九州大学 研究者情報
論文一覧
出射 浩(いでい ひろし) データ更新日:2021.10.07

教授 /  応用力学研究所 附属高温プラズマ理工学研究センター 大学院総合理工学府 総合理工学専攻 プラズマ・量子理工学


原著論文
1. A.Kuzmin;M.Kobayashi;K.Hanada;H.Idei;T.Onchi;S.Mori;N.Yoneda;T.Shikama;M.Hasuo;T.Ido;Y.Nagashima;R.Ikezoe;M.Hasegawa;K.Kuroda;K.Kono;S.Matsuo;T.Nagata;S.Shimabukuro;H.Zushi, Investigation of radial distribution of atomic hydrogen flux to the plasma facing components in steady state discharges in QUEST tokamak, Nuclear Materials and Energy, https://doi.org/10.1016/j.nme.2020.100872, 2021.03.
2. N. Yoneda, T. Shikama, K. Hanada, S. Mori, T. Onchi, K. Kuroda, M. Hasuo, A. Ejiri,K. Matsuzaki, Y. Osawa, Y. Peng, Y. Kawamata, S. Sakamoto, H. Idei, T. Ido, K. Nakamura,Y. Nagashima, R. Ikezoe, M. Hasegawa, A. Higashijima, T. Nagata, S. Shimabukuro , Toroidal Flow Measurements of Impurity Ions in QUEST ECH Plasmas using Multiple Viewing Chords Emission Spectroscopy , Nuclear Materials and Energy, https://doi.org/10.1016/j.nme.2021.100905, 2021.03.
3. Yifan Zhang, Takumi Onchi, Kazuo Nakamura, Akihiro Kidani, Qilin Yue, Kengoh Kuroda, Makoto Hasegawa, Ryuya Ikezoe, Hiroshi Idei, Designing an upgrade of ohmic heating system for the QUEST spherical tokamak, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2021.112362, 2021.03.
4. T. Onchi,, H. Idei, M. Fukuyama, D. Ogata, R. Ashida, T. Kariya, A. Ejiri, K. Matsuzaki, Y. Osawa, Y. Peng, S. Kojima, O. Watanabe, M. Hasegawa, K. Nakamura, K. Kuroda, R. Ikezoe, T. Ido, K. Hanada, N. Bertelli, M. Ono, and A. Fukuyama, Non-inductive plasma current ramp-up through oblique injection of harmonic electron cyclotron waves on the QUEST spherical tokamak, Physics of Plasma, https://doi.org/10.1063/5.0031357, 2021.01.
5. M. Ono, N. Bertelli, H. Idei, K. Hanada, T. Onchi, S. Kojima, and H. Elserafy, Modeling of solenoid-free start-up using 2nd harmonic electron cyclotron heating and current drive in QUEST, AIP Conference Proceedings , 10.1063/5.0013966, 2020.09.
6. Kojima S., Elserafy H., Hanada K., Idei H., Ikezoe R., Nagashima Y., Hasegawa M., Onchi T., Kuroda K., Nakamura K., Murakami T., Fukuyama M., Kato R., Yoneda R., Ono M., Ejiri A., Takase Y., Murakami S., Parametric Decay Wave Observation in HFS X-Mode Injection in QUEST, Plasma and Fusion Research, https://doi.org/10.1585/pfr.15.2402063, 2020.08.
7. Mori, S.; Shikama, T.; Hanada, K.; Yoneda, N.; Kuzmin, A.; Hasuo, M.; Idei, H.; Onchi, T.; Ejiri, A.; Osawa, Y.; Peng, Y.; Matsuzaki, K.; Kado, S.; Sawada, K.; Ido, T.; Nakamura, K.; Ikezoe, R.; Nagashima, Y.; Hasegawa, M.; Kuroda, K.; Higashijima, A.; Nagata, T.; Shimabukuro, S. Spectroscopic Measurement of Hydrogen Atom Density in a Plasma Produced with 28 GHz ECH in QUEST, Spectroscopic Measurement of Hydrogen Atom Density in a Plasma Produced with 28 GHz ECH in QUEST, Atoms, https://doi.org/10.3390/atoms8030044, 2020.08.
8. Makoto Hasegawa, Kazuaki Hanada, Hiroshi Idei, Shoji Kawasaki, Takahiro Nagata, Ryuya Ikezoe, Takumi Onchi, Kengoh Kuroda, Aki Higashijima, Predictive maintenance and safety operation by device integration on the QUEST large experimental device, Heliyon, 10.1016/j.heliyon.2020.e04214, 2020.06.
9. Qilin YUE, Kazuaki HANADA, Makoto OYA, Shogo MATSUO, Shinichiro KOJIMA, Hiroshi IDEI, Takumi ONCHI, Kengoh KURODA, Naoaki YOSHIDA, Ryuya IKEZOE, Yukai LIU, Makoto HASEGAWA, Shun SHIMABUKURO, Aki HIGASHIJIMA, Takahiro NAGATA and Shoji KAWASAKI , Measurement of Dynamic Retention with Fast Ejecting System of Targeted Sample (FESTA), Plasma and Fusion Research, 10.1585/pfr.15.2402013, 2020.04.
10. Elserafy,Hatem; Hanada, Kazuaki; Kojima, Shinichiro; Onchi, Takumi; Ikezoe, Ryuya; Kuroda, Kengoh; Idei, Hiroshi; Hasegawa, Makoto; Yoneda, Ryota; Fukuyama, Masaharu; Kuzmin, Arseniy; Higashijima, Aki; Nagata, Takahiro; Kawasaki, Shoji; Shimabukuro, Shun; Bertelli, Nicola; Ono, Masayuki, Electron Bernstein wave concversion of high-field side injected X-modes in QUEST, Plasma Physics and Controlled Fusion, 10.1088/1361-6587/ab6903, 2020.02.
11. Idei, Hiroshi; Onchi, Takumi; Mishra, Kishore; Zushi, Hideki; Kariya, Tsuyoshi; Imai, Tsuyoshi; Watanabe, Osamu; Ikezoe, Ryuya; Hanada, Kazuaki; Ono, Masayuki; ejiri, akira; Qian, Jinping; Nakamura, K; Fujisawa, Akihide; Nagashima, Yoshihiko; Hasegawa, Makoto; Matsuoka, Keisuke; Fukuyama, Atsushi; Kubo, Shin; Yoshikawa, M; Sakamoto, Mizuki; Kawasaki, Shoji; Higashijima, Aki; Ide, Shunsuke; Takase, Yuichi; Murakami, Sadayoshi, Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ab4c12, Volume 60, Number 1, 2019.12, A 28 GHz system with a high-power gyrotron tube has been used for the QUEST spherical tokamak to form an over-dense plasma for electron Bernstein wave (EBW) heating and current drive with an 8.2 GHz-wave. Non-inductive high-density plasma ramp-up experiments with dual-frequency (dual-f ) electron cyclotron (EC) (8.2 GHz and 28 GHz) waves were conducted. A spontaneous density jump (SDJ) to an over-dense state was first observed as a bifurcation phenomenon in the dual-f  wave experiment. The over-dense plasma on the 8.2 GHz wave was non-inductively ramped up to 25 kA, and was maintained for 0.4 s under stable plasma equilibrium after two such jumps in one shot. Heating to mildly energetic electrons and bulk electrons was observed even in the over-dense region. The electrostatic EBW heating effect on the mildly energetic electrons in the over-dense region is assessed following a dispersion analysis of the 8.2 GHz wave. The bulk electron heating effect observed is explained as heat exchange from mildly energetic electrons heated by the electrostatic EBW. Remarkably, a high hard-x-ray-radiation temperature of  ~500 keV was also observed in tangential viewing for current-carrying electrons in the over-dense core region. Synergetic heating from the overlap of different 28 GHz EC harmonic resonances as well as higher harmonic heating is discussed for maintaining the highly energetic electrons in the over-dense core region. In addition, the SDJ process and mechanism are considered based on the discussion of the electron heating effects with the 8.2 GHz wave..
12. Takumi Onchi, Hiroshi Idei, K. Nakamura, T. Nagata, S. Kawasaki, R. Ashida, M. Fukuyama, Makoto Hasegawa, Ryuya Ikezoe, A. Higashijima, K. Kuroda, Yoshihiko Nagashima, Kazuaki Hanada, High voltage electrical system of 8.56 GHz CW klystron for electron cyclotron heating on QUEST spherical tokamak, Fusion Engineering and Design, 10.1016/j.fusengdes.2019.04.043, 146, 2567-2570, 2019.09, [URL], A high voltage DC power supply for the cathode of the 8.56 GHz CW klystron has been set up for electron cyclotron heating (ECH) in steady state tokamak operation on QUEST spherical tokamak. The power supply is equipped with an IGBT array and a reactor for fast shutoff of the voltage in 10 μs, where the influx of electric energy at the short circuit is limited to 5 J. AC switches also have been installed in the three-phase power lines. High voltage relays are useful to save electric energy consumption. Fast three-phase AC switching by IGBT-stack is applicable to reduce the electric load of the components of the klystron power supply..
13. K. Nakamura, M. M. Alam, Y. Z. Jiang, O. Mitarai, M. Takechi, M. Hasegawa, K. Tokunaga, K. Hanada, H. Idei, Y. Nagashima, T. Onchi, K. Kuroda, O. Watanabe, A. Higashijima, T. Nagata, S. Shimabukuro, S. Kawasaki, A. Fukuyama, Plasma equilibrium based on EC-driven current profile with toroidal rotation on QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2019.04.059, 146, 2628-2631, 2019.09, [URL], In the EC-driven (8.2 GHz) steady-state plasma on QUEST, plasma current seems to flow in the open magnetic surface in the outside of the closed magnetic surface in the low-field region according to plasma current fitting method without taking equilibrium into account. In our previous work, plasma equilibrium solution was fitted assuming all plasma current is flowing in the inside of the Last Closed Flux Surface (LCFS). It was solved within isotropic pressure profile by EFIT code. Opposite-polarity current density region appeared in the high-field region. Here in this article, considering the toroidal rotation, the equilibrium is fitted within nested magnetic surfaces by SU-EFIT. Though the plasma magnetic axis shifts outward due to the centrifugal force, the opposite polarity current does not disappear in the high-field region. And relation between the toroidal rotation speed and the poloidal beta value will be discussed..
14. M. Fukuyama, Hiroshi Idei, T. I. Tsujimura, S. Kubo, S. Kobayashi, M. Yunoki, Takumi Onchi, Ryuya Ikezoe, Quasi-optical polarizer system for ECHCD experiments in the QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2019.02.099, 146, 1437-1440, 2019.09, [URL], A new transmission line from 28 GHz gyrotron to QUEST spherical tokamak (ST) has been developed for the highly efficient electron cyclotron heating and current drive (ECHCD) experiments. The ECHCD effect depends on the incident mode or polarization states of the injected beam. Although two corrugated-polarizer miter bends were developed and assembled to transmission line in the QUEST, arcing events were frequently detected at the polarizer miter bend when the high-power millimeter-wave were transmitted. A new quasi-optical (QO) concept for the polarizer system composed of two corrugated plate and a QO mirror was proposed to avoid the arcing at polarizer. The QO mirror was designed for coupling of input and output HE11 modes at the polarizer, its coupling property is discussed with Kirchhoff integral. Polarization-setting performance of the developed QO polarizer was examined in a low-power test system, and is discussed with grating-polarizer calculation..
15. Miu YUNOKI. Hiroshi IDEi, Kazuo NAKAMURA, Masaharu FUKUYAMA, Ryuichi ASHIDA. Daichi OGATA, Takumi ONCHI. Ryuya IKEZOE, Masayuki YOSHIKAWA, Prototype Quasi-optical Launcher System of 4mm Round-trip Interferometer for the QUEST Spherical Tokamak Experiments, Plasma and Fusion Research, DOI: 10.1585/pfr.14.3402122 , Volume 14, 3402122, 2019.07.
16. Masaharu FUKUYAMA, Hiroshi IDEI, Miu YUNOKI, Ryuichi ASHIDA, Daichi OGATA,Ryuya IKEZOE and Takumi ONCHI, Prototype Phased-Array Patch Loop Antennae for Electron Cyclotron Emission Diagnostics, Plasma and Fusion Research, 10.1585/pfr.14.3402111, Volume 14, 3402111 (2019), 2019.06.
17. C. Huang, K. Hanada, K. Kuroda, S. Kojima, H. Fujiyoshi, H. Miura, T. Yamada, H. Idei, M. Hasegawa, and T. Onchi, Fast tangentially viewed soft X-ray imaging system based on image intensifier with microchannel plate detector on QUEST, Plasma and Fusion Research, DOI: 10.1585/pfr.14.1402128, Volume 14, 1402128 , 2019.06.
18. K. HANADA, N. YOSHIDA, M. HASEGAWA, H. IDEI, Y. NAGASHIMA, K. NAKAMURA, T. ONCHI, O. WATANABE, H. WATANABE, K. TOKUNAGA, A. HIGASHIJIMA, S. KAWASAKI, H. NAKASHIMA, T. NAGATA, S. SHIMABUKURO, A. HATAYAMA, K. OKAMOTO, I. TAKAGI, T. HIRATA, T. SHIKAMA, S. MURAKAMI, H. LONG, Z. X. WANG, Y. OYA, S. KOJIMA, K. GAKU, M. OYA, M. MIYAMOTO, Y. OYA, A. KUZUMIN, T. TAKASE, X. GAO, H. LIU, J. QIAN, R. RAMAN, M. ONO, , Particle balance investigation with the combination of the hydrogen barrier model and rate equations of hydrogen state in long duration discharges on an all-metal plasma facing wall in QUEST, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ab1858, Volume 59, Number 7 , 2019.05.
19. Kazuaki Hanada, N. Yoshida, I. Takagi, T. Hirata, A. Hatayama, K. Okamoto, Y. Oya, T. Shikama, Z. Wang, H. Long, C. Huang, M. Oya, Hiroshi Idei, Yoshihiko Nagashima, Takumi Onchi, Makoto Hasegawa, K. Nakamura, H. Zushi, K. Kuroda, S. Kawasaki, A. Higashijima, T. Nagata, S. Shimabukuro, Y. Takase, S. Murakami, X. Gao, H. Liu, J. Qian, R. Raman, M. Ono, Estimation of fuel particle balance in steady state operation with hydrogen barrier model, Nuclear Materials and Energy, 10.1016/j.nme.2019.03.015, 19, 544-549, 2019.05, [URL], This research investigated fuel particle balance during long duration discharge in an all-metal plasma facing wall (PFW)through intensive QUEST execution. A simple wall model including the plasma-induced deposition layer that creates hydrogen (H)barriers, called the H barrier model, was established. A simple calculation, based on a combination of H state rate equations and the H barrier model, was applied to real plasma in the early phase of its longest discharge. The model accurately reconstructed the evolutions of electron density and wall-stored H over time, proper values are chosen for the parameters that are difficult to determine experimentally. Comparative calculations that used the H barrier and a fully reflective models, predicted significant impacts of wall models on the plasma density time response and value of electron density, indicating that a proper wall model should be developed for all-metal PFW devices..
20. Takumi Onchi, Hiroshi Idei, K. Nakamura, T. Nagata, S. Kawasaki, R. Ashida, M. Fukuyama, M. Hasegawa, Ryuya Ikezoe, A. Higashijima, K. Kuroda, Y. Nagashima, K. Hanada , High voltage electrical system of 8.56 GHz CW klystron for electron cyclotron heating on QUEST spherical tokamak, Fusion Engineering and Design
, https://doi.org/10.1016/j.fusengdes.2019.04.043, 2019.04.
21. T. Kariya, R. Minami, T. Imai, M. Okada, F. Motoyoshi, T. Numakura, Y. Nakashima, Hiroshi Idei, Takumi Onchi, Kazuaki Hanada, T. Shimozuma, Y. Yoshimura, H. Takahashi, S. Kubo, Y. Oda, R. Ikeda, K. Sakamoto, M. Ono, K. Nagasaki, T. Eguchi, Y. Mitsunaka, Development of high power gyrotrons for advanced fusion devices, Nuclear Fusion, 10.1088/1741-4326/ab0e2c, 59, 6, 2019.04, [URL], Megawatt (MW) gyrotrons, with a wide frequency range from 14 to 300 GHz, are being developed as part of a collaborative electron cyclotron heating (ECH) study for advanced fusion devices and a demonstration power plant (DEMO). (1) Detailed designs for a 14 GHz 1 MW gyrotron are being developed for fabrication. For a 14 GHz radio frequency (RF) beam with high divergence, a calculated transmission efficiency of 94% to the corrugated waveguide coupling position was obtained initially by introducing the design concept (direct RF beam coupling by built-in waveguide) to minimize the RF transmission path. Installing a double-disk sapphire window will make it possible to develop a 1 MW gyrotron with a continuous wave (CW) at 14 GHz. (2) In experimental tests of a new 28/35 GHz dual-frequency gyrotron, the cooling characteristics of an optimal-structure double-disk sapphire window were evaluated. We confirmed that operating at 0.4 MW with a CW at 28 GHz is feasible, reaching twice the output power reported in previous studies. In a 2 ms short-pulse experimental test, maximum powers of 1.65 MW at 28.04 GHz and 1.21 MW at 34.83 GHz were achieved. (3) A design study of a 77/51 GHz dual-frequency gyrotron was performed. Oscillations above 1.5 MW for 77 GHz and 1.3 MW for 51.88 GHz are expected for a beam voltage V k = 80 kV and beam current I k = 60 A. (4) In an experiment with a 300 GHz gyrotron, the influence of the wave reflected from the window was reduced by tilting the output window, and mode competition in the cavity was suppressed. An output power of 0.62 MW with a pulse width of 1 ms, which is the new record for this frequency, was obtained. (5) We also performed a trial design study of a 240 GHz gyrotron for DEMO..
22. Kariya, Tsuyoshi; Minami, Ryutaro; Imai, Tsuyoshi; Okada, Maki; Motoyoshi, Fumiya; Numakura, Tomoharu; Nakashima, Yousuke; Idei, Hiroshi; Onchi, Takumi; Hanada, Kazuaki; Shimozuma, T; Yoshimura, Yasuo; Takahashi, Hiromi; Kubo, Shin; Oda, Yasuhisa; Ikeda, Ryosuke; Sakamoto, Keishi; Ono, Masayuki; Nagasaki, Kazunobu; Eguchi, Taku; Mitsunaka, Yoshika, Development of High Power Gyrotrons for Advanced Fusion Devices, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ab0e2c, 2019.03.
23. Hatem ELSERAFY, Kazuaki HANADA, Kengoh KURODA, Hiroshi IDEI, Ryota YONEDA, Canbin HUANG, Shinichiro KOJIMA, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Takumi ONCHI, Ryuya IKEZOE, Aki HIGASHIJIMA, Takahiro NAGATA, Shoji KAWASAKI, Shun SHIMABUKURO, Nicola BERTELLI and Masayuki ONO, HFS Injection of X-Mode for EBW Conversion in QUEST, Plasma and Fusion Research, DOI: 10.1585/pfr.14.1205038, 2019.03.
24. H. Idei, T. Onchi, T. Kariya, T.I. Tsujimura, S. Kubo, S. Kobayashi, M. Sakaguchi, T. Imai, M. Hasegawa, K. Nakamura, K. Mishra, M. Fukuyama, M. Yunoki, S. Kojima, O. Watanabe, K. Kuroda, K. Hanada, Y. Nagashima, A. Ejiri, N. Matsumoto, M. Ono, A. Higashijima, T. Nagata, S. Shimabukoro, Y. Takase, A. Fukuyama, S. Murakami, 28-GHz ECHCD system with beam focusing launcher on the QUEST spherical tokamak, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2019.02.027, 2019.02, New polarizer and launcher systems on a 28-GHz electron-cyclotron (EC) heating and current drive (HCD) system have been developed for non-inductive second-harmonic EC-plasma-current ramp-up in the QUEST spherical tokamak. A launcher system with two quasi-optical mirrors providing beam steering capability was designed to focus the incident beam to a small-sized waist of ∼0.05 m at the second-harmonic EC resonance layer. A relatively large focusing mirror was designed based on a Kirchhoff integral code developed to derive wave solutions. The focusing property of the launched beam was first confirmed with a 3-dimensional (3D) electromagnetic-wave simulator. Focusing characteristics were also checked at low-power test facilities, together with the steering capability. The performance of this launcher system was demonstrated to work as designed, and assembled in the QUEST device. The system was applied to the non-inductive second-harmonic EC plasma ramp-up experiments with no optimization required regarding the incident polarization. The results obtained for the non-inductive plasma ramp-up are also presented..
25. M. Fukuyama, H. Idei, T.I. Tsujimura, S. Kubo, S. Kobayashi, M. Yunoki, T. Onchi, R. Ikezoe, Quasi-optical Polarizer System for ECHCD Experiments in the QUEST, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2019.02.099, 2019.02.
26. Hiroshi Idei, Takumi Onchi, T. Kariya, T. I. Tsujimura, S. Kubo, S. Kobayashi, M. Sakaguchi, T. Imai, Makoto Hasegawa, K. Nakamura, K. Mishra, M. Fukuyama, M. Yunoki, S. Kojima, O. Watanabe, K. Kuroda, Kazuaki Hanada, Yoshihiko Nagashima, A. Ejiri, N. Matsumoto, M. Ono, A. Higashijima, T. Nagata, S. Shimabukoro, Y. Takase, A. Fukuyama, S. Murakami, 28-GHz ECHCD system with beam focusing launcher on the QUEST spherical tokamak, Fusion Engineering and Design, 10.1016/j.fusengdes.2019.02.027, 2019.01, [URL], New polarizer and launcher systems on a 28-GHz electron-cyclotron (EC) heating and current drive (HCD) system have been developed for non-inductive second-harmonic EC-plasma-current ramp-up in the QUEST spherical tokamak. A launcher system with two quasi-optical mirrors providing beam steering capability was designed to focus the incident beam to a small-sized waist of ∼0.05 m at the second-harmonic EC resonance layer. A relatively large focusing mirror was designed based on a Kirchhoff integral code developed to derive wave solutions. The focusing property of the launched beam was first confirmed with a 3-dimensional (3D) electromagnetic-wave simulator. Focusing characteristics were also checked at low-power test facilities, together with the steering capability. The performance of this launcher system was demonstrated to work as designed, and assembled in the QUEST device. The system was applied to the non-inductive second-harmonic EC plasma ramp-up experiments with no optimization required regarding the incident polarization. The results obtained for the non-inductive plasma ramp-up are also presented..
27. Hatem Elserafy, Kazuaki Hanada, Kengoh Kuroda, Hiroshi Idei, Ryota Yoneda, Canbin Huang, Shinichiro Kojima, Makoto Hasegawa, Yoshihiko Nagashima, Takumi Onchi, Ryuya Ikezoe, Aki Higashijima, Takahiro Nagata, Shoji Kawasaki, Shun Shimabukuro, Nicola Bertelli, Masayuki Ono, HFS injection of X-mode for EBW conversion in QUEST, Plasma and Fusion Research, 10.1585/pfr.14.1205038, 14, 1, 2019.01, [URL], High field side (HFS) injection of eXtra-ordinary X-mode for electron Bernstein wave (EBW) conversion was conducted in the QUEST tokamak. Radio frequency (RF; 8.2 GHz) power was delivered from the low field side (LFS) to the high field side HFS through waveguides, and from the HFS placed 20 cm above the midplane of the vacuum vessel. The aim was to compare the RF launches from the LFS and HFS. The plasma brightness, measured by a fast camera, as well as the H α signal captured along the mid-plane, was noticeably higher in the HFS launch than in the LFS launch. The HFS injection achieved a plasma current of approximately 130 A, versus 35A in the LFS injection. The electron density n e predicted from the position of the upper hybrid resonance agreed with the line-averaged n e measured by an interferometer, confirming the effective conversion and subsequent damping of the EBW mode. The RF leakage of the HFS injection was less than one-sixth that of the LFS injection. These results indicate that HFS delivers better RF coupling and conversion efficiency to EBW than LFS injection. Such efficient plasma heating via EBW will significantly enhance the plasma production..
28. Masaharu Fukuyama, Hiroshi Idei, Miu Yunoki, Ryuichi Ashida, Daichi Ogata, Ryuya Ikezoe, Takumi Onchi, Prototype phased-array patch loop antennae for electron cyclotron emission diagnostics, Plasma and Fusion Research, 10.1585/PFR.14.3402111, 14, 2019.01, [URL], A two-dimensional (2D) phased-array-antenna (PAA) for electron cyclotron emission is one of the diagnostics for finding the window area of mode conversion from electron cyclotron waves to electron Bernstein wave. Spatial resolution of the reconstructed emission field pattern is improved with a lot of the antenna elements. The study proposes a phased-array patch loop antenna (PAPA) as a promising system to increase the elements of PAA. A 2D image reconstruction of a 6 GHz radio frequency source emission shows that the source position is detected within millimeter range by applying the prototype PAPA. This result indicates that the 2D image reconstruction with multi-element PAPA is feasible..
29. S. Kubo, H. Idei, Y. Tatematsu, T. Saito, M. Iizawa, Electron Bernstein wave detection by sub-Tera-Hz scattering in the QUEST, 43rd International Conference on Infrared Millimeter and Terahertz Waves, IRMMW-THz 2018
2018 43rd International Conference on Infrared Millimeter and Terahertz Waves, IRMMW-THz 2018
, 10.1109/IRMMW-THz.2018.8510425, 2018.10, [URL], A collective scattering method using the sub-THz gyrotron radiation is planned to apply to the direct detection of the electron Bernstein wave in the QUEST where the electron Bernstein wave plays one of the main heating/current drive roles in sustaining steady state spherical tokamak configuration..
30. K. Kuroda, R. Raman, K. Hanada, M. Hasegawa, T. Onchi, M. Ono, B. A. Nelson, T. R. Jarboe, M. Nagata, O. Mitarai, K. Nakamura, H. Idei, J. Rogers, S. Kawasaki, T. Nagata, A. Kuzmin, S. Kojima, C. Huang, O. Watanabe, A. Higashijima, Y. Takase, A. Fukuyama, S. Murakami, Initial results from solenoid-free plasma start-up using Transient CHI on QUEST, Plasma Physics and Controlled Fusion, 10.1088/1361-6587/aadcb7, 60, 11, 2018.09, [URL], Initial results from the recently implemented transient coaxial helicity injection (CHI) system on QUEST are reported. QUEST uses a new CHI electrode configuration in which the CHI insulator is not part of the vacuum boundary, making this configuration easier to implement in fusion reactors. Experimental results show that transient CHI startup in this alternate electrode configuration is indeed possible. Reliable gas breakdown was achieved, and toroidal currents up to 45 kA were generated..
31. Santanu Banerjee, H. Zushi, N. Nishino, K. Hanada, H. Idei, K. Nakamura, M. Hasegawa, A. Fujisawa, Y. Nagashima, K. Mishra, S. Tashima, T. Onchi, A. Kuzmin, K. Matsuoka, Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST, Plasma Physics and Controlled Fusion, 10.1088/1361-6587/aacb69, 60, 8, 2018.06, [URL], Intensity fluctuations are investigated using the fast camera imaging technique in the slab annular plasma as a function of magnetic shear and connection length in the spherical tokamak QUEST. Note that here QUEST is operated as a simple magnetized torus with a tight aspect ratio. Slab annular plasmas feature open magnetic field lines and can mimic the tokamak edge-scrape off layer (SOL)-like plasma attributes reasonably well. Three magnetic shear regimes are realized using three poloidal magnetic field (PF) coil pairs. A whole range of connection lengths (∼∞ ≥ L c ≥ 5.5 m) is scanned by varying the PF strength for a given toroidal field for each magnetic shear regime. For the first time a systematic study of the effect of magnetic shear and field line pitch together on edge-SOL-like plasma fluctuations is being reported. Slab plasmas with intermediate magnetic shear are observed to be more susceptible to generate distinct blobs when L c is reduced by increasing the PF strength. A distinct coherent mode appears only at the lowest magnetic shear slab featuring a deep potential well. Such mode is not apparent at other magnetic shear cases even at the same L c. Finally, with a combination of PF coil pairs, both the features of intermediate and low magnetic shear slabs are shown to be realizable simultaneously. Significantly stronger blobs are observed with such combination of PF mirror ratios in the presence of a coherent mode. This study may provide better insight into the effect of magnetic configuration in the tokamak edge and SOL turbulence and can help in searching for better tools to control cross-field convective intermittent transport in tokamaks..
32. Makoto Hasegawa, Kazuo Nakamura, Kazuaki Hanada, Shoji Kawasaki, Arseniy Kuzmin, Hiroshi Idei, Kazutoshi Tokunaga, Yoshihiko Nagashima, Takumi Onchi, Kengoh Kuroda, Osamu Watanabe, Aki Higashijima, Takahiro Nagata, Modification of plasma control system and hot-wall temperature control system for long-duration plasma sustainment in QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2018.02.069, 129, 202-206, 2018.04, [URL], In tokamaks, the temperature of the plasma-facing wall is an important parameter for achieving particle balance and therefore steady-state operation. QUEST, which is a middle-sized spherical tokamak, has hot walls that act as plasma-facing walls. They can be actively heated with sheath heaters and actively cooled with water. To control the wall temperature, heating and cooling systems have been developed. These systems adjust the power of the sheath heaters and the motor valves of the cooling system, respectively. The two systems communicate via Ethernet through UDP and control the hot-wall temperature cooperatively. The plasma control system (PCS) in QUEST has also been modified, especially with respect to gas fueling, in order to enable long-duration plasma sustainment. A feedback controller has been installed in the PCS, together with a mass flow controller, allowing Hα emission from the plasma which is used as a reference signal, to be well controlled. Plasma density calculations using a field-programmable gate array are proposed for the feedback control system..
33. Makoto Hasegawa, Kazuo Nakamura, Kazuaki Hanada, Shoji Kawasaki, Arseniy Kuzmin, Hiroshi Idei, Kazutoshi Tokunaga, Yoshihiko Nagashima, Takumi Onchi, Kengoh Kuroda, Osamu Watanabe, Aki Higashijima, Takahiro Nagata, Modification of plasma control system and hot-wall temperature control system for long-duration plasma sustainment in QUEST, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2018.02.069, 2018.03.
34. Nao Yoneda, Taiichi Shikama, Hideki Zushi, Kazuaki Hanada, Akinobu Fujikawa, Takumi Onchi, Kengoh Kuroda, Kuniaki Nii, Masahiro Hasuo, Makoto Hasegawa, Hiroshi Idei, Kazuo Nakamura, Yoshihiko Nagashima, Aki Higashijima, Takahiro Nagata, Spectroscopic measurements of impurity ion toroidal and poloidal flow velocities and their dependence on vertical magnetic field in QUEST toroidal ECR plasmas, Plasma and Fusion Research, 10.1585/PFR.13.3402087, 13, 2018.01, [URL], Toroidal electron cyclotron resonance (ECR) plasma is an ECR heated plasma in an open toroidal magnetic field. The plasma contains no toroidal current and is used for the pre-ionization and non-inductive startup of a tokamak plasma. To obtain a deeper understanding of the basic properties of the plasmas produced in the spherical tokamak QUEST (Q-shu University Experiment with steady-state Spherical Tokamak), we have developed an optical emission spectroscopy system with multiple viewing chords and have used it to measure the spatial distributions of the toroidal and poloidal flow velocities of C2+ ions. We compare the measured velocities with those calculated from the ion drift equations using the plasma parameters reported for a similar spherical tokamak, LATE (the Low Aspect Ratio Torus Experiment)..
35. K. Nakamura, M. M. Alam, Y. Z. Jiang, O. Mitarai, K. Kurihara, Y. Kawamata, M. Sueoka, M. Takechi, Makoto Hasegawa, K. Tokunaga, K. Araki, H. Zushi, Kazuaki Hanada, akihide fujisawa, Hiroshi Idei, Yoshihiko Nagashima, S. Kawasaki, H. Nakashima, A. Higashijima, T. Nagata, A. Fukuyama, Plasma equilibrium based on RF-driven current profile without assuming nested magnetic surfaces on QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2017.05.070, 123, 532-534, 2017.11, [URL], In the present RF-driven (ECCD) steady-state plasma on QUEST, the plasma current seems to flow in the open magnetic surface outside of the closed magnetic surface in the low-field region according to the plasma current fitting (PCF) method. The current in the open magnetic surface is due to the orbit-driven current by high-energy particles in the RF-driven plasma. High-energy particles guiding center orbits are calculated as contour plots of conserved variables in the Hamiltonian formulation considering particles in the initial position with different energies and pitch angles satisfying the resonance condition. A negative current appears near the magnetic axis, and a hollow current profile is expected even if the pressure driven current is considered. The equilibrium is fitted within nested magnetic surfaces by J-EFIT coded by MATLAB using the hollow current profile shift toward the low-field region. Although the plasma boundary shape reflects the plasma current density profile, the equilibrium shape fitted by J-EFIT does not coincide with the orbit-driven current profile. However, introducing an extension of the current profile without assuming nested contours into the J-EFIT code appropriately fits the plasma shape with the hollow current profile to the measured magnetic data..
36. Hiroshi Idei, T. Kariya, T. Imai, K. Mishra, Takumi Onchi, O. Watanabe, H. Zushi, Kazuaki Hanada, J. Qian, A. Ejiri, M. M. Alam, K. Nakamura, akihide fujisawa, Yoshihiko Nagashima, Makoto Hasegawa, K. Matsuoka, A. Fukuyama, S. Kubo, T. Shimozuma, M. Yoshikawa, M. Sakamoto, S. Kawasaki, H. Nakashima, A. Higashijima, S. Ide, T. Maekawa, Y. Takase, K. Toi, Fully non-inductive second harmonic electron cyclotron plasma ramp-up in the QUEST spherical tokamak, Nuclear Fusion, 10.1088/1741-4326/aa7c20, 57, 12, 2017.10, [URL], Fully non-inductive second (2nd) harmonic electron cyclotron (EC) plasma current ramp-up was demonstrated with a newlly developed 28 GHz system in the QUEST spherical tokamak. A high plasma current of 54 kA was non-inductively ramped up and sustained stably for 0.9 s with a 270 kW 28 GHz wave. A higher plasma current of 66 kA was also non-inductively achieved with a slow ramp-up of the vertical field. We have achieved a significantly higher plasma current than those achieved previously with the 2nd harmonic EC waves. This fully non-inductive 2nd harmonic EC plasma ramp-up method might be useful for future burning plasma devices and fusion reactors, in particular for operations at half magnetic field with the same EC heating equipment..
37. K. Hanada, N. Yoshida, T. Honda, Z. Wang, A. Kuzmin, I. Takagi, T. Hirata, Y. Oya, M. Miyamoto, H. Zushi, M. Hasegawa, K. Nakamura, A. Fujisawa, H. Idei, Y. Nagashima, O. Watanabe, T. Onchi, K. Kuroda, H. Long, H. Watanabe, K. Tokunaga, A. Higashijima, S. Kawasaki, T. Nagata, Y. Takase, A. Fukuyama, O. Mitarai, Investigation of hydrogen recycling in long-duration discharges and its modification with a hot wall in the spherical tokamak QUEST, Nuclear Fusion, 10.1088/1741-4326/aa8121, 57, 12, 2017.10, [URL], Fully non-inductive plasma maintenance was achieved by a microwave of 8.2 GHz and 40 kW for more than 1 h 55 min with a well-controlled plasma-facing wall (PFW) temperature of 393 K, using a hot wall in the middle-sized spherical tokamak QUEST, until the discharge was finally terminated by the uncontrollability of the density. The PFW was composed of atmospheric plasma-sprayed tungsten and stainless steel. The hot wall plays an essential role in reducing the amount of wall-stored hydrogen and facilitates hydrogen recycling. The behaviour of fuel hydrogen in the PFW was investigated by monitoring the injection and evacuation of hydrogen into and from the plasma-producing vessel. A fuel particle balance equation based on the presence of a hydrogen transport barrier between the deposited layer and the substrate was applied to the long-duration discharges. It was found that the model could readily predict the observed behaviour in which a higher wall temperature likely gives rise to faster wall saturation..
38. Z. Wang, Kazuaki Hanada, N. Yoshida, T. Shimoji, M. Miyamoto, Y. Oya, H. Zushi, Hiroshi Idei, K. Nakamura, akihide fujisawa, Yoshihiko Nagashima, Makoto Hasegawa, S. Kawasaki, A. Higashijima, H. Nakashima, T. Nagata, A. Kawaguchi, T. Fujiwara, K. Araki, O. Mitarai, A. Fukuyama, Y. Takase, K. Matsumoto, Measurement of thickness of film deposited on the plasma-facing wall in the QUEST tokamak by colorimetry, Review of Scientific Instruments, 10.1063/1.5000739, 88, 9, 2017.09, [URL], After several experimental campaigns in the Kyushu University Experiment with Steady-state Spherical Tokamak (QUEST), the originally stainless steel plasma-facing wall (PFW) becomes completely covered with a deposited film composed of mixture materials, such as iron, chromium, carbon, and tungsten. In this work, an innovative colorimetry-based method was developed to measure the thickness of the deposited film on the actual QUEST wall. Because the optical constants of the deposited film on the PFW were position-dependent and the extinction coefficient k1 was about 1.0-2.0, which made the probing light not penetrate through some thick deposited films, the colorimetry method developed can only provide a rough value range of thickness of the metal-containing film deposited on the actual PFW in QUEST. However, the use of colorimetry is of great benefit to large-area inspections and to radioactive materials in future fusion devices that will be strictly prohibited from being taken out of the limited area..
39. A. Kuzmin, H. Zushi, I. Takagi, S. K. Sharma, M. Kobayashi, Y. Hirooka, Takumi Onchi, Kazuaki Hanada, N. Yoshida, K. Nakamura, akihide fujisawa, Hiroshi Idei, Yoshihiko Nagashima, Makoto Hasegawa, T. Mutoh, K. Mishra, H. Ohwada, Spatial distribution of atomic and ion hydrogen flux and its effect on hydrogen recycling in long duration confined and non-confined plasmas, Nuclear Materials and Energy, 10.1016/j.nme.2017.03.027, 12, 627-632, 2017.08, [URL], In order to understand the atomic hydrogen distribution in different kinds of plasma and its influence on the recycling, two kinds of plasmas were used: non-confined annular electron cyclotron resonance (ECR) and confined long duration plasmas. The permeation probes are used to measure directly the atomic hydrogen flux at several poloidal positions. The permeation through metals due to the ion and atom component of the hydrogen flux to the wall is indistinguishable. To estimate the contribution of the ions directly, Langmuir probes were used. The Гinc profile behind the plasma facing components (PFCs) is almost constant, ∼2 ×1018 H/s/m2..
40. R. Yoneda, Kazuaki Hanada, K. Nakamura, Hiroshi Idei, N. Yoshida, Makoto Hasegawa, Takumi Onchi, K. Kuroda, S. Kawasaki, A. Higashijima, T. Nagata, A. Isayama, O. Mitarai, A. Fukuyama, Y. Takase, Effect of magnetic structure on RF-induced breakdown in QUEST, Physics of Plasmas, 10.1063/1.4985142, 24, 6, 2017.06, [URL], In tokamak operations, breakdown of plasma is the first step of the plasma build-up. In this paper, we present a combinative investigation of radio frequency (RF)-induced breakdown experiments in QUEST (Q-shu University Experiment with Steady-State Spherical Tokamak) and a one-point model of hydrogen ionization. Experimental results with two different frequencies of 2.45 GHz and 8.2 GHz showed that the clear threshold on connection length, L, existed for breakdown with a negative n-index configuration n=-(R/Bv)·(∂Bv/∂R), where R is the major radius and Bv the is vertical magnetic field. In contrast, breakdown was always obtained with positive n-index when changing L. It indicates that a lifetime of an incubated electron plays a significant role in the plasma breakdown. According to one-point model calculation, the experimental threshold of L is well predicted by the lifetime of the incubated electron estimated by employing the loss term along with L. The model calculation also describes the requirement of the minimum electron temperature Te for RF-induced breakdown to realize an avalanche of electrons in the tokamak magnetic structure..
41. Y. Takase, A. Ejiri, T. Fujita, N. Fukumoto, A. Fukuyama, Kazuaki Hanada, Hiroshi Idei, M. Nagata, Y. Ono, H. Tanaka, M. Uchida, R. Horiuchi, Y. Kamada, H. Kasahara, S. Masuzaki, Y. Nagayama, T. Oishi, K. Saito, Y. Takeiri, S. Tsuji-Iio, Overview of spherical tokamak research in Japan, Nuclear Fusion, 10.1088/1741-4326/aa62c1, 57, 10, 2017.06, [URL], Nationally coordinated research on spherical tokamak is being conducted in Japan. Recent achievements include: (i) plasma current start-up and ramp-up without the use of the central solenoid by RF waves (in electron cyclotron and lower hybrid frequency ranges), (ii) plasma current start-up by AC Ohmic operation and by coaxial helicity injection, (iii) development of an advanced fuelling technique by compact toroid injection, (iv) ultra-long-pulse operation and particle control using a high temperature metal wall, (v) access to the ultra-high-β regime by high-power reconnection heating, and (vi) improvement of spherical tokamak plasma stability by externally applied helical field..
42. T. Kariya, T. Imai, R. Minami, K. Sakamoto, Y. Oda, R. Ikeda, T. Shimozuma, S. Kubo, Hiroshi Idei, T. Numakura, K. Tsumura, Y. Ebashi, M. Okada, Y. Nakashima, Y. Yoshimura, H. Takahashi, S. Ito, Kazuaki Hanada, K. Nagasaki, M. Ono, T. Eguchi, Y. Mitsunaka, Development of over-MW gyrotrons for fusion at 14 GHz to sub-THz frequencies, Nuclear Fusion, 10.1088/1741-4326/aa6875, 57, 6, 2017.04, [URL], Megawatt power gyrotrons are being developed for collaborative electron cyclotron heating (ECH) studies of advanced fusion devices and demonstration power plant (DEMO). (1) In the first experiment of a 300 GHz gyrotron, an output power above 0.5 MW in the TE32,18 single mode was achieved with a pulse width of 2 ms. This was the first observation of MW-scale oscillations in a DEMO-relevant gyrotron mode. It was also found that the reflection at the output window affected the determination of the oscillation mode. Furthermore, several single mode oscillations in the 226-254 GHz range were confirmed, which is important for the step-frequency tunable gyrotron in the sub-THz frequency range. (2) Based on the successful results of the 77 and 154 GHz large helical device (LHD) tubes, a new 154/116 GHz dual-frequency gyrotron with an output of over 1.5 MW is being designed. (3) A new record output of 1.38 MW was obtained using an existing 28 GHz gyrotron. A newly designed tube aimed at achieving a dual-frequency output power of 2 MW at 28 GHz (0.4 MW continuous wave) and 1 MW at 35 GHz was built. In the first experimental test, main mode oscillations were observed at the frequencies of 28.036 and 34.831 GHz with Gaussian-like output beams and output power of 1.27 and 0.48 MW, respectively. A total efficiency of 50% was achieved at 28 GHz operation..
43. Toru Ii Tsujimura, Hiroshi Idei, Shin Kubo, Sakuji Kobayashi, Optimized design of polarizers with low ohmic loss and any polarization state for the 28 GHz QUEST ECH/ECCD system, Fusion Engineering and Design, 10.1016/j.fusengdes.2016.11.019, 114, 97-101, 2017.01, [URL], In a high-power long-pulse millimeter-wave transmission line for electron cyclotron heating and current drive (ECH/ECCD), the ohmic loss on the grooved mirror surface of polarizers is one of the important issues for reducing the transmission loss. In this paper, the ohmic loss on the mirror surface is evaluated in simulated real-scale polarizer miter bends for different groove parameters under a linearly-polarized incident wave excitation. The polarizers with low ohmic loss are optimally designed for a new 28 GHz transmission line on the QUEST spherical tokamak. The calculated optimum ohmic loss is restricted to only less than 1.5 times as large as the theoretical loss for a copper flat mirror at room temperature. The copper rounded-rectangular grooves of the polarizers were relatively easy to make smooth in mechanical machining and the resultant surface roughness was not more than 0.15 μm, which is only 0.38 times as large as the skin depth. The combination of the designed elliptical polarizer and the polarization rotator can also realize any polarization state of the reflected wave..
44. Kengoh Kuroda, Roger Raman, Kazuaki Hanada, Makoto Hasegawa, Takumi Onchi, Masayuki Ono, Thomas Jaboe, Brian A. Nelson, Masayoshi Nagata, Osamu Mitarai, Kazuo Nakamura, Hiroshi Idei, John Rogers, Shoji Kawasaki, Takahiro Nagata, Arseniy Kuzmin, Shinichiro Kojima, Osamu Watanabe, Aki Higashijima, Yuichi Takase, Atsushi Fukuyama, Current start-up using the new CHI system, Plasma and Fusion Research, 10.1585/pfr.12.1202020, 12, 2017.01, [URL], Coaxial Helicity Injection (CHI) has now been implemented in QUEST. The goals for the first transient CHI experiments were to establish reliable gas breakdown conditions, and to measure CHI-produced toroidal current generation. Both these objectives were successfully met. Toroidal currents up to 29 kA were measured. Interestingly, these first plasmas on QUEST also suggest the formation of small amounts of closed magnetic flux surfaces..
45. Kengoh Kuroda, Roger Raman, Kazuaki Hanada, Makoto Hasegawa, Takumi Onchi, Masayuki Ono, Thomas R. Jarboe, Brian A. Nelson, Masayoshi Nagata, Osamu Mitarai, Kazuo Nakamura, Hiroshi Idei, John Rogers, Shoji Kawasaki, Takahiro Nagata, Arseniy Kuzmin, Shinichiro Kojima, Osamu Watanabe, Aki Higashijima, Yuichi Takase, Atsushi Fukuyama, Erratum
Current Start-Up Using the New CHI System [Plasma Fusion Res., 12, (2017) (1202020)] DOI: 10.1585/pfr.12.1202020, Plasma and Fusion Research, 10.1585/pfr.12.1902026, 12, 2017.01, [URL], A typographical error of spelling occurred in author list of the published article. The correct author list is described as above on this page..
46. Makoto Hasegawa, Kazuo Nakamura, Hideki Zushi, Kazuaki Hanada, akihide fujisawa, Kazutoshi Tokunaga, Hiroshi Idei, Yoshihiko Nagashima, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Current status and prospect of plasma control system for steady-state operation on QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2016.04.016, 112, 699-702, 2016.11, [URL], The plasma control system (PCS) of QUEST is developed according to the progress of QUEST project. Since one of the critical goals of the project is to achieve the steady-state operation with high temperature vacuum vessel wall, the PCS is also required to have the capability to control the plasma for a long period. For the increase of the loads to processing power of the PCS, the PCS is decentralized with the use of reflective memories (RFMs). The PCS controls the plasma edge position with the real-time identification of plasma current and its position. This identification is done with not only flux loops but also hall sensors. The gas fueling method by piezo valve with monitoring the Hα signal filtered by a digital low-pass filter are proposed and suitable for the steady-state operation on QUEST. The present status and prospect of the PCS are presented with recent topics..
47. Kazuaki Hanada, H. Zushi, Hiroshi Idei, K. Nakamura, M. Ishiguro, S. Tashima, E. I. Kalinnikova, Yoshihiko Nagashima, Makoto Hasegawa, akihide fujisawa, A. Higashijima, S. Kawasaki, H. Nakashima, O. Mitarai, A. Fukuyama, Y. Takase, X. Gao, H. Liu, J. Qian, M. Ono, R. Raman, Power Balance Estimation in Long Duration Discharges on QUEST, Plasma Science and Technology, 10.1088/1009-0630/18/11/03, 18, 11, 1069-1075, 2016.11, [URL], Fully non-inductive plasma start-up was successfully achieved by using a well-controlled microwave source on the spherical tokamak, QUEST. Non-inductive plasmas were maintained for approximately 3-5 min, during which time power balance estimates could be achieved by monitoring wall and cooling-water temperatures. Approximately 70%-90% of the injected power could be accounted for by calorimetric measurements and approximately half of the injected power was found to be deposited on the vessel wall, which is slightly dependent on the magnetic configuration. The power distribution to water-cooled limiters, which are expected to be exposed to local heat loads, depends significantly on the magnetic configuration, however some of the deposited power is due to energetic electrons, which have large poloidal orbits and are likely to be deposited on the plasma facing components..
48. T. Kariya, T. Imai, R. Minami, K. Tsumura, Y. Ebashi, Hiroshi Idei, Kazuaki Hanada, M. Ono, K. Komurasaki, T. Numakura, Y. Endo, Y. Nakashima, Development of 28/35 GHz dual-frequency gyrotron for ECH study, 11th International Conference on Open Magnetic Systems for Plasma Confinement, OS 2016
Open Magnetic Systems for Plasma Confinement, OS 2016
Proceedings of the 11th International Conference on Open Magnetic Systems for Plasma Confinement
, 10.1063/1.4964176, 1771, 2016.10, [URL], The high power and long pulse operation of the gyrotron as well as efficient transmission of its output are quite important for achieving improved plasma performances. A 28 GHz 1 MW gyrotron developed for GAMMA 10/PDX achieved an output power of 1.38 MW in 2015 experiment after the power supply was improved. Furthermore, a new 28/35 GHz dual-frequency gyrotron (2 MW 3 s and 0.4 MW CW) for QUEST, NSTX-U, Heliotron J and GAMMA 10/PDX has been fabricated, after the preliminary test of a double-disk sapphire window installed in the gyrotron was performed. In the first experimental test, the oscillation of the main mode was confirmed at a frequency of 28.036 GHz with a Gaussian-like beam and an output power of 1.22 MW..
49. Md Mahbub Alam, Kazuo Nakamura, Hiroshi Idei, Makoto Hasegawa, Kazutoshi Tokunaga, Kuniaki Araki, Kazuaki Hanada, akihide fujisawa, Yoshihiko Nagashima, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Fan Xia, Osamu Mitarai, Guiding Center Orbit Calculation for Evaluating the Current Density Distributions of the Electrons in Electron Cyclotron Heating on QUEST, IEEE Transactions on Plasma Science, 10.1109/TPS.2016.2570815, 44, 9, 1666-1671, 2016.09, [URL], In order to evaluate the magnetic surface current density distributions, the electron guiding center orbits were calculated with the equilibrium fitting plasma equilibrium analysis. The current density distributions in electron cyclotron-heated plasma were estimated from the orbit analyses in the equilibrium plasma shaping for the fundamental and the second-harmonic resonant electrons separately. The current density distribution profiles on the equatorial plane were obtained for the electrons with initially positive and negative velocities parallel to the magnetic field direction as well as the trapped electrons. The surface averaged current density profiles of the closed flux surfaces were also evaluated. A significant amount of the positive current density distributions appeared outside the last closed flux surface (LCFS), while all the negative current density distributions were evaluated inside the LCFS. The trapped electrons being the second-harmonic electron cyclotron resonant contributed the negative current inside the LCFS. The positive current density distributions outside the LCFS were significant for the driven current density for both the fundamental and second-harmonic resonances..
50. Takumi Onchi, H. Zushi, K. Mishra, Y. Oyama, Yoshihiko Nagashima, Kazuaki Hanada, Hiroshi Idei, Makoto Hasegawa, A. Kuzmin, H. Miura, K. Nakamura, akihide fujisawa, K. Nagaoka, Response of the far scrape-off layer plasma to strong gas puffing in the high poloidal beta configuration of the QUEST spherical tokamak, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/58/11/115004, 58, 11, 2016.09, [URL], The response of the far scrape-off layer (far-SOL) to strong gas puffing (SGP), and its role as the boundary condition for core plasma, are investigated using a two-point Langmuir probe measurement in the high poloidal beta configuration in the QUEST spherical tokamak. The temperature and heat flux behave in an opposite way in the far-SOL and end-plate region after SGP, although SGP increases the density globally. The apparent density decay time in the far-SOL area is much longer than that in the core. Significant co-current flow is driven solely by the electron cyclotron wave in the far-SOL flow. Sheared flow is also observed in the perpendicular velocity profile during the recovered current flat-top phase, and such flow profiles are flattened by SGP. These flow profiles are attributed not only to drift-driven flow but also to transport-driven flow, the sink effect on the end-plate, and the balance of the neutral particle source..
51. Santanu Banerjee, H. Zushi, N. Nishino, K. Mishra, Y. Mahira, S. Tashima, A. Ejiri, T. Yamaguchi, Takumi Onchi, Yoshihiko Nagashima, Kazuaki Hanada, K. Nakamura, Hiroshi Idei, Makoto Hasegawa, akihide fujisawa, A. Kuzmin, K. Matsuoka, Observation of an edge coherent mode and poloidal flow in the electron cyclotron wave induced high βp plasma in QUEST, Physics of Plasmas, 10.1063/1.4960117, 23, 8, 2016.08, [URL], Fluctuations are measured in the edge and scrape-off layer (SOL) of QUEST using fast visible imaging diagnostic. Electron cyclotron wave injection in the Ohmic plasma features excitation of low frequency coherent fluctuations near the separatrix and enhanced cross-field transport. Plasma shifts from initial high field side limiter bound (inboard limited, IL) towards inboard poloidal null (IPN) configuration with steepening of the density profile at the edge. This may have facilitated the increased edge and SOL fluctuation activities. Observation of the coherent mode, associated plasma flow, and particle out-flux, for the first time in the IPN plasma configuration in a spherical tokamak may provide further impetus to the edge and SOL turbulence studies in tokamaks..
52. A. Kuzmin, H. Zushi, I. Takagi, S. K. Sharma, Y. Hirooka, M. Kobayashi, M. Sakamoto, Kazuaki Hanada, Takumi Onchi, Y. Oyama, N. Youshida, K. Nakamura, akihide fujisawa, Hiroshi Idei, Yoshihiko Nagashima, Makoto Hasegawa, K. Mishra, Hydrogen flux measurements with permeation probes in spherical tokamak QUEST, Vacuum, 10.1016/j.vacuum.2016.04.025, 129, 178-182, 2016.07, [URL], Poloidal and radial distributions of the hydrogen flux, both atomic and ion, to the plasma facing materials (PFMs) are measured with four fixed and one movable PdCu membrane probes in the QUEST spherical tokamak. Direct information about hydrogen retention in the areas far from main plasma-wall interaction is essential because the significant part of the global retention is due to atomic hydrogen. Incident hydrogen flux Γinc is numerically reconstructed by fitting the experimentally measured hydrogen flux Γp, permeated through the membrane. The sensitivity of the probe is improved when compared with other work which allows dynamic changes of the retention flux to be monitored, allowing detection of 10% of the Γinc modulation, or ∼1017 H m−2s−1..
53. Md Mahbub Alam, Kazuo Nakamura, Makoto Hasegawa, Kazutoshi Tokunaga, Kuniaki Araki, Hideki Zushi, Kazuaki Hanada, akihide fujisawa, Hiroshi Idei, Yoshihiko Nagashima, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Fan Xia, Osamu Mitarai, Current density calculation from particle orbit in RF-driven divertor plasma on QUEST, 26th IEEE Symposium on Fusion Engineering, SOFE 2015
2015 IEEE 26th Symposium on Fusion Engineering, SOFE 2015
, 10.1109/SOFE.2015.7482308, 2016-May, 2016.05, [URL], We investigate and calculate particle orbits and the effect of particle orbits on plasma current density for nonrelativistic resonance condition in the present RF-driven divertor plasma on QUEST. We surveyed particle orbits for different values of parallel refractive index, particle initial positions and pitch angles on fundamental and second harmonic resonance conditions. We observed that for fundamental harmonic resonance condition when particle orbits are plotted on the poloidal cross-section for positive values of parallel refractive index, these orbits are started from the resonance surface and produced their orbits around the LCFS (Large Closed Flux Surface). These orbits carry positive current. When particle orbits are plotted for negative values of parallel refractive index, these orbits are started from resonance surface, but remained at the inside of the LCFS. These orbits carry negative current that reduced the overall plasma current. For second harmonic resonance condition when particle orbits are plotted on the poloidal cross-section most of the orbits remained in inside the LCFS and carry positive current. When we consider the value of parallel refractive index-0.4 and +0.4 some particle orbits arrived at the limiter and become lost particles. On the other hand, when we consider particle initial positions 0.16 m or more vertically far from the mid plane some banana orbits are produced. These banana orbits make the current density profile maximum at low field side region. From this calculation we got a hollow current density profile with current density peak at the low field side region outside of the LCFS. From this calculation we can infer that parabolic current density profile is possible, if we set the resonance surface outside of the magnetic axis by increasing the toroidal magnetic field coil current and make the plasma position inward by increasing vertical field coil current..
54. Hiroshi Idei, K. Mishra, M. K. Yamamoto, M. Hamasaki, akihide fujisawa, Yoshihiko Nagashima, Y. Hayashi, Takumi Onchi, Kazuaki Hanada, H. Zushi, Adaptive-Array electron cyclotron emission diagnostics using data streaming in a software defined radio system, Journal of Instrumentation, 10.1088/1748-0221/11/04/C04010, 11, 4, 2016.04, [URL], Measurement of the Electron Cyclotron Emission (ECE) spectrum is one of the most popular electron temperature diagnostics in nuclear fusion plasma research. A 2-dimensional ECE imaging systemwas developed with an adaptive-Array approach. Aradio-frequency (RF) heterodyne detection system with Software Defined Radio (SDR) devices and a phased-Array receiver antenna was used to measure the phase and amplitude of the ECE wave. The SDR heterodyne system could continuously measure the phase and amplitude with sufficient accuracy and time resolution while the previous digitizer system could only acquire data at specific times. Robust streaming phase measurements for adaptive-Arrayed continuous ECE diagnostics were demonstrated using Fast Fourier Transform (FFT) analysis with the SDR system. The emission field pattern was reconstructed using adaptive-Array analysis. The reconstructed profileswere discussed using profiles calculated from coherent single-frequency radiation from the phase array antenna..
55. Kishore Mishra, Hideki Zushi, Hiroshi Idei, Takumi Onchi, Makoto Hasegawa, Kazuaki Hanada,, Origin and Evolution of Spontaneous Rotation in Plasma under Different Magnetic Field Geometries in Tokamak QUEST, IEEE Transactions on Plasma Science, 10.1109/TPS.2016.2522765, 44, 4, 441-447, 2016.04, [URL], Spontaneous toroidal rotation of the plasma is observed in the spherical tokamak QUEST with the help of electron cyclotron resonance (ECR) heating and without the use of any externally injected momentum. Several vertical magnetic field ( Bz) configurations with varying mirror ratio (M) (a measure of field curvature) are applied and evolution of rotation is studied with the help of Doppler spectroscopy of bulk and impurity ions. Significant toroidal rotation (Vφ-6km/s) is initiated in the open magnetic field configuration during the initial plasma breakdown phase, which is later sustained ( Vφ- 20km/s) in a closed magnetic field configuration in steady state. Rotational velocity is primarily along the cocurrent direction and is found to be proportional to the Bz strength and the resulting plasma current. High M and Bz are demonstrated to be the two specific external controls by which rotation can be initiated in the plasma. The rotation in open field lines is found to be initiated at the ECR layer in the slablike plasma, which is evolved to produce a sustained rotation in the natural divertor inboard poloidal field null equilibrium in QUEST..
56. H. Idei, K.Mishra, M.K.Yamamoto, A. Fujisawa, Y. Nagashima, M.Hamasaki, Y.Hayashi, T. Onchi, K.Hanada, H. Zushi, QUEST Team, Multiple Wall-Reflection Effect in Adaptive-array Differential-phase Reflectometry on QUEST, Journal of Instrumentation, 11, C01014, 2016.01, A phased array antenna and Software-Defined Radio (SDR) heterodyne-detection systems have been developed for adaptive array approaches in reflectometry on the QUEST. In the QUEST device considered as a large oversized cavity, standing wave (multiple wall-reflection) effect was significantly observed with distorted amplitude and phase evolution even if the adaptive array analyses were applied. The distorted fields were analyzed by Fast Fourier Transform (FFT) in wavenumber domain to treat separately the components with and without wall reflections. The differential phase evolution was properly obtained from the distorted field evolution by the FFT procedures. A frequency derivative method has been proposed to overcome the multiple-wall reflection effect, and SDR super-heterodyned components with small frequency difference for the derivative method were correctly obtained using the FFT analysis..
57. Hiroe Igami, Atsushi Fukuyama, Hiroshi Idei, Kazunobu Nagasaki, Yuki Goto, Shin Kubo, Takashi Shimozuma, Yasuo Yoshimura, Hiromi Takahashi, Toru I. Tsujimura, Ryohei Makino, Comparison between fullwave and ray-tracing calculations to examine scenarios for electron bernstein wave heating in LHD, Plasma and Fusion Research, 10.1585/pfr.11.2403098, 11, 1, 2016.01, [URL], With the use of the density scale length and the magnetic field strength around the O-X mode conversion region in the LHD for 77 GHz EC waves, the full wave calculations by the TASK/WF2D code have been performed. The wave patterns obtained by full wave calculation have been compared with the trajectories obtained by multi ray tracing calculations. For the X-mode and the O-mode reflected near each cutoff, wave patterns obtained by full wave calculations and trajectories obtained by multi ray-tracing correspond to each other well. On the contrary, trajectories of the rays restarted at the high field side of the evanescent region between the plasma and the left handed cutoffs do not cover fully the wave patterns after the O-X mode conversion obtained by full wave calculations. Improvement of the manner to restart the ray-tracing is required. This improvement can provide a more precise view of the propagation of the EBWs and may contribute to examining scenarios for electron Bernstein wave heating..
58. Shabbir A. Khan, Atsushi Fukuyama, Hiroe Igami, Hiroshi Idei, Kinetic full wave analysis of electron cyclotron wave mode conversion in tokamak plasmas, Plasma and Fusion Research, 10.1585/pfr.11.2403070, 11, Specialissue1, 2016.01, [URL], By employing the integral formulation of dielectric tensor, we have introduced the kinetic full wave analysis of ordinary-extraordinary-Bernstein (O-X-B) mode conversion in tokamak plasma in one dimension on the basis of TASK/W1 code using the finite element method. The boundary value problem of Maxwell's equation is solved and the finite Larmor radius effects are represented by integral formulation. The O-X-B mode conversion and the absorption near the cyclotron harmonic resonance are successfully described..
59. Hiroshi Idei, K. Mishra, M. K. Yamamoto, akihide fujisawa, Yoshihiko Nagashima, M. Hamasaki, Y. Hayashi, Takumi Onchi, Kazuaki Hanada, H. Zushi, Multiple wall-reflection effect in adaptive-array differential-phase reflectometry on QUEST, Journal of Instrumentation, 10.1088/1748-0221/11/01/C01014, 11, 1, 2016.01, [URL], A phased array antenna and Software-Defined Radio (SDR) heterodyne-detection systems have been developed for adaptive array approaches in reflectometry on the QUEST. In the QUEST device considered as a large oversized cavity, standing wave (multiple wall-reflection) effect was significantly observed with distorted amplitude and phase evolution even if the adaptive array analyses were applied. The distorted fields were analyzed by Fast Fourier Transform (FFT) in wavenumber domain to treat separately the components with and without wall reflections. The differential phase evolution was properly obtained from the distorted field evolution by the FFT procedures. A frequency derivative method has been proposed to overcome the multiple-wall reflection effect, and SDR super-heterodyned components with small frequency difference for the derivative method were correctly obtained using the FFT analysis..
60. K.Nakamura, M.M.Alam, Y.Z.Jiang, O.Mitarai, K.kurihara, Y.Kawamata, M.Sueoka, M.Takechi, M.Hasegawa, K.Tokunaga, K.Araki, H.Zushi, K.Hanada, A.Fujisawa, H. Idei, Y.Nagashima, S.Kawasaki, H.Nakashima, A.Higashijima, Analysis of plasma equilibrium based on orbit-driven current density profile in steady-state plasma on QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2015.11.035, 2015.12.
61. O.Mitarai, K.Nakamura, M.Hasegawa, T.Onchi, H.Idei, A.Fujisawa, K.Hanada, H.Zushi, A.Higashijima, H.Nakashima, S.Kawasaki, K.Matsuoka, S.Koike, T.Takahashi, H.Tsutsui, Comparative studies of inner and outer divertor discharges and a fueling study in QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2015.12.022, 2015.12.
62. Md Mahbub Alam, K.Nakamura, Fan Xia, O.Mitarai, M.Hasegawa, K.Tokunaga, K.Araki, H.Zushi, K.Hanada, A.Fujisawa, H. Idei, Y.Nagashima, S.Kawasaki, H.Nakashima, A.Higashijima, T.Nagata, Comparison of current density profiles based on particle orbit-driven current in steady-state plasma on QUEST, Fusion Engineering and Design, 10.1016/j.fusengdes.2015.11.007, 2015.11.
63. T.Fujita, S.Hamaguchi, H.Igami, S.Masuzaki, T.Morisaki, H.Idei, et.al., Overview of transport and MHD stability study: focusing on the impact of magnetic field topology in the Large Helical Device, NUCLEAR FUSION, 10.1088/0029-5515/55/10/104018, 55, 10, 2015.10.
64. M.Hasegawa, K.Nakamura, H.Zushi, K.Hanada, A.Fujisawa, O.Mitarai, K. Tokunaga, H.Idei, Y.Nagashima, S.Kawasaki, H.Nakashima, A.Higashijima, Development of a high-performance control system by decentralization with reflective memory on QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2015.06.054, 96-97, 629-632, 2015.10.
65. H.Idei, M.Yamamoto, Radiation Measurements using Adaptive-array Technique, 九州大学応用力学研究所所報No.149, 42-46, 2015.09.
66. A. Kuzmin, H. Zushi, I. Takagi, S.K.Sharma, A. Rusinov, Y. Inoue, Y. Hirooka, H. Zhou, M. Kobayashi, M.Sakamoto, K. Hanada, N. Yoshida, K. Nakamura, A. Fujisawa, K. Matsuoka, H. Idei, Y. Nagashima, M. Hasegawa, T. Onchi, S. Banerjee, Global gas balance and influence of atomic hydrogen irradiation on the wall inventory in steady-state operation of QUEST tokamak, Journal of Nuclear Materials, 10.1016/j.jnucmat.2014.12.092, 463, 1087-1090, 2015.08.
67. T.Onchi, H.Zushi, K.Mishra, Y.Mahira, K.Nagaoka, K.Hanada, H.Idei, M.Hasegawa, K.Nakamura, A.Fujisawa, Y.Nagashima, K.Matsuoka, S.Tashima, S.Banerjee, A.Kuzmin, S.Kawasaki, H.Nakashima, A.Higashijima, O.Wanatabe, Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST, Physics of Plasmas, 22, 8, 082513, 2015.08.
68. T.Onchi, Y.Mahira, K.Nagaoka, S.Tashima, S.Banerjee, K.Mishra, H.Idei, K.Hanada, K.Nakamura, A.Fujisawa, Y.Nagashima, M.Hasegawa, K.Matsuoka, A.Kuzmin, O.Wanatabe, S.Kawasaki, H.Nakashima, A.Higashijima, Observation of heat flux and plasma flow in scrape off layer in QUEST, Journal of Nuclear Materials, 10.1016/j.jnucmat.2014.11.136, 463, 428-431, 2015.08.
69. K.Hanada, H.Zushi, N.Yoshida, N.Yugami, T.Honda, M.Hasegawa, K.Mishra, A.Kuzmin, K.Nakamura, A.Fujisawa, H.Idei, Y.Nagashima, O.Watanabe, T.Onchi, H. Watanabe, K. Tokunaga, S.Kawasaki, H.Nakashima, A.Higashijima, Particle balance in long duration RF driven plasmas on QUEST, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2015.01.013, 463, 1084-1086, 2015.08.
70. T.Kariya, T.Imai, R.Minami, T.Mumakura, T.Eguchi, T.Kato, Y.Endo, M.Ichimura, H.Idei, et.al., Development of gyrotrons for fusion with power exceeding 1MW over a wide frequency range, Nuclear Fusion, 093009, 2015.08.
71. T. Kariya, T. Imai, R. Minami, T. Numakura, T. Eguchi, T. Kato, Y. Endo, M. Ichimura, T. Shimozuma, S. Kubo, H. Takahashi, Y. Yoshimura, H. Igami, S. Ito, T. Mutoh, K. Sakamoto, H. Idei, H. Zushi, K. Nagasaki, F. Sano, M. Ono, Y. Mitsunaka, Development of gyrotrons for fusion with power exceeding 1 MW over a wide frequency range, Nuclear Fusion, 10.1088/0029-5515/55/9/093009, 55, 9, 2015.08, [URL], Megawatt-class gyrotrons covering a wide frequency range (14 GHz-300 GHz) are in increasing demand for nuclear fusion. Recent electron cyclotron heating and electron cyclotron current drive experiments highlight a requirement of megawatt-scale gyrotrons at a relatively lower frequency (14-35 GHz) range of some plasma devices, like GAMMA 10/PDX of the University of Tsukuba, QUEST of Kyushu University, NSTX-U of Princeton Plasma Physics Laboratory, and Heliotron J of Kyoto University. Collaborative studies for designing a new 28 GHz/35 GHz dual-frequency gyrotron and a 14 GHz gyrotron have commenced. Operation above 1 MW of 28 GHz/35 GHz dual oscillation was demonstrated experimentally. Further in the design of dual-frequency gyrotron, operations with 2 MW 3 s and 0.4 MW CW (continuous wave) at 28 GHz, and power exceeding 1 MW for 3 s at 34.8 GHz have been shown to be feasible. The 14 GHz gyrotron is expected to operate above 1 MW. We are also developing higher frequency gyrotrons (77-300 GHz). The joint program of National Institute for Fusion Science and the University of Tsukuba developed two new 154 GHz gyrotrons for the large helical device after the demonstration of three 77 GHz gyrotrons. The 154 GHz gyrotrons achieved a maximum output power of 1.25 MW and quasi-CW operation of 0.35 MW for 30 min..
72. T. Onchi, H. Zushi, K. Mishra, Y. Mahira, K. Nagaoka, K. Hanada, H. Idei, M. Hasegawa, K. Nakamura, A. Fujisawa, Y. Nagashima, K. Matsuoka, S. Tashima, S. Banerjee, A. Kuzmin, S. Kawasaki, H. Nakashima, A. Higashijima, O. Watanabe, Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST, Physics of Plasmas, 10.1063/1.4928878, 22, 8, 2015.08, [URL], Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (Ip) ramp-up phase, high heat flux (>1 MW/m2) and supersonic flow (Mach number M > 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of Ip at 20 Hz is observed. Heat flux and subsonic plasma flow in the far-SOL are modified corresponding to the Ip-oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low-Ip phase. Modification of plasma flow in the far SOL occurs earlier than the Ip crash. The M-Ip curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core-SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of Ip in the IPN configuration..
73. Kishore Mishra, H. Zushi, H. Idei, M. Hasegawa, T. Onchi, S. Tashima, S. Banerjee, H. Hanada, H. Togashi, T. Yamaguchi, A. Ejiri, Y. Takase, K. Nakamura, A. Fujisawa, Y. Nagashima, A. Kuzmin, Self organization of high βp plasma equilibrium with an inboard poloidal magnetic field null in QUEST, Nuclear Fusion, 10.1088/0029-5515/55/8/083009, 55, 8, 2015.08, [URL], Successful production of high βp plasmas (εβp 1) fully non-inductively (NI) and their long pulse sustainment with the help of modest power (<100 kW) of electron cyclotron waves is demonstrated. High βp plasmas are found for the first time to be naturally self organized to form a stable natural inboard poloidal field null (IPN) equilibrium. A critical βp value is identified, which defines the transition boundary from inboard limiter (IL) to IPN equilibrium. A new feature of plasma self organization is evidenced, which enhances its negative triangular shape to sustain high βp. These results show a relatively simple method to produce and sustain high βp plasma close to the equilibrium limit in a stable configuration exploiting its self organization property..
74. H. Idei, T. Kobayashi, S. Moriyama, A. Isayama, M.Sakaguchi, W. Kasparek, Conceptual Design of Dual Baseline-Frequency Fast Directional Switch using Square Corrugated Waveguide Splitter/Combiner, Journal of Infared, Millimeter, and Teraherts Waves, 36, 7, 662-674, 2015.07.
75. K. Mishra, H. Zushi, H. Idei, M. Hasegawa, T. Onchi, S.Tashima, S. Banerjee, K. Hanada, H. Togashi, T. Yamaguchi, A. Ejiri, Y. Takase, K. Nakamura, A. Fujisawa, Y. Nagashima, A. Kuzmin, Self organization of high βp plasma equilibrium with an inboard poloidal magnetic field null in QUEST, Nuclear Fusion, online publish, 2015.07.
76. T.Kariya, R.Minami, T.Imai, T.Kato, H.Idei, K.Hanada, H.Zushi, T.Numakura, Y.Endo, M.Ichimura, DEVELOPMENT OF 28 GHz GYROTRON FOR COOPERATIVE ECH STUDY, FUSION SCIENCE AND TECHNOLOGY, 68, 1, 147-151, 2015.07.
77. H. Idei, T. Kobayashi, S. Moriyama, A. Isayama, M. Sakaguchi, W. Kasparek, Conceptual Design of Dual Baseline-Frequency Fast Directional Switch using Square Corrugated Waveguide Splitter/Combiner, Journal of Infrared, Millimeter, and Terahertz Waves, 10.1007/s10762-014-0138-0, 36, 7, 662-674, 2015.07, [URL], A FAst DIrectional Switch(FADIS) performance based on steep slope in a diplexer function was considered for dual-frequency (dual-f) applications to switch the transmission line with small frequency control. A diplexer of FADIS using a Square Corrugated Waveguide (SCW) splitter was designed as one of the most attractive candidates for the dual-f operation. The splitter performance was a key issue for the dual-f operation, and extended operation regions in splitter operations have been considered and surveyed using mode contents analysis based on matching coefficient evaluation. Some operational branches with high matching coefficients (>0.9) were found, and a new operating parameters were proposed for the dual-f operation in the JT-60SA Electron Cyclotron Hearing and Current Drive (ECHCD) system. Radiation pattern distributions from the SCW splitter were defined very well with no serious side lobes in the dual-f operation. In double loop ring resonator system, the diplexer frequency response was sufficiently steep to switch the outputs of the JT-60SA dual-f gyrotron..
78. T. Kariya, R. Minami, T. Imai, T. Kato, Hiroshi Idei, Kazuaki Hanada, H. Zushi, T. Numakura, Y. Endo, M. Ichimura, Development of 28 GHz Gyrotron for Cooperative ECH Study, Fusion Science and Technology, 10.13182/FST14-848, 68, 1, 147-151, 2015.07, [URL], At the Plasma Research Center at University of Tsukuba, development of megawatt gyrotrons is being performed as a collaborative electron cyclotron heating (ECH) study with some research organizations. A 28 GHz 1 MW 1 s gyrotron has been developed to upgrade the GAMMA 10/PDX ECH systems. To improve the oscillation efficiency in high current regions, the magnetron injection gun (MIG) of the 28 GHz gyrotron has been modified. Output power of 1.25 MW has been achieved with this gyrotron. For the first step of the collaborative research between Tsukuba University and Kyushu University, the Tsukuba 28 GHz gyrotron was adapted to the Q-shu University Experiment with Steady-State Spherical Tokamak (QUEST) ECH system, and the plasma heating and current drive effect were demonstrated. We obtained successful results, including an electron cyclotron-driven plasma current of 66 kA in the QUEST plasma experiment. For the next step of the collaborative research, the design targets of a 2 MW 3 s and 0.4 MW continuous wave have been achieved in a design study of a new 28 GHz gyrotron..
79. , T. Shimozuma, H. Igami, S. Kubo, Y. Yoshimura, H. Takahashi, M. Osakabe, T. Mutoh, M. Nishiura, H. Idei, K. Nagasaki, N. Marushchenko, Y. Turkin, Optimization of the high harmonic ECRH scenario to extend a heating plasma parameter range in LHD, Nuclear Fusion, 10.1088/0029-5515/55/6/063035, 55, 6, 2015.06, [URL], Effectiveness of high harmonic electron cyclotron resonance heating (ECRH) was investigated by both experiments and ray-trace analyses. The conditions of both the EC wave injection and the magnetic field configuration were optimized in the large helical device. In the case of the second harmonic ordinary mode injection with a frequency of 77 GHz and with the optimized injection angle, about 30-40% absorption could be kept beyond the cut-off density of the second harmonic extraordinary (X2) mode, which is 3.7 × 1019 m-3. In the third harmonic X (X3) mode heating experiment, the dependence of the absorption rate on plasma density and temperature of the target plasma was precisely investigated and compared with the ray-trace (TRAVIS code) calculation. The calculation results of the absorption rate show fairly good agreement with the experimentally obtained ones on the plasma-parameter dependences. The maximum absorption rate in the X3 heating experiment attained approximately 40% around the electron density of 1.5 × 1019 m-3 and the electron temperature of 1.2 keV. Superposed stepwise injection from three gyrotrons with a total of 3 MW increased the central electron temperature to about 3.5 times of the initial target plasma temperature of 0.6 keV. This shows that the temperature increase improves the absorption rate of the subsequent injection..
80. T.Shimozuma, H. Igami, S. Kubo, Y. Yoshimura, H. Takahashi, M. Osakabe, T. Mutoh, M. Nishiura, H. Idei, K. Nagasaki, N. Marushchenko, Y. Turkin, The LHD Experiment Group, Optimization of the high harmonic ECRH scenario to extend a heating plasma parameter range in LHD, Nuclear Fusion, 55, 063035(8pp), 2015.05.
81. H. Idei, S. Moriyama, T. Kobayashi, A. Isayama, M. Sakaguchi, W. Kasparek, Research and Development of 2-frequency (110/138GHz) FADIS for JT-60SA ECH/ECCD Experiments, EPJ Web of Conferences, http://dx.doi.org/10.1051/epjconf/20158704009, 87, 2015.03, A FAst DIrectional Switch (FADIS) of 2-frequency (2-ƒ) gyrotron system for the JT-60SA project is being developed under collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University. At first, the frequency drift and dip in the gyrotron operation were measured to consider which kind of FADIS is preferred for application in the Electron Cyclotron Heating and Current Drive (ECHCD) system for the JT- 60SA. Various types of the FADIS have been considered. A square corrugated waveguide diplexer system with double resonant rings was considered as one of the most attractive FADIS systems for stable high-power and long-pulse operations in the 2-ƒ JT-60SA ECHCD system..
82. S.Banerjee, H.Zushi, N.Nishino, K.Mishra, T.Onchi, A.Kuzmin, Y.Nagashima, K.Hanada, K.Nakamura, H. Idei, M.Hasegawa, A.Fujisawa, Dynamical programming based turbulence velocimetry for fast visible imaging of tokamak plasma, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.4914838, 86, 3, 2015.03.
83. K.Mishra, H.Zushi, H.Idei, M.Hasegawa, K.Hanada, High beta(p) plasma formation using off-axis ECCD in Ohmic heated plasma in the spherical tokamak QUEST, EC18 - 18TH JOINT WORKSHOP ON ELECTRON CYCLOTRON EMISSION AND ELECTRON CYCLOTRON RESONANCE HEATING, 10.1051/epjconf/20158702012, 87, 2015.03.
84. H.Igami, S.Kubo, S.Shimozuma, Y.Yoshimura, H.Takahashi, S.Kamio, S.Kobayashi, S.Ito, Y.Mizuno, K.Okada, R.Makino, S.Ogasawara, K.kobayashi, M.Osakabe, K.Nagasaki, H.Idei, T.Mitoh, Recent Upgrading of ECRH System and Studies to Improve ECRH Performance in the LHD, EPJ Web of Conferences, dx.doi.org/10.1051/epjconf/20158702011 , 87, 02011, 2015.03.
85. , Hiroe Igami, Shin Kubo, Takashi Shimozuma, Yasuo Yoshimura, Hiromi Takahashi, Shuji Kamio, Sakuji Kobayashi, Satoshi Ito, Yoshinori Mizuno, Kohta Okada, Ryohei Makino, Shinya Ogasawara, Kenya Kobayashi, Masaki Osakabe, Kazunobu Nagasaki, Hiroshi Idei, Takashi Mutoh, Recent upgrading of ECRH system and studies to improve ECRH performance in the LHD, 18th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, EC 2014
EPJ Web of Conferences
, 10.1051/epjconf/20158702011, 87, 2015.03, [URL], This paper reports the recent status of the ECRH system in the LHD and introduces the experimental results that suggest the reasonable effects of the wave-plasma interaction in the plasma boundary including outside the LCFS. With increasing the available ECRH power, ECRH/ECCD have been performed in higher density target plasmas where the mode coupling between the O-mode and the X-mode caused by the magnetic shear occurs for long distance in the low density region of the plasma boundary including the ergodic layer outside the LCFS. In such a case, the incident polarization should be set by taking into account the mode coupling effect. Moreover, the refraction in the boundary region should be considered for accurate numerical prediction of the wave trajectory and power absorption with use of the ray-tracing calculation..
86. H. Idei, S. Moriyama, T. Kobayashi, A. Isayama, M. Sakaguchi, W. Kasparek, Research and development of 2-frequency (110/138 GHz) FADIS for JT-60SA ECHCD system, 18th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, EC 2014
EPJ Web of Conferences
, 10.1051/epjconf/20158704009, 87, 2015.03, [URL], A FAst DIrectional Switch (FADIS) of 2-frequency (2-f{hook}) gyrotron system for the JT-60SA project is being developed under collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University. At first, the frequency drift and dip in the gyrotron operation were measured to consider which kind of FADIS is preferred for application in the Electron Cyclotron Heating and Current Drive (ECHCD) system for the JT- 60SA. Various types of the FADIS have been considered. A square corrugated waveguide diplexer system with double resonant rings was considered as one of the most attractive FADIS systems for stable high-power and long-pulse operations in the 2-f{hook} JT-60SA ECHCD system..
87. Hiroki Miura, Kazuaki Hanada, Hideki Zushi, Kazuo Nakamura, Akihide Fujisawa, Hiroshi Idei, Yoshihiko Nagashima, Makoto Hasegawa, Hisatoshi Nakashima, Shoji Kawasaki, Aki Higashijima, Osamu Mitarai, Atsushi Fukuyama, Yuichi Takase, Comparison between non-inductive plasma current start-up using ECRH with and without fundamental resonance on QUEST, Plasma and Fusion Research, 10.1585/pfr.10.3402066, 10, 2015.01, [URL], Comparison between non-inductive plasma current start-up using electron cyclotron resonance heating (ECRH) with and without fundamental (1st) resonance using 8.2-GHz microwave is experimentally performed on QUEST. Results of soft X-ray measurements in different energy ranges indicate significant difference in the number of current-carrying electrons with and without fundamental resonance. Numerical calculations show effective extendibility of electron energy in ECRH of fundamental resonance..
88. K. Ida, M. Yoshinuma, H. Tsuchiya, T. Kobayashi, C. Suzuki, M. Yokoyama, A. Shimizu, K. Nagaoka, S. Inagaki, K. Itoh, T. Akiyama, M. Emoto, T. Evans, A. Dinklage, X. Du, K. Fujii, M. Goto, T. Goto, M. Hasuo, C. Hidalgo, K. Ichiguchi, A. Ishizawa, M. Jakubowski, K. Kamiya, H. Kasahara, G. Kawamura, D. Kato, M. Kobayashi, S. Morita, K. Mukai, I. Murakami, S. Murakami, Y. Narushima, M. Nunami, S. Ohdach, N. Ohno, M. Osakabe, N. Pablant, S. Sakakibara, T. Seki, T. Shimozuma, M. Shoji, S. Sudo, K. Tanaka, T. Tokuzawa, Y. Todo, H. Wang, H. Yamada, Y. Takeiri, T. Mutoh, S. Imagawa, T. Mito, Y. Nagayama, K. Y. Watanabe, N. Ashikawa, H. Chikaraishi, A. Ejiri, M. Furukawa, T. Fujita, S. Hamaguchi, H. Igami, M. Isobe, S. Masuzaki, T. Morisaki, G. Motojima, K. Nagasaki, H. Nakano, Y. Oya, Y. Suzuki, R. Sakamoto, M. Sakamoto, A. Sanpei, H. Takahashi, M. Tokitani, Y. Ueda, Y. Yoshimura, S. Yamamoto, K. Nishimura, H. Sugama, T. Yamamoto, H. Idei, A. Isayama, S. Kitajima, S. Masamune, K. Shinohara, P. S. Bawankar, E. Bernard, M. Von Berkel, H. Funaba, X. L. Huang, T. Ii, T. Ido, K. Ikeda, S. Kamio, R. Kumazawa, C. Moon, S. Muto, J. Miyazawa, T. Ming, Y. Nakamura, S. Nishimura, K. Ogawa, T. Ozaki, T. Oishi, M. Ohno, S. Pandya, R. Seki, R. Sano, K. Saito, H. Sakaue, Y. Takemura, K. Tsumori, N. Tamura, H. Tanaka, K. Toi, B. Wieland, I. Yamada, R. Yasuhara, H. Zhang, O. Kaneko, A. Komori, Flow damping due to stochastization of the magnetic field, Nature communications, 10.1038/ncomms6816, 6, 2015.01, [URL], The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition from a nested magnetic flux surface to a stochastic magnetic field is observed when the magnetic shear at the rational surface decreases to 0.5 in the large helical device. This flow damping and resulting profile flattening are much stronger than expected from the Rechester-Rosenbluth model. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that the flow damping is due to the change in the non-diffusive term of momentum transport..
89. Kishore Mishra, Y. Hayashi, M. Hamasaki, Y. Maeda, R. Akimoto, T. Onchi, A. Kuzmin, H. Idei, H. Zushi, Role of magnetic field curvature and strength on spontaneous rotation of plasma in tokamak QUEST, Proc. of 16th Cross Straits symposium on Energy and Environmental Science and Technology , 2014.11.
90. Sudheer K. Jawla, Michael A. Shapiro, Hiroshi Idei, Richard J. Temkin, Determination of waveguide mode content using irradiance moments, 39th International Conference on Infrared, Millimeter and Terahertz Waves, IRMMW-THz 2014
2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014
, 10.1109/IRMMW-THz.2014.6956423, 2014.11, [URL], We present a novel method for calculating the linearly polarized mode contents in an overmoded corrugated waveguide. The proposed method is based on calculating the low order irradiance moments of the measured radiated intensity profiles at several distances from the waveguide aperture. The method is validated by the data measured from a 63.5 mm diameter corrugated waveguide at 170 GHz and a 19 mm diameter corrugated waveguide at 250 GHz..
91. Kishore Mishra, H. Idei, H. Zushi, K. Nagata, R. Akimoto, M. K. Yamamoto, K. Hanada, M. Hasegawa, K. Nakamura, A. Fujisawa, Y. Nagashima, S. Banerjee, T. Onchi, A. Kuzmin, Thermal imaging of plasma with a phased array antenna in QUEST, Review of Scientific Instruments, 10.1063/1.4889903, 85, 11, 2014.11, [URL], A thermal imaging system to measure plasma Electron Bernstein Emission (EBE) emanating from the mode conversion region in overdense plasma is discussed. Unlike conventional ECE/EBE imaging, this diagnostics does not employ any active mechanical scanning mirrors or focusing optics to scan for the emission cones in plasma. Instead, a standard 3 × 3 waveguide array antenna is used as a passive receiver to collect emission from plasma and imaging reconstruction is done by accurate measurements of phase and intensity of these signals by heterodyne detection technique. A broadband noise source simulating the EBE, is installed near the expected mode conversion region and its position is successfully reconstructed using phase array technique which is done in post processing..
92. T. Imai, T. Kariya, R. Minami, T. Numakura, T. Eguchi, T. Kato, Y. Endo, M. Ichimura, T. Shimozuma, S. Kubo, H. Takahashi, Y. Yoshimura, H. Igami, S. Ito, T. Mutoh, K. Sakamoto, H. Idei, H. Zushi, K. Nagasaki, F. Sano, Development of Over 1 MW and Multi-Frequency Gyrotrons for Fusion, Proc. of the 25th IAEA Fusion Energy Conference (IAEA FEC 2014), FIP/2-2Rc, 2014.10.
93. T. Shimozuma, H. Igami, S. Kubo, Y. Yoshimura, H. Takahashi, M. Osakabe, T. Mutoh, M. Nishiura, H. Idei, K. Nagasaki, N. Marushchenko, Y. Turkin, Optimization of High Harmonic ECRH Scenario to Extend a Heating Plasma Parameter Range in LHD, Proc. of the 25th IAEA Fusion Energy Conference (IAEA FEC 2014), EX/P6-34, 2014.10.
94. K. Mishra, H. Zushi, H. Idei, M. Hasegawa, T. Onchi, S. Tashima, S. Banerjee, K. Hanada, K. Nakamura, A. Kuzmin, A. Fujisawa, Y. Nagashima, Self Organization of High βp Plasma Equilibrium with an Inboard Poloidal Null Sustained by Fully non- inductive Current Drive in QUEST, Proc. of the 25th IAEA Fusion Energy Conference (IAEA FEC 2014), EX/P1-29, 2014.10.
95. H. Zushi, A. Kuzmin, I. Takagi, S. K. Sharma, M. Hasegawa, M. Kobayashi, Y. Hirooka, N. Yoshida, A. Rusinov, A. Inoue, H. Zhou, A. Fujisawa, K. Hanada, H. Idei, K. Nakamura, Y. Nagashima, K. Matsuoka, T. Onchi, S. Tashima, S. Banerjee, Determination of the system function for the particle circulation process using perturbation technique in QUEST, Proc. of the 25th IAEA Fusion Energy Conference (IAEA FEC 2014), EX/P1-38, 2014.10.
96. H. Idei, T. Kariya, T. Imai, K. Mishra, O. Wanatabe, H. Zushi, K. Hamada, T. Onchi, A. Ejiri, K. Nakamura, A. Fujisawa, Y. Nagashima, M. Hasegawa, K. Matsuoka, A. Fukuyama, S. Kubo, T. Shimozuma, M. Yoshikawa, M. Sakamoto, S. Kawasaki, Fully Non-inductive Current Drive Experiments using 28GHz and 8.2 GHz Electron Cyclotron Waves in QUEST, Proc. of the 25th IAEA Fusion Energy Conference (IAEA FEC 2014), EX/P1-38, 2014.10.
97. Jawla, Sudheer K.; Shapiro, Michael A.; Idei, Hiroshi; Temkin, Richard J., Corrugated Waveguide Mode Content Analysis Using Irradiance Moments, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2014.2349797, 42, 10, 3358-3364, 2014.10.
98. K. Hanada, N. Yoshida, H. Zushi, K. Nakamura, A. Fujisawa, H. Idei, Y. Nagashima, H. Watanabe, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, O. Watanabe, Y. Takase, A. Fukuyama, O. Mitarai, M. Peng and the QUEST team , Investigation of progression from low to high hydrogen recycling during long duration discharges on a spherical tokamak, QUEST, Proc.25th Fusion Energy Conference (FEC 2014), 2014.10.13-18, St. Petersburg Russian Federation, EX/P1-37, 2014.10, Progression from low (LR) to high recycling (HR) was observed in full non-inductive long duration discharges up to 12 minutes on QUEST. Repetitive transition between LR and HR was induced by periodic gas puffing and the period to recover to LR, rec, was gradually prolonged with the plasma duration. The period, rec, normalized by gas rate has a linear relation to time-integrated H. This indicates hydrogen recycling induced an intentional gas puffing is increasing with time-integrated H which an indicator of hydrogen (H) fluence to the wall. To understand the dependence, deuterium (D) storing capability of the specimen exposed to QUEST plasmas was investigated by implantation of D2+
ions of 1keV and subsequent thermal desorption spectroscopy (TDS) as a post-mortem analysis. A diffusion-trap model, reconstructing the obtained the results of TDS, shows a clear dependence of recycling ratio on fluence and a time evolution of wall-stored H can be reconstructed. The model calculation indicates surface recombination on the deposition layer plays an essential role in QUEST wall behaviour. Wall temperature dependence on the number of injected H to keep density is experimentally investigated and is agreed with the model calculation. This result is quite helpful to execute hot wall experiments on QUEST..
99. M.Hasegawa, K.Nakamura, H.Zushi, K.Hanada, A.Fujisawa, K.Matsuoka, H.Idei, Y.Nagashima, K.Tokunaga, S.Kawasaki, H.Nakashima, A.Higashijima, Development of a plasma control system for steady-state operation on QUEST, JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 10.3938/jkps.65.1191, 65, 8, 1191-1195, 2014.10.
100. Jawla, Sudheer K. ; Shapiro, Michael A. ; Idei, Hiroshi ; Temkin, Richard J. , Determination of waveguide mode content using irradiance moments, Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2014 39th International Conference on, 1.0-2.0, 2014.09.
101. Ishiguro, Masaki; Hanada, Kazuaki; Liu, Hiqing; Ogata, Ryota; Isobe, Mitsutaka; Tashima, Saya; Zushi, Hideki; Sato, Khonosuke; Fujisawa, Akihide; Nakamura, Kazuo; Idei, Hiroshi; Sakamoto, Mizuki; Hasegawa, Makoto; Takase, Yuichi; Maekawa, Takashi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Investigation of Non-inductive Plasma Current Start-up by RF on QUEST, 15TH INTERNATIONAL CONGRESS ON PLASMA PHYSICS (ICPP2010) & 13TH LATIN AMERICAN WORKSHOP ON PLASMA PHYSICS (LAWPP2010), 10.1088/1742-6596/511/1/012041, 511.0, 0.0, 0.0-0.0, Article No. 012041, 2014.09, Formations of a closed flux surface (CFS) on QUEST are achieved by fully non-inductive current start-up driven by RF, which is 8.2GHz in frequency and more than 40kW in power. It found that appropriate magnetic configuration with positive n-index and reduction of particle recycling was crucial to achieve the non-inductive plasma current start-up (PCS) successfully. Especially the controllability of particle recycling should be improved by wall conditioning based on successive plasma production and wall cleaning with electron cyclotron resonance heating (ECR) plasmas induced by RF in frequency of 2.45GHz..
102. Nakamura, Kazuo; Fujita, H.; Liu, X. L.; Xue, E. B.; Xia, Fan; Mitarai, Osamu; Kurihara, Kenichi; Kawamata, Y.; Sueoka, M.; Hasegawa, Makoto; Tokunaga, Kazutoshi; Zushi, H.; Hanada, K.; Fujisawa, A.; Matsuoka, K.; Idei, H.; Nagashima, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Araki, Kuniaki; Fukuyama, A., Shape Reconstruction of RF-Driven Divertor Plasma on QUEST, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2014.2341616, 42.0, 9.0, 2309.0-2312.0, 0.0, 2014.09, In the present RF-driven plasma with a lot of high-energy electrons, there may be anisotropic plasma pressure, which makes the usual equilibrium analysis difficult, but the Cauchy condition surface method can reconstruct the plasma shape precisely regardless of the anisotropy. In addition, the plasma current effect in the open magnetic surfaces outside of the closed magnetic surfaces is considered in the RF-driven divertor plasma. In the reconstruction process, singular value (SV) decomposition is used and optimal criterion function for generalized cross validation is estimated concerning truncation or reduction of the small-SV components..
103. Kishore Mishra, Hiroshi Idei, hideki zushi, K. Nagata, R. Akimoto, M. K. Yamamoto, Kazuaki Hanada, makoto hasegawa, Kazuo Nakamura, Akihide Fujisawa, Yoshihiko Nagashima, S. Banerjee, 恩地 拓己, KUZMIN ARSENIY ALEKSANDROVI, Thermal imaging of plasma with a phased array antenna in QUEST, REVIEW OF SCIENTIFIC INSTRUMENTS, 85.0, Article No. 11E808-4, 2014.07.
104. Kishore MISHRA, Hideki ZUSHI, Hiroshi IDEI, Saya TASHIMA, Santanu BANERJEE, Makoto HASEGAWA, Kazuaki HANADA, Kazuo NAKAMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Keisuke MATSUOKA, Arseny KUZMIN, Takumi ONCHI and QUEST Team, Analytical Solution of High βp Equilibria with Natural Inboard Poloidal Null Configuration Obtained in the Spherical Tokamak QUEST, Plasma and Fusion Research, 10.1585/pfr.9.3402093, 9.0, RC, 5.0, Article No. 3402093, 2014.07, High βp (εβp ∼ 1) equilibria obtained in a ECW heated Ohmic plasma is investigated using a simple analytic solution of Grad-Shafranov equation. The formation of a natural inboard poloidal null associated with high βp is explained consistently by high diamagnetism and negative triangularity. As βp is increased, the poloidal null point penetrates further into the vacuum vessel, which is qualitatively explained by the analytic model. Transition from inboard (high field side) limiter bound to the natural divertor configuration is associated with a reduction of the edge safety factor without appreciable enhancement of MHD activities. Such a scenario is also addressed successfully with the model..
105. Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Ishiguro, M.; Tashima, S.; Liu, H. Q.; Mishra, K.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K., Role of stochasticity in turbulence and convective intermittent transport at the scrape off layer of Ohmic plasma in QUEST, PHYSICS OF PLASMAS, 10.1063/1.4890359, 21.0, 7.0, 0.0-0.0, 072311, 2014.07, Statistical features of fluctuations are investigated using the fast camera imaging technique in the scrape of layer (SOL) of electron cyclotron resonance heated Ohmic plasma. Fluctuations in the SOL towards low field side are dominated by coherent convective structures (blobs). Two dimensional structures of the higher order moments (skewness s and kurtosis k) representing the shape of probability density function (PDF) are studied. s and k are seen to be functions of the magnetic field lines. s and k are consistently higher towards the bottom half of the vessel in the SOL showing the blob trajectory along the field lines from the top towards bottom of the vessel. Parabolic relation (k = As-2 + C) is observed between s and k near the plasma boundary, featuring steep density gradient region and at the far SOL. The coefficient A, obtained experimentally, indicates a shift of prominence from pure drift-wave instabilities towards fully developed turbulence. Numerical coefficients characterizing the Pearson system are derived which demonstrates the progressive deviation of the PDF from Gaussian towards gamma from the density gradient region, towards the far SOL. Based on a simple stochastic differential equation, a direct correspondence between the multiplicative noise amplitude, increased intermittency, and hence change in PDF is discussed. (C) 2014 AIP Publishing LLC..
106. S.Banerjee, H.Zushi, N.Nishino, Y.Mahira, K.Nagaoka, K.Mishra, S.Tashima, Y.Nagashima, K.Hanada, K.Nakamura, H. Idei, M.Hasegawa, A.Fujisawa, K.Matsuoka, Scrape Off Layer Flow Characteristics in the Spherical Tokamak QUEST, JPS Conf. Proc. 1, 01536, 2014.07.
107. Idei, H; Nagata, K; Mishra, K; Yamamoto, MK; Itado, T; Akimoto, R; Hanada, K; Zushi, H; , Adaptive array technique for differential-phase reflectometry in QUEST, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.4891710, 85.0, 11.0, 5.0, Article No. 11D842, 2014.06, A Phased Array Antenna (PAA) was considered as launching and receiving antennae in reflectometry to attain good directivity in its applied microwave range. A well-focused beam was obtained in a launching antenna application, and differential-phase evolution was properly measured by using a metal reflector plate in the proof-of-principle experiment at low power test facilities. Differential-phase evolution was also evaluated by using the PAA in the Q-shu University Experiment with Steady State Spherical Tokamak (QUEST). A beam-forming technique was applied in receiving phased-array antenna measurements. In the QUEST device that should be considered as a large oversized cavity, standing wave effect was significantly observed with perturbed phase evolution. A new approach using derivative of measured field on propagating wavenumber was proposed to eliminate the standing wave effect..
108. H. Igami, S. Kubo, T. Shimozuma, Y. Yoshimura, H. Takahashi, M. Nishiura, S. Ogasawara, R. Makino, H. Idei, K. Nagasaki, T. Seki, M. Osakabe and T. Mutoh, Electron Bernstein wave heating and emission measurement through the very narrow OXB mode conversion window in the LHD, RADIOFREQUENCY POWER IN PLASMAS: Proceedings of the 20th Topical Conference. AIP Publishing,, 1580.0, 1.0, 490.0-493.0, 2014. p. 490-493., 2014.05.
109. K.Mishra, H.Idei, H.Zushi, S.Tashima, S.Banergee, M.Hasegawa, K.Hanada, K.Nakamura, A.Fujisawa, K.Matsuoka, Y.Nagashima, S.Kawasaki, H.Nakashima, A.Higashijima, Characteristics of High Poloidal Beta Plasma Formed by Electron Cyclotron Waves in Spherical Tokamak QUEST, JPS Conf. Proc.1, dx.doi.org/10.7566/JPSCP.1.015031, 015031, 2014.05.
110. Tashima, Saya; Zushi, H.; Isobe, M.; Hanada, K.; Idei, H.; Nakamura, K.; Fujisawa, A.; Matsuoka, K.; Hasegawa, M.; Nagashima, Y.; Okamura, S.; Banerjee, S.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Role of energetic electrons during current ramp-up and production of high poloidal beta plasma in non-inductive current drive on QUEST, NUCLEAR FUSION, 10.1088/0029-5515/54/2/023010, 54.0, 2.0, 0.0-0.0, 023010, 2014.02, A scenario for non-inductive current ramp-up has been demonstrated using electron cyclotron waves in the spherical tokamak QUEST. The configuration was characterized by a high toroidal magnetic mirror ratio of 2 and a steady vertical magnetic field of more than 10% of the toroidal magnetic field. The generation and confinement of energetic electrons having energy greater than 10 keV were studied using hard x-rays. Because of the energetic electron pressure, a natural divertor formed with an inboard poloidal field null at the high poloidal beta (approximately 3-4)..
111. H. Igami, S. Kubo, T. Shimozuma, Y. Yoshimura, H. Takahashi, M. Nishiura, S. Ogasawara, R. Makino, Hiroshi Idei, K. Nagasaki, T. Seki, M. Osakabe, T. Mutoh, Electron Bernstein wave heating and emission measurement through the very narrow O-X-B mode conversion window in the LHD, 20th Topical Conference on Radiofrequency Power in Plasmas
Radiofrequency Power in Plasmas - Proceedings of the 20th Topical Conference
, 10.1063/1.4864595, 1580, 490-493, 2014.01, [URL], In the large helical device (LHD), the theoretically predicted width of the ordinary-extraordinary-electron Bernstein wave (O-X-B) mode conversion (MC) window is comparable to the beam width and the power deposition is located in the off-axis region if the 77GHz fundamental electron cyclotron (EC) wave of is launched from an existing horizontal port antenna. In the experiment, the actual MC window location was looked for with changing the aiming. The effective aiming with that the increase of the stored energy was observed was two degrees apart from the location of the theoretical MC window at a maximum. Measurement of the waves originated from the thermally emitted EBW and radiated via the B-X-O mode conversion process is effective to improve the accuracy of the theoretical prediction with comparison between the theoretical and the experimental results. The theoretical prediction suggests that the width of the MC window of the fundamental 77GHz EC wave can be expanded if the lower port antenna is used. On the other hand, the MC window of the second harmonic 154GHz EC wave is blocked by horizontal port wall if another horizontal port antenna is used. It is required to move the final mirror of the quasi-optical antenna toward the plasma surface. Focusing of the beam at the plasma cutoff is (PC) also necessary for the effective mode conversion..
112. SAKAGUCHI, Masatsugu; IDEI, Hiroshi; SAITO, Tetsuji; SHIGEMATSU, Takashi; , Development of Full D-Band Corrugated Horn Antenna for ECRH System, Plasma and Fusion Research, 8.0, RA, Article No. 1405163, 2013.12.
113. B. Plaum, W. Kasparek, C. Lechte, J. Ruiz, H. Idei, D. Tretiak, Z. Popovic, In-situ real-time characterization of spurious modes in HE11 transmission lines with a mitrebend hole coupler, 2013 38th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2013
2013 38th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2013
, 10.1109/IRMMW-THz.2013.6665625, 2013.12, [URL], A method for the in-situ characterization of spurious modes in high power microwave transmission lines is presented. It uses hole couplers, which are integrated into a mitre-bend. The signals are proportional to the field strength at the mirror and allow to partly reconstruct the mode spectrum in the waveguide. The theoretical background is presented as well as results from measurements on prototypes..
114. Kazuo Nakamura, H. Fujita, X. L. Liu, E. B. Xue, F. Xia, O. Mitarai, K. Kurihara, Y. Kawamata, M. Sueoka, Makoto Hasegawa, Kazutoshi Tokunaga, H. Zushi, Kazuaki Hanada, akihide fujisawa, K. Matsuoka, Hiroshi Idei, Yoshihiko Nagashima, S. Kawasaki, H. Nakashima, A. Higashijima, K. Araki, A. Fukuyama, Shape reconstruction of RF-driven divertor plasma on QUEST, 2013 IEEE 25th Symposium on Fusion Engineering, SOFE 2013
2013 IEEE 25th Symposium on Fusion Engineering, SOFE 2013
, 10.1109/SOFE.2013.6635507, 2013.12, [URL], In the present RF-driven plasma with a lot of high-energy electrons, there may be anisotropic plasma pressure, which makes difficult a usual equilibrium analysis, but the CCS method can reconstruct the plasma shape precisely regardless of the anisotropy. And the plasma current effect in the open magnetic surfaces outside of the closed magnetic surfaces is considered in the RF-driven plasma. Further high-energy particle guiding center orbits are calculated aiming at estimation of the open-magnetic-surface current distribution..
115. Hasegawa, M.; Nakamura, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Matsuoka, K.; Mitarai, O.; Idei, H.; Nagashima, Y.; Tokunaga, K.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Development of plasma control system for divertor configuration on QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2013.03.035, 88.0, 6.0, 1074.0-1077.0, 0.0, 2013.10, A plasma control system to sustain divertor configurations is developed on QUEST (Q-shu university experiment with steady-state spherical tokamak). Magnetic fluxes are numerically integrated at 100 kHz using FPGA (Field-Programmable Gate Array) modules and transferred to a main calculation loop at 4 kHz. With these signals, plasma shapes are identified in real time at 2 kHz under the assumption that the plasma current can be represented as one filament current. This calculation is done in another calculation loop in parallel by taking advantage of a multi-core processor of the plasma control system. The inside and outside plasma edge positions are controlled to their target positions using PID (proportional-integral-derivative) control loops. Whereas the outside edge position can not be controlled by the outer PF coil current, the inside edge position can be controlled by the inner PF coil current. (C) 2013 Elsevier B.V. All rights reserved..
116. Kaneko, O.; Yamada, H.; Inagaki, S.; Jakubowski, M.; Kajita, S.; Kitajima, S.; Kobayashi; Koga, K.; Morisaki, T.; Morita, S.; Mutoh, T.; Sakakibara, S.; Suzuki, Y.; Takahashi, H.; Tanaka, K.; Toi, K.; Yoshimura, Y.; Akiyama, T.; Asahi, Y.; Ashikawa, N.; Chikaraishi, H.; Cooper, A.; Darrow, D. S.; Drapiko, E.; Drewelow, P.; Du, X.; Ejiri, A.; Emoto, M.; Evans, T.; Ezumi, N.; Fujii, K.; Fukuda, T.; Funaba, H.; Furukawa, M.; Gates, D. A.; Goto, M.; Goto, T.; Guttenfelder, W.; Hamaguchi, S.; Hasuo, M.; Hino, T.; Hirooka, Y.; Ichiguchi, K.; Ida, K.; Idei, H.; Ido, T.; Igami, H.; Ikeda, K.; Imagawa, S.; Imai, T.; Isobe, M.; Itagaki, M.; Ito, T.; Itoh, K.; Itoh, S.; Iwamoto, A.; Kamiya, K.; Kariya, T.; Kasahara, H.; Kasuya, N.; Kato, D.; Kato, T.; Kawahata, K.; Koike, F.; Kubo, S.; Kumazawa, R.; Kuwahara, D.; Lazerson, S.; Lee, H.; Masuzaki, S.; Matsuoka, S.; Matsuura, H.; Matsuyama, A.; Michael, C.; Mikkelsen, D.; Mitarai, O.; Mito, T.; Miyazawa, J.; Motojima, G.; Mukai, K.; Murakami, A.; Murakami, I.; Murakami, S.; Muroga, T.; Muto, S.; Nagaoka, K.; Nagasaki, K.; Nagayama, Y.; Nakajima, N.; Nakamura, H.; Nakamura, Y.; Nakanishi, H.; Nakano, H.; Nakano, T.; Narihara, K.; Narushima, Y.; Nishimura, K.; Nishimura, S.; Nishiura, M.; Nunami, Y. M.; Obana, T.; Ogawa, K.; Ohdachi, S.; Ohno, N.; Ohyabu, N.; Oishi, T.; Okamoto, M.; Okamoto, A.; Osakabe, M.; Oya, Y.; Ozaki, T.; Pablant, N.; Peterson, B. J.; Sagara, A.; Saito, K.; Sakamoto, R.; Sakaue, H.; Sasao, M.; Sato, K.; Sato, M.; Sawada, K.; Seki, R.; Seki, T.; Sergeev, V.; Sharapov, S.; Sharov, I.; Shimizu, A.; Shimozuma, T.; Shiratani, M.; Shoji, M.; Sudo, S.; Sugama, H.; Suzuki, C.; Takahata, K.; Takeiri, Y.; Takemura, Y.; Takeuchi, M.; Tamura, H.; Tamura, N.; Tanaka, H.; Tanaka, T.; Tingfeng, M.; Todo, Y.; Tokitani, M.; Tokunaga, K.; Tokuzawa, T.; Tsuchiya, H.; Tsumori, K.; Ueda, Y.; Vyacheslavov, L.; Watanabe, K. Y.; Watanabe, T.; Watanabe, T. H.; Wieland, B.; Yamada, I.; Yamada, S.; Yamamoto, S.; Yanagi, N.; Yasuhara, R.; Yokoyama, M.; Yoshida, N.; Yoshimura, S.; Yoshinaga, T.; Yoshinuma, M.; Komori, A., Extension of operation regimes and investigation of three-dimensional currentless plasmas in the Large Helical Device, NUCLEAR FUSION, 10.1088/0029-5515/53/10/104015, 53.0, 10.0, Article No. 104015, 2013.10, The progress of physical understanding as well as parameter improvement of net-current-free helical plasma is reported for the Large Helical Device since the last Fusion Energy Conference in Daejeon in 2010. The second low-energy neutral beam line was installed, and the central ion temperature has exceeded 7 keV, which was obtained by carbon pellet injection. Transport analysis of the high-T-i plasmas shows that the ion-thermal conductivity and viscosity decreased after the pellet injection although the improvement does not last long. The effort has been focused on the optimization of plasma edge conditions to extend the operation regime towards higher ion temperature and more stable high density and high beta. For this purpose a portion of the open helical divertors are being modified to the baffle-structured closed ones aimed at active control of the edge plasma. It is compared with the open case that the neutral pressure in the closed helical divertor increased by ten times as predicted by modelling. Studies of physics in a three-dimensional geometry are highlighted in the topics related to the response to a resonant magnetic perturbation at the plasma periphery such as edge-localized-mode mitigation and divertor detachment. Novel approaches of non-local and non-diffusive transport have also been advanced..
117. Plaum, B; Kasparek, W; Lechte, C; Ruiz, J; Idei, H; Tretiak, D; Popovic, Z; , In-situ real-time characterization of spurious modes in HE 11 transmission lines with a mitrebend hole coupler, Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on, Article No. 41641, 2013.09, A method for the in-situ characterization of spurious modes in high power microwave transmission lines is presented. It uses hole couplers, which are integrated into a mitre-bend. The signals are proportional to the field strength at the mirror and allow to partly reconstruct the mode spectrum in the waveguide. The theoretical background is presented as well as results from measurements on prototypes..
118. Santanu BANERJEE, Hideki ZUSHI, Nobuhiro NISHINO, Yoshihiko NAGASHIMA, Kazuaki HANADA, Saya TASHIMA, Tsubasa INOUE, Kazuo NAKAMURA, Hiroshi IDEI, Makoto HASEGAWA, Akihide FUJISAWA and Keisuke MATSUOKA, Turbulence Velocimetry of Tangential Fast Imaging Data on QUEST, Plasma and Fusion Research, 8.0, RA, 4.0, Article No. 2402098, 2013.08, A particle image velocimetry technique based on orthogonal dynamic programming is developed to measure the time resolved flow field of the fluctuating structures at the plasma edge and scrape off layer. This non-intrusive technique can provide two dimensional velocity fields at high spatial and temporal resolution from a fast framing image sequence and hence can provide better insights in plasma flow as compared to conventional probe measurements. Applicability of the technique is tested with simulated image pairs. Finally, it is applied to tangential fast visible images of QUEST as a test case to estimate the scrape off layer flow in Ohmic and ECRH driven plasma discharges..
119. Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Gao, X.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M., Cross-field motion of plasma blob-filaments and related particle flux in an open magnetic field line configuration on QUEST, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2013.01.106, 438.0, S513-S517, 2013.07, Blob-filaments have been observed by combined measurement with a fast camera and a movable Langmuir probe in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. Blob-filaments extended along field lines do correspond to over-dense plasma structures and propagated across the field lines to the outer wall. The radial velocity of the blob structure, Vb, was obtained by three methods and was dominantly driven by the E x B force. The radial velocity, size of the blob showed good agreements with the results obtained by sheath-connected interchange theoretical model. Vb corresponds to roughly 0.02-0.07 of the local sound speed (Cs) in QUEST. The higher moments (skewness S and kurtosis K) representing the shape of PDF of density fluctuation are studied. Their least squares fitting with quadratic polynomial is K = (1.60 +/- 0.27) S-2 - (0.46 +/- 0.20). The larger blob structures, occurring only 10% of the time, can carry more than 60% loss of the entire radial particle flux. (C) 2013 Elsevier B.V. All rights reserved..
120. Takashi SHIMOZUMA, Hiromi TAKAHASHI, Shin KUBO, Yasuo YOSHIMURA, Hiroe IGAMI, Masaki NISHIURA, Shinya OGASAWARA, Ryohei MAKINO, Hiroshi IDEI, Nikolai B MARUSHCHENKO, Yuri TURKIN and Takashi MUTOH, High Harmonic ECH Experiment for Extension of Heating Parameter Regime in LHD, Plasma and Fusion Research, 8.0, RA, Article No. 2402073, 2013.06, High harmonic electron cyclotron resonance heating (ECH) can extend the plasma heating region to higher density and higher β compared to the normal heating scenario. In this study, the heating characteristics of the second-harmonic ordinary (O2) and third-harmonic extraordinary (X3) modes and the possible extension of heating regime are experimentally confirmed. At the same time, a comparative study using ray-tracing calculation was performed in the realistic three-dimensional configuration of the Large Helical Device. The O2 mode heating showed a 40% absorption rate even above the X2 mode cut-off density. The X3 mode heating using powerful 77 GHz gyrotrons demonstrated an increase of about 40% in the central electron temperature in the plasmas at β-value of about 1%. These results were quantitatively explained to some extent by ray-tracing calculations..
121. Minami, R.; Kariya, T.; Imai, T.; Numakura, T.; Endo, Y.; Nakabayashi, H.; Eguchi, T.; Shimozuma, T.; Kubo, S.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Mutoh, T.; Ito, S.; Idei, H.; Zushi, H.; Yamaguchi, Y.; Sakamoto, K.; Mitsunaka, Y., Development of multi-purpose MW gyrotrons for fusion devices, NUCLEAR FUSION, 10.1088/0029-5515/53/6/063003, 53.0, 6.0, 0.0-0.0, UNSP 063003, 2013.06, The latest development achievements in the University of Tsukuba of over-1MW power level gyrotrons required in present-day fusion devices, GAMMA 10, Large Helical Device (LHD), QUEST, Heliotron J and NSTX, are presented. The obtained maximum outputs are 1.9MW for 0.1 s on the 77 GHz LHD tube and 1.2MW for 1ms on the 28 GHz GAMMA 10 one, which are new records in these frequency ranges. In long-pulse operation, 0.3 MW for 40 min at 77 GHz and 0.54 MW for 2 s at 28 GHz are achieved. A new programme of 154 GHz 1MW development has started for high-density plasma heating in LHD. On the first 154 GHz tube, 1.0MW for 1 s is achieved. As a next activity of the 28 GHz gyrotron, an over-1.5MW gyrotron is designed and fabricated to study the multi-MW oscillation. The possibility of 0.4MW continuous wave and 2MW level output in operations of a few seconds, after the improvements of output window and mode converter, is shown. Moreover, a new design study of dual-frequency gyrotron at 28 and 35 GHz has started, which indicates the practicability of the multi-purpose gyrotron..
122. Yoshimura, Y.; Igami, H.; Kubo, S.; Shimozuma, T.; Takahashi, H.; Nishiura, M.; Ohdachi, S.; Tanaka, K.; Ida, K.; Yoshinuma, M.; Suzuki, C.; Ogasawara, S.; Makino, R.; Idei, H.; Kumazawa, R.; Mutoh, T.; Yamada, H., Electron Bernstein wave heating by electron cyclotron wave injection from the high-field side in LHD, NUCLEAR FUSION, 10.1088/0029-5515/53/6/063004, 53.0, 6.0, UNSP 063004, 2013.06, In the Large Helical Device (LHD), evident electron Bernstein wave (EBW) heating was successfully performed. The experiment was carried out using the electron cyclotron heating (ECH) system that was upgraded by installation of high-power, long-pulse 77 GHz gyrotrons. The EBW heating was achieved by a mode conversion from injected EC wave to EBW, by the so-called slow-XB technique where an X-mode wave is injected to the plasma from the high magnetic field side. The specific magnetic configuration of LHD provides a good opportunity to realize the slow-XB technique, which is generally difficult for tokamaks. With the slow-XB technique, increases in kinetically evaluated electron energyWpe and electron temperature Te were observed in overdense plasmas. An electron heating in the so-called super dense core plasma in LHD, which is characterized with an internal diffusion barrier and a steep density gradient at the plasma core, was successfully demonstrated in the plasma core region where the central electron density n(e0) of 17 x 10(19) m(-3) was about 1.2 times higher, at the beginning of the EC-wave injection, than the left-hand cut-off density of applied 77 GHz EC waves..
123. Mutoh, T.; Seki, T.; Kumazawa, R.; Saito, K.; Kasahara, H.; Seki, R.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Nishiura, M.; Shoji, M.; Miyazawa, J.; Nakamura, Y.; Tokitani, M.; Ashikawa, N.; Masuzaki, S.; Idei, H.; Nomura, G.; Murakami, A.; Sakamoto, R.; Motojima, G.; Zhao, Y. P.; Kwak, J. G.; Takeiri, Y.; Yamada, H.; Kaneko, O.; Komori, A., Steady-state operation using a dipole mode ion cyclotron heating antenna and 77 GHz electron cyclotron heating in the Large Helical Device, NUCLEAR FUSION, 10.1088/0029-5515/53/6/063017, 53.0, 6.0, 0.0-0.0, UNSP 063017, 2013.06, The steady-state operation of high-performance plasmas in the Large Helical Device (LHD) has progressed since the 2010 IAEA Conference in Korea by means of a newly installed ion cyclotron heating (ICH) antenna (HAS antenna) and an improved electron cyclotron heating (ECH) system. The HAS antenna can control the launched parallel wave number and heat the core plasma efficiently in the case of dipole mode operation. Understanding of the physics and technology of wave heating, particle and heat flow balances, and plasma-wall interactions in LHD has also improved. The heating power of steady-state ICH and ECH exceeded 1MWand 500kW, respectively, and a higher density helium plasma with minority hydrogen ions was maintained using the HAS antenna and new 77 GHz gyrotrons. As a result, plasma performance improved, e. g. electron temperature of more than 2 keV at a density of more than 2 x 10(19) m(-3) became possible for more than 1 min. Heat flow balance and particle flux balance of steady-state operation were evaluated. Particle balance analysis indicated that externally fed helium and hydrogen particles were mainly absorbed by the chamber wall and divertor plates, even after the 54 min operation..
124. NAKAMURA Kazuo, FUJITA Hiroki, LIU Xiaolong, XUE Erbing, XIA Fan, MITARAI Osamu, KURIHARA Kenichi, KAWAMATA Yoichi, SUEOKA Michiharu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki, SHAPE RECONSTRUCTION OF RF-DRIVEN DIVERTOR PLASMA ON QUEST , Proc. Third Meeting for A3 Foresight Program Workshop on Critical Physics Issues Specific to Steady State Sustainment of High-Performance Plasmas,19-24 May 2013,Beijing,China,NIFS-PROC-95, 19-24 May 2013,Beijing,China,NIFS-PROC-95,48-55,2013.12., 2013.05.
125. Liu Xiaolong, Kazuo Nakamura, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Xue Erbing, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki, H∞ Loop Shaping Control for Plasma Vertical Position Instability on QUEST, PLASMA SCIENCE & TECHNOLOGY, 15.0, 3.0, 295.0, 2013.03, QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils (HCU and HCL) outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative (PD) controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does..
126. Masatsugu Sakaguchi, Hiroshi Idei, Tetsuji Saito, Takashi Shigematsu, Development of full D-band corrugated horn antenna for ecrh system, Plasma and Fusion Research, 10.1585/pfr.8.1405163, 8, 2013.01, [URL], The corrugated horn antenna is widely used for the evaluation of transmission lines in electron cyclotron resonant heating systems, but little is known about the intensity and phase of its radiation profile over a wide frequency range. This paper is concerned with the development of a full D-band (110 - 170 GHz) corrugated horn antenna. The antenna was designed based on electromagnetic simulation codes for the finite element method and the method of moment. To verify these numerical simulations, a low-power test system was established, and its dynamic power range was defined for the precise measurement of antenna radiation. The fabricated antenna was measured and analyzed with basic Gaussian optics for a number of frequencies throughout the D-band. The measured radiation profiles are Gaussian-like and agree well with the numerical simulations. The radiated intensity pattern is slightly elliptical in the lower frequency range, as unwanted higher-order modes arose at the corrugated mode conversion section and generated the elliptical radiation pattern. The evolutions of the antenna radiation do not correspond with those expected by basic Gaussian optics..
127. Xiaolong Liu, Kazuo Nakamura, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Erbing Xue, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki, H loop shaping control for plasma vertical position instability on QUEST, Plasma Science and Technology, 10.1088/1009-0630/15/3/21, 15, 3, 295-299, 2013.01, [URL], QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils (HCU and HCL) outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative (PD) controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does..
128. Takashi Shimozuma, Hiromi Takahashi, Shin Kubo, Yasuo Yoshimura, Hiroe Igami, Masaki Nishiura, Shinya Ogasawara, Ryohei Makino, Hiroshi Idei, Nikolai B. Marushchenko, Yuri Turkin, Takashi Mutoh, High harmonic ECH experiment for extension of heating parameter regime in LHD, Plasma and Fusion Research, 10.1585/pfr.8.2402073, 8, 2013.01, [URL], High harmonic electron cyclotron resonance heating (ECH) can extend the plasma heating region to higher density and higher β compared to the normal heating scenario. In this study, the heating characteristics of the second-harmonic ordinary (O2) and third-harmonic extraordinary (X3) modes and the possible extension of heating regime are experimentally confirmed. At the same time, a comparative study using ray-tracing calculation was performed in the realistic three-dimensional configuration of the Large Helical Device. The O2 mode heating showed a 40% absorption rate even above the X2 mode cut-off density. The X3 mode heating using powerful 77 GHz gyrotrons demonstrated an increase of about 40% in the central electron temperature in the plasmas at β-value of about 1%. These results were quantitatively explained to some extent by ray-tracing calculations..
129. , Saya Tashima, Hideki Zushi, Mitsutaka Isobe, Hiroshi Idei, Shoichi Okamura, Kazuaki Hanada, Kazuo Nakamura, Akihide Fujisawa, Keisuke Matsuoka, Makoto Hasegawa, Yoshihiko Nagashima, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Non-inductive current drive by EC waves in an inboard poloidal magnetic field null configuration on the spherical tokamak QUEST, Plasma and Fusion Research, 10.1585/pfr.8.2402118, 8, 2013.01, [URL], To investigate the effects of confinement of fast electrons on poloidal beta equilibrium, experiments under different toroidal magnetic mirror ratios, MOMFC, were performed in electron cyclotron heated plasma in the spherical tokamak QUEST. The proportional constants of the relation between plasma current and vertical magnetic fields decreased with increase in MOMFC. The poloidal field null point appeared in the chamber for MOMFC > 1.8 at a plasma current value of ~15 kA. Poloidal beta and temperature of hard X-rays increased with MOMFC. This suggests that high poloidal beta equilibrium plasma is produced by better confinement of energetic trapped particles..
130. Santanu Banerjee, Hideki Zushi, Nobuhiro Nishino, Yoshihiko Nagashima, Kazuaki Hanada, Saya Tashima, Tsubasa Inoue, Kazuo Nakamura, Hiroshi Idei, Makoto Hasegawa, Akihide Fujisawa, Keisuke Matsuoka, Turbulence velocimetry of tangential fast imaging data on QUEST, Plasma and Fusion Research, 10.1585/pfr.8.2402098, 8, 2013.01, [URL], A particle image velocimetry technique based on orthogonal dynamic programming is developed to measure the time resolved flow field of the fluctuating structures at the plasma edge and scrape off layer. This nonintrusive technique can provide two dimensional velocity fields at high spatial and temporal resolution from a fast framing image sequence and hence can provide better insights in plasma flow as compared to conventional probe measurements. Applicability of the technique is tested with simulated image pairs. Finally, it is applied to tangential fast visible images of QUEST as a test case to estimate the scrape off layer flow in Ohmic and ECRH driven plasma discharges..
131. Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Sharma, S. K.; Honma, H.; Tashima, S.; Inoue, T.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A., Statistical features of coherent structures at increasing magnetic field pitch investigated using fast imaging in QUEST, NUCLEAR FUSION, 10.1088/0029-5515/52/12/123016, 52.0, 12.0, 0.0-0.0, 123016, 2012.12, Fluctuations in slab plasma produced by electron cyclotron waves in an open magnetic configuration with vertical (B-z) and toroidal (B-t) fields are investigated as a function of B-z/B-t (field pitch) using a high speed visible camera in the spherical tokamak QUEST. Higher order moments (skewness s and kurtosis k) of spatio- temporal fluctuations are investigated. Background fluctuations, generation of coherent convective structures (blobs) and their propagation are analysed at the intensity gradient (R-im) and the source- free (essentially vacuum on the low- field side) regions, respectively. Parabolic relation (k = As-2 + C) is observed between s and k on the entire R- Z plane for a wide range of B-z/B-t. Progressive shift from the Gaussian statistics beyond R-im is observed with increasing B-z/B-t. From the moments of the probability density functions, possible location for blob generation is inferred to be R-im. Direct correspondence is observed with the prominence of the blobs and increase in stochastic forces with the increase in field pitch. Distribution of waiting time suggests that the blob generation may be a Poisson process. Accelerated cross field transport is observed for reasonably large-sized blobs..
132. Hiroshi Idei, Hideki Zushi, Kazuaki Hanada, Evgeniya Kalinnikova, Kazuo Nakamura, Akihide Fujisawa, Yoshihiko Nagashima, Makoto Hasegawa, Keisuke Matsuoka, Tsuyoshi Kariya, Tsuyoshi Imai, Ryutaro Minami, Naoaki Yoshida, Mizuki Sakamoto, Hideo Watanabe, Kazutoshi Tokunaga, Akira Ejiri, Masatsugu Sakaguchi, Masaki Ishiguro, Saya Tashima, Atsushi Fukuyama, Hiroe Igami, Shin Kubo, Mitsutaka Isobe, Kenichi Nagaoka, Hideya Nakanishi, Nobuhiro Nishino, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Yuichi Takase, Takashi Maekawa, Osamu Mitarai, Mitsuru Kikuchi, Kazuo Toi, ECW/EBW heating and current drive experiment results and prospects for CW operation in QUEST, Plasma and Fusion Research, 10.1585/pfr.7.2402112, 7, SPL.ISS.1, 2012.12, [URL], A CW phased-array antenna system for electron cyclotron/Bernstein wave heating and current drive (ECWH/CD, EBWH/CD) experiments was developed in the QUEST. The antenna was designed to excite an elliptically polarized pure O-mode wave in oblique injection for the O-X-B mode conversion scenario, and its good performance was confirmed at a high power level. Long pulse discharges with a plasma current of 10 kA and 15 kA were non-inductively attained for 37 s and 20 s, respectively, with only radio frequency (RF) power. Divertor configurationswere also obtained in the RF-sustained plasmas. A new operational window for sustained plasma current was observed in the high-density plasma with a higher RF incident power. Two new heating and current drive systems with an 8.56GHz klystron and a 28GHz gyrotron are being prepared to conduct CW EBWH/CD experiments in the high-density plasma..
133. Hiroe Igami, Shin Kubo, Takashi Shimozuma, Yasuo Yoshimura, Hiromi Takahashi, Hiroshi Idei, Masaki Nishiura, Shinya Ogasawara, Ryohei Makino, Ryuhei Kumazawa, Takashi Mutoh, Akio Sagara, Takuya Goto, Experimental results for electron Bernstein wave heating in the large helical device, Plasma and Fusion Research, 10.1585/pfr.7.2402110, 7, SPL.ISS.1, 2012.12, [URL], Electron cyclotron heating (ECH) using electron Bernstein waves (EBWs) was studied in the large helical device (LHD). Oblique launching of the slow extraordinary (SX-) mode from the high field side and oblique launching of the ordinary (O-) mode from the low field side were adopted to excite EBWs in the LHD by using electron cyclotron (EC) wave antennas installed apart from the plasma surface. Increases in the stored energy and electron temperature were observed for both cases of launching. These launching methods for ECH using EBWs (EBWH) is promising for high-density operation in future helical fusion devices instead of conventional ECH by normal electromagnetic modes..
134. B. Plaum, W. Kasparek, C. Lechte, J. Ruiz, D. Tretiak, H. Idei, In-situ characterization of spurious modes in HE11 transmission lines with a 5-port coupler, 17th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, EC 2011
EPJ Web of Conferences
, 10.1051/epjconf/20123204010, 32, 2012.12, [URL], Real-time in-situ measurement of spurious modes in HE11 transmission lines is becoming an important topic for the design of next-generation ECRH installations (e.g. ITER), because the acceptable tolerances for the alignment of the waveguides and coupling optics are small for oversized waveguides. Also, the effects of spurious modes (ohmic heating, wrong beam parameters at the launcher) become increasingly critical. We present a method for in-situ characterization of 4 dominant spurious modes by using a 5-port coupler, which is integrated into a miter bend. The coupler signals can be directly transformed into the mode spectrum by a matrix multiplication. A general formalism for obtaining the coefficients of the transformation matrix is presented along with a method for optimizing the coupler positions in order to obtain the maximum dynamic range for the diagnostics..
135. H. Igami, Y. Yoshimura, H. Takahashi, T. Shimozuma, S. Kubo, H. Idei, M. Nishiura, S. Ogasawara, R. Makino, S. Ohdachi, K. Ida, M. Yoshinuma, T. Ido, A. Shimizu, N. Tamura, S. Inagaki, T. Mutoh, Progress of ECRH by EBW in over-dense plasmas and controlling the confinement regime by ECCD with high power launching in LHD, 17th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, EC 2011
EPJ Web of Conferences
, 10.1051/epjconf/20123202006, 32, 2012.12, [URL], In the large helical device (LHD), fundamental electron cyclotron resonance heating (ECRH) by the electron Bernstein wave (EBW) excited via the ordinary-extraordinary-EBW (O-X-B) mode conversion process was performed with high power (∼1MW) launching. Profiles of increase of the electron temperature (Te) and the soft X-ray signals during the power injection suggest power absorption in the core region. Effects of the local modification of the rotational transform ι/2π(=1/q) by electron cyclotron current drive (ECCD) on the formation and sustainment of the electron internal transport barrier (e-ITB) was investigated for the first time. Co ECCD raised ι/2π close to 0.5 in the core region and caused the flattening of the Te profile. Additional ECRH power is required to form the e-ITB. On the contrary, counter (cntr.) ECCD separates ι/2π from 0.5 in the core region and avoids the flattening of the Te profile. The e-ITB can be formed and sustained without additional ECRH. Analysis of the heat pulse transport with use of the modulation ECRH (MECH) shows the good confinement region extends to the ι/2π =0.5 rational surface in the case of cntr. ECCD..
136. Masatsugu Sakaguchi, Hiroshi Idei, Shin Kubo, Tetsuji Saito, Takashi Shigematsu, Quasi-optical high purity HE11-mode exciter for oversized corrugated waveguide transmission, Plasma and Fusion Research, 10.1585/pfr.7.2405037, 7, SPL.ISS.1, 2012.12, [URL], Oversized corrugated waveguide transmissions are used to transmit high power millimeter wave for electron cyclotron heating in ITER. The HE11 mode purity of the waveguide components is a critical issue not only in the high power operation but also in the low power operation to evaluate the components. Conventional single Gaussian beam system causes edge diffraction and excites higher order modes at the waveguide aperture. A proposed HE11-mode exciter uses beam interference between two Gaussian beams interference and serves the high purity HE11 mode without the edge diffraction. The HE11-mode exciter consists of a scalar feed horn antenna, quasi-optical mirrors and a beam splitter (combiner). Phase matched mirrors correct the Gaussian-like beam excited from the horn antenna to pure Gaussian beam. Authors report the experimental study of the exciter..
137. S. Tashima, H. Zushi, M. Isobe, H. Idei, S. Okamura, K. Hanada, K. Nakamura, A. Fujisawa, K. Matsuoka, M. Hasegawa, Y. Nagashima, M. Ishiguro, S. Kawasaki, H. Nakashima, A. Higashijima, The role of energetic electrons on non-inductive current start-up and formation of an inboard poloidal field null configuration in the spherical tokamak QUEST, 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics
39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics
, 305-308, 2012.12.
138. H. Zushi; S. Tashima; M. Ishiguro; M. Hasegawa; S. Banerjee; N. Nishino; M. Isobe; K. Hanada; H. Idei; K. Nakamura; A. Fujisawa; Y. Nagashima; K. Matsuoka, S. K. Sharma; H. Liu; K. Toi; T. Maekawa; A. Ejiri; T. Yamaguchi;J. Hiratsuka; Y. Takase; M. Kikuchi; A. Fukuyama; Y. Ueda; O. Mitarai; S. Okamura;, Non-inductive current start-up and plasma equilibrium with an inboard poloidal field null by means of electron cyclotron waves in QUEST, Proc. 24th Int. Conf. on Fusion Energy (San Diego, CA, 2012), (※), 2012.10.
139. T. Mutoh, T. Seki, R. Kumazawa, K. Saito, H. Kasahara, R. Seki, S. Kubo, T. Shimozuma, Y. Yoshimura, H. Igami, H. Takahashi, M. Shoji, J. Miyazawa, M. Nishiura, Y. Nakamura, M. Tokitani, N. Ashikawa, S. Masuzaki, H. Idei, G. Nomura, A. Murakami, R. Sakamoto, G. Motojima, Y. P. Zhao, J. G. Kwak, Y. Takeiri, H. Yamada, O. kaneko, A. Komori and LHD Experiment group , Steady state operation using improved ICH and ECH for high performance plasma in LHD, 18th IAEA Fusion Energy Conference (Sorrento),IAEA-CN-77/OV5/3, EX/P2-12, 2012.10.
140. Banerjee, Santanu; Zushi, H.; Nishino, N.; Nagashima, Y.; Hanada, K.; Ishiguro, M.; Ryoukai, T.; Tashima, S.; Inoue, T.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Matsuoka, K., Fast visible imaging and edge turbulence analysis in QUEST, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.4739080, 83.0, 10.0, Article No. 10E524, 2012.10, A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024 x 1024 at 7000 frames/s (fps) and can achieve 775 kfps at a resolution of 128 x 24. In this paper, we present the salient features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma, without plasma current. Vertical magnetic field (B-z) topology is varied with three sets of poloidal field (PF) coils and the variation in the edge turbulence is investigated as a function of the B-z strength and curvature. Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739080].
141. Makoto Hasegawa, Kazuo Nakamura, Kazutoshi Tokunaga, Hideki Zushi, Kazuaki Hanada, akihide fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, A plasma shape identification with magnetic analysis for the real-time control on QUEST, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.132.477, 132, 7, 2012.10, [URL], In order to identify plasma shape, there is a way to represent the plasma current profile with several parameters, and adjust these parameters with least-square technique in order for calculated magnetic values to accord with measured ones. Here, the plasma shape parameters such as minor radius, elongation, and triangularity are chosen as the fitting parameters to represent plasma shape more directly, and the applicability to the control of the plasma shape are described by evaluating its calculation time. In order to find minimum of an objective function with least-square technique, two methods are compared, namely a linear approximation method and a downhill simplex method. While high accuracies of the measured magnetic signals are required, the good reproducibility is obtained, and the plasma shape identification can be done within several milliseconds in both methods..
142. Hiroshi Idei, Masatsugu Sakaguchi, Kazuya Nagata, Kazuaki Hanada, Hideki Zushi, Kazuo Nakamura, Makoto Hasegawa, Kohnosuke Sato, Mizuki Sakamoto, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Conceptual design and prototype performance of phased-array antenna for EBWH/CD experiments in QUEST, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.132.511, 132, 7, 511-516+9, 2012.10, [URL], Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments have been conducted to sustain a spherical tokamak configuration in a steady state in QUEST. In the EBWH/CD experiments on QUEST, the O-X-B mode conversion scenario was selected for plasma current sustainment in rather lowdensity plasmas. A new phased-array antenna system was proposed to launch a pure elliptically-polarized O-mode in the oblique injection. The prototype antenna system was designed and its performance was checked at low power test facilities. Good focusing and steering properties were confirmed in the low power test..
143. Evgeniya Kalinnikova, Hiroshi Idei, Hiroe Igami, Shin Kubo, Atsushi Fukuyama, Hideo Nuga, Hideki Zushi, Kazuaki Hanada, Modeling of OXB mode conversion scenario for EBWH/CD experiments in QUEST, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.132.505, 132, 7, 2012.10, [URL], The power deposition profiles were analyzed with a multiple ray tracing code for the Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments in QUEST. In the EBWH/CD experiments in QUEST, the OXB mode conversion scenario was selected for the plasma current sustainment in the rather low-density case. The algorithm for the wave penetration through evanescent layer beyond a O-mode cutoff position was developed for the multiple-ray analysis. The launching antenna positions were considered to obtain the significant wave absorption in the specific propagating direction for current drive experiments using the developed ray-tracing code..
144. Kazuaki Hanada, Hideki Zushi, Hiroshi Idei, Kazuo Nakamura, Masaki Ishiguro, Saya Tashima, Evgeniya Kalinnikova, Mizuki Sakamoto, Makoto Hasegawa, akihide fujisawa, Konosuke Sato, Naoaki Yoshida, Hideo Watanabe, Kazutoshi Tokunaga, Yoshihiko Nagashima, Aki Higashijima, Shoji Kawasaki, Hisatoshi Nakashima, Haiqing Liu, Osamu Mitarai, Takashi Maekawa, Atsushi Fukuyama, Yuichi Takase, Jinping Qian, QUEST experiments towards steady state operation of spherical tokamaks, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.132.490, 132, 7, 2012.10, [URL], Recent progress towards SSO of a spherical tokamak (ST) on QUEST is introduced. Zero-dimensional calculations of particle balance for QUEST experiment, refresh wall, and hot wall were performed showing that a SSO time of more than 1000s is required to obtain reliable results in regard to particle balance. Basic features of blobs were investigated in electron cyclotron resonance (ECR) heated plasmas. Formation and maintenance of a single-null divertor configuration was successfully obtained. Plasma duration in the divertor configuration was limited by out-gassing from a non-water-cooled first wall. Design studies for a hot wall are introduced..
145. Santanu Banerjee, Hideki Zushi, Nobuhiro Nishino, Kazuaki Hanada, Sanjeev Kumar Sharma, Tsubasa Inoue, Haiqing Liu, Masaki Ishiguro, Tomofumi Ryokai, Saya Tashima, Kazuo Nakamura, Hiroshi Idei, Makoto Hasegawa, Akihide Fujisawa, Keisuke Matsuoka, Statistical analysis of the convective intermittent transport at the edge region of QUEST, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.132.545, 132, 7, 545-554+16, 2012.10, [URL], Ambient fluctuations and the generation of coherent convective structures are investigated as a function of vertical to toroidal magnetic field ratio (B z/B t) in the spherical tokamak QUEST [K. Hanada et al., Plasma Fusion Research 5, S1007]. Fluctuation signals are obtained at a high spatial and temporal resolution using the fast visible camera. The coherent structures (blobs) were seen to be apparent only beyond a critical Bz/Bt ratio (∼ 10 -2). This clearly indicates a shift from the drift to the interchange mode with the increase in vertical magnetic field. The blobs are propagated radially at a high speed ∼ 10 3 m/s which is ∼ 1/10 th of the ion acoustic speed in QUEST. Lifetime of the blobs is about 700 μs. Second part of the study comprises of the investigation of the finer structures in the current ramp-up phase which is characterized by lower levels of fluctuations. Singular value decomposition (SVD) and principal component analysis (PCA) techniques are applied on the fast camera images to reveal the structures which are otherwise embedded in the overall intensity image. Electron banana orbits were seen to form from the slab annular plasma and grow wider to eventually shape the plasma current front..
146. H. Idei, H. Zushi, K. Hanada, E. Kalinnikova, M. Sakaguchi, T. Itado, K. Nakamura, A. Fujisawa, Y. Nagashima, M. Hasegawa, K. Matsuoka, A. Fukuyama, S. Tashima, H. Watanabe, N. Yoshida, K. Tokunaga, A. Ejiri, H. Igami, S. Kubo, K. Toi, M . Isobe, K. Nagaoka, H. Nakanishi, N. Nishino, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Ueda, M. Kikuchi, T. Fujita, O. Mitarai, T. Maekawa and Y. Takase, Electron Bernstein Wave Heating and Current Drive Effects in QUEST, FEC 2012: 24. IAEA Fusion Energy Conference; San Diego, CA (United States); 8-13 Oct 2012, 217.0, EX/P6-17, 2012.09.
147. Hiroe IGAMI, Shin KUBO, Takashi SHIMOZUMA, Yasuo YOSHIMURA, Hiromi TAKAHASHI, Idei Hiroshi, Masaki NISHIURA, Shinya OGASAWARA, Ryohei MAKINO, Ryuhei KUMAZAWA, Takashi MUTOH, Akio SAGARA, Takuya GOTO, Experimental Results for Electron Bernstein Wave Heating in the Large Helical Device, Plasma and Fusion Research, 7.0, RA, Article No. 2402110, 2012.09.
148. Igami, H; Yoshimura, Y; Takahashi, H; Shimozuma, T; Kubo, S; Idei, H; Nishiura, M; Ogasawara, S; Makino, R; Ohdachi, S; , Progress of ECRH by EBW in over-dense plasmas and controlling the confinement regime by ECCD with high power launching in LHD, EPJ Web of Conferences, 32.0, Article No. 02006, 2012.09.
149. Hiroshi IDEI, Hideki ZUSHI, Kazuaki HANADA, Evgeniya KALINNIKOVA, Kazuo NAKAMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Makoto HASEGAWA, Keisuke MATSUOKA, Tsuyoshi KARIYA, Tsuyoshi IMAI, Ryutaro MINAMI, Naoaki YOSHIDA, Mizuki SAKAMOTO, Hideo WATANABE, Kazutoshi TOKUNAGA, Akira EJIRI, Masatsugu SAKAGUCHI, Masaki ISHIGURO, Saya TASHIMA, Atsushi FUKUYAMA, Hiroe IGAMI, Shin KUBO, Mitsutaka ISOBE, Kenichi NAGAOKA, Hideya NAKANISHI, Nobuhiro NISHINO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA, Yuichi TAKASE, Takashi MAEKAWA, Osamu MITARAI, Mitsuru KIKUCHI and Kazuo TOI, ECW/EBW Heating and Current Drive Experiment Results and Prospects for CW Operation in QUEST, Plasma and Fusion Research, 7.0, RA, Article No. 2402112, 2012.09, A CW phased-array antenna system for electron cyclotron/Bernstein wave heating and current drive (ECWH/CD, EBWH/CD) experiments was developed in the QUEST. The antenna was designed to excite an elliptically polarized pure O-mode wave in oblique injection for the O-X-B mode conversion scenario, and its good performance was confirmed at a high power level. Long pulse discharges with a plasma current of 10 kA and 15 kA were non-inductively attained for 37 s and 20 s, respectively, with only radio frequency (RF) power. Divertor configurations were also obtained in the RF-sustained plasmas. A new operational window for sustained plasma current was observed in the high-density plasma with a higher RF incident power. Two new heating and current drive systems with an 8.56 GHz klystron and a 28 GHz gyrotron are being prepared to conduct CW EBWH/CD experiments in the high-density plasma..
150. TASHIMA, H ZUSHI, M ISOBE, H IDEI, S OKAMURA, K HANADA, K NAKAMURA, A FUJISAWA, K MATSUOKA, M HASEGAWA, Y NAGASHIMA, M ISHIGURO, S KAWASAKI, H NAKASHIMA, A HIGASHIJIMA, The role of energetic electrons on non-inductive current start-up and formation of an inboard poloidal field null configuration in the spherical tokamak QUEST, 39th EPS Conference & 16th Int. Congress on Plasma Physics, Vol.54 023010 , 2012.08.
151. Hiroshi Idei, Masatsugu Sakaguchi, Kazuya Nagata, Kazuaki Hanada, Hideki Zushi, Kazuo Nakamura, Makoto Hasegawa, Kohnosuke Sato, Mizuki Sakamoto, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Conceptual Design and Prototype Performance of Phased-array Antenna for EBWH/CD Experiments in QUEST, IEEJ Transactions on Fundamentals and Materials, 132.0, 7.0, 511.0-516.0, 2012.07, Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments have been conducted to sustain a spherical tokamak configuration in a steady state in QUEST. In the EBWH/CD experiments on QUEST, the O-X-B mode conversion scenario was selected for plasma current sustainment in rather low-density plasmas. A new phased-array antenna system was proposed to launch a pure elliptically-polarized O-mode in the oblique injection. The prototype antenna system was designed and its performance was checked at low power test facilities. Good focusing and steering properties were confirmed in the low power test..
152. B Plaum, W Kasparek, C Lechte, Juan Ruiz, D Tretiak, H Idei, In-situ characterization of spurious modes in HE11 transmission lines with a 5-port coupler, EPJ Web of Conferences, 32.0, Article No. 04010, 2012.07, Real-time in-situ measurement of spurious modes in HE11 transmission lines is becoming an important topic for the design of next-generation ECRH installations (e.g. ITER), because the acceptable tolerances for the alignment of the waveguides and coupling optics are small for oversized waveguides. Also, the effects of spurious modes (ohmic heating, wrong beam parameters at the launcher) become increasingly critical. We present a method for in-situ characterization of 4 dominant spurious modes by using a 5-port coupler, which is integrated into a miter bend. The coupler signals can be directly transformed into the mode spectrum by a matrix multiplication. A general formalism for obtaining the coefficients of the transformation matrix is presented along with a method for optimizing the coupler positions in order to obtain the maximum dynamic range for the diagnostics..
153. Kazuaki Hanada, Hideki Zushi, Hiroshi Idei, Kazuo Nakamura, Masaki Ishiguro, Saya Tashima, Evgeniya Kalinnikova, Mizuki Sakamoto, Makoto Hasegawa, Akihide Fujisawa, Konosuke Sato, Naoaki Yoshida, Hideo Watanabe, Kazutoshi Tokunaga, Yoshihiko Nagashima, Aki Higashijima, Shoji Kawasaki, Hisatoshi Nakashima, Haiqing Liu, Osamu Mitarai, Takashi Maekawa, Atsushi Fukuyama, Yuichi Takase, Jinping Qian, QUEST Experiments Towards Steady State Operation of Spherical Tokamaks, IEEJ Transactions on Fundamentals and Materials, 132.0, 7.0, 490.0-498.0, 2012.07, QUEST計画の大きな目標の一つは、高温プラズマの定常化にかかわる研究である。本論文は、論文は論文は発表時点での長時間維持についての報告(国際球状トカマクワークショップ:平成23年11月於核融合科学研究所)をまとめたものである。特に長時間運転での粒子バランスについてのポイントモデルを用いて、QUESTのパラメータを用いると粒子バランスの定常化に必要な時間が1018秒程度になることを示した。.
154. Santanu Banerjee, Hideki Zushi, Nobuhiro Nishino, Kazuaki Hanada, Sanjeev Kumar Sharma, Tsubasa Inoue, Haiqing Liu, Masaki Ishiguro, Tomofumi Ryokai, Saya Tashima, Kazuo Nakamura, Hiroshi Idei, Makoto Hasegawa, Akihide Fujisawa, Keisuke Matsuoka, Statistical Analysis of the Convective Intermittent Transport at the Edge Region of QUEST, IEEJ Transactions on Fundamentals and Materials, 132.0, 7.0, 545.0-554.0, 2012.07.
155. Makoto Hasegawa, Kazuo Nakamura, Kazutoshi Tokunaga, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, A Plasma Shape Identification with Magnetic Analysis for the Real-time Control on QUEST, IEEJ Transactions on Fundamentals and Materials, 132.0, 7.0, 477.0-484.0, 2012.07, In order to identify plasma shape, there is a way to represent the plasma current profile with several parameters, and adjust these parameters with least-square technique in order for calculated magnetic values to accord with measured ones. Here, the plasma shape parameters such as minor radius, elongation, and triangularity are chosen as the fitting parameters to represent plasma shape more directly, and the applicability to the control of the plasma shape are described by evaluating its calculation time. In order to find minimum of an objective function with least-square technique, two methods are compared, namely a linear approximation method and a downhill simplex method. While high accuracies of the measured magnetic signals are required, the good reproducibility is obtained, and the plasma shape identification can be done within several milliseconds in both methods..
156. Ishiguro, Masaki; Hanada, Kazuaki; Liu, Haiqing; Zushi, Hideki; Nakamura, Kazuo; Fujisawa, Akihide; Idei, Hiroshi; Nagashima, Yoshihiko; Hasegawa, Makoto; Tashima, Saya; Takase, Yuichi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Non-inductive current start-up assisted by energetic electrons in Q-shu University experiment with steady-state spherical tokamak, PHYSICS OF PLASMAS, 10.1063/1.4731700, 19.0, 6.0, Article No. 062508, 2012.06, After intensive discharge cleaning of the chamber wall, non-inductive current start-up experiments have been successfully performed in QUEST in moderate vertical fields of about 1.0-1.5mT with positive n-index. Simultaneously, with increasing plasma current, an asymmetric toroidal flow of energetic electrons was observed and direct measurements of current driven by this asymmetric flow were taken with a newly developed Langmuir probe technique. A numerical study of the energetic electron orbits indicates that the total current is enough to play a dominant role in the formation of a closed flux surface in QUEST. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731700].
157. Evgeniya KALINNIKOVA, Hiroshi IDEI, Hiroe IGAMI, Shin KUBO, Atsushi FUKUYAMA, HideoNUGA, Hideki ZUSHI, Kazuaki HANADA, Modeling of OXB mode conversion scenario for EBWH/CD Experiments in QUEST, IEEJ Transactions on Fundamentals and Materials, 132.0, 7.0, 505.0-510.0, 2012.05.
158. Ruiz, Juan; Kasparek, Walter; Lechte, Carsten; Plaum, Burkhard; Idei, Hiroshi, Numerical and experimental investigation of a 5-port mitre-bend directional coupler for mode analysis in corrugated waveguides, JOURNAL OF INFRARED MILLIMETER AND TERAHERTZ WAVES, 10.1007/s10762-012-9883-0, 33.0, 5.0, 491.0-504.0, 0.0, 2012.05, A directional coupler array with 5 ports integrated into a mitre bend for corrugated waveguide transmission lines at 140 GHz has been manufactured. The design is reviewed, and calculations on the performance for in-situ power measurement and mode discrimination are shown. Emphasis is given on detection of errors in alignment of the transmission system. Experimental tests are performed to benchmark the calculations. The results confirm the predictions and show that such a coupler is a viable tool for power measurement and basic mode analysis in high-power transmission systems..
159. Sakaguchi, Masatsugu; Idei, Hiroshi; Kubo, Shin; Saito, Tetsuji; Shigematsu, Takashi; , Quasi-Optical High Purity HE 11-Mode Exciter for Oversized Corrugated Waveguide Transmission, Plasma and Fusion Research, 7.0, ArticleNo. 2405037, 2012.01.
160. Sharma, S. K.; Zushi, H.; Yoshida, N.; Watanabe, H.; Osakabe, M.; Takeri, Y.; Hasegawa, M.; Tanabe, T.; Tokunaga, K.; Hanada, K.; Idei, H.; Sakamoto, M.; Nakamura, K.; Fujisawa, A.; Ishiguro, M.; Tashima, S., Analysis of PWI footprint traces and material damage on the first walls of the spherical tokamak QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2011.10.001, 87.0, 1.0, 77.0-86.0, 2012.01, After several non-inductive current startup experimental campaigns in the spherical tokamak QUEST, its metallic first walls have revealed various kinds of damages as a signature of strong plasma wall interaction (PWI). Several types of footprint traces, namely colored regions formed due to material erosion/redeposition, melting of plasma facing components (PFCs) and numerous arc tracks on the chamber walls are recognized. Analysis of the re-deposited materials on collector probes is carried out using Xray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Redeposition of several impurity materials such as carbon, oxygen and tungsten is identified. The footprint traces are majorly formed on the lower side PFCs, showing a large up/down asymmetry. Both toroidally symmetric and asymmetric footprint traces are formed on the bottoms side divertor plate and the lower part of the outboard side walls, respectively. Localized melting occurred on the outboard side limiters is attributed to the loss of energetic electrons produced via electron cyclotron resonance (ECR) heating. The observed damages are discussed in view of localized PWI, loss of energetic electrons, particle drifts, sputtering, arcing and redeposition of eroded materials. Material analysis and numerically calculated guiding center orbits of the charge particles are used to discuss these damages. (C) 2011 Elsevier B.V. All rights reserved..
161. Sharma, S. K.; Zushi, H.; Takagi, I.; Hisano, Y.; Shikama, T.; Morita, S.; Tanabe, T.; Yoshida, N.; Sakamoto, M.; Higashizono, Y.; Hanada, K.; Hasegawa, M.; Nakamura, K.; Idei, H.; Sato, K. N.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nakashima, Y.; Hatano, Y.; Sagara, A.; Nakamura, Y.; Ashikawa, N.; Maekawa, T.; Kishimoto, Y.; Takase, Y., Permeation measurements for investigating atomic hydrogen flux and wall pumping/fuelling dynamics in QUEST, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2011.09.026, 420.0, 13.0, 83.0-93.0, 2012.01, In order to investigate the overall atomic hydrogen background and the dynamic characteristics of wall pumping/fuelling phenomenon, a permeation probe system has been developed and applied in the spherical tokamak QUEST. Reliability of measurements, within +/- 3% accuracy and a positive correlation with the hydrogen line emission over three orders of magnitude have been demonstrated for more than 3000 various plasma discharges. By comparison of the experimental permeation (flux) curves with the numerically simulated curves, the net incident atomic hydrogen flux is evaluated in the range of 1 x 10(19) H m(-2) s(-1) 4 x 10(20) H m(-2) s(-1). The atomic flux has been investigated as a function of various plasma operation parameters like RF power, gas pressure and magnetic configuration. Using the static particle balance and permeation measurements, the progress in wall conditioning has been investigated. An inverse correlation between the atomic hydrogen flux and improvement in wall pumping has been observed over the two campaigns. (C) 2011 Elsevier B.V. All rights reserved..
162. Hiroshi Idei, M. Sakaguchi, K. Nagata, E. Kalinnikova, A. Fukuyama, H. Zushi, Kazuaki Hanada, Kazuo Nakamura, M. Sakamoto, Makoto Hasegawa, Y. Takase, T. Maekawa, O. Mitarai, S. Kawasaki, H. Nakashima, A. Higashijima, Development of CW 16-element phased-array antenna for electron bernstein wave heating and current drive experiments in QUEST, 36th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2011
IRMMW-THz 2011 - 36th International Conference on Infrared, Millimeter, and Terahertz Waves
, 10.1109/irmmw-THz.2011.6105070, 2011.12, [URL], The 16-element phased-array antenna has been developed for the EBWH/CD experiments. The 2-D k-spectra could be controlled. The heat load and stress were analyzed to be moderate in the 200kW CW operation. The symmetrically 2-D narrow-field distributions were excited by the developed antenna, indicating its good applicability to the EBWH/CD experiments..
163. H. Idei, H. Zushi, K. Hanada, K. Nakamura, A. Fujisawa, M. Hasegawa, N. Yoshida, M. Sakamoto, H. Watanebe, K. Tokunaga, Y. Nagashima, A. Ejiri, M. Sakaguchi, E. Kalinnikova, M. Ishiguro, S. Tashima, A. Fukuyama, H. Igami, S. Kubo, S. K. Sharma, T. Ryokai, H. Q. Liu, M. Isobe, K. Nagaoka, H. Nakanishi, N. Nishino, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai, M. Kikuchi, K. Toi, Electron Cyclotron / Bernstein wave heating and current drive experiments using phased-array antenna in QUEST, 19th Topical Conference on Radio Frequency Power in Plasmas
Radio Frequency Power in Plasmas - Proceedings of the 19th Topical Conference
, 10.1063/1.3665017, 473-476, 2011.12, [URL], The phased-array antenna system for Electron Cyclotron/Bernstein Wave Heating and Current Drive experiments has been developed in the QUEST. The antenna was designed to excite a pure O-mode wave in the oblique injection for the O-X-B mode conversion experiments, and its good performances were confirmed at a low power level. The plasma current (<∼15kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection in the low-density operations. The long pulse discharge of 10 kA was also attained for 37 s. The new density window to sustain the plasma current was observed in the high-density plasmas. The single-null divertor configuration with the high plasma current (<∼25kA) was attained in the 17 s plasma sustainment..
164. Osamu Mitarai, Kazuo Nakamura, Saya Tashima, Makoto Hasegawa, Hiroshi Idei, Mizuki Sakamoto, Kazuaki Hanada, Hideki Zushi, Kohnosuke Sato, Masaki Ishiguro, Hai Qing Liu, Yuta Higashizono, Aki Higashijima, Hisatoshi Nakashima, Shoji Kawasaki, Yuichi Takase, Takashi Maekawa, Nobuhiro Nishino, First ohmic discharge assisted with RF power in QUEST spherical tokamak, Plasma and Fusion Research, 10.1585/pfr.6.1402003, 6, 2011, 2011.12, [URL], Ohmic plasma currents of up to 17 kA with a discharge duration of 0.32 s have been obtained in the Kyushu University Experiment with Steady-State Spherical Tokamak (QUEST) with the help of electron cyclotron wave (ECW) and cancellation coils (CCs). The CCs, originally installed to create a field null in the plasma breakdown phase, are essential for producing plasma current in QUEST. Although the ohmic coil current is initially biased and then reduced completely to zero to induce the plasma current in 15-20 ms, we demonstrate that the flat top of the plasma current exceeding 20 ms is maintained by the vertical field after the ohmic current is switched off. This type of operation is quite favorable for extending pulsed operation to the steady state by electron Bernstein wave current drive (EBCD)..
165. Xiaolong Liu, Kazuo Nakamura, Yi Jiang, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki, Study of matrix converter as a current-controlled power supply in QUEST tokamak, Plasma and Fusion Research, 10.1585/pfr.6.2405137, 6, 1 SPECIAL ISSUE, 2011.12, [URL], Because QUEST tokamak has a divertor configuration with a higher κ and a negative n-index, a precise power supply with a rapid response is needed to control the vertical position of the plasma. A matrix converter is a direct power conversion device that uses an array of controlled bidirectional switches as the main power elements for creating a variable-output current system. This paper presents a novel three-phase to two-phase topological matrix converter as a proposed power supply that stabilizes the plasma vertical position and achieves unity input power factor. An indirect control strategy in which the matrix converter is split into a virtual rectifier stage and a virtual inverter stage is adopted. In the virtual rectifier stage, the instantaneous active power and reactive power are decoupled on the basis of system equations derived from the DQ transformation; hence, unity power factor is achieved. Space vector pulse width modulation is adopted to determine the switching time of each switch in the virtual rectifier; the output voltage of the virtual rectifier is adjusted by the virtual inverter stage to obtain the desired load current. Theoretical analyses and simulation results are provided to verify its feasibility..
166. H. Kasahara, K. Saito, T. Seki, R. G. Nomura, F. S.T. Shimozuma, H. Igami, T. Wakatsuki, H. Watada, Hiroshi Idei, S. Masuzaki, T. Mutoh, The impact of ICRF heating using newly installed phasing antenna in LHD, 38th EPS Conference on Plasma Physics 2011, EPS 2011
38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts
, 897-900, 2011.12.
167. Ishiguro, Masaki; Hanada, Kazuaki; Liu, Haiqing; Zushi, Hideki; Yoshida, Naoaki; Tokunaga, Tomonori; Nakamura, Kazuo; Fujisawa, Akihide; Idei, Hiroshi; Sakamoto, Mizuki; Hasegawa, Makoto; Tashima, Saya; Takase, Yuichi; Maekawa, Takashi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Direct measurement of energetic electron flow in Q-shu University experiment with steady-state spherical tokamak, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.3662204, 82.0, 11.0, Article No. 113509, 2011.11, In magnetized plasmas, the presence of a significant number of energetic electrons has been observed but quantitative characteristics of these electrons are proving difficult to investigate. A Langmuir probe offers a means to provide quantitative measurement of these energetic electrons that takes into account electron emissions (secondary electron emission and electron reflection) from the probe tips and sheath expansion around the probe tips caused by a considerable negative potential. In this paper, these effects are experimentally confirmed and an analytical means to measure energetic electron characteristics are proposed. An analysis of plasmas produced by a high frequency wave is then applied leading to the successful detection of an asymmetric flow of energetic electrons. The estimated electron temperature and current density were approximately 4-5 keV and 2-3 kA/m(2). (C) 2011 American Institute of Physics. [doi:10.1063/1.3662204].
168. Sharma, S. K.; Zushi, H.; Takagi, I.; Hisano, Y.; Shikama, T.; Morita, S.; Tanabe, T.; Yoshida, N.; Sakamoto, M.; Higashizono, Y.; Hanada, K.; Hasegawa, M.; Mitarai, O.; Nakamura, K.; Idei, H.; Sato, K. N.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nakashima, Y.; Nishino, N.; Hatano, Y.; Sagara, A.; Nakamura, Y.; Ashikawa, N.; Maekawa, T.; Kishimoto, Y.; Takase, Y., HYDROGEN PERMEATION MEASUREMENTS IN THE SPHERICAL TOKAMAK QUEST AND ITS NUMERICAL MODELING, FUSION SCIENCE AND TECHNOLOGY, 60.0, 4.0, 1511.0-1514.0, 0.0, 2011.11, A permeation measuring system with a nickel membrane of 30 ion thickness was installed near the mid plane of the spherical tokamak, QUEST Hydrogen permeation through the membrane heated at fix temperatures (422 - 506 K) was measured during short pulse (< 1 s) and long pulse (I hour) plasma discharges. After the membrane was heated to a required temperature, hydrogen plasma was discharged using a 2.45 GHz or 8.2 GHz RF system. Significant plasma-driven permeation was observed even for very short plasma discharges (e.g. 0.1s). Numerical calculations with the use of diffusion equation under recombination boundary conditions were conducted to simulate the transient permeation behavior. The numerical calculations were also used to estimate diffusion coefficient and recombination coefficients of membrane material. Temperature dependence of both the coefficients was explained by the Arrhenius law. A one hour long permeation curve was also numerically reproduced using the same set of parameters except an increasing recombination coefficient on the plasma side of the membrane..
169. Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Liu, H. Q.; Ishiguro, M.; Ryoukai, T.; Tashima, S.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A., Statistical Interpretation of the Density Fluctuations From the High-Speed Visible Images of Edge Turbulence on QUEST, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2011.2163423, 39.0, 11.0, 3006.0-3007.0, 0.0, 2011.11, Edge turbulence has been imaged on QUEST at high temporal resolution (50 kHz) using a fast framing visible camera. Statistical features of fluctuations including blobs are investigated in both open and closed magnetic configurations. Higher order moments of fluctuations including blobs and their mutual relationships are investigated. Close resemblance of the density pdf with Gaussian or beta distributions has earlier been predicted. Hence, an attempt has been made to characterize the density pdf with respect to the Pearson system to ascertain the implications of the stochastic forces..
170. S. K. Sharma, H. Zushi, I. Takagi, Y. Hisano, T. Shikama, S. Morita, T. Tanabe, N. Yoshida, M. Sakamoto, Y. Higashizono, K. Hanada, M. Hasegawa, O. Mitarai, K. Nakamura, H. Idei, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Nakashima, N. Nishino, Y. Hatano, A. Sagara, Y. Nakamura, N. Ashikawa, T. Maekawa, Y. Kishimoto, Y. Takase, Hydrogen permeation measurements in the spherical tokamak quest and its numerical modeling, Fusion Science and Technology, 10.13182/FST11-A12719, 60, 4, 1511-1514, 2011.11, [URL], A permeation measuring system with a nickel membrane of 30 pm thickness was installed near the mid plane of the spherical tokamak, QUEST. Hydrogen permeation through the membrane heated at fix temperatures (422 -506 K) was measured during short pulse (< 1 s) and long pulse (1 hour) plasma discharges. After the membrane was heated to a required temperature, hydrogen plasma was discharged using a 2.45 GHz or 8.2 GHzRF system. Significant plasma-driven permeation was observed even for very short plasma discharges (e.g. 0.1s). Numerical calculations with the use of diffusion equation under recombination boundary conditions were conducted to simulate the transient permeation behavior. The numerical calculations were also used to estimate diffusion coefficient and recombination coefficients of membrane material. Temperature dependence of both the coefficients was explained by the Arrhenius law. A one hour long permeation curve was also numerically reproduced using the same set of parameters except an increasing recombination coefficient on the plasma side of the membrane..
171. Nakamura, K.; Jiang, Y.; Liu, X. L.; Mitarai, O.; Kurihara, K.; Kawamata, Y.; Sueoka, M.; Hasegawa, M.; Tokunaga, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Sakamoto, M.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Araki, K., Eddy current-adjusted plasma shape reconstruction by Cauchy condition surface method on QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2011.04.045, 86.0, 6.0, 1080.0-1084.0, 2011.10, CCS (Cauchy Condition Surface) method is a numerical approach to reproduce plasma shape, which has good precision in conventional tokamaks. In order to apply it in plasma shape reproduction of ST (Spherical Tokamak). the calculation precision of the CCS method in a spherical tokamak CPD (Compact PWI experimental Device)(B(t) = 0.25 T, R = 0.3 m, a = 0.2 m) has been analyzed. The precision was confirmed also in ST and decided to be applied to a spherical tokamak QUEST (B(t), = 0.25 T, R = 0.68 m, a = 0.40 m).. In present stage from the magnetic measurement, it is known that the eddy current effect is large in QUEST experiment, and there are no special magnetic measurements for eddy current now, so some proper model should be selected to evaluate the eddy current effect. The eddy current density by not only CS (Center Solenoid) coil but also plasma current is calculated using EDDYCAL (JAEA). The eddy current magnitudes are taken as unknown variables and solved together with plasma shape reconstruction in ohmic discharge and ECCD (Electron Cyclotron Current Drive) discharge. (C) 2011 Elsevier B.V. All rights reserved..
172. Idei, H.; Sakaguchi, M.; Nagata, K.; Kalinnikova, E.; Fukuyama, A.; Zushi, H.; Hanada, K.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Development of CW 16-element Phased-array Antenna for Electron Bernstein Wave Heating and Current Drive Experiments in QUEST, 2011 36TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ), 2011.09, The 16-element phased-array antenna has been developed for the EBWH/CD experiments. The 2-D k-spectra could be controlled. The heat load and stress were analyzed to be moderate in the 200kW CW operation. The symmetrically 2-D narrow-field distributions were excited by the developed antenna, indicating its good applicability to the EBWH/CD experiments..
173. Ogata, R.; Hanada, K.; Nishino, N.; Liu, H. Q.; Zushi, H.; Ishiguro, M.; Ikeda, T.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak, PHYSICS OF PLASMAS, 10.1063/1.3640494, 18.0, 9.0, 0.0-0.0, Article No. 092306, 2011.09, A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3640494].
174. Igami, Hiroe; Idei, Hiroshi; Kubo, Shin; Yoshimura, Yasuo; Shimozuma, Takashi; Takahashi, Hiromi, Measurement of the Electron Bernstein Wave Emission with One of the Power Transmission Lines for ECH in LHD, PLASMA SCIENCE & TECHNOLOGY, 10.1088/1009-0630/13/4/04, 13.0, 4.0, 405.0-409.0, 0.0, 2011.08, Possibility of the measurement of radiated waves derived from the thermally emitted electron Bernstein wave (EBW) is numerically investigated based on the assumption of the super dense core (SDC) plasma generated in LHD. EBW that is thermally emitted in the electron cyclotron resonance (ECR) layer may couple with the electromagnetic wave and be emitted to the vacuum via the EBW-extraordinary-ordinary (B-X-O) mode conversion process. We consider the use of one of the transmission lines for electron cyclotron heating (ECH) in LHD as a receiving system of the emission. It is derived that the waves in the fundamental cyclotron frequency range are emitted as the EBW near their upper hybrid resonance (UHR) layer outside the last close flux surface (LCFS). On the other hand, waves in the second harmonics cyclotron frequency range are emitted in the core region. It means that successful measurement of waves of the second harmonic frequency range emitted from extremely high dense core plasma with setting an aim angle for receiving indicates a possibility of the second harmonic ECH by EBW in the core region with setting the same aim angle and the same polarization for launching..
175. Hanada, K.; Sasaki, K.; Zushi, H.; Nakamura, K.; Sato, K. N.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Metallic dusts behavior in all-metal first wall on TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2010.11.017, 415.0, 1.0, S1123-S1126, 2011.08, Metallic dust behavior was observed in full lower hybrid current drive plasmas on TRIAM-1M, which had all-metal plasma facing components. TRIAM-1M was shut-down on December 2005 and then in-vessel dusts were collected with a suction aspirator through a membrane filter of 100 nm meshes. The toroidal distribution of the total mass of collected in-vessel dusts was measured and the largest amount was found to be near the vertical movable limiter (VML). The typical size of in-vessel dusts was 1-10 mu m and the impact on augmenting the surface area was not significant. Dusts were observed to be either flaky or spherical in form and the majority of the flakes had accumulated around the VML Eruption detritus were observed on the surface of large flakes and this suggests that the burst of blistering are one of the origins of in-vessel dusts. (C) 2010 Elsevier B.V. All rights reserved..
176. Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Fujisawa, A.; Hasegawa, M.; Higashizono, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Study of blob-like structures in QUEST, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2010.12.225, 415.0, 1.0, S620-S623, 2011.08, Blob-like structures are observed in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. The combined measurement with a fast camera and a movable Langmuir probe show that visible filamentary structures extended along field lines do correspond to over-dense plasma structures. Ion saturation current time trace shows a front-like asymmetric burst when a visible structure reaches the probe during its outward propagation. The typical radial velocity of the blob-like structure, V-b, was measured as similar to 1 km/s with the fast camera at the intermediate area. V-b increased as the blob-like structure moved along major radius, R (outward). The average velocity of E x B drift derived from the probe measurement, slightly larger than V-b, was also increased as the blob-like structure propagated to larger R. (C) 2010 Elsevier B.V. All rights reserved..
177. K. Hanada, H. Zushi, H. Idei, K. Nakamura, M. Ishiguro, S. Tashima, E. I.Kalinnikova, M. Sakamoto, M. Hasegawa, A. Fujisawa, A. Higashijima, S. Kawasaki, H. Nakashima, H. Liu, O. Mitarai, T. Maekawa, A. Fukuyama, Y. Takase, J. Qian, Recent experiments and future collaborations on QUEST, JSPS-CAS Core University Program Seminar on Summary of 10-year Collaborations in Plasma and Nuclear Fusion Research Area 9?11 March 2011,Okinawa,Japan, 204.0, 204.0, 2011.07.
178. H Kasahara, K Saito, T Seki, R Kumazawa, G Nomura, F Shimpo, S Kubo, T Shimozuma, H Igami, T Wakatsuki, H Watada, H Idei, S Masuzaki, T Mutoh, The impact of ICRF heating using newly installed phasing antenna in LHD, 38th EPS Conference on Plasma Physics (2011), P2.099, 2011.06.
179. Hanada, K.; Zushi, H.; Idei, H.; Nakamura, K.; Ishiguro, M.; Tashima, S.; Kalinnikova, E. I.; Sakamoto, M.; Hasegawa, M.; Fujisawa, A.; Higashijima, A.; Kawasaki, S.; Nakashima, H.; Liu, H.; Mitarai, O.; Maekawa, T.; Fukuyama, A.; Takase, Y.; Qian, J., Non-Inductive Start up of QUEST Plasma by RF Power, PLASMA SCIENCE & TECHNOLOGY, 10.1088/1009-0630/13/3/08, 13.0, 3.0, 307.0-311.0, 0.0, 2011.06, Both start-up and sustainment of plasma were successfully achieved by fully non-inductive current drive using microwave with a frequency of 8.2 GHz. Plasmas current of 15 kA was implemented for 1 s. Magnetic surface reconstruction exhibited a plasma shape with an aspect ratio of below 1.5. The plasma current was dependent significantly on the launched microwave power and vertical magnetic field, while not affected by the mode of launched wave and the toroidal refractive index. Hard X-ray (HXR) emitted from energetic electrons accelerated by the microwave was observed, and the discharge with a plasma current over 4 kA followed the same trend as the number of photons of 10 keV to 12 keV. This suggests that the plasma current may be driven by energetic electrons. Based on the experimental conditions, alternative explanations of how the plasma current could be driven are discussed..
180. Osamu MITARAI, Kazuo NAKAMURA, Saya TASHIMA, Makoto HASEGAWA, Hiroshi IDEI, Mizuki SAKAMOTO, Kazuaki HANADA, Hideki ZUSHI, Kohnosuke SATO, Masaki ISHIGURO, Hai Qing LIU, Yuta HIGASHIZONO, Aki HIGASHIJIMA, Hisatoshi NAKASHIMA, Shoji KAWASAKI, Yuichi TAKASE, Takashi MAEKAWA and Nobuhiro NISHINO, First Ohmic Discharge Assisted with RF Power in QUEST Spherical Tokamak, Plasma and Fusion Research, 6.0, RA, Article No. 1402003, 2011.02, Ohmic plasma currents of up to 17 kA with a discharge duration of 0.32 s have been obtained in the Kyushu University Experiment with Steady-State Spherical Tokamak (QUEST) with the help of electron cyclotron wave (ECW) and cancellation coils (CCs). The CCs, originally installed to create a field null in the plasma breakdown phase, are essential for producing plasma current in QUEST. Although the ohmic coil current is initially biased and then reduced completely to zero to induce the plasma current in 15-20 ms, we demonstrate that the flat top of the plasma current exceeding 20 ms is maintained by the vertical field after the ohmic current is switched off. This type of operation is quite favorable for extending pulsed operation to the steady state by electron Bernstein wave current drive (EBCD)..
181. Hanada, K; Zushi, H; Idei, H; Nakamura, K; Ishiguro, M; Tashima, S; Kalinnikovab, EI; Sakamoto, M; Hasegawaa, M; Fujisawaa, A; , Recent experiments towards steady state operation of spherical tokamak QUEST, Proceeding of JSPS-CAS Core University Program Seminar on Production and Control of High Performance Plasmas with Advanced Plasma Heating and Diagnostic Systems 1-4 November, 2010, Guilin, China, Vol. , No. , Pages 42, 2011.01.
182. Haiqing LIU, Kazuaki HANADA, Nobuhiro NISHINO, Ryota OGATA, Masaki ISHIGURO, Hideki ZUSHI, Kazuo NAKAMURA, Mizuki SAKAMOTO, Hiroshi IDEI, Makoto HASEGAWA, Yuta HIGASHIZONO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA and QUEST GROUP, Measurement of Blob-Like Structures in Plasma with a Langmuir Probe and Fast Camera on QUEST, Plasma and Fusion Research, 5.0, RA, Article No. S2077, 2010.12, This paper presents a scheme for combining a Langmuir probe with a fast camera for measurement of the behavior of blob-like structures in the boundary region of an electron cyclotron resonance (ECR) heating plasma in Q-shu University Experiment with a Steady-State Spherical Tokamak (QUEST, major radius, R = 0.68 m, minor radius, a = 0.40 m, and toroidal magnetic field, Bt = 0.25 T at R = 0.64 m). The frame rate of the camera was typically set to 40,000 frames per second (FPS) with 192 × 144 pixels per frame. Radial motion of blob-like structures was observed in the half of the plasma space where the probe head was located. A radially movable and rotatable probe system was used to measure the floating potential from single unbiased tips, the potential of the positively biased tip, and the ion saturation current in two orthogonal directions in the outboard midplane region. Time series of the ion saturation current measured by the Langmuir probe and of pixels in a 40,000 FPS movie were compared and cross-correlated. The results of the two diagnostics agreed well, and the spatial scale was found to be of the same as the size of the probe head. The ion saturation current was asymmetric in terms of the time the blob-like structure was passing; fast camera imaging also clearly demonstrated the blobs' filamentary structures and radial motion at the edge of QUEST. This means that plasma in the blob-like structure hunches over, like blobs in other devices. The typical radial velocity of the structures is ∼1 km/s, and the structures were accelerated along their path of radial motion from the inner to the outer parts of the vacuum vessel..
183. Masaki ISHIGURO, Kazuaki HANADA, Kazuo NAKAMURA, Osamu MITARAI, Hideki ZUSHI, Hiroshi IDEI, Mizuki SAKAMOTO, Makoto HASEGAWA, Yuta HIGASHIZONO, Yuichi TAKASE, Takashi MAEKAWA, Yasuaki KISHIMOTO, Shoji KAWASAKI, Hisatoshi NAKASHIMA and Aki HIGASHIJIMA, Reconstruction of Vacuum Magnetic Flux in QUEST, Plasma and Fusion Research, 5.0, RA, Article No. S2083, 2010.12, It is important to determine the best method for reconstructing the magnetic flux when eddy currents are significantly induced during magnetic measurement in spherical tokamaks (STs). Four methods for this reconstruction are investigated, and the calculated magnetic fluxes are compared to those measured in the cavity of a vacuum vessel. The results show that the best method is the one that uses currents from virtual coils for reconstruction. In this method, the placement of the virtual coils is optimized with numerical simulations using the Akaike information criterion (AIC), which indicates the goodness of fit of models used to fit measured data. The virtual coils are set on a line 15 cm outside the vacuum vessel..
184. S. Tashima, H. Zushi, M. Isobe, S. Okamura, H. Idei, K. Hanada, S. K. Sharma, T. Ryoukai, M. Ishiguro, H. Liu, The role of fast electrons on the non-inductive current ramp-up in QUEST, 37th EPS Conference on Plasma Physics 2010, EPS 2010
37th EPS Conference on Plasma Physics 2010, EPS 2010
, 1716-1719, 2010.12, The role of energetic electrons during the non-inductive current ramp-up is investigated in electron cyclotron heated plasma (≤ 60kW) in the spherical tokamak QUEST. The pulse height analysis of the hard X-ray (HX) is carried out with a fast time resolution of ≥1 ms, and acceleration of the electrons are studied by measuring the evolution of spectrum. It is found that wall recycling condition affects the formation of the tokamak configuration from an initial open magnetic field configuration. The vertical magnetic field Bz dependence of driven current Ip (~ 11 kA) is compared with those of HXs for studying contribution of fast electron. For high recycling case, Ip and HXs show peaks at an optimal low value of Bz/Bt = 7 ×10-3, however, for low recycling case, both increase monotonically with B z/Bt = 7 ×10-3 - 21×10 -3..
185. Sharma, Sanjeev K.; Zushi, Hideki; Takagi, Ikuji; Hisano, Yuki; Sakamoto, Mizuki; Higashizono, Yuta; Shikama, Taichi; Morita, Sigeru; Tanabe, Tetsuo; Yoshida, Naoaki; Hanada, Kazuaki; Hasegawa, Makoto; Mitarai, Osamu; Nakamura, Kazuo; Idei, Hiroshi; Sato, Kohnosuke N.; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki; Nakashima, Yousuke; Nishino, Nobuyuki; Hatano, Yuji; Sagara, Akira; Nakamura, Yukio; Ashikawa, Naoko; Maekawa, Takashi; Kishimoto, Yasuaki; Takase, Yuichi, Measurement of hydrogen permeation due to atomic flux using permeation probe in the spherical tokamak QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2010.08.032, 85.0, 6.0, 950.0-955.0, 0.0, 2010.11, Particle retention and recycling in plasma fusion devices are generally associated with the diffusion of atomic hydrogen into the materials. The resulted permeation of atomic hydrogen is known as plasma driven permeation (POP). This permeation may also be significant, even in the walls, which are not directly exposed to the plasma. Under similar conditions, the permeation flux (Gamma(perm)) of hydrogen through a 30 mu m thick Ni membrane heated at 412-575K has been measured in the spherical tokamak QUEST. Gamma(perm) is being measured during the scans of different operating parameters like RF power (P(RF)), chamber pressure (P(chamber)), discharge widths (tau(dis)) and vertical magnetic field (B(Z)). Simultaneously edge plasma density and spectral intensities of atomic (Balmer) lines and molecular (Fulcher) bands have been compared with the permeation measurements. A linear relationship has been established between the time integrated Gamma(perm) i.e. permeation fluence (Q(perm)) and the time integrated H(alpha) intensity i.e. H(alpha) fluence (Q(alpha)). Q(perm) also shows a strong relationship with the edge plasma density and various spectral fluences. The obtained results are discussed for exploring the applicability of the permeation probes in measuring the atomic flux near the first walls. (C) 2010 Elsevier B.V. All rights reserved..
186. Hiroshi Idei, M. Sakaguchi, E. Kalinnikova, K. Nagata, H. Zushi, Kazuaki Hanada, K. Nakamura, M. Sakamoto, Makoto Hasegawa, Y. Takase, T. Maekawa, O. Mitarai, A. Fukuyamaf, S. Kawasaki, H. Nakashima, A. Higashijima, Development of CW phased-array antenna system for electron Bernstein heating and current drive experiments in QUEST, 35th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2010
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide
, 10.1109/ICIMW.2010.5612352, 2010.11, [URL], The CW phased-array antenna for the EBWH/CD has been developed in QUEST. The measured fields were in excellent agreement with those evaluated by the Kirchhoff integral. The thermal load and stress were analyzed. The phase array has been fast scanned to control the incident polarization and angle..
187. K. Nagata, Hiroshi Idei, M. Sakaguchi, K. Dono, Y. Wataya, S. Kawasaki, H. Zushi, Kazuaki Hanada, Kazuo Nakamura, M. Sakamoto, Makoto Hasegawa, Y. Higashizono, Y. Takase, T. Maekawa, O. Mitarai, Y. Kishimoto, H. Nakashima, A. Higashijima, Differential-phase reflectometry using phased-array antenna system in QUEST, 35th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2010
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide
, 10.1109/ICIMW.2010.5612434, 2010.11, [URL], The differential-phase reflectometry has been developed to measure the density profile, concerning electron Bernstein Wave (EBW) heating and current drive in the QUEST. The Phased Array Antenna (PAA) system was proposed for the reflectometry to improve the ratio of signal to noise. The PAA was confirmed to be effective, as a launching antenna to receive the larger reflected-wave signal..
188. H. Idei, K. Nagata, M. Sakaguchi, E. Kalinnikova, A. Fukuyama, S. Ohdachi, S. Inagaki, Y. Nagayama, K. Kawahata, H. Igami, S. Kubo, T. Shimozuma, H. Zushi, K. Hanada, K. N. Sato, K. Nakamura, M. Sakamoto, M. Hasegawa, Y. Takase, T. Maekawa, O. Mitarai, S. Kawasaki, H. Nakashima, A. Higashijima, Electron Bernstein wave emission diagnostics using phased-array antenna system in QUEST, 35th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2010
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide
, 10.1109/ICIMW.2010.5612710, 2010.11, [URL], The square waveguide phased-array antenna system has been developed for Electron Bernstein Emission diagnostics. The broadband orthomode transducer was prepared to measure the wave polarization. The measured fields were in good agreements with those evaluated from the Kirchhoff integral..
189. T. Shimozuma, S. Kubo, Y. Yoshimura, H. Igami, H. Takahashi, S. Kobayashi, S. Ito, Y. Mizuno, K. Okada, Y. Takita, T. Mutoh, H. Idei, R. Minami, T. Kariya, T. Imai, Progress of a multi-megawatt gyrotron system for electron cyclotron heating on the large helical device, 35th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2010
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide
, 10.1109/ICIMW.2010.5613060, 2010.11, [URL], In LHD, an ECH system for fusion-relevant plasma heating has been greatly progressed with the development of megawatt gyrotrons. Net power of 3.7 MW could be injected into LHD. For stable operation, a new position and profile monitor of the mmw-beams in evacuated transmission lines is developed..
190. M. Sakaguchi, Hiroshi Idei, K. Nagata, T. Saito, T. Shigematsu, Quasi-Optical HE11-mode exciter for coupling into oversized Circular Corrugated Waveguide, 35th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2010
IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide
, 10.1109/ICIMW.2010.5612688, 2010.11, [URL], The Quasi-Optical (QO) HE11-mode exciter has been considered for mode coupling into the circular corrugated waveguides. It contained a feed antenna and QO mirror system. A fields radiated from the feed antenna were measured, and the mode contents was analyzed with irradiant waveguide modes..
191. H. Zushi, N. Nishino, K. Hanada H. Honma, H. Q. Liu, Y. Higashizono, M. Sakamoto, Y. Nakashima, M. Ishiguro, T. Ryoukai, S. Tashima, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa, O. Mitarai, A. Fukuyama, Takeiri, Y. Takase, T. Maekawa, Y. Kishimoto, Study of Edge Turbulence from the Open to Closed Magnetic Field Configuration during the Current Ramp-up Phase in QUEST, Proc.23rd IAEA Fusion Energy Conference, 10-16 October 2010,Daejon,Republic of Korea, 2010.10.
192. Idei, H., and QUEST Team, Phased-array Antenna System for Electron Bernstein Wave Heating and Current Drive Experiments in QUEST, Proceedings of the 23rd IAEA Fusion Energy Conference, EXW/P7-31, 2010.09.
193. Sakaguchi, M; Idei, H; Nagata, K; Saito, T; Shigematsu, T; , Quasi-Optical HE 11-mode exciter for coupling into oversized circular corrugated waveguide, Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on, Article No. 41641, 2010.09.
194. Idei, H.; Sakaguchi, M.; Kalinnikova, E.; Nagata, K.; Zushi, H.; Hanada, K.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Takase, Y.; Maekawa, T.; Mitarai, O.; Fukuyama, A.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Development of CW Phased-array Antenna System for Electron Bernstein Heating and Current Drive Experiments in QUEST, 35TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ 2010), 2010.09, The CW phased-array antenna for the EBWH/CD has been developed in QUEST. The measured fields were in excellent agreement with those evaluated by the Kirchhoff integral. The thermal load and stress were analyzed. The phase array has been fast scanned to control the incident polarization and angle..
195. Nagata, K.; Idei, H.; Sakaguchi, M.; Dono, K.; Wataya, Y.; Kawasaki, S.; Zushi, H.; Hanada, K.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Higashizono, Y.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kishimoto, Y.; Nakashima, H.; Higashijima, A., Differential-phase Reflectometry using Phased-array Antenna System in QUEST, 35TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ 2010), 0.0, 0.0, 0.0-0.0, 0.0, 2010.09, The differential-phase reflectometry has been developed to measure the density profile, concerning electron Bernstein Wave (EBW) heating and current drive in the QUEST. The Phased Array Antenna (PAA) system was proposed for the reflectometry to improve the ratio of signal to noise. The PAA was confirmed to be effective, as a launching antenna to receive the larger reflected-wave signal..
196. Idei, H.; Nagata, K.; Sakaguchi, M.; Kalinnikova, E.; Fukuyama, A.; Ohdachi, S.; Inagaki, S.; Nagayama, Y.; Kawahata, K.; Igami, H.; Kubo, S.; Shimozuma, T.; Zushi, H.; Hanada, K.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Electron Bernstein Wave Emission Diagnostics using Phased-array Antenna System in QUEST, 35TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ 2010), 1.0-3.0, 2010.09, The square waveguide phased-array antenna system has been developed for Electron Bernstein Emission diagnostics. The broadband orthomode transducer was prepared to measure the wave polarization. The measured fields were in good agreements with those evaluated from the Kirchhoff integral..
197. H. Idei, K. Nagata, M. Sakaguchi, K. Dono, Y. Wataya, A. Ohdachi, S. Inagaki, Y. Nagayama, K. Kawahata, H. Igami, T. Shimozuma, H. Zushi, K. Hanada, K. Nakamura, M. Sakamoto, M. Hassegawa, Y. Higashizono, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai and Y. Kishimoto, Differential-Phase Reflectometry and Electron Bernstein Wave Radiometry using Phased-array Antenna System in the QUEST, Journal of Plasma and Fusion Research, 9.0, 112.0-117.0, (Proc.APFA2009/APPTC2009), 2010.08, The differential-phase reflectometry has been developed to measure the density profile evolution, concering electron Bernstein Wave (EBW) heating and current drive in the QUEST. The proper phase dependence was confirmed in developed single-side-band heterodyne differential-phase reflectometry at RIAM microwave/mm-wave test facilities. The phase time evolutions in the QUEST were also successfully measured, but the weak reflected-wave caused the small ratio of signal to noise in the measurements. The Phased Array Antenna (PAA) system was proposed for the reflectometry to obtain the large reflected-wave. The oblique viewing EBW emission can be measured by the precise phasearray measurements between the PAA waveguide elements. The PAA was confirmed to be effective, as a launching antenna for the reflectometry, and as a receiving antenna for the EBW radiometry. Keywords: AM reflectometry, Electron Bernstein wave, phased-array antenna, QUEST.
198. S. Tashima, H. Zushi, M. Isobe, S. Okamura, H. Idei, K. Hanada, T. Ryoukai, M. Ishiguro, S. Sharma, SHU and the QUEST group, Hard X-ray measurement during the current startup phase in QUEST, Journal of Plasma and Fusion Research SERIES, 9.0, 316.0-321.0, 2010.08.
199. H. Q. LIU, K. HANADA, N. NISHINO, R. OGATA, M. ISHIGURO, H. ZUSHI, K. NAKAMURA, K. N. SATO, M. SAKAMOTO, H. IDEI, M. HASEGAWA, Y. HIGASHIZONO, S. KAWASAKI, H. NAKASHIMA, A. HIGASHIJIMA, and QUEST GROUP, Measurement of blob-like structure behavior in the plasma edge in QUEST, Journal of Plasma and Fusion Research SERIES, 9.0, 33.0-36.0, (※), 2010.08.
200. Y. Higashizono, M. Sakamoto, Y. Nakashima, R. Yonenaga, H. Zushi, K. Hanada, M. Ishiguro, K. Nakamura, H. Idei, M. Hasegawa, K. N. Sato, I. Gouda, S. Tsuru, S. Kawasaki, H. Nakashima, A. Higashijima, N. Nishino, O. Mitarai, T. Maekawa, Y. Kishimoto, Y. Takase and QUEST Group:, Observation of separated plasma structure in non inductive discharge in QUEST, Journal of Plasma and Fusion Research SERIES, 9.0, 007-011, (※), 2010.08.
201. Osamu MITARAI, Kazuo NAKAMURA, Masaki ISHIGURO, Makoto HASEGAWA, Hiroshi IDEI, Mizuki SAKAMOTO, Kazuaki HANADA, Hideki ZUSHI, Hai Qing LIU, Saya TASHIMA, Yuta HIGASHIZONO, Aki HIGASHIJIMA, Hisatoshi NAKASHIMA, Shoji KAWASAKI and QUEST Group, Plasma Current Ramp-Up Experiments in QUEST, Journal of Plasma and Fusion Research, 9.0, (※), 2010.08.
202. S. K. Sharma, H. Zushi, I. Takagi, Y. Hisano, T. Shikama, S. Morita. T. Tanabe, N. Yoshida, M. Sakamoto, Y. Higashizono, K. Hanada, M. Hasegawa, O. Mitarai, K. Nakamura, H. Idei, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Nakashima, N. Nishino, Y. Hatano, A. Sagara, Y. Nakamura, N. Ashikawa, T. Maekawa, Y. Kishimoto, Y. Takase and QUEST Group, Study of the plasma driven permeation of hydrogen through a nickel membrane in RF and ohmic plasmas in the spherical tokamak QUEST, Journal of Plasma and Fusion Research SERIES, 9.0, Volume 9 (2010,pp142-146, 2010.08.
203. M. Ishiguro, K. Hanada, H. Zushi, K. N. Sato, K. Nakamura, H. Idei, M. Sakamoto, M. Hasegawa, T. Yoshinaga, S. Kawasaki, H. Nakashima, A. Higashijima, The Study about the Relationship between Plasma Current in Open Magnetic Field and the Formation of Closed Flux Surface in CPD, Journal of Plasma and Fusion Research SERIES, 9.0, Vol.9,018-022(※Proceedings of the 7th General Scientific Assembly of the Asia Plasma and Fusion Association in 2009 (APFA2009) and Asia-Pacific Plasma Theory Conference in 2009 (APPTC2009),October 27-30,2009,Aomori,Japan), 2010.08.
204. Shimozuma, T.; Takahashi, H.; Kubo, S.; Yoshimura, Y.; Igami, H.; Takita, Y.; Kobayashi, S.; Ito, S.; Mizuno, Y.; Idei, H.; Notake, T.; Sato, M.; Ohkubo, K.; Watari, T.; Mutoh, T.; Minami, R.; Kariya, T.; Imai, T., ECRH-RELATED TECHNOLOGIES FOR HIGH-POWER AND STEADY-STATE OPERATION IN LHD, FUSION SCIENCE AND TECHNOLOGY, 58.0, 1.0, 530.0-538.0, 0.0, 2010.07, The electron cyclotron resonance heating (ECRH) system on the Large Helical Device (LHD) has been in stable operation for similar to 11 yr in numerous plasma experiments. During this time, many upgrades to the system have been made, such as reinforcement of the gyrotron tubes, modification of the power supply depending on gyrotron type, and increase in the number of transmission lines and antennas. These efforts allow the stable injection of millimeter-wave power in excess of 2 MW. In parallel, various transmission components were evaluated, and antenna performance was confirmed at a high power level. The coupling efficiency of the millimeter wave from the gyrotron to the transmission line and the transmission efficiency through the waveguide were further improved in recent years. The feedback control of the wave polarization has also been tried to maximize the efficiency of wave absorption. The gyrotron oscillation frequency was reconsidered in order to extend the flexibility of the magnetic configuration in plasma experiments. The development of 77-GHz gyrotrons with the output of 1 MW per few seconds in a single tube is currently taking place in collaboration with the University of Tsukuba. Two such gyrotron tubes already have been installed and were used for plasma experiments recently. An ECRH system with a capability of the steady operation is required, because the LHD can continuously generate confinement magnetic fields using superconducting magnets. Not only the gyrotron but also the transmission system and components must withstand continuous power operation. Further acceleration of both the power reinforcement and a steady-state capability will allow the sustainment of high-performance plasmas..
205. Shimozuma, T.; Yokoyama, M.; Ida, K.; Takeiri, Y.; Kubo, S.; Murakami, S.; Wakasa, A.; Idei, H.; Yoshimura, Y.; Notake, T.; Inagaki, S.; Tamura, N.; Toi, K.; Ohyabu, N.; Osakabe, M.; Ikeda, K.; Tsumori, K.; Oka, Y.; Nagaoka, K.; Kaneko, O.; Yamada, I.; Narihara, K.; Nagayama, Y.; Muto, S.; Tanaka, K.; Tokuzawa, T.; Morita, S.; Goto, M.; Yoshinuma, M.; Funaba, H.; Morisaki, T.; Watanabe, K. Y.; Miyazawa, J.; Mutoh, T.; Watari, T.; Ohkubo, K., IMPROVEMENT OF PLASMA CORE CONFINEMENT VIA ELECTRON-ROOT REALIZATION BY STRONGLY FOCUSED ECRH IN LHD: CORE ELECTRON-ROOT CONFINEMENT, FUSION SCIENCE AND TECHNOLOGY, 58.0, 1.0, 38.0-45.0, 2010.07, Core electron-root confinement (CERC), observed in the Large Helical Device as well as in other helical devices, is an improved electron energy confinement mode. It is characterized by a highly peaked electron temperature profile in the core region and appears when the centrally focused electron cyclotron resonance heating power exceeds a certain threshold value. This threshold value has been clarified to associate with the transition of the radial electric field (E(r)) from the ion root (small negative value) to the electron root (large positive value greater than a few kV/m), based on the bifurcation nature of Er due to the ambipolarity condition of neoclassical transport fluxes that is specific in nonaxisymmetric configurations. It has been experimentally recognized that a steeper T(e) gradient is realized with a clear transition (power threshold nature) in target plasmas with counter neutral beam injection (NBI) than ones with codirectional NBI. It has been interpreted, based on the heat pulse propagation experiment, to be related to the rational sutface or the island induced by the NBI-driven current. Transport analyses have shown that the incremental thermal diffusivity of electron heat transport becomes lower, and the standard thermal diffusivity decreases with the increase of heating power in CERC plasmas..
206. Yoshimura, Y.; Kubo, S.; Shimozuma, T.; Igami, H.; Takahashi, H.; Kobayashi, S.; Ito, S.; Mizuno, Y.; Takita, Y.; Nakamura, Y.; Ohkubo, K.; Ikeda, R.; Ida, K.; Yoshinuma, M.; Sakakibara, S.; Mutoh, T.; Nagasaki, K.; Idei, H.; Notake, T., PROGRESS TOWARD STEADY-STATE OPERATION IN LHD USING ELECTRON CYCLOTRON WAVES, FUSION SCIENCE AND TECHNOLOGY, 58.0, 1.0, 551.0-559.0, 0.0, 2010.07, Trials of steady-state operation (SSO) in the Large Helical Device (LHD) were started when a continuous wave (cw) gyrotron with the output power up to 0.2 MW was introduced to the electron cyclotron heating (ECH) system on LHD in 2003. During the first trial of SSO in the seventh LHD experimental campaign in 2004, severe temperature increase on the waveguide transmission line and, as a result, intense pressure increase in the evacuated wave guide occurred, which terminated the operation at 756 s. Additional pumping sections and cooling structures on the transmission line worked well, allowing a 3900-s sustainment of plasma with n(e) = 0.15 x 10(19) m(-3) and T(e0) = 1.7 keV by 0.1 MW injection power in 2005. The improvement of the ECH system by introducing cw gyrotrons with higher power for further improvement of plasma performance in SSO is in progress.Investigations on electron cyclotron current drive (ECCD) physics have been advanced a few years after the proof of ECCD in LHD. By obliquely injecting second-harmonic X-mode EC waves in toroidal direction, stable current up to 5.5 kA is driven, which was evaluated as a difference in plasma currents of the co- and counter-ECCD discharges with 0.1-MW EC wave power. It takes a few seconds for the driven current to saturate. Change in profile of rotational transform by ECCD and profile of driven current density are investigated by use of motional Stark effect measurement. Peaked and localized driven current profile at the plasma core region was confirmed for on-axis second-harmonic ECCD discharges..
207. Igami, H.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Notake, T.; Takahashi, H.; Idei, H.; Inagaki, S.; Tanaka, H.; Nagasaki, K.; Ohkubo, K.; Mutoh, T., RESEARCH OF ELECTRON CYCLOTRON RESONANCE HEATING METHODS AND RELEVANT EXPERIMENTS, FUSION SCIENCE AND TECHNOLOGY, 58.0, 1.0, 539.0-550.0, 0.0, 2010.07, For expanding applicable parameter ranges of electron cyclotron resonance heating (ECRH), various methods of ECRH have been studied with use of millimeter-wave sources of 77-, 82.7-, 84-, and 168-GHz gyrotrons in the Large Helical Device (LHD). The fundamental ordinary (O-) mode and the second-harmonic extraordinary (X-) mode are mainly used for starting up, sustaining, and controlling the plasma. Heating efficiencies of ECRH by launching of these modes have been investigated experimentally for wide range of the central electron density and compared with power absorption rates obtained by ray-tracing calculation. ECRH by the third-harmonic X-mode has been performed in each magnetic configuration B(ax) = 1 and 2 T with launching of 84-GHz range and 168-GHz millimeter waves. Increases of the electron temperature and the stored energy were observed in both cases. ECRH by the electrostatic electron Bernstein wave (EBW) has been expected to be a promising substitute in parameter ranges where the conventional methods of ECRH by the electromagnetic modes are not available. To perform ECRH by the EBW in LHD, extraordinary-EBW (X-B) and ordinary-extraordinary-EBW (O-X-B) mode conversion processes, the propagation of the wave, and the absorption have been investigated experimentally and theoretically..
208. Shimozuma, T.; Kubo, S. ; Yoshimura, Y. ; Igami, H. ; Takahashi, H. ; Kobayashi, S. ; Ito, S. ; Mizuno, Y. ; Okada, K. ; Takita, Y. ; Mutoh, T. ; Idei, H. ; Minami, R. ; Kariya, T. ; Imai, T.;, Progress of a multi-megawatt gyrotron system for electron cyclotron heating on the large helical device, Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on, 2010, (※), 2010.06.
209. TASHIMA, S; ZUSHI, H; ISOBE, M; OKAMURA, S; IDEI, H; HANADA, K; , The role of fast electrons on the non-inductive current ramp-up in QUEST, 37th EPS Conference on Plasma Physics, Dublin,Ireland,2010.6.21-6.25, 2010.06.
210. S. K. Sharma, H. Zushi, I. Takagi, Y. Hisano, T. Shikama, S. Morita, T. Tanabe, N. Yoshida, M. Sakamoto, Y. Higashizono, K. Hanada, M. Hasegawa, O. Mitarai, K. Nakamura, H. Idei, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Nakashima, N. Nishino, Y. Hatano, A. Sagara, Y. Nakamura, N. Ashikawa, T. Maekawa, Y. Kishimoto, Y. Takase and QUEST GroupS, Wall pumping studies in spherical tokamak QUEST using permeation measurements and a static gas balance method,, 10th International Workshop on Hydrogen Isotopes in Fusion Reactor Materials, Pleasanton,and the Livermore Valley,California,May 31 - June 1,2010, 2010.05.
211. H. Idei, M. Sakaguchi, E. I. Kalinnikova, K. Nagata, H. Zushi, K. Hanada, S. Tashima, M. Ishiguro, , H. Q. Liu, H. Igami3, S. Kubo, K. Nakamura, A. Fujisawa, M. Sakamoto, M. Hassegawa, Y. Higashizono, R. Ogata, T. Ryokai, S. K. Sharma, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai and Y. Kishimoto, Development of Phased-array Antenna System and Its Application to EBWH/CD Experiments in QUEST, 16th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating,Sanya,China, 269.0-274.0, (※), 2010.04.
212. Kalinnikova, E, Idei Hiroshi, zushi hideki, hanada kazuaki, Igami, H, Kubo, S, Fukuyama, A, Nuga, H., Multiple ray-tracing analysis for EBWH/CD experiments in QUEST, Proceedings of the 16th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, Vol. 1, No. , Pages 275-280, 2010.04.
213. Mizuki Sakamoto, Yuta Higashizono, Hideki Zushi, Kazuo Nakamura, Kazuaki Hanada, Hiroshi Idei, Makoto Hasegawa, Yousuke Nakashima, Masayuki Tokitani, Mitsutaka Miyamoto, Kazutoshi Tokunaga, Shoji Kawasaki, Hisatoshi Nakashima, Tadashi Fujiwara, Aki Higashijima, Naoaki Yoshida and Kohnosuke Sato, Plasma-Wall Interaction Study towards the Steady State Operation, Plasma and Fusion Research, 5.0, RA, Article No. S2009, 2010.04.
214. Kazuaki Hanada, Kohnosuke Sato, Hideki Zushi, Kazuo Nakamura, Mizuki Sakamoto, Hiroshi Idei, Makoto Hasegawa, Yuichi Takase, Osamu Mitarai, Takashi Maekawa, Yasuaki Kishimoto, Masaki Ishiguro, Tomokazu Yoshinaga, Hiroe Igami, Nobuhiro Nishino, Hiroshi Honma, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Yuta Higashizono, Akira Ando, Nobuyuki Asakura, Akira Ejiri, Yoshihiko Hirooka, Akio Ishida, Akio Komori, Makoto Matsukawa, Osamu Motojima, Yuichi Ogawa, Noriyasu Ohno, Yasushi Ono, Martin Peng, Shigeru Sudo, Hiroshi Yamada, Naoaki Yoshida, Zensho Yoshida, Steady-state operation scenario and the first experimental result on QUEST, Plasma and Fusion Research, 5.0, RA, Article No. S1007, 2010.03.
215. Sharma, S. K.; Zushi, H.; Osakabe, M.; Takeiri, Y.; Yoshida, N.; Hasegava, M.; Yoshinaga, T.; Hanada, K.; Idei, H.; Sakamoto, M.; Nakamura, K.; Sato, K. N., Analysis of the footprint traces on the first walls of the compact plasma wall interaction device (CPD) using surface analysis and electron orbit calculations, NUCLEAR FUSION, 10.1088/0029-5515/50/2/025017, 50.0, 2.0, 0.0-0.0, Article No. 025017, 2010.02, After the non-inductive current startup experimental campaign on the spherical tokamak compact plasma wall interaction device (CPD), various localized damage tracks or footprint traces have been observed on plasma facing components (PFCs), such as the chamber walls and the 'stiffeners' that support them. Although the magnetic field configuration is mainly open, the footprint traces are classified as (1) radially distributed traces, (2) toroidal imperfect circular traces with small gaps, (3) arc-shaped traces and (4) vertically distributed traces. The surface analysis of the samples attached near the traces has been carried out by scanning electron microscopy and x-ray photoelectron spectroscopy. They suggest thin deposition of impurity materials (C, Cu, Ti, Fe and their oxides) over the traces. These footprint traces are analysed in view of the localized plasma wall interaction and the loss of energetic electrons using orbit calculations. Radially distributed traces correspond to the loss of co- and countermoving passing electrons mainly escaping along the magnetic field lines. The imperfect circular traces are found corresponding to lost orbits of the energetic trapped electrons largely crossing the magnetic field lines. Other traces are also discussed from a viewpoint of loss along the magnetic field lines and impurity deposition..
216. Takashi Shimozuma, Hiroshi Idei, Michael A Shapiro, Richard J Temkin, Shin Kubo, Hiroe Igami, Yasuo Yoshimura, Hiromi Takahashi, Satoshi Ito, Sakuji Kobayashi, Yoshinori Mizuno, Yasuyuki Takita, Takashi Mutoh, Mode-Content Analysis and Field Reconstruction of Propagating Waves in Corrugated Waveguides of an ECH System, Plasma and Fusion Research, 5.0, RA, Article No. S1030, 2010.01.
217. RYOUKAI, Tomofumi; ZUSHI, Hideki; MORISAKI, Tomohiro; IDEI, Hiroshi; HANADA, Kazuaki; DONO, Kousuke; MUTOH, Takashi; KUBO, Shin; NAGASAKI, Kazunobu; , The correlation analysis between electron density fluctuation and RF stray power in the CPD electron cyclotron plasma, Journal of Plasma and Fusion Research SERIES, 9.0, 310.0-315.0, 2010.01.
218. T. Shimozuma, H. Takahashi, S. Kubo, Y. Yoshimura, H. Igami, Y. Takita, S. Kobayashi, S. Ito, Y. Mizuno, Hiroshi Idei, T. Notake, M. Sato, K. Ohkubo, T. Watari, T. Mutoh, R. Minami, T. Kariya, T. Imai, Ecrh-related technologies for high-power and steady-state operation in LHD, Fusion Science and Technology, 10.13182/FST58-530, 58, 1, 530-538, 2010.01, [URL], The electron cyclotron resonance heating (ECRH) system on the Large Helical Device (LHD) has been in stable operation for ∼11 yr in numerous plasma experiments. During this time, many upgrades to the system have been made, such as reinforcement of the gyrotron tubes, modification of the power supply depending on gyrotron type, and increase in the number of transmission lines and antennas. These efforts allow the stable injection of millimeter-wave power in excess of 2 MW. In parallel, various transmission components were evaluated, and antenna performance was confirmed at a high power level. The coupling efficiency of the millimeter wave from the gyrotron to the transmission line and the transmission efficiency through the waveguide were further improved in recent years. The feedback control of the wave polarization has also been tried to maximize the efficiency of wave absorption. The gyrotron oscillation frequency was reconsidered in order to extend the flexibility of the magnetic configuration in plasma experiments. The development of 77-GHz gyrotrons with the output of 1 MW per few seconds in a single tube is currently taking place in collaboration with the University of Tsukuba. Two such gyrotron tubes already have been installed and were used for plasma experiments recently. An ECRH system with a capability of the steady operation is required, because the LHD can continuously generate confinement magnetic fields using superconducting magnets. Not only the gyrotron but also the transmission system and components must withstand continuous power operation. Further acceleration of both the power reinforcement and a steady-state capability will allow the sustainment of high-performance plasmas..
219. T. Shimozuma, M. Yokoyama, K. Ida, Y. Takeiri, S. Kubo, S. Murakami, A. Wakasa, Hiroshi Idei, Y. Yoshimura, T. Notake, Inagaki Shigeru, N. Tamura, K. Toi, N. Ohyabu, M. Osakabe, K. Ikeda, K. Tsumori, Y. Oka, K. Nagaoka, O. Kaneko, I. Yamada, K. Narihara, Y. Nagayama, S. Muto, K. Tanaka, T. Tokuzawa, S. Morita, M. Goto, M. Yoshinuma, H. Funaba, T. Morisaki, K. Y. Watanabe, J. Miyazawa, T. Mutoh, T. Watari, K. Ohkubo, Improvement of plasma Core confinement via electron-root realization by strongly focused ECRH in LHD
Core electron-root confinement, Fusion Science and Technology, 10.13182/FST10-A10791, 58, 1, 38-45, 2010.01, [URL], Core electron-root confinement (CERC), observed in the Large Helical Device as well as in other helical devices, is an improved electron energy confinement mode. It is characterized by a highly peaked electron temperature profile in the core region and appears when the centrally focused electron cyclotron resonance heating power exceeds a certain threshold value. This threshold value has been clarified to associate with the transition of the radial electric field (Er) from the ion root (small negative value) to the electron root (large positive value greater than a few kV/m), based on the bifurcation nature of Er due to the ambipolarity condition of neoclassical transport fluxes that is specific in nonaxisymmetric configurations. It has been experimentally recognized that a steeper Te gradient is realized with a clear transition (power threshold nature) in target plasmas with counter neutral beam injection (NBI) than ones with codirectional NBI. It has been interpreted, based on the heat pulse propagation experiment, to be related to the rational surface or the island induced by the NBI-driven current. Transport analyses have shown that the incremental thermal diffusivity of electron heat transport becomes lower, and the standard thermal diffusivity decreases with the increase of heating power in CERC plasmas..
220. Haiqing Liu, Kazuaki Hanada, Nobuhiro Nishino, Ryota Ogata, Masaki Ishiguro, Hideki Zushi, Kazuo Nakamura, Mizuki Sakamoto, Hiroshi Idei, Makoto Hasegawa, Yuta Higashizono, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Measurement of blob-like structures in plasma with a Langmuir probe and fast camera on QUEST, Plasma and Fusion Research, 10.1585/pfr.5.S2077, 5, 2010.01, [URL], This paper presents a scheme for combining a Langmuir probe with a fast camera for measurement of the behavior of blob-like structures in the boundary region of an electron cyclotron resonance (ECR) heating plasma in Q-shu University Experiment with a Steady-State Spherical Tokamak (QUEST, major radius, R = 0.68 m, minor radius, a = 0.40 m, and toroidal magnetic field, Bt = 0.25T at R = 0.64 m). The frame rate of the camera was typically set to 40,000 frames per second (FPS) with 192 ×144 pixels per frame. Radial motion of blob-like structures was observed in the half of the plasma space where the probe head was located. A radially movable and rotatable probe system was used to measure the floating potential from single unbiased tips, the potential of the positively biased tip, and the ion saturation current in two orthogonal directions in the outboard midplane region. Time series of the ion saturation current measured by the Langmuir probe and of pixels in a 40,000 FPS movie were compared and cross-correlated. The results of the two diagnostics agreed well, and the spatial scale was found to be of the same as the size of the probe head. The ion saturation current was asymmetric in terms of the time the blob-like structure was passing; fast camera imaging also clearly demonstrated the blobs' filamentary structures and radial motion at the edge of QUEST. This means that plasma in the blob-like structure hunches over, like blobs in other devices. The typical radial velocity of the structures is ~1km/s, and the structures were accelerated along their path of radial motion from the inner to the outer parts of the vacuum vessel..
221. Takashi Shimozuma, Hiroshi Idei, Michael A. Shapiro, Richard J. Temkin, Shin Kubo, Hiroe Igami, Yasuo Yoshimura, Hiromi Takahashi, Satoshi Ito, Sakuji Kobayashi, Yoshinori Mizuno, Yasuyuki Takita, Takashi Mutoh, Mode-content analysis and field reconstruction of propagating waves in corrugated Waveguides of an ECH system, Plasma and Fusion Research, 10.1585/pfr.5.S1029, 5, 2010.01, [URL], A new method is proposed to analyze the mode content of high power electromagnetic waves that are propagating through corrugated waveguides in the electron cyclotron resonance heating (ECH) systems for nuclear fusion devices. The method was applied to the 168GHz transmission line of the ECH system in the Large Helical Device (LHD) to evaluate the waveguide alignment. The mode content of the propagating waves could be accurately analyzed using this method. Furthermore, the wave field in the waveguide was reconstructed using the mode content information obtained for each mode..
222. Mizuki Sakamoto, Yuta Higashizono, Hideki Zushi, Kazuo Nakamura, Kazuaki Hanada, Hiroshi Idei, Makoto Hasegawa, Younosuke Nakashima, Masayuki Tokitani, Mitsutaka Miyamoto, Kazutoshi Tokunaga, Shoji Kawasaki, Hisatoshi Nakashima, Tadashi Fujiwara, Aki Higashijima, Naoaki Yoshida, Kohnosuke Sato, Plasma-wall interaction study towards the steady state operation, Plasma and Fusion Research, 10.1585/pfr.5.S2009, 5, 2010.01, [URL], Various phenomena of plasma-wall interactions during long duration discharges in TRIAM-1M are investigated from macroscopic and microscopic viewpoints. It is found that the density dependence of the hydrogen neutral flux decay length is not very sensitive to the density (i.e. ne-0.2 ). Neutral transport through the scrape-off layer is important for structural formation of hydrogen recycling. The hydrogen retention in the co-deposited layer, which was obtained using a material probe during long duration discharges, is consistent with the global wall pumping rate estimated from particle balance analysis. The wall temperature and co-deposition play important roles on hydrogen re-emission and hydrogen absorption, respectively. Oxygen impurities should affect the erosion and deposition properties of the plasma-facing wall as well as the hydrogen retention property of the co-deposited layer. The co-deposition of hydrogen with molybdenum and the oxygen impurities both play important roles in the hydrogen recycling..
223. Y. Yoshimura, S. Kubo, T. Shimozuma, H. Igami, H. Takahashi, S. Kobayashi, S. Ito, Y. Mizuno, Y. Takita, Y. Nakamura, K. Ohkubo, R. Ikeda, K. Ida, M. Yoshinuma, S. Sakakibara, T. Mutoh, K. Nagasaki, Hiroshi Idei, T. Notake, Progress toward steady-state operation in LHD using electron cyclotron waves, Fusion Science and Technology, 10.13182/FST58-551, 58, 1, 551-559, 2010.01, [URL], Trials of steady-state operation (SSO) in the Large Helical Device (LHD) were started when a continuous wave (cw) gyrotron with the output power up to 0.2 MW was introduced to the electron cyclotron heating (ECH) system on LHD in 2003. During the first trial of SSO in the seventh LHD experimental campaign in 2004, severe temperature increase on the waveguide transmission line and, as a result, intense pressure increase in the evacuated waveguide occurred, which terminated the operation at 756 s. Additional pumping sections and cooling structures on the transmission line worked well, allowing a 3900-s sustainment of plasma with ne=0.15 ×1019 m-3 and Te0 = 1.7 keV by 0.1 MW injection power in 2005. The improvement of the ECH system by introducing cw gyrotrons with higher power for further improvement of plasma performance in SSO is in progress. Investigations on electron cyclotron current drive (ECCD) physics have been advanced a few years after the proof of ECCD in LHD. By obliquely injecting secondharmonic X-mode EC waves in toroidal direction, stable current up to 5.5 kA is driven, which was evaluated as a difference in plasma currents of the co-and counter-ECCD discharges with 0.1-MW EC wave power. It takes a few seconds for the driven current to saturate. Change in profile of rotational transform by ECCD and profile of driven current density are investigated by use of motional Stark effect measurement. Peaked and localized driven current profile at the plasma core region was confirmed for on-axis second-harmonic ECCD discharges..
224. Masaki Ishiguro, Kazuaki Hanada, Kazuo Nakamura, Osamu Mitarai, Hideki Zushi, Hiroshi Idei, Mizuki Sakamoto, Makoto Hasegawa, Yuta Higashizono, Yuichi Takase, Takashi Maekawa, Yasuaki Kishimoto, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Reconstruction of vacuum magnetic flux in QUEST, Plasma and Fusion Research, 10.1585/pfr.5.S2083, 5, 2010.01, [URL], It is important to determine the best method for reconstructing the magnetic flux when eddy currents are significantly induced during magnetic measurement in spherical tokamaks (STs). Four methods for this reconstruction are investigated, and the calculated magnetic fluxes are compared to those measured in the cavity of a vacuum vessel. The results show that the best method is the one that uses currents from virtual coils for reconstruction. In this method, the placement of the virtual coils is optimized with numerical simulations using the Akaike information criterion (AIC), which indicates the goodness of fit of models used to fit measured data. The virtual coils are set on a line 15 cm outside the vacuum vessel..
225. H. Igami, S. Kubo, T. Shimozuma, Y. Yoshimura, T. Notake, H. Takahashi, Hiroshi Idei, Inagaki Shigeru, H. Tanaka, K. Nagasaki, K. Ohkubo, T. Mutoh, Research of electron cyclotron resonance heating methods and relevant experiments, Fusion Science and Technology, 10.13182/FST10-A10841, 58, 1, 539-550, 2010.01, [URL], For expanding applicable parameter ranges of electron cyclotron resonance heating (ECRH), various methods of ECRH have been studied with use of millimeter-wave sources of 77-, 82.7-, 84-, and 168-GHz gyrotrons in the Large Helical Device (LHD). The fundamental ordinary (0-) mode and the secondharmonic extraordinary (X-) mode are mainly used for starting up, sustaining, and controlling the plasma. Heating efficiencies of ECRH by launching of these modes have been investigated experimentally for wide range of the central electron density and compared with power absorption rates obtained by ray-tracing calculation. ECRH by the third-harmonic X-mode has been performed in each magnetic configuration Bax = 1 and 2 T with launching of 84-GHz range and 168-GHz millimeter waves. Increases of the electron temperature and the stored energy were observed in both cases. ECRH by the electrostatic electron Bernstein wave (EBW) has been expected to be a promising substitute in parameter ranges where the conventional methods of ECRH by the electromagnetic modes are not available. To perform ECRH by the EBW in LHD, extraordinary-EBW (X-B) and ordinary-extraordinary-EBW (O-X-B) mode conversion processes, the propagation of the wave, and the absorption have been investigated experimentally and theoretically..
226. Kazuaki Hanada, Kohnosuke Sato, Hideki Zushi, Kazuo Nakamura, Mizuki Sakamoto, Hiroshi Idei, Makoto Hasegawa, Yuichi Takase, Osamu Mitarai, Takashi Maekawa, Yasuaki Kishimoto, Masaki Ishiguro, Tomokazu Yoshinaga, Hiroe Igami, Nobuhiro Nishino, Hiroshi Honma, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Yuta Higashizono, Akira Ando, Nobuyuki Asakura, Akira Ejiri, Yoshihiko Hirooka, Akio Ishida, Akio Komori, Makoto Matsukawa, Osamu Motojima, Yuichi Ogawa, Noriyasu Ohno, Yasushi Ono, Martin Peng, Shigeru Sudo, Hiroshi Yamada, Naoaki Yoshida, Zensho Yoshida, Steady-state operation scenario and the first experimental result on QUEST, Plasma and Fusion Research, 10.1585/pfr.5.S1007, 5, 2010.01, [URL], QUEST focuses on the steady state operation of the spherical tokamak by controlled PWI and electron Bernstein wave current drive. One of the main purposes of QUEST is an achievement of long duration discharge with MW-class injected power. As the result, QUEST should be operated in the challenging region on heat and particle handling. To do the particle handling, high temperature all metal wall up to 623K and closed divertors are planned, which is to realize the steady-state operation under recycling ratio, R = 1. This is a dispensable check to DEMO, because wall pumping should be avoided as possible in the view of tritium retention. The QUEST project will be developed in increment step such as, I. low β steady state operation in limiter configuration, II. low β steady state operation in divertor configuration, III. relatively high β steady state operation in closed divertor configuration. Phase I in the project corresponds to these two years, and final goal of phase I is to make full current drive plasma up to 20 kA. Closed divertor will be designed and tested in the Phase II. QUEST is running from Oct., 2008 and the first results are introduced..
227. T. Shimozuma, S. Kubo, Y. Yoshimura, H. Igami, H. Takahashi, R. Ikeda, N. Tamura, S. Kobayashi, S. Ito, Y. Mizuno, Y. Takita, T. Mutoh, R. Minami, T. Kariya, T. Imai, H. Idei, M. A. Shapiro, R. J. Temkin, F. Felici, T. Goodman, O. Sauter, Activities on realization of high-power and steady-state ECRH system and achievement of high performance plasmas in LHD, 18th Topical Conference on Radio Frequency Power in plasmas
Radio Frequency Power in plasmas - Proceedings of the 18th Topical Conference
, 10.1063/1.3273796, 479-486, 2009.12, [URL], Electron Cyclotron Resonance Heating (ECRH) has contributed to the achievement of high performance plasma production, high electron temperature plasmas and sustainment of steady-state plasmas in the Large Helical Device (LHD). Our immediate targets of upgrading the ECRH system are 5 MW several seconds and 1 MW longer than one hour power injection into LHD. The improvement will greatly extend the plasma parameter regime. For that purpose, we have been promoting the development and installation of 77 GHz/1-1.5 MW/several seconds and 0.3 MW/CW gyrotrons in collaboration with University of Tsukuba. The transmission lines are re-examined and improved for high and CW power transmission. In the recent experimental campaign, two 77 GHz gyrotrons were operated. One more gyrotron, which was designed for 1.5 MW/2 s output, was constructed and is tested. We have been promoting to improve total ECRH efficiency for efficient gyrotron-power use and efficient plasma heating, e.g. a new waveguide alignment method and mode-content analysis and the feedback control of the injection polarization. In the last experimental campaign, the 77 GHz gyrotrons were used in combination with the existing 84 GHz range and 168 GHz gyrotrons. Multi-frequency ECRH system is more flexible in plasma heating experiments and diagnostics. A lot of experiments have been performed in relation to high electron temperature plasmas by realization of the core electron-root confinement (CERC), electron cyclotron current drive (ECCD), Electron Bernstein Wave heating, and steady-state plasma sustainment. Some of the experimental results are briefly described..
228. H. Igami, Hiroshi Idei, R. Ikeda, E. Kawamori, S. Ito, Y. Ono, K. Toi, S. Kubo, Y. Yoshimura, T. Shimozuma, H. Takahashi, T. Maekawa, H. Tanaka, T. Mutoh, Development of an analysis method on the mode conversion process between electromagnetic and electron Bernstein waves in real experimental configurations, 34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
, 10.1109/ICIMW.2009.5325602, 2009.12, [URL], A numerical code has been developed to treat the mode conversion process between electromagnetic and electron Bernstein waves for arbitrary propagation angle and polarization considering real experimental configurations on various devices. Robustness of any heating/detection condition with change of the plasma parameters or the frequency can be also estimated with this numerical code in a short time..
229. Takashi Shimozuma, Shin Kubo, Yasuo Yoshimura, Hiroe Igami, Hiromi Takahashi, Yasuyuki Takita, Sakuji Kobayashi, Satoshi Ito, Yoshinori Mizuno, Hiroshi Idei, Takashi Notake, Michael A. Shapiro, Richard J. Temkin, Federico Felici, Timothy Goodman, Olivier Sauter, Ryutaro Minami, Tsuyoshi Kariya, Tsuyoshi Imai, Takashi Mutoh, Handling technology of Mega-Watt millimeter-waves for optimized heating of fusion plasmas, Journal of Microwave Power and Electromagnetic Energy, 43, 1, 43160-43170, 2009.12, Millimeter-wave components were re-examined for high power (Mega-Watt) and steady-state (greater than one hour) operation. Some millimeter-wave components, including waveguide joints, vacuum pumping sections, power monitors, sliding waveguides, and injection windows, have been improved for high power CW (Continuous Waves) transmission. To improve transmission efficiency, information about the wave phase and mode content of high power millimeter-waves propagating in corrugated waveguides, which are difficult to measure directly, were obtained by a newly developed method based on retrieved phase information. To optimize the plasma heating efficiency, a proof-of-principle study of the injection polarization feedback control was performed in the low power test stand..
230. H. Idei, M. A. Shapiro, R. J. Temkin, T. Shimozuma, S. Kubo, Mode retrieval from intensity profile measurements using irradiant waveguide-modes, 34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
, 10.1109/ICIMW.2009.5324607, 2009.12, [URL], The fields radiated from the waveguide were used to analyze propagating mode content in an oversized circular corrugated waveguide. The radiated fields were calculated by the Kirchhoff integral in the paraxial approximation. The irradiant waveguide modes of the radiated field are orthogonal within the paraxial approximation. The complex fractions in the irradiant mode expansion were deduced from an iteration process in which the reconstructed amplitude profile from the complex fractions coincided with the measured amplitude profile..
231. H. Idei, M. Sakaguchi, H. Kasahara, K. Saito, M. Tsukamoto, K. Hanada, H. Zushi, K. N. Sato, K. Nakamura, M. Sakamoto, M. Hasegawa, Y. Higashizono, Y. Takase, T. Maekawa, O. Mitarai, Y. Kishimoto, S. Kawasaki, H. Nakashima, A. Higashijima, Phased-array antenna for electron Bernstein wave heating and current drive in QUEST, 34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
, 10.1109/ICIMW.2009.5324704, 2009.12, [URL], The phased-array antenna has been designed for steady-state electron Bernstein wave heating and current drive at 8.2 GHz in the QUEST tokamak. The prototype antenna had rather large side-lobe components. In the new designed antenna the side-lobe components were reduced by modification of the antenna structure. For the steady-state operation, forced water-cooling and thermal stress were analyzed for the antenna component using the HFSS/ePhysics/ANSYS codes..
232. H. Idei, K. Dono, Y. Wataya, K. Nagata, S. Kawasaki, H. Zushi, K. Hanada, K. N. Sato, K. Nakamura, M. Sakamoto, M. Hasegawa, Y. Higashizono, Y. Takase, T. Maekawa, O. Mitarai, Y. Kishimoto, H. Nakashima, A. Higashijima, Single-side-band heterodyne differential-phase reflectometry in QUEST, 34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009
, 10.1109/ICIMW.2009.5324785, 2009.12, [URL], In a spherical tokamak (ST), an operating frequency of the reflectometry is low due to the low magnetic field of the device. In the large ST, the reflected wave signal level is weak in the large propagating length, and a direct coupling between the launching and receiving antennae may become comparable level to the reflected signal due to the diffraction effect in the low operating frequency at the ST. New single-side-band heterodyne differential-phase reflectometry is proposed on a large ST device of the QUEST, to remove the direct coupling effect in an amplitude modulation reflectometry..
233. H. Zushi, T. Ryoukai, K. Kikukawa, T. Morisaki, R. Bhattacharyay, T. Yoshinaga, K. Hanada, T. Sakimura, H. Idei, K. Dono, N. Nishino, H. Honma, S. Tashima, T. Mutoh, S. Kubo, K. Nagasaki, M. Sakamoto, Y. Nakashima, Y. Higashizono, K. N. Sato, K. Nakamura, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, Two dimensional density fluctuation measurements during the non-inductive current ramp-up phase in the compact plasma wall interaction experimental device CPD, Plasma Science and Technology, 10.1088/1009-0630/11/4/06, 11, 4, 397-401, 2009.12, [URL], Two-dimensional structure of density fluctuations is examined during the current jump phase, indicating a change from the open magnetic fields to the closed ones. During the smooth current ramp-up phase the two-dimensional contour of the LiI intensity shows vertically alignment, consistent with the magnetic surfaces. At the inflection point in Ip ramp-up the LiI intensity contour becomes flat in the observation regime and then suddenly a steep gradient and higher intensity regime are formed in the vertical direction. This higher intensity corresponds to a burst of LiI waveform. According to these changes in the contour, it is found that, within 1 ms around the burst of LiI, a low frequency coherent wave with a long wavelength rapidly grows. The relations with other signals (magnetic flux and microwave stray power) are discussed with respect to the topological change in the magnetic configuration and mode conversion of the incident electromagnetic waves..
234. Komori, A.; Yamada, H.; Sakakibara, S.; Kaneko, O.; Kawahata, K.; Mutoh, T.; Ohyabu, N.; Imagawa, S.; Ida, K.; Nagayama, Y.; Shimozuma, T.; Watanabe, K. Y.; Mito, T.; Kobayashi, M.; Nagaoka, K.; Sakamoto, R.; Yoshida, N.; Ohdachi, S.; Ashikawa, N.; Feng, Y.; Fukuda, T.; Igami, H.; Inagaki, S.; Kasahara, H.; Kubo, S.; Kumazawa, R.; Mitarai, O.; Murakami, S.; Nakamura, Yuji; Nishiura, M.; Hino, T.; Masuzaki, S.; Tanaka, K.; Toi, K.; Weller, A.; Yoshinuma, M.; Narushima, Y.; Ohno, N.; Okamura, T.; Tamura, N.; Saito, K.; Seki, T.; Sudo, S.; Tanaka, H.; Tokuzawa, T.; Yanagi, N.; Yokoyama, M.; Yoshimura, Y.; Akiyama, T.; Chikaraishi, H.; Chowdhuri, M.; Emoto, M.; Ezumi, N.; Funaba, H.; Garcia, L.; Goncharov, P.; Goto, M.; Ichiguchi, K.; Ichimura, M.; Idei, H.; Ido, T.; Iio, S.; Ikeda, K.; Irie, M.; Isayama, A.; Ishigooka, T.; Isobe, M.; Ito, T.; Itoh, K.; Iwamae, A.; Hamaguchi, S.; Hamajima, T.; Kitajima, S.; Kado, S.; Kato, D.; Kato, T.; Kobayashi, S.; Kondo, K.; Masamune, S.; Matsumoto, Y.; Matsunami, N.; Minami, T.; Michael, C.; Miura, H.; Miyazawa, J.; Mizuguchi, N.; Morisaki, T.; Morita, S.; Motojima, G.; Murakami, I.; Muto, S.; Nagasaki, K.; Nakajima, N.; Nakamura, Y.; Nakanishi, H.; Nakano, H.; Narihara, K.; Nishimura, A.; Nishimura, H.; Nishimura, K.; Nishimura, S.; Nishino, N.; Notake, T.; Obana, T.; Ogawa, K.; Oka, Y.; Ohishi, T.; Okada, H.; Okuno, K.; Ono, K.; Osakabe, M.; Osako, T.; Ozaki, T.; Peterson, B. J.; Sakaue, H.; Sasao, M.; Satake, S.; Sato, K.; Sato, M.; Shimizu, A.; Shiratani, M.; Shoji, M.; Sugama, H.; Suzuki, C.; Suzuki, Y.; Takahata, K.; Takahashi, H.; Takase, Y.; Takeiri, Y.; Takenaga, H.; Toda, S.; Todo, Y.; Tokitani, M.; Tsuchiya, H.; Tsumori, K.; Urano, H.; Veshchev, E.; Watanabe, F.; Watanabe, T.; Watanabe, T. H.; Yamada, I.; Yamada, S.; Yamagishi, O.; Yamaguchi, S.; Yoshimura, S.; Yoshinaga, T.; Motojima, O., Development of net-current free heliotron plasmas in the Large Helical Device, NUCLEAR FUSION, 10.1088/0029-5515/49/10/104015, 49.0, 10.0, 0.0-0.0, Article No. 104015, 2009.10, Remarkable progress in the physical parameters of net-current free plasmas has been made in the Large Helical Device (LHD) since the last Fusion Energy Conference in Chengdu, 2006 (Motojima et al 2007 Nucl. Fusion 47 S668). The beta value reached 5% and a high-beta state beyond 4.5% from the diamagnetic measurement has been maintained for longer than 100 times the energy confinement time. The density and temperature regimes have also been extended. The central density has exceeded 1 x 10(21) m(-3) due to the formation of an internal diffusion barrier. The ion temperature has reached 5.2 keV at the density of 1.6 x 10(19) m(-3), which is associated with the suppression of ion heat conduction loss. Although these parameters have been obtained in separated discharges, each fusion-reactor relevant parameter has elucidated the potential of net-current free heliotron plasmas. Diversified studies in recent LHD experiments are reviewed in this paper..
235. Kazuaki Hanada, Kohnosuke Sato, Hideki Zushi, Kazuo Nakamura, Mizuki Sakamoto, Hiroshi Idei, Makoto Hasegawa, Yuichi Takase, Takashi Maekawa, Osamu Mitarai, Physical design and future plan of QUEST, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.129.589, 129, 9, 589-594+5, 2009.10, [URL], The QUEST (Kyushu, pronounced as "Q-shu" University Experiment with Steady-state spherical Tokamak) project is promoted from 2005 in the frame work of bi-directional collaboration organized by N1FS (National Institute for Fusion Science) to study plasma wall interaction on high temperature all-metal wall in long duration plasma on a spherical tokamak configuration. Present status and future plan of QUEST are presented..
236. Kazuo NAKAMURA, Shinji MATSUFUJI, Masashi TOMODA, Feng WANG, Osamu MITARAI, Kenichi KURIHARA, Yoichi KAWAMATA, Michiharu SUEOKA, Makoto HASEGAWA, Kazutoshi TOKUNAGA, Kohnosuke SATO, Hideki ZUSHI, Kazuaki HANADA, Mizuki SAKAMOTO, Hiroshi IDEI, Shoji KAWASAKI, Hisatoshi NAKASHIMA and Aki HIGASHIJIMA, Characteristics of SVD in ST Plasma Shape Reproduction Method Based on CCS, Journal of Plasma and Fusion Research, 8.0, 1048.0-1051.0, 2009.09.
237. H. Igami, H. Idei, R. Ikeda, E. Kawamori, S. Ito, Y. Ono, K. Toi, S. Kubo, Y. Yoshimura, T. Shimozuma, H. Takahashi, T. Maekawa H. Tanaka, T. Mutoh, LHD experiment groupa and CHS experiment group, Development of an analysis method on the mode conversion process between electromagnetic and electron Bernstein waves in real experimental configurations, Proceeding of 34th International Conference on Infrared and Millimeter Waves and THz Electronics,, 2.0, (※), 2009.09, A numerical code has been developed to treat the mode conversion process between electromagnetic and electron Bernstein waves for arbitrary propagation angle and polarization considering real experimental configurations on various devices. Robustness of any heating/detection condition with change of the plasma parameters or the frequency can be also estimated with this numerical code in a short time..
238. T. Ryoukai, H. Zushi, R. Bhattacharyay, H. Idei, T. Yoshinaga, CPD Group, T. Morisaki, T. Mutoh, S. Kubo, K. Nagasaki, Field line tying and magnetic shear effects of the vertical magnetic field on low frequency density fluctuations in CPD, Journal of Plasma and Fusion Research SERIES, 8.0, 105.0-108.0, 2009.09.
239. Takeuchi, Norio; Idei, Hiroshi; Fukuyama, Atsushi; Seki, T; Kumazawa, R; Mutoh, T; Saito, K; , Multiple Ray Trace Analysis for Fast Wave Heating and Current Drive using LHD Combline Antenna System, Journal of Plasma and Fusion Research SERIES, 8.0, Vol. 8, p.865-868, 2009.09.
240. Tomokazu YOSHINAGA, Kazuaki HANADA, Kohnosuke SATO, Hideki ZUSHI, Kazuo NAKAMURA, Hiroshi IDEI, Mizuki SAKAMOTO, Yousuke NAKASHIMA, Makoto HASEGAWA, Yuta HIGASHIZONO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA, Rajendraprasad BHATTACHARYAY, Kosuke DONO, Hiroshi HONMA, Masaki ISHIGURO, Takashi SAKIMURA, Tomofumi RYOKAI and Toshimasa MIYAZAKI, Non-inductive formation of spherical tokamak plasmas by ECH on CPD, Journal of Plasma and Fusion Research SERIES, 8.0, Vol.8,pp.100-104, 2009.09.
241. H. Idei, M. Sakaguchi, H. Kasahara, K. Saito, K. Hanada, H. Zushi, K. N. Sato, K. Nakamura, M. Sakamoto, M. Hasegawa, Y. Takase, T. Maekawa, O. Mitarai, Y. Kishimoto, S. Kawasaki, H. Nakashima, A.. Higashijima, Y. Higashizono, Phased-array antenna for Electron Bernstein Heating and Current Drive in QUEST, Proc. 34th International Conference on Infrared,Millimeter,and Terahertz Waves, (※), 2009.09.
242. 花田 和明 , 佐藤 浩之助, 図子 秀樹, 中村 一男, 坂本 瑞樹, 出射 浩, 長谷川 真, 高瀬 雄一, 前川 孝 , 御手洗 修, QUESTの設計と将来計画, 電気学会論文誌Vol.129,No.9「核融合炉実用化への課題と球状トカマク研究」 特集論文(Ⅰ), vol.129,No.9, 2009.09.
243. H. Idei, N. Takeuchi, S. Kubo, A. Fukuyama, H. Nuga, M. Sakaguchi, N. Nakamura, K. Hanada, H. Zushi, K. N. Sato, M. Sakamoto, M. Hasegawa, Y. Takase, O. Mitarai, Maekawa and Y. Kishimoto, Ray Trace and Fokker-Plank Analyses for Electron Bernstein Wave Heating and Current Drive in QUEST, Journal of Plasma and Fusion Research SERIES, 8.0, Vol.8,pp.1104-1107, 2009.09.
244. H. Honma, K. Hanada, N. Fukumoto, M. Nagata, N. Nishino, K. N. Sato, K. Nakamura, H. Zushi, H. Idei, M. Sakamoto, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, S. Kawakami, T. Yoshinaga, Calorimetric measurement of kinetic energy of compact toroid in the spherical tokamak CPD, Journal of Plasma and Fusion Research, 8.0, 1015.0-1019.0, 2009.08.
245. Zushi, H.; Ryoukai, T.; Kikukawa, K.; Morisaki, T.; Bhattacharyay, R.; Yoshinaga, T.; Hanada, K.; Sakimura, T.; Idei, H.; Dono, K.; Nishino, N.; Honma, H.; Tashima, S.; Mutoh, T.; Kubo, S.; Nagasaki, K.; Sakamoto, M.; Nakashima, Y.; Higashizono, Y.; Sato, K. N.; Nakamura, K.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Two Dimensional Density Fluctuation Measurements During the Non-Inductive Current Ramp-up Phase in the Compact Plasma Wall Interaction Experimental Device CPD, PLASMA SCIENCE & TECHNOLOGY, 11.0, 4.0, 397.0-401.0, 0.0, 2009.08, Two-dimensional structure of density fluctuations is examined during the current jump phase, indicating a change from the open magnetic fields to the closed ones. During the smooth current ramp-up phase the two-dimensional contour of the LiI intensity shows vertically alignment, consistent with the magnetic surfaces. At the inflection point in I(p) ramp-up the LiI intensity contour becomes flat in the observation regime and then suddenly a steep gradient and higher intensity regime are formed in the vertical direction. This higher intensity corresponds to a burst of LiI wave form. According to these changes in the contour, it is found that, within +/-1 ms around the burst of LiI, a low frequency coherent wave with a long wavelength rapidly grows. The relations with other signals (magnetic flux and microwave stray power) are discussed with respect to the topological change in the magnetic configuration and mode conversion of the incident electromagnetic waves..
246. Hirooka, Y.; Zushi, H.; Bhattacharyay, R.; Sakamoto, M.; Idei, H.; Yoshinaga, T.; Nakashima, Y.; Higashizono, Y., Active particle control in the CPD compact spherical tokamak by a lithium-gettered rotating drum limiter, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2009.01.060, 390.0, 502.0-506.0, 2009.06, Active particle control capabilities of a lithium-gettered rotating drum poloidal limiter have been demonstrated during 50 kW RF-current drive discharges in a compact spherical tokamak with the major and minor radii of 30 and 20 cm, respectively. The pulse length is typically similar to 300 ms with a flat-top of similar to 250 ms. The rotating limiter is in the shape of cylinder with the diameter and axial length of 15 and 12 cm, respectively. It has reproducibly been observed that, as soon as the rotating drum is gettered with lithium, hydrogen recycling measured with H(proportional to) spectroscopy decreases by a factor of similar to 3 not only near the limiter but also in the center stack region. Also, the oxygen impurity level measured with O-II spectroscopy is reduced by a factor of similar to 3. Meanwhile, the core electron temperature increases from around 7 eV to 20 eV along which the flat-top toroidal plasma current is found to nearly double even at the same vertical magnetic field. Comprehensive surface analysis has been conducted to investigate hydrogen and lithium distributions over the rotating drum after plasma exposure. (C) 2009 Elsevier B.V. All rights reserved..
247. T Shimozuma, S Kubo, Y Yoshimura, H Igami, H Takahashi, R Ikeda, N Tamura, S Kobayashi, S Ito, Y Mizuno, Y Takita, T Mutoh, R Minami, T Kariya, T Imai, H Idei, MA Shapiro, RJ Temkin, F Felici, T Goodman, O Sauter, Activities on Realization of High‐Power and Steady‐State ECRH System and Achievement of High Performance Plasmas in LHD, RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 18th Topical Conference, 1187.0, 1.0, 479.0-486.0, 2009.06, Electron Cyclotron Resonance Heating (ECRH) has contributed to the achievement of high performance plasma production, high electron temperature plasmas and sustainment of steady‐state plasmas in the Large Helical Device (LHD). Our immediate targets of upgrading the ECRH system are 5 MW several seconds and 1 MW longer than one hour power injection into LHD. The improvement will greatly extend the plasma parameter regime. For that purpose, we have been promoting the development and installation of 77 GHz/1–1.5 MW/several seconds and 0.3 MW/CW gyrotrons in collaboration with University of Tsukuba. The transmission lines are re‐examined and improved for high and CW power transmission. In the recent experimental campaign, two 77 GHz gyrotrons were operated. One more gyrotron, which was designed for 1.5 MW/2 s output, was constructed and is tested. We have been promoting to improve total ECRH efficiency for efficient gyrotron‐power use and efficient plasma heating, e.g. a new waveguide alignment method and mode‐content analysis and the feedback control of the injection polarization. In the last experimental campaign, the 77 GHz gyrotrons were used in combination with the existing 84 GHz range and 168 GHz gyrotrons. Multi‐frequency ECRH system is more flexible in plasma heating experiments and diagnostics. A lot of experiments have been performed in relation to high electron temperature plasmas by realization of the core electron‐root confinement (CERC), electron cyclotron current drive (ECCD), Electron Bernstein Wave heating, and steady‐state plasma sustainment. Some of the experimental results are briefly described..
248. Takashi Shimozuma, Shin Kubo, Yasuo Yoshimura, Hiroe Igami, Hiromi Takahashi, Yasuyuki Takita, Sakuji Kobayashi, Satoshi Ito, Yoshinori Mizu-no, Hiroshi Idei, Takashi Notake, Michael A Shapiro, Richard J Temkin, Federico Felici, Timothy Goodman, Olivier Sauter, Ryutaro Minami, Tsuyoshi Kariya, Tsuyoshi Imai, Takashi Mutoh, Handling technology of mega-watt millimeter-waves for optimized heating of fusion plasmas, Journal of Microwave Power & Electromagnetic Energy ONLINE, 43.0, 1.0, 60.0-70.0, 2009.05.
249. Zushi, H.; Hirooka, Y.; Bhattacharyay, R.; Sakamoto, M.; Nakashima, Y.; Yoshinaga, T.; Higashizono, Y.; Hanada, K.; Nishino, N.; Yoshida, N.; Tokunaga, K.; Kado, S.; Shikama, T.; Kawasaki, S.; Okamoto, K.; Miyazaki, T.; Honma, H.; Sato, K. N.; Nakamura, K.; Idei, H.; Hasegawa, M.; Nakashima, H.; Higashijima, A., Active particle control experiments and critical particle flux discriminating between the wall pumping and fuelling in the compact plasma wall interaction device CPD spherical tokamak, NUCLEAR FUSION, 10.1088/0029-5515/49/5/055020, 49.0, 5.0, 9.0, Article No. 055020, 2009.05, Two approaches associated with wall recycling have been performed in a small spherical tokamak device CPD (compact plasma wall interaction experimental device), that is, (1) demonstration of active particle recycling control, namely, 'active wall pumping' using a rotating poloidal limiter whose surface is continuously gettered by lithium and (2) a basic study of the key parameters which discriminates between 'wall pumping and fuelling'. For the former, active control of 'wall pumping' has been demonstrated during 50kW RF current drive discharges whose pulse length is typically similar to 300 ms. Although the rotating limiter is located at the outer board, as soon as the rotating drum is gettered with lithium, hydrogen recycling measured with H a spectroscopy decreases by about a factor of 3 not only near the limiter but also in the centre stack region. Also, the oxygen impurity level measured with O II spectroscopy is reduced by about a factor of 3. As a consequence of the reduced recycling and impurity level, RF driven current has nearly doubled at the same vertical magnetic field. For the latter, global plasma wall interaction with plasma facing components in the vessel is studied in a simple torus produced by electron cyclotron waves with I(p) < 1 kA. A static gas balance (pressure measurement) without external pumping systems has been performed to investigate the role of particle flux on a transition of 'wall fuelling' to 'wall pumping'. It is found that a critical particle flux exists to discriminate between them. Beyond the critical value, a large fraction (similar to 80%) of pressure drop ('wall pumping') is found, suggesting that almost all injected particles are retained in the wall. Below it, a significant pressure rise ('wall fuelling') is found, which indicates that particles are fuelled from the wall during/just after the discharge. Shot history effects (integrated particle recycling behaviour from the plasma facing surfaces) are seen on that the critical particle flux is reducing from 0.8 x 10(-4) to similar to 0.1 x 10(-4) Torr during the experimental campaign (similar to 3000 shots). In the wall pumping pressure range the wall pumping fraction is reduced with increasing surface temperature up to 150 degrees C..
250. Idei, H.; Shapiro, M. A.; Temkin, R. J.; Shimozuma, T.; Kubo, S., Mode Retrieval from Intensity Profile Measurements using Irradiant Waveguide-modes, 2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2, 0.0, 0.0, 619.0-620.0, 0.0, 2009.04, The fields radiated from the waveguide were used to analyze propagating mode content in an oversized circular corrugated waveguide. The radiated fields were calculated by the Kirchhoff integral in the paraxial approximation. The irradiant waveguide modes of the radiated field are orthogonal within the paraxial approximation. The complex fractions in the irradiant mode expansion were deduced from an iteration process in which the reconstructed amplitude profile from the complex fractions coincided with the measured amplitude profile..
251. Idei, H.; Sakaguchi, M.; Kasahara, H.; Saito, K.; Tsukamoto, M.; Hanada, K.; Zushi, H.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Higashizono, Y.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kishimoto, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Phased-array Antenna for Electron Bernstein Wave Heating and Current Drive in QUEST, 2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2, 0.0, 0.0, 686.0-687.0, 0.0, 2009.04, The phased-array antenna has been designed for steady-state electron Bernstein wave heating and current drive at 8.2 GHz in the QUEST tokamak. The prototype antenna had rather large side-lobe components. In the new designed antenna the side-lobe components were reduced by modification of the antenna structure. For the steady-state operation, forced water-cooling and thermal stress were analyzed for the antenna component using the HFSS/ePhysics/ANSYS codes..
252. Idei, H.; Dono, K.; Wataya, Y.; Nagata, K.; Kawasaki, S.; Zushi, H.; Hanada, K.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Hasegawa, M.; Higashizono, Y.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kishimoto, Y.; Nakashima, H.; Higashijima, A., Single-Side-Band Heterodyne Differential-Phase Reflectometry in QUEST, 2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2, 0.0, 0.0, 718.0-719.0, 0.0, 2009.04, In a spherical tokamak (ST), an operating frequency of the reflectometry is low due to the low magnetic field of the device. In the large ST, the reflected wave signal level is weak in the large propagating length, and a direct coupling between the launching and receiving antennae may become comparable level to the reflected signal due to the diffraction effect in the low operating frequency at the ST. New single-side-band heterodyne differential-phase reflectometry is proposed on a large ST device of the QUEST, to remove the direct coupling effect in an amplitude modulation reflectometry..
253. Hanada, Kazuaki; Sato, Kohnosuke; Zushi, Hideki; Nakamura, Kazuo; Sakamoto, Mizuki; Idei, Hiroshi; Hasegawa, Makoto; Takase, Yuichi; Maekawa, Takashi; Mitarai, Osamu; , Physical Design and Future Plan of QUEST, IEEJ Transactions on Fundamentals and Materials, 129.0, 9.0, 589.0-594.0, 2009.01.
254. Bhattacharyay, R.; Zushi, H.; Hirooka, Y.; Sakamoto, M.; Yoshinaga, T.; Okamoto, K.; Kawasaki, S.; Hanada, K.; Sato, K. N.; Nakamura, K.; Idei, H.; Ryoukai, T.; Nakashima, H.; Higashijima, A., Study on wall recycling behaviour in CPD spherical tokamak, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2008.05.009, 83.0, 7.0, 1114.0-1119.0, 0.0, 2008.12, Experiments to study wall recycling behaviour have been performed in the small spherical tokamak compact plasma-wall interaction experimental device (CPD) from the viewpoint of global as well as local plasma wall interaction condition. Electron cyclotron resonance (ECR) plasma of typically similar to 50 to 400 ms duration is produced using similar to 40 to 80 kW RF power. In order to study the global wall recycling behaviour, pressure measurements are carried out just before and after the ECR plasma in the absence of any external pumping. The recycling behaviour is found to change from release to pumping beyond a certain level of pressure value which is again found to be a function of shot history. The real-time local wall behaviour is studied in similar RF plasma using a rotating tungsten limiter, actively coated with lithium. Measurement of H. light intensity in front of the rotating surface has indicated a clear reduction (similar to 10%) in the steady-state hydrogen recycling with continuous Li gettering of several minutes. (C) 2008 Elsevier BY. All rights reserved..
255. T. Shimozuma, H. Idei, M. A. Shapiro, R. J. Temkin, S. Kubo, Y. Yoshimura, H. Igami, H. Takahashi, T. Notake, S. Ito, S. Kobayashi, Y. Mizuno, Y. Takita, T. Mutoh, Propagating mode analysis and field reconstruction in the corrugated waveguides of a high power electron cyclotron heating system, 33rd International Conference on Infrared and Millimeter Waves and the 16th International Conference on Terahertz Electronics, 2008, IRMMW-THz 2008
33rd International Conference on Infrared and Millimeter Waves and the 16th International Conference on Terahertz Electronics, 2008, IRMMW-THz 2008
, 10.1109/ICIMW.2008.4665825, 2008.12, [URL], A new method is proposed to analyze mode contents of high power electromagnetic waves that are propagating through corrugated waveguides in the electron cyclotron resonance heating (ECH) system for nuclear fusion devices. The method was applied to a 168GHz transmission line of the ECH system in Large Helical Device (LHD) to evaluate the waveguide misalignment. Mode contents of the propagating wave could be well obtained, and the wave field in the waveguide was reconstructed by using the information of each mode..
256. N. Fukumoto, K. Hanada, S. Kawakami, S. Honma, M. Nagata, N. Nishino, H. Zushi, K. Sato, K. Nakamura, H. Idei, M. Sakamoto, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, R. Bhattachayay, K. Okamoto, Y. Kikuchi, Investigation of compact toroid penetration for fuelling spherical tokamak plasmas on CPD, Proc. 22nd IAEA Fusion Energy Conference, EX/P5-7 , 2008.10.
257. K. Hanada, K. N.Sato, H. Zushi, K. Nakamura, M. Sakamoto, H. Idei, M. Hasegawa, Y. Takase, O. Mitarai, T. Maekawa, Y. Kishimoto, M. Ishiguro, T. Yoshinaga, H. Igami, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Higashizono, A. Ando, N. Asakura, A. Ejiri, Y. Hirooka, A. Ishida, A. Komori, M. Matsukawa, O. Motojima, Y. Ogawa, N. Ohno, Y. Ono, M. Peng, S. Sudo, H. Yamada, N. Yoshida, Z. Yoshida, Physical design of MW-class steady-state spherical tokamak, QUEST, IAEA Fusion Energy Conference 2008, Proceedings of the 22nd IAEA Fusion Energy Conference, Geneva, 13-18 October 2008, FT/P3-25, 2008.10, QUEST (R=0.68m, a=0.4m) focuses on the steady state operation of the spherical tokamak (ST) by controlled PWI and electron Bernstain wave (EBW) current drive (CD). The QUEST project will be developed along two phases, phase I: steady state operation with plasma current, Ip=20-30kA on open divertor configuration and phase II: steady state operation with Ip=100kA and β of 10% in short pulse on closed divertor configuration. Feasibility of the missions on QUEST was investigated and the suitable machine size of QUEST was decided based on the physical view of plasma parameters. Electron Bernstein wave (EBW) current drive are planned to establish the maintenance of plasma current in steady state. Mode conversion efficiency to EBW was calculated and the conversion of 95% will be expected. A new type antenna for QUEST has been fabricated to excite EBW effectively. The situation of heat and particle handling is challenging, and W and high temperature wall is adopted. The start-up scenario of plasma current was investigated based on the driven current by energetic electron and the most favorable magnetic configuration for start-up is proposed..
258. T. Yoshinaga, K. Hanada, H. Zushi, K. Nakamura, K. N. Sato, H. Idei, M. Sakamoto, M. Hasegawa, T. Morisaki, Y. Nakashima, N. Nishino, M. Nagata, N. Fukumoto, Y. Takase, T. Maekawa, Y. Kishimoto, O. Mitarai, N. Yoshida, K. Tokunaga, Y. Hirooka, Y. Higashizono, S. Kawasaki, H. Nakashima, A. Higashijima, R. Bhattacharyay, S. Kawano, S. Kawakami, T. Kikukawa, K. Dono, M. Ishiguro, H. Honma, T. Miyazaki, T. Ryokai, T. Sakimura, Y. Inada, S. Watanabe and Y. Wataya, Physics Study of EC-Excited Current Generation via Current Jump in the Compact Plasma-Wall-Interaction Experimental Device, Proc.22nd IAEA Fusion Energy Conference, (※), 2008.10.
259. H. ZUSHI, T. RYOUKAI, K. KIKUKAWA, T. MORISAKI, R. BHATTACHARYAY, T. YOSHINAGA, K. HANADA, H. IDEI, M. SAKAMOTO, Y. NAKASHIMA, Y. HIGASHIZONO, N. NISHINO, K. DONO, T. SAKIMURA, T. MIYAZAKI, H. HONMA, S. TASHIMA, K. N. SATO, K. NAKAMURA, M. HASEGAWA, S. KAWASAKI H. NAKASHIMA, A. HIGASHIJIMA, Study on Density Fluctuations during the RF Current Ramp-up Phase in the CPD Spherical Tokamak, Proc. Joint Meeting of the 4th IAEA Technical Meeting on Spherical Tori and the 14th International Workshop on Spherical Torus, 2008.10.
260. H. ZUSHI, T. RYOUKAI, K. KIKUKAWA, T. MORISAKI, R. BHATTACHARYAY, T. YOSHINAGA, K. HANADA, H. IDEI, M. SAKAMOTO, Y. NAKASHIMA, Y. HIGASHIZONO, N. NISHINO, K. DONO, T. SAKIMURA, T. MIYAZAKI, H. HONMA, S. TASHIMA, K. N. SATO, K. NAKAMURA, M. HASEGAWA, S. KAWASAKI H. NAKASHIMA, A. HIGASHIJIMA, Study on Fluctuations during the RF Current Ramp-up Phase in the CPD Spherical Tokamak, Proc. Joint Meeting of the 4th IAEA Technical Meeting on Spherical Tori and the 14th International Workshop on Spherical Torus,Frascati,Italy,October 7-10,2008, 2008.10.
261. Bhattacharyay, R.; Zushi, H.; Fukumoto, N.; Nagata, M.; Nishino, N.; Honma, H.; Kawakami, K.; Yoshida, N.; Kawasaki, S.; Yoshinaga, T.; Sasaki, K.; Hasegawa, M.; Sato, K. N.; Sakamoto, M.; Nakamura, K.; Idei, H.; Nakashima, H.; Higashijima, A., Effects of magnetic field and target plasma on the penetration behaviour of compact toroid plasma by heat load measurements in CPD, NUCLEAR FUSION, 10.1088/0029-5515/48/10/105001, 48.0, 10.0, Article No. 105001, 2008.10, Compact toroid (CT) injection experiments have recently been carried out in a compact plasma wall interaction experimental device (CPD) in the presence of toroidal as well as poloidal magnetic field and low density RF target plasma. Spectroscopic studies have been carried out using an IR camera, an IR spectrometer and an H(alpha) monitor to estimate the heat load deposition on the target and also to study the magnetic field as well as RF target plasma effects on CT plasma penetration behaviour. Using IR camera imaging of the target plate, heat load deposition on it has been estimated from the observed temperature rise of the plate and has been compared with the energy content of CT plasma. The estimation suggests that nearly 700 J of energy is uniformly deposited on the target plate under vacuum condition without any magnetic field. On the other hand, post exposure analysis of target plate using scanning electron microscopy has indicated local melting of the target plate. It has been observed that radial penetration of CT towards the target plate is reduced with the increase in the external magnetic field, both toroidal and poloidal. Moreover, the presence of RF target plasma in external magnetic fields seems to change the CT penetration behaviour significantly..
262. H. Zushi, Y. Hirooka, M. Sakamoto, Y. Nakashima, R. Bhattacharyay, T. Yoshinaga, Y. Higashizono, K. Hanada, N. Nishino, N. Yoshida, K. Tokunaga, S. Kado, T. Shikama, Kawasaki, K. Okamoto, T. Miyazaki, H. Honma, K. N. Sato, K. Nakamura, H. Idei, M. Hasegawa, H. Nakashima, A. Higashijima, Particle recycling in the CPD Spherical Tokamak, Proceedings of the Joint Meeting of 4th IAEA Technical Meeting on Spherical Tori 14th International Workshop on Spherical Torus, 2008.10.
263. Takashi NOTAKE, Takashi SHIMOZUMA, Shin KUBO, Hiroshi IDEI, Katsumi IDA, Kiyomasa WATANABE, Satoru SAKAKIBARA, Taiki YAMAGUCHI, Mikirou YOSHINUMA, Takashi KOBUCHI, Shigeru INAGAKI, Tokihiko TOKUZAWA, Yasuo YOSHIMURA, Hiroe IGAMI, Tetsuo SEKI, Hitoshi TANAKA, Kazunobu NAGASAKI and LHD Experimental Group, First Demonstration of Rotational Transform Control by Electron Cyclotron Current Drive in Large Helical Device, Plasma and Fusion Research, 3.0, RA, Article No. S1077, 2008.06, An active current drive is a promising technique for improving plasma performances by controlling rotational transform and/or magnetic shear profiles in helical devices. A current drive based on electron cyclotron resonance heating is the most appropriate scheme for this purpose in terms of locality of driven current. Optimum conditions for an efficient electron cyclotron current drive (ECCD) in Large Helical Device (LHD) are being investigated using three-dimensional ray-tracing code, which can simulate propagation and power dissipation of electron cyclotron waves with large parallel refractive index. In the present experiment, inversion of directions of driven plasma current corresponding to injected ECCD modes was demonstrated successfully, and the results could be elucidated by the Fisch-Boozer theory. In addition, clear shifts of rotational transform were observed by motional Stark effect polarimetry. Our findings verified that the ECCD can be used as an effective actuator for controlling the rotational transform and magnetic shear profile in LHD..
264. Hasegawa, M.; Higashijima, A.; Nakamura, K.; Hanada, K.; Sato, K. N.; Sakamoto, M.; Idei, H.; Kawasaki, S.; Nakashima, H., A WEB-based integrated data processing system for the TRIAM-1M, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2007.12.012, 83.0, 4.0, 588.0-593.0, 2008.05, In TRIAM-1M, plasma discharge can be sustained for over five hours [H. Zushi, et al., Steady-state tokamak operation, ITB transition and sustainment and ECCD experiments in TRIAM-1M, Nucl. Fusion 45 (2005) S142-S156]. In order to avoid sitting in front of one console for the purpose of monitoring the plasma discharge, it is recommended that the experimental information be accessible from any location at any time. In addition, simple services to access experimental information are required in order to promote the participation of multiple researchers in the TRIAM-1M experiment. Thus, A WEB-based integrated data processing system that provides management for experiment planning, an experimental log, numerical data, and plasma supervision has been installed in the TRIAM-1M. These services are composed primarily of an Apache WEB server, a Tomcat JSP/Servlet container, and a MySQL relational database. This system is constructed using the object-oriented Java language, which is easy to maintain and develop because of the intrinsic characteristics of the Java language. When participating in experiments, researchers are required only to prepare a WEB browser on any platform and are no longer required to memorize complex operations because all services are provided with a uniform user interface through a WEB browser. Furthermore, with the integration of these services, the required information and numerical data can be provided promptly by tracing HTML links that are created dynamically by server applications. (C) 2007 Elsevier B.V. All rights reserved..
265. Nakamura, K.; Hasegawa, M.; Wang, R.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Sato, K. N.; Zushi, H.; Hanada, K.; Sakamoto, M.; Idei, H., Control system and the controllability of CPD and QUEST, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2008.01.004, 83.0, 2.0, 236.0-240.0, 2008.04, Superconducting tokamak TRIAM-1M has just ceased its operation in December 2005. However, in order to develop the systematic study on plasma-wall interaction in long duration discharges in the TRIAM-1M tokamak, spherical tokamak QUEST is under construction. To fulfill the mission of QUEST under a small group of the university in collaboration with other group, control and interlock system must be designed appropriately. Hence, a spherical tokamak CPD was constructed and the experiment is carried out for preparation of QUEST. The control and interlock system for QUEST is tested and developed during the experiment in the CPD. (c) 2008 Elsevier B.V. All rights reserved..
266. Hasegawa, M.; Nakamura, K.; Higashijima, A.; Kawasaki, S.; Nakashima, H.; Sato, K. N.; Zushi, H.; Hanada, K.; Sakamoto, A.; Idei, H., High accessible experimental information on CPD experiment, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2007.10.014, 83.0, 2.0, 402.0-405.0, 2008.04, On CPD [1] (Compact PWI experimental Device) experiment, information of electronic logbook and sequence status are distributed by Web services to prepare future experimental environment such as steady state operation and remote participation. Hence, all the researchers can acquire information with a Web browser installed on a personal computer if they are connected to the Internet. However, to carry a notebook computer all the time is a burden to researchers. Furthermore, the researchers may not be always connected to the Internet. Mobile phones are superior in portability compared to notebook computers, and are easy to connect with Internet through the wireless network of the telecom carriers. Moreover, since recent mobile phones have full browsing function, their affinities to the Web services are becoming high. On this account, Web services for mobile phones are developed to access experimental information. For sequence monitoring, a mobile application MIDlet that utilizes special functions of mobile phone such as sound and vibration is also developed to draw attentions of researchers to sequence status. (C) 2007 Elsevier B.V. All rights reserved..
267. Xu, Handong; Hanada, K.; Hasegawa, M.; Wang, M.; Shen, B.; Zushi, H.; Nakamura, K.; Sato, K. N.; Sakamoto, M.; Idei, H.; Bhattacharyay, R., The current control of steady-state plasma in TRIAM-1M and HT-7, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2008.01.018, 83.0, 2.0, 211.0-214.0, 0.0, 2008.04, Fully non-inductive lower hybrid current drive (LHCD) plasmas have been achieved in TRIAM-1M and HT-7 superconducting tokamaks, but the current control in toroidal plasma was performed in different way during their steady-state operation (SSO). In HT-7, the plasma current was controlled mainly by the ohmic field, and partially by LHCD through ohmic transformer magnetic flux feedback control. In TRIAM-1M, the plasma current was controlled by lower hybrid wave (LHW) power directly according to a simple simulation model. (c) 2008 Elsevier B.V. All rights reserved..
268. Tetsushi KIKUKAWA, Hideki ZUSHI, Tomohiro MORISAKI, Rajendraprasad BHATTACHARYAY, Tomofumi RYOUKAI, Tomokazu YOSHINAGA, Makoto HASEGAWA, Kazuaki HANADA, Hiroshi IDEI and CPD Experimental Group , Visualization of magnetic surfaces during current ramp-up phase using thermal Lithium sheet beam in CPD, Plasma and Fusion Research, 3.0, RC, Article No. 010, 2008.02, Two dimensional electron density profile measurement has been performed in the spherical tokamak CPD (Compact PWI experimental Device) using Li sheet beam imaging technique. The topological change from the open magnetic field line configuration to the closed one is visualized by this technique. The plasma current can be driven by RF waves itself in a weak mirror configuration and a clear change is observed in plasma boundary as well as magnetic field topology associated with the transition of the current from low (∼1 kA) to high (∼3 kA) value..
269. Bhattacharyay, R.; Zushi, H.; Morisaki, T.; Inada, Y.; Kikukawa, T.; Watanabe, S.; Sasaki, K.; Ryoukai, T.; Hasegawa, M.; Hanada, K.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Idei, H.; Yoshinaga, T.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Study of magnetic configuration effects on plasma boundary and measurement of edge electron density in the spherical tokamak compact plasma wall interaction experimental device using Li sheet beam, PHYSICS OF PLASMAS, 10.1063/1.2839034, 15.0, 2.0, 0.0-0.0, 022504, 2008.02, Two-dimensional lithium beam imaging technique has been applied in the spherical tokamak CPD (compact plasma wall interaction experimental device) to study the effects of magnetic field configurations on rf plasma boundary in the absence of any plasma current, and also for the measurement of a two-dimensional edge electron density profile. With the present working condition of the diagnostics, the minimum measured electron density can be similar to 1.0 X 10 16 m(-3); this is considered to be the definition for the plasma boundary. The performance of the lithium sheet beam is absolutely calibrated using a quartz crystal monitor. Experimental results reveal that magnetic field configuration, either mirror or so-called null, critically affects the rf plasma boundary. A sharp lower boundary is found to exist in magnetic null configuration, which is quite different from that in the weak mirror configuration. Theoretical calculations of particle drift orbit and. magnetic connection length (wall-to-wall) suggest that only mirror trapped particles are confined within a region where the magnetic connection length is similar to 4.0 in or more. A two-dimensional edge electron density profile is obtained from the observed Li I intensity profile. Overdense plasma formation is discussed from the viewpoint of mode conversion of rf wave into electron Bernstein wave and its dependence on the electron density profile. (c) 2008 American Institute of Physics..
270. Notake, Takashi; Shimozuma, Takashi; Kubo, Shin; IDEI, Hiroshi; IDA, Katsumi; YOSHINUMA, Mikirou; KOBUCHI, Takashi; WATANABE, Kiyomasa; INAGAKI, Shigeru; TOKUZAWA, Tokihiko; , Demonstration of Plasma Current Control by Using High Power Millimeter-Waves, Proceedings of ITC/ISHW2007, 4.0, 2008.01.
271. Ryoukai, Tomofumi; ZUSHI, Hideki; BHATTACHARYAY, Rajendraprasad; IDEI, Hiroshi; YOSHINAGA, Tomokazu; CPD, Group12; MORISAKI, Tomohiro; MUTOH, Takashi; KUBO, Shin; NAGASAKI, Kazuaki; , Field line tying and magnetic shear effects of the vertical magnetic field on low frequency density fluctuations in CPD, 14th Int. Congress on Plasma Phys., Fukuoka, Japan, 2008.01.
272. Shimozuma, T; Idei, H; Shapiro, MA; Temkin, RJ; Kubo, S; Yoshimura, Y; Igami, H; Takahashi, H; Notake, T; Ito, S; , Propagating mode analysis and field reconstruction in the corrugated waveguides of a high power electron cyclotron heating system, Infrared, Millimeter and Terahertz Waves, 2008. IRMMW-THz 2008. 33rd International Conference on, Article No. 41640, 2008.01.
273. Hasegawa, Makoto; Hanada, Kazuaki; Sato, Kohnosuke; Nakamura, Kazuo; Zushi, Hideki; Sakamoto, Mizuki; Idei, Hiroshi; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Initial plasma production by Townsend avalanche breakdown on QUEST tokamak, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.47.287, 47.0, 1.0, 287.0-292.0, 2008.01, On tokamak devices, an induction electric field induced by poloidal field (PF) coils plays a role to produce initial plasma. On a DIII-D tokamak, the required induction electric field for plasma breakdown agrees well with theoretical predictions based on the Townsend avalanche theory. According to the Townsend avalanche theory, the minimum induction electric field for plasma breakdown depends on neutral gas pressure and connection length. For stable plasma breakdown, a sufficiently large induction electric field is required. However, in the case of spherical tokamaks without electric insulation in the toroidal direction, the effect of eddy currents flowing in the toroidal direction should be considered in evaluating a feasible induction electric field because this effect suppresses the generation of an induction electric field. On a QUEST spherical tokamak, the possibility of Townsend avalanche breakdown is studied by evaluating the connection length and achievable induction electric field. The connection length is greater than 100 in in the case where a null point is set to be R = 0.56 in with a CS coil current of 2.0 kA and a PF26 coil current of 0.4 kA. Moreover, the induction electric field is about 1.5 V at this point including the effect of eddy currents. With these values, the initial plasma production by the induction electric field is sufficiently possible on QUEST..
274. , Takashi Notake, Takashi Shimozuma, Shin Kubo, Hiroshi Idei, Katsumi Ida, Kiyomasa Watanabe, Satoru Sakakibara, Taiki Yamaguchi, Mikirou Yoshinuma, Takashi Kobuchi, Shigeru Inagaki, Tokihiko Tokuzawa, Yasuo Yoshimura, Hiroe Igami, Tetsuo Seki, Hitoshi Tanaka, Kazunobu Nagasaki, First demonstration of rotational transform control by electron cyclotron current drive in large helical device, Plasma and Fusion Research, 10.1585/pfr.3.S1077, 3, 2008.01, [URL], An active current drive is a promising technique for improving plasma performances by controlling rotational transform and/or magnetic shear profiles in helical devices. A current drive based on electron cyclotron resonance heating is the most appropriate scheme for this purpose in terms of locality of driven current. Optimum conditions for an efficient electron cyclotron current drive (ECCD) in Large Helical Device (LHD) are being investigated using three-dimensional ray-tracing code, which can simulate propagation and power dissipation of electron cyclotron waves with large parallel refractive index. In the present experiment, inversion of directions of driven plasma current corresponding to injected ECCD modes was demonstrated successfully, and the results could be elucidated by the Fisch-Boozer theory. In addition, clear shifts of rotational transform were observed by motional Stark effect polarimetry. Our findings verified that the ECCD can be used as an effective actuator for controlling the rotational transform and magnetic shear profile in LHD..
275. Tetsushi Kikukawa, Hideki Zushi, Tomohiro Morisaki, Rajendraprasad Bhattacharyay, Tomofumi Ryoukai, Tomokazu Yoshinaga, Makoto Hasegawa, Kazuaki Hanada, Hiroshi Idei, Experimental Group CPD Experimental Group, Visualization of magnetic surfaces during current ramp-up phase using thermal lithium sheet beam in CPD, Plasma and Fusion Research, 10.1585/pfr.3.010, 3, 2008.01, [URL], Two dimensional electron density profile measurement has been performed in the spherical tokamak CPD (Compact PWI experimental Device) using Li sheet beam imaging technique. The topological change from the open magnetic field line configuration to the closed one is visualized by this technique. The plasma current can be driven by RF waves itself in a weak mirror configuration and a clear change is observed in plasma boundary as well as magnetic field topology associated with the transition of the current from low (~1 kA) to high (~3kA) value..
276. Hiroshi Idei, Shigeru Inagaki, Shohji Kawasaki, Hideki Zushi, Yoshio Nagayama, Kazuo Kawahata, Takashi Shimozuma, Yuichi Wataya, Broadband radiometer system with fast frequency switching synthesizer for electron cyclotron emission measurements in LHD, Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics, IRMMW-THz2007
IRMMW-THz2007 - Conference Digest of the Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics
, 387-388, 2007.12, The broadband fast frequency-switching heterodyne radiometers have been developed to measure simultaneously three-band components of electron cyclotron emission with high time and frequency resolutions in the large helical device (LHD). The fast frequency-switching system was prepared as a local oscillator part of the heterodyne radiometers. The frequency switching time was 10 μs. The fundamental electron cyclotron emission spectrum was successfully measured using the radiometer in the LHD experiment..
277. Hiroshi Idei, Minoru Kawaguchi, Masatsugu Sakaguchi, Yasumasa Tanaka, Satoshi Ito, Design of phased array antenna system for electron Bernstein wave heating and current drive in QUEST, Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics, IRMMW-THz2007
IRMMW-THz2007 - Conference Digest of the Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics
, 789-790, 2007.12, The phased array antenna system has been designed for electron Bernstein wave heating and current drive in the QUEST tokamak at 8.2 GHz. In order to control the launching polarization state, an orthomode transducer was designed to mix two orthogonal electric field components. The polarization state was arbitrarily controlled using phase difference and intensity ratio between the two field components. The fields radiated from the phased array antenna were evaluated using the Kirchhoff integral and HFSS codes. New designed phased array antenna steered a radiated beam to the desired launching-direction by the phased array..
278. Hiroshi Idei, Shouji Kawasaki, Kazuaki Hanada, Hideki Zushi, Kohnosuke Sato, Kazuo Nakamura, Mizuki Sakamoto, Makoto Hasegawa, Hisatoshi Nakashima, Aki Higashijima, Yuichi Wataya, Shinji Matsubara, Shuhei Kawano, Initial results of AM reflectometory on CPD, Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics, IRMMW-THz2007
IRMMW-THz2007 - Conference Digest of the Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics
, 518-519, 2007.12, The amplitude modulation reflectometer system has been developed to measure the density profile in detail on the Compact PWI ( plasma-wall interaction ) Device (CPD) experiments. The probing frequency range was 6-18 GHz, and its frequency-switching time was 10 μs in an arbitrary step. Using the broadband fast-scanning reflectometer, the wide-range density profile can be measured with high time resolution. In X-mode reflectometory, the developed system successfully measured the phase delay of propagating waves at 6.6, 8.8 and 13.2 GHz, reflected at the vessel wall of the CPD and the R-cutoff layers in the CPD plasma..
279. Hiroshi Idei, Michael Shapiro, Richard J. Temkin, Takashi Shimozuma, Shin Kubo, Mode content analysis in circular corrugated waveguide using radiated field, Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics, IRMMW-THz2007
IRMMW-THz2007 - Conference Digest of the Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics
, 69-70, 2007.12, The fields radiated from the waveguide were used to analyze propagating mode content in an oversized circular corrugated waveguide. The radiated fields were calculated by the Kirchhoff Integral in the paraxial approximation. The irradiant waveguide modes of the radiated field are orthogonal within the paraxial approximation. The waveguide mode content was evaluated from the irradiant waveguide modes. The radiated intensity and phase profiles were directly measured with a vector network analyzer system at 84GHz for the analysis. The analyzed waveguide mode content was consistent with that excited in the waveguide, predicted by the coupling theory..
280. Kazuaki HANADA, Keisuke SASAKI, Makoto HASEGAWA, Hiroshi IDEI, Hideki ZUSHI, Kazuo NAKAMURA, Mizuki SAKAMOTO, Konosuke SATO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA and TRIAM group, Current profile estimation in full LHCD plasmas using Hard X-ray measurement along the top and bottom identical line of sight on TRIAM-1M, Plasma and Fusion Research, 2.0, RA, 4.0, Article No. S1071, 2007.11, A new technique to measure the current profile in plasmas with asymmetric distribution function such as lower hybrid current drive (LHCD) by using hard X-ray (HXR) energy spectrum measurement along the top and bottom identical line of sights (ILOS) is proposed and is applied to the full and partially LHCD plasmas on the TRIAM-1M tokamak at the first time in the world. The pitch angles were measured at R - R0 = ±2.5 cm, where R, R0 mean the major radii of the ILOS and the magnetic axis, respectively. The measured pitch angle of the magnetic field inverted at the magnetic axis estimated magnetic measurement in partially LHCD plasmas. This indicates that the difference of the measured pitch angles is caused by the plasma current in the plasma and this new method is available in detecting the current profile in tokamaks. In full LHCD plasma, no difference between the HXR signals along the top and bottom ILOS appear. This indicates that the current density around the magnetic axis was reduced compared with that in partially LHCD plasmas. This observation is no contradiction with power deposition of LHCD..
281. Sakamoto, M; Sato, KN; Zushi, H; Nakamura, K; Hanada, K; Idei, H; Hasegawa, M; Kawasaki, S; Nakashima, H; Higashijima, A; , Steady state plasma operation in the superconducting tokamak TRIAM-1M and the QUEST project, Proc. of Int. Symposium on Eco Topia Science, Pages 314-317, 2007.11.
282. R. BHATTACHARYAY, H. ZUSHI, T. MORISAKI, K. KIKUKAWA, S. WATANABE, Y. INADA, M. HASEGAWA, H. TSUCHIYA, K. N. SATO, K. NAKAMURA, M. SAKAMOTO, H. IDEI, K. SASAKI, H. XU, F. WANG, S. KAWASAKI, H. NAKASHIMA and A. HIGASHIJIMA, Two Dimensional Li Beam Imaging to Study the Magnetic Field Configuration Effects on Plasma Confinement in Spherical Tokamak CPD, Plasma and Fusion Research, 2.0, RA, Article No. S1103, 2007.11, Two dimensional lithium beam imaging technique has been applied in the spherical tokamak, CPD (Compact Plasma wall interaction experimental Device), to study the effects of various magnetic field configurations on RF plasma confinement topology. The performance of the lithium sheet beam is absolutely calibrated by a quartz crystal monitor. Experimental results show that plasma initiation takes place at the electron cyclotron resonance layer in a simple torus configuration and then it expands quickly to the low magnetic field side. Different magnetic field configurations critically affect the RF plasma confinement topology. A sharp lower boundary exists for the RF plasma in magnetic null configuration. Magnetic connection length plays the key role in defining plasma boundary and the critical value of connection length for plasma to exist in CPD is found to be ∼ 5-6 meter for a given pressure condition..
283. Idei, Hiroshi; Kawasaki, Shohji; Zushi, Hideki; Inagaki, Shigeru; Nagayama, Yoshio; Kawahata, Kazuo; Wataya, Yuichi, Broadband radiometer system with fast frequency switching synthesizer for electron cyclotron emission measurements in LHD, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 380.0-381.0, 0.0, 2007.09, The broadband fast frequency-switching heterodyne radiometers have been developed to measure simultaneously three-band components of electron cyclotron emission with high time and frequency resolutions in the large helical device (LHD). The fast frequency-switching system was prepared as a local oscillator part of the heterodyne radiometers. The frequency switching time was 10 mu s. The fundamental electron cyclotron emission spectrum was successfully measured using the radiometer in the LHD experiment..
284. Idei, Hiroshi; Kawasaki, Shouji; Hanada, Kazuaki; Zushi, Hideki; Sakamoto, Kohnosuke Sato Kazuo Nakamura Mizuki; Hasegawa, Makoto; Nakashima, Hisatoshi; Higashijima, Aki; Wataya, Yuichi; Matsubara, Shinji; Kawano, Shuhei, Initial results of AM reflectometory on CPD, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 0.0, 0.0, 518.0-519.0, 2007.09, The amplitude modulation reflectometer system has been developed to measure the density profile in detail on the Compact PWI ( plasma-wall interaction) Device (CPD) experiments. The probing frequency range was 6-18 GHz, and its frequency-switching time was 10 mu s in an arbitrary step. Using the broadband fast-scanning reflectometer, the wide-range density profile can be measured with high time resolution. In X-mode reflectometory, the developed system successfully measured the phase delay of propagating waves at 6.6, 8.8 and 13.2 GHz, reflected at the vessel wall of the CPD and the R-cutoff layers in the CPD plasma..
285. Bhattacharyay, R.; Zushi, H.; Nakashima, K.; Shikama, T.; Sakamoto, M.; Yoshida, N.; Kado, S.; Sawada, K.; Hirooka, Y.; Nakamura, K.; Hanada, K.; Idei, H.; Hasegawa, M.; Sato, K. N.; Ogawa, M.; Takaki, O.; Sasaki, K.; Xu, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A., A study on temperature effects on hydrogen recycling and molybdenum impurity emission from a movable limiter in TRIAM-1M Tokamak, NUCLEAR FUSION, 10.1088/0029-5515/47/8/018, 47.0, 8.0, 864.0-874.0, 2007.08, In order to investigate the surface temperature effects on plasma fuel recycling and impurity release from the plasma facing components, plasma discharges have been performed under selected plasma-wall interaction (PWI) conditions in the high-field superconducting tokamak, TRIAM-1M. By moving a water-cooled molybdenum movable limiter (ML) beyond the last closed flux surface, as defined by poloidal limiters, the surface temperature profile on it is varied. Hot spots have been observed on the ML surface in such conditions. The release behaviour of fuel as well as impurity particles from the ML surface has been studied as a function of hot spot temperature (T-hot) by means of wide range spectroscopy (200-1600 nm). A critical Thot is found to be similar to 2100 K above which the emission of both hydrogen and impurity particles enhances significantly. This is indicative of some thermally activated process playing an important role in PWIs between the limiter and the edge plasma. With the rise in hot spot temperature localized PWI at the ML is found to dominate the global recycling even when external fuelling is stopped..
286. Zushi, H.; Hanada, K.; Idei, H.; Hasegawa, M.; Sasaki, K.; Bhattacharyay, R.; Sakamoto, M.; Nakamura, K.; Sato, K. N.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Electron cyclotron counter current drive experiments in lower hybrid current drive plasma in TRIAM-1M, FUSION SCIENCE AND TECHNOLOGY, 52.0, 2.0, 240.0-249.0, 0.0, 2007.08, Combined experiments with lower hybrid (LH) waves (LHWs) and electron cyclotron (EC) waves (ECWs) have been performed to study counter (ctr) current drive (CD) (ctr-CD) in LHCD plasma. Although there exists a large spectrum gap under the condition of the forward (FW) LHCD at high ratio (> 13) of the thermal velocity and the phase velocity, the relativistic Doppler resonance for backward (BW) ECWs coupled with the energetic electrons streaming along the current direction is used to confirm that the gap in the opposite velocity region is also filled by BW LHWs and the counter current tends to be driven. Three experimental scenarios have been studied for ctr-CD by the following experiments: (a) BW-LHW injection into FW LHW, (b) BW-ECW injection into FW LHW, and (c) BW-ECW injection into bidirectional BW-LHCD and FW-LHCD plasma. A transition depending on the power ratio is observed in case (a). The Ohkawa current is discussed for the co-driven current observation for case (b). The role of the amount of the resonance electrons is understood as a function of the power ratio of BW LHW to FW LHW for case (c)..
287. Hasegawa, Makoto; Hanada, Kazuaki; Sato, Kohnosuke; Nakamura, Kazuo; Zushi, Hideki; Sakamoto, Mizuki; Idei, Hiroshi; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Model of inductive plasma production assisted by radio-frequency wave in tokamaks, JOURNAL OF NUCLEAR MATERIALS, 10.1143/JPSJ.76.084501, 76.0, 8.0, 0.0-0.0, 084501, 2007.08, For initial plasma production, an induction electric field generated by applying voltage to a poloidal field (PF) coil system is used to produce a Townsend avalanche breakdown. When the avalanche margins are small, as for the International Thermonuclear Experimental Reactor (ITER) in which the induction electric field is about 0.3 V/m, the assistance of radio-frequency waves (RF) is provided to reduce the induction electric field required for reliable breakdown. However, the conditions of RF-assisted breakdown are not clear. Here, the effects of both RF and induction electric field on the RF-assisted breakdown are evaluated considering the electron loss. When traveling loss is the dominant loss, a simple model of an extended Townsend avalanche is proposed. In this model, the induction electric field required for RF-assisted breakdown can be decreased to half that required for induction breakdown..
288. Hanada, K.; Shinoda, N.; Sugata, T.; Sasaki, K.; Zushi, H.; Nakamura, K.; Sato, K. N.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Calorimetric measurement of heat load in full non-inductive LHCD plasmas on TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.255, 363.0, 1425.0-1428.0, 2007.06, Calorimetric measurements using the temperature increment of cooling-water were carried out to estimate the heat load distribution on the plasma facing components (PFCs) in the limiter discharges on TRIAM-1M. Line averaged electron density, n(e), and LH power, P-LH, dependences of the heat load on PFCs were measured. The heat load on the limiters was proportional to n(e)(1.5) in the range of n(e) = 0.2-1.0 x 10(19) m(-3) and P-LH(I) in the range of P-LH = 0.005-0.09 MW. For P-LH > 0.1 MW, the plasma transition to an enhanced current drive (ECD) mode appeared and the n(e) dependences on the heat load on the limiter moderated. This indicates that the heat flux to scrape-off layer (SOL) region was reduced due to the improvement of the plasma confinement. The up-down asymmetry of the heat load on the vacuum vessel was enhanced in the ECD mode, which may be caused by the increasing of the direct loss of energetic electrons. (c) 2007 Elsevier B.V. All rights reserved..
289. Ogawa, M.; Sakamoto, M.; Sato, K. N.; Zushi, H.; Nakamura, K.; Hanada, K.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Difference in oxygen impurity behavior between repetitive short discharges and one long discharge on TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.238, 363.0, 0.0, 1364.0-1368.0, 2007.06, Oxygen impurity behaviors of one long duration discharge and repetition of short duration discharges have been investigated in TRIAM-1M. In the former case, the OII line intensity divided by the line averaged electron density, which is considered as a monitor of oxygen concentration on the plasma facing surface (PFS), decreased with the time constant, tau(d), of 30-50 s during the discharge due to the hydrogen flux to PFS. In the latter case, tau(d) is in the range of 70-600 s. There exists a big difference of global behavior of oxygen impurity between both cases. The difference seems to result from the absence or presence of the interval time between the discharges. The oxygen concentration on PFS increases during the interval time due to adsorption of H2O. The time constant of the increase in the oxygen concentration is evaluated to be about 5500 s from Langmuir adsorption isotherms analysis. (c) 2007 Elsevier B.V. All rights reserved..
290. Sakamoto, M.; Ogawa, M.; Zushi, H.; Higashijima, A.; Nakashima, H.; Kawasaki, S.; Hasegawa, M.; Idei, H.; Hanada, K.; Nakamura, K.; Sato, K. N., In situ measurements of erosion and redeposition during long duration discharges on TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.055, 363.0, 0.0, 233.0-237.0, 2007.06, An in situ and real time measurement system of erosion and deposition has been developed, which is based on interference of light on a thin semi-transparent layer of redeposited material on substrate. It has been applied to long duration discharges in TRIAM-1M. The sapphire window is used as substrate. The deposition pattern on the window indicates up down and toroidal asymmetry. In the 5 h 16 min discharge, the thickness of the deposited layer increased monotonically with time and its deposition rate is similar to 1.5 x 10(16) Mo m(-2) S-1. In the low density and long duration discharge, the Mo deposition rate on the window depends on the ratio of Mo flux to hydrogen flux. (c) 2007 Elsevier B.V. All rights reserved..
291. Zushi, H.; Nozaki, Y.; Bhattacharyay, R.; Nakashima, K.; Sakamoto, M.; Hanada, K.; Idei, H.; Nakamura, K.; Sato, K. N.; Nishi, S.; Ogawa, M.; Takaki, K.; Sasaki, K.; Hirooka, Y.; Hasegawa, M.; Xu, H.; Kado, S.; Shikama, T.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Relation between charge exchange flux and impurity influx studied by perturbation methods of gas puffing, heat load and confinement properties in TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.201, 363.0, 0.0, 1386.0-1394.0, 2007.06, A diagnostic technique to study the global structure of the recycling and impurity (molybdenum) influx from the plasma facing components is proposed and is tested using the three kinds of perturbations (gas puffing, transport oscillation, and localized heat deposition). Balmer line intensities I-H alpha, charge exchange flux Gamma(CX) and neutral molybdenum line I-Mol are measured and their correlations are analyzed with response to the perturbation parameters (I-H alpha at the gas port, density n(e), and hot spot temperature T-hot). A simple model calculation is done to understand these correlations. It is found that the phase reversal of Gamma(CX) with respect to n(e) modulation is well reproduced and a critical density exists for the phase reversal of I-Mol. The evaporation Mo flux evaluated with measured T-hot is also compared with enhanced I-Mol for the heat load perturbation and it contribution to the total content of Mo ions is evaluated by similar to 30% increment. (c) 2007 Elsevier B.V. All rights reserved..
292. Bhattacharyay, R.; Zushi, H.; Nakashima, K.; Shikama, T.; Sakamoto, M.; Ogawa, M.; Nakamura, K.; Yoshida, N.; Kado, S.; Sawada, K.; Hirooka, Y.; Hanada, K.; Sato, K. N.; Idei, H.; Sasaki, K.; Xu, H.; Hasegawa, M.; Uehara, K.; Tsushima, A.; Kimura, N.; Nozaki, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Surface temperature effects on hydrogen and impurity release from the limiter studied by means of visible and near infrared spectroscopic measurement in TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.117, 363.0, 0.0, 938.0-943.0, 2007.06, Tokamak operation has been performed under the localized plasma wall interaction conditions in TRIAM-1M, using a water cooled rail movable limiter (ML) made of Molybdenum. The limiter surface temperature dependence on hydrogen recycling and neutral molybdenum impurity production behaviour has been studied using visible as well as infrared spectroscopy during low power long pulse and high power short pulse discharges. In these experiments it is considered that escaped energetic electrons are lost mainly on ML and localised heat deposition makes a 'hot spot' on ML. It has been observed that H-2, H-alpha and MoI intensities critically depend on the hot spot temperature (T-hot) and enhanced recycling due to localized PWI on ML can fuel the discharge without any external fueling source. (c) 2007 Elsevier B.V. All rights reserved..
293. Sasaki, K.; Hanada, K.; Nishino, N.; Tokitani, M.; Yoshida, N.; Sato, K. N.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakasihma, H.; Higashijima, A., The observation of dust behavior in TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.199, 363.0, 0.0, 238.0-241.0, 2007.06, The observation of dusts in plasmas was carried out by high speed camera in full non-inductive lower hybrid current drive (LHCD) plasma on TRIAM-1M. The velocities of dusts were 10-50 m/s. The number of dust generated per second increased with the discharge duration in the range of 20-57 s. This suggests that a part of dusts were generated from a movable limiter whose the surface temperature increases with the discharge duration. Dusts were coming from various directions even close to the movable limiter. Dusts were collected in the vacuum vessel by use of a kind of cleaner and the composition and the size of dust were examined by Scanning Electron Microscope (SEM). Dust size was several mu m and composition was Molybdenum mixed with small amount of elements of stainless metal. The poloidal distribution of the collected mass of dusts was almost uniform. (c) 2007 Published by Elsevier B.V..
294. Zushi, H.; Morisaki, T.; Inada, Y.; Bouchard, J.; Nakashima, K.; Tsuchiya, H.; Hanada, K.; Sasaki, K.; Bhattacharyay, R.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A., Two-dimensional density profile measurement with a sheet thermal Li beam on CPD, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2007.01.259, 363.0, 0.0, 1429.0-1435.0, 2007.06, A sheet thermal Li beam to study the density contour near X-point and divertor strike points has been developed for the spherical tokamak CPD. The CCD camera with a time resolution of 1 ms and spatial resolution of similar to 1 mm can record two-dimensional images of LiI resonance line (300 mm x 500 mm). The performance of the sheet beam is absolutely calibrated by a quartz crystal monitor. The Li flux of 10(18)-10(19) m(-2) s(-1) is achieved near the X-point. The sheet characteristics of beam width and uniformity are also confirmed. This technique is applied during plasma initiation and electron cyclotron heating phase of plasma in a simple torus with a small vertical field. The formation of vertically stretched plasma at the position of the cyclotron resonance is clearly found. The expansion process towards the low field side is observed and an over dense plasma (> 1 x 10(18) m(-3)) is obtained. A model calculation of LiI emission with density range of 1-5 x 10(18) m(-3) agrees fairly well with the observations. Over dense plasma formation is also discussed. (c) 2007 Elsevier B.V. All rights reserved..
295. Idei, Hiroshi; Kawaguchi, Minoru; Sakaguchi, Masatsugu; Tanaka, Yasumasa; Ito, Satoshi; , Design of phased array antenna system for electron bernstein wave heating and current drive in QUEST, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 0.0, 0.0, 789.0-790.0, 0.0, 2007.04, The phased array antenna system has been designed for electron Bernstein wave heating and current drive in the QUEST tokamak at 8.2 GHz. In order to control the launching polarization state, an orthomode transducer was designed to mix two orthogonal electric field components. The polarization state was arbitrarily controlled using phase difference and intensity ratio between the two field components. The fields radiated from the phased array antenna were evaluated using the Kirchhoff integral and HFSS codes. New designed phased array antenna steered a radiated beam to the desired launching-direction by the phased array..
296. Idei, Hiroshi; Shapiro, Michael; Temkin, Richard J.; Shimozuma, Takashi; Kubo, Shin, Mode content analysis in circular corrugated waveguide using radiated field, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 0.0, 0.0, 69.0-70.0, 0.0, 2007.04, The fields radiated from the waveguide were used to analyze propagating mode content in an oversized circular corrugated waveguide. The radiated fields were calculated by the Kirchhoff Integral in the paraxial approximation. The irradiant waveguide modes of the radiated field are orthogonal within the paraxial approximation. The waveguide mode content was evaluated from the irradiant waveguide modes. The radiated intensity and phase profiles were directly measured with a vector network analyzer system at 84GHz for the analysis. The analyzed waveguide mode content was consistent with that excited in the waveguide, predicted by the coupling theory..
297. Makoto HASEGAWA, Kazuaki HANADA, Kohnosuke SATO, Kazuo NAKAMURA, Hideki ZUSHI, Mizuki SAKAMOTO, Hiroshi IDEI, Shoji KAWASAKI, Hisatoshi NAKASHIMA and Aki HIGASHIJIMA , Townsend Avalanche Breakdown Assisted by Radio Frequency Wave in Tokamaks, Plasma and Fusion Research, 2.0, RC, Article No. 007, 2007.03.
298. Kazuaki Hanada, Keisuke Sasaki, Makoto Hasegawa, Hiroshi Idei, Hideki Zushi, Kazuo Nakamura, Mizuki Sakamoto, Konosuke Sato, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, group Triam group, Current profile estimation in full LHCD plasmas using hard X-ray measurement along the top and bottom identical line of sight on TRIAM-1M, Plasma and Fusion Research, 10.1585/pfr.2.S1071, 2, 2007.01, [URL], A new technique to measure the current profile in plasmas with asymmetric distribution function such as lower hybrid current drive (LHCD) by using hard X-ray (HXR) energy spectrum measurement along the top and bottom identical line of sights (ILOS) is proposed and is applied to the full and partially LHCD plasmas on the TRIAM-1M tokamak at the first time in the world. The pitch angles were measured at R - R0 = ±2.5cm, where R, R0 mean the major radii of the ILOS and the magnetic axis, respectively. The measured pitch angle of the magnetic field inverted at the magnetic axis estimated magnetic measurement in partially LHCD plasmas. This indicates that the difference of the measured pitch angles is caused by the plasma current in the plasma and this new method is available in detecting the current profile in tokamaks. In full LHCD plasma, no difference between the HXR signals along the top and bottomILOS appear. This indicates that the current density around the magnetic axis was reduced compared with that in partially LHCD plasmas. This observation is no contradiction with power deposition of LHCD..
299. H. Zushi, Kazuaki Hanada, Hiroshi Idei, Makoto Hasegawa, K. Sasaki, R. Bhattacharyay, M. Sakamoto, Kazuo Nakamura, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, Electron cyclotron counter current drive experiments in lower hybrid current drive plasma in triam-1m, Fusion Science and Technology, 10.13182/FST07-A1503, 52, 2, 240-249, 2007.01, [URL], Combined experiments with lower hybrid (LH) waves (LHWs) and electron cyclotron (EC) waves (ECWs) have been performed to study counter (ctr) current drive (CD) (ctr-CD) in LHCD plasma. Although there exists a large spectrum gap under the condition of the forward (FW) LHCD at high ratio (>13) of the thermal velocity and the phase velocity, the relativistic Doppler resonance for backward (BW) ECWs coupled with the energetic electrons streaming along the current direction is used to confirm that the gap in the opposite velocity region is also filled by BW LHWs and the counter current tends to be driven. Three experimental scenarios have been studied for ctr-CD by the following experiments: (a) BW-LHW injection into FW LHW, (b) BW-ECW injection into FW LHW, and (c) BW-ECW injection into bidirectional BW-LHCD and FW-LHCD plasma. A transition depending on the power ratio is observed in case (a). The Ohkawa current is discussed for the co-driven current observation for case (b). The role of the amount of the resonance electrons is understood as a function of the power ratio of BW LHW to FW LHW for case (c)..
300. F. Wang, K. Nakamura, O. Mitarai, K. Kurihara, Y. Kawamata, M. Sueoka, K. N. Sato, H. Zushi, K. Hanada, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, Plasma shape reconstruction of spherical tokamak using CCS method, Plasma and Fusion Research, 10.1585/pfr.2.S1095, 2, 2007.01, [URL], Plasma shape reconstruction is important for plasma control of tokamak. Cauchy-Condition Surface (CCS) method is a numerical approach to reproduce plasma shape which has good precision in conventional tokamak. In order to apply it in the plasma shape reproduction of Compact PWI experimental Device (CPD) which is a new spherical tokamak in Kyushu University, the calculation precision of CCS method in CPD is analyzed in the paper..
301. Makoto Hasegawa, Kazuaki Hanada, Kohnosuke Sato, Kazuo Nakamura, Hideki Zushi, Mizuki Sakamoto, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Townsend avalanche breakdown assisted by radio frequency wave in tokamaks, Plasma and Fusion Research, 10.1585/pfr.2.007, 2, 2007.01, [URL], A simple model of radio frequency wave (RF) assisted breakdown based on Townsend avalanche theory is proposed for the purpose of evaluating the effect of RF on Townsend avalanche breakdown. According to this model, the required minimum electric field for RF-assisted breakdown can be decreased down to half of that for breakdown by the induction electric field alone. The electric field of RF reaches a minimum when the frequency of the RF is equal to the electron cyclotron frequency..
302. R. Bhattacharyay, H. Zushi, T. Morisaki, K. Kikukawa, S. Watanabe, Y. Inada, M. Hasegawa, H. Tsuchiya, K. N. Sato, K. Nakamura, M. Sakamoto, H. Idei, K. Sasaki, H. Xu, F. Wang, S. Kawasaki, H. Nakashima, A. Higashijima, Two dimensional Li beam imaging to study the magnetic field configuration effects on plasma confinement in spherical tokamak CPD, Plasma and Fusion Research, 10.1585/pfr.2.S1103, 2, 2007.01, [URL], Two dimensional lithium beam imaging technique has been applied in the spherical tokamak, CPD (Compact Plasma wall interaction experimental Device), to study the effects of various magnetic field configurations on RF plasma confinement topology. The performance of the lithium sheet beam is absolutely calibrated by a quartz crystal monitor. Experimental results show that plasma initiation takes place at the electron cyclotron resonance layer in a simple torus configuration and then it expands quickly to the lowmagnetic field side. Different magnetic field configurations critically affect the RF plasma confinement topology. A sharp lower boundary exists for the RF plasma in magnetic null configuration. Magnetic connection length plays the key role in defining plasma boundary and the critical value of connection length for plasma to exist in CPD is found to be ~ 5-6 meter for a given pressure condition..
303. K. Hanada, K. Sasaki, M. Hasegawa, H. Idei, H. Zushi, K. Nakamura, M. Sakamoto, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, Current profile estimation using Hard X-ray measurement along the top and bottom identical line of sight on TRIAM-1M, 33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006
33rd EPS Conference on Plasma Physics 2006, EPS 2006 - Europhysics Conference Abstracts
, 1608-1611, 2006.12, A new technique to measure the current profile in lower hybrid current drive (LHCD) plasmas by using hard X-ray (HXR) energy spectrum measurement along the top and bottom identical line of sight (ILOS) is proposed. An angle between ILOS and the magnetic filed line is out of alignment from the perpendicular by the poloidal magnetic field. As the emission cross-section of HXR strongly depends on the angle to the drift direction of energetic electrons, that is the magnetic filed line, this disagreement of the angles makes significant difference between the signals of detectors located on the top and bottom. As the result, the poloidal magnetic field is able to be derived from the difference of the HXR emission along the top and bottom ILOS. The method was applied to the full LHCD plasmas on the TRIMA-1M tokamak and the plasma current around the magnetic axis was estimated..
304. H. Zushi, R. Bhattacharyay, M. Sakamoto, Y. Nozaki, K. Nakashima, M. Ogawa, K. Takaki, K. Hanada, H. Idei, K. Nakamura, K. Sasaki, Y. Hirooka, Y. Nakashima, S. Kado, T. Shikama, Dynamics of recycling processes responding to the local particle and heat load perturbations on TRIAM-1M, 33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006
33rd EPS Conference on Plasma Physics 2006, EPS 2006 - Europhysics Conference Abstracts
, 1604-1607, 2006.12, A new diagnostic technique to study the global structure of the recycling among the plasma facing components PFCs has been proposed and tested using the three kinds of perturbations (gas puffing, transport oscillation, and localized heat deposition) at the frequency less than a few Hz . Hα intensities are measured at various toroidal and poloidal positions and FFT analysis shows that the propagation velocity of the neutral hydrogen in the toroidal direction is < 25 m/s for the gas puff modulation. For toroidally uniform transport oscillations, on the other hand, in-out asymmetry of recycling structure is found. The localized heat deposition causes the localized particle source distribution in the torus due to enhanced efflux of the hydrogen particles only fueled from the hot area..
305. K. Sasaki, K. Hanada, K. N. Sato, H. Zushi, K. Nakamura, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, T. Nakashima, A. Higashijima, Y. Takase, A. Ejiri, S. Shiraiwa, H. Kasahara, T. Yamada, N. Nishino, Soft X-ray measurement in IRE on the TST-2 spherical tokamak, 33rd European Physical Society Conference on Plasma Physics 2006, EPS 2006
33rd EPS Conference on Plasma Physics 2006, EPS 2006 - Europhysics Conference Abstracts
, 1640-1643, 2006.12, Internal Reconnection Event (IRE) is a characteristic relaxation phenomenon in STs (Sperical Tokamaks). To investigate the deformation of the plasma shape during IRE, four PIN diode arrays of 20 channels were installed on the TST-2@K (TST-2 at Kyushu University). Precursor of IRE was observed for several milli-seconds. The fluctuation was composed of two dominant components in frequency of 10kHz and 4kHz. The mode structure of 10kHz component is n/m=1/1 helical structure and 4kHz is n/m= 3/4. The overlap of modes (10kHz and 4kHz) was considered to be cause of IRE in TST-2 from the position and the growth of the modes..
306. K. Nakashima, H. Zushi, N. Maezono, M. Sakamoto, N. Yoshida, Kazutoshi Tokunaga, Y. Hirooka, T. Shikama, S. Kado, N. Nishino, Y. Nakahima, Kazuaki Hanada, K. Sasaki, Hiroshi Idei, A. Iyomasa, S. Kawasaki, K. N. Sato, H. Nakashima, Kazuo Nakamura, Makoto Hasegawa, A. Higashijima, Surface temperature dependence of hydrogen balmar and molybdenum neutral lines from the Mo limiter in TRIAM-1M, 21st IEEE/NPS Symposium on Fusion Engineering, SOFE'05
21st IEEE/NPS Symposium on Fusion Engineering, SOFE'05
, 10.1109/FUSION.2005.252980, 2006.12, [URL], The limiter surface temperature dependence on hydrogen recycling and molybdenum impurity production behavior was studied with optical spectroscopy during long pulse plasma discharges in TRIAM-1M. It has been observed that the H α intensity critically depends on the limiter surface temperature. The Mo-I intensity from the hot spot has shown a negative temperature dependence. This is believed to be due to the reduction of heat load and enhanced CX flux due to ion temperature rise..
307. Y. Wataya, H. Idei, S. Inagaki, T. Shimozuma, Y. Nagayama, K. Kawahata, H. Zushi, Wide-band heterodyne-radiometer with fast frequency-switching local oscillator for electron cyclotron emission diagnostics, IRMMW-THz 2006 - 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics
IRMMW-THz 2006 - 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics
, 10.1109/ICIMW.2006.368709, 2006.12, [URL].
308. Yuichi Wataya, H. Idei, H. Zushi, TRIAM group, Development of Heterodyne Radiometer for Electron Cyclotron Emission (ECE) Measurement System using Harmonic Local Oscillator in High Frequency mm-wave range, Proc. of the 7th Cross Straits Symposium on Materials,Energy,and Environmental Sciences, (※), 2006.11.
309. Idei, Hiroshi; Shimozuma, Takashi; Shapiro, Michael A.; Notake, Takashi; Kubo, Shin; Temkin, Richard J., Experimental verification of phase retrieval of quasi-optical millimeter-wave beams, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, 10.1109/TMTT.2006.884632, 54.0, 11.0, 3899.0-3905.0, 2006.11, The accuracy of a phase-retrieval procedure for microwave beams was analyzed and verified using an 84-GHz quasi-optical beam transmitted by a corrugated waveguide. The output intensity and phase profiles of the beam were directly measured with a microwave receiver. The beam intensity was also measured at several planes and the data were used with a phase-retrieval algorithm to yield an independent estimate of the phase. Moment and matching coefficient methods were used to analyze the retrieved profiles. In the higher order moment analysis, the intensity profiles, which were calculated from the retrieved phase profiles, coincided well with the measured profiles in terms of the beam size, asymmetric property (skewness), and flatness/peakedness (kurtosis) over the entire profile. Analysis indicated that the mode content of the beam obtained by phase retrieval matched that of the direct measurement with a matching coefficient of 0.97 using both the intensity and phase profiles..
310. H. Zushi, K. Hanada, H. Idei, S. Nishi, T. Maekawa, M. Azumi, A. Fukuyama, S. Kubo, T. Shimozuma, T. Notake, K. Sasaki, B. Bhattacharyay, K. Nakashima, H. Hoshika, M. Sakamoto, M. Ogawa, K. Nakamura, K. N. Sato, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, K. Toi, Y. Takase, T. Shikama, S. Kado, O. Mitarai, K. Takahashi, K. Takaki, N. Maezono, M. Kitaguch, F. Wang, H. Xu, Y. Nozaki, Y. Wataya, N. Kimura, Bi-directional Lower Hybrid Current Drive and Electron Cyclotron Counter Current Drive Experiments in Full Current Drive Plasma in TRIAM-1M, Proc. 21th IAEA Fusion Energy Conference,Chengdu,China,16-21 October 2007, (※), 2006.10, In order to investigate the spectrum gap problem in LHCD and controllability for the current profile by means of counter current drive in full current drive plasma, experiments by combination of backward (BW) propagating LHW and/or ECW have been performed in a plasma sustained by forward (FW) propagating LHW. Three ctr-CD aspects have been investigated for relativistic resonance with respect to the power ratio of backward (PBW) to forward (PFW) LHWs; 1) a clear reduction of co-ICD for PBW/PFW < 0.8; 2) a rapid positive change in co-ICD and broadening in j(r) for PBW/PFW > 0.8 [H. Zushi et al., Nucl. Fusion 41 (2001) 1483]; and 3) a large positive change in co-ICD by ctr ECW into FW LHCD plasma and further changes to negative value in co-ΔICD depending on PBW/PFW of LHW..
311. M. Sakamoto, M. Ogawa, H. Zushi, K. Takaki, M. Tokitani, K. Tokunaga, N. Yoshida, Y. Higashizono, Y. Nakashima, K. Nakamura, K. Hanada, K. N. Sato, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, T. Fujiwara, A. Higashijima, T. Shikama, S. Kado, A. Tsushi, Multiscale Phenomena of Plasma-Wall Interaction in Long Duration Discharges on TRIAM-1M, 21st IAEA Fusion Energy Conference, 16-21,EX/P4-25, 2006.10.
312. K. N. Sato, H. Zushi, K. Nakamura, K. Hanada, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, D. Thang, F. Wang, I. Rego, K. Sasaki, H. Xu, B. Rajendraprasad, M. Ogawa, K. Takagi, K. Nakashima, S. Nishi, T. Aoki, N. Kimura, Y. Inada, Y. Nozaki, Y. Wataya, H. Sakai, M. Matsubara, S. Watanabe, K. Goto, Y. Miyoshi, N. Yoshida, K. Tokunaga, T. Fujiwara, M. Miyamoto, M. Tokitani, K. Uehara, Y. Sadamoto, Y. Nakashima, Y. Higashizono, Y. Takase, A. Ejiri, S. Kado, T. Shikama, S. Iio, T. Takeda, Y. Hirooka, T. Morisaki, Y. Nakamura, K. Toi, T. Fujimoto, A. Iwamae, T. Maekawa, M. Nagata, N. Nishino, O. Mitarai, Overview of Recent Experimental Studies on TRIAM-1M, Proc. 21th IAEA Fusion Energy Conference, (※), 2006.10.
313. K. Hanada, H. Xu, H. Idei, H. Zushi, M. Hasegawa, K. Nakamura, M. Sakamoto, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima and K. Sasaki, Power dependence of density and current drive efficiency in full LHCD plasmas on TRIAM-1M, Proc. 21th IAEA Fusion Energy Conference, (※), 2006.10.
314. Hanada, K.; Sugata, T.; Sakamoto, M.; Zushi, H.; Nakamura, K.; Sato, K. N.; Idei, H.; Hasegawa, M.; Higashijima, A.; Kawasaki, S.; Nakashima, H., Power balance investigation in steady-state LHCD discharges on TRIAM-1M, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2006.03.004, 81.0, 19.0, 2257.0-2265.0, 0.0, 2006.09, A discharge longer than 5h was successfully achieved on TRIAM-1M by fully non-inductive lower hybrid current drive (LHCD). The heat load distribution into the plasma facing components (PFCs) during the 5 h discharge was investigated using calorimetric measurements, which estimated that the injected radio frequency (RF) power coincided with the total heat load amount to the PFCs. The power balance, including the portion of direct loss power of the fast electrons and the heat flux due to the charge exchange (CX) process, was also investigated. (c) 2006 Elsevier B.V. All rights reserved..
315. Takase, Y.; Ejiri, A.; Shiraiwa, S.; Adachi, Y.; Ishii, N.; Kasahara, H.; Nuga, H.; Ono, Y.; Oosako, T.; Sasaki, M.; Shimada, Y.; Sumitomo, N.; Taguchi, I.; Tojo, H.; Tsujimura, J.; Ushigome, M.; Yamada, T.; Hanada, K.; Hasegawa, M.; Idei, H.; Nakamura, K.; Sakamoto, M.; Sasaki, K.; Sato, K. N.; Zushi, H.; Nishino, N.; Mitarai, O., Plasma current start-up experiments without the central solenoid in the TST-2 spherical tokamak, NUCLEAR FUSION, 10.1088/0029-5515/46/8/S05, 46.0, 8.0, #-#, 0.0, 2006.08, Several techniques for initiating the plasma current without the use of the central solenoid are being developed in TST-2. While TST-2 was temporarily located at Kyushu University, two types of start-up scenarios were demonstrated. (1) A plasma current of 4 kA was generated and sustained for 0.28 s by either electron cyclotron wave or electron Bernstein wave, without induction. (2) A plasma current of 10 kA was obtained transiently by induction using only outboard poloidal field coils. In the second scenario, it is important to supply sufficient power for ionization (100 kW of EC power was sufficient in this case), since the vertical field during start-up is not adequate to maintain plasma equilibrium. In addition, electron heating experiments using the X-B mode conversion scenario were performed, and a heating efficiency of 60% was observed at a 100 kW RF power level. TST-2 is now located at the Kashiwa Campus of the University of Tokyo. Significant upgrades were made in both magnetic coil power supplies and RF systems, and plasma experiments have restarted. RF power of up to 400 kW is available in the high-harmonic fast wave frequency range around 20 MHz. Four 200 MHz transmitters are now being prepared for plasma current start-up experiments using RF power in the lower-hybrid frequency range. Preparations are in progress for a new plasma merging experiment (UTST) aimed at the formation and sustainment of ultra-high beta ST plasmas..
316. K. Nakamura, F. Wang, K. N. Sato, H. Zushi, K. Hanada, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, Hot Gas Flow Simulation Aimed for Integrative Optimization of GCB, Proc. Int. Conf. on Electrical Engineering, PS1-ME-17, 2006.07.
317. Ejiri, A.; Takase, Y.; Kasahara, H.; Yamada, T.; Hanada, K.; Sato, K. N.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Iyomasa, A.; Imamura, N.; Esaki, K.; Kitaguchi, M.; Sasaki, K.; Hoshika, H.; Mitarai, O.; Nishino, N., RF start-up and sustainment experiments on the TST-2@K spherical tokamak, NUCLEAR FUSION, 10.1088/0029-5515/46/7/003, 46.0, 7.0, 709.0-713.0, 0.0, 2006.07, Plasma start-up and sustainment without an inductive field have been studied in the TST-2@K spherical tokamak using high power RF sources (8.2 GHz/up to 170 kW). Steady state discharges with a plasma current of 4 kA were achieved. The line integrated density was about 3 x 10(17) m(-2) and the electron temperature was 160 eV. A truncated equilibrium was introduced to reproduce magnetic measurements. It was found that a positive Pfirsch-Schluter current in the open field line region at the outboard boundary makes a significant contribution to the current. Insensitivity of the current to variations in the vertical field and RF power variation was also found..
318. K. Hanada, K. Sasaki, M. Hasegawa, H. Idei, H. Zushi, K. Nakamura, M. Sakamoto, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima and TRIAM group, Current profile estimation using Hard X-ray measurement along the top and bottom identical line of sight on TRIAM-1M, Proc. 33rd Conference on Control Fusion and Plasma Physics, Roma, Italy (2007), (※), 2006.06.
319. H. Zushi, R. Bhattacharyay, M. Sakamoto, Y. Nozaki, K. Nakashima, M. Ogawa, K. Takaki, K. Hanada, H. Idei, K. Nakamura, K. Sasaki, Y. Hirooka, Y. Nakashima, S. Kado , T. Shikama and TRIAM group , Dynamics of recycling processes responding to the local particle and heat load perturbations on TRIAM-1M, 33rd EPS Conference on Plasma Phys. Rome, 19 - 23 June 2006 ECA Vol.30I, P-4.124 (2006), 30I, P-4.124 , 2006.06.
320. K. Sasaki, K. Hanada, K. N. Sato, H. Zushi, K. Nakamura, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, T. Nakashima, A. Higashijima, Y. Takase, A. Ejiri, S. Shirakawa, H. Kasahara, T. Yamada and N. Nishino, Soft X-ray measurement in IRE on the TST-2 spherical tokamak, 33rd EPS Conference on Plasma Phys. Rome, 19 - 23 June 2006 ECA Vol.30I, P-4.134 (2006), (※), 2006.06.
321. Idei, H; Hanada, K; Zushi, H; Ohkubo, K; Hasegawa, M; Kubo, S; Nishi, S; Fukuyama, A; Sato, KN; Nakamura, K; Sakamoto, M; Yomasa, A; Kawasaki, S; Nakashima, H; Higashijima, A; Notake, T; Shimozuma, T; Ito, S; Hoshika, H; Maezono, N; Nakashima, K; Ogawa, M, Electron cyclotron current drive experiments in LHCD plasmas using a remote steering antenna on the TRIAM-1M tokamak, NUCLEAR FUSION, 10.1088/0029-5515/46/5/001, 46.0, 5.0, 489.0-499.0, 0.0, 2006.05, A remote steering antenna was recently developed for electron cyclotron heating and current drive (ECH/ECCD) experiments on the TRIAM- I M tokamak. This is the first application of the remote steering antenna concept for ECH/ECCD experiments, which have conditions relevant to the International Thermonuclear Experimental Reactor (ITER). Fundamental ECH and ECCD experiments were conducted in the ITER frequency from the low field using this antenna system. In addition to the angles near 0 degrees, the launcher was a symmetric direction antenna with an extended steering-angle capability of +/- (8 degrees-19 degrees). The output beam from the antenna was a well-defined Gaussian with a proper steering angle. The Gaussian content and the steering-angle accuracy were 0.85 and -0.5 degrees, respectively. The high power tests measured the antenna transmission efficiency at 0.90-0.94. The efficiencies obtained in the low and high power tests were consistent with the calculations using higher-order modes. In order to excite the pure O/X-modes in the oblique injection, two polarizers were used to control the elliptical polarization of the incident beam for the ECCD experiments. The fundamental O/X-mode ECH/ECCD was applied to lower hyrid current drive plasmas at the optimized incident polarization. In the X-mode experiment, at medium density (similar to 1 x 10(19) m(-3)), clear differences in the plasma current and the hard x-ray intensity were observed between the co- and counter-steering injections due to the ECCD effect on the coupling of forward fast electrons..
322. Shiraiwa, S; Hanada, K; Hasegawa, M; Idei, H; Kasahara, H; Mitarai, O; Nakamura, K; Nishino, N; Nozato, H; Sakamoto, M; Sasaki, K; Sato, K; Takase, Y; Yamada, T; Zushi, H, Heating by an electron Bernstein wave in a spherical tokamak plasma via mode conversion, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.96.185003, 96.0, 18.0, 0.0-0.0, Article No. 185003, 2006.05, The first successful high power heating of a high dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited by mode conversion (MC) of an X mode cyclotron wave injected from the low magnetic field side of the TST-2 spherical tokamak. Evidence of electron heating was observed as increases in the stored energy and soft x-ray emission. The increased emission was concentrated in the plasma core region. A heating efficiency of over 50% was achieved, when the density gradient in the MC region was sufficiently steep..
323. Nakamura, Kazuo; Wang, Feng; Sato, Kohnosuke; Sakamoto, Mizuki; Idei, Hiroshi; Hasegawa, Makoto; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki, Integrated gas flow simulation for overall optimization of GCB, 2006 International Conference on Power Systems Technology: POWERCON, Vols 1- 6, 0.0, 0.0, 2616.0-2618.0, 2006.04, As for hot gas flow according to fluid equation with interaction with electrical arc and solid chamber, fluid equation must be solved with moving boundary of the chamber and with interaction with hot arc and impurity intrusion. Here we propose application of CIP (Cubic Interpolated Propagation) scheme, which is convenient and good at efficient advection and boundary motion. The CIP code was tested in simulation of normal shock tube, which has an analytical solution according to Rankine-Hugoniot relation, and applied in radial shock tube. And it was tested also in simulation of shock tube with solid piston between two fluids, using density function and functional transformation..
324. Idei, H.; Shimozuma, T.; Ohkubo, K.; Kubo, S.; Notake, T.; Hanada, K.; Hasegawa, M., Operation range of remote steering antenna in anti-symmetric and symmetric directions, Conference Digest of the 2006 Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics, 0.0, 0.0, 574.0-574.0, 0.0, 2006.04, Intensity and phase profiles of the output beams from a remote steering antenna were measured in the anti-symmetric and symmetric directions. The beam properties are discussed with the imaging property calculations..
325. Nakashima, K.; Zushi, H.; Maezono, N.; Sakamoto, M.; Yoshida, N.; Tokunaga, K.; Hirooka, Y.; Shikama, T.; Kado, S.; Nishino, N.; Nakahima, Y.; Hanada, K.; Sasaki, K.; Idei, H.; Iyomasa, A.; Kawasaki, S.; Sato, K. N.; Nakashima, H.; Nakamura, K.; Hasegawa, M.; Higashijima, A., Surface temperature dependence of hydrogen balmar and molybdenum neutral lines from the Mo limiter in TRIAM-IM, 21st IEEE/NPSS Symposium on Fusion Engineering - SOFE 05, 0.0, 0.0, 578.0-581.0, P-159(2004), 2006.04, The limiter surface temperature dependence on hydrogen recycling and molybdenum impurity production behavior was studied with optical spectroscopy during long pulse plasma discharges in TRIAM-1M. It has been observed that the H-alpha intensity critically depends on the limiter surface temperature. The Mo-I intensity from the hot spot has shown a negative temperature dependence. This is believed to be due to the reduction of heat load and enhanced CX flux due to ion temperature rise..
326. Wataya, Y.; Idei, H.; Inagaki, S.; Shimozuma, T.; Nagayama, Y.; Kawahata, K.; Zushi, H., Wide-band heterodyne-radiometer with fast frequency-switching local oscillator for electron cyclotron emission diagnostics, Conference Digest of the 2006 Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics, 0.0, 0.0, 501.0-501.0, 0.0, 2006.04, 0.0.
327. Wang, F; Luo, JR; Nakamura, K; Sato, KN; Hanada, K; Sakamoto, M; Idei, H; Kawasaki, S; Nakashima, H, Continuous and real-time data acquisition system for superconducting tokamaks HT-7 and TRIAM-1M, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2005.09.055, 81.0, 8.0, 1621.0-1626.0, 2006.02, Conventional data acquisition systems cannot deal with data acquisition for a long-time discharge of a nuclear fusion reactor. Thus, continuous data acquisition with a real-time data presentation during discharge must be developed. Two data acquisition systems, which include alternating CAMAC data acquisition and long-time PCI data acquisition, are designed for the longtime operation of HT-7 tokamak. Since an effective alternating mode is adopted, the alternating CAMAC data acquisition can accurately and continuously acquire data at a rate of 10 kHz. The acquired data is immediately transmitted to a data server and real-time results can be presented during the plasma discharge. As for the long-time PCI data acquisition, a special kind of PCI A/D card, which has a hard disk on board, is designed to collect data at a max speed of 200 kHz. Thus, the total sampling duration is only related to the capacity of the hard disk on board. These two types of data acquisitions were applied to HT-7 tokamak and a 250 s discharge was acquired. These data acquisition systems were also successfully demonstrated on a 2500 s plasma discharge on TRIAM-1M. This paper describes the two data acquisitions in detail. (c) 2005 Elsevier B.V. All rights reserved..
328. Nakamura, K; Luo, JR; Wang, HZ; Ji, ZS; Wang, H; Wang, F; Qi, N; Sato, KN; Hanada, K; Sakamoto, M; Idei, H; Hasegawa, M; Iyomasa, A; Kawasaki, S; Nakashima, H; Higashijima, A, Magnetic sensorless control experiment without drift problem on HT-7, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2005.08.094, 81.0, 8.0, 1607.0-1612.0, 0.0, 2006.02, Magnetic sensorless control experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. Previously the horizontal position was calculated from the vertical field coil current and voltage without using signals of magnetic sensors like magnetic coils and flux loops placed near the plasma. The calculations are made focusing on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem of integrator of magnetic sensors. Two kinds of experiments were carried out, to keep the position constant and swing the position in a triangular waveform. (c) 2005 Elsevier B.V. All rights reserved..
329. Nakamura, K.; Luo, Jiarong; Wang, Huazhong; Ji, Zhenshan; Wang, Hua; Wang, Feng; Qi, Na; Sato, K. N.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashljima, A., Magnetic sensorless control of plasma position and shape in a tokamak, PLASMA SCIENCE & TECHNOLOGY, 10.1088/1009-0630/8/1/18, 8.0, 1.0, 80.0-83.0, 0.0, 2006.01, Magnetic sensorless sensing and control experiments with the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made to focus on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem with the integrator of magnetic sensors. Two kinds of control experiments have been carried out: to keep the position constant and swing the position in a triangular waveform. And magnetic sensorless sensing of plasma shape is discussed..
330. Kazuo Nakamura, Feng Wang, Kohnosuke Sato, Mizuki Sakamoto, Hiroshi Idei, Makoto Hasegawa, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Integrated gas flow simulation for overall optimization of GCB, 2006 International Conference on Power System Technology, POWERCON2006
2006 International Conference on Power System Technology, POWERCON2006
, 10.1109/ICPST.2006.321521, 2006.01, [URL], As for hot gas flow according to fluid equation with interaction with electrical arc and solid chamber, fluid equation must be solved with moving boundary of the chamber and with interaction with hot arc and impurity intrusion. Here we propose application of CIP (Cubic Interpolated Propagation) scheme, which is convenient and good at efficient advection and boundary motion. The CIP code was tested in simulation of normal shock tube, which has an analytical solution according to Rankine-Hugoniot relation, and applied in radial shock tube. And it was tested also in simulation of shock tube with solid piston between two fluids, using density function and functional transformation..
331. M. Sakamoto, M. Ogawa, K. Takaki, H. Zushi, K. Nakashima, N. Maezono, T. Sugata, Y. Nakashima, Y. Higashizono, Y. Kubota, A. Higashijima, H. Nakashima, S. Kawasaki, A. Iyomasa, Makoto Hasegawa, Hiroshi Idei, Kazuaki Hanada, Kazuo Nakamura, K. N. Sato, Impact of a movable limiter on the global wall recycling in TRIAM-1M, 32nd European Physical Society Conference on Plasma Physics and Controlled Fusion combined with the 8th International Workshop on Fast Ignition of Fusion Targets
32nd EPS Conference on Plasma Physics 2005, EPS 2005, Held with the 8th International Workshop on Fast Ignition of Fusion Targets - Europhysics Conference Abstracts
, 1930-1933, 2005.12, In TRIAM-1M, the influence of the local structure of the first wall on the global wall recycling has been studied using the ML with good cooling capability. No wall saturation was observed in the 5 h 16 min discharge with the ML, since particle release was suppressed by less temperature rise of the main chamber. The global wall pumping rate without the ML, ~8.6 x 10
16
atoms m
-2
s
-1
, is 3.6 times higher than that of the long duration discharge without the ML. The temperature rise in the wall is attributed to the transition of the wall role from the particle sink to the source. The co-deposition of hydrogen with Mo is a key for the wall role of the particle sink. No clear difference of the growth rate of Mo deposits on the viewing window located from the limiter surface between with and without the ML. The growth rate is from ~2 x 10
-4
nm/s to ~8 x 10
-4
nm/s. The toroidal structure of hydrogen recycling changes significantly near at the ML. However, integration of H intensity with and without the ML over the whole toroidal length is about the same within 3% , which is less than the error, i.e. 15%..
332. Shimozuma, T; Kubo, S; Idei, H; Inagaki, S; Tamura, N; Tokuzawa, T; Morisaki, T; Watanabe, KY; Ida, K; Yamada, I; Narihara, K; Muto, S; Yokoyama, M; Yoshimura, Y; Notake, T; Ohkubo, K; Seki, T; Saito, K; Kumazawa, R; Mutoh, T; Watari, T; Komori, A, Transition phenomena and thermal transport properties in LHD plasmas with an electron internal transport barrier, NUCLEAR FUSION, 10.1088/0029-5515/45/11/021, 45.0, 11.0, 1396.0-1403.0, 0.0, 2005.11, Two types of improved core confinement were observed during centrally focused electron cyclotron heating (ECH) into plasmas sustained by counter (CNTR) and Co neutral beam injections (NBI) in the Large Helical Device. The CNTR NBI plasma displayed transition phenomena to the high-electron-temperature state and had a clear electron internal transport barrier, while the Co NBI plasma did not show a clear transition or an ECH power threshold but showed broad high temperature profiles with moderate temperature gradient. This indicated that the Co NBI plasma with additional ECH also had an improved core confinement. The electron heat transport characteristics of these plasmas were directly investigated using heat pulse propagation excited by modulated ECH. These effects appear to be related to the m/n = 2/1 rational surface or the island induced by NBI beam-driven current..
333. Zushi, H; Nakamura, K; Hanada, K; Sato, KN; Sakamoto, M; Idei, H; Hasegawa, M; Iyomasa, A; Kawasaki, S; Nakashima, H; Higashijima, A; Kuramoto, T; Tanaka, A; Matsuo, Y; Esaki, K; Akanishi, H; Sugata, T; Hoshika, H; Sasaki, K; Maezono, N; Kitaguchi, M; Imamura, N; Yoshida, N; Tokunaga, K; Fujiwara, T; Miyamoto, M; Tokitani, M; Uehara, K; Sadamoto, Y; Nakashima, Y; Kubota, Y; Higasizono, Y; Takase, Y; Ejiri, A; Shiraiwa, S; Kado, S; Sikama, T; Tsuji-Iio, S; Takeda, T; Hirooka, Y; Ida, K; Nakamura, Y; Fujimoto, T; Iwamae, A; Maekawa, T; Mitarai, O, Steady-state tokamak operation, ITB transition and sustainment and ECCD experiments in TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/45/10/S12, 45.0, 10.0, #-#, 0.0, 2005.10, Experiments aiming at 'day long operation at high performance' have been carried out in TRIAM-1M. The record value of the discharge duration was updated to 5 h and 16 min. Steady-state tokamak operation is studied under the localized plasma wall interaction conditions. The distributions of the heat load, the particle recycling flux and impurity source are investigated to understand the co-deposition and wall pumping. The formation and sustainment of an internal transport barrier (ITB) in enhanced current drive mode has been investigated by controlling the lower hybrid driven current profile by changing the phase spectrum. An ITER relevant remote steering antenna for electron cyclotron wave injection was installed and a relativistic Doppler resonance of the oblique propagating extraordinary wave with energetic electrons driven by lower hybrid waves was studied..
334. M. Sakamoto, K. N. Sato, M. Ogawa, K. Takaki, H. Zushi, K. Nakashima, N. Maezono, T. Sugata, Y. Nakashima, Y. Higashizono, Y. Kubota, A. Higashijima, H. Nakashima, S. Kawasaki, A. Iyomasa, M. Hasegawa, H. Idei, K. Hanada, K. Nakamura, Recent Global Wall Recycling Studies in Long Term Sustained TRIAM-1M Tokamak and its Development in New ST Device in Kyushu University, The 5th conference of Asia Plasma & Fusion Association (APFA 2005), August 29-31, 2005, Jeju (Korea), Proc. of the 5th conference of Asia Plasma & Fusion Association (APFA 2005),, 2005.08.
335. K. Nakamura, J. R. Luo, H. Z. Wang, Z. S. Ji, H. Wang, F. Wang, N. Qi, K. N. Sato, K. Hanada, M. Sakamoto, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, Magnetic Sensorless Control of Plasma Position without Drift Problem in the HT-7 Tokamak, Proc. Int. Conf. on Electrical Engineering,2005,Kunming,China, (※), 2005.07.
336. Kubo, S; Shimozuma, T; Yoshimura, Y; Notake, T; Idei, H; Inagaki, S; Yokoyama, M; Ohkubo, K; Kumazawa, R; Nakamura, Y; Saito, K; Seki, T; Mutoh, T; Watari, T; Narihara, K; Yamada, I; Ida, K; Takeiri, Y; Funaba, H; Ohyabu, N; Kawahata, K; Kaneko, O; Yamada, H; Itoh, K; Ashikawa, N; Emoto, M; Goto, M; Hamada, Y; Ido, T; Ikeda, K; Isobe, M; Khlopenkov, K; Kobuchi, T; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Murakami, S; Muto, S; Nagaoka, K; Nagayama, Y; Nakanishi, H; Narushima, Y; Nishimura, K; Nishiura, M; Noda, N; Ohdachi, S; Oka, Y; Osakabe, M; Ozaki, T; Peterson, BJ; Sagara, A; Sakakibara, S; Sakamoto, R; Shoji, M; Sudo, S; Takeuchi, N; Tamura, N; Tanaka, K; Toi, K; Tokuzawa, T; Tsumori, K; Watanabe, K; Watanabe, T; Yamazaki, K; Yoshinuma, M; Komori, A; Motojima, O, Extension and characteristics of an ECRH plasma in LHD, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/47/5A/008, 47.0, 5A, A81, 2005.05, One of the main objectives of LHD is to extend the plasma confinement database for helical systems and to demonstrate such extended plasma confinement properties to be sustained in the steady state. Among the various plasma parameter regimes, the study of confinement properties in the collisionless regime is of particular importance. Electron cyclotron resonance heating (ECRH) has been extensively used for these confinement studies of LHD plasma from the initial operation. The system optimizations including the modification of the transmission and antenna system are performed with special emphasis on the local heating properties. As a result, a central electron temperature of more than 10 keV with an electron density of 0.6 x 10(19) m(-3) is achieved near the magnetic axis. The electron temperature profile is characterized by a steep gradient similar to those of an internal transport barrier observed in tokamaks and stellarators. The 168 GHz ECRH system demonstrated efficient heating at densities more than 1.0 x 10(20) m(-3). The continuous wave ECRH system is successfully operated to sustain a 756 s discharge..
337. Notake, T; Idei, H; Shimozuma, T; Sato, M; Kubo, S; Ito, S; Takita, Y; Ohkubo, K; Yoshimura, Y; Kobayashi, S; Mizuno, Y; Watari, T; Kumazawa, R; Shapiro, MA; Temkin, RJ, Evaluation of phase correcting mirrors for an 84 GHz gyrotron based on direct phase measurements at low-power level, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2004.12.002, 73.0, 1.0, 9.0-18.0, 0.0, 2005.04, Low-power tests are carried out to evaluate the performance of the newly designed MOU by reversely injecting a Gaussian beam from the output port of the MOU. The output beam from the input port of the MOU is measured with the analyzer. In this inverse process, the: injected Gaussian beam should be converted to the real beam pattern radiated from the gyrotron. Using correlation analysis, the measured- and calculated-electric fields are compared in their amplitude- and phase-profiles. Good agreement between the measurement and the calculation is obtained. Therefore, it is judged that the phase-correcting mirrors in the MOU will work correctly in upcoming high-power tests. © 2005 Elsevier B.V. All rights reserved.A low-power test system using a vector network analyzer is constructed to evaluate the performance of phase correcting mirrors in a matching optics unit (MOU). The MOU is used in order to facilitate the good coupling of a millimeter wave beam from a gyrotron into corrugated waveguides. The newly developed diagnostic system allows us to make measurements not only of intensity-, but also of phase-profiles of millimeter wave beams and opens a new range of possibilities for designing and testing high-precision quasi-optical systems..
338. Takashi Shimozuma, Hiroshi Idei, Michael Shapiro, Richard Temkin, Satoshi Ito, Takashi Notake, Shin Kubo, Yasuo Yoshimura, Sakuji Kobayashi, Yoshinori Mizuno, Yasuyuki Takita, Kunizo Ohkubo, Alignment Method of ECH Transmission Lines Based on the Moment and Phase Retrieval Method Using IR Images, Journal of Plasma and Fusion Research, 81.0, 3.0, 191.0-196.0, 2005.03.
339. Notake, T; Kubo, S; Shimozuma, T; Idei, H; Yoshimura, Y; Inagaki, S; Ohkubo, K; Kobayashi, S; Mizuno, Y; Ito, S; Takita, Y; Watari, T; Narihara, K; Morisaki, T; Yamada, I; Nagayama, Y; Tanaka, K; Sakakibara, S; Kumazawa, R; Seki, T; Saito, K; Mutoh, T; Shimizu, A; Komori, A, Optimization of incident wave polarization for ECRH in LHD, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/47/3/009, 47.0, 3.0, 531.0-544.0, 0.0, 2005.03, This paper reports on the results of an experimental investigation into electron cyclotron resonance heating (ECRH) using the fundamental O-mode in the large helical device (LHD). The aim of the experiment is to understand the mechanism of the selective excitation of the O-mode EC wave and, thereby, optimize the performance of the ECRH. The polarization angle and the ellipticity of the electric field of the incident high power millimetre waves were varied in the experiment using a pair of grating polarizers. The responses of the plasma stored energy and electron temperature were measured to evaluate the effects. The optimum values of the polarization angle and the ellipticity for the ECRH were identified experimentally. A simple model of power branching between the O- and X-modes is introduced in order to interpret the observed experimental results. Specific to the ECRH in the LHD configuration, the effect of magnetic shear in the plasma peripheral region is considered..
340. Notake, T; Idei, H; Kubo, S; Shimozuma, T; Yoshimura, Y; Kobayashi, S; Mizuno, Y; Ito, S; Takita, Y; Ohkubo, K; Kasparek, W; Watari, T; Kumazawa, R, Real time polarization monitor developed for high power electron cyclotron resonance heating and current drive experiments in large helical device, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.1848657, 76.0, 2.0, 1.0, Article No. 023504, 2005.02, The polarization state of a wave is an important factor in electron cyclotron resonance heating (ECRH) and current drive (ECCD), for it strongly affects the propagation and absorption of the wave in the plasma. A real-time monitor of the polarization of the EC beam has been developed for use in ECRH/ECCD experiments in large helical device (LHD). Two orthogonal components of the wave field are measured in one of the miter-bends by use of a specially designed coupler and a waveguide circuit with a 0degrees-90degrees phase switch to deduce the polarization parameters: the polarization angle alpha and the ellipticity beta. Since fast-response pin diodes are used for the switches, the polarization is determined every 3 ms, facilitating real time acquisition of the polarization. This article reports on the design and the principle of this monitor as well as on the algorithm used to calculate alpha and beta. This article also reports on the method of calibration, for the accuracy of this measurement depends on it. Finally, a comparison is made between polarization parameters measured by a monitor actually installed on one of the ECRH transmission lines on LHD and the value set by the polarizer in ECRH experiments. (C) 2005 American Institute of Physics..
341. SHIRAIWA, Syun’ichi; Ejiri, Akira; Hanada, Kazuaki; Hasegawa, Makoto; Hoshika, Hiroyuki; Idei, Hiroshi; Iyomasa, Atsuhiro; Kamada, Yusuke; Kasahara, Hiroshi; Mitarai, Osamu; , Evidence of electron Bernstein wave heating on the TST-2 spherical tokamak, JOURNAL OF NUCLEAR MATERIALS, 81.0, 1.0, P3-P4, 2005.01.
342. M. Sakamoto, M. Ogawa, K. Takaki, H. Zushi, K, Nakashima, N. Maezono, T. Sugata, Y. Nakashima, Y. Higashizono, Y. Kubota, A. Higashijima, H. Nakashima, S. Kawasaki, A. Iyomasa, M. Hasegawa, H. Idei, K. Hanada, K. Nakamura, K. N. Sato, Impact of a movable limiter on the global wall recycling in TRIAM-1M, Proc. of 32nd EPS Conference on Plasma Physics, 2005.01.
343. Idei, Hiroshi; Shimozuma, Takashi; Shapiro, Michael; Temkin, Richard; Notake, Takashi; Ito, Satoshi; Kubo, Shin; Ohkubo, Kunizo; , Quasi-optical beam analysis based on direct phase measurement at low power level, Journal of Plasma and Fusion Research, 81.0, 3.0, 186.0-190.0, 2005.01.
344. Hanada, K; Iyomasa, A; Zushi, H; Hasegawa, M; Sasaki, K; Hoshika, H; Nakamura, K; Sakamoto, M; Sato, KN; Idei, H; , Transport barrier formation and its maintenance by LHCD on TRIAM-1M, Proc. of 20. IAEA fusion energy conference, IAEA-CN-116-EX/P4-25, 2005.01.
345. Hiroshi Idei, Kazuaki Hanada, K. Ohkubo, Makoto Hasegawa, T. Notake, S. Kubo, T. Shimozuma, S. Ito, K. N. Sato, H. Zushi, Kazuo Nakamura, M. Sakamoto, A. Iyomasa, S. Kawasaki, H. Nakashima, A. Higashijima, S. Nishi, Remote steering antenna system on the TRIAM-1M Tokamak, Conference Digest of the 2004 Joint 29th International Conference on Infrared and Millimeter Waves and 12th International Conference on Terahertz Electronics
Conference Digest of the 2004 Joint 29th International Conference on Infrared and Millimeter Waves and 12th International Conference on Terahertz Electronics
, 10.1109/ICIMW.2004.1422297, 725-726, 2004.12, A remote steering antenna designed as a symmetric direction antenna is prepared for Electron Cyclotron Heating (ECH) and Current Drive (ECCD) experiments on the TRIAM-1M tokamak. The steering angles of 8-19 degrees are available in the design, in addition to the angle near 0 degrees. The antenna is tested at both of high and low power levels. The fraction of radiated power to injected power at the antenna is roughly evaluated at the low power test. The angle radiated from the antenna is checked from both of the intensity and phase measurements at the low power test. Several percentage losses at the antenna are evaluated at the high power test. The antenna system is evaluated to work correctly..
346. H. Idei, K. Hanada, H. Zushi, K. Ohkubo, M. Hasegawa, S. Kubo, S. Nishi, K. N. Sato, K. Nakamura, M. Sakamoto, A. Iyomasa, S. Kawasaki, H. Nakashima, A. Higashijima, T. Notake, T. Shimozuma, S. Ito, H. Hoshika, N. Maezono, K. Nakashima, M. Ogawa, TRIAM Gro, Fundamental X-mode Electron Cyclotron Current Drive using Remote-Steering Symmetric Direction Antenna at Larger Steering Angles, 20th IAEA Fusion Energy Conference,IAEA-CN-116-PD-1-2(2004), IAEA-CN-116-PD-1-2, 2004.11.
347. H. ZUSHI, K. NAKAMURA, K. HANADA, K. N. SATO, M. SAKAMOTO, H. IDEI, M. HASEGAWA, A. IYOMASA, S. KAWASAKI, H. NAKASHIMA, A. HIGASHIJIMA, T. KURAMOTO, A. TANAKA, Y. MATSUO, K. ESAKI, H. AKANISHI, H. AYATSUKA, S. IMADA, T. SUGATA, H. HOSHIKA, K. SASAKI, N. MAEZONO, M. KITAGUCHI, N. IMAMURA, T. HAYASAKI, K. ICHIZONO, S. KUGIMIYA, N. YOSHIDA, K. TOKUNAGA, T. FUJIWARA, M. MIYAMOTO, M. OKITANI, K. UEHARA, Y. SADAMOTO, Y. NAKASHIMA, Y. KUBOTA, Y. HIGASIZONO, Y. TAKASE, A. EJIRI, S. SHIRAIWA, S. KADO, T. SIKAMA, S. TSUJI-IIO , T. TAKEDA, Y. HIROOKA, K. IDA, Y. NAKAMURA, T. FUJIMOTO, A. IWAMAE, T. MAEKAWA, O. MITARAI, Overview of steady-state tokamak operation and current drive experiments in TRIAM-1M , 20th IAEA Fusion Energy Conference, IAEA-CN-116-OV5-2(2004), 2004.11.
348. M Sakamoto, Y Matsuo, T Kuramoto, M Kitaguchi, T Sugata, N Maezono, M Tokitani, H Zushi, K Nakamura, K Hanada, KN Sato, H Idei, M Hasegawa, A Iyomasa, S Kawasaki, H Nakashima, A Higashijima, N Yoshida, K Tokunaga, T Fujiwara, M Miyamoto, Y Nakashima, Y Kubota, Y Higashizono, Y Hirooka, S Kado, T Shikama, Toroidal Structure of Hydrogen Recycling in Ultra-long Discharges on TRIAM-1M, 20th IAEA Fusion Energy Conference 2004. Conference proceedings, IAEA-OV-EX/P5-30, 2004.11.
349. Sugata, Tomoya; Hanada, K; Imamura, N; Sakamoto, M; Zushi, H; Idei, H; Iyomasa, A; Kawasaki, S; Sato, K; Nakashima, H; , Estimation of Power Balance in Steady State LHCD Discharges on TRIAM-1M, Proc. of 12th International Congress on Plasma Physics, P3-094, 2004.10.
350. Hiroyuki Hoshika, H. Zushi, M. Aramasu, H. Idei, A. Iyomasa, A. Ejiri, S. Ohara, H. Kasahara, Y. Kamada, S. Kawasaki, M. Sakamoto, K. Sasaki, K. Sato, S. Shiraiwa, Y. Takagi, Y. Takase, H. Nakashima, K. Nakamura, M. Hasegawa, K. Hanada, A. Higashijima, T. Yamada, Ion acceleration during internal magnetic reconnection events in TST-2, 12th International Congress on Plasma Physics,25-29 October 2004,Nice (France), arXiv preprint physics/0410229, P1-078, 2004.10, Characteristics of ion acceleration in the internal magnetic reconnection events (IRE) have been studied by means of a neutral particle energy analyzer (NPA) in Tokyo Spherical Tokamak (TST-2). The major and minor radii are 0.38 m and 0.25m, respectively. The magnetic field strength is 0.3T and the maximum plasma current is up to 140 kA. The electron and ion temperatures are 0.4-0.5 keV and 0.1 keV, respectively and the electron density is ~1x1019 m-3. The NPA can be scanned toroidally from q = 74° (cw) to q = 114° (ccw), where q = 90° corresponds to the perpendicular sightline. The direction of the plasma current is cw. The NPA signals are digitized at every 50 ms. The NPA is calibrated in the energy range of 0.1 keV < E < 8.4 keV. When the IRE occurs, it is observed that the plasma current increases by ~ 20% and the loop voltage drops from 0.6 V to-5 V for ~ 0.1 ms. The enhanced charge exchange flux is observed by more than one order of magnitude at ~ 1 keV for this reconnection phase. The ion temperature increases by 80 eV at IREs. The angle q dependence of increment of Ti shows that DTi (q = 74°) is higher than that for q = 114°. This observation suggests that an ion is accelerated initially in the direction of magnetic field lines. The time evolution of the ion distribution function is simulated with a Fokker-Planck code taking into account the electric field effects..
351. K. Hanada, A. Iyomasa, H. Zushi, M. Hasegawa, K. Sasaki, H. Hoshika, K. Nakamura, M. Sakamoto, K. N. Sato, H. Idei, S. Kawasaki, H. Nakashima, A. Higashijima, Transport barrier formation by LHCD on TRIAM-1M, 12th International Congress on Plasma Physics,25-29 October 2004,Nice (France), (※), 2004.10, Internal transport barrier (ITB) has been obtained in full lower hybrid current driven (LHCD) plasmas on a superconducting tokamak, TRIMA-1M (R=0.84m, a x b=0.12mx0.18m, BT<8T). The formation of ITB depends on the current density profile, j(r), varied by the power deposition of the lower hybrid (LH). The plasma with ITB can be maintained by the LH power deposited around the foot point of ITB up to 25 sec, which corresponds to more than 100 times of current diffusion time, τL/R. ITB is terminated by the reduction of current drive efficiency caused by metal impurities accumulation. In some condition, self-organized slow sawtooth oscillations (SSSO) of plasma current, density, temperature, and so on with the period comparable to the current diffusion time have been also observed during ITB discharge. The oscillation has the capability of particle exhaust, as the result, it may play an role in the avoidance of the impurity accumulation and the dilution in the future steady state fusion plasma with ITB, as the edge-localized mode in H-mode..
352. H Zushi, M Sakamoto, K Hanada, Y Matsuo, K Kuramoto, T Sugata, N Maezono, H Hoshika, A Iyomasa, K Sasaki, K Nakamura, KN Sato, H Idei, S Kawasaki, H Nakashima, A Higashijima, M Hasegawa, Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M, Proc. of 12. International Congress on Plasma Physics, (※), 2004.08.
353. MITARAI Osamu, TAKASE Yuichi, EJIRI Akira, SHIRAIWA Shun’ichi, KASAHARA Hiroshi, YAMADA Takuma, OHARA Shinya, TST-2 Team, NAKAMURA Kazuo, IYOMASA Atsuhiro, HASEGAWA Makoto, IDEI Hiroshi, SAKAMOTO Mizuki, HANADA Kazuaki, SATOH Kohnosuke, ZUSHI Hideki, TRIAM Group and NISHINO Nobuhiro, Plasma current start-up by ECW and vertical field in the TST-2 spherical tokamak, Journal of Plasma and Fusion Research SERIES, Vol. 80, No. , Pages 549, 2004.07.
354. Motojima, O; Yamada, H; Komori, A; Watanabe, KY; Mutoh, T; Takeiri, Y; Ida, K; Akiyama, T; Asakura, N; Ashikawa, N; Chikaraishi, H; Cooper, WA; Emoto, M; Fujita, T; Fujiwara, M; Funaba, H; Goncharov, P; Goto, M; Hamada, Y; Higashijima, S; Hino, T; Hoshino, M; Ichimura, M; Idei, H; Ido, T; Ikeda, K; Imagawa, S; Inagaki, S; Isayama, A; Isobe, M; Itoh, T; Itoh, K; Kado, S; Kalinina, D; Kaneba, T; Kaneko, O; Kato, D; Kato, T; Kawahata, K; Kawashima, H; Kawazome, H; Kobuchi, T; Kondo, K; Kubo, S; Kumazawa, R; Lyon, JF; Maekawa, R; Mase, A; Masuzaki, S; Mito, T; Matsuoka, K; Miura, Y; Miyazawa, J; More, R; Morisaki, T; Morita, S; Murakami, I; Murakami, S; Mutoh, S; Nagaoka, K; Nagasaki, K; Nagayama, Y; Nakamura, Y; Nakanishi, H; Narihara, K; Narushima, Y; Nishimura, H; Nishimura, K; Nishiura, M; Nishizawa, A; Noda, N; Notake, T; Nozato, H; Ohdachi, S; Ohkubo, K; Ohyabu, N; Oyama, N; Oka, Y; Okada, H; Osakabe, M; Ozaki, T; Peterson, BJ; Sagara, A; Saida, T; Saito, K; Sakakibara, S; Sakamoto, M; Sakamoto, R; Ttt, MS; Sato, K; Seki, T; Shimozuma, T; Shoji, M; Sudo, S; Takagi, S; Takahashi, Y; Takase, Y; Takenaga, H; Takeuchi, N; Tamura, N; Tanaka, K; Tanaka, M; Toi, K; Takahata, K; Tokuzawa, T; Torii, Y; Tsumori, K; Watanabe, F; Watanabe, M; Watanabe, T; Watari, T; Yamada, I; Yamada, S; Yamaguchi, T; Yamamoto, S; Yamazaki, K; Yanagi, N; Yokoyama, M; Yoshida, N; Yoshimura, S; Yoshimura, Y; Yoshinuma, M, Review on the progress of the LHD experiment, FUSION SCIENCE AND TECHNOLOGY, 46.0, 1.0, 1.0-12.0, 0.0, 2004.07, Recent progress in the Large Helical Device (LHD) experiment during the last 2 yr is reviewed. The LHD has been extending its operational regime toward fusion-relevant conditions while taking advantage of the net-current-free heliotron concept employing a superconducting coil system. Heating capability has exceeded 10 MW, and the central ion and electron temperatures have reached 7 and 10 keV respectively. The maximum values of beta and pulse length have been extended to 3.2% and 150 s, respectively. Several encouraging physics observations have been obtained, i.e., simultaneous achievement of the mitigation of the magnetohydro-dynamic instability criteria and good confinement, and formation of an internal transport barrier. The initial results have been obtained using a local island divertor, which shows the possibility of particle control at the plasma edge..
355. S. Kubo, T. Shimozuma, Y. Yoshimura, S. Inagaki, T. Notake, H. Idei, K. Ohkubo, R. Kumazawa, Y. Nakamura, K. Saito, T. Seki, T. Mutoh, Y. Takita, S. Kobayashi, S. Ito, Y. Mizuno, F. Gandini, I. Kazanski, A. Kruglov, V. Kurbatov, E. Tai and LHD Experimental group, RECENT UPGRADE OF ECRH SYSTEM AND RESULTS OF THE HIGH POWER LONG PULSE INJECTION IN THE LHD, 13th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, 2004.05.
356. Ida, K; Inagaki, S; Shimozuma, T; Tamura, N; Funaba, H; Narihara, K; Kubo, S; Murakami, S; Wakasa, A; Yokoyama, M; Takeiri, Y; Watanabe, KY; Tanaka, K; Yoshinuma, M; Liang, Y; Ohyabu, N; Akiyama, T; Ashikawa, N; Emoto, M; Fujita, T; Fukuda, T; Goncharov, P; Goto, M; Idei, H; Ikeda, K; Isayama, A; Isobe, M; Kaneko, O; Kawahata, K; Kawazome, H; Kobuchi, T; Komori, A; Kumazawa, R; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Muto, S; Mutoh, T; Nagayama, Y; Nakamura, Y; Nakanishi, H; Narushima, Y; Nishimura, K; Noda, N; Notake, T; Nozato, H; Ohdachi, S; Oka, Y; Okajima, S; Osakabe, M; Ozaki, T; Peterson, BJ; Sagara, A; Saida, T; Saito, K; Sakakibara, S; Sakamoto, R; Sakamoto, Y; Sasao, M; Sato, K; Sato, M; Seki, T; Shoji, M; Suzuki, H; Takeuchi, N; Toi, K; Tokuzawa, T; Torii, Y; Tsumori, K; Watari, T; Yamada, H; Yamada, I; Yamamoto, S; Yamamoto, T; Yoshimura, Y; Itoh, K; Matsuoka, K; Ohkubo, K; Sudo, S; Uda, T; Yamazaki, K; Motojima, O, Characteristics of transport in electron internal transport barriers and in the vicinity of rational surfaces in the Large Helical Device, PHYSICS OF PLASMAS, 10.1063/1.1668787, 11.0, 5.0, 2551.0-2557.0, 0.0, 2004.05, Characteristics of transport in electron internal transport barriers (ITB) and in the vicinity of a rational surface with a magnetic island are studied with transient transport analysis as well as with steady state transport analysis. Associated with the transition of the radial electric field from a small negative value (ion-root) to a large positive value (electron-root), an electron ITB appears in the Large Helical Device [M. Fujiwara , Nucl. Fusion 41, 1355 (2001)], when the heating power of the electron cyclotron heating exceeds a power threshold. Transport analysis shows that both the standard electron thermal diffusivity, chi(e), and the incremental electron thermal diffusivity, chi(e)(inc) (the derivative of normalized heat flux to temperature gradient, equivalent to heat pulse chi(e)), are reduced significantly (a factor 5-10) in the ITB. The chi(e)(inc) is much lower than the chi(e) by a factor of 3 just after the transition, while chi(e)(inc) is comparable to or even higher than chi(e) before the transition, which results in the improvement of electron transport with increasing power in the ITB, in contrast to its degradation outside the ITB. In other experiments without an ITB, a significant reduction (by one order of magnitude) of chi(e)(inc) is observed at the O-point of the magnetic island produced near the plasma edge using error field coils. This observation gives significant insight into the mechanism of transport improvement near the rational surface and implies that the magnetic island serves as a poloidally asymmetric transport barrier. Therefore the radial heat flux near the rational surface is focused at the X-point region, and that may be the mechanism to induce an ITB near a rational surface. (C) 2004 American Institute of Physics..
357. Ida, K; Fujita, T; Fukuda, T; Sakamoto, Y; Ide, S; Toi, K; Inagaki, S; Shimozuma, T; Kubo, S; Idei, H; Fujisawa, A; Ohdachi, S; Yoshinuma, M; Funaba, H; Narihara, K; Murakami, S; Wakasa, A; Yokoyama, M; Takeiri, Y; Watanabe, KY; Tanaka, K; Liang, Y; Ohyabu, N, Comparison of electron internal transport barriers in the large helical device and JT-60U plasmas, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/46/5A/004, 46.0, 5A, A45-A50, PII S0741-3335(04)70388-7, 2004.05, Plasmas with an electron internal transport barrier (ITB), which is characterized by peaked electron temperature profiles, are obtained in the JT-60U tokamak and in the large helical device (LHD) when the electron cyclotron heating (ECH) is focused on the magnetic axis. The maximum values of R/L-Te, where R is the major radius and LT. is the scale length of the electron temperature gradient, are similar for the LHD and JT-60U ITB plasmas. However, there is a clear jump of R/L-Te observed in LHD but not in JT-60U in the ECH power scan. This result is consistent with the fact that the trigger mechanism of the electron ITB is the fast transition of the radial electric field from a small negative E, to a large positive E, in LHD and a change of the magnetic shear from positive to negative is required for the formation of the electron ITB in JT-60U. There are also differences in the electron temperature profiles inside the ITB. The flattening of the electron temperature profile inside the strong ITB could be explained by the sharp increase of q values observed in JT-60U, while no flattening of the electron temperature profile is observed in LHD, where the central q values stay low..
358. Fujita, T; Fukuda, T; Sakamoto, Y; Ide, S; Suzuki, T; Takenaga, H; Ida, K; Idei, H; Shimozuma, T; Fujisawa, A; Ohdachi, S; Toi, K, Formation conditions for electron internal transport barriers in JT-60U plasmas, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/46/5A/003, 46.0, 10A, A35-A43, PII S0741-3335(04)70644-2, 2004.05, The formation of electron internal transport barriers (ITBs) was studied using electron cyclotron (EC) heating in JT-60U positive shear (PS) and reversed shear (RS) plasmas with scan of neutral beam (NB) power. With no or low values of NB power and with a small radial electric field (Er) gradient, a strong, box-type electron ITB was formed in RS plasmas while a peaked profile with no strong electron ITBs was observed in PS plasmas within the available EC power. When the NB power and the Er gradient were increased, the electron transport in strong electron ITBs with EC heating in RS plasmas was not affected, while electron thermal diffusivity was reduced in conjunction with the reduction of ion thermal diffusivity, and strong electron and ion ITBs were formed in PS plasmas..
359. K. Ida, S. Inagaki, T. Shimozuma, N. Tamura, H. Funaba, K. Narihara, S. Kubo, S. Murakami, A. Wakasa, M. Yokoyama, Y. Takeiri, K. Y. Watanabe, K. Tanaka, M. Yoshinuma, Y. Liang, N. Ohyabu, T. Akiyama, N. Ashikawa, M. Emoto, T. Fujita, T. Fukuda, P. Goncharov, M. Goto, H. Idei, K. Ikeda, A. Isayama, M. Isobe, O. Kaneko, K. Kawahata, H. Kawazome, T. Kobuchi, A. Komori, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, Y. Narushima, K. Nishimura, N. Noda, T. Notake, H. Nozato, S. Ohdachi, Y. Oka, S. Okajima, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, Y. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, M. Shoji, H. Suzuki, N. Takeuchi, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Watari, H. Yamada, I. Yamada, S. Yamamoto, T. Yamamoto, Y. Yoshimura, K. Itoh, K. Matsuoka, K. Ohkubo, S. Sudo, T. Uda, K. Yamazaki, O. Motojima, Characteristics of transport in electron internal transport barriers and in the vicinity of rational surfaces in the Large Helical Device, Physics of Plasmas, 10.1063/1.1688787, 11, 5 PART 2, 2551-2557, 2004.05, [URL], The characteristics of transport in electron internal transport barriers (ITB) and in the vicinity of a rational surface with a magnetic island were analyzed using trasient transport analysis and steady state transport analysis. An electron ITB appeared in the large helical device (LHD), when the heating power of the electron cyclotron heating exceeded a power threshold. It was shown by the transport analysis that both the standard electron thermal diffusivity and the incremental electron thermal diffusivity are reduced significantly in the ITB. The results show that the radial heat flux near the rational surface is focused at the X-point region, and that may be the mechanism to induce an ITB near a rational surface..
360. Idei, H; Hanada, K; Ohkubo, K; Hasegawa, M; Notake, T; Kubo, S; Shimozuma, T; Ito, S; Sato, KN; Zushi, H; Nakamura, K; Sakamoto, M; Iyomasa, A; Kawasaki, S; Nakashima, H; Higashijima, A; Nishi, S, Remote steering antenna system on the TRIAM-1M tokamak, CONFERENCE DIGEST OF THE 2004 JOINT 29TH INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 12TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, 0.0, 0.0, 725.0-726.0, 0.0, 2004.04, A remote steering antenna designed as a symmetric direction antenna is prepared for Electron Cyclotron Heating (ECH) and Current Drive (ECCD) experiments on the TRIAM-IM tokamak. The steering angles of 8-19 degrees are available in the design, in addition to the angle near 0 degrees. The antenna is tested at both of high and low power levels. The fraction of radiated power to injected power at the antenna is roughly evaluated at the low power test. The angle radiated from the antenna is checked from both of the intensity and phase measurements at the low power test. Several percentage losses at the antenna are evaluated at the high power test. The antenna system is evaluated to work correctly..
361. K Toi, S Ohdachi, S Yamamoto, N Nakajima, S Sakakibara, KY Watanabe, S Inagaki, Y Nagayama, Y Narushima, H Yamada, K Narihara, S Morita, T Akiyama, N Ashikawa, X Ding, M Emoto, H Funaba, M Goto, K Ida, H Idei, T Ido, K Ikeda, S Imagawa, M Isobe, K Itoh, O Kaneko, K Kawahata, T Kobuchi, A Komori, S Kubo, R Kumazawa, J Li, Y Liang, S Masuzaki, T Mito, J Miyazawa, T Morisaki, S Murakami, S Muto, T Mutoh, K Nagaoka, Y Nakamura, H Nakanishi, K Nishimura, A Nishizawa, N Noda, T Notake, K Ohkubo, I Ohtake, N Ohyabu, Y Oka, S Okamura, T Ozaki, BJ Peterson, A Sagara, T Saida, K Saito, R Sakamoto, M Sasao, K Sato, M Sato, T Satow, T Seki, T Shimozuma, M Shoji, S Sudo, MY Tanaka, N Tamura, K Tanaka, K Tsumori, T Uda, T Watari, A Weller, Y Xu, I Yamada, M Yokoyama, S Yoshimura, Y Yoshimura, K Yamazaki, K Matsuoka, O Motojima, Y Hamada, M Fujiwara, MHD instabilities and their effects on plasma confinement in Large Helical Device plasmas, NUCLEAR FUSION, Vol. 44, No. 2, Pages 217, 2004.02.
362. Katsumi Ida, S Inagaki, N Tamura, T Morisaki, N Ohyabu, K Khlopenkov, S Sudo, K Watanabe, M Yokoyama, T Shimozuma, Y Takeiri, K Itoh, M Yoshinuma, Y Liang, K Narihara, K Tanaka, Y Nagayama, T Tokuzawa, K Kawahata, H Suzuki, A Komori, T Akiyama, N Ashikawa, M Emoto, H Funaba, P Goncharov, M Goto, H Idei, K Ikeda, M Isobe, O Kaneko, H Kawazome, T Kobuchi, A Kostrioukov, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, S Morita, S Murakami, S Muto, T Mutoh, Y Nakamura, H Nakanishi, Y Narushima, K Nishimura, N Noda, T Notake, H Nozato, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, T Saida, K Saito, S Sakakibara, R Sakamoto, M Sasao, K Sato, M Sato, T Seki, M Shoji, N Takeuchi, K Toi, Y Torii, K Tsumori, T Watari, Y Xu, H Yamada, I Yamada, S Yamamoto, T Yamamoto, Y Yoshimura, I Ohtake, K Ohkubo, T Mito, T Satow, T Uda, K Yamazaki, K Matsuoka, O Motojima, M Fujiwara, Radial electric field and transport near the rational surface and the magnetic island in LHD, NUCLEAR FUSION, Vol. 44, No. 2, Pages 290, 2004.02.
363. K. Toi, S. Ohdachi, S. Yamamoto, N. Nakajima, S. Sakakibara, K. Y. Watanabe, Inagaki Shigeru, Y. Nagayama, Y. Narushima, H. Yamada, K. Narihara, S. Morita, T. Akiyama, N. Ashikawa, X. Ding, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, T. Ido, K. Ikeda, S. Imagawa, M. Isobe, K. Itoh, O. Kaneko, K. Kawahata, T. Kobuchi, A. Komori, S. Kubo, R. Kumazawa, J. Li, Y. Liang, S. Masuzaki, T. Mito, J. Miyazawa, T. Morisaki, S. Murakami, S. Muto, T. Mutoh, K. Nagaoka, Y. Nakamura, H. Nakanishi, K. Nishimura, A. Nishizawa, N. Noda, T. Notake, K. Ohkubo, I. Ohtake, N. Ohyabu, Y. Oka, S. Okamura, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Satow, T. Seki, T. Shimozuma, M. Shoji, S. Sudo, M. Y. Tanaka, N. Tamura, K. Tanaka, K. Tsumori, T. Uda, T. Watari, A. Weller, Y. Xu, I. Yamada, M. Yokoyama, S. Yoshimura, Y. Yoshimura, K. Yamazaki, K. Matsuoka, O. Motojima, Y. Hamada, M. Fujiwara, MHD instabilities and their effects on plasma confinement in Large Helical Device plasmas, Nuclear Fusion, 10.1088/0029-5515/44/2/001, 44, 2, 217-225, 2004.02, [URL], Characteristics of MHD instabilities and their impacts on plasma confinement are studied in current free plasmas of the Large Helical Device. Spontaneous L-H transition is often observed in high beta plasmas close to 2% at low toroidal fields (Bt ≤ 0.75 T). The stored energy starts to rise rapidly just after the transition accompanying the clear rise in the electron density but quickly saturates due to the growth of the m = 2/n = 3 mode (m and n: poloidal and toroidal mode numbers), the rational surface of which is located in the edge barrier region, and edge localized mode (ELM) like activities having fairly small amplitude but high repetition frequency. Even in low beta plasmas without L-H transitions, ELM-like activities are sometimes induced in high performance plasmas with a steep edge pressure gradient and transiently reduce the stored energy up to 10%. Energetic ion driven MHD modes such as Alfvén eigenmodes (AEs) are studied in a very wide range of characteristic parameters (the averaged beta of energetic ions, (β b∥), and the ratio of energetic ion velocity to the Alfvén velocity, Vb∥/VA), of which range includes all tokamak data. In addition to the observation of toroidicity induced AEs (TAEs), coherent magnetic fluctuations of helicity induced AEs (HAEs) have been detected for the first time in NBI heated plasmas. The transition of a core-localized TAE to a global AE (GAE) is also observed in a discharge with temporal evolution of the rotational transform profile, having a similarity to the phenomenon observed in a reversed shear tokamak. At low magnetic fields, bursting TAEs transiently induce a significant loss of energetic ions, up to 40% of injected beams, but on the other hand play an important role in triggering the formation of transport barriers in the core and edge regions..
364. K. Ida, S. Inagaki, N. Tamura, T. Morisaki, N. Ohyabu., K. Khlopenkov, S. Sudo, K. Watanabe, M. Yokoyama, T. Shimozuma, Y. Takeiri, K. Itoh, M. Yoshinuma, Y. Liang, K. Narihara, K. Tanaka, Y. Nagayama, T. Tokuzawa, K. Kawahata, H. Suzuki, A. Komori, T. Akiyama, N. Ashikawa, M. Emoto, H. Funaba, P. Goncharov, M. Goto, H. Idei, K. Ikeda, M. Isobe, O. Kaneko, H. Kawazome, T. Kobuchi, A. Kostrioukov, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nakamura, H. Nakanishi, Y. Narushima, K. Nishimura, N. Noda, T. Notake, H. Nozato, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, M. Shoji, N. Takeuchi, K. Toi, Y. Torii, K. Tsumori, T. Watari, Y. Xu, H. Yamada, I. Yamada, S. Yamamoto, T. Yamamoto, Y. Yoshimura, I. Ohtake, K. Ohkubo, T. Mito, T. Satow, T. Uda, K. Yamazaki, K. Matsuoka, O. Motojima, M. Fujiwara, Radial electric field and transport near the rational surface and the magnetic island in LHD, Nuclear Fusion, 10.1088/0029-5515/44/2/010, 44, 2, 290-295, 2004.02, [URL], The structure of the radial electric field and heat transport at the magnetic island in the large helical device (LHD) are investigated by measuring the radial profile of the poloidal flow with charge exchange spectroscopy and measuring the time evolution of the electron temperature with ECE. A vortex-like plasma flow along the magnetic flux surface inside the magnetic island is observed when the n/m = 1/1 external perturbation field becomes large enough to increase the magnetic island width above a critical range (15-20% of minor radius) in LHD. This convective poloidal flow results in a non-flat space potential inside the magnetic island. The sign of the curvature of the space potential (∂2Φ/∂r2, where Φ is the space potential) depends on the radial electric field at the boundary of the magnetic island. The heat transport inside the magnetic island is studied with a cold pulse propagation technique. The experimental results show the existence of radial electric field shear at the boundary of the magnetic island and a reduction in heat transport at the boundary and inside the magnetic island..
365. Takashi Mutoh, Ryuhei Kumazawa, Tetsuo Seki, Kenji Saito, Tetsuo Watari, Yuki Torii, Norio Takeuchi, Fujio Shimpo, Goro Nomura, Mitsuhiro Yokota, Tsuguhiro Watanabe, Masaki Osakabe, Mamiko Sasao, Sadayoshi Murakami, Tomoya Saida, Hiroyuki Okada, Yuichi Takase, Atsushi Fukuyama, Naoko Ashikawa, Masahiko Emoto, Hisamichi Funaba, Pavel R Goncharov, Motoshi Goto, Yasuji Hamada, Katsumi Ida, Hiroshi Idei, Katsunori Ikeda, Shinsaku Imagawa, Shigeru Inagaki, Mitsutaka Isobe, Takashi Kobuchi, Shin Kubo, Suguru Masuzaki, Keisuke Matsuoka, Takashi Minami, Toshiyuki Mito, Jyunichi Miyazawa, Tomohiro Morisaki, Shigeru Morita, Sadatsugu Muto, Yoshio Nagayama, Yukio Nakamura, Hideya Nakanishi, Kazumichi Narihara, Yoshiro Narushima, Kiyohiko Nishimura, Nobuaki Noda, Takashi Notake, Satoshi Ohdachi, Yoshihide Oka, Tetsuo Ozaki, Byron J Peterson, Akio Sagara, Satoru Sakakibara, Ryuichi Sakamoto, Kuninori Sato, Motoyasu Sato, Takashi Shimozuma, Mamoru Shoji, Hajime Suzuki, Long-pulse operation and high-energy particle confinement study in ICRF heating of LHD, Fusion science and technology, 46.0, 1.0, 175.0-183.0, 2004.01.
366. Nakamura, Kazuo; Ji, Zhenshan; Shen, Biao; Qin, Pinjian; Sato, Kohnosuke; Hanada, Kazuaki; Sakamoto, Mizuki; Idei, Hiroshi; Hasegawa, Makoto; Iyomasa, Atsuhiro; , Magnetic Sensorless Control of Plasma Position in the Superconducting Tokamak HT-7, Proc. Int. Conf. on Electrical Engineering, Vol. 1, No. , Pages 784-788, 2004.01.
367. H Idei, K Hanada, K Ohkubo, M Hasegawa, T Notake, S Kubo, T Shimozuma, S Ito, H Zushi, KN Sato, K Nakamura, M Sakamoto, A Iyomasa, H Hoshika, K Sasaki, S Kawasaki, H Nakashima, Remote Steering Antenna System and Its Application to ECH/ECCD Experiments on the TRIAM-1M tokamak, Proceedings of 13th Joint Workshop on ECE & ECRH, p. 326-331 (2004), 2004.01.
368. Takashi Mutoh, Ryuhei Kumazawa, Tetsuo Seki, Kenji Saito, Tetsuo Watari, Yuki Torii, Norio Takeuchi, Fujio Shimpo, Goro Nomura, Mitsuhiro Yokota, Tsuguhiro Watanabe, Masaki Osakabe, Mamiko Sasao, Sadayoshi Murakami, Tomoya Saida, Hiroyuki Okada, Yuichi Takase, Atsushi Fukuyama, Naoko Ashikawa, Masahiko Emoto, Hisamichi Funaba, Pavel R. Goncharov, Motoshi Goto, Yasuji Hamada, Katsumi Ida, Hiroshi Idei, Katsunori Ikeda, Shinsaku Imagawa, Inagaki Shigeru, Mitsutaka Isobe, Takashi Kobuchi, Shin Kubo, Suguru Masuzaki, Keisuke Matsuoka, Takashi Minami, Toshiyuki Mito, Jyunichi Miyazawa, Tomohiro Morisaki, Shigeru Morita, Sadatsugu Muto, Yoshio Nagayama, Yukio Nakamura, Hideya Nakanishi, Kazumichi Narihara, Yoshiro Narushima, Kiyohiko Nishimura, Nobuaki Noda, Takashi Notake, Satoshi Ohdachi, Yoshihide Oka, Tetsuo Ozaki, Byron J. Peterson, Akio Sagara, Satoru Sakakibara, Ryuichi Sakamoto, Kuninori Sato, Motoyasu Sato, Takashi Shimozuma, Mamoru Shoji, Hajime Suzuki, Yasuhiko Takeiri, Naoki Tamura, Kenji Tanaka, Kazuo Toi, Tokihiko Tokuzawa, Katsuyoshi Tsumori, Kiyomasa Watanabe, Hiroshi Yamada, Ichihiro Yamada, Kozo Yamazaki, Masayuki Yokoyama, Yasuo Yoshimura, Mikiro Yoshinuma, Osamu Kaneko, Kazuo Kawahata, Nobuyoshi Ohyabu, Kunizo Ohkubo, Akio Komori, Shigeru Sudo, Osamu Motojima, Long-pulse operation and high-energy particle confinement study in ICRF heating of LHD, Fusion Science and Technology, 10.13182/FST04-A553, 46, 1, 175-183, 2004.01, [URL], Long-pulse operation and high-energy particle confinement properties were studied using ion cyclotron range of frequencies (ICRF) heating for the Large Helical Device. For the minority-ion mode, ions with energies up to 500 keV were observed by concentrating the ICRF heating power near the plasma axis. The confinement of high-energy particles was studied using the power-modulation technique. This confirmed that the confinement of highenergy particles was better with the inward-shifted configuration than with the normal configuration. This behavior was the same for bulk plasma confinement. Long-pulse operation for more than 2 min was achieved during the experimental program in 2002. This was mainly due to better confinement of the helically trapped particles and accumulation of fewer impurities in the region of the plasma core, in conjunction with substantial hardware improvements. Currently, the plasma operation time is limited by an unexpected density rise due to out-gassing from the chamber materials. The temperature of the local carbon plates of the divertor exceeded 400°C, and a charge-coupled device camera observed the hot spots. The hot spot pattern was well explained by a calculation of the accelerated-particle orbits, and those accelerated particles came from outside the plasma near the ICRF antenna..
369. O. Motojima, H. Yamada, A. Komori, K. Y. Watanabe, T. Mutoh, Y. Takeiri, K. Ida, T. Akiyama, N. Asakura, N. Ashikawa, H. Chikaraishi, W. A. Cooper, M. Emoto, T. Fujita, M. Fujiwara, H. Funaba, P. Goncharov, M. Goto, Y. Hamada, S. Higashijima, T. Hino, M. Hoshino, M. Ichimura, Hiroshi Idei, T. Ido, K. Ikeda, S. Imagawa, Inagaki Shigeru, A. Isayama, M. Isobe, T. Itoh, K. Itoh, S. Kado, D. Kalinina, T. Kaneba, O. Kaneko, D. Kato, T. Kato, K. Kawahata, H. Kawashima, H. Kawazome, T. Kobuchi, K. Kondo, S. Kubo, R. Kumazawa, J. F. Lyon, R. Maekawa, A. Mase, S. Masuzaki, T. Mito, K. Matsuoka, Y. Miura, J. Miyazawa, R. More, T. Morisaki, S. Morita, I. Murakami, S. Murakami, S. Mutoh, K. Nagaoka, K. Nagasaki, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, H. Nishimura, K. Nishimura, M. Nishiura, A. Nishizawa, N. Noda, T. Notake, H. Nozato, S. Ohdachi, K. Ohkubo, N. Ohyabu, N. Oyama, Y. Oka, H. Okada, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, M. Sakamoto, R. Sakamoto, M. Sasao, R. Sato, T. Seki, T. Shimozuma, M. Shoji, S. Sudo, S. Takagi, Y. Takahashi, Y. Takase, H. Takenaga, N. Takeuchi, Review on the progress of the LHD experiment, Fusion Science and Technology, 10.13182/FST04-A535, 46, 1, 1-12, 2004.01, [URL], Recent progress in the Large Helical Device (LHD) experiment during the last 2 yr is reviewed. The LHD has been extending its operational regime toward fusion-relevant conditions while taking advantage of the net-current-free heliotron concept employing a superconducting coil system. Heating capability has exceeded 10 MW, and the central ion and electron temperatures have reached 7 and 10 keV, respectively. The maximum values of beta and pulse length have been extended to 3.2% and 150 s, respectively. Several encouraging phys ics observations have been obtained, i.e., simultaneous achievement of the mitigation of the magnetohydrodynamic instability criteria and good confinement, and formation of an internal transport barrier. The initial results have been obtained using a local island divertor, which shows the possibility of particle control at the plasma edge..
370. Ozaki, T., Goncharov, P., L, Jim, Murakami, S., Sudo, S., Nakanishi, H., Kojima, M., Yamauchi, K., Shoji, M., Kumazawa, R., Mutoh, T., Seki, T., Watari, T., Saito, K., Torii, H., Oka, Y., Osakabe, M., Takeiri, Y., Tsumori, K., Idei, H., High Energy Particle Measurements during Long Discharge in LHD, Jourinal of Plasma Fusion Research SERIES, 5, 201-204, 2003.12.
371. Motojima,O., Yamada, H., Ashikawa, N., Emoto, M., Funaba, H., Goto, M., Ida, K., Idei, H., Ikeda, K., Inagaki, S., Inoue, N., Isobe, M., Kaneko, O., Kawahata, K., Khlopenkov, K., Kobuchi, T., Komori, A., Kostrioukov, A., Kubo, S., Kumazawa, R., Resent Development of LHD Experiment, Journal of Plasma and Fusion Research SERIES, 5, 22-27, 2003.12.
372. Motojima, O; Ohyabu, N; Komori, A; Kaneko, O; Yamada, H; Kawahata, K; Nakamura, Y; Ida, K; Akiyama, T; Ashikawa, N; Cooper, WA; Ejiri, A; Emoto, M; Ezumi, N; Funaba, H; Fukuyama, A; Goncharov, P; Goto, M; Idei, H; Ikeda, K; Inagaki, S; Isobe, M; Kado, S; Kawazome, H; Khlopenkov, K; Kobuchi, T; Kondo, K; Kostrioukov, A; Kubo, S; Kumazawa, R; Liang, Y; Lyon, JF; Mase, A; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Murakami, S; Muto, S; Mutoh, T; Nagaoka, K; Nagayama, Y; Nakajima, N; Nakamura, K; Nakanishi, H; Narihara, K; Narushima, Y; Nishimura, K; Nishino, N; Noda, N; Notake, T; Nozato, H; Ohdachi, S; Oka, Y; Okada, H; Okamura, S; Osakabe, M; Ozaki, T; Peterson, BJ; Sagara, A; Saida, T; Saito, K; Sakakibara, S; Sakamoto, M; Sakamoto, R; Sasao, M; Sato, K; Sato, M; Seki, T; Shimozuma, T; Shoji, M; Suzuki, H; Takeiri, Y; Takeuchi, N; Tamura, N; Tanaka, K; Tanaka, MY; Teramachi, Y; Toi, K; Tokuzawa, T; Tomota, Y; Torii, Y; Tsumori, K; Watanabe, KY; Watari, T; Xu, Y; Yamada, I; Yamamoto, S; Yamamoto, T; Yokoyama, M; Yoshimura, S; Yoshimura, Y; Yoshinuma, M; Asakura, N; Fujita, T; Fukuda, T; Hatae, T; Higashijima, S; Isayama, A; Kamada, Y; Kubo, H; Kusama, Y; Miura, Y; Nakano, Y; Ninomiya, H; Oikawa, T; Oyama, N; Sakamoto, Y; Shinohara, K; Suzuki, T; Takenaga, H; Ushigusa, K; Hino, T; Ichimura, M; Takase, Y; Sano, F; Zushi, H; Satow, T; Imagawa, S; Mito, T; Ohtake, I; Uda, T; Itoh, K; Ohkubo, K; Sudo, S; Yamazaki, K; Matsuoka, K; Hamada, Y; Fujiwara, M, Recent advances in the LHD experiment, NUCLEAR FUSION, 10.1088/0029-5515/43/12/013, 43.0, 12.0, 1674.0-1683.0, PII S0029-5515(03)675-1, 2003.12, In the first four years of the LHD experiment, several encouraging results have emerged, the most significant of which is that MHD stability and good transport are compatible in the inward shifted axis configuration. The observed energy confinement at this optimal configuration is consistent with ISS95 scaling with an enhancement factor of 1.5. The confinement enhancement over the smaller heliotron devices is attributed to the high edge temperature. We find that the plasma with an average beta of 3% is stable in this configuration, even though the theoretical stability conditions of Mercier modes and pressure driven low-n modes are violated. In the low density discharges heated by NBI and ECR, internal transport barrier (ITB) and an associated high central temperature (> 10 keV) are seen. The radial electric field measured in these discharges is positive (electron root) and expected to play a key role in the formation of the ITB. The positive electric field is also found to suppress the ion thermal diffusivity as predicted by neoclassical transport theory. The width of the externally imposed island (n/m = 1/1) is found to decrease when the plasma is collisionless with finite beta and increase when the plasma is collisional. The ICRF heating in LHD is successful and a high energy tail (up to 500 keV) has been detected for minority ion heating, demonstrating good confinement of the high energy particles. The magnetic field line structure unique to the heliotron edge configuration is confirmed by measuring the plasma density and temperature profiles on the divertor plate. A long pulse (2 min) discharge with an ICRF power of 0.4 MW has been demonstrated and the energy confinement characteristics are almost the same as those in short pulse discharges..
373. H. Idei, T. Shimozuma, M. A.Shapiro, T. Notake, S. Kubo, R. J.Temkin, K. Ohkubo, Comparison between Retrieved and Measured Phase Profiles of Quasi-Optical Beams, The 28th International Conference on Infrared and Millimeter Waves, 351.0-352.0, Th3-1, 2003.10.
374. S Morita, M Goto, Y Takeiri, J Miyazawa, S Murakami, K Narihara, M Osakabe, K Yamazaki, T Akiyama, N Ashikawa, M Emoto, M Fujiwara, H Funaba, P Goncharov, Y Hamada, K Ida, H Idei, T Ido, K Ikeda, S Inagaki, M Isobe, K Itoh, O Kaneko, K Kawahata, H Kawazome, K Khlopenkov, T Kobuchi, A Komori, A Kostrioukov, S Kubo, R Kumazawa, Y Liang, S Masuzaki, K Matsuoka, T Minami, T Morisaki, O Motojima, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, Y Narushima, K Nishimura, A Nishizawa, N Noda, T Notake, H Nozato, S Ohdachi, K Ohkubo, N Ohyabu, Y Oka, T Ozaki, BJ Peterson, A Sagara, T Saida, K Saito, S Sakakibara, R Sakamoto, M Sasao, K Sato, M Sato, T Satow, T Seki, T Shimozuma, M Shoji, S Sudo, H Suzuki, N Takeuchi, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, T Uda, KY Watanabe, T Watari, Y Xu, H Yamada, I Yamada, S Yamamoto, T Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, Experimental study on ion temperature behaviours in ECH, ICRF and NBI H2, He and Ne discharges of the Large Helical Device, NUCLEAR FUSION, 43.0, 9.0, 899.0-909.0, 2003.09.
375. Y. Torii, R. Kumazawa, K. Saito, T. Watari, T. Watanabe, H. Idei, S. Kubo, T. Shoji, T. Mutoh, T. Seki, T. Yamamoto, N. Takeuchi, J. Xie, B. Wan, The propagation of ion Bernstein waves in heliotron/torsatron magnetic configurations, PHYSICS OF PLASMAS, Vol.10,3692-3702, 2003.09.
376. S. Morita, M. Goto, Y. Takeiri, J. Miyazawa, S. Murakami, K. Narihara, M. Osakabe, K. Yamazaki, T. Akiyama, N. Ashikawa, M. Emoto, M. Fujiwara, H. Funaba, P. Goncharov, Y. Hamada, K. Ida, Hiroshi Idei, T. Ido, K. Ikeda, Inagaki Shigeru, M. Isobe, K. Itoh, O. Kaneko, K. Kawahata, H. Kawazome, K. Khlopenkov, T. Kobuchi, A. Komori, A. Kostrioukov, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, K. Matsuoka, T. Minami, T. Morisaki, O. Motojima, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, Y. Narushima, K. Nishimura, A. Nishizawa, N. Noda, T. Notake, H. Nozato, S. Ohdachi, K. Ohkubo, N. Ohyabu, Y. Oka, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Satow, T. Seki, T. Shimozuma, M. Shoji, S. Sudo, H. Suzuki, N. Takeuchi, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Uda, K. Y. Watanabe, T. Watari, Y. Xu, H. Yamada, I. Yamada, S. Yamamoto, T. Yamamoto, M. Yokoyama, Y. Yoshimura, M. Yoshinuma, Experimental study on ion temperature behaviours in ECH, ICRF and NBI H2, He and Ne discharges of the large helical device, Nuclear Fusion, 10.1088/0029-5515/43/9/314, 43, 9, 899-909, 2003.09, [URL], Ion heating experiments have been carried out in the large helical device using ECH (82.5, 84.0, 168 GHz, ≤1 MW), ICRF (38.5 MHz, ≤2.7 MW) and NBI (H° beam: 160 keV, ≤9 MW). The central ion temperature has been observed from the Doppler broadening of Ti XXI (2.61 Å) and Ar XVII (3.95 Å) x-ray lines, which are measured using a newly installed crystal spectrometer with a charge-coupled device. Recently, in ECH discharges, on-axis heating became possible. As a result, a high Te (0) of 6-10 keV and a high ion temperature of 2.2 keV were obtained at ne = 0.6 × 1013 cm-3. A clear increment of Ti was also observed with the enhancement of the electron-ion energy flow when the ECH pulse was added to the NBI discharge. These results demonstrate the feasibility towards ECH ignition. A clear Ti increment was observed also in ICRF discharges at low density ranges of (0.4-0.6) × 1013 cm-3 with appearance of a new operational range of Ti(0) = 2.8 keV > Te(0) = 1.9 keV. In low power ICRF heating (1 MW), the fraction of bulk ion heating is estimated to be 60% of the total ICRF input power, which means Pi > Pe. Higher Ti(0), up to 3.5 keV, was obtained for a combined heating of NBI (≤4 MW) and ICRF (1 MW) at density ranges of (0.5-1.5) × 1013 cm-3. The highest Ti(0) of 5 keV was recorded in Ne NBI discharges at ne ≤ 1 × 1013 cm-3 with the achievement of Ti(0) > Te(0), whereas the Ti(0) remained at relatively low values of 2 keV in H2 and He NBI discharges due to less Pi. The main reasons for the high Ti achievement in the Ne discharges are: (1) 30% increment of deposition power, (2) increase in Pi/ni (five times, Pi/ni ≫ Pe/ne, Pi ≤ Pe) and (3) increase in τei (three times). The obtained Ti(0) data can be plotted by a smooth function of Pi/ni. This result strongly suggests that the ion temperature increases even in the H2 discharge if the Pi can be raised up..
377. Y. Torii, R. Kumazawa, K. Saito, T. Watari, T. Watanabe, Hiroshi Idei, S. Kubo, T. Shoji, T. Mutoh, T. Seki, T. Yamamoto, N. Takeuchi, J. Xie, B. Wan, The propagation of ion Bernstein waves in heliotron/torsatron magnetic configurations, Physics of Plasmas, 10.1063/1.1602453, 10, 9, 3692-3702, 2003.09, [URL], The propagation and absorption of ion Bernstein waves (IBW) in a helical system was investigated. IBW was excited using a folded waveguide antenna to improve energy confinement. It was found that the electron Landau damping was so strong that the IBW was absorbed before it reached the cyclotron resonance layer where ion heating was expected to occur. It was noted that the two cases of circular tokamak and straight helical configuration possessed their own symmetry..
378. H Yamada, S Murakami, K Yamazaki, O Kaneko, J Miyazawa, R Sakamoto, KY Watanabe, K Narihara, K Tanaka, S Sakakibara, M Osakabe, BJ Peterson, S Morita, K Ida, S Inagaki, S Masuzaki, T Morisaki, G Rewoldt, H Sugama, N Nakajima, WA Cooper, T Akiyama, N Ashikawa, M Emoto, H Funaba, P Goncharov, M Goto, H Idei, K Ikeda, M Isobe, K Kawahata, H Kawazome, K Khlopenkov, T Kobuchi, A Komori, A Kostrioukov, S Kubo, R Kumazawa, Y Liang, T Minami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, Y Narushima, K Nishimura, N Noda, T Notake, H Nozato, S Ohdachi, N Ohyabu, Y Oka, T Ozaki, A Sagara, T Saida, K Saito, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Takeuchi, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, T Watanabe, T Watari, Y Xu, I Yamada, S Yamamoto, T Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, T Mito, K Itoh, K Ohkubo, I Ohtake, T Satow, S Sudo, T Uda, K Matsuoka, O Motojima, Impact of heat deposition profile on global confinement of NBI heated plasmas in the LHD, NUCLEAR FUSION, 43.0, 8.0, 749.0, 2003.08.
379. T Mutoh, R Kumazawa, T Seki, K Saito, T Watari, Y Torii, N Takeuchi, T Yamamoto, F Shimpo, G Nomura, M Yokota, M Osakabe, M Sasao, S Murakami, T Ozaki, T Saida, YP Zhao, H Okada, Y Takase, A Fukuyama, N Ashikawa, M Emoto, H Funaba, P Goncharov, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, M Isobe, O Kaneko, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, A Kostrioukov, S Kubo, Y Liang, S Masuzaki, T Minami, T Mito, J Miyazawa, T Morisaki, S Morita, S Muto, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, Y Narushima, K Nishimura, N Noda, T Notake, S Ohdachi, I Ohtake, N Ohyabu, Y Oka, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, K Sato, M Sato, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Tamura, K Tanaka, K Toi, T Tokuzawa, K Tsumori, KY Watanabe, Y Xu, H Yamada, I Yamada, S Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, K Itoh, K Ohkubo, T Satow, S Sudo, T Uda, K Yamazaki, K Matsuoka, O Motojima, Y Hamada, M Fujiwara, Ion cyclotron range of frequencies heating and high-energy particle production in the Large Helical Device, NUCLEAR FUSION, 43.0, 8.0, 738.0, 2003.08.
380. H. Yamada, S. Murakami, K. Yamazaki, O. Kaneko, J. Miyazawa, R. Sakamoto, K. Y. Watanabe, K. Narihara, K. Tanaka, S. Sakakibara, M. Osakabe, B. J. Peterson, S. Morita, K. Ida, Inagaki Shigeru, S. Masuzaki, T. Morisaki, G. Rewoldt, H. Sugama, N. Nakajima, W. A. Cooper, T. Akiyama, N. Ashikawa, M. Emoto, H. Funaba, P. Goncharov, M. Goto, Hiroshi Idei, K. Ikeda, M. Isobe, K. Kawahata, H. Kawazome, K. Khlopenkov, T. Kobuchi, A. Komori, A. Kostrioukov, S. Kubo, R. Kumazawa, Y. Liang, T. Minami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, Y. Narushima, K. Nishimura, N. Noda, T. Notake, H. Nozato, S. Ohdachi, N. Ohyabu, Y. Oka, T. Ozaki, A. Sagara, T. Saida, K. Saito, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Takeuchi, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Watanabe, T. Watari, Y. Xu, I. Yamada, S. Yamamoto, T. Yamamoto, M. Yokoyama, Y. Yoshimura, M. Yoshinuma, T. Mito, K. Itoh, K. Ohkubo, I. Ohtake, T. Satow, S. Sudo, T. Uda, K. Matsuoka, O. Motojima, Impact of heat deposition profile on global confinement of NBI heated plasmas in the LHD, Nuclear Fusion, 10.1088/0029-5515/43/8/317, 43, 8, 749-755, 2003.08, [URL], Energy confinement and heat transport of net-current-free NBI heated plasmas in the large helical device (LHD) are discussed with emphasis on density and power deposition profile dependences. Although the apparent density dependence of the energy confinement time has been demonstrated in a wide parameter range in LHD, the loss of this dependence has been observed in the high density regime under specific conditions. Broad heat deposition due to off-axis alignment and shallow penetration of neutral beams degrades the global energy confinement while the local heat transport maintains a clear temperature dependence, lying between Bohm and gyro-Bohm characteristics. The central heat deposition tends towards an intrinsic density dependence like τE ∝ (n̄e/P)0.6 from the state where density dependence is lost. The broadening of the temperature profile due to the broad heat deposition profile contrasts with the invariant property that has been observed widely as profile resilience or stiffness in tokamak experiments. The confinement improvement as a result of the inward shift of the magnetic axis is obvious in the core region, which emphasizes the improvement of transport because of the geometry being unfavourable for the central heating of NBI in this configuration. The edge pressure, clearly, does not depend on the magnetic axis position. Unlike a tokamak H-mode, the edge pressure is determined by transport and can be increased by increasing the heating power..
381. T. Mutoh, R. Kumazawa, T. Seki, K. Saito, T. Watari, Y. Torii, N. Takeuchi, T. Yamamoto, F. Shimpo, G. Nomura, M. Yokota, M. Osakabe, M. Sasao, S. Murakami, T. Ozaki, T. Saida, Y. P. Zhao, H. Okada, Y. Takase, A. Fukuyama, N. Ashikawa, M. Emoto, H. Funaba, P. Goncharov, M. Goto, K. Ida, H. Idei, K. Ikeda, S. Inagaki, M. Isobe, O. Kaneko, K. Kawahata, K. Khlopenkov, T. Kobuchi, A. Komori, A. Kostrioukov, S. Kubo, Y. Liang, S. Masuzaki, T. Minami, T. Mito, J. Miyazawa, T. Morisaki, S. Morita, S. Muto, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, I. Ohtake, N. Ohyabu, Y. Oka, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Y. Watanabe, Y. Xu, H. Yamada, I. Yamada, S. Yamamoto, M. Yokoyama, Y. Yoshimura, M. Yoshinuma, K. Itoh, K. Ohkubo, T. Satow, S. Sudo, T. Uda, K. Yamazaki, K. Matsuoka, O. Motojima, Y. Hamada, M. Fujiwara, Ion cyclotron range of frequencies heating and high-energy particle production in the Large Helical Device, Nuclear Fusion, 10.1088/0029-5515/43/8/315, 43, 8, 738-743, 2003.08, [URL], Significant progress has been made with ion cyclotron range of frequencies (ICRF) heating in the Large Helical Device. This is mainly due to better confinement of the helically trapped particles and less accumulation of impurities in the region of the plasma core. During the past two years, ICRF heating power has been increased from 1.35 to 2.7 MW. Various wave-mode tests were carried out using minority-ion heating, second-harmonic heating, slow-wave heating and high-density fast-wave heating at the fundamental cyclotron frequency. This fundamental heating mode extended the plasma density range of effective ICRF heating to a value of 1 × 1020m-3. This use of the heating mode was its first successful application in large fusion devices. Using the minority-ion mode gave the best performance, and the stored energy reached 240 kJ using ICRF alone. This was obtained for the inward-shifted magnetic axis configuration. The improvement associated with the axis-shift was common for both bulk plasma and highly accelerated particles. For the minority-ion mode, high-energy ions up to 500 keV were observed by concentrating the heating power near the plasma axis. The confinement properties of high-energy particles were studied for different magnetic axis configurations, using the power-modulation technique. It confirmed that with the inward-shifted configuration the confinement of high-energy particles was better than with the normal configuration. By increasing the distance of the plasma to the vessel wall to about 2 cm, the impurity influx was sufficiently reduced to allow sustainment of the plasma with ICRF heating alone for more than 2 min..
382. K Ohkubo, S Kubo, T Shimozuma, H Idei, Y Yoshimura, T Notake, W Kasparek, Extension of steering angle in a square corrugated waveguide antenna, FUSION ENGINEERING AND DESIGN, 65.0, 4.0, 657.0-672.0, 2003.07.
383. T Shimozuma, S Kubo, H Idei, Y Yoshimura, T Notake, K Ida, N Ohyabu, I Yamada, K Narihara, S Inagaki, Y Nagayama, Y Takeiri, H Funaba, S Muto, K Tanaka, M Yokoyama, S Murakami, M Osakabe, R Kumazawa, N Ashikawa, M Emoto, M Goto, K Ikeda, M Isobe, T Kobichi, Y Liang, S Masuzaki, T Minami, J Miyazawa, S Morita, T Morisaki, T Mutoh, H Nakanishi, K Nishimura, N Noda, S Ohdachi, Y Oka, T Ozaki, B J Peterson, Y Narushima, A Sagara, K Saito, S Sakakibara, R Sakamoto, M Sasao, M Sato, K Satoh, T Seki, S Shoji, H Suzuki, N Tamura, K Tokuzawa, Y Torii, K Toi, K Tsumori, K Y Watanabe, T Watari, S Yamamoto, T Yamamoto, M Yoshinuma, K Yamazaki, S Sudo, K Ohkubo, K Itoh, A Komori, H Yamada, O Kaneko, Y Nakamura, K Kawahata, K Matsuoka, O Motojima and the LHD Experimental Group, Formation of Electron Internal Transport Barriers by Highly Localized Electron Cyclotron Resonance Heating in the Large Helical Device, PLASMA PHYSICS AND CONTROLLED FUSION, 45.0, 7.0, 1183.0-1192.0, 2003.07.
384. K. Ohkubo, S. Kubo, T. Shimozuma, Hiroshi Idei, Y. Yoshimura, T. Notake, W. Kasparek, Extension of steering angle in a square corrugated waveguide antenna, Fusion Engineering and Design, 10.1016/S0920-3796(03)00385-5, 65, 4, 657-672, 2003.07, [URL], A theoretical study of the square waveguide antenna with corrugated walls was carried out with reference to experimental results. When the length of the waveguide, to which the Gaussian beam is injected obliquely, is changed, a recursive Gaussian beam with high efficiency radiates from the waveguide exit in the asymmetric or symmetric direction with respect to a waveguide axis at almost the same interval. Because the optimum waveguide length for maximum efficiency decreases stepwise with increasing injection angle, adjustment of the waveguide length is not continuous but discrete. This method enables the injection angle, which is limited to 10° in a fixed waveguide length, to be increased by about two times. This is applicable to an antenna for an ITER-electron cyclotron heating/current drive and also to a launcher for a small machine with a narrow port where a steering mirror cannot be installed..
385. T. Shimozuma, S. Kubo, H. Idei, Y. Yoshimura, T. Notake, K. Ida, N. Ohyabu, I. Yamada, K. Narihara, S. Inagaki, Y. Nagayama, Y. Takeiri, H. Funaba, S. Muto, K. Tanaka, M. Yokoyama, S. Murakami, M. Osakabe, R. Kumazawa, N. Ashikawa, M. Emoto, M. Goto, K. Ikeda, M. Isobe, T. Kobichi, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, S. Morita, T. Morisaki, T. Mutoh, H. Nakanishi, K. Nishimura, N. Noda, S. Ohdachi, Y. Oka, T. Ozaki, B. J. Peterson, Y. Narushima, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, M. Sato, K. Satoh, T. Seki, S. Shoji, H. Suzuki, N. Tamura, K. Tokuzawa, Y. Torii, K. Toi, K. Tsumori, K. Y. Watanabe, T. Watari, S. Yamamoto, T. Yamamoto, M. Yoshinuma, K. Yamazaki, S. Sudo, K. Ohkubo, K. Itoh, A. Komori, H. Yamada, O. Kaneko, Y. Nakamura, K. Kawahata, K. Matsuoka, O. Motojima, Formation of electron internal transport barriers by highly localized electron cyclotron resonance heating in the large helical device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/45/7/310, 45, 7, 1183-1192, 2003.07, [URL], The characteristics of electron internal transport barriers (eITB) formation were investigated. The experimental investigations were carried out in relation to the electron cyclotron resonance heating (ECH) injection condition by means of diagnostics with high spatial and time resolution. Improvement of thermal transport within the eITB was confirmed by the analysis of energy transport and the transient response of the radiative temperature..
386. R Kumazawa, K Saito, Y Torii, T Mutoh, T Seki, T Watari, M Osakabe, S Murakami, M Sasao, T Watanabe, T Yamamoto, T Notake, N Takeuchi, T Saida, F Shimpo, G Nomura, M Yokota, A Kato, Y Zao, H Okada, M Isobe, T Ozaki, K Narihara, Y Nagayama, S Inagaki, S Morita, AV Krasilnikov, H Idei, S Kubo, K Ohkubo, M Sato, T Shimozuma, Y Yoshimura, K Ikeda, K Nagaoka, Y Oka, Y Takeiri, K Tsumori, N Ashikawa, M Emoto, H Funaba, M Goto, K Ida, T Kobuchi, Y Liang, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Muto, Y Nakamura, H Nakanishi, K Nishimura, N Noda, S Ohdachi, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, K Sato, M Shoji, H Suzuki, K Tanaka, K Toi, T Tokuzawa, KY Watanabe, I Yamada, S Yamamoto, M Yoshinuma, M Yokoyama, O Kaneko, K Kawahata, A Komori, N Ohyabu, H Yamada, K Yamazaki, S Sudo, K Matsuoka, Y Hamada, O Motojima, M Fujiwara, Confinement characteristics of high-energy ions produced by ICRF heating in the large helical device, PLASMA PHYSICS AND CONTROLLED FUSION, 45.0, 6.0, 1037.0, 2003.06.
387. R. Kumazawa, K. Saito, Y. Torii, T. Mutoh, T. Seki, T. Watari, M. Osakabe, S. Murakami, M. Sasao, T. Watanabe, T. Yamamoto, T. Notake, N. Takeuchi, T. Saida, F. Shimpo, G. Nomura, M. Yokota, A. Kato, Y. Zao, H. Okada, M. Isobe, T. Ozaki, K. Narihara, Y. Nagayama, Inagaki Shigeru, S. Morita, A. V. Krasilnikov, Hiroshi Idei, S. Kubo, K. Ohkubo, M. Sato, T. Shimozuma, Y. Yoshimura, K. Ikeda, K. Nagaoka, Y. Oka, Y. Takeiri, K. Tsumori, N. Ashikawa, M. Emoto, H. Funaba, M. Goto, K. Ida, T. Kobuchi, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Muto, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, S. Ohdachi, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, K. Sato, M. Shoji, H. Suzuki, K. Tanaka, K. Toi, T. Tokuzawa, K. Y. Watanabe, I. Yamada, S. Yamamoto, M. Yoshinuma, M. Yokoyama, K. Y. Watanabe, O. Kaneko, K. Kawahata, A. Komori, N. Ohyabu, H. Yamada, K. Yamazaki, S. Sudo, K. Matsuoka, Y. Hamada, O. Motojima, M. Fujiwara, Confinement characteristics of high-energy ions produced by ICRF heating in the large helical device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/45/6/315, 45, 6, 1037-1050, 2003.06, [URL], The behaviour of high-energy ions accelerated by an ion cyclotron range of frequency (ICRF) electric field in the large helical device (LHD) is discussed. A better confinement performance of high-energy ions in the inward-shifted magnetic axis configuration was experimentally verified by measuring their energy spectrum and comparing it with the effective temperature determined by an electron slowing down process. In the standard magnetic axis configuration a saturation of the measured tail temperature was observed as the effective temperature was increased. The ratio between these two quantities is a measure of the quality of transfer efficiency from high-energy ions to a bulk plasma; when this efficiency was compared with Monte Carlo simulations the results agreed fairly well. The ratio of the stored energy of the high-energy ions to that of the bulk plasma was measured using an ICRF heating power modulation method; it was deduced from phase differences between total and bulk plasma stored energies and the modulated ICRF heating power. The measured high energy fraction agreed with that calculated using the injected ICRF heating power, the transfer efficiency determined in the experiment and the confinement scaling of the LHD plasma..
388. Yasuhiko Takeiri, T Shimozuma, S Kubo, S Morita, M Osakabe, O Kaneko, K Tsumori, Y Oka, K Ikeda, K Nagaoka, N Ohyabu, K Ida, M Yokoyama, J Miyazawa, M Goto, K Narihara, I Yamada, H Idei, Y Yoshimura, N Ashikawa, M Emoto, H Funaba, S Inagaki, M Isobe, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, A Kostrioukov, R Kumazawa, Y Liang, S Masuzaki, T Minami, T Morisaki, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, Y Narushima, K Nishimura, N Noda, S Ohdachi, T Ozaki, BJ Peterson, A Sagara, K Saito, S Sakakibara, R Sakamoto, M Sasao, K Sato, M Sato, T Seki, M Shoji, H Suzuki, N Tamura, K Tanaka, K Toi, T Tokuzawa, KY Watanabe, T Watari, Y Xu, H Yamada, M Yoshinuma, K Itoh, K Ohkubo, T Satow, S Sudo, T Uda, K Yamazaki, Y Hamada, K Matsuoka, O Motojima, M Fujiwara, T Notake, N Takeuchi, Y Torii, S Yamamoto, T Yamamoto, T Akiyama, P Goncharov, T Saida, H Kawazome, H Nozato, Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device, PHYSICS OF PLASMAS, 10.0, 5.0, 1788.0-1795.0, 2003.05.
389. A Komori, N Ohyabu, H Yamada, O Kaneko, K Kawahata, K Ida, Y Nakamura, T Akiyama, N Ashikawa, M Emoto, H Funaba, P Goncharov, M Goto, H Idei, K Ikeda, S Inagaki, M Isobe, H Kawazome, K Khlopenkov, T Kobuchi, A Kostrioukov, S Kubo, R Kumazawa, Y Liang, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, H Nakanishi, K Narihara, Y Narushima, K Nishimura, N Noda, T Notake, H Nozato, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, T Saida, K Saito, S Sakakibara, R Sakamoto, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Takeuchi, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, KY Watanabe, T Watari, Y Xu, I Yamada, S Yamamoto, T Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, K Itoh, K Matsuoka, K Ohkubo, T Satow, S Sudo, T Uda, K Yamazaki, O Motojima, M Fujiwara, Recent results from the large helical device, PLASMA PHYSICS AND CONTROLLED FUSION, 45.0, 5.0, 671.0, 2003.05.
390. Y Nagayama, K Kawahata, S Inagaki, BJ Peterson, S Sakakibara, K Tanaka, T Tokuzawa, KY Watanabe, N Ashikawa, H Chikaraishi, M Emoto, H Funaba, M Goto, Y Hamada, K Ichiguchi, K Ida, H Idei, T Ido, K Ikeda, S Imagawa, A Isayama, M Isobe, A Iwamoto, O Kaneko, S Kitagawa, A Komori, S Kubo, R Kumazawa, S Masuzaki, K Matsuoka, T Mito, J Miyazawa, T Morisaki, S Morita, O Motojima, S Murakami, T Mutoh, S Muto, N Nakajima, Y Nakamura, H Nakanishi, K Narihara, Y Narushima, A Nishimura, K Nishimura, A Nishizawa, N Noda, S Ohdachi, K Ohkubo, N Ohyabu, Y Oka, M Osakabe, T Ozaki, A Sagara, K Saito, R Sakamoto, M Sasao, K Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, S Sudo, K Takahata, Y Takeiri, K Toi, K Tsumori, H Yamada, I Yamada, K Yamazaki, N Yanagi, M Yokoyama, Y Yoshimura, Y Yoshinuma, T Watari, LHD Group, Sawtooth oscillation in current-carrying plasma in the Large Helical Device, Physical review letters, 90.0, 20.0, Article No. 205001, 2003.05.
391. Y. Takeiri, T. Shimozuma, S. Kubo, S. Morita, M. Osakabe, O. Kaneko, K. Tsumori, Y. Oka, K. Ikeda, K. Nagaoka, N. Ohyabu, K. Ida, M. Yokoyama, J. Miyazawa, M. Goto, K. Narihara, I. Yamada, H. Idei, Y. Yoshimura, N. Ashikawa, M. Emoto, H. Funaba, S. Inagaki, M. Isobe, K. Kawahata, K. Khlopenkov, T. Kobuchi, A. Komori, A. Kostrioukov, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, T. Morisaki, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, Y. Narushima, K. Nishimura, M. Noda, S. Ohdachi, T. Ozaki, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, M. Shoji, H. Suzuki, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, K. Y. Watanabe, T. Watari, Y. Xu, H. Yamada, M. Yoshinuma, K. Itoh, K. Ohkubo, T. Satow, S. Sudo, T. Uda, K. Yamazaki, Y. Hamada, K. Matsuoka, O. Motojima, M. Fujiwara, T. Notake, N. Takeuchi, Y. Torii, S. Yamamoto, T. Yamamoto, T. Akiyama, P. Goncharov, T. Saida, H. Kawazome, H. Nozato, Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device, Physics of Plasmas, 10.1063/1.1560613, 10, 5 II, 1788-1795, 2003.05, [URL], The formation of electron internal transport barrier (ITB) and achievement of higher ion temperature in large helical device was discussed. The formation of the electron-ITB was correlated with the neoclassical electron root with a strong radical electric field determined by the neoclassical ambipolar flux. As for the ion temperature, high-power neutral beam injection (NBI) heating of 9 MW had realised a central ion temperature of 5 KeV with neon injection..
392. A. Komori, N. Ohyabu, H. Yamada, O. Kaneko, K. Kawahata, K. Ida, Y. Nakamura, T. Akiyama, N. Ashikawa, M. Emoto, H. Funaba, P. Goncharov, M. Goto, H. Idei, K. Ikeda, S. Inagaki, M. Isobe, H. Kawazome, K. Khlopenkov, T. Kobuichi, A. Kostrioukov, Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, H. Nakanishi, K. Narihara, Y. Narushima, K. Nishimura, N. Noda, T. Notake, H. Nozato, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Takeuchi, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, K. Y. Watanabe, T. Watari, Y. Xu, I. Yamada, S. Yamamoto, T. Yamamoto, M. Yokoyama, Y. Yoshimura, M. Yoshinuma, K. Itoh, K. Matsuoka, K. Ohkubo, T. Satow, S. Sudo, T. Uda, K. Yamazaki, O. Motojima, M. Fujiwara, Recent results from the Large Helical Device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/45/5/311, 45, 5, 671-686, 2003.05, [URL], The most important finding in the Large Helical Device (LHD) experiments so far is that an inward-shifted configuration exhibits good plasma performance with a scaling similar to that of ELMy H-mode tokamaks. The inward-shifted configuration has been predicted to have unfavourable magnetohydrodynamic (MHD) properties, even though it has significantly better particle-orbit properties. However, no serious confinement degradation due to the MHD activities was observed, resolving favourably the potential conflict between stability and confinement. Neoclassical transport loss can be suppressed even in a low-collisionality regime, and in this way the inward-shifted configuration was shown to make the LHD plasma properties favourable. Then, it is very important to realize more improved plasma performance and higher temperature plasmas for extending the plasma-parameter regime in order to obtain data that can be extrapolated to a reactor. In the fifth campaign in 2001-2002, an increase in the heating power achieved an electron temperature Te of over 10 keV and an ion temperature Ti of 5 keV. A Te profile, which is characteristic of internal transport barriers, was also observed when the electron cyclotron resonance heating power was highly focused on the centre of the plasma sustained by neutral beam injection..
393. Y. Nagayama, K. Kawahata, Inagaki Shigeru, B. J. Peterson, S. Sakakibara, K. Tanaka, T. Tokuzawa, K. Y. Watanabe, N. Ashikawa, H. Chikaraishi, M. Emoto, H. Funaba, M. Goto, Y. Hamada, K. Ichiguchi, K. Ida, Hiroshi Idei, T. Ido, K. Ikeda, S. Imagawa, A. Isayama, M. Isobe, A. Iwamoto, O. Kaneko, S. Kitagawa, A. Komori, S. Kubo, R. Kumazawa, S. Masuzaki, K. Matsuoka, T. Mito, J. Miyazawa, T. Morisaki, S. Morita, O. Motojima, S. Murakami, T. Mutoh, S. Muto, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, A. Nishimura, K. Nishimura, A. Nishizawa, N. Noda, S. Ohdachi, K. Ohkubo, N. Ohyabu, Y. Oka, M. Osakabe, T. Ozaki, A. Sagara, K. Saito, R. Sakamoto, M. Sasao, K. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, S. Sudo, K. Takahata, Y. Takeiri, K. Toi, K. Tsumori, H. Yamada, I. Yamada, K. Yamazaki, N. Yanagi, M. Yokoyama, Y. Yoshimura, Y. Yoshinuma, T. Watari, Sawtooth oscillation in current-carrying plasma in the large helical device, Physical Review Letters, 90, 20, 2003.05, By using the ECE diagnostics, new types of sawtooth crashes in helical plasmas in LHD were discovered. One is the full sawtooth crash in the case of countercurrent, and another is the annular crash in the case of cocurrent. The plasma confinement is slightly degraded due to the sawtooth oscillation. An observed rapid mixture of the plasma in the limited region suggests that sawtooth crashes in LHD are reconnection phenomena..
394. W. Kasparek, H. Idei, S. Kubo, T. Notake, Beam waveguide reflector with integrated direction-finding antenna for in-situ alignment, International Journal of Infrared and Millimeter Waves, 24.0, 4.0, 451.0-472.0, Vol.24(4),p.451-472, 2003.04, An in-situ alignment system for beam waveguides based on an interferometric direction-finding antenna was investigated numerically and experimentally. The system consists of a reflector with four off-central positioned waveguide couplers in two directions. By nulling the difference of the power signals as well as the mixing signal from each coupler pair, spatial and angular alignments of a beam impinging on the mirror can be performed.
In this paper, the characteristics of such a mirror are presented, and the design of a prototype intended for use in an ECH transmission line at LHD is described. Low-power as well as high-power tests at a frequency of 82.7 GHz were carried out, and the results are discussed. The device shows a high performance in agreement with theory..
395. Y Nakamura, Y Takeiri, R Kumazawa, M Osakabe, T Seki, BJ Peterson, K Ida, H Funaba, M Yokoyama, N Tamura, A Komori, S Morita, K Sato, K Narihara, S Inagaki, T Tokuzawa, S Masuzaki, J Miyazawa, N Noda, T Mutoh, T Shimozuma, K Kawahata, Y Oka, H Suzuki, N Ohyabu, T Akiyama, N Ashikawa, M Emoto, P Goncharov, M Goto, H Idei, K Ikeda, S Imagawa, M Isobe, O Kaneko, H Kawazome, K Khlopenkov, T Kobuchi, A Kostrioukov, S Kubo, Y Liang, T Minami, T Morisaki, S Murakami, S Muto, K Nagaoka, Y Nagayama, H Nakanishi, Y Narushima, K Nishimura, T Notake, H Nozato, S Ohdachi, S Okamura, T Ozaki, A Sagara, T Saida, K Saito, S Sakakibara, R Sakamoto, M Sasao, M Sato, M Shoji, N Takeuchi, K Tanaka, MY Tanaka, K Toi, Y Torii, K Tsumori, KY Watanabe, T Watari, Y Xu, H Yamada, I Yamada, S Yamamoto, T Yamamoto, S Yoshimura, Y Yoshimura, M Yoshinuma, K Itoh, T Mito, K Ohkubo, I Ohtake, T Satow, S Sudo, T Uda, K Yamazaki, K Matsuoka, O Motojima, Y Hamada, M Fujiwara, Plasma performance and impurity behaviour in long pulse discharges on LHD, NUCLEAR FUSION, Vol. 43, No. 4, Pages 219, 2003.04.
396. W. Kasparek, Hiroshi Idei, S. Kubo, T. Notake, Beam waveguide reflector with integrated direction-finding antenna for in-situ alignment, International Journal of Infrared and Millimeter Waves, 10.1023/A:1022468412389, 24, 4, 451-472, 2003.04, [URL], An in-situ alignment system for beam waveguides based on an interferometric direction-finding antenna was investigated numerically and experimentally. The system consists of a reflector with four off-central positioned waveguide couplers in two directions. By nulling the difference of the power signals as well as the mixing signal from each coupler pair, spatial and angular alignments of a beam impinging on the mirror can be performed. In this paper, the characteristics of such a mirror are presented, and the design of a prototype intended for use in an ECH transmission line at LHD is described. Low-power as well as high-power tests at a frequency of 82.7 GHz were carried out, and the results are discussed. The device shows a high performance in agreement with theory..
397. Y. Nakamura, Y. Takeiri, R. Kumazawa, M. Osakabe, T. Seki, B. J. Peterson, K. Ida, H. Funaba, M. Yokoyama, N. Tamura, A. Komori, S. Morita, K. Sato, K. Narihara, Inagaki Shigeru, T. Tokuzawa, S. Masuzaki, J. Miyazawa, N. Noda, T. Mutoh, T. Shimozuma, K. Kawahata, Y. Oka, H. Suzuki, N. Ohyabu, T. Akiyama, N. Ashikawa, M. Emoto, P. Goncharov, M. Goto, Hiroshi Idei, K. Ikeda, S. Imagawa, M. Isobe, O. Kaneko, H. Kawazome, K. Khlopenkov, T. Kobuchi, A. Kostrioukov, S. Kubo, Y. Liang, T. Minami, T. Morisaki, S. Murakami, S. Muto, K. Nagaoka, Y. Nagayama, H. Nakanishi, Y. Narushima, K. Nishimura, T. Notake, H. Nozato, S. Ohdachi, S. Okamura, T. Ozaki, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, M. Sato, M. Shoji, N. Takeuchi, K. Tanaka, M. Y. Tanaka, K. Toi, Y. Torii, K. Tsumori, K. Y. Watanabe, T. Watari, Y. Xu, H. Yamada, I. Yamada, S. Yamamoto, T. Yamamoto, S. Yoshimura, Y. Yoshimura, M. Yoshinuma, K. Itoh, T. Mito, K. Ohkubo, I. Ohtake, T. Satow, S. Sudo, T. Uda, K. Yamazaki, K. Matsuoka, O. Motojima, Y. Hamada, M. Fujiwara, Plasma performance and impurity behaviour in long pulse discharges on LHD, Nuclear Fusion, 10.1088/0029-5515/43/4/301, 43, 4, 219-227, 2003.04, [URL], The superconducting machine LHD has conducted long pulse experiments for four years to achieve long-duration plasmas with high performance. The operational regime was largely extended in discharge duration and plasma density. In this paper, the plasma characteristics, in particular, plasma performance and impurity behaviour in long pulse discharges are described. Confinement studies show that global energy confinement times are comparable to those in short pulse discharges. Long sustainment of high performance plasma, which is equivalent to the previous achievement in other devices, was demonstrated. Long pulse discharges enabled us to investigate impurity behaviour in a long timescale. Intrinsic metallic impurity accumulation was observed in a narrow density window (2-3 × 1019 m-3) only for hydrogen discharges. Impurity transport study by using active impurity pellet injection shows a long impurity confinement time and an inward convection in the impurity accumulation window, which is consistent with the intrinsic impurity behaviour. The pulsed neon gas injection experiment shows that the neon penetration into the plasma core is caused by the inward convection due to radial electric field. Finally, impurity accumulation control with an externally induced magnetic island at the plasma edge was demonstrated..
398. S Muto, S Morita, S Kubo, T Shimozuma, H Idei, Y Yoshimura, First measurement of hard x-ray spectrum emitted from high-energy electrons in electron cyclotron heated plasma of LHD, REVIEW OF SCIENTIFIC INSTRUMENTS, 74.0, 3.0, 1993.0-1996.0, 2003.03.
399. S. Muto, S. Morita, S. Kubo, T. Shimozuma, Hiroshi Idei, Y. Yoshimura, First measurement of hard x-ray spectrum emitted from high-energy electrons in electron cyclotron heated plasma of LHD, Review of Scientific Instruments, 10.1063/1.1538329, 74, 3 II, 1993-1996, 2003.03, [URL], The measurement of hard x-ray spectrum emitted from high-energy electrons in electron cyclotron heated plasma was analysed. The measurement was taken with an x-ray pulse-height analyzer installed on a horizontal port of large helical device. The apparatus was equipped with filter and collimators and data-acquisition system was operated with a high counting rate..
400. Tetsuo Ozaki, Sadayoshi Murakami, Pavel Goncharov, Tsuguhiro Watanabe, Shigeru Sudo, Kazumichi Narihara, Kenji Tanaka, Shin Kubo, Takashi Simozuma, Hiroshi Idei, Yoshihide Oka, Masaki Osakabe, Yasuhiko Takeiri, Katsuyoshi Tsumori, Katsumi Ida, Mamoru Shoji, Hideya Nakanishi, Mamiko Sasao, Osamu Kaneko, Kazuo Kawahata, Yukio Nakamura, Nobuyoshi Ohyabu, Osamu Motojima, Spatial resolved high-energy particle diagnostic system using time-of-flight neutral particle analyzer in Large Helical Device, Proceedings of the 14th Topical Conference on High - Temperature Plasma Diagnostics
Review of Scientific Instruments
, 10.1063/1.1537883, 74, 3 II, 1878-1882, 2003.03, [URL], The time-of-flight-type neutral particle analyzer, which was able of horizontal continuous scanning during long discharges, was operated in large helical device. Experiments for the comparison between the co- and counter neutral beam injection were performed. It was found that the particle with large pitch angle was lost in the counter injection from the spectrum of the pitch angle distribution of the neutral particles..
401. T Shimozuma, S Kubo, H Idei, Y Yoshimura, T Notake, T Watari, Y Mizuno, S Ito, S Kobayashi, Y Takita, K Narihara, I Yamada, N Ohyabu, K Ida, S Inagaki, Y Nagayama, Y Takeiri, H Funaba, M Yokoyama, S Murakami, M Emoto, M Goto, K Ikeda, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, S Morita, T Morisaki, S Muto, T Mutoh, H Nakanishi, Y Narushima, K Nishimura, N Noda, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, M Sasao, M Sato, K Satoh, T Seki, S Shoji, H Suzuki, K Tanaka, K Toi, K Tokuzawa, K Tsumori, KY Watanabe, M Yoshinuma, K Kawahata, Y Nakamura, H Yamada, O Kaneko, A Komori, K Yamazaki, K Ohkubo, S Sudo, K Itoh, K Matsuoka, O Motojima, ECRH Experiments in an Extended Power Regime on the Large Helical Device, The 12th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating, 1.0, 359.0-364.0, (ISBN-981-238-189-9), 2003.02.
402. Kubo,S., Idei,H., Shimozuma,T., Yoshimura, Y., Notake, T., Ohkubo, K., Inagaki, S., Nagayama, Y., Narihara, K. and LHD Experimental Group, ECH Power Modulation Experiments in LHD, Journal of Plasma and Fusion Research SERIES, 5, 584-587, 2003.01.
403. H. Idei, T. Notake, T. Shimozuma, S. Ito, S. Kubo, M. A.Shapiro, R. J.Temkin, Evaluation of Correcting Mirrors for a Gyrotron in the Large Helical Device, The 26th International Conference on Infrared and Millimeter Waves, 5,p.208-211, 2003.01.
404. H Idei, S Kubo, T Shimozuma, K Tsumori, T Watari, T Notake, S Ito, S Kobayashi, Y Mizuno, Y Takita, Y Yoshimura, K Ohkubo, S Sakakibara, K Narihara, I Yamada, K Tanaka, T Morisaki, KY Watanabe, H Nakanishi, S Ohdachi, M Emoto, K Matsuoka, O Motojima, M Fujiwara, Evolution of Full Stokes Parameters in Polarized Radiative Transfer of Electron Cyclotron Waves on LHD, The 12th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating, 95.0-100.0, (ISBN-981-238-189-9), 2003.01.
405. Ozaki, Tetsuo; Murakami, Sadayoshi; Goncharov, Pavel; Watanabe, Tsuguhiro; Sudo, Shigeru; Narihara, Kazumichi; Tanaka, Kenji; Kubo, Shin; Simozuma, Takashi; Idei, Hiroshi; , Spatial resolved high-energy particle diagnostic system using time-of-flight neutral particle analyzer in Large Helical Device, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol. 74, No. 3, Pages 1878-1882, 2003.01.
406. Y. Nagayama, K. Kawahata, S. Inagaki, B. J. Peterson, S. Sakakibara, K. Tanaka, T. Tokuzawa, K. Y. Watanabe, N. Ashikawa, H. Chikaraishi, M. Emoto, H. Funaba, M. Goto, Y. Hamada, K. Ichiguchi, K. Ida, H. Idei, T. Ido, K. Ikeda, S. Imagawa, A. Isayama, M. Isobe, A. Iwamoto, O. Kaneko, S. Kitagawa, A. Komori, S. Kubo, R. Kumazawa, S. Masuzaki, K. Matsuoka, T. Mito, J. Miyazawa, T. Morisaki, S. Morita, O. Motojima, S. Murakami, T. Mutoh, S. Muto, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, A. Nishimura, K. Nishimura, A. Nishizawa, N. Noda, S. Ohdachi, K. Ohkubo, N. Ohyabu, Y. Oka, M. Osakabe, T. Ozaki, A. Sagara, K. Saito, R. Sakamoto, M. Sasao, K. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, S. Sudo, K. Takahata, Y. Takeiri, K. Toi, K. Tsumori, H. Yamada, I. Yamada, K. Yamazaki, N. Yanagi, M. Yokoyama, Y. Yoshimura, Y. Yoshinuma, T. Watari, Sawtooth Oscillation in Current-Carrying Plasma in the Large Helical Device, Physical Review Letters, 10.1103/PhysRevLett.90.205001, 90, 20, 2003.01, [URL], Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the [Formula presented] threshold of the sawtooth oscillation. When the central [Formula presented] value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed..
407. S Morita, M Goto, S Kubo, S Murakami, K Narihara, M Osakabe, T Seki, Y Takeiri, K Tanaka, H Yamada, H Funaba, H Idei, K Ida, K Ikeda, S Inagaki, O Kaneko, K Kawahata, A Komori, R Kumazawa, S Masuzaki, J Miyazawa, T Morisaki, O Motojima, S Muto, T Mutoh, Y Nagayama, Y Nakamura, K Nishimura, S Ohdachi, N Ohyabu, Y Oka, T Ozaki, BJ Peterson, S Sakakibara, R Sakamoto, M Sasao, K Sato, T Shimozuma, M Shoji, H Suzuki, K Toi, T Tokuzawa, K Tsumori, KY Watanabe, T Watari, I Yamada, Behaviour of ion temperature in electron and ion heating regimes observed with ECH, NBI and ICRF discharges of LHD, NUCLEAR FUSION, 42.0, 10.0, 1179.0, 2002.10, Ion temperature at the plasma centre has been measured from Doppler broadening of Ti XXI (2.61 Å) and Ar XVII (3.95 Å) x-ray lines using a newly installed crystal spectrometer with CCD detector in ECH, NBI and ICRF plasmas of Large Helical Device (LHD). The ion temperature obtained in a range of 0.6 and 3.5 keV was analysed with electron density and compared with electron temperature. A new parameter range of Ti>Te was found in low-density (ne<1013 cm−3) H-minority ICRF discharges operated in the ion-heating regime (Pi≥Pe), whereas the ion temperature was roughly equal to the electron temperature in NBI discharges operated in the electron-heating regime (Pi
408. O. Motojima, N. Ohyabu, A. Komori, O. Kaneko, H. Yamada, K. Kawahata, Y. Nakamura, K. Ida, T. Akiyama, N. Ashikawa, W. A. Cooper, A. Ejiri, M. Emoto, N. Ezumi, H. Funaba, A. Fukuyama, P. Goncharov, M. Goto, H. Idei, K. Ikeda, S. Inagaki, M. Isobe, S. Kado, H. Kawazome, K. Khlopenkov, T. Kobuchi, K. Kondo, A. Kostrioukov, S. Kubo, R. Kumazawa, Y. Liang, J. F. Lyon, A. Mase, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, K. Nagaoka, Y. Nagayama, N. Nakajima, K. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, K. Nishimura, N. Nishino, N. Noda, T. Notake, H. Nozato, S. Ohdachi, Y. Oka, H. Okada, S. Okamura, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, M. Sakamoto, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Takeuchi, N. Tamura, K. Tanaka, M. Y. Tanaka, Y. Teramachi, K. Toi, T. Tokuzawa, Y. Tomota, Y. Torii, K. Tsumori, K. Y. Watanabe, T. Watari, Y. Xu, I. Yamada, S. Yamamoto, T. Yamamoto, M. Yokoyama, S. Yoshimura, Y. Yoshimura, M. Yoshinuma, N. Asakura, T. Fujita, T. Fukuda, T. Hatae, S. Higashijima, A. Isayama, Y. Kamada, H. Kubo, Y. Kusama, Y. Miura, T. Nakano, H. Ninomiya, T. Oikawa, N. Oyama, Y. Sakamoto, K. Shinohara, T. Suzuki, H. Takenaga, K. Ushigusa, T. Hino, M. Ichimura, Y. Takase, F. Sano, H. Zushi, T. Satow, S. Imagawa, T. Mito, I. Ohtake, T. Uda, K. Itoh, K. Ohkubo, S. Sudo, K. Yamazaki, K. Matsuoka, Y. Hamada and M. Fujiwara, Recent Advance in LHD Experiment, Proc. 19th IAEA Fusion Energy Conference, 43.0, 43,12(※IAEA-CN-94/OV/1-6), 2002.10.
409. S. Morita, M. Goto, S. Kubo, S. Murakami, K. Narihara, M. Osakabe, T. Seki, Y. Takeiri, K. Tanaka, H. Yamada, H. Funaba, Hiroshi Idei, K. Ida, K. Ikeda, Inagaki Shigeru, O. Kaneko, K. Kawahata, A. Komori, R. Kumazawa, S. Masuzaki, J. Miyazawa, T. Morisaki, O. Motojima, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, K. Nishimura, S. Ohdachi, N. Ohyabu, Y. Oka, T. Ozaki, B. J. Peterson, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, T. Shimozuma, M. Shoji, H. Suzuki, K. Toi, T. Tokuzawa, K. Tsumori, K. Y. Watanabe, T. Watari, I. Yamada, Behaviour of ion temperature in electron and ion heating regimes observed with ECH, NBI and ICRF discharges of LHD, Nuclear Fusion, 10.1088/0029-5515/42/10/301, 42, 10, 1179-1183, 2002.10, [URL], Ion temperature at the plasma centre has been measured from Doppler broadening of Ti XXI (2.61 Å) and Ar XVII (3.95 Å) x-ray lines using a newly installed crystal spectrometer with CCD detector in ECH, NBI and ICRF plasmas of Large Helical Device (LHD). The ion temperature obtained in a range of 0.6 and 3.5 kev was analysed with electron density and compared with electron temperature. A new parameter range of Ti > Te was found in low-density (ne < 1013 cm-3) H-minority ICRF discharges operated in the ion-heating regime (Pi ≥ Pe), whereas the ion temperature was roughly equal to the electron temperature in NBI discharges operated in the electron-heating regime (Pi < Pe). The ion temperature in the ICRF and ICRF + NBI discharges was correlated with the input power to bulk ions over the ion density (Pi/ni). As a result, a good correlation was obtained between them and it also indicated a clear rise of the ion temperature for the increasing Pi in a range of Pi/ni < 5 (MW/1013 cm-3)..
410. K. Ohkubo, S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, T. Notake, W. Kasparek, THEORETICAL ANALYSIS OF REMOTE STEERING ANTENNA AND COMPARISON WITH EXPERIMENT, Fifth International Workshop STRONG MICROWAVES IN PLASMAS, p.1-9, 2002.09.
411. Idei, H; Shimozuma, T; Notake, T; Ito, S; Kubo, S; Shapiro, MA; Anderson, JP; Temkin, RJ; Ohkubo, K; , Beam alignment of ECH transmission line using moment method, Infrared and Millimeter Waves, 2002. Conference Digest. Twenty Seventh International Conference on, 151.0-152.0, 2002.09, In the 84 GHz CPI gyrotron, with a single-stage depressed collector in the TE/sub 15,3/ oscillating mode, a geometric optics Vlasov converter was installed in the tube to convert the mode into a Gaussian beam. The low power test stand where intensity and phase patterns can be measured was prepared at the National Institute for Fusion Science (NIFS). The sizes and tilt angles of quasi-optical beams are deduced from the measured intensity and phase profiles using the moment method. The Gaussian-like beam is coupled into the HE/sub 11/ corrugated waveguide with tilt angle adjustment. The beam radiated from the waveguide after coupling is analyzed with the moment method. The Gaussian content in the radiated beam is also discussed..
412. K Saito, R Kumazawa, T Mutoh, T Seki, T Watari, T Yamamoto, Y Torii, N Takeuchi, C Zhang, Y Zhao, A Fukuyama, F Shimpo, G Nomura, M Yokota, A Kato, M Sasao, M Isobe, A V Krasilnikov, T Ozaki, M Osakabe, K Narihara, Y Nagayama, S Inagaki, K Itoh, T Ido, S Morita, K Ohkubo, M Sato, S Kubo, T Shimozuma, H Idei, Y Yoshimura, T Notake, O Kaneko, Y Takeiri, Y Oka, K Tsumori, K Ikeda, A Komori, H Yamada, H Funaba, K Y Watanabe, S Sakakibara, R Sakamoto, J Miyazawa, K Tanaka, B J Peterson, N Ashikawa, S Murakami, T Minami, M Shoji, S Ohdachi, S Yamamoto, H Suzuki, K Kawahata, M Emoto, H Nakanishi, N Inoue, N Ohyabu, Y Nakamura, S Masuzaki, S Muto, K Sato, T Morisaki, M Yokoyama, T Watanabe, M Goto, I Yamada, K Ida, T Tokuzawa, N Noda, K Toi, S Yamaguchi, K Akaishi, A Sagara, K Nishimura, K Yamazaki, S Sudo, Y Hamada, O Motojima and M Fujiwara, A study of high-energy ions produced by ICRF heating in LHD, PLASMA PHYSICS AND CONTROLLED FUSION, 44.0, 1.0, 103.0, 2002.08, This paper reports on the behaviour of high-energy ions created by ion cyclotron range of frequency (ICRF) heating on the Large Helical Device (LHD). In the third experimental campaign conducted in 1999, it was found that minority heating has good heating performance, and high-energy particles were observed. In the fourth campaign in 2000, the temporal behaviour of high-energy ions was investigated in the minority heating regime using turnoff or modulation of ICRF power. The time evolution of the high-energy particle distribution was measured using a natural diamond detector (NDD) and a time-of-flight neutral particle analyser (TOF-NPA). It was found that the count number of higher-energy particles declines faster than that of lower-energy particles after ICRF turnoff. In the modulation experiments, the phase difference of the flux of high-energy particles with respect to the ICRF power modulation increased with energy. These results were explained qualitatively by the Fokker-Planck equation with a simple model. The pitch-angle dependence of the distribution function was also measured in the experiment by changing the line of sight of the TOF-NPA, and an anisotropy of the high-energy tail was found. This anisotropy was reproduced by solving the bounce-averaged Fokker-Planck equation. The second harmonic heating was conducted successfully for the first time in the LHD in high-β plasma, and high-energy particles were also detected in this heating regime..
413. T. Yamamoto, T. Watari, T. Mutoh, R. Kumazawa, T. Seki, K. Saito, Y. Torii, N. Takeuti, H. Sasao, M. Isobe, A. Krasilnikov, T. Morisaki, H. Yamada, Y. P. Zhao, Z. Chen, Hiroshi Idei, S. Kubo, K. Ohkubo, M. Sato, T. Shimozuma, Y. Yoshimura, T. Notake, K. Ikeda, O. Kaneko, Y. Oka, M. Osakabe, Y. Takeiri, K. Tsumori, H. Funaba, M. Goto, K. Ida, Inagaki Shigeru, K. Itoh, K. Kawahata, A. Komori, Y. Liang, S. Masuzaki, J. Miyazawa, S. Morita, S. Murakami, S. Muto, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, S. Ohdachi, N. Ohyabu, T. Ozaki, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, K. Sato, M. Shoji, S. Sudo, H. Suzuki, K. Tanaka, K. Toi, T. Tokuzawa, K. Y. Watanabe, T. Watanabe, K. Yamazaki, M. Yokoyama, O. Motojima, Optimization of ICRF heating in terms of confining magnetic field parameters in the LHD, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/44/8/308, 44, 8, 1543-1556, 2002.08, [URL], The utility of ICRF heating in the LHD was demonstrated in the third campaign carried out in 1999. This paper summarizes the investigations made in 2000 with a focus on the optimization of ICRF heating. The flexibility of the LHD magnetic configuration was fully utilized as a key factor in the investigations. The experiments include (a) scan of magnetic field intensity, (b) scan of aspect ratio, (c) scan of magnetic axis shift, (d) scan of quadrupole magnetic field, and (e) cancellation of magnetic island. The performance of the ICRF heating was thus optimized with respect to magnetic parameters, while optimization was achieved mainly with respect to heating regime and wall conditioning in the third campaign. Some of these parameters are directly related to the orbit of trapped particles. Therefore, the relation between particle orbits and the performance of ICRF heating is also addressed in this paper based on analyses of the high-energy tail of ions..
414. S Morita, Y Shirai, M Goto, Y Nakamura, H Idei, M Isobe, S Kubo, K Matsuoka, T Minami, S Nishimura, S Okamura, M Osakabe, S Takagi, C Takahashi, K Tanaka, K Toi, Y Yoshimura, Observation of ablation and acceleration of impurity pellets in the presence of energetic ions in the CHS heliotron/torsatron, NUCLEAR FUSION, Vol. 42, No. 7, Pages 876, 2002.07.
415. S. Morita, Y. Shirai, M. Goto, Y. Nakamura, Hiroshi Idei, M. Isobe, S. Kubo, K. Matsuoka, T. Minami, S. Nishimura, S. Okamura, M. Osakabe, S. Takagi, C. Takahashi, K. Tanaka, K. Toi, Y. Yoshimura, Observation of ablation and acceleration of impurity pellets in the presence of energetic ions in the CHS heliotron/torsatron, Nuclear Fusion, 10.1088/0029-5515/42/7/310, 42, 7, 876-880, 2002.07, [URL], Hydrocarbon pellets were injected into NBI and ECH plasmas of the Compact Helical System (CHS) heliotron/torsatron. The ablation of the pellet was observed from horizontal and vertical directions using two CCD cameras, and the velocities of the pellet during ablation were measured with an 11 channel fan array. It was observed that the pellet trajectory was strongly curved in NBI cases, whereas in ECH cases it was straight. When the toroidal direction of the tangential NBI was changed from clockwise to counter-clockwise, the direction of the curved trajectory completely changed. For the first time, it was also found that the pellet was accelerated during the ablation, for example from 270 to 600 m/s. The ablation of the pellet is simulated for the case with fast ions from NBI (40 keV). The results strongly support the idea that the pellet can be mainly ablated by collisions with fast ions. As a result, it is found that the pellet is accelerated by a jet of the ablation cloud resulting from one-side heating due to the toroidally circulating fast ions..
416. H. Funaba, T. Shimozuma, S. Kubo, H. Idei, Y. Yoshimura, T. Notake, K. Narihara, K. Ida, Y. Nagayama, S. Inagaki, Y. Takeiri, M. Osakabe, K. Tanaka, B. J.Peterson, K. Y.Watanabe, S. Murakami, M. Yokoyama, K. Kawahata, N. Ohyabu and the LHD Experimental Group, Transport Analysis of ECH Overlapped NBI Plasmas in LHD, 29th EPS Conference on Plasma Phys. and Contr. Fusion Montreux, ECA Vol. 26B, P-1.077 (2002), 2002.06.
417. Y. Torii, R. Kumazawa, T. Seki, T. Mutoh, T. Watari, K. Saito, T. Yamamoto, N. Takeuchi, Zhang Cheng, Yangping Zhao, F. Shimpo, G. Nomura, M. Yokota, A. Kato, K. Nishimura, T. S. Bigelow, D. A. Rasmussen, R. H. Goulding, M. D. Carter, H. Idei, K. Ikeda, O. Kaneko, K. Kawahata, A. Komori, S. Kubo, J. Miyazawa, T. Morisaki, Y. Nakamura, T. Notake, K. Ohkubo, N. Ohyabu, Y. Oka, M. Osakabe, M. Sato, T. Shimozuma, Y. Takeiri, K. Tsumori, T. Watanabe, H. Yamada, Y. Yoshimura, Plasma production experiments using a folded waveguide antenna on LHD, Nuclear Fusion, 10.1088/0029-5515/42/6/306, 42, 6, 679-688, 2002.06, [URL], A folded waveguide (FWG) antenna was used in the ion cyclotron range of frequency (ICRF) on the large helical device (LHD) in the National Institute for Fusion Science. The FWG antenna is a waveguide antenna folded several times in order to make its size smaller. The FWG antenna in the LHD is designed so that slow waves are excited preferentially. It was used in the fourth experimental campaign in 2000-2001 for the purpose of plasma production and plasmas with an average electron density up to 3.0 × 1018 m-3 were obtained. This will be a high enough density for initial plasmas of neutral beam injection or ICRF to obtain plasmas with higher densities and temperatures. This is the first demonstration of the utility of an FWG antenna in magnetic confinement devices. Further investigations were made in order to understand the mechanism of plasma production. The maximum achievable plasma density increased with injection power and gas-puffing rate, and became saturated. The density became higher as the magnetic field strength was increased. Such experimental observations were explained by the wave accessibility conditions of a shear Alfvén wave..
418. O Kaneko, A Komori, H Yamada, N Ohyabu, K Kawahata, Y Nakamura, K Ida, S Murakami, T Mutoh, S Sakakibara, S Masuzaki, N Ashikawa, M Emoto, H Funaba, M Goto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, K Khlopenkov, S Kubo, R Kumazawa, T Minami, J Miyazawa, T Morisaki, S Morita, S Muto, Y Nagayama, N Nakajima, H Nakanishi, K Narihara, K Nishimura, N Noda, T Notake, T Kobuchi, Y Liang, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, K Saito, R Sakamoto, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, M Takechi, Y Takeiri, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, KY Watanabe, T Watari, Y Xu, K Itoh, K Matsuoka, K Ohkubo, I Ohtake, T Satow, S Sudo, K Yamazaki, Y Hamada, O Motojima, M Fujiwara, Compatibility between high energy particle confinement and magnetohydrodynamic stability in the inward-shifted plasmas of the Large Helical Device, PHYSICS OF PLASMAS, 9.0, 5.0, 2020.0-2026.0, 2002.05.
419. Yuhong Xu, BJ Peterson, S Sudo, T Tokuzawa, K Narihara, M Osakabe, S Morita, M Goto, S Sakakibara, K Tanaka, K Kawahata, K Tsumori, K Ikeda, S Kubo, H Idei, J Miyazawa, KY Watanabe, K Nishimura, A Kostrioukov, H Yamada, O Kaneko, N Ohyabu, K Komori, Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD, NUCLEAR FUSION, Vol. 42, No. 5, Pages 601, 2002.05.
420. O. Kaneko, A. Komori, H. Yamada, N. Ohyabu, K. Kawahata, Y. Nakamura, K. Ida, S. Murakami, T. Mutoh, S. Sakakibara, S. Masuzaki, N. Ashikawa, M. Emoto, H. Funaba, M. Goto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, K. Khlopenkov, S. Kubo, R. Kumazawa, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Muto, Y. Nagayama, N. Nakajima, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, T. Kobuchi, Y. Liang, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, K. Saito, R. Sakamoto, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamamoto, M. Yokoyama, Y. Yoshimura, M. Yoshinuma, K. Y. Watanabe, T. Watari, Y. Xu, K. Itoh, K. Matsuoka, K. Ohkubo, I. Ohtake, T. Satow, S. Sudo, K. Yamazaki, Y. Hamada, O. Motojima, M. Fujiwara, Compatibility between high energy particle confinement and magnetohydrodynamic stability in the inward-shifted plasmas of the Large Helical Device, Physics of Plasmas, 10.1063/1.1448345, 9, 5, 2020-2026, 2002.05, [URL], The experimentally optimized magnetic field configuration of the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)], where the magnetic axis is shifted inward by 15 cm from the early theoretical prediction, reveals 50% better global energy confinement than the prediction of the scaling law. This configuration has been investigated further from the viewpoints of high energy particle confinement and magnetohydrodynamic (MHD) stability. The confinement of high energy ions is improved as expected. The minority heating of ion cyclotron range of frequency was successful and the heating efficiency was improved by the inward shift. The confinement of passing particles by neutral beam injection was also improved under low magnetic field strength, and there could be obtained an almost steady high beta discharge up to 3% in volume average. This was a surprising result because the observed pressure gradient exceeded the Mercier unstable limit. The observed MHD activities became as high as beta but they did not grow enough to deteriorate the confinement of high energy ions or the performance of the bulk plasma, which was still 50% better than the scaling. According to these favorable results, better performance would be expected by increasing the heating power because the neoclassical transport can also be improved there..
421. Yuhong Xu, B. J. Peterson, S. Sudo, T. Tokuzawa, K. Narihara, M. Osakabe, S. Morita, M. Goto, S. Sakakibara, K. Tanaka, K. Kawahata, K. Tsumori, K. Ikeda, S. Kubo, Hiroshi Idei, J. Miyazawa, K. Y. Watanabe, K. Nishimura, A. Kostrioukov, H. Yamada, O. Kaneko, N. Ohyabu, K. Komori, Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD, Nuclear Fusion, 10.1088/0029-5515/42/5/312, 42, 5, 601-613, 2002.05, [URL], In LHD discharges, the NBI heated plasmas are terminated in two ways: (a) thermal decay (TD) after the termination of NBI and (b) radiative collapse (RC) during the NBI heating. The basic characteristics of the TD and RC discharges are compared. It is found that the decay and collapse of the plasma are mainly governed by the heating power and the plasma density. The critical density n̄c for the collapse of RC plasmas is similar to the scaling laws obtained in other helical devices, i.e. n̄c ∝ (PB/V)0.5, where P, B and V denote heating power, magnetic field and plasma volume, respectively. Moreover, measurements using multichannel bolometric diagnostics indicate that the total radiation profiles in TD and RC plasmas are usually inboard-outboard symmetric and asymmetric, respectively, at the end of the discharge. In RC discharges, the total radiation profile develops in several phases. Before the onset of the thermal instability (TI), the radiation profile is rather symmetric, while after that, the radiation profile evolves from being symmetric in the initial period towards being asymmetric eventually with high radiation on the inboard side. Corresponding variations are shown in the time evolutions of the density and temperature profiles, and a substantial contraction of the plasma column is observed immediately after TI onset. The spatial and temporal coincidence of the asymmetries in the radiation, density and temperature is similar to that observed with multifaceted asymmetric radiation from the edge (MARFE) in tokamaks. But, unlike MARFEs, the asymmetric radiation (AR) in LHD is rather transient since it appears just before the end of RC discharges. The underlying cause for the development of radiation asymmetry was investigated and compared with existing instability models. The result suggests that the high inboard radiation is a manifestation of an enhanced local thermal instability, and the AR results from asymmetric developments of TI on the inboard-outboard sides during the final stage of RC discharges..
422. Shin KUBO, Takashi SHIMOZUMA, Hiroshi IDEI, Yasuo YOSHIMURA, Takashi NOTAKE, Motoyasu SATO, Kunizo OHKUBO, Kazuo KAWAHATA, Nobuyoshi OHYABU, Osamu KANEKO, Akio KOMORI, Hiroshi YAMADA, Naoko ASHIKAWA, Masahiko EMOTO, Hisamichi FUNABA, Motoshi GOTO, Katsumi IDA, Katsunori IKEDA, Shigeru INAGAKI, Mitsutaka ISOBE, Konstantin KHLOPENKOV, Takashi KOBUCHI, Ryuhei KUMAZAWA, Yunfeng LIANG, Suguru MASUZAKI, Takashi MINAMI, Jyun-ichi MIYAZAWA, Tomohiro MORISAKI, Shigeru MORITA, Sadayoshi MURAKAMI, Sadatsugu MUTO, Takashi MUTOH, Yoshio NAGAYAMA, Yukio NAKAMURA, Hideya NAKANISHI, Kazumichi NARIHARA, Yoshiro NARUSHIMA, Kiyohiko NISHIMURA, Nobuaki NODA, Satoshi OHDACHI, Yoshihide OKA, Masaki OSAKABE, Tetsu OZAKI, Byron J. PETERSON, Akio SAGARA, Kenji SAITO, Satoru SAKAKIBARA, Ryuichi SAKAMOTO, Mamiko SASAO, Tetsuo SEKI, Mamoru SHOJI, Shigeru SUDO, Hajime SUZUKI, Yasuhiko TAKEIRI, Norio TAKEUCHI, Naoki TAMURA, Kenji TANAKA, Kazuo TOI, Tokihiko TOKUZAWA, Yuki TORII, Katsuyoshi TSUMORI, Kiyomasa WATANABE, Tsuguhiro WATANABE, Tetsuo WATARI, Ichihiro YAMADA, Satoshi YAMAMOTO, Taro YAMAMOTO, Kozo YAMAZAKI, Masayuki YOKOYAMA, Mikiro YOSHINUMA, Osamu MOTOJIMA, Achievement of 10 keV Central Electron Temperatures by ECH in LHD, Journal of Plasma and Fusion Research, 78.0, 2.0, 99.0-100.0, 2002.02.
423. N. Ohyabu, K. Ida, T. Morisaki, K. Narihara, A. Komori, K. Watanabe, Y. Narushima, Y. Nagayama, M. Shoji, N. Ashikawa, M. Emoto, H. Funaba, M. Goto, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, K. Khlopenkov, T. Kobuchi, A. Kostrioukov, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, S. Morita, S. Muto, T. Mutoh, S. Murakami, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Notake, K. Ohkubo, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, R. Sakamoto, S. Sakakibara, A. Sagara, K. Saito, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, S. Sudo, H. Suzuki, Y. Takeiri, K. Tanaka, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Watanabe, K. Yamazaki, I. Yamada, S. Yamamoto, M. Yokoyama, Y. Yoshimura, T. Watari, Y. Xu, O. Kaneko, K. Kawahata, H. Yamada, O. Motojima, Island dynamics in the large-helical-device plasmas, Physical Review Letters, 88, 5, 550051-550054, 2002.02, A report on the dynamics of the islands with various sizes in the wider range of the background configurations and the parameter growth or suppression of the island in the large-helical-device (LHD) plasma discharges was presented. It was found that the size of an externally imposed island with mode number was decreased for collisionless finite beta LHD plasmas. The size of the island observed to increase for the collisional plasmas with finite beta..
424. Morita, S.; Goto, M.; Kubo, S.; Murakami, S.; Narihara, K.; Osakabe, M.; Seki, T.; Takeiri, Y.; Tanaka, K.; Yamada, H.; Funaba, H.; Idei, H.; Ida, K.; Ikeda, K; Inagaki, S.; Kaneko, O.; Kawahata, K.; Komori, A; Kumazawa, R.; Masuzaki, S.; Miyazawa, J.; Morisaki, T.; Motojima, O.; Muto, S.; Mutoh, T.; Nagayama, Y; Nakamura, Y.; Nishimura, K.; Ohdachi, S.; Ohyabu, N.; Oka, Y.; Ozaki, T.; Peterson, B. J.; Sakakibara, S.; Sakamoto, R.; Sasao, M.; Sato, K.; Shimozuma, T.; Shoji, M.; Suzuki, H.; Toi, K.; Tokuzawa, T.; Tsumori, K.; Watanabe, K. Y.; Watari, T.; Yamada I , Behavior of central ion temperature and toroidal rotation in ECH, NBI and ICRF discharges of LHD, Proc. of 13th International Stellarator Workshop, 4.0, Article No. OIV:2, 2002.01, Ion temperatures at the plasma center have been measured from Doppler broadening of TiXXI x-ray line (2.61Angstroms) using a crystal spectrometer in ECH, NBI and ICRF plasmas of the Large Helical Device (LHD). The ion temperature obtained in a range of 0.6 and 3.5keV was analyzed with electron densities and compared with electron temperature. As a result, we could see that a condition of Ti >Te was clearly achieved in low-density (ne <1013 cm-3 ) two- ion hybrid ICRF discharges (H: minority, He: majority) operated in ion- heating regime (Pion >Pe ), whereas the ion temperature was roughly equal to the electron temperature in NBI discharges operated in electron- heating regime (Pion < Pe ). The ion temperature in ECH discharges becomes equal to the electron temperature at electron densities near 1x1013 cm-3 , although the electron temperature is much higher than the ion temperature at ne <1x1013 cm-3 . This can be explained by the relation between energy confinement time, τE , and electron- ion energy exchange time, τei . The ion temperature in the ion-heating regime was correlated with heating power over electron density (P/< ne >). Most of the ion temperatures ranged between 1.5*(P/ne )0.5 and 2.2*(P/ne )0.5. Considering the ISS-95 scaling, we can obtain a relation of 1.44*P 0.4can obtain a relation of 1.44*P 0.41 /ne 0.49 under the assumption of Te =Ti with parabolic profiles. However, the ion temperature is distributed in a range between 1.44*P 0.41 /ne 0.49 and 2.3*P 0.41 /ne 0.49 . This result suggests an improvement of 50% for ion heating efficiency in ICRF discharges compared with NBI heating discharges. The ion temperature in NBI+ICRF discharges also showed a continuous increment for the P/< ne >, although it saturated in the electron- heating regime of NBI discharges. These results demonstrated the achievement of successful ion heating in the ICRF and ICRF+NBI discharges and pointed out the importance of direct ion heating to increase the ion heating efficiency (ICRF: PH /(Pe +PH )∼0.9, NBI: Pion /(Pe +Pion )∼0.2), and also suggested a new direction for helical experimental research. Toroidal rotation has been also measured from the Doppler shift of TiXXI spectra. In ECH plasmas no toroidal rotation is observed. In NBI cases it is roughly 4km/s for Pabs =1.0MW and 7km/s for 1.6MW at ne =1x1013 cm-3 . Further analysis is being carried out..
425. H. Idei, T. Notake, M. Shapiro, W. Kasparek, T. Shimozuma, S. Kubo, S. Ito, M. Sato, R. J.Temkin and K. Ohkubo, Development of Quasi-Optical Components for Electron Cyclotron Heating based on Phase Measurements, The 12th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating, 1.0, 517.0-522.0, (ISBN-981-238-189-9), 2002.01.
426. Nina N Skvortsova, German M Batanov, Leonid V Kolik, VV Saenko, AE Petrov, AA Pshenichnikov, KA Sarksyan, NK Kharchev, K Ohkubo, T Shimozuma, H Idei, Ya Yoshimura, S Kubo, J Sanchez, T Estrada, D Van Milliqen, Investigation of Turbulence in High-Temperature Plasma by Microwave Scattering Techniques in Modern Stellarators, JOURNAL OF NUCLEAR MATERIALS, 5.0, 328.0-332.0, 2002.01.
427. N Ohyabu, K Ida, T Morisaki, K Narihara, A Komori, K Watanabe, Y Narushima, Y Nagayama, M Shoji, N Ashikawa, M Emoto, H Funaba, M Goto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, K Khlopenkov, T Kobuchi, A Kostrioukov, S Kubo, R Kumazawa, Y Liang, S Masuzaki, T Minami, J Miyazawa, S Morita, S Muto, T Mutoh, S Murakami, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Notake, K Ohkubo, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, R Sakamoto, S Sakakibara, A Sagara, K Saito, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, S Sudo, H Suzuki, Y Takeiri, K Tanaka, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, T Watanabe, K Yamazaki, I Yamada, S Yamamoto, M Yokoyama, Y Yoshimura, T Watari, Y Xu, O Kaneko, K Kawahata, H Yamada, O Motojima, Island dynamics in the large-helical-device plasmas, Physical review letters, 88.0, 5.0, Article No. 055005, 2002.01.
428. T. Ozaki, P. Goncharov, S. Murakami, S. Sudo, M. Shoji, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, K. Ikeda, O. Kanko, K. Kawahata, T. Kobuchi, S. Kubo, R. Kumazawa, S. Morita, O. Motojima, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, N. Noda, S. Ohdachi, N. Ohyabu, Y. Oka, M. Osakabe, B. Peterson, K. Saito, S. Sakakibara, M. Sasao, K. Sato, T. Seki, T. Shimozuma, Y. Takeiri, K. Tanaka, H. Torii, K. Tsumori, T. Watanabe, T. Watari, V. Zanza, G. Bracco, A. Sibio, B. Tilia, G1/G2 Group, Spatial Distribution Measurement of High Energy Particle using Time-Of-Flight Neutral Particle Energy Analyzer in Large Helical Device, Advanced Diagnostics for Magnetic and Inertial Fusion, 145.0-148.0, 2002.01.
429. S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, T. Notake', M. Sato, K. Ohkubo, T. Watari, K. Naribara, . Yamada, S. Inagaki, Y. Nagayama, S. Murakami, S. MutoY. Takeiri, M. Yokoyama, N. Ohyabu, K. Ida, K. Kawahata, . Kaneko, A. Komori, T. Mutoh, Y. Nakamura, H. Yamada, T. Akiyama , N. Ashikawa, M. Emoto, H. Funaba, P. GoncharoV, M. Goto, K. Ikeda, M. Isobe, H. Kawazome , K. Khlopenkov, T. Kobuchi, A. Kostrioukov, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, H. Nakanishi, Y. Narushima, K. Nishimura, N. Noda, H. Nozatol, S. Ohdachi, Y Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, T. Saida, K. Saito, S. Sakakibara, R. Sakamoto, M. Sasao, K. SatoT. Seki, M. Shoji, H. Suzuki, N. Takeuchi', N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torfil, K. Tsumori, K. Y. Watanabe, Y. Xu, S. Yamamoto', T. Yamamoto', M. Yoshinuma, K. Itoh, T. Satow, S. Sudo, T. Uda, K. Yamazaki, K. Matsuoka, . Motojima, Y. Hamada, and M. Fujiwara, Transport barrier formation by application of localized ECH in the LHD, National Inst. for Fusion Science, Toki, Gifu (Japan), NIFS--759; IAEA-CN--94/EX/C4-5RB;, 2002.01.
430. K. Saito, R. Kumazawa, T. Mutoh, T. Seki, T. Watari, T. Yamamoto, Y. Torii, N. Takeuchi, C. Zhang, Y. Zhao, A. Fukuyama, F. Shimpo, G. Nomura, M. Yokota, A. Kato, M. Sasao, M. Isobe, A. V. Krasilnikov, T. Ozaki, M. Osakabe, K. Narihara, Y. Nagayama, Inagaki Shigeru, K. Itoh, T. Ido, S. Morita, K. Ohkubo, M. Sato, S. Kubo, T. Shimozuma, Hiroshi Idei, Y. Yoshimura, T. Notake, O. Kaneko, Y. Takeiri, Y. Oka, K. Tsumori, K. Ikeda, A. Komori, H. Yamada, H. Funaba, K. Y. Watanabe, S. Sakakibara, R. Sakamoto, J. Miyazawa, K. Tanaka, B. J. Peterson, N. Ashikawa, S. Murakami, T. Minami, M. Shoji, S. Ohdachi, S. Yamamoto, H. Suzuki, K. Kawahata, M. Emoto, H. Nakanishi, N. Inoue, N. Ohyabu, Y. Nakamura, S. Masuzaki, S. Muto, K. Sato, T. Morisaki, M. Yokoyama, T. Watanabe, M. Goto, I. Yamada, K. Ida, T. Tokuzawa, N. Noda, K. Toi, S. Yamaguchi, K. Akaishi, A. Sagara, K. Nishimura, K. Yamazaki, S. Sudo, Y. Hamada, O. Motojima, M. Fujiwara, A study of high-energy ions produced by ICRF heating in LHD, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/44/1/309, 44, 1, 103-119, 2002.01, [URL], This paper reports on the behaviour of high-energy ions created by ion cyclotron range of frequency (ICRF) heating on the Large Helical Device (LHD). In the third experimental campaign conducted in 1999, it was found that minority heating has good heating performance, and high-energy particles were observed. In the fourth campaign in 2000, the temporal behaviour of high-energy ions was investigated in the minority heating regime using turnoff or modulation of ICRF power. The time evolution of the high-energy particle distribution was measured using a natural diamond detector (NDD) and a time-of-flight neutral particle analyser (TOF-NPA). It was found that the count number of higher-energy particles declines faster than that of lower-energy particles after ICRF turnoff. In the modulation experiments, the phase difference of the flux of high-energy particles with respect to the ICRF power modulation increased with energy. These results were explained qualitatively by the Fokker-Planck equation with a simple model. The pitch-angle dependence of the distribution function was also measured in the experiment by changing the line of sight of the TOF-NPA, and an anisotropy of the high-energy tail was found. This anisotropy was reproduced by solving the bounce-averaged Fokker-Planck equation. The second harmonic heating was conducted successfully for the first time in the LHD in high-β plasma, and high-energy particles were also detected in this heating regime..
431. H. Idei, T. Shimozuma, T. Notake, S. Ito, S. Kubo, M. A. Shapiro, J. P. Anderson, R. J. Temkin, K. Ohkubo, Beam alignment of ECH transmission line using moment method, 27th International Conference on Infrared and Millimeter Waves, IRMMW 2002
Conference Digest - 27th International Conference on Infrared and Millimeter Waves, IRMMW 2002
, 10.1109/ICIMW.2002.1076129, 151-152, 2002.01, [URL], In the 84 GHz CPI gyrotron, with a single-stage depressed collector in the TE15,3 oscillating mode, a geometric optics Vlasov converter was installed in the tube to convert the mode into a Gaussian beam. The low power test stand where intensity and phase patterns can be measured was prepared at the National Institute for Fusion Science (NIFS). The sizes and tilt angles of quasi-optical beams are deduced from the measured intensity and phase profiles using the moment method. The Gaussian-like beam is coupled into the HE11 corrugated waveguide with tilt angle adjustment. The beam radiated from the waveguide after coupling is analyzed with the moment method. The Gaussian content in the radiated beam is also discussed..
432. N. Ohyabu, K. Ida, T. Morisaki, K. Narihara, A. Komori, K. Watanabe, Y. Narushima, Y. Nagayama, M. Shoji, M. Emoto, H. Funaba, M. Goto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, K. Khlopenkov, A. Kostrioukov, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, S. Morita, S. Muto, T. Mutoh, S. Murakami, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, K. Ohkubo, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, R. Sakamoto, S. Sakakibara, A. Sagara, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, S. Sudo, H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, T. Watanabe, K. Yamazaki, I. Yamada, M. Yokoyama, Y. Yoshimura, T. Watari, Y. Xu, O. Kaneko, K. Kawahata, H. Yamada, O. Motojima, N. Ashikawa, T. Kobuchi, Y. Liang, N. Tamura, T. Notake, K. Saito, Y. Torii, S. Yamamoto, Island Dynamics in the Large-Helical-Device Plasmas, Physical Review Letters, 10.1103/PhysRevLett.88.055005, 88, 5, 2002.01, [URL], In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ([Formula presented]) decreases substantially when the plasma is collisionless ([Formula presented]) and the beta is finite ([Formula presented]) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen..
433. H Yamada, A Komori, N Ohyabu, O Kaneko, K Kawahata, KY Watanabe, S Sakakibara, S Murakami, K Ida, R Sakamoto, Y Liang, J Miyazawa, K Tanaka, Y Narushima, S Morita, S Masuzaki, T Morisaki, N Ashikawa, LR Baylor, WA Cooper, M Emoto, PW Fisher, H Funaba, M Goto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, K Khlopenkov, T Kobuchi, A Kostrioukov, S Kubo, T Kuroda, R Kumazawa, T Minami, S Muto, T Mutoh, Y Nagayama, N Nakajima, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, T Notake, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, G Rewoldt, A Sagara, K Saito, H Sasao, M Sasao, K Sato, M Sato, T Seki, H Sugama, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, T Watanabe, I Yamada, S Yamamoto, M Yokoyama, Y Yoshimura, T Watari, Y Xu, K Itoh, K Matsuoka, K Ohkubo, T Satow, S Sudo, T Uda, K Yamazaki, O Motojima, M Fujiwara, Configuration flexibility and extended regimes in Large Helical Device, PLASMA PHYSICS AND CONTROLLED FUSION, 43.0, 12A, A55, 2001.12.
434. O. Kaneko, K. Kawahata, A. Komori, N. Ohyabu, H. Yamada, N. Ashikawa', P. DeVries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, S. Kado, K. Khlopenkov, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, T. Kobuchi, Y. Liang, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Sugama, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, K. Y. Watanabe, T. Watari, K. Itoh, K. Matsuoka, K. Ohkubo, I. Ohtake, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, Y. Hamada, O. Motojima, M. Fujiwara, Recent results from the large helical device, Fusion Technology, 39, 2, 322-328, 2001.12, The experimental results from the Large Helical Device (LHD) heliotron / torsatron of the first two years are reviewed. The world's largest superconducting helical coils have been driven up to 2.9 Tesla on the axis which is close to the designed value (3 T). The obtained plasma performances are better than those predicted by the database from the medium-size helical devices. These improvements are attributed mainly to the optimization of a magnetic field configuration which can be controlled by shifting the magnetic axis inward than that of standard case. This configuration improves particle orbits of trapped high energy ions resulting in success of ICRF heating in LHD. Efforts have also been made on steady state plasma operation, and long pulse discharges more than one minute have been achieved both by ICRF and NBI. It should be noted that the feature of no current-disruption in helical plasma makes the discharges easy..
435. KANEKO O.; KAWAHATA K.; KOMORI A.; OHYABU N.; YAMADA H.; ASHIKAWA N.; DEVRIES P.; EMOTO M.; FUNABA H.; GOTO M.; IDA K.; IDEI H.; IKEDA K.; INAGAKI S.; INOUE N.; ISOBE M.; KADO S.; KHLOPENKOV K.; KUBO S.; KUMAZAWA R.; MASUZAKI S.; MINAMI T.; MIYAZAWA J.; MORISAKI T.; MORITA S.; MURAKAMI S.; MUTO S.; MUTOH T.; NAGAYAMA Y.; NAKAJIMA N. ; NAKAMURA Y.; NAKANISHI H.; NARIHARA K.; NISHIMURA K.; NODA N.; NOTAKE T.; KOBUCHI T. ; LIANG Y. ; OHDACHI S. ; OKA Y. ; OSAKABE M. ; OZAKI T. ; PAVLICHENKO R. O. ; PETERSON B. J. ; SAGARA A. ; SAITO K. ; SAKAKIBARA S. ; SAKAMOTO R. ; SASAO H. ; SASAO M. ; SATO K. ; SATO M. ; SEKI T. ; SHIMOZUMA T.; SHOJI M.; SUGAMA H.; SUZUKI H.; TAKECHI M.; TAKEIRI Y.; TAMURA N.;, Recent results from the large helical device, American Nuclear Society Topical Meeting on the Technology of Fusion Energy No14, Park City, Utah , ETATS-UNIS (15/10/2000), 2001, vol. 39 (2), no 2 (890 p.) (20 ref.), [Notes: Selected papers], pp. 322-328, 39.0, 2.0, 322.0-328.0, 2001.10.
436. Fujiwara, M; Kawahata, K; Ohyabu, N; Kaneko, O; Komori, A; Yamada, H; Ashikawa, N; Baylor, LR; Combs, SK; deVries, PC; Emoto, M; Ejiri, A; Fisher, PW; Funaba, H; Goto, M; Hartmann, D; Ida, K; Idei, H; Iio, S; Ikeda, K; Inagaki, S; Inoue, N; Isobe, T; Kado, S; Khlopenkov, K; Kobuchi, T; Krasilnikov, AV; Kubo, S; Kumazawa, R; Leuterer, F; Liang, Y; Lyon, JF; Masuzaki, S; Minami, T; Miyajima, J; Morisaki, T; Morita, S; Murakami, S; Muto, S; Mutoh, T; Nagayama, Y; Nakajima, N; Nakamura, Y; Nakanishi, H; Narihara, K; Nishimura, K; Noda, N; Notake, T; Ohdachi, S; Oka, Y; Okajima, S; Okamoto, M; Osakabe, M; Ozaki, T; Pavlichenko, RO; Peterson, BJ; Sagara, A; Saito, K; Sakakibara, S; Sakamoto, R; Sanuki, H; Sasao, H; Sasao, M; Sato, K; Sato, M; Seki, T; Shimozuma, T; Shoji, M; Sugama, H; Suzuki, H; Takechi, M; Takeiri, Y; Tamura, N; Tanaka, K; Toi, K; Tokuzawa, T; Torii, Y; Tsumori, K; Watanabe, KY; Watanabe, T; Watari, T; Yamada, I; Yamaguchi, S; Yamamoto, S; Yokoyama, M; Yoshida, N; Yoshimura, Y; Zhao, YP; Akiyama, R; Haba, K; Iima, M; Kodaira, J; Takita, T; Tsuzuki, T; Yamauchi, K; Yonezu, H; Chikaraishi, H; Hamaguchi, S; Imagawa, S; Inoue, N; Iwamoto, A; Kitagawa, S; Kubota, Y; Maekawa, R; Mito, T; Murai, K; Nishimura, A; Chikaraishi, H; Takahata, K; Tamura, H; Yamada, S; Yanagi, N; Itoh, K; Matsuoka, K; Ohkubo, K; Ohtake, I; Satoh, S; Satow, T; Sudo, S; Tanahashi, S; Yamazaki, K; Hamada, Y; Motojima, O, Overview of LHD experiments, NUCLEAR FUSION, 10.1088/0029-5515/41/10/305, 41.0, 10.0, 1355.0-1367.0, 0.0, 2001.10, During the first two years of the LHD experiment the following results have been achieved: (i) higher T-e (T-e(0) 4.4 keV at [n(e)] = 5.3 x 10(18) m(-3) and P-abs = 1.8 MW); (ii) higher confinement (tau (E) = 0.3 s, T-e(0) 1.1 keV at [n(e)] = 6.5 x 10(19) m(-3) and P-abs = 2.0 MW) (iii) higher stored energy, W-p(dia) = 880 kJ at B = 2.75 T. High performance plasmas have been realized in the inward shifted magnetic axis configuration (R = 3.6 m) where helical symmetry is recovered and the particle orbit properties are improved by a trade-off of MHD stability properties due to the appearance of a magnetic hill. Energy confinement was systematically higher than that predicted by the International Stellarator Scaling 95 by up to a factor of 1.6 and was comparable with the ELMy H mode confinement capability in tokamaks. This confinement improvement is attributed to configuration control (inward shift of the magnetic axis) and to the formation of a high edge temperature. The average beta value achieved reached 2.4% at B = 1.3 T, the highest beta value ever obtained in a helical device, and so far no degradation of confinement by MHD phenomena has been observed. The inward shifted configuration has also led to successful ICRF minority ion heating. ICRF powers up to 1.3 MW were reliably injected into the plasma without significant impurity contamination, and a plasma with a stored energy of 200 kJ was sustained for 5 s by ICRF alone. As another important result, long pulse discharges of more than 1 min were successfully achieved separately with an NBI heating of 0.5 MW and with an ICRF heating of 0.85 MW..
437. Y Torii, T Watari, R Kumazawa, K Saito, T Mutoh, T Seki, F Shimpo, G Nomura, T Watanabe, N Takeuchi, T Yamamoto, Y Zhao, DA Hartmann, H Yamada, T Ozaki, S Masuzaki, K Tanaka, M Yokota, A Katoh, K Akaishi, N Ashikawa, P De Vries, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, K Itoh, S Kado, O Kaneko, K Kawahata, T Kobuchi, A Komori, AV Krasilnikov, S Kubo, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, S Ohdachi, K Ohkubo, N Ohyabu, Y Oka, M Osakabe, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Shimozuma, M Shoji, S Sudo, Y Takeiri, K Toi, T Tokuzawa, K Tsumori, KY Watanabe, H Suzuki, I Yamada, Y Hamada, S Yamaguchi, S Yamamoto, K Yamazaki, M Yokoyama, Y Yoshimura, O Motojima, M Fujiwara, Derivation of energy confinement time and ICRF absorption in LHD by power modulation, PLASMA PHYSICS AND CONTROLLED FUSION, 43.0, 9.0, 1191.0, 2001.09.
438. S Sakakibara, H Yamada, KY Watanabe, Y Narushima, K Toi, S Ohdachi, M Takechi, S Yamamoto, K Narihara, K Tanaka, N Ashikawa, P De Vries, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, O Kaneko, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, S Kubo, R Kumazawa, Y Liang, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Notake, N Ohyabu, Y Oka, M Osakabe, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, K Saito, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Tamura, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, M Yokoyama, Y Yoshimura, T Watari, N Nakajima, K Ichiguchi, H Takahashi, AW Cooper, K Yamazaki, O Motojima, Y Hamada, M Fujiwara, MHD characteristics in the high beta regime of the Large Helical Device, NUCLEAR FUSION, Vol. 41, No. 9, Pages 1177, 2001.09.
439. K Narihara, KY Watanabe, I Yamada, T Morisaki, K Tanaka, S Sakakibara, K Ida, R Sakamoto, N Ohyabu, N Ashikawa, M Emoto, H Funaba, M Goto, H Hayashi, H Idei, K Ikeda, S Inagaki, N Inoue, O Kaneko, K Kawahata, T Kobuchi, A Komori, S Kubo, R Kumazawa, S Masuzaki, J Miyazawa, S Morita, O Motojima, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Notake, S Ohdachi, Y Oka, K Ohkubo, M Osakabe, S Ozaki, BJ Peterson, A Sagara, K Saito, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, C Shoji, S Sudo, H Suzuki, A Takayama, M Takechi, Y Takeiri, N Tamura, K Toi, N Tokuzawa, Y Torii, K Tsumori, T Watari, H Yamada, S Yamaguchi, S Yamamoto, K Yamazaki, Y Yoshimura, Observation of the “Self-Healing” of an Error Field Island in the Large Helical Device, Physical review letters, 87.0, 13.0, Article No. 135002, 2001.09.
440. Y. Torii, T. Watari, R. Kumazawa, K. Saito, T. Mutoh, T. Seki, F. Shimpo, G. Nomura, T. Watanabe, N. Takeuchi, T. Yamamoto, Y. Zhao, D. A. Hartmann, H. Yamada, T. Ozaki, S. Masuzaki, K. Tanaka, M. Yokota, A. Katoh, K. Akaishi, N. Ashikawa, P. De Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, K. Itoh, S. Kado, O. Kaneko, K. Kawahata, T. Kobuchi, A. Komori, A. V. Krasilnikov, S. Kubo, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, S. Ohdachi, K. Ohkubo, N. Ohyabu, Y. Oka, M. Osakabe, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Shimozuma, M. Shoji, S. Sudo, Y. Takeiri, K. Toi, T. Tokuzawa, K. Tsumori, K. Y. Watanabe, H. Suzuki, I. Yamada, Y. Hamada, S. Yamaguchi, S. Yamamoto, K. Yamazaki, M. Yokoyama, Y. Yoshimura, O. Motojima, M. Fujiwara, Derivation of energy confinement time and ICRF absorption in LHD by power modulation, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/43/9/303, 43, 9, 1191-1210, 2001.09, [URL], A power modulation experiment was conducted in the third campaign of the LHD. In a conventional analysis of the modulation experiments, the energy confinement time and heating efficiency are taken as constant, disregarding their dependence on the plasma parameters. In this paper, their dependence on the plasma temperature and heating power is taken into consideration to improve the analysis of the power modulation experiments. Several models, with differing dependence on the plasma parameters, have been examined. There have been several reports suggesting that the transport coefficients obtained from the dynamical method are different from those obtained from power balance analyses. This paper finally concludes that the energy confinement time obtained from the power modulation experiments well agrees with that obtained from the power balance analysis, made including temperature dependence both in energy confinement time and heating efficiency..
441. S. Morita, M. Goto, H. Funaba, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, O. Kaneko, K. Kawahata, A. Komori, S. Kubo, R. Kumazawa, S. Masuzaki, J. Miyazawa, T. Morisaki, O. Motojima, S. Muto, T. Mutoh, Y. Nakamura, K. Narihara, K. Nishimura, N. Noda, S. Ohdachi, N. Ohyabu, Y. Oka, M. Osakabe, A. Sagara, S. Sakakibara, R. Sakamoto, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, H. Yamada, K. Y. Watanabe, T. Watari, Effect of carbon divertor plates on impurities, Zeff and density limit in large helical device, 9th Internationsl Workshop on Carbon Materials
Physica Scripta T
, 91, 48-52, 2001.09, LHD (Large Helical Device) has been operated during 2 years after initiating the first plasma on March of 1998. During the first year (1st and 2nd experimental campaigns) the discharges were mainly carried out with a low magnetic field of Bt = 1.5 T Before the 3rd experimental campaign begin in 1999, carbon divertor plates were installed in the vacuum chamber at the end of the divertor legs. These were connected to the ergodic layer for the purpose of heat removal and separation from the vacuum wall (SS316L). After the installation metal impurities decreased and high influxes of carbon and oxygen were measured. During accumulated number of discharges the metal impurities increased and returned finally to the former level. The re-deposition of metals on the carbon plates was also observed. However, discharges were successful and the impurity level did not lower critically the plasma performance. The behaviour of impurities, Zeff (effective charge) and density limit is discussed and r esults from spectroscopic measurements are presented..
442. S. Sakakibara, H. Yamada, K. Y. Watanabe, Y. Narushima, K. Toi, S. Ohdachi, M. Takechi, S. Yamamoto, K. Narihara, K. Tanaka, N. Ashikawa, P. De Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, S. Kado, O. Kaneko, K. Kawahata, K. Khlopenkov, T. Kobuchi, A. Komori, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Notake, N. Ohyabu, Y. Oka, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Tamura, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, M. Yokoyama, Y. Yoshimura, T. Watari, N. Nakajima, K. Ichiguchi, H. Takahashi, A. W. Cooper, K. Yamazaki, O. Motojima, Y. Hamada, M. Fujiwara, MHD characteristics in the high beta regime of the Large Helical Device, Nuclear Fusion, 10.1088/0029-5515/41/9/306, 41, 9, 1177-1183, 2001.09, [URL], The highest volume averaged beta values βt of 2.2% at Bt = 0.75 T (gas puff) and 2.4% at βt, = 1.3 T (pellet) in helical devices have been achieved in LHD. The βt dependence of MHD activities has been investigated in NBI plasmas. The n/m = 1/2 mode, excited in the core region, and the t = 1 resonant modes, in the peripheral region, have been observed. Both of the fluctuation amplitudes increase with βt and pressure gradient. The strong n/m = 1/2 mode, which affects the plasma profile, has been observed in high βt discharges, and the abrupt disappearance of the mode leads to restoration of the Te profile. Violent instabilities which terminate the plasma and degradation of global energy confinement have not been observed so far..
443. K Saito, R Kumazawa, T Mutoh, T Seki, T Watari, Y Torii, DA Hartmann, Y Zhao, A Fukuyama, F Shimpo, G Nomura, M Yokota, M Sasao, M Isobe, M Osakabe, T Ozaki, K Narihara, Y Nagayama, S Inagaki, K Itoh, S Morita, AV Krasilnikov, K Ohkubo, M Sato, S Kubo, T Shimozuma, H Idei, Y Yoshimura, O Kaneko, Y Takeiri, Y Oka, K Tsumori, K Ikeda, A Komori, H Yamada, H Funaba, KY Watanabe, S Sakakibara, M Shoji, R Sakamoto, J Miyazawa, K Tanaka, BJ Peterson, N Ashikawa, S Murakami, T Minami, S Ohdachi, S Yamamoto, S Kado, H Sasao, H Suzuki, K Kawahata, P De Vries, M Emoto, H Nakanishi, T Kobuchi, N Inoue, N Ohyabu, Y Nakamura, S Masuzaki, S Muto, K Sato, T Morisaki, M Yokoyama, T Watanabe, M Goto, I Yamada, K Ida, T Tokuzawa, N Noda, S Yamaguchi, K Akaishi, A Sagara, K Toi, K Nishimura, K Yamazaki, S Sudo, Y Hamada, O Motojima, M Fujiwara, Ion and electron heating in ICRF heating experiments on LHD, NUCLEAR FUSION, 41.0, 8.0, 1021.0, 2001.08.
444. K. Saito, R. Kumazawa, T. Mutoh, T. Seki, T. Watari, Y. Torii, D. A. Hartmann, Y. Zhao, A. Fukuyama, F. Shimpo, G. Nomura, M. Yokota, M. Sasao, M. Isobe, M. Osakabe, T. Ozaki, K. Narihara, Y. Nagayama, S. Inagaki, K. Itoh, S. Morita, A. V. Krasilnikov, K. Ohkubo, M. Sato, S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, O. Kaneko, Y. Takeiri, Y. Oka, K. Tsumori, K. Ikeda, A. Komori, H. Yamada, H. Funaba, K. Y. Watanabe, S. Sakakibara, M. Shoji, R. Sakamoto, J. Miyazawa, K. Tanaka, B. J. Peterson, N. Ashikawa, S. Murakami, T. Minami, S. Ohdachi, S. Yamamoto, S. Kado, H. Sasao, H. Suzuki, K. Kawahata, P. De Vries, M. Emoto, H. Nakanishi, T. Kobuchi, N. Inoue, N. Ohyabu, Y. Nakamura, S. Masuzaki, S. Muto, K. Sato, T. Morisaki, M. Yokoyama, T. Watanabe, M. Goto, I. Yamada, K. Ida, T. Tokuzawa, N. Noda, S. Yamaguchi, K. Akaishi, A. Sagara, K. Toi, K. Nishimura, K. Yamazaki, S. Sudo, Y. Hamada, O. Motojima, M. Fujiwara, Ion and electron heating in ICRF heating experiments on LHD, Nuclear Fusion, 10.1088/0029-5515/41/8/306, 41, 8, 1021-1035, 2001.08, [URL], The ICRF heating experiments conducted in 1999 in the third experimental campaign on LHD are reported, with an emphasis on the optimization of the heating regime. Specifically. an exhaustive study of seven different heating regimes was carried out by changing the radiofrequency relative to the magnetic field intensity, and the dependence of the heating efficiency on H minority concentration was investigated. It was found in the experiment that both ion and electron heating are attainable with the same experimental set-up by properly choosing the frequency relative to the magnetic field intensity. In the cases of both electron heating and ion heating, the power absorption efficiency depends on the minority ion concentration. An optimum minority concentration exists in the ion heating case while, in the electron heating case, the efficiency increases with concentration monotonically. A simple model calculation is introduced to provide a heuristic understanding of these experimental results. Among the heating regimes examined in this experiment, one of the ion heating regimes was finally chosen as the optimized heating regime and various high performance discharges were realized with it..
445. H Yamada, KY Watanabe, K Yamazaki, S Murakami, S Sakakibara, K Narihara, K Tanaka, M Osakabe, K Ida, N Ashikawa, PC De Vries, M Emoto, H Funaba, M Goto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, O Kaneko, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, S Kubo, R Kumazawa, Y Liang, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Muto, T Mutoh, Y Nagayama, N Nakajima, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Notake, S Ohdachi, N Ohyabu, Y Oka, T Ozaki, RO Pavlichenko, BJ Peterson, G Rewoldt, A Sagara, K Saito, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Sugama, H Suzuki, M Takechi, Y Takeiri, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, M Yokoyama, Y Yoshimura, T Watari, K Itoh, K Matsuoka, K Ohkubo, I Ohtake, S Satoh, T Satow, S Sudo, S Tanahashi, T Uda, Y Hamada, O Motojima, M Fujiwara, Energy confinement and thermal transport characteristics of net current free plasmas in the Large Helical Device, NUCLEAR FUSION, 84.0, 7.0, 901.0, 2001.07.
446. H. Yamada, K. Y. Watanabe, K. Yamazaki, S. Murakami, S. Sakakibara, K. Narihara, K. Tanaka, M. Osakabe, K. Ida, N. Ashikawa, P. C. De Vries, M. Emoto, H. Funaba, M. Goto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, S. Kado, O. Kaneko, K. Kawahata, K. Khlopenkov, T. Kobuchi, A. Komori, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Muto, T. Mutoh, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, N. Ohyabu, Y. Oka, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, G. Rewoldt, A. Sagara, K. Saito, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Sugama, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, T. Watari, K. Itoh, K. Matsuoka, K. Ohkubo, I. Ohtake, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, T. Uda, Y. Hamada, O. Motojima, M. Fujiwara, Energy confinement and thermal transport characteristics of net current free plasmas in the large helical device, Nuclear Fusion, 10.1088/0029-5515/41/7/311, 41, 7, 901-908, 2001.07, [URL], The energy confinement and thermal transport characteristics of net current free plasmas in regimes with much smaller gyroradii and collisionality than previously studied have been investigated in the Large Helical Device (LHD). The inward shifted configuration, which is superior from the point of view of neoclassical transport theory, has revealed a systematic confinement improvement over the standard configuration. Energy confinement times are improved over the International Stellarator Scaling 95 by a factor of 1.6 ± 0.2 for an inward shifted configuration. This enhancement is primarily due to the broad temperature profile with a high edge value. A simple dimensional analysis involving LHD and other medium sized heliotrons yields a strongly gyro-Bohm dependence (τEΩ ∝ ρ*-3.8) of energy confinement times. It should be noted that this result is attributed to a comprehensive treatment of LHD for systematic confinement enhancement and that the medium sized heliotrons have narrow temperature profiles. The core stored energy still indicates a dependence of τEΩ ∝ ρ*-2.6 when data only from LHD are processed. The local heat transport analysis of discharges dimensionally similar except for ρ* suggests that the heat conduction coefficient lies between Bohm and gyro-Bohm in the core and changes towards strong gyro-Bohm in the peripheral region. Since the inward shifted configuration has a geometrical feature suppressing neoclassical transport, confinement improvement can be maintained in the collisionless regime where ripple transport is important. The stiffness of the pressure profile coincides with enhanced transport in the peaked density profile obtained by pellet injection..
447. A. Komori, R. Sakamoto, T. Morisaki, J. Miyazawa, K. Narihara, B. J. Peterson, S. Masuzaki, S. Sakakibara, H. Suzuki, M. Shoji, S. Inagaki, H. Yamada, N. Ohyabu, H. Idei, K. Ikeda, S. Kubo, S. Morita, S. Murakami, T. Mutoh, Y. Narushima, S. Ohdachi, T. Seki, K. Tanaka, K. Tsumori, K. Y. Watanabe, O. Kaneko, K. Kawahata, O. Motojima and the LHD Experimental Group , Effect of Magnetic Islands on LHD Plasma Performance, 28th EPS Conference On Contr. Fusion Phys., 25A, 1505.0-1508.0, 2001.06.
448. N Noda, Y Nakamura, Y Takeiri, T Mutoh, R Kumazawa, M Sato, K Kawahata, S Yamada, T Shimozuma, Y Oka, A Iiyoshi, R Sakamoto, Y Kubota, S Masuzaki, S Inagaki, T Morisaki, H Suzuki, N Ohyabu, K Adachi, K Akaishi, N Ashikawa, H Chikaraishi, PC De Vries, M Emoto, H Funaba, M Goto, S Hamaguchi, K Ida, H Idei, K Ikeda, S Imagawa, N Inoue, M Isobe, A Iwamoto, S Kado, O Kaneko, S Kitagawa, K Khlopenkov, T Kobuchi, A Komori, S Kubo, Y Liang, R Maekawa, T Minami, T Mito, J Miyazawa, S Morita, K Murai, S Murakami, S Muto, Y Nagayama, H Nakanishi, K Narihara, A Nishimura, K Nishimura, A Nishizawa, T Notake, S Ohdachi, M Okamoto, M Osakabe, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, K Saito, S Sakakibara, H Sasao, M Sasao, K Sato, T Seki, M Shoji, H Sugama, K Takahata, M Takechi, H Tamura, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, KY Watanabe, T Watanabe, T Watari, N Yanagi, I Yamada, H Yamada, S Yamaguchi, S Yamamoto, T Yamamoto, M Yokoyama, Y Yoshimura, I Ohtake, R Akiyama, K Haba, M Iima, J Kodaira, K Tsuzuki, K Itoh, K Matsuoka, K Ohkubo, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, O Motojima, Y Hamada, M Fujiwara, Experimental studies towards long pulse steady state operation in LHD, NUCLEAR FUSION, 41.0, 6.0, Article No. 779, 2001.06.
449. K Ida, H Funaba, S Kado, K Narihara, K Tanaka, Y Takeiri, Y Nakamura, N Ohyabu, K Yamazaki, M Yokoyama, S Murakami, N Ashikawa, M Emoto, M Goto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, K Itoh, O Kaneko, K Kawahata, K Khlopenkov, A Komori, S Kubo, R Kumazawa, Y Liang, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, T Mutoh, S Muto, Y Nagayama, H Nakanishi, K Nishimura, N Noda, T Notake, T Kobuchi, S Ohdachi, K Ohkubo, Y Oka, M Osakabe, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, K Saito, S Sakakibara, R Sakamoto, H Sanuki, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, S Sudo, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, T Yamamoto, H Yamada, I Yamada, S Yamaguchi, S Yamamoto, Y Yoshimura, KY Watanabe, T Watari, Y Hamada, O Motojima, M Fujiwara, Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device, Physical review letters, 86.0, 23.0, 5297.0, 2001.06.
450. B. J. Peterson, H. Funaba, K. Itoh, J. E. Rice, K. Yamazaki, Y. Nakamura, N. Noda, Y. Takeiri, Yuhong Xu, N. Ashikawa, K. Narihara, K. Tanaka, S. Masuzaki, T. Tokuzawa, K. Sato, M. Goto, K. Ida, S. Sakakibara, J. Miyazawa, M. Osakabe, A. Kostrioukov, K. Tsumori, K. Ikeda, S. Kubo, H. Idei, K. Kawahata, H. Yamada, O. Kaneko, N. Ohyabu, K. Komori, S. Sudo, O. Motojima and the LHD Experimental Group, Role of Changing Transport in 'Breathing' Oscillations in LHD
, Proc. of 28th EPS Conference on Controlled Fusion and Plasma Physics, P4.044, 2001.06.
451. N. Noda, Y. Nakamura, Y. Takeiri, T. Mutoh, R. Kumazawa, M. Sato, K. Kawahata, S. Yamada, T. Shimozuma, Y. Oka, A. Iiyoshi, R. Sakamoto, Y. Kubota, S. Masuzaki, S. Inagaki, T. Morisaki, H. Suzuki, N. Ohyabu, K. Adachi, K. Akaishi, N. Ashikawa, H. Chikaraishi, P. C. De Vries, M. Emoto, H. Funaba, M. Goto, S. Hamaguchi, K. Ida, H. Idei, K. Ikeda, S. Imagawa, N. Inoue, M. Isobe, A. Iwamoto, S. Kado, O. Kaneko, S. Kitagawa, K. Khlopenkov, T. Kobuchi, A. Komori, S. Kubo, Y. Liang, R. Maekawa, T. Minami, T. Mito, J. Miyazawa, S. Morita, K. Murai, S. Murakami, S. Muto, Y. Nagayama, H. Nakanishi, K. Narihara, A. Nishimura, K. Nishimura, A. Nishizawa, T. Notake, S. Ohdachi, M. Okamoto, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, H. Sasao, M. Sasao, K. Sato, T. Seki, M. Shoji, H. Sugama, K. Takahata, M. Takechi, H. Tamura, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, K. Y. Watanabe, T. Watanabe, T. Watari, N. Yanagi, I. Yamada, H. Yamada, S. Yamaguchi, S. Yamamoto, T. Yamamoto, M. Yokoyama, Y. Yoshimura, I. Ohtake, R. Akiyama, K. Haba, M. Iima, J. Kodaira, K. Tsuzuki, K. Itoh, K. Matsuoka, K. Ohkubo, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, O. Motojima, Y. Hamada, M. Fujiwara, Experimental studies towards long pulse steady state operation in LHD, Nuclear Fusion, 10.1088/0029-5515/41/6/314, 41, 6, 779-790, 2001.06, [URL], In the Large Helical Device, stable discharges lasting longer than one minute have been obtained using the complete heating scheme, including ECH. The plasma is sustained with NBI or ICRF of 0.5-1 MW. The central plasma temperature is higher than 1.5 keV with a density of (1-2) × 1019 m-3 maintained until the end of the pulse. Full installation of the carbon divertor has contributed to this achievement. This provides a sufficient basis for physics and technology studies for the next campaign. Long pulse operation opens new possibilities in diagnostics and in physics studies. Higher accuracy and reliability are obtained with a diagnostics parameter scan, longer integration of signals or two dimensional measurement. The mechanism of a slow oscillation called 'breathing' is discussed. Hydrogen recycling analysis has been carried out and preliminary results have been obtained. On the basis of these results, the future programme is divided into two categories: (i) physics and technology experiments utilizing long pulse discharges lasting up to 5 minutes, and (ii) extension of the pulse length up to one hour..
452. K. Ida, H. Funaba, S. Kado, K. Narihara, K. Tanaka, Y. Takeiri, Y. Nakamura, N. Ohyabu, K. Yamazaki, M. Yokoyama, S. Murakami, N. Ashikawa, P. C. DeVries, M. Emoto, M. Goto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, K. Itoh, O. Kaneko, K. Kawahata, K. Khlopenkov, A. Komori, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, T. Mutoh, S. Muto, Y. Nagayama, H. Nakanish, K. Nishimura, N. Noda, T. Notake, T. Kobuchi, S. Ohdachi, K. Ohkubo, Y. Oka, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, H. Sanuki, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, S. Sudo, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Yamamoto, H. Yamada, I. Yamada, S. Yamaguchi, S. Yamamoto, Y. Yoshimura, K. Y. Watanabe, T. Watari, Y. Hamada, O. Motojima, M. Fujiwara, Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device, Physical Review Letters, 10.1103/PhysRevLett.86.5297, 86, 23, 5297-5300, 2001.06, [URL], A study of reduction of ion thermal diffusivity in the neutral-beam-heated plasmas in the large helical device was performed. The thermal diffusivity was associated with the transition of the radial electric field. There was a good agreement of the values of radial electric field with the neoclassical theory. There was significant increase of electron temperature and a clear reduction of electron thermal diffusivity in the plasma core in the electron root..
453. Akio Komori, N Ohyabu, H Yamada, O Kaneko, K Kawahata, N Ashikawa, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, K Khlopenkov, T Kobuchi, S Kubo, R Kumazawa, Y Liang, S Masuzaki, Y Matsumoto, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, Y Narushima, K Nishimura, N Noda, T Notake, S Ohdachi, Y Oka, M Okamoto, M Osakabe, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, K Saito, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, M Takechi, Y Takeiri, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, M Yokoyama, Y Yoshimura, KY Watanabe, T Watanabe, T Watari, Y Hamada, K Itoh, K Matsuoka, K Ohkubo, T Satow, S Sudo, K Yamazaki, O Motojima, M Fujiwara, Improved plasma performance on Large Helical Device, PHYSICS OF PLASMAS, 8.0, 5.0, 2002.0-2008.0, 2001.05.
454. R Kumazawa, T Mutoh, T Seki, T Watari, K Saito, Y Torii, F Shimpo, G Nomura, M Yokota, A Kato, DA Hartmann, Y Zhao, A Fukuyama, H Okada, K Ohkubo, M Sato, S Kubo, T Shimozuma, H Idei, Y Yoshimura, T Notake, Y Takita, S Kobayashi, S Itoh, Y Mizuno, O Kaneko, Y Takeiri, Y Oka, K Tsumori, M Osakabe, K Ikeda, S Yamamoto, T Kawamoto, E Asano, N Ohyabu, K Kawahata, A Komori, H Yamada, K Akaishi, N Ashikawa, M Emoto, H Funaba, M Goto, K Ida, S Inagaki, N Inoue, M Isobe, A Krasilnikov, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, Y Nakamura, Y Nagayama, H Nakanishi, K Narihara, Y Narushima, K Nishimura, N Noda, T Kobuchi, S Ohdachi, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Shoji, H Suzuki, K Tanaka, K Toi, T Tokuzawa, I Yamada, S Yamaguchi, M Yokoyama, KY Watanabe, T Watanabe, K Matsuoka, K Itoh, S Sudo, K Yamazaki, Y Hamada, O Motojima, M Fujiwara, Ion cyclotron range of frequency heating experiments on the large helical device and high energy ion behavior, PHYSICS OF PLASMAS, 8.0, 5.0, 2139.0-2147.0, 2001.05.
455. BJ Peterson, Y Nakamura, K Yamazaki, N Noda, J Rice, Y Takeiri, M Goto, K Narihara, K Tanaka, K Sato, S Masuzaki, S Sakakibara, K Ida, H Funaba, M Shoji, M Osakabe, M Sato, Yuhong Xu, T Kobuchi, N Ashikawa, PC De Vries, M Emoto, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, K Khlopenkov, S Kubo, R Kumazawa, T Minami, J Miyazawa, T Morisaki, S Murakami, S Muto, T Mutoh, Y Nagayama, H Nakanishi, K Nishimura, T Notake, Y Liang, S Ohdachi, Y Oka, T Ozaki, RO Pavlichenko, A Sagara, K Saito, R Sakamoto, H Sasao, M Sasao, T Seki, T Shimozuma, H Suzuki, M Takechi, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, M Yokoyama, Y Yoshimura, KY Watanabe, T Watari, K Kawahata, O Kaneko, N Ohyabu, H Yamada, A Komori, S Sudo, O Motojima, Role of core radiation during slow oscillations in LHD, NUCLEAR FUSION, Vol. 41, No. 5, Pages 519, 2001.05.
456. A. Komori, N. Ohyabu, H. Yamada, O. Kaneko, K. Kawahata, N. Ashikawa, P. DeVaries, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, S. Kado, K. Khlopenkov, T. Kobuchi, S. Kubo, R. Kumazawa, Y. Liang, S. Masuzaki, Y. Matsumoto, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, Y. Narushima, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, Y. Oka, M. Okamoto, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, K. Y. Watanabe, T. Watanabe, T. Watari, Y. Hamada, K. Itoh, K. Matsuoka, K. Ohkubo, T. Satow, S. Sudo, K. Yamazaki, O. Motojima, M. Fujiwara, Improved plasma performance on Large Helical Device, 42nd Annual Meeting of the APS Division of Plasma Physics
Physics of Plasmas
, 10.1063/1.1344561, 8, 5 II, 2002-2008, 2001.05, [URL], Since the start of the Large Helical Device (LHD) experiment, various attempts have been made to achieve improved plasma performance in LHD [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. Recently, an inward-shifted configuration with a magnetic axis position R
ax
of 3.6 m has been found to exhibit much better plasma performance than the standard configuration with R
ax
of 3.75 m. A factor of 1.6 enhancement of energy confinement time was achieved over the International Stellarator Scaling 95. This configuration has been predicted to have unfavorable magnetohydrodynamic (MHD) properties, based on linear theory, even though it has significantly better particle-orbit properties, and hence lower neoclassical transport loss. However, no serious confinement degradation due to the MHD activities was observed, resolving favorably the potential conflict between stability and confinement at least up to the realized volume-averaged beta 〈β〉 of 2.4%. An improved radial profile of electron temperature was also achieved in the configuration with magnetic islands, minimized by an external perturbation coil system for the Local Island Divertor (LID). The LID has been proposed for remarkable improvement of plasma confinement like the high (H) mode in tokamaks, and the LID function was suggested in limiter experiments..
457. R. Kumazawa, T. Mutoh, T. Seki, T. Watari, K. Saito, Y. Torii, F. Shimpo, G. Nomura, M. Yokota, A. Kato, D. A. Hartmann, Y. Zhao, A. Fukuyama, H. Okada, K. Ohkubo, M. Sato, S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, T. Notake, Y. Takita, S. Kobayashi, S. Itoh, Y. Mizuno, O. Kaneko, Y. Takeiri, Y. Oka, K. Tsumori, M. Osakabe, K. Ikeda, S. Yamamoto, T. Kawamoto, E. Asano, N. Ohyabu, K. Kawahata, A. Komori, H. Yamada, K. Akaishi, N. Ashikawa, M. Emoto, H. Funaba, M. Goto, K. Ida, S. Inagaki, N. Inoue, M. Isobe, A. Krasilnikov, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, Y. Nakamura, Y. Nagayama, H. Nakanishi, K. Narihara, Y. Narushima, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, T. Ozaki, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Shoji, H. Suzuki, K. Tanaka, K. Toi, T. Tokuzawa, I. Yamada, S. Yamaguchi, M. Yokoyama, K. Y. Watanabe, T. Watanabe, K. Matsuoka, K. Itoh, S. Sudo, K. Yamazaki, Y. Hamada, O. Motojima, M. Fujiwara, Ion Cyclotron range of frequency heating experiments on the large helical device and high energy ion behavior, 42nd Annual Meeting of the APS Division of Plasma Physics
Physics of Plasmas
, 10.1063/1.1354152, 8, 5 II, 2139-2147, 2001.05, [URL], Ion cyclotron range of frequency (ICRF) heating experiments on the Large Helical Device (LHD) [O. Motojima et al. Fus. Eng. Des. 20, 3 (1993)] achieved significant advances during the third experimental campaign carried out in 1999. They showed significant results in two heating modes; these are modes of the ICH-sustained plasma with large plasma stored energy and the neutral beam injection (NBI) plasma under additional heating. A long-pulse operation of more than 1 minute was achieved at a level of 1 MW. The characteristics of the ICRF heated plasma are the same as those of the NBI heated plasma. The energy confinement time is longer than that of International Stellarator Scaling 95. Three keys to successful ICRF heating are as follows: (1) an increase in the magnetic field strength, (2) the employment of an inward shift of the magnetic axis, (3) the installation of actively cooled graphite plates along the divertor legs. Highly energetic protons accelerated by the ICRF electric field were experimentally observed in the energy range from 30 to 250 keV and the tail temperature depended on the energy balance between the wave heating and the electron drag. The transfer efficiency from the high energy ions to the bulk plasma was deduced from the increase in the energy confinement time due to the high energy ions in the lower density discharge, which agrees fairly well with the result obtained by the Monte Carlo simulation. The transfer efficiency is expected to be 95% at an electron density of more than ne = 5.0× 1019m-3 even in the high power heating of 10 MW. The accumulation of impurities, e.g., FeXVI and OV was not observed in high rf power and long pulse operation. The well-defined divertor intrinsic to LHD is believed to be useful in reducing the impurity influx..
458. B. J. Peterson, Y. Nakamura, K. Yamazaki, N. Noda, J. Rice, Y. Takeiri, M. Goto, K. Narihara, K. Tanaka, K. Sato, S. Masuzaki, S. Sakakibara, K. Ida, H. Funaba, M. Shoji, M. Osakabe, M. Sato, Yuhong Xu, T. Kobuchi, N. Ashikawa, P. C. De Vries, M. Emoto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, S. Kado, K. Khlopenkov, S. Kubo, R. Kumazawa, T. Minami, J. Miyazawa, T. Morisaki, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, H. Nakanishi, K. Nishimura, T. Notake, Y. Liang, S. Ohdachi, Y. Oka, T. Ozaki, R. O. Pavlichenko, A. Sagara, K. Saito, R. Sakamoto, H. Sasao, M. Sasao, T. Seki, T. Shimozuma, H. Suzuki, M. Takechi, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, K. Y. Watanabe, T. Watari, K. Kawahata, O. Kaneko, N. Ohyabu, H. Yamada, A. Komori, S. Sudo, O. Motojima, Role of core radiation during slow oscillations in LHD, Nuclear Fusion, 10.1088/0029-5515/41/5/305, 41, 5, 519-525, 2001.05, [URL], During experiments in LHD using stainless steel divertor plates, a slow (∼1 s) cyclic oscillation in the plasma parameters known as 'breathing' plasma was observed during NBI heated long pulse discharges. Using an average ion, corona equilibrium model for the iron impurity cooling rate, the iron impurity density profile is calculated for 0.0 < ρ < 0.8 from the measured electron temperature and density profiles and radiation profile data for these discharges in LHD. This calculated iron density oscillates out of phase with the electron density and peaks near ρ = 0.4 at a fraction of the electron density that varies by a factor of 4. This is in qualitative agreement with spectroscopic measurements of iron that show a similar oscillation. The correlation of the iron impurity concentration with the change in electron temperature and with the local power balance between radiation and beam deposition indicates that when radiation from the iron impurity dominates the local power balance the core plasma is cooled. The increase in the calculated iron density during the phase of the oscillation when the divertor electron temperature exceeds the sputtering threshold suggests that sputtering of the stainless steel divertor plate may be the source of the iron impurity. Evidence of changing transport points to the need for a closer examination of the role of impurity transport in this oscillation..
459. R Sakamoto, H Yamada, K Tanaka, K Narihara, S Morita, S Sakakibara, S Masuzaki, S Inagaki, Larry R Baylor, Paul W Fisher, Stephen Kirk Combs, Michael J Gouge, S Kato, A Komori, O Kaneko, N Ashikawa, P de Vries, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, M Isobe, S Kado, K Kawahata, K Khlopenkov, S Kubo, R Kumazawa, T Minami, J Miyazawa, T Morisaki, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Notake, T Kobuchi, Y Liang, S Ohdachi, N Ohyabu, Y Oka, M Osakabe, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, K Saito, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, S Sudo, H Suzuki, M Takechi, Y Takeiri, N Tamura, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, Y Yoshimura, KY Watanabe, T Watari, K Yamazaki, Y Hamada, O Motojima, M Fujiwara, Impact of pellet injection on extension of the operational region in LHD, NUCLEAR FUSION, 41.0, 4.0, 381.0, 2001.04.
460. R. Sakamoto, H. Yamada, K. Tanaka, K. Narihara, S. Morita, S. Sakakibara, S. Masuzaki, S. Inagaki, L. R. Baylor, P. W. Fisher, S. K. Combs, M. J. Gouge, S. Kato, A. Komori, O. Kaneko, N. Ashikawa, P. De Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, K. Ikeda, M. Isobe, S. Kado, K. Kawahata, K. Khlopenkov, S. Kubo, R. Kumazawa, T. Minami, J. Miyazawa, T. Morisaki, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Notake, T. Kobuchi, Y. Liang, S. Ohdachi, N. Ohyabu, Y. Oka, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, S. Sudo, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, Y. Yoshimura, K. Y. Watanabe, T. Watari, K. Yamazaki, Y. Hamada, O. Motojima, M. Fujiwara, Impact of pellet injection on extension of the operational region in LHD, Nuclear Fusion, 10.1088/0029-5515/41/4/304, 41, 4, 381-386, 2001.04, [URL], Pellet injection has been used as a primary fuelling scheme in the Large Helical Device. With pellet injection, the operational region of NBI plasmas has been extended to higher densities while maintaining a favourable dependence of energy confinement on density, and several important values, such as plasma stored energy of 0.88 MJ, energy confinement time of 0.3 s, β of 2.4% at 1.3 T and density of 1.1 × 1020 m-3, have been achieved. These parameters cannot be attained by gas puffing. Ablation and the subsequent behaviour of the plasma have been investigated. The measured pellet penetration depth estimated on the basis of the duration of the Hα emission is shallower than the depth predicted from the simple neutral gas shielding (NGS) model. It can be explained by the NGS model with inclusion of the effect of fast ions on the ablation. Just after ablation, the redistribution of the ablated pellet mass was observed on a short timescale (∼400 ms). The redistribution causes shallow deposition and low fuelling efficiency..
461. T Watari, T Mutoh, R Kumazawa, T Seki, K Saito, Y Torii, Yan Ping Zhao, D Hartmann, H Idei, S Kubo, K Ohkubo, M Sato, T Shimozuma, Y Yoshimura, K Ikeda, O Kaneko, Y Oka, M Osakabe, Y Takeiri, K Tsumori, N Ashikawa, PC De Vries, M Emoto, A Fukuyama, H Funaba, M Goto, K Ida, S Inagaki, N Inoue, M Isobe, K Itoh, S Kado, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, AV Krasilnikov, Y Liang, S Masuzaki, K Matsuoka, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, AT Notake, S Ohdachi, N Ohyabu, H Okada, M Okamoto, T Ozaki, RO Pavlichenko, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, S Satoh, T Satow, M Shoji, S Sudo, H Suzuki, M Takechi, N Tamura, S Tanahashi, K Tanaka, K Toi, T Tokuzawa, KY Watanabe, T Watanabe, H Yamada, I Yamada, S Yamaguchi, S Yamamoto, K Yamazaki, M Yokoyama, Y Hamada, O Motojima, M Fujiwara, The performance of ICRF heated plasmas in LHD, NUCLEAR FUSION, Vol. 41, No. 3, Pages 325, 2001.03.
462. T. Watari, T. Mutoh, R. Kumazawa, T. Seki, K. Saito, Y. Torii, Yan Ping Zhao, D. Hartmann, H. Idei, S. Kubo, K. Ohkubo, M. Sato, T. Shimozuma, Y. Yoshimura, K. Ikeda, O. Kaneko, Y. Oka, M. Osakabe, Y. Takeiri, K. Tsumori, N. Ashikawa, P. C. De Vries, M. Emoto, A. Fukuyama, H. Funaba, M. Goto, K. Ida, S. Inagaki, N. Inoue, M. Isobe, K. Itoh, S. Kado, K. Kawahata, K. Khlopenkov, T. Kobuchi, A. Komori, A. V. Krasilnikov, Y. Liang, S. Masuzaki, K. Matsuoka, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, A. T. Notake, S. Ohdachi, N. Ohyabu, H. Okada, M. Okamoto, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, S. Satoh, T. Satow, M. Shoji, S. Sudo, H. Suzuki, M. Takechi, N. Tamura, S. Tanahashi, K. Tanaka, K. Toi, T. Tokuzawa, K. Y. Watanabe, T. Watanabe, H. Yamada, I. Yamada, S. Yamaguchi, S. Yamamoto, K. Yamazaki, M. Yokoyama, Y. Hamada, O. Motojima, M. Fujiwara, The performance of ICRF heated plasmas in LHD, Nuclear Fusion, 10.1088/0029-5515/41/3/310, 41, 3, 325-332, 2001.03, [URL], An ion cyclotron range of frequency (ICRF) heating experiment was conducted in the third campaign of LHD in 1999. 1.35 MW of ICRF power were injected into the plasma and 200 kJ of stored energy were obtained, which was maintained for 5 s by ICRF power only after the termination of ECH. The impurity problem was so completely overcome that the pulse length was easily extended to 68 s at a power level of 0.7 MW. The utility of a liquid stub tuner in steady state plasma heating was demonstrated in this discharge. The energy confinement time of the ICRF heated plasma has the same dependences on plasma parameters as those of the ISS95 stellarator scaling with a multiplication factor of 1.5, which is a high efficiency comparable to that of NBI. Such an improvement in performance was obtained by various means, including: (a) scanning of the magnetic field intensity and minority concentration, (b) improvement of particle orbits due to a shift of magnetic axis and (c) reduction of the number of impurity ions by means of titanium gettering and the use of carbon divertor plates. In the optimized heating regime, ion heating turned out to be the dominant heating mechanism, unlike in CHS and WT-AS. Owing to the high quality of the heating and the parameter range being extended far beyond that of previous experiments, the experiment can be regarded as the first complete demonstration of ICRF heating in stellarators..
463. T Shimozuma, S Kubo, M Sato, H Idei, Y Takita, S Ito, S Kobayashi, Y Mizuno, Y Yoshimura, K Ohkubo, H Funaba, S Inagaki, T Kobuchi, S Masuzaki, S Muto, M Shoji, H Suzuki, N Noda, Y Nakamura, K Kawahata, N Ohyabu, O Motojima, ECH system and its application to long pulse discharge in large helical device, FUSION ENGINEERING AND DESIGN, 53.0, 1.0, 525.0-536.0, 2001.01.
464. S Morita, M Goto, H Funaba, H Idei, K Ikeda, S Inagaki, O Kaneko, K Kawahata, A Komori, S Kubo, R Kumazawa, S Masuzaki, J Miyazawa, T Morisaki, O Motojima, S Muto, T Mutoh, Y Nakamura, K Narihara, K Nishimura, N Noda, S Ohdachi, N Ohyabu, Y Oka, M Osakabe, A Sagara, S Sakakibara, R Sakamoto, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, H Yamada, KY Watanabe, T Watari, Effect of carbon divertor plates on impurities, Zeff and density limit in large helical device, PHYSICA SCRIPTA, 2001.0, T91, 48.0, 2001.01.
465. NISHIMURA Kiyohiko, IDA Katsumi, KAWAHATA Kazuo, YAMAZAKI Kozo, ASHIKAWA Naoko, EMOTO Masahiko, FUNABA Hisamichi, GOTO Motoshi, IDEI Hiroshi, IKEDA Katsunori, INAGAKI Shigeru, INOUE Noriyuki, ISOBE Mitsutaka, KANEKO Osamu, KHLOPENKOV Konstantin, KOMORI Akio, KUBO Shin, KUMAZAWA Ryuhei, LIANG Yunfeng. MASUZAKI Suguru, MINAMI Takashi, MIYAZAWA Junichi, MORISAKI Tomohiro, MORITA Shigeru, MURAKAMI Sadayoshi, MUTO Sadatsugu, MUTOH Takashi, NAGAYAMA Yoshio, NAKAMURA Yukio, NAKANISHI Hideya, NARIHARA Kazumichi, NARUSHIMA Yoshiro, NODA Nobuaki, NOTAKE Takashi, OBUCHI Takashil, OHDACHI Satoshi, OHYABU Nobuyoshi, OKA Yoshihide, OSAKABE Masaki, OZAKI Tetsuo, PETERSON Byron J., SAGARA Akio, SAITO Kenji, SAKAKIBARA Satoru, SAKAMOTO Ryuichi, SASAO Hajime, SASAO Mamiko, SATO Kuninori, SATO Motoyasu, SEKI Tetsuo, SHIMOZUMA Takashi, SHOJI Mamoru, SUZUKI Hajime, TAKAYAMA Arimichi, TAKEIRI Yasuhiko, TANAKA Kenji, TANAKA Naoki, TOI Kazuo, TOKUZAWA Tokihiko, TORII Yuki, TSUMORI Katsuyoshi, WATANABE Kiyomasa, WATARI Tetsuo, YAMADA Hiroshi, YAMADA Ichihiro, YAMAGUCHI Satarou, YAMAMOTO Satoru, YOKOYAMA Masayuki, YOSHIMURA Yasuo and MOTOJIMA Osamu, Electric Field Measurement and Limiter Experiment on LHD, JOURNAL OF NUCLEAR MATERIALS, 4.0, 106.0-110.0, 2001.01.
466. H Idei, S Kubo, T Shimozuma, M Sato, K Ohkubo, Y Yoshimura, Y Takita, S Kobayashi, S Ito, Y Mizuno, K Tsumori, K Ikeda, T Notake, T Watari, O Kaneko, A Komori, H Yamada, PC de Vries, M Goto, K Ida, S Inagaki, S Kado, K Kawahata, T Kobuchi, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, Y Nagayama, H Nakanishi, K Narihara, BJ Peterson, S Sakakibara, H Sasao, K Sato, K Tanaka, Y Takeiri, KY Watanabe, I Yamada, O Motojima, M Fujiwara, Electron cyclotron heating scenario and experimental results in LHD, FUSION ENGINEERING AND DESIGN, 53.0, 1.0, 329.0-336.0, 2001.01.
467. H. Yamada, A. Komori, N. Ohyabu, O. Kaneko, K. Kawahata, K. Y. Watanabe, S. Sakakibara, S. Murakami, K. Ida, R. Sakamoto, Y. Liang, J. Miyazawa, K. Tanaka, Y. Narushima, S. Morita, S. Masuzaki, T. Morisaki, N. Ashikawa, L. R. Baylor, W. A. Cooper, M. Emoto, P. W. Fisher, H. Funaba, M. Goto, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, K. Khlopenkov, T. Kobuchi, A. Kostrioukov, S. Kubo, T. Kuroda, R. Kumazawa, T. Minami, S. Muto, T. Mutoh, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, G. Rewoldt, A. Sagara, K. Saito, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, H. Sugama, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Watanabe, I. Yamada, S. Yamamoto, M. Yokoyama, Y. Yoshimura, T. Watari, Y. Xu, K. Itoh, K. Matsuoka, K. Ohkubo, T. Satow, S. Sudo, T. Uda, K. Yamazaki, O. Motojima, M. Fujiwara, Configuration flexibility and extended regimes in Large Helical Device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/43/12A/305, 43, 12A, 2001.01, [URL], Recent experimental results in the Large Helical Device have indicated that a large pressure gradient can be formed beyond the stability criterion for the Mercier (high-n) mode. While the stability against an interchange mode is violated in the inward-shifted configuration due to an enhancement of the magnetic hill, the neoclassical transport and confinement of high-energy particle are, in contrast, improved by this inward shift. Mitigation of the unfavourable effects of MHD instability has led to a significant extension of the operational regime. Achievements of the stored energy of 1 MJ and the volume-averaged beta of 3% are representative results from this finding. A confinement enhancement factor above the international stellarator scaling ISS95 is also maintained around 1.5 towards a volume-averaged beta, 〈β〉, of 3%. Configuration studies on confinement and MHD characteristics emphasize the superiority of the inward-shifted geometry to other geometries. The emergence of coherent modes appears to be consistent with the linear ideal MHD theory; however, the inward-shifted configuration has reduced heat transport in spite of a larger amplitude of magnetic fluctuation than the outward-shifted configuration. While neoclassical helical ripple transport becomes visible for the outward-shifted configuration in the collisionless regime, the inward-shifted configuration does not show any degradation of confinement deep in the collisionless regime (v* < 0.1). The distinguished characteristics observed in the inward-shifted configuration help in creating a new perspective of MHD stability and related transport in net current-free plasmas. The first result of the pellet launching at different locations is also reported..
468. T. Shimozuma, S. Kubo, M. Sato, Hiroshi Idei, Y. Takita, S. Ito, S. Kobayashi, Y. Mizuno, Y. Yoshimura, K. Ohkubo, H. Funaba, Inagaki Shigeru, T. Kobuchi, S. Masuzaki, S. Muto, M. Shoji, H. Suzuki, N. Noda, Y. Nakamura, K. Kawahata, N. Ohyabu, O. Motojima, ECH system and its application to long pulse discharge in large helical device, Fusion Engineering and Design, 10.1016/S0920-3796(00)00529-9, 53, 1-4, 525-536, 2001.01, [URL], We have developed and constructed an ECH system for the large helical device (LHD). The ECH system consists of 0.5 MW, 84 GHz range and 168 GHz gyrotrons, high voltage power supplies, long distance transmission lines, and in-vessel quasi-optical antennas. It has been improved step by step. At the third campaign of LHD experiments, three 84 GHz range (two 82.6 GHz and one 84 GHz) and three 168 GHz gyrotrons are operated and ECH power can be injected from four antennas vertically and two horizontally. This complicated system is remotely controlled and monitored by fully GUI (Graphical User Interface) control panels realized on PC via TCP (transmission control protocol) communication. Over 10 000 shots of gyrotron power have been injected steadily into the LHD during the experimental campaigns on this system. One line of the system (84 GHz line) is specially prepared for the experiments of steady state plasma production. Using this line, plasma sustainment for 2 min was successfully achieved by only ECH power. Injected ECH power was 50 kW with 95% duty factor. The electron density and temperature of the sustained plasma are measured to be 0.3-0.5 × 1018 m-3 and ∼650 eV. Ion temperature measured by Doppler broadening of the impurity radiation line was kept constant at ∼300 eV during RF injection..
469. Hiroshi Idei, S. Kubo, T. Shimozuma, M. Sato, K. Ohkubo, Y. Yoshimura, Y. Takita, S. Kobayashi, S. Ito, Y. Mizuno, K. Tsumori, K. Ikeda, T. Notake, T. Watari, O. Kaneko, A. Komori, H. Yamada, P. C. De Vries, M. Goto, K. Ida, Inagaki Shigeru, S. Kado, K. Kawahata, T. Kobuchi, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, Y. Nagayama, H. Nakanishi, K. Narihara, B. J. Peterson, S. Sakakibara, H. Sasao, K. Sato, K. Tanaka, Y. Takeiri, K. Y. Watanabe, I. Yamada, O. Motojima, M. Fujiwara, Electron cyclotron heating scenario and experimental results in LHD, Fusion Engineering and Design, 10.1016/S0920-3796(00)00505-6, 53, 1-4, 329-336, 2001.01, [URL], A large helical device (LHD) experiment began at the end of March 1998. Fundamental and second harmonic electron cyclotron heating (ECH) are used as a plasma production and heating method with six gyrotrons whose frequencies are 82.6/84 and 168 GHz, respectively. Up to 0.9 MW power has been injected in LHD with long distance corrugated waveguide transmission systems. The maximum pulse width is achieved to 3.0 s/240 kW for the LHD experiments. Six antenna systems have been prepared at the horizontally and vertically elongated poloidal sections. The maximum stored energy using all six gyrotrons is 70 kJ at the averaged density of n̄e = 4 × 1018 m-3. The maximum central electron temperature Te0 = 3.5 keV is achieved at n̄e = 3 × 1018 m-3. The magnetic field structure in heliotron type devices like LHD, notably near the coil, is complicated. For this oblique injection, a wave is launched from the antenna, and then crosses the plasma in the complex field structure near the coil. The polarization ellipse of the wave is changed along the ray-path. The wave propagation in heliotron type devices has been analyzed in an ideal case that the magnetic field component along the propagation direction can be neglected. Even for perpendicular injection with our antenna systems, the field component along the propagation direction is not so small. Another treatment of the wave-propagation is introduced. Some calculations for the heating scenario with this treatment are shown..
470. K. Narihara, K. Y. Watanabe, I. Yamada, T. Morisaki, K. Tanaka, S. Sakakibara, K. Ida, R. Sakamoto, N. Ohyabu, N. Ashikawa, M. Emoto, H. Funaba, M. Goto, H. Hayashi, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, O. Kaneko, K. Kawahata, T. Kobuchi, A. Komori, S. Kubo, R. Kumazawa, S. Masuzaki, J. Miyazawa, S. Morita, O. Motojima, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, Y. Oka, K. Ohkubo, M. Osakabe, S. Ozaki, B. J. Peterson, A. Sagara, K. Saito, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, C. Shoji, S. Sudo, H. Suzuki, A. Takayama, M. Takechi, Y. Takeiri, N. Tamura, K. Toi, N. Tokuzawa, Y. Torii, K. Tsumori, T. Watari, H. Yamada, S. Yamaguchi, S. Yamamoto, K. Yamazaki, Y. Yoshimura, Observation of the “self-healing” of an error field island in the large helical device, Physical Review Letters, 10.1103/PhysRevLett.87.135002, 87, 13, 2001.01, [URL], It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced..
471. K Kawahata, N Ohyabu, O Kaneko, A Komori, H Yamada, N Ashikawa, P deVries, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, K Khlopenkov, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, T Notake, T Kobuchi, Y Liang, S Ohdachi, Y Oka, M Osakabe, T Ozaki, R O Pavlichenko, B J Peterson, A Sagara, K Saito, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, M Takechi, Y Takeiri, N Tamura, K Tanaka, K Toi, T Tokuzawa, Y Torii, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, M Yokoyama, Y Yoshimura, K Y Watanabe, T Watari, K Itoh, K Matsuoka, K Ohkubo, I Ohtake, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, Y Hamada, O Motojima and M Fujiwara, Experimental studies on NBI and ICRF heated plasmas in the large helical device, PLASMA PHYSICS AND CONTROLLED FUSION, 42.0, 12B, Article No. B51, 2000.12.
472. T. Shimozuma, H. Idei, S. Kubo, T. Takita, S. Kobayashi, S. Ito, Y. Mizuno, M. Sato, K. Ohkubo, Y. Yoshimura, F. Leuterer, T. Notake, Y. Takeiri, K. Tsumori, K. Ikeda, M. Osakabe, Y. Oka, O. Kaneko, M. Emoto, H. Funaba, M. Goto, S. Inagaki, T. Kobuchi, S. Masuzaki, T. Minami, J. M, Performance of Electron Cyclotron Harmonic Heated Plasmas in Large Helical Device, The 27th EPS Conference on Controlled Fusion and Plasma Physics, vol.24B 1336-9, 2000.12.
473. T Mutoh, R Kumazawa, T Seki, T Watari, K Saito, Y Torii, DA Hartmann, Y Zhao, M Sasao, M Isobe, M Osakabe, AV Krasilnikov, T Ozaki, K Narihara, Y Nagayama, S Inagaki, F Shimpo, G Nomura, M Yokota, K Akaishi, N Ashikawa, P De Vries, M Emoto, H Funaba, A Fukuyama, M Goto, K Ida, H Idei, K Ikeda, N Inoue, K Itoh, O Kaneko, K Kawahata, S Kado, A Komori, T Kobuchi, S Kubo, S Masuzaki, T Morisaki, S Morita, J Miyazawa, S Murakami, T Minami, S Muto, Y Nakamura, H Nakanishi, N Noda, K Nishimura, K Ohkubo, N Ohyabu, S Ohdachi, Y Oka, H Okada, BJ Peterson, A Sagara, K Sato, S Sakakibara, R Sakamoto, H Sasao, M Sato, T Shimozuma, M Shoji, S Sudo, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, KY Watanabe, T Watanabe, H Yamada, I Yamada, S Yamaguchi, K Yamazaki, M Yokoyama, Y Yoshimura, Y Hamada, O Motojima, M Fujiwara, Ion Heating and high-energy-particle production by ion-cyclotron heating in the large helical device, Physical review letters, 85.0, 21.0, 4530.0, 2000.11.
474. A Komori, H Yamada, O Kaneko, N Ohyabu, K Kawahata, R Sakamoto, S Sakakibara, N Ashikawa, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, N Inoue, M Isobe, S Kado, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, T Kobuchi, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, K Saito, A Sagara, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, M Takechi, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, I Yamada, S Yamaguchi, S Yamamoto, M Yokoyama, Y Yoshimura, KY Watanabe, T Watanabe, T Watari, Y Hamada, K Itoh, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, O Motojima, M Fujiwara, Overview of the large helical device, PLASMA PHYSICS AND CONTROLLED FUSION, Vol. 42, No. 11, Pages 1165, 2000.11.
475. T. Mutoh, R. Kumazawa, T. Seki, T. Watari, K. Saito, Y. Torii, D. A. Hartmann, Y. Zhao, M. Sasao, M. Isobe, M. Osakabe, A. V. Krasilnikov, T. Ozaki, K. Narihara, Y. Nagayama, S. Inagaki, F. Shimpo, G. Nomura, M. Yokota, K. Akaishi, N. Ashikawa, P. De Vries, M. Emoto, H. Funaba, A. Fukuyama, M. Goto, K. Ida, H. Idei, K. Ikeda, N. Inoue, K. Itoh, O. Kaneko, K. Kawahata, S. Kado, A. Komori, T. Kobuchi, S. Kubo, S. Masuzaki, T. Morisaki, S. Morita, J. Miyazawa, S. Murakami, T. Minami, S. Muto, Y. Nakamura, H. Nakanishi, N. Noda, K. Nishimura, K. Ohkubo, N. Ohyabu, S. Ohdachi, Y. Oka, H. Okada, B. J. Peterson, A. Sagara, K. Sato, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sato, T. Shimozuma, M. Shoji, S. Sudo, H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Y. Watanabe, T. Watanabe, H. Yamada, I. Yamada, S. Yamaguchi, K. Yamazaki, M. Yokoyama, Y. Yoshimura, Y. Hamada, O. Motojima, M. Fujiwara, Ion heating and high-energy-particle production by ion-cyclotron heating in the large helical device, Physical Review Letters, 10.1103/PhysRevLett.85.4530, 85, 21, 4530-4533, 2000.11, [URL], An efficient plasma heating and maintenance for more than one minute was achieved by ion cyclotron range of frequencies (ICRF) heating in the large helical device (LHD). Ions were mainly heated by waves and a high-energy ion tail was observed. These results were consistent with 1D full-wave-analysis-code calculation..
476. A. Komori, H. Yamada, O. Kaneko, N. Ohyabu, K. Kawahata, R. Sakamoto, S. Sakakibara, N. Ashikawa, P. C. DeVries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, S. Kado, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, K. Saito, A. Sagara, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, M. Takechi, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, K. Y. Watanabe, T. Watanabe, T. Watari, Y. Hamada, K. Itoh, K. Matsuoka, K. Murai, K. Ohkubo, I. Ohtake, M. Okamoto, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, O. Motojima, M. Fujiwara, Overview of the Large Helical Device, 12th International Stellarator Workshop
Plasma Physics and Controlled Fusion
, 10.1088/0741-3335/42/11/303, 42, 11, 1165-1177, 2000.11, [URL], The Large Helical Device (LHD) experiments have started after a construction period of eight years, and two experimental campaigns were performed in 1998. The magnetic field was raised up to 2.75 T at a magnetic axis position of 3.6. m at the end of the second campaign. In the third campaign, started in July in 1999, the plasma production with ECH of 0.9 MW and auxiliary heating with NBI of 3.5 MW have achieved an electron temperature of 3.5 keV and an ion temperature of 2.4 keV. The maximum stored energy has reached 0.75 MJ with an averaged electron density of 7.7×10
19
m
-3
by hydrogen pellet injection. The ICRF heating has sustained the plasma for longer than 2 s and the initial stored energy of the NBI target plasma has increased from 0.27 MJ to 0.335 MJ. The major characteristic of the LHD plasma is the formation of the temperature pedestal, which leads to some enhancement of energy confinement over the ISS95 scaling law. The confinement characteristic is gyro-Bohm and the maximum energy confinement has reached 0.28 s. The LHD has also shown its high potentiality for steady-state operation by realizing a 22 s discharge in the second campaign..
477. Ohkubo, K; Kubo, S; Idei, H; Shimozuma, T; Yoshimura, Y; Leuterer, F; Sato, M; Takita, Y; , Analysis of oversized sliding waveguide by mode matching and multi-mode network theory, International Journal of Infrared and Millimeter Waves, 21.0, 9.0, 1463.0-1477.0, 2000.09, Transmission and reflection coefficients of hybrid modes in the sliding waveguide are discussed on the basis of mode matching method and multi-mode network theory. It is confirmed that the decrease in power of < 0.2% at 84 GHz is obtained for 3 cm in gap..
478. K Toi, M Takechi, M Isobe, N Nakajima, M Osakabe, S Takagi, T Kondo, G Matsunaga, K Ohkuni, M Sasao, S Yamamoto, S Ohdachi, S Sakakibara, H Yamada, KY Watanabe, DS Darrow, A Fujisawa, M Goto, K Ida, H Idei, H Iguchi, S Lee, S Kado, S Kubo, O Kaneko, K Kawahata, K Matsuoka, T Minami, S Morita, O Motojima, K Narihara, S Nishimura, N Ohyabu, Y Oka, S Okamura, T Ozaki, K Sato, M Sato, A Shimizu, T Shimozuma, Y Takeiri, K Tanaka, T Tokuzawa, K Tsumori, I Yamada, Y Yoshimura, Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device, NUCLEAR FUSION, 40.0, 7.0, 1349.0, 2000.07.
479. K. Toi, M. Takechi, M. Isobe, N. Nakajima, M. Osakabe, S. Takagi, T. Kondo, G. Matsunaga, K. Ohkuni, M. Sasao, S. Yamamoto, S. Ohdachi, S. Sakakibara, H. Yamada, K. Y. Watanabe, D. S. Darrow, akihide fujisawa, M. Goto, K. Ida, Hiroshi Idei, H. Iguchi, S. Lee, S. Kado, S. Kubo, O. Kaneko, K. Kawahata, K. Matsuoka, T. Minami, S. Morita, O. Motojima, K. Narihara, S. Nishimura, N. Ohyabu, Y. Oka, S. Okamura, T. Ozaki, K. Sato, M. Sato, A. Shimizu, T. Shimozuma, Y. Takeiri, K. Tanaka, T. Tokuzawa, K. Tsumori, I. Yamada, Y. Yoshimura, Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device, Nuclear Fusion, 10.1088/0029-5515/40/7/306, 40, 7, 1349-1362, 2000.07, [URL], Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfven eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfven eigenmodes (TAEs) and global Alfven eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfven velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (Bt = 1.5 T)..
480. H. Yamada, R. Sakamoto, S. Sakakibara, S. Morita, K. Tanaka, K. Narihara, S. Masuzaki, K. Y.Watanabe, B. J.Peterson, M. Osakabe, S. Murakami, L. R.Baylor, S. K.Combs, M. Goto, K. Ida, H. Idei, O. Kaneko, K. Kawahata, A. Komori, S. Kubo, J. Miyazawa, H. Nakanishi, Y. Narushima, S. Ohdahi, N. Ohyabu, M. Shoji, K. Toi, T. Tokuzawa, K. Tsumori, LHD Experimental Group, Characteristics of Pellet Penetration and Related Performance Improvement in LHD, 27th EPS Conference on Contr. Fusion and Plasma Phys. Budapest, 12-16 June 2000 ECA, 24B, 1320.0-1323.0, 2000.06.
481. M Fujiwara, Y Takeiri, T Shimozuma, T Mutoh, Y Nakamura, S Yamada, S Sudo, K Kawahata, Y Oka, M Sato, N Noda, A Iiyoshi, K Adachi, K Akaishi, N Ashikawa, H Chikaraishi, PC De Vries, M Emoto, H Funaba, M Goto, K Ida, H Idei, K Ikeda, S Imagawa, S Inagaki, M Isobe, A Iwamoto, S Kado, O Kaneko, S Kitagawa, T Kobuchi, A Komori, S Kubo, Y Kubota, R Kumazawa, R Maekawa, S Masuzaki, T Minami, T Mito, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, Y Nagayama, H Nakanishi, K Narihara, A Nishimura, K Nishimura, A Nishizawa, S Ohdachi, N Ohyabu, M Osakabe, T Ozaki, BJ Peterson, K Saito, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, T Seki, M Shoji, H Sugama, H Suzuki, K Takahata, M Takeuchi, H Tamura, K Tanaka, K Toi, T Tokuzawa, K Tsumori, KY Watanabe, TH Watanabe, T Watari, H Yamada, I Yamada, S Yamaguchi, S Yamamoto, N Yanagi, M Yokoyama, Y Yoshimura, Y Hamada, K Itoh, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Tanahashi, K Yamazaki, O Motojima, Overview of long pulse operation in the Large Helical Device, NUCLEAR FUSION, Vol. 40, No. 6, Pages 1157, 2000.06.
482. Morisaki, T; Narihara, K; Yamada, I; Komori, A; Ohyabu, N; Goto, M; Kaneko, O; Idei, H; Kubo, S; Masuzaki, S; , Relationship between Edge Magnetic Field Structure and Density/Temperature Profiles in LHD Heliotron, 27th EPS Conference on Contr. Fusion and Plasma Phys. Budapest, 12-16 June 2000 ECA Vol. 24B (2000) 780-783, 24B, 780.0-783.0, 2000.06.
483. M. Fujiwara, Y. Takeiri, T. Shimozuma, T. Mutoh, Y. Nakamura, S. Yamada, S. Sudo, K. Kawahata, Y. Oka, M. Sato, N. Noda, A. Iiyoshi, K. Adachi, K. Akaishi, N. Ashikawa, H. Chikaraishi, P. C. De Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, K. Ikeda, S. Imagawa, Inagaki Shigeru, M. Isobe, A. Iwamoto, S. Kado, O. Kaneko, S. Kitagawa, T. Kobuchi, A. Komori, S. Kubo, Y. Kubota, R. Kumazawa, R. Maekawa, S. Masuzaki, T. Minami, T. Mito, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, Y. Nagayama, H. Nakanishi, K. Narihara, A. Nishimura, K. Nishimura, A. Nishizawa, S. Ohdachi, N. Ohyabu, M. Osakabe, T. Ozaki, B. J. Peterson, K. Saito, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, T. Seki, M. Shoji, H. Sugama, H. Suzuki, K. Takahata, M. Takeuchi, H. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Y. Watanabe, T. H. Watanabe, T. Watari, H. Yamada, I. Yamada, S. Yamaguchi, S. Yamamoto, N. Yanagi, M. Yokoyama, Y. Yoshimura, Y. Hamada, K. Itoh, K. Matsuoka, K. Murai, K. Ohkubo, I. Ohtake, M. Okamoto, S. Satoh, T. Satow, S. Tanahashi, K. Yamazaki, O. Motojima, Overview of long pulse operation in the Large Helical Device, Nuclear Fusion, 10.1088/0029-5515/40/6/313, 40, 6, 1157-1166, 2000.06, [URL], The Large Helical Device is the world's largest heliotron type helical system, with the plasma confining magnetic field being generated by only external superconducting coils. One of the main objectives of the LHD project is to sustain high temperature plasmas for a long time in steady state. The plasma vacuum vessel and the divertor are water cooled, and a heat load of 3 MW can be removed continuously. The NBI, ECH and ICRF heating systems, diagnostic instruments and data acquisition system are designed for long pulse operation. The present status of these systems and the recent experimental results of long pulse operation are reviewed. A steady state discharge with NBI was obtained for 35 s. The ECH discharge duration was extended to 120 s with a duty factor of 95%. Plasma sustainment by ICRF alone was achieved for 2 s. The performance of these long pulse operations is summarized..
484. N Ohyabu, A Fujisawa, N Ashikawa, M Emoto, H Funaba, M Goto, Y Hamada, H Iguchi, K Ida, K Itoh, M Isobe, H Idei, S Inagaki, N Inoue, K Ikeda, S Kado, S Kubo, R Kumazawa, K Khlopenkov, O Kaneko, K Kawahata, A Komori, T Kobuchi, S Lee, Y Liang, T Minami, J Miyazawa, S Masuzaki, K Matsuoka, T Morisaki, S Morita, S Murakami, T Mutoh, S Muto, K Narihara, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, S Nishimura, N Noda, I Nomura, T Notake, S Okamura, S Ohdachi, K Ohkubo, Y Oka, M Osakabe, T Ozaki, BJ Peterson, RO Pavlichenko, A Sagara, S Sakakibara, R Sakamoto, M Sasao, K Sato, H Sanuki, K Saito, M Sato, T Seki, A Shimizu, T Shimozuma, M Shoji, H Suzuki, S Sudo, H Sasao, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, M Takechi, N Tamura, Y Torii, I Yamada, H Yamada, S Yamaguchi, K Yamazaki, M Yokoyama, Y Yoshimura, S Yamamoto, KY Watanabe, T Watanabe, T Watari, O Motojima, M Fujiwara, Thermal transport barrier in heliotron-type devices (Large Helical Device and Compact Helical System), PHYSICS OF PLASMAS, 7.0, 5.0, 1802.0-1808.0, 2000.05.
485. N. Ohyabu, A. Fujisawa, N. Ashikawa, P. DeVries, M. Emoto, H. Funaba, M. Goto, Y. Hamada, H. Iguchi, K. Ida, K. Itoh, M. Isobe, H. Idei, S. Inagaki, N. Inoue, K. Ikeda, S. Kado, S. Kubo, R. Kumazawa, K. Khlopenkov, O. Kaneko, K. Kawahata, A. Komori, T. Kobuchi, S. Lee, Y. Liang, T. Minami, J. Miyazawa, S. Masuzaki, K. Matsuoka, T. Morisaki, S. Morita, S. Murakami, T. Mutoh, S. Muto, K. Narihara, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Nishimura, S. Nishimura, N. Noda, I. Nomura, T. Notake, S. Okamura, S. Ohdachi, K. Ohkubo, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, R. O. Pavlichenko, A. Sagara, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, H. Sanuki, K. Saito, M. Sato, T. Seki, A. Shimizu, T. Shimozuma, M. Shoji, H. Suzuki, S. Sudo, H. Sasao, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Tsuzuki, M. Takechi, N. Tamura, Y. Torii, I. Yamada, H. Yamada, S. Yamaguchi, K. Yamazaki, M. Yokoyama, Y. Yoshimura, S. Yamamoto, K. Y. Watanabe, T. Watanabe, T. Watari, O. Motojima, M. Fujiwara, Thermal transport barrier in heliotron-type devices (Large Helical Device and Compact Helical System), Physics of Plasmas, 7, 5 II, 1802-1808, 2000.05, In the discharges of the Large Helical Device [O. Motojima et al., Proceedings of the 16th Conference on Fusion Energy, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 3, p. 437], a significant enhancement of the energy confinement has been achieved with an edge thermal transport barrier, which exhibits a sharp gradient at the edge. Key features associated with the barrier are quite different from those seen in tokamaks (i) almost no change in particle (including impurity) transport, (ii) a gradual formation of the barrier, (iii) a very high ratio of the edge temperature to the average temperature, (iv) no edge relaxation phenomenon. In the electron cyclotron heating (ECH) heated discharges in the Compact Helical System [K. Matsuoka et al., in Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411], the internal electron transport barrier has been observed, which enhances the central electron temperature significantly. High shear of the radial electric field appears to suppress the turbulence in the core region and enhance the electron confinement there..
486. Takashi Shimozuma, Motoyasu Sato, Yasuyuki Takita, Satoshi Ito, Shin Kubo, Hiroshi Idei, Kunizo Ohkubo, Masaomi Shirasaka, Shigeyuki Morimoto, Development of a Forced Gas-Gooled Brewster window for High-Power, CW Millimeter Waves, JOURNAL OF NUCLEAR MATERIALS, 3.0, 363.0-367.0, 2000.04.
487. Takashi Mutoh, R Kumazawa, T Seki, K Saito, F Shimpo, G Nomura, T Watari, X Jikang, G Cattanei, H Okada, K Ohkubo, M Sato, S Kubo, T Shimozuma, H Idei, Y Yoshimura, O Kaneko, Y Takeiri, M Osakabe, Y Oka, K Tsumori, A Komori, H Yamada, KY Watanabe, S Sakakibara, M Shoji, R Sakamoto, S Inagaki, J Miyazawa, S Morita, K Tanaka, BJ Peterson, S Murakami, T Minami, S Ohdachi, S Kado, K Narihara, H Sasao, H Suzuki, K Kawahata, N Ohyabu, Y Nakamura, H Funaba, S Masuzaki, S Muto, K Sato, T Morisaki, S Sudo, Y Nagayama, T Watanabe, M Sasao, M Goto, I Yamada, T Tokuzawa, K Ida, N Noda, K Yamazaki, K Akaishi, A Sagara, K Nishimura, T Ozaki, K Toi, O Motojima, M Fujiwara, The first ICRF heating experiment in the large helical device, PLASMA PHYSICS AND CONTROLLED FUSION, Vol. 42, No. 3, Pages 265, 2000.03.
488. S. Murakami, U. Gasparino, H. Idei, S. Kubo, H. Maassberg, N. Marushchenko, N. Nakajima, M. Romé and M. Okamoto, 5-D simulation study of suprathermal electron transport in non-axisymmetric plasmas, NUCLEAR FUSION, 40.0, 3Y, 693.0, 2000.03, ECRH driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5-D phase space. Two different phases of the ECRH driven transport of suprathermal electrons can be seen. The first is a rapid convective phase due to the direct radial motion of trapped electrons and the second is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile in W7-AS is clarified. The ECRH driven flux is also evaluated and considered in relation to the `electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity, and thus the observed electron root feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. A possible scenario for this type of electron root is considered for the LHD plasma..
489. T. Mutoh, R. Kumazawa, T. Seki, K. Saito, F. Shimpo, G. Nomura, T. Watari, X. Jikang, G. Cattanei, H. Okada, K. Ohkubo, M. Sato, S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, O. Kaneko, Y. Takeiri, M. Osakabe, Y. Oka, K. Tsumori, A. Komori, H. Yamada, K. Y. Watanabe, S. Sakakibara, M. Shoji, R. Sakamoto, S. Inagaki, J. Miyazawa, S. Morita, K. Tanaka, B. J. Peterson, S. Murakami, T. Minami, S. Ohdachi, S. Kado, K. Narihara, H. Sasao, H. Suzuki, K. Kawahata, N. Ohyabu, Y. Nakamura, H. Funaba, S. Masuzaki, S. Muto, K. Sato, T. Morisaki, S. Sudo, Y. Nagayama, T. Watanabe, M. Sasao, M. Goto, I. Yamada, T. Tokuzawa, K. Ida, N. Noda, K. Yamazaki, K. Akaishi, A. Sagara, K. Nishimura, T. Ozaki, K. Toi, O. Motojima, M. Fujiwara, First ICRF heating experiment in the large helical device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/42/3/304, 42, 3, 265-274, 2000.03, [URL], The first experiment of the ion cyclotron range of frequencies (ICRF) heating in the Large Helical Device (LHD) was carried out at the end of 1998. The LHD is a large superconducting heliotron device and its first plasma was produced in March 1998. During the ICRF heating experiment, a maximum 300 kW/0.2 s of ICRF power was injected into the LHD plasma by using a pair of loop antennae. This paper reports on the installation of the loop antennae, the results of antenna coupling and the first heating experiments. The antennae are designed to operate in the steady state and to change their distance from the plasma by 0-15 cm. In the experiment, the antenna resistance coupled with the plasma was measured by changing the distance between the last closed flux surface and the launcher front from 9 cm to 5 cm. The resistance was almost doubled by decreasing the distance. The target plasma was produced by the second harmonic electron cyclotron heating (ECH) of 84 GHz gyrotrons at a magnetic field of 1.5 T and a low plasma electron density of less than 1 × 1019 m-3. Therefore, the low coupling resistance limited the maximum injected power to less than 300 kW. The heating efficiency and heating species were varied by the minority ion gas-puffing rate. The heating characteristics were compared with a one-dimensional full-wave analysis code, and the experimental results were consistent with wave damping analysis. For the optimum condition of the minority hydrogen gas-puff ratio, the plasma internal energy increased from 13 kJ to 26 kJ by almost the same power as the ECH power..
490. H Yamada, KY Watanabe, S Sakakibara, S Murakami, M Osakabe, O Kaneko, K Narihara, K Tanaka, K Ida, T Minami, M Goto, H Idei, S Inagaki, S Kado, K Kawahata, A Komori, S Kubo, J Miyazawa, T Morisaki, S Morita, H Nakanishi, S Ohdachi, N Ohyabu, Y Oka, BJ Peterson, R Sakamoto, M Shoji, H Suzuki, Y Takeiri, K Toi, T Tokuzawa, K Tsumori, I Yamada, K Ohkubo, S Sudo, K Yamazaki, O Motojima, M Fujiwara, Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device, Physical review letters, 84.0, 6.0, 1216.0, 2000.02.
491. Ozaki, T., Sudo, S., Shoji, M., Murakami, S., Kado, S., Ida, K., Narihara, K., Tanaka, K., Kobuchi, T., Nakanishi, H., Kojima, M., Ohdachi, S., Morita, S., Goto, M., Sasao, M., Khrashilinikov, A., Sakakibara, S., Peterson, B., Kaneko, O., Idei, H., Preliminary Results of the Neutral Particle Measurements in Large Helical Device, Journal of Plasma and Fusion Research SERIES, 3, 444-448, 2000.01.
492. Kumazawa, R., Mutoh, T., Seki, T., Watari, T., Saito, K., Torii, Y., Shimpo, F., Nomura, G., Yokota, M., Hartmann, D.A., Zhao, Y., Okada, H., Ohkubo, K., Sato, M., Kubo, S., Shimozuma,T., Idei, H., Yoshimura, Y., Notake, T., Takita, Y., Long Pulse ICRF Heating Experiment on the LHD, Journal of Plasma and Fusion Research SERIES, 3, 352-358, 2000.01.
493. Takeiri, Y., Noda, N., Nakamura, Y., Kawahata,K., Osakabe, M., Oka, Y., Kaneko, O., Tsumori, K., Ikeda, K., Ida, K., Kado, S., Sato, M., Mutoh, T., Shimozuma, T., Idei, H., Inagaki, S., Isobe, M., Kobuchi, T., Kubo, S., Kumazawa, R., Long Pulse Neutral-Beam-Heated Discharges in Large Helical Device, Journal of Plasma and Fusion Research SERIES, 3, 345-351, 2000.01.
494. Kobuchi,T., Sato, K., Noda, N., Emoto, M., Funaba, H., Goto, M., Ida, K., Idei, H., Inagaki, S., Inoue, N., Isobe, M., Kado, S., Kaneko, O., Kawahata, K., Komori, A., Kubo, S., Kumazawa, R., Masuzaki,S., Minami,T., Miyazawa, J., Impurity Emission Characteristics of Long Pulse Discharges in Large Helical Device, Journal of Plasma and Fusion Research SERIES, 3, 121-124, 2000.01.
495. N Ohyabu, K Narihara, H Funaba, T Morisaki, S Masuzaki, K Kawahata, A Komori, O Kaneko, H Yamada, M Emoto, M Goto, Y Hamada, K Ida, H Idei, S Inagaki, N Inoue, S Kado, S Kubo, R Kumazawa, T Minami, J Miyazawa, S Morita, S Murakami, T Mutoh, S Muto, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, N Noda, T Kobuchi, S Ohdachi, K Ohkubo, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, K Saito, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, S Sudo, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, I Yamada, S Yamaguchi, K Yamazaki, M Yokoyama, KY Watanabe, T Watari, O Motojima, Edge thermal transport barrier in LHD discharges, Physical review letters, 84.0, 1.0, 103.0, 2000.01.
496. H. Idei, S. Kubo, T. Shimozuma, K. Tsumori, Y. Takita, S. Kobayashi, S. Ito, Y. Mizuno, M. Sato, K. Ohkubo, Y. Yoshimura, F. Leuterer, T. Notake, T. Watari, P. C.de. Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, K. Ikeda, S. Inagaki, S. Kado, T. Kobuchi, R. Kumazawa, S. Masuzaki, T., Polarized Radiative Transfer of Electron Cyclotron Waves in Large Helical Device, The 27th EPS Conference on Controlled Fusion and Plasma Physics, vol.24B 400-3, 2000.01.
497. MOTOJIMA Osamu, OHYABU Nobuyoshi, KOMORI Akio, KANEKO Osamu, YAMADA Hiroshi, KAWAHATA Kazuo, ASHIKAWA NaoKoI, CHIKARAISHI HirotaKa, DEVRIES Peter, EMOTO MasahiKo, FUNABA Hisamichi, GOTO Motoshi, HAMAGUCHI Shinji, IDA Katsumi, IDEI Hiroshi, IMAGAWA Shinsaku, INAGAKI Shigeru, INOUE Noriyuki, IWAMOTO Akifumi, KADO Shinichiro, KITAGAWA Shiro, KUBO Shin, KUBOTA Yusuke, KUMAZAWA Ryuhei, MAEKAWA Ryuji, MASUZAKI Suguru, MINAMI Takashi, MITO Toshiyuki, MIYAZAWA Junichi, MORISAKI Tomohiro, MORITA Shigeru, MURAKAMI Sadayoshi, MUTO Sadatsugu, MUTOH Takashi, NAGAYAMA Yoshio, NAKAMURA Yukio, NAKANISHI Hideya, NARIHARA Kazumichi, NISHIMURA Arata, NISHIMURA Kiyohiko, NODA Nobuaki, KOBUCHI Takashir, OHDACHI Satoshi, OKA Yoshihide, OSAKABE Takeshi, OZAKI Tetsuo, PETERSON Byron, SAGARA Akio, SAITOH Kenji, SAKAKIBARA Satoru, SAKAMOTO Ryuichi, SASAO Hajimer, SASAO Mamiko, SATO Kuninori, SATO Motoyasu, SEKI Tetsuo, SHIMOZUMA Takashi, SHOJI lviamoru, SUZUKI Hajime, TAKAHATA Kazuya, TAKECHI Manabu, TAKEIRI Yasuhiko, TAMURA Hitoshi, TAMURA Naoki, TANAKA Kenji, TOI Kazuo, TOKUZAWA Tokihiko, TSUMORI Katsuyoshi, TSUZUKI Kazuhiro, YAMADA Ichihiro, YAMADA Syuichi, YAMAGUCHI Satarou, YAMAMOTO Satoshi, YANAGI Nagato, YOKOYAMA Masayuki, WATANABE Kiyomasa, WATARI Tetsuo, HAMADA Yasuji, ITOH Kimitaka, MATSUOKA Keisuke, MURAI Katsuji, OHKUBO Kunizo, SATOH Sadao, SATOW Takashi, SUDO Sigeru, TANAHASHI Shyugo, YAMAZAKI Kozo, OHTAKE Isao, AKIYAMA Ryuuichi, HABA Kiichiro, IIMA Masashi, KODAIRA Jun-ichi, TSUZUKI Tetsuya and FUJIWARA Masami, Progress in LHD Experiment, Journal of Plasma and Fusion Research, 3.0, 3.0-9.0, 2000.01, In the third campaign (O7.13.99-12.14.99), NBI (<4.2 MW), ICRH (<1.4 MW) and ECRH (<0.9 MW) were used to heat the plasma in LHD. The carbon tiles were installed as divertor plates, resulting in significant reduction in metal impurity concentration (Fe). The maximum field used in the experiment is 2.gT.IJpgrading of the key hardware systems led to (i) higher T" [T,(0) = 4.4keY atn"= J.J x 1018m-3 and Po6, = 1.8 Mwl, (ii) higher confinement [%= 0.3 s, Z"(0) = l.l keV at n"(0) = 6.5 x l0re m-3 and Po6, = 2.0 MWl, (iiD higher stored energy W, = 880 kJ, (iv) higher volume averaged B = 2.4Eo (at B = 1.3 T). The temperature pedestal enhances the confinement significantly (50Ea higher than the ISS95 scaling). The ICRH heating was found to be as efficient as NBI heating. Long pulse discharges (80 sec NBI shot, 68 sec ICRH shot) have been achieved without any technical difficulty..
498. S. Murakami, U. Gasparino, H. Idei, S. Kubo, H. Maassberg, N. Marushchenko, N. Nakajima, M. Romé, M. Okamoto, 5-D simulation study of suprathermal electron transport in non-axisymmetric plasmas, Nuclear Fusion, 10.1088/0029-5515/40/3Y/333, 40, SPEC. ISS. 3, 693-700, 2000.01, [URL], ECRH driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5-D phase space. Two different phases of the ECRH driven transport of suprathermal electrons can be seen. The first is a rapid convective phase due to the direct radial motion of trapped electrons and the second is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile in W7-AS is clarified. The ECRH driven flux is also evaluated and considered in relation to the `electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity, and thus the observed electron root feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. A possible scenario for this type of electron root is considered for the LHD plasma..
499. K. Ohkubo, S. Kubo, Hiroshi Idei, T. Shimozuma, Y. Yoshimura, F. Leuterer, M. Sato, Y. Takita, Analysis of oversized sliding waveguide by mode matching and multi-mode network theory, International Journal of Infrared and Millimeter Waves, 10.1023/A:1026461125089, 21, 9, 1463-1477, 2000.01, [URL], Transmission and reflection coefficients of hybrid modes in the sliding waveguide are discussed on the basis of mode matching method and multi-mode network theory. It is confirmed that the decrease in power of <0.2% at 84 GHz is obtained for 2 cm in gap of the sliding waveguide which is composed of the corrugated waveguide with 88.9 mmφ and the smooth-wall waveguide with 110 mmφ. At the sliding length near multi-half-wavelength in vacuum, transmission and reflection powers in the sliding waveguide change slightly, because the very small amount of standing wave in high higher-mode is produced resonantly in the gap..
500. N. Ohyabu, K. Narihara, H. Funaba, T. Morisaki, S. Masuzaki, K. Kawahata, A. Komori, O. Kaneko, H. Yamada, P. de Vries, M. Emoto, M. Goto, Y. Hamada, K. Ida, H. Idei, S. Inagaki, N. Inoue, S. Kado, S. Kubo, R. Kumazawa, T. Minami, J. Miyazawa, S. Morita, S. Murakami, T. Mutoh, S. Muto, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, K. Ohkubo, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, K. Saito, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, S. Sudo, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Tsuzuki, I. Yamada, S. Yamaguchi, K. Yamazaki, M. Yokoyama, K. Y. Watanabe, T. Watari, O. Motojima, Edge thermal transport barrier in LHD discharges, Physical Review Letters, 10.1103/PhysRevLett.84.103, 84, 1, 103-106, 2000.01, [URL], In LHD discharges a significant enhancement of the global energy confinement has been achieved for the first time in a helical device with an edge thermal barrier, which exhibits a sharp gradient at the edge of the temperature profile. Key features associated with the barrier are quite different from those seen in tokamaks: (i) almost no change in particle (including impurity) transport, (ii) a gradual formation of the barrier, (iii) a very high ratio of the edge temperature to the average temperature, and (iv) no edge relaxation phenomenon. These features are very attractive in applying the thermal barrier to future reactor grade devices..
501. H. Yamada, K. Y. Watanabe, S. Sakakibara, S. Murakami, M. Osakabe, O. Kaneko, K. Narihara, K. Tanaka, K. Ida, T. Minami, M. Goto, H. Idei, S. Inagaki, S. Kado, K. Kawahata, A. Komori, S. Kubo, J. Miyazawa, T. Morisaki, S. Morita, H. Nakanishi, S. Ohdachi, N. Ohyabu, Y. Oka, B. J. Peterson, R. Sakamoto, M. Shoji, H. Suzuki, Y. Takeiri, K. Toi, T. Tokuzawa, T. Tsumori, I. Yamada, K. Ohkubo, S. Sudo, K. Yamazaki, O. Motojima, M. Fujiwara, Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device, Physical Review Letters, 10.1103/PhysRevLett.84.1216, 84, 6, 1216-1219, 2000.01, [URL], The confinement characteristics of large net-current-free plasmas heated by neutral-beam injection have been investigated in the Large Helical Device (LHD). A systematic enhancement in energy-confinement times from the scaling derived from the medium-sized heliotron/torsatron experiments have been observed, which is attributed to the edge pedestal. The core confinement is scaled with the Bohm term divided by the square root of the gyro radii. The comparative analysis using a dimensionally similar discharge in the Compact Helical System indicates gyro-Bohm dependence in the core and transport improvement in the edge region of LHD plasmas..
502. K. Kawahata, N. Ohyabu, O. Kaneko, A. Komori, H. Yamada, N. Ashikawa, P. De Vries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, K. Ikeda, Inagaki Shigeru, N. Inoue, M. Isobe, S. Kado, K. Khlopenkov, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, T. Kobuchi, Y. Liang, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, R. O. Pavlichenko, B. J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, Y. Yoshimura, K. Y. Watanabe, T. Watari, K. Itoh, K. Matsuoka, K. Ohkubo, I. Ohtake, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, Y. Hamada, O. Motojima, M. Fujiwara, Experimental studies on NBI and ICRF heated plasmas in the large helical device, 27th European Physical Society Conference on Controlled Fusion and Plasma Physics
Plasma Physics and Controlled Fusion
, 10.1088/0741-3335/42/12B/305, 42, 12 SUPPL. B, 2000.01, [URL], In the Large Helical Device (LHD), upgrading of the key hardware system since the last EPS conference has led to (1) higher Te (Te(0) = 4.4 keV at 〈ne〉 = 5.3×1018 m-3 and Pabs = 1.8 MW); (2) higher confinement (τE = 0.3 s, Te(0) = 1.1 keV at 〈ne〉 = 6.5×1019 m-3 and Pabs = 2.0 MW); (3) higher stored energy Wpdia = 880 kJ; and (4) the highest β value in helical devices (2.4% at B = 1.3 T). The energy confinement was systematically higher than that predicted by the International Stellarator Scaling 95 up to a factor of 1.6. Ion cyclotron range of frequencies (ICRF) power up to 1.3 MW was reliably injected into the plasma without significant impurity contamination and a plasma with stored energy of 200 kJ was sustained for 5 s by ICRF alone. Long pulse discharges greater than 1 min in duration have been successfully achieved with ICRF power alone and with neutral beam injection (NBI) power alone. With NBI heating an 80 s discharge was achieved with a heating power of 0.5 MW at 2.75 T. The electron density was maintained at around 1.6×1019 m-3 by controlled gas puffing. The central electron and ion temperatures were kept around 1.5 keV. With ICRF heating, a similar long pulse discharge was achieved for 68 s with a heating power of 0.85 MW. The sustained plasma parameters are: Wp approximately 110 kJ, Te(0) approximately Ti(0) = 2.0 keV and 〈ne〉 = 1.0×1019 m-3. During these discharges, no increase in radiation power has been observed..
503. M Fujiwara, O Kaneko, A Komori, H Yamada, N Ohyabu, K Kawahata, M Emoto, H Funaba, M Goto, K Ida, H Idei, S Inagaki, N Inoue, S Kado, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, T Kobuchi, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sahkibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, I Yamada, S Yamaguchi, M Yokoyama, KY Watanabe, T Watari, Y Hamada, K Itoh, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, O Motojima, A Iiyoshi, Experiments on NBI plasmas in LHD, PLASMA PHYSICS AND CONTROLLED FUSION, 44.0, 15B, B160, Vol. 41, No. 12B, Pages B157, 1999.12.
504. K. Toi, M. Takechi, S. Takagi, G. Matsunaga, M. Isobe, T. Kondo, M. Sasao, D. S. Darrow, K. Ohkuni, S. Ohdachi, R. Akiyama, A. Fujisawa, M. Gotoh, K. Ida, H. Idei, H. Iguchi, S. Kado, M. Kojima, S. Kubo, S. Lee, K. Matsuoka, T. Minami, S. Morita, N. Nikai, S. Nishimura, S. Okamura, M. Osakabe, A. Shimizu, Y. Shirai, C. Takahashi, K. Tanaka, T. Watari, Y. Yoshimura, Global MHD modes excited by energetic ions in heliotron/torsatron plasmas, Nuclear Fusion, 10.1088/0029-5515/39/11Y/336, 39, Special Issu, 1929-1933, 1999.12, [URL], Fishbone-like burst modes (FBs) and toroidal Alfven eigenmodes (TAEs) excited by energetic ions were observed for the first time in CHS heliotron/torsatron plasmas heated by co-injected neutral beams, where the rotational transform is increased by the induced beam driven current. FBs of m = 3/n = 2 (where m, n are the poloidal and toroidal mode numbers) induce a pulsed increase in the energetic ion loss flux. FBs of m = 2/n = 1 induce sawtooth oscillations in the latter half of a discharge where the plasma β becomes high. Only when the beam velocity exceeds about half of the central Alfven velocity and the net plasma current is induced to the required level are TAEs with n = 1 and n = 2 excited; these are localized in the plasma core region, where the magnetic shear is appreciably reduced by the net plasma current. So far, TAE induced energetic ion loss has not been observed..
505. M. Fujiwara, H. Yamada, A. Ejiri, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, S. Inagaki, S. Kado, O. Kaneko, K. Kawahata, T. Kobuchi, A. Komori, S. Kubo, Plasma confinement studies in LHD, Nuclear Fusion, 10.1088/0029-5515/39/11Y/305, 39, Special Issu, 1659-1666, 1999.12, [URL], The initial experiments on the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R = 3.9 m, a = 0.6 m). Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8×1018m-3·keV·s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and an ion temperature of 1.1 keV were achieved simultaneously at a line averaged electron density of 1.5×1019m-3. The maximum stored energy reached 0.22 MJ with neither unexpected confinement deterioration nor visible MHD instabilities, which corresponds to 〈β〉 = 0.7%. Energy confinement times reached a maximum of 0.17 s. A favourable dependence of energy confinement time on density remains in the present power density (approximately 40 kW/m3) and electron density (3×1019m-3) regimes, unlike the L mode in tokamaks. Although power degradation and significant density dependence are similar to the conditions on existing medium sized helical devices, the absolute value is enhanced by up to about 50% from the International Stellarator Scaling 95. Temperatures of both electrons and ions as high as 200 eV were observed at the outermost flux surface, which indicates a qualitative jump in performance compared with that of helical devices to date. Spontaneously generated toroidal currents indicate agreement with the physical picture of neoclassical bootstrap currents. Change of magnetic configuration due to the finite β effect was well described by 3-D MHD equilibrium analysis. A density pump-out phenomenon was observed in hydrogen discharges, which was mitigated in helium discharges with high recycling..
506. K. Ida, M. Osakabe, K. Tanaka, T. Minami, S. Nishimura, S. Okamura, A. Fujisawa, K. Yamazaki, Y. Yoshimura, S. Kubo, R. Akiyama, D. S. Darrow, H. Idei, H. Iguchi, M. Isobe, S. Kado, T. Kondo, S. Lee, K. Matsuoka, S. Morita, I. Nomura, S. Ohdachi, M. Sasao, A. Shimizu, S. Takagi, C. Takahashi, S. Takayama, M. Takechi, K. Toi, K. Tsumori, T. Watari, Transition from L mode to high ion temperature mode in CHS heliotron/torsatron plasmas, Nuclear Fusion, 10.1088/0029-5515/39/11Y/304, 39, Special Issu, 1649-1658, 1999.12, [URL], A high ion temperature (Ti) mode is observed for neutral beam heated plasmas in the Compact Helical System (CHS) heliotron/torsatron. The high Ti mode plasma is characterized by a high central ion temperature, Ti(O), and is associated with a peaked electron density profile produced by neutral beam fuelling with low wall recycling. Transition from L mode to high Ti mode has been studied in CHS. Ti(0) in the high Ti mode discharges reaches 1 keV, which is 2.5 times higher than that in the L mode discharges. The ion thermal diffusivity is significantly reduced by a factor of more than 2-3 in the high Ti mode plasma. The ion loss cone is observed in neutral particle flux in the energy range 1-6 keV with a narrow range of pitch angle (90°±20°) in the high Ti mode. However, the degradation of ion energy confinement due to this loss cone is negligible..
507. K Toi, M Takechi, S Takagi, G Matsunaga, M Isobe, T Kondo, M Sasao, DS Darrow, K Ohkuni, S Ohdachi, R Akiyama, A Fujisawa, M Gotoh, K Ida, H Idei, H Iguchi, S Kado, M Kojima, S Kubo, S Lee, K Matsuoka, T Minami, S Morita, N Nikai, S Nishimura, S Okamura, M Osakabe, A Shimizu, Y Shirai, C Takahashi, K Tanaka, T Watari, Y Yoshimura, Global MHD modes excited by energetic ions in heliotron/torsatron plasmas, NUCLEAR FUSION, 39.0, 11Y, 1929.0, 1999.11.
508. M Fujiwara, H Yamada, A Ejiri, M Emoto, H Funaba, M Goto, K Ida, H Idei, S Inagaki, S Kado, O Kaneko, K Kawahata, T Kobuchi, A Komori, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, S Ohdachi, N Ohyabu, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, KY Watanabe, T Watari, I Yamada, S Yamaguchi, M Yokoyama, R Akiyama, H Chikaraishi, K Haba, S Hamaguchi, M Iima, S Imagawa, N Inoue, K Iwamoto, S Kitagawa, J Kodaira, Y Kubota, R Maekawa, T Mito, T Nagasaka, A Nishimura, C Takahashi, K Takahata, Y Takita, H Tamura, T Tsuzuki, S Yamada, K Yamauchi, N Yanagi, H Yonezu, Y Hamada, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, O Motojima, A Iiyoshi, Plasma confinement studies in LHD, NUCLEAR FUSION, Vol. 39, No. 11Y, Pages 1659, 1999.11.
509. S Okamura, K Matsuoka, R Akiyama, DS Darrow, A Ejiri, A Fujisawa, M Fujiwara, M Goto, K Ida, H Idei, H Iguchi, N Inoue, M Isobe, K Itoh, S Kado, K Khlopenkov, T Kondo, S Kubo, A Lazaros, S Lee, G Matsunaga, T Minami, S Morita, S Murakami, N Nakajima, N Nikai, S Nishimura, I Nomura, S Ohdachi, K Ohkuni, M Osakabe, R Pavlichenko, BJ Peterson, R Sakamoto, H Sanuki, M Sasao, A Shimizu, Y Shirai, S Sudo, S Takagi, C Takahashi, S Takayama, M Takechi, K Tanaka, K Toi, T Watari, K Yamazaki, M Yokoyama, Y Yoshimura, Confinement physics study in a small low aspect ratio helical device: CHS, NUCLEAR FUSION, 39.0, 9Y, 1337.0, 1999.09.
510. Atsuo Iiyoshi, A Komori, A Ejiri, M Emoto, H Funaba, M Goto, K Ida, H Idei, S Inagaki, S Kado, O Kaneko, K Kawahata, T Kobuchi, S Kubo, R Kumazawa, S Masuzaki, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, S Ohdachi, N Ohyabu, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, KY Watanabe, T Watari, H Yamada, I Yamada, S Yamaguchi, M Yokoyama, R Akiyama, H Chikaraishi, K Haba, S Hamaguchi, M Iima, S Imagawa, N Inoue, K Iwamoto, S Kitagawa, J Kodaira, Y Kubota, R Maekawa, T Mito, T Nagasaka, A Nishimura, C Takahashi, K Takahata, Y Takita, H Tamura, T Tsuzuki, S Yamada, K Yamauchi, N Yanagi, H Yonezu, Y Hamada, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, M Fujiwara, O Motojima, Overview of the large helical device project, NUCLEAR FUSION, Vol. 39, No. 9Y, Pages 1245, 1999.09.
511. S. Kubo, R. Kumazawa, T. Shimozuma, H. Idei, Y. Yoshimura, M. Sato, T. Mutoh, T. Seki, T. Watari, K. Ohkubo, K. Saito, Y. Takita, S. Kobayashi, S. Ito, Y. Mizuno, F. Shinpo, G. Nomura, O. Kaneko, A. Komori, H. Yamada, N. Ohyabu, K. Kawahata, K. Akaishi, M. Emoto, H. Funaba, M. Goto, Y. Hamada, K. Ida, S. Inagaki, N. Inoue, S. Kado, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Shoji, S. Sudo, H. Suzuki, T. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Tsuzuki, I. Yamada, S. Yamaguchi, K. Yamazaki, M. Yokoyama, K. Y. Watanabe, O. Motojima, M. FujiwaraandA. Iiyoshi, RF experiments in LHD, The thirteenth topical conference on radio frequency power in plasmas, 485.0, 1.0, 237.0-244.0, AIP Publishing, 1999. p. 237-244., 1999.09.
512. S. Okamura, K. Matsuoka, R. Akiyama, D. S. Darrow, A. Ejiri, A. Fujisawa, M. Fujiwara, M. Goto, K. Ida, H. Idei, H. Iguchi, N. Inoue, M. Isobe, K. Itoh, S. Kado, al et al, Confinement physics study in a small low aspect ratio helical device
CHS, Nuclear Fusion, 39, Special Issue, 1337-1350, 1999.09, Variation of the plasma position relative to the centre of the helical coil winding is a very effective means of controlling the MHD stability and the trapped particle confinement in heliotron/torsatron systems, but improving one of these two characteristics with this parameter simultaneously has a detrimental effect on the other. The inward shifted configuration is favourable for drift orbit optimization but is predicted to be unstable according to the Mercier criterion. Various physics problems, such as electric field structure, plasma rotation and MHD phenomena, have been studied in the Compact Helical System (CHS) with a compromise intermediate position. With this standard configuration, CHS has yielded experimental results that contribute to the understanding of general toroidal confinement physics and low aspect ratio helical systems. In the recent experiments, it was found that a wide range of inward shifted configurations give stable plasma discharges without any restriction to the special pressure profile. Such an enhanced range of operation made it possible to study experimentally the drift orbit optimized configuration in heliotron/torsatron systems. The effect of configuration improvement was studied with plasmas in a low collisionality regime..
513. A. Iiyoshi, A. Komori, A. Ejiri, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, S. Inagaki, S. Kado, O. Kaneko, K. Kawahata, T. Kobuchi, S. Kubo, R. Kumazawa, al et al, Overview of the large helical device project, Nuclear Fusion, 39, Special Issue, 1245-1256, 1999.09, The Large Helical Device (LHD) has successfully started running plasma confinement experiments after a long construction period of eight years. During the construction and machine commissioning phases, a variety of milestones were attained in fusion engineering which successfully led to the first operation, and the first plasma was ignited on 31 March 1998. Two experimental campaigns were carried out in 1998. In the first campaign, the magnetic flux mapping clearly demonstrated a nested structure of magnetic surfaces. The first plasma experiments were conducted with second harmonic 84 and 82.6 GHz ECH at a heating power input of 0.35 MW. The magnetic field was set at 1.5 T in these campaigns so as to accumulate operational experience with the superconducting coils. In the second campaign, auxiliary heating with NBI at 3 MW has been carried out. Averaged electron densities of up to 6 × 1019 mMIN3, central temperatures ranging from 1.4 to 1.5 keV and stored energies of up to 0.22 MJ have been attained despite the fact that the impurity level has not yet been minimized. The obtained scaling of energy confinement time has been found to be consistent with the ISS95 scaling law with some enhancement..
514. Kumazawa, R., Mutoh, T., Seki, T., Saito, K., Shimpo, F., Nomura, G., Ido, T., Watari, T., Cattenei, G., Jikang, X., Okada, H., Ohkubo, K., Sato, M., Kubo, S., Shimozuma, T., Idei, H., Yoshimura, Y., Kaneko, O., Takeiri, Y., Oka, Y., Initial ICRF heating experiments on the LHD, AIP Conf. Proc., 485, 160-163, 1999.08.
515. Takechi, M; Toi, K; Takagi, S; Matsunaga, G; Ohkuni, K; Ohdachi, S; Akiyama, R; Darrow, DS; Fujisawa, A; Gotoh, M; Idei, H; Iguchi, H; Isobe, M; Kondo, T; Kojima, M; Kubo, S; Lee, S; Minami, T; Morita, S; Matsuoka, K; Nishimura, S; Okamura, S; Osakabe, M; Sasao, M; Shimizu, M; Takahashi, C; Tanaka, K; Yoshimura, Y, Energetic-ion-driven toroidal Alfven eigenmodes observed in a heliotron torsatron plasma, PHYSICAL REVIEW LETTERS, 83, 2, 312-315, 1999.07.
516. O Motojima, H Yamada, A Komori, N Ohyabu, K Kawahata, O Kaneko, S Masuzaki, A Ejiri, M Emoto, H Funaba, M Goto, K Ida, H Idei, S Inagaki, N Inoue, S Kado, S Kubo, R Kumazawa, T Minami, J Miyazawa, T Morisaki, S Morita, S Murakami, S Muto, T Mutoh, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, K Nishimura, N Noda, T Kobuchi, S Ohdachi, Y Oka, M Osakabe, T Ozaki, BJ Peterson, A Sagara, S Sakakibara, R Sakamoto, H Sasao, M Sasao, K Sato, M Sato, T Seki, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, I Yamada, S Yamaguchi, M Yokoyama, KY Watanabe, T Watari, Y Hamada, K Matsuoka, K Murai, K Ohkubo, I Ohtake, M Okamoto, S Satoh, T Satow, S Sudo, S Tanahashi, K Yamazaki, M Fujiwara, A Iiyoshi, Initial physics achievements of large helical device experiments, PHYSICS OF PLASMAS, 6.0, 5.0, 1845.0-1850.0, 1999.05.
517. O. Motojima, H. Yamada, A. Komori, N. Ohyabu, K. Kawahata, O. Kaneko, S. Masuzaki, A. Ejiri, M. Emoto, H. Funaba, M. Goto, K. Ida, H. Idei, S. Inagaki, N. Inoue, S. Kado, S. Kubo, R. Kumazawa, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, S. Sakakibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Tsuzuki, I. Yamada, S. Yamaguchi, M. Yokoyama, K. Y. Watanabe, T. Watari, Y. Hamada, K. Matsuoka, K. Murai, K. Ohkubo, I. Ohtake, M. Okamoto, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, M. Fujiwara, A. Iiyoshi, Initial physics achievements of large helical device experiments, Physics of Plasmas, 10.1063/1.873443, 6, 5 I, 1843-1850, 1999.05, [URL], The Large Helical Device (LHD) experiments [O. Motojima, et al., Proceedings, 16th Conference on Fusion Energy, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 3, p. 437] have started this year after a successful eight-year construction and test period of the fully superconducting facility. LHD investigates a variety of physics issues on large scale heliotron plasmas (R = 3.9 m, a = 0.6 m), which stimulates efforts to explore currentless and disruption-free steady plasmas under an optimized configuration. A magnetic field mapping has demonstrated the nested and healthy structure of magnetic surfaces, which indicates the successful completion of the physical design and the effectiveness of engineering quality control during the fabrication. Heating by 3 MW of neutral beam injection (NBI) has produced plasmas with a fusion triple product of 8 × 1018 keV m-3 s at a magnetic field of 1.5 T. An electron temperature of 1.5 keV and an ion temperature of 1.4 keV have been achieved. The maximum stored energy has reached 0.22 MJ, which corresponds to 〈β〉=0.7%, with neither unexpected confinement deterioration nor visible magnetohydrodynamics (MHD) instabilities. Energy confinement times, reaching 0.17 s at the maximum, have shown a trend similar to the present scaling law derived from the existing medium sized helical devices, but enhanced by 50%. The knowledge on transport, MHD, divertor, and long pulse operation, etc., are now rapidly increasing, which implies the successful progress of physics experiments on helical currentless-toroidal plasmas..
518. K Ida, M Osakabe, K Tanaka, T Minami, S Nishimura, S Okamura, A Fujisawa, K Yamazaki, Y Yoshimura, S Kubo, R Akiyama, DS Darrow, H Idei, H Iguchi, M Isobe, S Kado, T Kondo, S Lee, K Matsuoka, S Morita, I Nomura, S Ohdachi, M Sasao, A Shimizu, S Takagi, C Takahashi, S Takayama, M Takechi, K Toi, K Tsumori, T Watari, Transition from L mode to high ion temperature mode in CHS heliotron/torsatron plasmas, NUCLEAR FUSION, 39.0, 11Y, 1649.0, Vol. 39, No. 11Y, Pages 1649, 1999.04.
519. Fujisawa, A; Iguchi, H; Idei, H; Kubo, S; Matsuoka, K; Okamura, S; Tanaka, K; Minami, T; Ohdachi, S; Morita, S; Zushi, H; Lee, S; Osakabe, M; Akiyama, R; Yoshimura, Y; Toit, K; Sanuki, H; Itoh, K; Shimizu, A; Takagi, S; Ejiri, A; Takahashi, C; Kojima, M; Hidekuma, S; Ida, K; Nishimura, S; Isobe, M; Inoue, N; Sakamoto, R; Itoh, SI; Hamada, Y; Fujiwara, M, Electric pulsation and profile quantization in CHS heliotron/torsatron, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/41/3A/049, 41.0, 3A, A561, 1999.03, Radial electric field is a key physical quantity in determining the structure of toroidal helical plasmas, owing to the nonlinear dependence of transport on the, radial electric field. It has been observed that the potential profiles show various interesting patterns in space and time in the compact helical system (CHS) plasmas. In particular, the phenomenon of electric pulsation, clearly demonstrates the nature of bifurcation of radial electric field in toroidal helical plasmas..
520. B. J. Peterson, K. Y. Watanabe, M. Osakabe, R. Sakamoto, Y. Xu 1 , S. Sudo, H. Idei, S. Kado, S. Kubo, J. Miyazawa, S. Morita, K. Narihara, S. Sakakibara, K. Tanaka, T. Tokuzawa, K. Tsumori, H. Yamada, A. Komori, O. Kaneko, K. Kawahata, N. Ohyabu, O. Motojima, M. Fujiwara and LHD Experimental Groups I and II, Bolometric measurements of radiated power profiles from initial NBI heated plasmas in the Large Helical Device, 26th European Physical Society Conference on Controlled Fusion and Plasma Physics (Maastricht, 1999), 23.0, 1337.0-1340.0, 1999.01.
521. M. Takechi, K. Toi, S. Takagi, G. Matsunaga, K. Ohkuni, S. Ohdachi, R. Akiyama, D. S. Darrow, akihide fujisawa, M. Gotoh, Hiroshi Idei, H. Iguchi, M. Isobe, T. Kondo, M. Kojima, S. Kubo, S. Lee, T. Minami, S. Morita, K. Matsuoka, S. Nishimura, S. Okamura, M. Osakabe, M. Sasao, M. Shimizu, C. Takahashi, K. Tanaka, Y. Yoshimura, Energetic-ion-driven toroidal alfvén eigenmodes observed in a heliotron/torsatron plasma, Physical Review Letters, 10.1103/PhysRevLett.83.312, 83, 2, 312-315, 1999.01, [URL], Toroidal Alfvén eigenmodes (TAEs) of low toroidal mode number, n=1 and 2, are observed in neutral-beam-heated plasmas in the compact helical system heliotron/torsatron. The observed frequency is proportional to the computed TAE frequency and lies near the lower bound of the innermost TAE gap. The modes are excited only when the beam velocity exceeds about half the central Alfvén velocity and when the net plasma current induced by coinjected neutral beams is in the required range. The modes are localized in the plasma core region, between 0.2 and 0.6 of the plasma minor radius..
522. M. Fujiwara, O. Kaneko, A. Komori, H. Yamada, N. Ohyabu, K. Kawahata, P. C. DeVries, M. Emoto, H. Funaba, M. Goto, K. Ida, Hiroshi Idei, Inagaki Shigeru, N. Inoue, S. Kado, S. Kubo, R. Kumazawa, S. Masuzaki, T. Minami, J. Miyazawa, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, A. Sagara, S. Sahkibara, R. Sakamoto, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi, T. Tokuzawa, K. Tsumori, K. Tsuzuki, I. Yamada, S. Yamaguchi, M. Yokoyama, K. Y. Watanabe, T. Watari, Y. Hamada, K. Itoh, K. Matsuoka, K. Murai, K. Ohkubo, I. Ohtake, M. Okamoto, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, O. Motojima, A. Iiyoshi, Experiments on NBI plasmas in LHD, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/41/12B/311, 41, SUPPL. 12B, 1999.01, [URL], Neutral beam injection (NBI) heating started in the second experimental campaign of the Large Helical Device (September to December 1998) by two tangential beam lines. With 100 keV hydrogen, the beam port through power of up to 3.7 MW was injected for 1 s typically. The energy confinement was systematically better than that predicted by the International Stellerator Scaling 95 up to a factor of 1.5. The temperature pedestal observed contributes to this enhancement. We have also demonstrated a long pulse discharge by NBI in the LHD. By injecting 0.7 MW of beam, a plasma with a density of 0.3 × 1019 m-3 was sustained for 22 s. A unique oscillating phenomenon of plasma quantities with a long time scale was observed in the long pulse discharge. One of the topics of NB discharge is that the plasma can be started up by NB alone. This technique is unique for helical systems that have a vacuum magnetic field confining high energy ions, and it is useful for helical systems to be free from the constraint of magnetic field strength that must coincide with the frequency required by electron cyclotron resonance heating (ECH)..
523. FUJISAWA Akihide, IGUCHI Harukazu, IDEI Hiroshi, KUBO Shin, LEE Seishu, MATSUOKA Keisuke, OKAMURA Shoichi, TANAKA Kenji, MINAMI Takashi, MORITA Shigeru, OHDACHI Satoshi, OSAKABE Masaki, AKIYAMA Ryuichi, YOSHIMURA Yasuo, TOI Kazuo, SANUKI Heiji, ITOH Kimitaka, TAKAHASHI Chihiro, KOJIMA Mamoru, HIDEKUMA Shigeru, IDA Katsumi, NISHIMURA Shin, EIIRI Akira, HAMADA Yasushi, ITOH Sanae-L1, INOUE Noriyuki, SAKAMOTO Ryuichi and FUJMARA Masami, Electric field bifurcation and transition in CHS heliotron/torsatron, JOURNAL OF NUCLEAR MATERIALS, 1.0, 84.0-87.0, 1998.12, Transition in radial electric field has been observed in CHS plasmas during a combined heating phase of ECH+NBI, using a heavy ion beam probe. The transition occurs in a timescale of a few dozen or a hundred microseconds. Radial current to induce the transition is evaluated by high temporal resolution of the heavy ion beam probe. Neoclassical dependence of radial electric field on a plasma parameter will be discussed to clarify the nonlinearity to allow the transition..
524. U. Gasparino, H. Idei, S. Kubo, N. Marushchenko, M. Romé, High harmonic electron cyclotron resonance heating in the large helical device, Nuclear Fusion, 10.1088/0029-5515/38/2/306, 38, 2, 223-235, 1998.12, [URL], During the initial experimental phase, LHD, a stellarator of the heliotron/torsatron variety presently under construction, will operate at a magnetic field lower than the nominal one. In this scenario, the frequency of the available gyrotrons (chosen in view of second harmonic heating at full field operation) will be resonant with the third or the fourth harmonic of the electron gyrofrequency. The aim of this article is to analyse the electron cyclotron resonance heating (ECRH) at these high harmonics. By using linear absorption theory, together with transport predictions, good absorption is found over a wide density range for third harmonic heating. In the case of the fourth harmonic, the conditions for absorption are considerably more critical, but non-negligible heating (single pass absorption ≳10%) is expected in very low density, high temperature target plasmas. Owing to the strong temperature dependence of the absorption mechanism, heating at higher harmonics presents some peculiar characteristics. Quasi-linear effects are found to improve the absorption properties (as compared with those of linear theory), and bifurcation phenomena, as well as a critical power threshold, might appear. The physical origin and the consequences of these effects are discussed..
525. Takahashi, C., Akiyama, R., Inoue, T., Takami, S., Shimbo, F., Haba, K., Takita, Y., Asano, E., Nomura, G., Ito, S., Komoto, T., Taniguchi, Y., Ogawa, H., Yamamoto, N., Chikaraishi, H., Mutoh, T., Kubo, S., Idei, H., Takeiri, Y., Kaneko, O., Control and communication system for plasma heating unit and power supply system of large helical device, Symposium on fusion technology, 1998.10.
526. Fujisawa, A; Iguchi, H; Idei, H; Kubo, S; Matsuoka, K; Okamura, S; Tanaka, K; Minami, T; Ohdachi, S; Morita, S; Zushi, H; Lee, S; Osakabe, M; Akiyama, R; Yoshimura, Y; Toi, K; Sanuki, H; Itoh, K; Shimizu, A; Takagi, S; Ejiri, A; Takahashi, C; Kojima, M; Hidekuma, S; Ida, K; Nishimura, S; Isobe, M; Inoue, N; Sakamoto, R; Itoh, SI; Hamada, Y; Fujiwara, M, Discovery of electric pulsation in a toroidal helical plasma, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.81.2256, 81.0, 11.0, 2256.0-2259.0, 1998.09, A pulsating behavior of the electrostatic potential has been discovered in a low-density, high-electron-temperature plasma of the CHS heliotron/torsatron. The potential profiles were observed to swing repeatedly between two distinctive states in a constant external magnetic field under a continuous supply of particles and energy. The change of the potential profile, which occurs on a much faster time scale (microseconds) than the diffusive time scale (milliseconds), is accompanied by changes in density and temperature. This discovery clearly demonstrates that even in a low beta regime a toroidal helical plasma can produce a self-sustaining dynamic steady state, like the sawtooth oscillation in tokamaks..
527. U Gasparino, H Idei, S Kubo, N Marushchenko, M Rom, High harmonic electron cyclotron resonance heating in the Large Helical Device, NUCLEAR FUSION, 38.0, 2.0, 223.0, 1998.02, During the initial experimental phase, LHD, a stellarator of the heliotron/torsatron variety presently under construction, will operate at a magnetic field lower than the nominal one. In this scenario, the frequency of the available gyrotrons (chosen in view of second harmonic heating at full field operation) will be resonant with the third or the fourth harmonic of the electron gyrofrequency. The aim of this article is to analyse the electron cyclotron resonance heating (ECRH) at these high harmonics. By using linear absorption theory, together with transport predictions, good absorption is found over a wide density range for third harmonic heating. In the case of the fourth harmonic, the conditions for absorption are considerably more critical, but non-negligible heating (single pass absorption gtrsim 10%) is expected in very low density, high temperature target plasmas. Owing to the strong temperature dependence of the absorption mechanism, heating at higher harmonics presents some peculiar characteristics. Quasi-linear effects are found to improve the absorption properties (as compared with those of linear theory), and bifurcation phenomena, as well as a critical power threshold, might appear. The physical origin and the consequences of these effects are discussed..
528. Makoto Iwase, Shin Kubo, Hiroshi Idei, Kunizo Ohkubo, Takashi Minami, John Wilgen, Statistical estimation of power deposition profile in electron cyclotron heated plasmas, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 37, 2, 678-687, 1998.02, The power deposition profile by modulated fundamental electron cyclotron heating is deduced with the confidence interval derived from the statistical treatment of experimental data. The second harmonic electron cyclotron emission is used for the measurement of electron temperature that is necessary in this analysis. It is shown that the resultant deposition profile is consistent with the prediction resulting from the ray tracing calculation, including the multireflection effect at the vessel wall. The local adiabatic time scale for the thermal diffusion is derived and the propriety of the time scale in the power balance analysis is confirmed. The statistical confidence interval implies a broad profile of the power absorption. The obtained results show the necessity of using the statistical approach for analysis of the experimental data..
529. Peterson, BJ; Sudo, S; Sato, M; Kawahata, K; Morita, S; Sakakibara, S; Kubo, S; Idei, H; Shimozuma, T; Tanaka, K; , Bolometric Measurements of ECH Produced Plasmas in the Large Helical Device, APS Division of Plasma Physics Meeting Abstracts, 1.0, 1998.01.
530. KUBO Shin. OSAKABE Masaki, IDEI Hiroshi, KANEKO Osamu, TSUMORI Katsuyoshi, YOSHIMURA Yasuo, IDA Katsumi, NISHIMURA Shinl, TANAKA Kenji, OKAMURA Shoichi, SHIMIZU Akihiro, MINAMI Takashi, ISOBE Mitsutaka, KONDO Takashil, SASAO Mamiko, DARROW, Douglass S., MORITA Shigeru, TAKECHI Manabu2, TAKAGI Shoji, OHDACHI Satoshi, TOI Kazuo, TAKAHASHI Chihiro, AKIYAMA Ryuichi' INOUE Noriyuki, SAKAMOTO Ryuichi, WATARI Tetsuo and MATSUOKA Keisuke , High power EC and NB heating experiments in CHS, Journal of Plasa Fusion Research SERIES, 1.0, 118.0-121.0, 1998.01.
531. Iwase, Makoto; Kubo, Shin; Idei, Hiroshi; Ohkubo, Kunizo; Minami, Takashi; Wilgen, John; , Statistical estimation of power deposition profile in electron cyclotron heated plasmas, JAPANESE JOURNAL OF APPLIED PHYSICS, Vol. 37, No. 2R, Pages 678, 1998.01.
532. Morisaki, T; Komori, A; Akiyama, R; Idei, H; Iguchi, H; Inoue, N; Kawai, Y; Kubo, S; Masuzaki, S; Matsuoka, K; Minami, T; Morita, S; Noda, N; Ohyabu, N; Okamura, S; Osakabe, M; Suzuki, H; Tanaka, K; Takahashi, C; Yamada, H; Yamada, I; Motojima, O, Experimental study of edge plasma structure in various discharges on compact helical system, JOURNAL OF NUCLEAR MATERIALS, 10.1016/S0022-3115(97)80177-8, 241.0, 977.0-981.0, 1997.11, Precise measurements of edge density profiles in various discharges have been performed successfully in the compact helical system (CHS) with a thermal neutral lithium beam probe. During high beta discharges, an outward shift of the plasma edge boundary was observed with an increase in the beta value, which was found to agree qualitatively with theoretical calculations. Experiments with different magnetic field configurations, i.e., with Limiter, divertor and with an m/n = 1/1 island, were also performed. Clear difference in the edge density profiles among the configurations and a large change of plasma parameters in the configuration with the m/n = 1/1 island were observed..
533. Takahashi, C. ; Akiyama, R. ; Shimbo, F. ; Haba, K. ; Takita, Y. ; Asano, E. ; Nomura, G. ; Ito, S. ; Kohmoto, T. ; Taniguchi, Y. ; Ogawa, H. ; Yamamoto, N. ; Mutoh, T. ; Kubo, S. ; Idei, H. ; Takeiri, Y. ; Kaneko, O. ; Watanabe, K. ; Yamada, H. ; Yamazaki, K. ; Murai, K. ; Motojima, O. ; Watari, T., Control and communication system for plasma heating unit of Large Helical Device, Fusion Engineering, 1997. 17th IEEE/NPSS Symposium, 1.0, 509.0-512.0, 1997.10, Development of the control and communication system for the plasma heating unit of Large Helical Device (LHD: an experimental machine for fusion science) has been continued. The system is composed of a distributed and concurrent client/server system by the use of several UNIX workstations, and its sub-systems are controlled by PLC (Programmable Logic Controller), VME (Versa Module Europe). Almost all of its control system are connected via Ethernet with IEEE802.3. Man-machine interface system and hardware/software of the control system have been completed.
534. Kubo, Shin; Osakabe, Masaki; Idei, Hiroshi, High power EC and NB heating experiments in CHS, ITC-8: 8. international Toki conference on plasma physics and controlled nuclear fusion; Toki, Gifu (Japan); Toki, Gifu (Japan); 29 Sep - 3 Oct 1997; 29 Sep - 3 Oct 1997, 1997.10.
535. Shimozuma, T; Sato, M; Takita, Y; Ito, S; Kubo, S; Idei, H; Ohkubo, K; Watari, T; Chu, TS; Felch, K; , The First Preliminary Experiments on an 84 GHz Gyrotron with a Single-Stage Depressed Collector, NIFS-513 , 1997.10.
536. T. Shimozuma, S. Morimoto, M. Sato, Y. Takita, S. Ito, S. Kubo, H. Idei, K. Ohkubo, T. Watari, A forced gas-cooled single-disk window using silicon nitride composite for high power CW millimeter waves, International Journal of Infrared and Millimeter Waves, 18.0, 8.0, 1479.0-1493.0, 1997.08, Silicon nitride composite as a candidate of a window material for high power CW (Continuous Wave) millimeter-waves was high power tested especially with a surface cooling by impinging gas nitrogen jets on the single-disk surface. Gas-cooling dramatically suppressed the temperature of the window disk even with gas flow rate of around 100 l/min. With gas cooling of 465l/min., 130kW CW power of HE11 mode could be transmitted through the silicon nitride window with a diameter of 88.9mm. The peak window temperature was completely saturated on 123.6 °C. Without gas-cooling it did not saturate and reached 323 °C during 30 seconds pulse. A possibility of 1MW CW single disk Brewster windows with a forced gas-cooling is discussed, resulting in convinced prospects of the windows with realistic size and thickness..
537. Fujisawa, A; Iguchi, H; Sanuki, H; Itoh, K; Lee, S; Hamada, Y; Kubo, S; Idei, H; Crowley, TP; Akiyama, R; Tanaka, K; Minami, T; Ida, K; Nishimura, S; Morita, S; Kojima, M; Hidekuma, S; Itoh, SI; Takahashi, C; Inoue, N; Suzuki, H; Okamura, S; Matsuoka, K, Dynamic behavior of potential in the plasma core of the CHS heliotron/torsatron, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.79.1054, 79.0, 6.0, 1054.0-1057.0, 0.0, 1997.08, During combined electron cyclotron and neutral beam heating, an abrupt drop and rise in potential by about one half of the central electron temperature (similar to 400 V) was observed in the core of the compact helical system heliotron/torsatron plasma. Drastic changes of radial electric field between positive and negative states occur over periods as short as 60 mu s, which is much shorter than the energy confinement time scale of about a few milliseconds. A nonlinear relation between the radial electric field and radial current is obtained. This is the first experimental observation of a microsecond time scale spontaneous transition based on an electric field bifurcation in toroidal helical plasmas..
538. A Fujisawa, H Iguchi, S Lee, TP Crowley, Y Hamada, S Kubo, H Idei, H Sanuki, K Itoh, T Minami, K Tanaka, S Nishimura, K Ida, S Hidekuma, M Kojima, C Takahashi, S Okamura, K Matsuoka, Direct observation of potential profiles with a 200 keV heavy ion beam probe on the Compact Helical System, PHYSICS OF PLASMAS, 4.0, 5.0, 1357.0-1361.0, 1997.05.
539. A. Fujisawa, H. Iguchi, S. Lee, T. P. Crowley, Y. Hamada, S. Kubo, H. Idei, H. Sanuki, K. Itoh, T. Minami, K. Tanaka, S. Nishimura, K. Ida, S. Hidekuma, M. Kojima, C. Takahashi, S. Okamura, K. Matsuoka, Direct observation of potential profiles with a 200 keV heavy ion beam probe on the Compact Helical System, Physics of Plasmas, 10.1063/1.872310, 4, 5, 1357-1361, 1997.05, [URL], In this paper we present space potential profiles directly observed in a toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings, 12th International Conference on Plasma Physics and Controlled Nuclear Fusion, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411], using a 200 keV heavy ion beam probe. The potential profiles exhibit widely varied characteristics, including positive and negative polarities for electron cyclotron and neutral beam-heated plasmas, respectively. The behavior of high-energy particles in the CHS plasmas are deduced from loss cone diagrams evaluated from the observed potential profiles..
540. T. Watari, R. Kumazawa, K. Nishimura, T. Mutoh, T. Seki, S. Masuda, T. Shoji, F. Simbo, T. Ido, R. Akiyama, A. Ando, A. Ejiri, A. Fujisawa, H. Idei, K. Ida, H. Iguchi, M. Isobe, M. Iwase, S. Kubo, T. Minami, K. Matsuoka, T. Morisaki, S. Morita, S. Mutoh, S. Murakami, K. Narihara, S. Okamura, T. Ozaki, M. Sasao, C. Takahashi, T. Kawamoto, K. Tanaka, J. Xu, J. M. Noterdaeme, D. A. Rasmussen, J. F. Lyon, J. B. Wilgen, D. E. Greenwood, D. J. Hoffman, E. F. Jaeger and M. Murakami, RF heating experiments in CHS and RF development for LHD, The twelfth topical conference on radio frequency power in plasmas, 403.0, 1.0, 57.0-64.0, Vol. 403, No. 1, Pages 57-64, 1997.04.
541. Ozaki, T., Okamura, S., Zanza, V., Bracco, G., Moleti,A., Tilia, B., Sibio,A., Sudo,S., Yamada, H., Morita,S., Akiyama, R., Ejiri, A., Fujisawa, A., Hamada, Y., Hasegawa, Y., Ida, K., Idei, H., Iguchi,H., Inoue, N., Iwase, M., Design study of high energy neutral particle measurements in a LHD, Fusion Engineering and Design, 34-35, 535-538, 1997.03.
542. K Tanaka, A Ejiri, K Kawahata, S Okajima, K Matsuoka, S Okamura, K Nishimura, R Akiyama, K Ida, H Idei, H Iguchi, N Inoue, S Kubo, R Kumazawa, S Morita, T Minami, S Muto, K Narihara, T Ozaki, H Suzuki, C Takahashi, K Toi, J Xu, I Yamada, Temporal evolutions of electron density profiles of CHS and its transport aspects, FUSION ENGINEERING AND DESIGN, 34.0, 399-401, 34, 399-401, 1997.03.
543. A Sagara, Y Hasegawa, K Tsuzuki, N Inoue, H Suzuki, T Morisaki, N Noda, O Motojima, S Okamura, K Matsuoka, R Akiyama, K Ida, H Idei, K Iwasaki, S Kubo, T Minami, S Morita, K Narihara, T Ozaki, K Sato, C Takahashi, K Tanaka, K Toi, I Yamada, Real time boronization experiments in CHS and scaling for LHD, JOURNAL OF NUCLEAR MATERIALS, 241.0, 979.0-976.0, 1997.02.
544. T. Morisaki, A. Komori, R. Akiyama, Hiroshi Idei, H. Iguchi, N. Inoue, Y. Kawai, S. Kubo, S. Masuzaki, K. Matsuoka, T. Minami, S. Morita, N. Noda, N. Ohyabu, S. Okamura, M. Osakabe, H. Suzuki, K. Tanaka, C. Takahashi, H. Yamada, I. Yamada, O. Motojima, Experimental study of edge plasma structure in various discharges on compact helical system, Journal of Nuclear Materials, 241-243, 977-981, 1997.02, Precise measurements of edge density profiles in various discharges have been performed successfully in the compact helical system (CHS) with a thermal neutral lithium beam probe. During high beta discharges, an outward shift of the plasma edge boundary was observed with an increase in the beta value, which was found to agree qualitatively with theoretical calculations. Experiments with different magnetic field configurations, i.e., with limiter, divertor and with an m/n = 1/1 island, were also performed. Clear difference in the edge density profiles among the configurations and a large change of plasma parameters in the configuration with the m/n = 1/1 island were observed..
545. A. Sagara, Y. Hasegawa, K. Tsuzuki, N. Inoue, H. Suzuki, T. Morisaki, N. Noda, O. Motojima, S. Okamura, K. Matsuoka, R. Akiyama, K. Ida, Hiroshi Idei, K. Iwasaki, S. Kubo, T. Minami, S. Morita, K. Narihara, T. Ozaki, K. Sato, C. Takahashi, K. Tanaka, K. Toi, I. Yamada, Real time boronization experiments in CHS and scaling for LHD, Journal of Nuclear Materials, 241-243, 972-976, 1997.02, As a promising wall-conditioning technique in LHD under steady-state high magnetic fields with superconducting magnets, real time boronization (RTB) by puffing decaborane B10H14 into the main NBI-heated plasma has been first examined in CHS. It is shown that, as compared with the usual glow discharge method, only the 2 orders smaller amount of decaborane is efficient to reduce plasma impurities such as oxygen and metals, resulting in expansion of the operating region of the plasma density and stored energy. The puffing at the inside of the LCFS gives better results on RTB than the outer. Even after RTB on the wall at the room temperature, hydrogen recycling does not increase probably due to the small consumed amount with a high plasma heating power used. The operative RTB parameters expected in LHD are estimated using the first scaling of boronization on the device size..
546. K Ohkubo, S Kubo, H Idei, M Sato, T Shimozuma, Y Takita, Coupling of tilting Gaussian beam with hybrid mode in the corrugated waveguide, International Journal of Infrared and Millimeter Waves, 18.0, 1.0, 23.0-41.0, 1997.01, The mode-conversion loss in the matching between the gaussian beam emanated from the gyrotron and the hybrid mode in the circular corrugated waveguide with the diameter of 2a is discussed. By numerical calculation, it is found that the loss considerably increases and optimum waist sizew 0 changes when TEM00 mode with the wavelength λ is injected with offset or tilt. By fitting numerical data to the polynomial function, it becomes evident that the scaling formulas of the losses for the off-axis shiftr d and for the tilt angle θ are derived to be 2.3(r d /a)2 – 2.2(r d /a)4 and 3.9(aα/λ)2 – 5.6(aθ/λ)4 for fixedw 0/a=0.643, respectively. To keep the mode-conversion loss ≤1% for the frequency of 168 GHz and 2a=88.9 mm, tilting angle and offset should be less than 0.1 degrees and 2.9 mm, respectively..
547. Fujisawa, A; Iguchi, H; Lee, S; Crowley, TP; Hamada, Y; Hidekuma, S; Kojima, M; Kubo, S; Idei, H; Nishimura, K; , Potential profile measurements on compact helical system (CHS) using a 200 keV heavy ion beam probe, FUSION ENGINEERING AND DESIGN, 34.0, 649.0-651.0, 1997.01.
548. MORITA, S; IDEI, H; IGUCHI, H; KUBO, S; MATSUOKA, K; MINAMI, T; OKAMURA, S; OZAKI, T; TANAKA, K; TOI, K; , A study on density profile and density limit of NBI plasmas in the Compact Helical System, Proc of 16th IAEA Fusion Energy Conference, 4.0, INIS-AU--0055, 1997.01, The mechanism of density profile formation has been studied in the Compact Helical System (CHS). It has generally been known that the profiles become peaked and hollow in limiter and divertor dominated cases, respectively. This tendency does not change for the direction of neutral beam injection (NBI) such as co- and counterinjection, resulting in a difference of the electric field. It is also found that the density profiles are not affected by the magnetic configuration itself. The density profile is, however, affected by limiter insertion. The edge ion temperatures were correlated with the density peaking factor, ne0/< ne>. As a result, it was found that a peaked profile (ne0/< ne> ≥ 1.5) can be obtained with a higher edge ion temperature (≥ 40 eV at ρ = 0.9). These results indicate the importance of the energy distribution of the incoming neutral particles. An analysis is done to explain the results. The density limit has also been studied in CHS NBI plasmas. It was found that the density limit was strongly affected by the density profile. The mechanism related to the density limit is discussed. .
549. T. Shimozuma, S. Morimoto, M. Sato, Y. Takita, S. Ito, S. Kubo, Hiroshi Idei, K. Ohkubo, T. Watari, A forced gas-cooled single-disk window using silicon nitride composite for high power CW millimeter waves, International Journal of Infrared and Millimeter Waves, 10.1007/BF02678306, 18, 8, 1479-1493, 1997.01, [URL], Silicon nitride composite as a candidate of a window material for high power CW (Continuous Wave) millimeter-waves was high power tested especially with a surface cooling by impinging gas nitrogen jets on the single-disk surface. Gas-cooling dramatically suppressed the temperature of the window disk even with gas flow rate of around 100 1/min. With gas cooling of 4651/min., 130kW CW power of HE11 mode could be transmitted through the silicon nitride window with a diameter of 88.9mm. The peak window temperature was completely saturated on 123.6°C. Without gas-cooling it did not saturate and reached 323°C during 30 seconds pulse. A possibility of 1MW CW single disk Brewster windows with a forced gas-cooling is discussed, resulting in convinced prospects of the windows with realistic size and thickness..
550. K. Ohkubo, S. Kubo, Hiroshi Idei, M. Sato, T. Shimozuma, Y. Takita, Coupling of tilting gaussian beam with hybrid mode in the corrugated waveguide, International Journal of Infrared and Millimeter Waves, 18, 1, 39-41, 1997.01, The mode-conversion loss in the matching between the gaussian beam emanated from the gyrotron and the hybrid mode in the circular corrugated waveguide with the diameter of 2a is discussed. By numerical calculation, it is found that the loss considerably increases and optimum waist size w0 changes when TEM00 mode with the wavelength λ is injected with offset or tilt. By fitting numerical data to the polynomial function, it becomes evident that the scaling formulas of the losses for the off-axis shift rd and for the tilt angle θ are derived to be 2.3(rd/a)2 - 2.2(rd/a)4 and 3.9(aθ/λ)2 - 5.6(aθ/λ)4 for fixed w0/a=0.643, respectively. To keep the mode-conversion loss ≤1% for the frequency of 168 GHz and 2a=88.9 mm, tilting angle and offset should be less than 0.1 degrees and 2.9 mm, respectively..
551. T. Ozaki, S. Okamura, V. Zanza, G. Bracco, A. Moleti, B. Tilia, A. Sibio, S. Sudo, H. Yamada, S. Morita, R. Akiyama, A. Ejiri, akihide fujisawa, Y. Hamada, Y. Hasegawa, K. Ida, Hiroshi Idei, H. Iguchi, N. Inoue, M. Iwase, A. Komori, S. Kubo, R. Kumazawa, Y. Liang, S. Masuda, K. Matsuoka, T. Minami, S. Muto, K. Narihara, K. Nishimura, S. Nishimura, I. Nomura, S. Odachi, A. Sagara, H. Suzuki, K. Tanaka, C. Takahashi, K. Toi, J. Xu, I. Yamada, T. Watari, Design study of high energy neutral particle measurements in a LHD, Fusion Engineering and Design, 10.1016/S0920-3796(96)00624-2, 34-35, 535-538, 1997.01, [URL], The development of a high energy neutral particle measurement system for ion temperature measurements and high energy particle confinement analysis in a Large Helical Device (LHD) is described here. We have improved the time-of-flight (TOF) neutral particle analyzer for the LHD which had been developed in ENEA Frascati. The mass rejection factor was improved up to 1/1000 by using a biased diaphragm in front of the stop detector..
552. akihide fujisawa, H. Iguchi, S. Lee, T. P. Crowley, Y. Hamada, S. Hidekuma, M. Kojima, S. Kubo, Hiroshi Idei, K. Nishimura, S. Okamura, K. Matsuoka, Potential profile measurements on compact helical system (CHS) using a 200 keV heavy ion beam probe, Fusion Engineering and Design, 10.1016/S0920-3796(96)00584-4, 34-35, 649-651, 1997.01, [URL], A 200 keV heavy ion beam probe system has been prepared to measure potential profiles in the compact helical system. Probing beam trajectory is successfully controlled by a secondary beam sweep system to keep the injection angle of the secondary beam constant during the radial scan. As a result, it was observed that the potential profile changes after the neutral beam heating is applied on electron cyclotron heated plasmas..
553. S. Masuda, R. Kumazawa, K. Nishimura, T. Mutoh, T. Watari, F. Simbo, T. Seki, T. Ido, R. Akiyama, A. Ando, A. Ejiri, H. Idei, K. Ida, H. Iguchi, M. Isobe, M. Iwase, S. Kubo, K. Matsuoka, T. Morisaki, S. Morita, S. Mutoh, S. Murakami, S. Okamura, T. Ozaki, S. Sakakibara, M. Sasao, C. Takahashi, T. Kawamoto, K. Tanaka, J. Xu, H. Yamada, I. Yamada, D. A. Rasmussen, J. F. Lyon, J. B. Wilgen, D. E. Greenwood, D. J. Hoffman, E. F. Jaeger, M. Murakami, Strong electron heating in CHS ICRF heating experiments, Nuclear Fusion, 10.1088/0029-5515/37/1/I12, 37, 1, 53-68, 1997.01, [URL], An ion cyclotron range of frequencies (ICRF) heating experiment was performed on the Compact Helical System (CHS) device in order to identify the problems in establishing this as a reliable heating method. Radiofrequency heating was applied to plasmas with two ion species produced by ECH. Stored energy increased up to 2.2 kJ with the application of a 590 kW ICRF heating pulse, giving a heating efficiency comparable to that of NBI heating. More importantly, the 'flat-top' of the stored energy was maintained during the pulse. Good heating was realized with 30% proton and 70% deuteron plasmas at high density (4 ×19 m-3). It was found that the best discharges are dominated by electron ICRF heating, which seems to be the reason for the successful results. On the contrary, a flat-top in stored energy has never been obtained in discharges where ion heating dominates. The loss of high energy ions with large pitch angles produced by ion heating appears to degrade the performance and limit the duration of the heating. A similar degradation was encountered in previous ICRF heating experiments in helical systems. A newly designed detector was used to study the loss of the helically trapped particles..
554. K. Tanaka, A. Ejiri, K. Kawahata, S. Okajima, K. Matsuoka, S. Okamura, K. Nishimura, R. Akiyama, K. Ida, Hiroshi Idei, H. Iguchi, N. Inoue, S. Kubo, R. Kumazawa, S. Morita, T. Minami, S. Muto, K. Narihara, T. Ozaki, H. Suzuki, C. Takahashi, K. Toi, J. Xu, I. Yamada, Temporal evolutions of electron density profiles of CHS and its transport aspects, Fusion Engineering and Design, 10.1016/S0920-3796(96)00648-5, 34-35, 399-401, 1997.01, [URL], In order to investigate the characteristics of particle confinement in compact helical system (CHS) plasmas, temporal evolutions of electron density profiles during gas puff modulation are measured using an HCN laser interferometer. Two different magnetic configurations are studied..
555. Pereyaslavets, M; Sato, M; Shimozuma, T; Takita, Y; Idei, H; Kubo, S; Ohkubo, K; Hayashi, K; , Development and simulation of RF components for high power millimeter wave gyrotrons, National Inst. for Fusion Science, Nagoya (Japan), 1996.11.
556. K. TOI, K. N. SATO, Y. HAMADA, S. OHDACHI, H. SAKAKITA, A. NISHIZAWA, A. EJIRI, K. NARIHARA, H. KURAMOTO, Y. KAWASUMI, S. KUBO, T. SEKI, K. KITACHI, J. XU, K. IDA, K. KAWAHATA, I. NOMURA, K. ADACHI, R. AKIYAMA, A. FUJISAWA, J. FUJITA, S. HIDEKUMA, N. HIRAKI, S. HIROKURA, H. IDEI, T. IDO, H. IGUCHI, M. ISOBE, K. IWASAKI, O. KANEKO, Y. KANO, M. KOJIMA, J. KOOG, R. KUMAZAWA, T. KURODA, J. LI, R. LIANG, T. MINAMI, S. MORITA, K. OHKUBO, Y. OKA, S. OKAJIMA, M. OSAKABE, Y. SAKAWA, M. SASAO, K. SATO, T. SHIMPO, T. SHOJI, H. SUGAI, T. WATARI, I. YAMADA, K. YAMAUTI, Studies of Perturbative Plasma Transport, Ice Pellet Ablation and Sawtooth Phenomena in the JIPP T-IIU Tokamak, 16th Conference Proceedings of Fusion Energy, 1.0, 559.0, IAEA-CN-64/A6-S, 1996.10.
557. K Toi, S Ohdachi, T Morisaki, S Sakakibara, S Morita, T Minami, K Tanaka, H Yamada, S Okamura, K Nishimura, K Matsuoka, I Yamada, R Akiyama, A Ando, A Ejiri, K Ida, H Idei, H Iguchi, A Komori, S Kubo, K Narihara, T Ozaki, C Takahashi, K Tsumori, J Xu, Transition behaviour in the H-mode of the CHS heliotron/torsatron, PLASMA PHYSICS AND CONTROLLED FUSION, 38.0, 8.0, 1289.0, 1996.08.
558. K. Toi, S. Ohdachi, T. Morisaki, S. Sakakibara, S. Morita, T. Minami, K. Tanaka, H. Yamada, S. Okamura, K. Nishimura, K. Matsuoka, I. Yamada, R. Akiyama, A. Ando, A. Ejiri, K. Ida, Hiroshi Idei, H. Iguchi, A. Komori, S. Kubo, K. Narihara, T. Ozaki, C. Takahashi, K. Tsumori, J. Xu, Transition behaviour in the H-mode of the CHS heliotron/torsatron, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/38/8/024, 38, 8, 1289-1293, 1996.08, [URL], The H-mode initiated by the control of the rotational transform profile in CHS exhibits a very rapid transition (in 100 μs or less) in NBI heated plasmas. There is no obvious difference in transition behaviour between hydrogen and deuterium. Langmuir probe measurement has revealed that the rapid change in floating potential occurs at the transition, but the change follows the formation of an edge transport barrier. The presence of an t = 1 surface just inside the last closed flux surface and a sawtooth crash triggered by internal modes play an important role in the H-mode transition of CHS..
559. M Fujiwara, K Yamazaki, M Okamoto, J Todoroki, T Amano, T Watanabe, T Hayashi, H Sanuki, N Nakajima, K Itoh, H Sugama, K Ichiguchi, S Murakami, O Motojima, J Yamamoto, T Satow, N Yanagi, S Imagawa, K Takahata, H Tamura, A Nishimura, A Komori, N Inoue, N Noda, A Sagara, Y Kubota, N Akaishi, S Satoh, S Tanahashi, H Chikaraishi, T Mito, S Yamada, S Yamaguchi, S Sudo, KN Sato, T Watari, T Kuroda, O Kaneko, K Ohkubo, S Kitagawa, A Ando, H Idei, K Tsumori, S Kubo, R Kumazawa, T Mutoh, Y Oka, M Sato, T Seki, T Shimozuma, Y Takeiri, Y Hamada, K Narihara, K Kawahata, S Fujisawa, S Hidekuma, T Minami, I Yamada, A Ejiri, K Tanaka, M Sasao, H Iguchi, KY Watanabe, H Yamada, N Ohyabu, H Suzuki, A Iiyoshi, Large helical device (LHD) program, Journal of fusion energy, 15.0, 1.0, 7.0-153.0, 1996.06.
560. Iwase, Makoto; Ohkubo, Kunizo; Kubo, Shin; Idei, Hiroshi; , Band rejection filter for measurement of electron cyclotron emission during electron cyclotron heating, Jornal of Plasma and Fusion Research, 72.0, 3.0, 270.0-278.0, 1996.03, For the measurement of electron cyclotron emission from the high temperature plasma, a band rejection filter in the range of 40 〜 60 GHz is designed to reject the 53.2 GHz signal with large amplitude from the gyrotron for the purpose of plasma electron heating. The filter developed with ten sets of three quarters-wavelength coupled by TE_<111> mode of tunable resonant cavity has rejection of 50 dB and 3 dB bandwidth of 500 MHz. The modified model of Tschebysheff type for the prediction of rejection is proposed. It is confirmed that the measured rejection as a function of frequency agrees well with the experimental results for small coupling hole, and also clarified that the rejection ratio increases for the large coupling hole..
561. A Fujisawa, S Kubo, H Iguchi, H IDEI, T MINAMI, H SANUKI, K ITOH, S OKAMURA, K MATSUOKA, K TANAKA, S LEE, M KOJIMA, TP CROWLEY, Y HAMADA, M IWASE, H NAGASAKI, H SUZUKI, N INOUE, R AKIYAMA, M OSAKABE, S MORITA, C TAKAHASHI, S MUTO, A EJIRI, K IDA, S NISHIMURA, K NARIHARA, I YAMADA, K TOI, S OHDACHI, T OZAKI, A KOMORI, K NISHIMURA, S HIDEKUMA, K OHKUBO, DA RASMUSSEN, JB WILGEN, M MURAKAMI, T WATARI, M FUJIWARA, Experimental study of plasma confinement and heating efficiency through potential profile measurements with a heavy ion beam probe in the compact helical system, Proc. 16th IAEA Fusion Energy Conference, Montreal, Canada 1996, 2.0, 41.0-54.0, IAEA-CN-64/C1-5, 1996.01.
562. Kubo, S; Idei, H; Iwase, M; Ohkubo, K; Minami, T; Yamada, I; Narihara, K; Tanaka, K; Wilgen, JB; Murakami, M; , High power local ECH in CHS, The 11th topical conference on radio frequency power in plasmas, 355.0, 1.0, 155.0-158.0, 1996.01.
563. M. Fujiwara, K. Yamazaki, M. Okamoto, J. Todoroki, T. Amano, T. Watanabe, T. Hayashi, H. Sanuki, N. Nakajima, K. Itoh, H. Sugama, K. Ichiguchi, S. Murakami, O. Motojima, J. Yamamoto, T. Satow, N. Yanagi, S. Imagawa, K. Takahata, H. Tamura, A. Nishimura, A. Komori, N. Inoue, N. Noda, A. Sagara, Y. Kubota, N. Akaishi, S. Satoh, S. Tanahashi, H. Chikaraishi, T. Mito, S. Yamada, S. Yamaguchi, S. Sudo, K. N. Sato, T. Watari, T. Kuroda, O. Kaneko, K. Ohkubo, S. Kitagawa, A. Ando, Hiroshi Idei, K. Tsumori, S. Kubo, R. Kumazawa, T. Mutoh, Y. Oka, M. Sato, T. Seki, T. Shimozuma, Y. Takeiri, Y. Hamada, K. Narihara, K. Kawahata, S. Fujisawa, S. Hidekuma, T. Minami, I. Yamada, A. Ejiri, K. Tanaka, M. Sasao, H. Iguchi, K. Y. Watanabe, H. Yamada, N. Ohyabu, H. Suzuki, A. Iiyoshi, Large helical device (LHD) program, Journal of Fusion Energy, 10.1007/BF02266926, 15, 1-2, 7-153, 1996.01, [URL], The largest superconducting fusion machine, Large Helical Device (LHD), is now under construction in Japan and will begin operation in 1997. Design and construction of related R&D programs are now being carried out. The major radius of this machine is 3.9 m and the magnetic field on the plasma center is 3 T. The NbTi superconducting conductors are used in both helical coils and poloidal coils to produce this field. This will be upgraded in the second phase a using superfluid coil cooling technique. A negative ion source is being successfully developed for the NBI heating of LHD. This paper describes the present status and progress in its experimental planning and theoretical analysis on LHD, and the design and construction of LHD torus, heating, and diagnostics equipments..
564. S. Okamura, K. Matsuoka, K. Nishimura, K. Tsumori, R. Akiyama, S. Sakakibara, H. Yamada, S. Morita, T. Morisaki, N. Nakajima, K. Tanaka, J. Xu, K. Ida, H. Iguchi, A. Lazaros, T. Ozaki, H. Arimoto, A. Ejiri, M. Fujiwara, Hiroshi Idei, O. Kaneko, K. Kawahata, T. Kawamoto, A. Komori, S. Kubo, O. Motojima, V. D. Pustovitov, C. Takahashi, K. Toi, I. Yamada, High beta discharges with neutral beam injection in CHS, Nuclear Fusion, 10.1088/0029-5515/35/3/I03, 35, 3, 283-296, 1995.12, [URL], High beta plasmas with a volume averaged equilibrium beta value of 2.1% were produced in CHS using tangential neutral beam injection. This beta value was achieved with the confinement improvement (reheat mode) observed after turning off strong gas puffing. Wall conditioning with titanium gettering was used to make high density operation (ne ≤ 8 × 10 19 m-3) possible for low magnetic fields (Bt = 0.6 T). The discharges start with the magnetic hill configuration (in vacuum) and finally achieve Mercier stable equilibrium owing to the self-stabilization effect given by the magnetic well which is produced by the plasma pressure. The Shafranov shift was about 40% of a plasma minor radius. Magnetic fluctuations did not increase with increasing plasma pressure when the beta value exceeded 1%. Dynamic poloidal field control was applied to suppress the outward plasma shift with increasing plasma pressure. Such operation gave an additional increase of beta value compared with the constant poloidal field operation..
565. H. Sanuki, K. Itoh, J. Todoroki, K. Ida, Hiroshi Idei, H. Iguchi, H. Yamada, Theoretical and experimental studies on electric field and confinement in helical systems, Physica Scripta, 10.1088/0031-8949/52/4/018, 52, 4, 461-466, 1995.10, [URL], The present study consists of two parts. The first part is oriented to a theoretical model of selfconsistent analysis to determine simultaneously the electric field and loss cone boundary in heliotron/torsatron configuration under the influence of nonclassical particle losses. The second part is refered to the analysis on NBI heated and ECH plasmas in Compact Helical System (CHS) device. Comparison is made between theoretical results and experimental observations..
566. Morita, S., Yamada, H., Akiyama, R., Ando, A., Arimoto, H., Ida, K., Idei, H., Iguchi, H., Kaneko, O., Kubo, S., Kumazawa, R., Matsuoka, K., Minami, T., Morisaki, T., Muto, S., Narihara, K., Nishimura, K., Okamura, S., Ozaki, T., Sakakibara, S., Particle confinement of limiter- and divertor-dominated NBI plasmas in CHS, Fusion Technology, 27, 239-243, 1995.04.
567. TOI, K; MORISAKI, T; SAKAKIBARA, S; OHDACHI, S; MINAMI, T; MORITA, S; YAMADA, H; TANAKA, K; IDA, K; OKAMURA, S; EJIRI, A; IGUCHI, H; NISHIMURA, K; MATSUOKA, K; ANDO, A; XU, J; YAMADA, I; NARIHARA, K; AKIYAMA, R; IDEI, H; KUBO, S; OZAKI, T; TAKAHASHI, C; TSUMORI, K, H-MODE STUDY IN CHS, FUSION TECHNOLOGY, 27, 190-193, 1995.04.
568. IWASE, M; KUBO, S; KUMAZAWA, R; IDEI, H; OHKUBO, K; MUTOH, T; WATARI, T; NISHIMURA, K; OKAMURA, S; MATSUOKA, K; MINAMI, T; YAMADA, I; NARIHARA, K; IDA, K; IGUCHI, H, ESTIMATE OF THE ELECTRON POWER DEPOSITION PROFILE IN CHS, FUSION TECHNOLOGY, 27, 248-251, 1995.04.
569. Sanuki, H.: Itoh, K.: Todoroki, J.:Ida, K; Idei, H; Iguchi, H; Yamada, H; , Theoretical and experimental studies on electric field and confinement in helical systems, PHYSICA SCRIPTA, 52.0, 4.0, 461.0, 1995.04.
570. S Okamura, K Matsuoka, K Nishimura, K Tsumori, R Akiyama, S Sakakibara, H Yamada, S Morita, T Morisaki, N Nakajima, K Tanaka, J Xu, K Ida, H Iguchi, A Lazaros, T Ozaki, H Arimoto, A Ejiri, M Fujiwara, H Idei, O Kaneko, K Kawahata, T Kawamoto, A Komori, S Kubo, O Motojima, VD Pustovitov, C Takahashi, K Toi, I Yamada, High beta discharges with neutral beam injection in CHS, NUCLEAR FUSION, 35.0, 3.0, 283.0, 1995.03.
571. Ozaki,T., Morita, S., Kumazawa, R., Nishimura, K., Masuda, S., Ejiri, A., Minami, T., Yamada, I., Narihara, K., Okamura, S., Matsuoka, K., Sagara, A., Idei, H., Kubo, S., Tanaka, K., Takahashi, C., Measurements of H / (H+D) ratios in ICRF heating experiments of CHS, Fusion Technology, 27, 244-247, 1995.01.
572. KURODA, T; OHKUBO, K; WATARI, T; SATO, M; KUMAZAWA, R; MUTOH, T; KANEKO, O; OKA, Y; KUBO, S; TAKEIRI, Y; TSUMORI, K; ANDO, A; IDEI, H; SEKI, T, DEVELOPMENT OF HIGH-POWER HEATING FOR LARGE HELICAL DEVICE, FUSION ENGINEERING AND DESIGN, 26, 1-4, 227-238, 1995.01.
573. MATSUOKA, K; OKAMURA, S; NISHIMURA, K; TSUMORI, K; AKIYAMA, R; YAMADA, H; SAKAKIBARA, S; LAZAROS, A; XU, J; IDA, K; TANAKA, K; MORISAKI, T; MORITA, S; ARIMOTO, H; EJIRI, A; FUJIWARA, M; IDEI, H; IGUCHI, H; KANEKO, O; KAWAMOTO, T; KUBO, S; KURODA, T; MOTOJIMA, O; OZAKI, T; PUSTOVITOV, VD; SAGARA, A; TAKAHASHI, C; TOI, K; WATARI, T; YAMADA, I, HIGH-BETA EXPERIMENT AND CONFINEMENT REGIMES IN A COMPACT HELICAL SYSTEM, FUSION ENGINEERING AND DESIGN, 26, 1-4, 135-140, 1995.01.
574. Ida, K; Idei, H; Sanuki, H; Itoh,K., Xu,J., Hidekuma,S., Kondo, K., Sahara,A., Zushi,H., Itoh,S.I., Fukuyama, A., Adati, K., Akiyama,R., Besshou, S., Ejiri, A., Fujisawa,A., Fujiwara, M., Hamada, Y., Hirokura,S., Iguchi, H., Kaneko,O., Kawahata,K., Kwasumi,Y., Kojima,M., Kubo, S., Kuramoto, H., Lazaros,A., Liang, R., Matsuoka, K., Minami, T., Mizuuchi, T., Morisaki, T., Morita, S., Nagasaki, K., Narihara,K., Nishimura, K., Nishizawa, A., Obiki, T., Okada, H., Okamura,S., Ozaki, T., Sagara, A., Sakakibara, S., Sakakita, H., Sano, F., Sasao,M., Sato, K.N., Seki,T., Sudo,S., Takahashi, C., Takita, Y., Tanaka, K., Toi, K., Tuimori, K., Tuzuki, T., Watari.T., Yamada, H., Yamada, I., Control of the radial electric field in a toroidal plasma, FIFTEENTH CONFERENCE PROCEEDINGS. SEVILLE. SPAIN. 26 SEPTEMBER-1 OCTOBER 1994, 375.0, 1995.01.
575. H Idei, S Kubo, H Sanuki, H Iguchi, K Ida, S Morita, R Akiyama, H Arimoto, K Matsuoka, K Nishimura, K Ohkubo, S Okamura, C Takahashi, Y Takita, K Toi, K Tsumori, H Yamada, I Yamada, Experimental study on density pump-out due to electron cyclotron heating in the compact helical system heliotron-torsatron, Journal of Infrared and Millimeter Waves, 23.0, 1.0, 167.0-172.0, 1995.01.
576. Ohkubo, K; Kubo, S; Iwase, M; Idei, H; Sato, M; Shimozuma, T; Takita, Y; Kuroda, T; , Miter bend with movable corrugated waveguides and 62m-straight corrugated waveguide for ECH transmission system, Fusion technology 1994. Proceedings. Vol. 1, 1995.01.
577. K Ohkubo, S Kubo, M Sato, H Idei, Y Takita, T Kuroda, Rectangular corrugated waveguide and parallel corrugated plates for an elliptical gaussian beam, FUSION ENGINEERING AND DESIGN, 26.0, 1.0, 325.0-333.0, 1995.01.
578. S Kubo, K Ohkubo, H Idei, M Sato, Y Takita, M Iwase, T Kuroda, Antenna and transmission system for high power electron cyclotron heating in a compact helical system, FUSION ENGINEERING AND DESIGN, 26.0, 1.0, 319.0-324.0, 1995.01, Antenna and transmission system for high power electron cyclotron heating in a compact helical system.
579. S. Kubo, K. Ohkubo, Hiroshi Idei, M. Sato, Y. Takita, M. Iwase, T. Kuroda, Antenna and transmission system for high power electron cyclotron heating in a compact helical system, Fusion Engineering and Design, 10.1016/0920-3796(94)00197-F, 26, 1-4, 319-324, 1995.01, [URL], An electron cyclotron heating (ECH) system for the compact helical system using two types of high power gyrotron as a power source is designed. In order to utilize fully the advantage of the ECH, the antenna system is designed so as to inject the microwave power as an elliptic gaussian beam, which allows well-defined high power local heating. This antenna and associated transmission system from gyrotron are designed with the quasi-optical concept. This design concept and the results of the cold test for the transmission and antenna system are described. The resultant beam parameter of the cold test for the antenna system shows fairly good agreement with the designed value, which indicates the validity of this design concept. The power transmission efficiency of about 90% was estimated from the measured power at both ends..
580. T. Kuroda, K. Ohkubo, T. Watari, M. Sato, R. Kumazawa, T. Mutoh, O. Kaneko, Y. Oka, S. Kubo, Y. Takeiri, K. Tsumori, A. Ando, Hiroshi Idei, T. Seki, Development of high-power heating for large helical device, Fusion Engineering and Design, 10.1016/0920-3796(94)00190-I, 26, 1-4, 227-238, 1995.01, [URL], Three high-power heating mechanisms, i.e. electron cyclotron resonance heating, ion cyclotron resonance heating and neutral beam injection heating will be available to achieve operation of the Large Helical Device in the (i) high nτT mode, (ii) high Ti mode and (iii) high β mode. The requirements for each heating method are (i) 10 MW of ECH at a frequency of 84 GHz with a pulse length of 10 s, (ii) 3 MW of ICRF heating in the frequency range 25-100 MHz in CW operation and (iii) 20 MW of NBI at a hydrogen injection energy of 125 keV and 10 s operation. The components of each heating mechanism which need development individually exist, i.e. (i) a high-power gyrotron with an output power of 1 MW in CW operation and a high-efficiency transmission line for ECH, (ii) a high-power co-axial transmission line with cooling and an automatic matching circuit for ICRF heating and (iii) a large negative ion source and some components of the beam line for NBI. The heating scenario and the present status of the development are described for each heating system..
581. Hiroshi Idei, S. Kubo, H. Sanuki, H. Iguchi, K. Ida, S. Morita, R. Akiyama, H. Arimoto, K. Matsuoka, K. Nishimura, K. Ohkubo, S. Okamura, C. Takahashi, Y. Takita, K. Toi, K. Tsumori, H. Yamada, I. Yamada, Experimental study on density pump-out due to electron cyclotron heating in the compact helical system heliotron - torsatron, Fusion Engineering and Design, 10.1016/0920-3796(94)00182-7, 26, 1-4, 167-172, 1995.01, [URL], The phenomenon of density pump-out or the degradation of particle confinement is observed for plasmas with electron cyclotron heating (ECH) in the compact helical system. It is confirmed that the enhancement of the particle flux with ECH is triggered by the production of electrons accelerated perpendicularly to the magnetic field with ECH..
582. K. Matsuoka, S. Okamura, K. Nishimura, K. Tsumori, R. Akiyama, H. Yamada, S. Sakakibara, A. Lazaros, J. Xu, K. Ida, K. Tanaka, T. Morisaki, S. Morita, H. Arimoto, A. Ejiri, M. Fujiwara, Hiroshi Idei, H. Iguchi, O. Kaneko, T. Kawamoto, S. Kubo, T. Kuroda, O. Motojima, T. Ozaki, V. D. Pustovitov, A. Sagara, C. Takahashi, K. Toi, T. Watari, I. Yamada, High β experiment and confinement regimes in a compact helical system, Fusion Engineering and Design, 10.1016/0920-3796(94)00178-A, 26, 1-4, 135-140, 1995.01, [URL], A volume-averaged equilibrium β value 〈β
eq
〉 of 2.14% is achieved in a compact helical system using two neutral beam lines with balanced injection and intense wall conditioning with Ti gettering. This value is the highest β value realized so far in helical systems. Reheat mode, where the stored energy increases after turn-off of a strong gas puff, is employed in the experiment. Discharge conditions are as follows: B
t
= 0.61 T; beam power through the port, 1.1 MW (coinjection) and 0.8 MW (counterinjection); line-averaged electron density n
e
= 6.5 × 10
13
cm
-3
. Amplitudes of magnetic fluctuations integrated over the frequency range from 3 kHz to 100 kHz become saturated at 〈β
eq
〉 higher than 1%. Dominant coherent modes are m n = 2 1 and 1 1 when 〈β
eq
〉 is lower and higher respectively than 1%. Dependence of the energy confinement time τ
E
on n
e
(up to 8 × 10
13
cm
-3
) and B
t
(from 0.6 to 1.8T) is also studied in this high β experiment. When the density increases τ
E
degrades compared with the LHD scaling; the density dependence exhibits Bohm-like behaviour. On the contrary, τ
E
scales as B
t
≈0.75
, which is rather close to the LHD scaling (gyro-Bohm-like behaviour)..
583. K. Ohkubo, S. Kubo, M. Sato, Hiroshi Idei, Y. Takita, T. Kuroda, Rectangular corrugated waveguide and parallel corrugated plates for an elliptical gaussian beam, Fusion Engineering and Design, 10.1016/0920-3796(94)00198-G, 26, 1-4, 325-333, 1995.01, [URL], The generation of an elliptical gaussian beam for an antenna for the large helical device is discussed. Numerical and experimental results on a square corrugated waveguide and parallel corrugated plates and its combination are described. It is shown that the parallel corrugated plates provide a good performance for the elliptical gaussian beam..
584. K. Toi, R. Akiyama, H. Arimoto, A. Ejiri, K. Ida, Hiroshi Idei, H. Iguchi, O. Kaneko, K. Kawahata, A. Komori, S. Kubo, K. Matsuoka, T. Morisaki, S. Morita, K. Nishimura, S. Okamura, A. Sagara, S. Sakakibara, C. Takahashi, Y. Takita, K. Tanaka, K. Tsumori, J. Xu, H. Yamada, I. Yamada, H-mode transition in the CHS heliotron/torsatron, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/36/7A/014, 36, 7 A, 1994.12, [URL], Characteristics of the H-mode transition observed in CHS are described. The transition is achieved with modification of the rotational transform profile by inducing a small ohmic heating current. The transition is often initiated by a sawtooth crash caused by a coherent mode with the poloidal mode number m=2 and toroidal one n=1..
585. I. Yamada, S. Kubo, K. Watanabe, H. Iguchi, S. Okamura, S. Morita, Hiroshi Idei, I. Yamada, H. Arimoto, K. Matsuoka, K. Nishimura, S. Sakakibara, C. Takahashi, Y. Takita, Response of bootstrap current and electron thermal conductivity to shaping in an ECRH plasma in the CHS heliotron/torsatron, Nuclear Fusion, 10.1088/0029-5515/34/5/I12, 34, 5, 641-647, 1994.12, [URL], The bootstrap current and electron thermal conductivity have been investigated in ECRH plasmas on the CHS heliotron/torsatron. The neoclassical transport coefficients have been externally controlled over a wide range by changing the ellipticity of the plasma cross-section. While local thermal conductivity, as well as global confinement, have shown inconsistency with the neoclassical predictions, the observed toroidal net current has been successfully explained by considering the three dimensional geometry with the available neoclassical theory. The present experimental results indicate that the transport parallel to the magnetic field lines (bootstrap current) is likely to be neoclassical but that the perpendicular transport (thermal conductivity) is anomalous, which is common in current less plasmas as well as tokamaks..
586. H Idei, K Ida, H Sanuki, S Kubo, H Yamada, H Iguchi, S Morita, S Okamura, R Akiyama, H Arimoto, K Matsuoka, K Nishimura, K Ohkubo, C Takahashi, Y Takita, K Toi, K Tsumori, I Yamada, Formation of positive radial electric field by electron cyclotron heating in compact helical system, PHYSICS OF PLASMAS, 1.0, 10.0, 3400.0-3406.0, 1994.10.
587. Nishimura, K., Kumazawa, R., Mutoh, T., Watari, T., Seki, T., Ando, A., Masuda, S., Shinpo, F., Murakami, S., Okamura, S., Yamada, H., Matsuoka, K., Morita, S., Ozaki, T., Ida, K., Iguchi, H., Yamada, I., Ejiri, A., Idei, H., Muto, S., ICRF heating in CHS, Plasma Physics and Controlled Nuclear Fusion Research, 1, 783-789, 1994.09.
588. Okamura, S., Matsuoka, K., Nishimura, K., Tsumori, K., Akiyama, R., Sakakibara, S., Yamada, I., Morita, S., Morisaki, T., Nakajima, N., Tanaka, K., Xu, J., Ida, K., Iguchi, H., Lazaros, A., Ozaki, T., Arimoto, H., Ejiri, A., Fujiwara, M., Idei, H., High beta experiments in CHS, Plasma Physics and Controlled Nuclear Fusion Research , 1, 381-388, 1994.09.
589. K Ohkubo, S Kubo, M Iwase, H Idei, M Sato, T Shimozuma, Y Takita, T Kuroda, Hybrid mode trasmission in 62-m corrugated waveguide, International journal of infrared and millimeter waves, 15.0, 9.0, 1507.0-1519.0, 1994.09.
590. K. TOI, T. MORISAKI, S. SAKAKIBARA, A. EJIRI, H. YAMADA, S. MORITA, K. TANAKA, N. NAKAJIMA, S. OKAMURA, H. IGUCHI, K. IDA, K. TSUMORI, S. OHDACHI, K. NISHIMURA, K. MATSUOKA, J. XU, I. YAMADA, T. MINAMI, K. NARIHARA, R. AKIYAMA, A. ANDO, H. ARIMOTO, A. FUJISAWA, M. FUJIWARA, H. IDEI, O. KANEKO, K. KAWAHATA, A. KOMORI, S. KUBO, R. KUMAZAWA, T. OZAKI, A. SAGARA, C. TAKAHASHI, Y. TAKITA, T. WATARI , Impact of rotational transform profile control on plasma confinement and stability in CHS, Plasma Physics and Controlled Nuclear Fusion Research 1994: Fifteenth Conference Proceedings, Seville, Spain, 26 September-1 October 1994, Vol. 2, 2.0, 331.0, IAEA-CN-60/A6/C-P3, 1994.09.
591. K. Ohkubo, S. Kubo, M. Iwase, Hiroshi Idei, M. Sato, T. Shimozuma, Y. Takita, T. Kuroda, Hybrid mode trasmission in 62-m corrugated waveguide, International Journal of Infrared and Millimeter Waves, 10.1007/BF02096093, 15, 9, 1507-1519, 1994.09, [URL], Experimental measurements by wavepacket reflectometry are carried out to verify the low transmission loss of hybrid mode on HE11 in the corrugated waveguide with 88.9 mm in diameter. The HE11 mode is injected into the 62-m straight circular corrugated waveguide and the beat between the HE11 and HE21 (including degenerated TE01 and TM02) modes is observed. The loss is too small to measure and inferred to be less than 2 db/km. The result shows that the use of HE11 mode for electron cyclotron heating system is suitable..
592. Kubo, S; Ohkubo, K; Idei, H; Sato, M; Takita, Y; Kuroda, T; , ECH (electron cyclotron heating) launching system for LHD (large helical device) and CHS (compact helical system), IAEA technical committee meeting on RF launchers for plasma heating and current drive; Naka, Ibaraki (Japan), 16C, 1.0, 152.0-156.0, 1994.08, The effectiveness of the mirror surface definition for the focusing mirrors using constant phase concept is demonstrated and actually applied for the new antenna system for CHS. Preliminary design of the ECH launcher for LHD is done based on the same idea. The minimum beam parameters are 15 mm in radial direction and 50 mm in toroidal direction under present allowed port space..
593. K Toi, R Akiyama, H Arimoto, A Ejiri, K Ida, H Idei, H Iguchi, O Kaneko, K Kawahata, A Komori, S Kubo, K Matsuoka, T Morisaki, S Morita, K Nishimura, S Okamura, A Sagara, S Sakakibara, C Takahashi, Y Takita, K Tanaka, K Tsumori, J Xu, H Yamada, I Yamada, H-mode transition in the CHS heliotron/torsatron, PLASMA PHYSICS AND CONTROLLED FUSION, 36.0, 7A, A117, 1994.07.
594. I. Yamada, S. Kubo, K. Watanabe, H. Iguchi, S. Okamura, S. Morita, H. Idei, I. Yamada, H. Arimoto, K. Matsuoka, K. Nishimura, S. Sakakibara, C. Takahashi and Y. Takita, Response of bootstrap current and electron thermal conductivity to shaping in an ECRH plasma in the CHS heliotron/torsatron, NUCLEAR FUSION, 34.0, 5.0, 641.0, Vol. 34, No. 5, Pages 641, 1994.04.
595. Ida, K; Idei, H; Sanuki, H; , Control of radial electric field in torus plasma, National Inst. for Fusion Science, 1994.01, The radial electric field is controlled by changing the direction of neutral beam from co to counter to plasma current in tokamak, while it is controlled by the 2nd harmonic ECH and NBI and pellet infection in heliotron/torsatron..
596. Ohkubo, K; Kubo, S; Sato, M; Idei, H; Takita, Y; Kuroda, T; , Development of ECH System for Large Helical Device at NIFS, Strong Microwaves in Plasmas: 2nd International Workshop: Papers, 60.0, 1994.01.
597. Idei, Hiroshi; Kubo, Shin; Hosokawa, Minoru; Iguchi, Harukazu; Ohkubo, Kunizo; Sato, Teruyuki; , Electron cyclotron emission from optically thin plasma in compact helical system, JAPANESE JOURNAL OF APPLIED PHYSICS, 33.0, 3R, 1543.0, 1994.01.
598. Ida, Katsumi; Miura, Yukitoshi; Itoh, Sanae-I; Hofmann, J; Fukuyama, Atsushi; Hideuma, Shigeru; Sanuki, Heiji; Idei, Hiroshi; Yamada, Hiroshi; Iguchi, Harukazu; , Physical mechanism determining the radial electric field and its radial structure in a toroidal plasma, Journal of Plasma and Fusion Research, Vol. 1, No. , Pages , 1994.01.
599. Hiroshi Idei, Shin Kubo, Minoru Hosokawa, Harukazu Iguchi, Kunizo Ohkubo, Teruyuki Sato, Electron cyclotron emission from optically thin plasma in compact helical system, Japanese Journal of Applied Physics, 10.1143/JJAP.33.1543, 33, 3R, 1543-1549, 1994.01, [URL], A frequency spectrum of second harmonic electron cyclotron emission was observed for an optically thin plasma produced by fundamental electron cyclotron heating in a compact helical system. A radial electron temperature profile deduced from this spectrum neglecting the multiple reflections effect shows a clear difference from that measured by Thomson scattering. We relate the spectrum with the electron temperature profile by the modified emission model including the scrambling effect. The scrambling effect results from both mode conversion and change in the trajectory due to multiple reflections of the emitting ray at the vessel wall. The difference between the two temperature profiles is explained well by using the modified emission model. Reconstruction of the electron temperature profile from the spectrum using this model is also discussed..
600. Hiroshi Idei, K. Ida, H. Sanuki, S. Kubo, H. Yamada, H. Iguchi, S. Morita, S. Okamura, R. Akiyama, H. Arimoto, K. Matsuoka, K. Nishimura, K. Ohkubo, C. Takahashi, Y. Takita, K. Toi, K. Tsumori, I. Yamada, Formation of positive radial electric field by electron cyclotron heating in compact helical system, Physics of Plasmas, 10.1063/1.870488, 1, 10, 3400-3406, 1994.01, [URL], The radial electric field is driven to positive value by off-axis second harmonic electron cyclotron heating (ECH) in the Compact Helical System [Plasma Physics and Controlled Nuclear Fusion Research 1988, Nice (International Atomic Energy Agency, Vienna, 1989), Vol. II, p. 411]. The observed positive electric field is associated with the outward particle flux enhanced with ECH. The enhanced particle flux triggered by the production of the electrons accelerated perpendicularly to the magnetic field with ECH results in the change of the electric field..
601. Idei, H; Kubo, S; Hosokawa, M; Iguchi, H; Ohkubo, K; Sato, T; , Effect on multiple reflection of electron cyclotron emission from optically thin plasmas, Proc. of 8th joint workshop on electron cyclotron emission and electron cyclotron resonance heating, 361.0-367.0, IPP--III/186(V.2) , 1993.11.
602. H Idei, K Ida, H Sanuki, H Yamada, H Iguchi, S Kubo, R Akiyama, H Arimoto, M Fujiwara, M Hosokawa, K Matsuoka, S Morita, K Nishimura, K Ohkubo, S Okamura, S Sakakibara, C Takahashi, Y Takita, K Tsumori, I Yamada, Transition of the radial electric field by electron cyclotron heating in the CHS heliotron/torsatron, Physical review letters, 71.0, 14.0, Article No. 2220, 1993.10.
603. Idei, H; Ida, K; Sanuki, H; , Bifurcation of radial electric field in the low-aspect-ratio heliotron/torsatron CHS, EPS conference on controlled fusion and plasma physics, 27.0, 6.0, 393.0-396.0, 1993.07, There are generally two stable states in the stellarator plasmas which are called the ion and the electron roots. In a stellarator reactor, it is an important scenario to attain the electron root with higher energy confinement time through heating electrons in the startup phase. In Heliotron-E device, the radial electric field at r ≅ 0.7-0.9a is found to be positive (the electron root) for the low density plasma (ne<1x1013 cm-3), and negative (the ion root) for the high density plasma (ne>2x1013 cm-3). In Wendelstein VII-A stellarator, the observed electric field in the plasma with electron cyclotron heating (ECH) (ne ∼ 5x1013 cm-3) is consistent with a theoretical prediction. In CHS, the observed radial electric field is negative in the typical neutral beam (NB) heated plasmas. The electric field becomes more negative near the plasma edge for the higher electron density. It is generally observed that ECH has an effect of density pump-out both in tokamaks and stellarators. In CHS, it is observed that the particle confinement becomes worse in the plasma with second harmonic ECH at low field side resonance than at high field side one. One of the candidates for the mechanism of the density pump-out is the outward flux due to the poor confinement of perpendicularly accelerated electrons by ECH. In this paper, we present the bifurcation of the radial electric field from non of the radial electric field from negative to positive value triggered by enhancing the electron particle flux with ECH..
604. H. Idei, K. Ida, H. Sanuki, H. Yamada, H. Iguchi, S. Kubo, R. Akiyama, H. Arimoto, M. Fujiwara, M. Hosokawa, K. Matsuoka, S. Morita, K. Nishimura, K. Ohkubo, S. Okamura, S. Sakakibara, C. Takahashi, Y. Takita, K. Tsumori and I. Yamada , Transition of radial electric field by electron cyclotron heating in stellarator plasmas, National Inst. for Fusion Science, NIFS--230, 1993.06, The transition of a radial electric field from a negative to a positive value is observed in Compact Helical System when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. The observed threshold for the enhanced particle flux required to cause the transition is compared with a theoretical prediction..
605. Iguchi, H; Kubo, S; Idei, H; , Hollow density profile and particle transport of ECH plasmas in the low-aspect-ratio heliotron/torsatron CHS, Proc. of the 20th. EPS conference on controlled fusion and plasma physics, 17C, I, I-381-I-384, 1993.01.
606. Hiroshi Idei, K. Ida, H. Sanuki, H. Yamada, H. Iguchi, S. Kubo, R. Akiyama, H. Arimoto, M. Fujiwara, M. Hosokawa, K. Matsuoka, S. Morita, K. Nishimura, K. Ohkubo, S. Okamura, S. Sakakibara, C. Takahashi, Y. Takita, K. Tsumori, I. Yamada, Transition of the radial electric field by electron cyclotron heating in the CHS heliotron/torsatron, Physical Review Letters, 10.1103/PhysRevLett.71.2220, 71, 14, 2220-2223, 1993.01, [URL], The transition of a radial electric field from a negative to a positive value is observed in the compact helical system when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. Existence of the threshold for the enhanced particle flux required to cause the transition is experimentally certified. The observed threshold is compared with a theoretical prediction..
607. MATSUOKA, K; YAMADA, H; IGUCHI, H; IDA, K; MORITA, S; OKAMURA, S; NISHIMURA, K; SANUKI, H; ITOH, K; AKIYAMA, R; ARIMOTO, H; HANATANI, K; HOSOKAWA, M; IDEI, H; KANEKO, O; KUBO, S; KUMAZAWA, R; OZAKI, T; SAGARA, A; SAKAKIBARA, S; TAKAHASHI, C; TAKEIRI, Y; TAKITA, Y; TOI, K; TSUMORI, K; UEDA, M; YAMADA, I; WATARI, T; FUJIWARA, M, RESULTS FROM THE CHS DEVICE, PLASMA PHYSICS AND CONTROLLED FUSION, 34, 13, 1909-1915, 1992.12.
608. A. Sagara, N. Noda, R. Akiyama, H. Arimoto, H. Idei, H. Iguchi, O. Kaneko, T. Kohmoto, S. Kubo, N. Matsunami, K. Matsuoka, S. Morita, O. Motojima, K. Nishimura, S. Okamura, J. Rice, T. Shoji, C. Takahasi, Y. Takita, M. Ueda, H. Yamada, I. Yamada, An analytical erosion model for divertor plates and limiter experiments in CHS, JOURNAL OF NUCLEAR MATERIALS, 196.0, 271.0-275.0, 1992.12, A self-consistent analytical solution for net erosion of a divertor plate which is set perpendicular to magnetic field lines is presented. The primary flux profile of hydrogen and impurities except redepositing particles is externally given as well as the return ratio of sputtered atoms to the plate. In the direction along the divertor trace, all conditions are uniform. The ionization mean free path is assumed constant to simplify equations. The analytical solution is compared with net erosion experiments carried out in compact helical system (CHS) by exposing a graphite target to a neutral beam heated plasma column introduced perpendicularly to the target along the magnetic field lines through a 2 cm slit opened on a graphite limiter. After exposure to 98 discharges, the target surface is analyzed with Rutherford backscattering method. Deposition profiles of Ti and O impurities are very well explained with the analytical predictions..
609. A. Sagara, N. Noda, R. Akiyama, H. Arimoto, Hiroshi Idei, H. Iguchi, O. Kaneko, T. Kohmoto, S. Kubo, N. Matsunami, K. Matsuoka, S. Morita, O. Motojima, K. Nishimura, S. Okamura, J. Rice, T. Shoji, C. Takahasi, Y. Takita, M. Ueda, H. Yamada, I. Yamada, An analytical erosion model for divertor plates and limiter experiments in CHS, Journal of Nuclear Materials, 10.1016/S0022-3115(06)80044-9, 196-198, C, 271-275, 1992.12, [URL], A self-consistent analytical solution for net erosion of a divertor plate which is set perpendicular to magnetic field lines is presented. The primary flux profile of hydrogen and impurities except redepositing particles is externally given as well as the return ratio of sputtered atoms to the plate. In the direction along the divertor trace, all conditions are uniform. The ionization mean free path is assumed constant to simplify equations. The analytical solution is compared with net erosion experiments carried out in compact helical system (CHS) by exposing a graphite target to a neutral beam heated plasma column introduced perpendicularly to the target along the magnetic field lines through a 2 cm slit opened on a graphite limiter. After exposure to 98 discharges, the target surface is analyzed with Rutherford backscattering method. Deposition profiles of Ti and O impurities are very well explained with the analytical predictions..
610. T. Shoji, A. Sagara, N. Noda, M. Hosokawa, K. Ida, Hiroshi Idei, H. Iguchi, O. Kaneko, S. Kubo, K. Matsuoka, S. Morita, K. Nishimura, S. Okamura, C. Takahashi, Y. Takeiri, H. Yamada, Edge plasma control by rf electric field in the compact helical system (CHS), Journal of Nuclear Materials, 10.1016/S0022-3115(06)80150-9, 196-198, C, 824-828, 1992.12, [URL], The reduction of the plasma heat flux on the material limiter and the stabilization of the fluctuations at the plasma boundary by the use of an rf ponderomotive potential barrier on the limiter (rf limiter) have been demonstrated in the compact helical system (CHS) for the ECH heated plasma. The rf current on a graphite limiter surface along magnetic field lines produces a ponderomotive potential barrier, which is large at the limiter edges. The high heat load on the limiter edges, which is measured using an infrared TV camera, has been shown to be reduced by an rf power of 1.4 kW at a frequency of 10 MHz (ωci<ωωce). Another remarkable effect of the ponderomotive potential barrier on the limiter that has been observed is the suppression of density fluctuations (<100 kHz) at the plasma boundary..
611. H. Yamada, K. Ida, H. Iguchi, S. Morita, O. Kaneko, H. Arimoto, M. Hosokawa, H. Idei, S. Kubo, K. Matsuoka, K. Nishimura, S. Okamura, Y. Takeiri, Y. Takita, C. Takahashi, K. Hanatani, H. C. Howe, S. P. Hirshman, D. K. Lee, Shafranov shift in the low aspect ratio heliotron/torsatron Compact Helical System, Nuclear Fusion, 10.1088/0029-5515/32/1/I03, 32, 1, 25-32, 1992.12, [URL], The MHD equilibrium properties of neutral beam heated plasmas have been experimentally investigated in the Compact Helical System (CHS)-a low aspect ratio (Ap ∼ 5) heliotron/torsatron. This configuration is characterized by a strong breaking of helical symmetry. The radial profiles measured by various diagnostics have shown a significant Shafranov shift due to the plasma pressure. The deviation of the magnetic axis from is vacuum position has become as large as 50% of the minor radius. When the three-dimensional equilibrium code VMEC is used to reconstruct the equilibrium from the experimental data, the result is in good agreement with the experimentally observed Shafranov shift as well as with the diamagnetic pressure in plasmas with 〈β〉 ≤ 1.2% and β0 ≤ 3.3%. This beta values corresponds to half of the conventional equilibrium β limit defined by the Shafranov shift reaching a value of half of the minor radius. Although tangential neutral beam injection causes pressure anisotropies, p ||/p ≤ 3, the description of the equilibrium assuming isotropic pressure is consistent with the experiment..
612. Toi, K., Okamura, S., Iguchi, H., Yamada, H., Morita, S., Sakakibara, S., Ida, K., Nishimura, K., Matsuoka, K., Akiyama, R., Arimoto, H., Fujiwara, M., Hosokawa, M., Idei, H., Kaneko, O., Kubo, S., Sagara, A., Formation of an H-mode-like transport barrier in the CHS heliotron/torsatron, Plasma Physics and Controlled Nuclear Fusion Research , 2, 461-467, 1992.09.
613. Yamada, H., Morita,S., Ida, K., Okamura, S., Iguchi,H., Sakakibara, S., Nishimura, K., Akiyama,R., Arimoto, H., Fujiwara, M., Hanatani, K., Hirshman, S. P., Ichiguchi, K., Idei, H., Kaneko, O., Kawamoto, T., Kubo, S., Lee, D. K., Matsuoka, K., Motojima, O., MHD and confinement characteristics in the high-beta regime on the compact helical system low aspect ratio heliotron/torsatron, Plasma Physics and Controlled Nuclear Fusion Research , 2, 493-500, 1992.09.
614. Morita, Sakae; Yamada, H; Iguchi, H; Adati, K; Akiyama, R; Arimoto, H; Fujiwara, M; Hamada, Y; Ida, K; Idei, H; , A role of neutral hydrogen in CHS plasmas with reheat and collapse and comparison with JIPP T-IIU tokamak plasmas, Conference on Plasma Physics and Controlled Nuclear Fusion Research of the Fourteenth IAEA held in Wuerzburg, Germany, 30 Sep.-7 Oct. 1992, Vol. 1, No. , Pages , 1992.09, Results are described on NBI plasmas of the Compact Helical System (CHS). An increase in the stored energy, which is called plasma 'reheat' is observed with density peaking when gas puffing is turned off in the high density region. A plasma collapse with large increase in radiation loss occurs even in discharges whose Z(sub eff) values (typically, less than 2-3) do not show any increase when the gas puffing is continued. Both phenomena are basically explained by the edge electron temperature due to the difference in the amount of edge hydrogen neutrals. After turning off the gas puffing, the central electron density n(sub e 0) shows an increase of 80 percent and the density peaking factor (n(sub e 0)/bar-n(sub e)) changes from 1.0 to 2.0 in typical cases, and a high inward velocity of the impurities appears (v = 20 m/s). The accumulation is studied in relation to the poloidal rotation and the edge temperature. These results are compared with results from plasmas with IOC- and H-modes in the JIPPT-IIU tokamak..
615. Shoji, T; Sagara, A; Noda, N; Hosokawa, M; Ida, K; Idei, H; Iguchi, H; Kaneko, O; Kubo, S; Matsuoka, K; , Edge plasma control by rf electric field in the compact helical system (CHS), JOURNAL OF NUCLEAR MATERIALS, 196.0, 824.0-828.0, 1992.01.
616. Okamura, S; Nishimura, K; Hanatani, K; Amano, T; Arimoto, H; Fujiwara, M; Hosokawa, M; Ida, K; Idei, H; Iguchi, H; , Heating experiments using neutral beams with variable injection angle and ICRF waves in CHS, Presented at the 14th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Wuerzburg, Germany, 30 Sep.-7 Oct. 1992, 1992.01.
617. H Yamada, K Ida, H Iguchi, S Morita, O Kaneko, H Arimoto, M Hosokawa, H Idei, S Kubo, K Matsuoka, K Nishimura, S Okamura, Y Takeiri, Y Takita, C Takahashi, K Hanatani, HC Howe, SP Hirshman, DK Lee, Shafranov shift in the low aspect ratio heliotron/torsatron compact helical system, NUCLEAR FUSION, Vol. 32, No. 1, Pages 25, 1992.01.
618. K. Matsuoka, H. Yamada, H. Iguchi, K. Ida, S. Morita, S. Okamura, K. Nishimura, H. Sanuki, K. Itoh, R. Akiyama, H. Arimoto, K. Hanatani, M. Hosokawa, Hiroshi Idei, O. Kaneko, S. Kubo, R. Kumazawa, T. Ozaki, A. Sagara, S. Sakakibara, C. Takahashi, Y. Takeiri, Y. Takita, K. Toi, K. Tsumori, M. Ueda, I. Yamada, T. Watari, M. Fujiwara, Results from the CHS device, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/34/13/020, 34, 13, 1909-1915, 1992.01, [URL], This paper reviews recent experimental results from compact helical system (CHS), a heliotron/torsatron type device with a low aspect ratio of 5. Transport phenomena are discussed through analyses of MHD equilibrium, thermal/particle diffusivity and viscosity. It is seen that transport is dominated by anomalous processes which are thought to be due to electrostatic fluctuations. On the basis of these results, optimization of confinement by shifting the vacuum magnetic axis is briefly discussed..
619. A. Sagara, T. Shoji, N. Noda, M. Fujiwara, M. Hosokawa, K. Ida, H. Idei, H. Iguchi, O. Kaneko, A. Karita, S. Kubo, K. Matsuoka, O. Motojima, S. Morita, K. Nishimura, S. Okamura, K. Okazaki, T. Ozaki, K. Sato, H. Sanuki, C. Takahasi, Y. Takeiri, Y. Takita, K. Tsuzuki, H. Yamada, Temperature-controlled graphite limiter experiments in CHS plasma, JOURNAL OF NUCLEAR MATERIALS, 167.0, 3.0, 174.0-179.0, 1990.12.
620. A. Sagara, T. Shoji, N. Noda, M. Fujiwara, M. Hosokawa, K. Ida, Hiroshi Idei, H. Iguchi, O. Kaneko, A. Karita, S. Kubo, K. Matsuoka, O. Motojima, S. Morita, K. Nishimura, S. Okamura, K. Okazaki, T. Ozaki, K. Sato, H. Sanuki, C. Takahasi, Y. Takeiri, Y. Takita, K. Tsuzuki, H. Yamada, Temperature-controlled graphite limiter experiments in CHS plasma, Journal of Nuclear Materials, 10.1016/0022-3115(90)90041-K, 176-177, C, 174-179, 1990.12, [URL], A movable graphite limiter with an internal heater has been installed in the heliotron/torsatron type compact helical system (CHS). Comparing discharges with and without the limiter the origin of major impurities and the role of the limiter are discussed. Infrared TV measurements reveal that there are two hot spots on the limiter due to heat loading and their temperatures depend on the electron density and/or the magnetic field direction. Limiter temperature dependence of measured CH/Hγ, CI, CII, OII, CH+3, OV and total radiation loss is compared. From these experiments it is concluded that CH4 molecules produced chemically on the limiter are presumed to recycle rapidly near the limiter and both carbon and oxygen impurities result probably from CO produced chemically on the limiter with oxygen which is predominant in CHS and originates mostly from the first wall. At surface temperatures above 900 ° C the limiter effect on impurities is observable in the main plasma..
621. O. KANEKO, S. KUBO, K. NISHIMURA, T. SHOJI, M. HOSOKAWA, K. IDA, H. IDEI, H. IGUCHI, K. MATSUOKA, S. MORITA, N. NODA, S. OKAMURA, T. OZAKI, A. SAGARA, H. SANUKI, C. TAKAHASHI, Y. TAKEIRI, Y. TAKITA, K. TSUZUKI, H. YAMADA, T. AMANO, A. ANDO, M. FUJIWARA, K. HANATANI, A. KARITA, T. KOHMOTO, A. KOMORI, K. MASAI, T. MORISAKI, O. MOTOJIMA, N. NAKAJIMA, Y. OKA, M. OKAMOTO, S. SOBHANIAN, J. TODOROKI , Confinement characteristics of high power heated plasma in CHS, Proc. 13th Int. Conf. on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 2.0, 473.0, IAEA-CN-53/C-I-4
, 1990.10, High-power-heated discharges in CHS are studied from the view point of optimizing the plasma performance in low-aspect-ratio heliotron/torsatron ( R/a= 100 cm/ 20 cm ) . With tangential neutral injection, the stored energy, especially the electron temperature, strongly depends on the location of magnetic axis. The optimal magnetic axis (R_{ax}=92cm) , however, does not coincide with the location where the theory predicts the most favorable drift surface (R_{ax}=88cm) . High beta plasma (< B >=1.5%) can also be obtained in inward shifted configurations at the toroidal field B_t=0.47-0.6T. The optimal location is also R_{ax}=92cm although the observed plasma center shifts outward by several cm due to Shafranov shift. So far, the obtained stored energy stays in the range that the LHD scaling predicts. This fact means that the performance of CHS. i.e. Iow-aspect-ratio helical system, is as good as other helical systems . The induced currents are observed both in ECH and NBH discharges. In NBH discharges, the currents consist of bootstrap and OHKAWA currents. In fact, the current reversal is often observed when the density is high or B_t is low, which is consistent with the theory of bootstrap current in the plateau regime..
622. Kubo, Shin; Hosokawa, Minolu; Takita, Y; Idei, H; , Power deposition during ECH in CHS, Plasma Physics and Controlled Nuclear Fusion: Next Generation Experiments in Helical Systems, 1, 240-243, 1990.01.
623. Matsuoka, Keisuke; Fujiwara, Masami; Harris, JH; Hosokawa, Minolu; Ida, Katsumi; Idei, H; Iguchi, Harukazu; Kaneko, Osamu; Kubo, Shin; Masai, K; , Review of CHS experiment, Plasma Physics and Controlled Nuclear Fusion: Next Generation Experiments in Helical Systems, 1, 93-96, 1990.01.
624. K Matsuoka, S Kubo, M Hosokawa, Y Takita, S Okamura, N Noda, H Yamada, H Iguchi, K MASAI, S MORITA, K IDA, H IDEI, C TAKAHASHI, K NISHIMURA, T SHOJI, H SANUKI, M FUJIWARA, Y ABE, T AMANO, A ANDO, T AOKI, DG BI, J FUJITA, S HIDEKUMA, T KAMIMURA, O KANEKO, T KAWAMOTO, A MOHRI, A NISHIZAWA, S TANAHASHI, J TODOROKI, K TSUZUKI, K YAMAZAKI, Confinement study in compact helical system (CHS), Plasma Physics and Controlled Nuclear Fusion Research (Proc. 12th Int. Conf., Nice, 1988), 2.0, 411.0-417.0, 1988.01.

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