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makoto hasegawa Last modified date：2024.04.02

Associate Professor / Division of Nuclear Fusion Dynamics / Research Institute for Applied Mechanics


Papers
1. Makoto HASEGAWA, Aki HIGASHIJIMA, Ichiro NIIYA, Kazuaki HANADA, Hiroshi IDEI, Takeshi IDO, Ryuya IKEZOE, Takumi ONCHI, Kengo KURODA and Daisuke SAKURAI, QUEST Database for Tokamak Big Data, Plasma and Fusion Research, 10.1585/pfr.18.1305048, 18, 1305048-1-1305048-4, 2023.05, A database has been developed to provide a highly efficient data analysis environment by registering various types of data obtained in the QUEST (Q-shu University Experiment with Steady-State Spherical Tokamak) experiments and providing the data to researchers through standard SQL query output. In conventional experiments, measurements are usually obtained using several instruments, and the results are often stored separately in proprietary formats. An analysis to collect distributed files and convert them into appropriate formats individually was necessary, which led to a decrease in analysis efficiency. In order to build a system to centrally store and provide data, we constructed new servers, each for registering data in a database and for extracting data from the database and visualizing the data. As a result, various real-time monitoring data can be registered in the database, and data retrieval for analysis can be performed easily with a unified user interface. The construction of this database has made it possible to easily retrieve real-time monitoring data and a wide variety of table data, enabling analysis from a new perspective, and improving analysis efficiency..
2. Kuroda, K., Raman, R., Hasegawa, M.., Onchi, T., Hanada, K., Ono, M., Nelson, B.A., Rogers, J., Ikezoe, R., Idei, H., Ido, T., Mitarai, O., Nagata, M., Kawasaki, S., Nagata, T., Higashijima, A., Shimabukuro, S., Niiya, I., Sekiya, I., Kojima, S., Nakamura, K., Takase, Y., Murakami, S., Improvements to the High-Field-Side Transient CHI System on QUEST, JOURNAL OF FUSION ENERGY, 10.1007/s10894-022-00338-4, 41, 2, 2022.12, Transient coaxial helicity injection (CHI) is a promising candidate for solenoid-free plasma current start-up in a low-aspect-ratio tokamak in support of developing fully non-inductive scenarios. The aim of the transient CHI research on QUEST is to develop a reactor-relevant CHI design. On QUEST, a CHI discharge is initiated by driving current along magnetic field lines that connect an electrically insulated electrode plate (which is referred to as a bias electrode) to a vessel component at the bottom region of the spherical tokamak. In the first application of CHI on QUEST, the electrically insulated electrode plate was biased with respect to the outer vessel in a configuration referred to as low-field-side (LFS) injection. To maintain a narrow injector flux footprint width throughout the discharge, QUEST is now developing a high-field-side (HFS) injection configuration, in which the electrically insulated electrode plate is biased with respect to the inner vessel components. Through the implementation of a CHI-dedicated gas injection system, studies in the HFS injection configuration have now demonstrated good magnetic flux evolution into the vacuum vessel. Toroidal currents up to 43 kA have been achieved, and the generated current has increased in proportion to the magnetic flux connecting the electrodes. These results which show agreement with the CHI-scaling suggest that much higher levels of toroidal current can be generated on QUEST in an optimized CHI system in which the magnetic flux connecting the CHI electrodes is further increased..
3. R. Raman, K. Kuroda, K. Hanada, M. Ono, M. Hasegawa, T.Onchi, R. Ikezoe, H. Idei, T. Ido, J.A. Rogers, Design Considerations for the Implementation of a High-Field Side Transient CHI System on QUEST, IEEE Transactions onPlasma Science, https://doi.org/10.1109/TPS.2022.3193069, (1-6),2022, 2022.08, Transient coaxial helicity injection (T-CHI), a method first developed on the small helicity injected torus (HIT-II) experiment and then validated on the much larger National Spherical Torus Experiment (NSTX) device, is a method to initiate an inductive-like tokamak plasma discharge without reliance on the central solenoid. A CHI discharge is initiated by driving current along magnetic flux that connects the inner and outer divertor plates on one end of the tokamak. To permit this, on both HIT-II and NSTX, toroidal ceramic insulators were used to electrically separate the inner and outer vessel components. The use of such large toroidal vacuum insulators may not be easy to implement in reactors. To address this issue, the Q-shu University experiments with steady-state spherical tokamak (ST) (QUEST) is developing a reactor-relevant CHI configuration in which one of the divertor plates is electrically insulated from the rest of the vessel. The first application of T-CHI on QUEST biased the CHI electrode to the outer vessel. While the CHI discharges could be easily generated, it was found that as the discharge filled the vessel, the separation distance between the injector magnetic flux footprints widened, a condition that is not favorable for the generation of closed flux surfaces. Biasing the electrode to the inner wall is a configuration similar to that used on NSTX and HIT-II, but initial testing in this configuration has proved to be challenging. The design described here overcomes the present limitation by locating the CHI electrode much closer to the CHI injector flux coil and using an NSTX-like gas injection manifold to enable high-field-side T-CHI startup on QUEST. The concepts described in this article should also benefit the future implementation of T-CHI systems in other tokamaks and spherical tokamaks..
4. Makoto Hasegawa, Daisuke Sakurai, Aki Higashijima, Ichiro Niiya, Keiji Matsushima, Kazuaki Hanada, Hiroshi Idei, Takeshi Ido, Ryuya Ikezoe, Takumi Onchi, Kengo Kuroda, Towards automated gas leak detection through cluster analysis of mass spectrometer data, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2022.113199, 180, 113199, 2022.06, In order to generate high-performance plasma for future fusion power generation, it is desirable to keep high quality vacuum during experiment. Mass spectrometer is commonly used to monitor the vacuum quality and to record the amount of atoms and molecules in the vacuum vessel. Leak is the most serious accident to avoid that can nullify an experiment and even harm researchers. Detecting leaks are ever more important since it can be easily overlooked, e.g., when the deterioration in the vacuum degree is modest. This forces the researcher to carefully observe the vacuum and mass spectrometer data. This article presents a way to suggest potential leaks in the vacuum vessel by analyzing mass spectrometer data. This is done by utilizing the Euclidean distance between composition ratios at different times for the clustering using the daily composition ratio. We show that our cluster analysis is an effective way of separating these two cases, which results in a semi-automatic determination of leaks is more efficient than the current norm, which is to check many measures to find a small abnormality in the data manually. We plan further model improvements for long-term evaluation..
5. Kazuo NAKAMURA, Yifan ZHANG, Takumi ONCHI, Hiroshi IDEI, Makoto HASEGAWA, Kazutoshi TOKUNAGA, Kazuaki HANADA, Hirotaka CHIKARAISHI, Osamu MITARAI, Shoji KAWASAKI, Aki HIGASHIJIMA, Takahiro NAGATA, Shun SHIMABUKURO, Quaternion Analysis of Transient Phenomena in MatrixConverter Based on Space-Vector Modulation, Plasma and FusionResearch, https://doi.org/10.1585/pfr.17.2405025, 17, 2022 Volume 17 Pages 2405025, 2022.04, The space vector of an output voltage can be rotated smoothly in a matrix converter. However, a zero-sequence component appears causing problems in the load, such as a motor. A quaternion is a four-dimensional hypercomplex number with an imaginary part that can simultaneously represent and deal with three-phase voltages. In addition, the quaternion is expressed in the exponential form; thus, it can easily represent the space vector rotation. Two zero configurations were used to optimize the ripple characteristics in fictitious pulse-width-modulated voltage-source inverter. The two zero configurations are used to remove the zero-sequence component from the matrix converter. The quaternion can be differentiated in time as well as rotate in space. Therefore, it is used to analyze transient phenomena in the matrix converter's rise-up and rise-down phases, and the switching's transition phase..
6. Shinichiro Kojima, Kazuaki Hanada, Hiroshi Idei, Takumi Onchi, Ryuya Ikezoe, Yoshihiko Nagashima, Makoto Hasegawa, Kengoh Kuroda, Kazuo Nakamura, Aki Higashijima, Takahiro Nagata, Shoji Kawasaki, Shun Shimabukuro, Hatem Elserafy, Masaharu Fukuyama, Akira Ejiri, Taiichi Shikama, Nao Yoneda, Ryota Yoneda, Tsuyoshi Kariya, Yuichi Takase, Sadayoshi Murakami, Nicola Bertelli and Masayuki Ono, Observation of second harmonic electron cyclotron resonance heating and current-drive transition during noninductive plasma start-up experiment in QUEST, Plasma Physics and Controlled Fusion, https://doi.org/10.1088/1361-6587/ac1838, 63, 105002, 2021.08, Noninductive plasma current start-up using 2nd harmonic electron cyclotron resonance heating (ECRH) with oblique radio frequency (RF) injection is demonstrated in a Q-shu University experiment with steady-state spherical tokamak. A strong transition was observed in the heating and plasma current ramp-up. The initial bulk electron heating regime exhibits Tebulk ∼ 140 eV and no hard x-ray (HXR) emission with a low Ip of ∼15 kA; it abruptly transitions to a regime that exhibits a low Tebulk of ∼10 eV and a strong HXR emission with a high Ip of ∼50 kA. This behavior is distinctly different from that observed in previous fundamental ECRH experiments. The mechanism of the heating and current drive transition are investigated considering wave power absorption and plasma power balance. The results indicate that the transition is caused by the favorable heating of tail electrons where the RF power absorption at the 2nd harmonic increases nearly linearly with Tetail, while the power transfer from the tail electrons to the bulk electrons decreases with 1/Tetail 0.5. This causes a rapid transition to a state with high Tetail while reducing Tebulk towards colder ion temperature. The understanding of the transition mechanism
helps to consider plasma current start-up using 2nd harmonic ECRH for tokamak reactors such as JT-60 SA and ITER.
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7. K. Hanada, N. Yoshida, M. Hasegawa, M. Oya, Y. Oya, I. Takagi, A. Hatayama, T. Shikama, H. Idei, Y. Nagashima, R. Ikezoe, T. Onchi, K. Kuroda, S. Kawasaki, A. Higashijima, T. Nagata, S. Shimabukuro, K. Nakamura, S. Murakami, Y. Takase, X. Gao, H. Liu, and J. Qian, Overview of recent progress on steady state operation of all-metal plasma facing wall device QUEST
, Nuclear Materials and Energy, https://doi.org/10.1016/j.nme.2021.101013, 27, 101013, 2021.06, QUEST (Q-shu university experiment with steady state spherical tokamak) is a midsize spherical tokamak capable of steady-state operation, comprising all-metal plasma-facing walls and a hot wall (HW) to address issues pertaining to fuel particle balance. The HW was installed summer 2014. Quantitative analysis pertaining to the HW at 373 K is carried out, and clarify the quantitative impact of shot history that obviously appears in wall stored hydrogen just before the discharge at the wall temperature. The model indicates the plasma-induced deposition layer play an essential role in fuel particle balance. A clear temperature dependence of fuel recy-cling was observed using outgassing just after plasma termination and played an essential role in regulation of particle balance. Consequently, long duration discharges lasting more than 1 h has been obtained at wall tem-perature, TW
8. Kengoh KURODA, Roger RAMAN, Makoto HASEGAWA, Takumi ONCHI, Brian A. NELSON, John ROGERS, Osamu MITARAI, Kazuaki HANADA, Masayuki ONO, Thomas JARBOE, Masayoshi NAGATA, Hiroshi IDEI, Takeshi IDO, Ryuya IKEZOE, Shoji KAWASAKI, Takahiro NAGATA, Aki HIGASHIJIMA, Shun SHIMABUKURO, Ichiro NIIYA, Canbin HUANG, Shinichiro KOJIMA, Akihiro KIDANI, Takahiro MURAKAMI, Kazuo NAKAMURA, Yuichi TAKASE, Sadayoshi MURAKAMI, Initial Results from High-Field-Side Transient CHI Start-Up on QUEST, Plasma and Fusion Research , https://doi.org/10.1585/pfr.16.2402048, 16, 2402048, 2021.02, Transient coaxial helicity injection (t-CHI) current start-up using a new design simple electrode configuration has been implemented on the QUEST. Discharges injected from the low field side (LFS) and from the high field side (HFS) were examined. Compared to the LFS injection case, the HFS injection has the advantages of providing access to a higher toroidal field and better controlling the location of the injector flux footprint location. Although the present PF coils on QUEST are not well positioned to form the injector flux on the HFS
injector region and there has been a frequent occurrence of the spurious arcs, known as absorber arcs, HFS injection has shown flux evolution in a shape that is suitable for the formation of closed flux surfaces. The discharges were improved by installing an in-vessel-coil and adding a new cylindrical electrode to the existing CHI electrode. The results show that the new cylindrical electrode allowed the flux to evolve stably while allowing both the inner and the outer injector flux footprint to remain in the vicinity of the cylindrical electrode. This
configuration which inherently generates a narrow injector flux footprint width resulted in discharges that strongly suggested the persistence of the CHI generated plasma after the injector current was reduced to zero. These studies have informed us of the need to improve the CHI gas injection system so that the absorber arcs could be better controlled in the HFS injection configuration..
9. Makoto HASEGAWA, Kazuaki HANADA, Naoaki YOSHIDA, Hiroshi IDEI, Takeshi IDO, Yoshihiko NAGASHIMA, Ryuya IKEZOE, Takumi ONCHI, Kengoh KURODA, Shoji KAWASAKI, Aki HIGASHIJIMA, Takahiro NAGATA, Shun SHIMABUKURO and Kazuo NAKAMURA, Extension of Operation Region for Steady State Operation on
QUEST by Integrated Control with Hot Walls, Plasma and Fusion Research, 10.1585/pfr.16.2402034, 16, 2402034, 2402034-1-2402034-8, 2021.01, [URL], The controllability of particle supply during long-term discharge in a high-temperature environment was investigated at the Q-shu University Experiment with steady state spherical tokamak (QUEST). QUEST has a high-temperature wall capable of active heating and cooling as a plasma-facing wall. With this hot wall, a temperature rise test was conducted with 673K as the target temperature. It was confirmed that the hot wall could maintain the temperature above 600 K. Feedback control of particle fueling was conducted to control Hα
emission, which is closely related to influx to the wall. Using this particle fueling control and setting the hot wall temperature to 473 K, it was possible to obtain a discharge of more than 6 h. In this discharge, the fueling rate of particles decreased with time, and finally became zero, losing the particle fueling controllability. However, as soon as the cooling water started to flow through the hot wall, particles could be supplied again, and controllability was restored. Thus, indicating that temperature control of the plasma first wall is important even in the high temperature environment of 473K to control particle retention of the wall..
10. Shinichiro KOJIMA, Hatem ELSERAFY, Kazuaki HANADA, Hiroshi IDEI, Ryuya IKEZOE, Yoshihiko NAGASHIMA, Makoto HASEGAWA, Takumi ONCHI, Kengoh KURODA, Kazuo NAKAMURA, Takahiro MURAKAMI, Masaharu FUKUYAMA, Ryoya KATO, Ryota YONEDA, Masayuki ONO, Akira EJIRI, Yuichi TAKASE, Sadayoshi MURAKAMI, Parametric Decay Wave Observation in HFS X-Mode Injection in QUEST, Plasma and Fusion Research, https://doi.org/10.1585/pfr.15.2402063, 15, 2402063, 2402063-1-2402063-6, Volume 15, 2402063 (2020)
, 2020.08, [URL], The parametric decay wave (PDW) caused by three-wave parametric decay process was measured in a plasma-injecting X-mode electron cyclotron wave (ECW) from the high field side (HFS) of the Q-shu University Experimental Steady-State Spherical Tokamak (QUEST). The intensity of the low-frequency PDW on the HFS X-mode injection was significantly enhanced over the O-mode ECW injection from the low field side (LFS), where the mode conversion to electron Bernstein wave (EBW) was not expected. As the comparison was executed using plasmas with the same magnetic field and injection power, the wave injection method was considered as the primary cause of the difference in the PDW excitation. The frequency range of the low-frequency PDW was consistent with that of the lower hybrid wave (LHW) range, which was expected to be excited during the mode conversion to EBW. The low-frequency PDW intensity evolved in response to the plasma density, plasma current and injection power. This observation suggests that the low-frequency PDW intensity is a reliable indicator for the efficient mode conversion to EBW..
11. 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, https://doi.org/10.1016/j.heliyon.2020.e04214, 6, e04214, accepted, 2020.06, As technology has improved in recent years, it has become possible to create new valuable functions by combining various devices and sensors in a network. This concept is referred to as the Internet of Things (IoT), and predictive maintenance is a new valuable function associated with the IoT. In large-scale experimental facilities with many researchers, it is not desirable that experiments cannot be performed due to sudden failure of equipment. For this reason, it is important to predict the failure in advance based on the measurement results of sensors and to perform repairs in a planned manner. On the Q-shu University experiment with steady-state spherical tokamak (QUEST) large experimental device, it is necessary to drive a large current of 50 kA, and the diagnosis of its power line deterioration is well performed as predictive maintenance through the evaluation of its contact resistances of several micro ohms order on the network. In addition, as an example of the IoT, mechanisms to assist safe operation, such as a sound alarm system and an entrance management system, are built by sharing experimental information between devices via the network..
12. 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, 15, 2402013 , 2402013-1- 2402013-5, Volume 15, 2402013 (2020), 2020.04, [URL], Fast Ejecting System of Targeted sAmple called FESTA has been developed to carry out the measurement of
dynamic hydrogen retention by a test sample. A sample can be exposed and extracted from the targeted plasma at
any time using FESTA, however, when exposing the sample, the test chamber wall gets coated by some hydrogen
as it is open to the QUEST vacuum vessel. We refer to this as the plasma-induced background. To measure the
amount of hydrogen retained by the sample itself, the contribution from the plasma induced background must be
subtracted from the measurements. To measure the accurate dynamic retention from plasma-exposed sample, a
background subtraction model has been developed and tested. The initial testing shows that the FESTA system
and model can estimate the dynamic hydrogen retention by a target test sample..
13. 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 conbersion of high-field side injected X-modes in QUEST, Plasma Physics and Controlled Fusion, 10.1088/1361-6587/ab6903, 62, 035018, 035018-1-035018-9, Plasma Phys. Control. Fusion 62 (2020) 035018 (9pp), 2020.02, [URL], This paper presents a detailed design of the Q-shu University experimental steady state spherical tokamak's (QUEST's) high-field side (HFS) injection system for electron Bernstein wave (EBW) excitation and the results of an experimental comparison of the HFS eXtraordinary X-mode and low-field side (LFS) ordinary O-mode injection of 8.2 GHz radio frequency (RF) power. Waveguides, as an alternative to mirror polarizers for transmitting RF X-mode power from LFS to HFS for EBW conversion, were used instead of the installation of an RF mirror. Testing of LFS-to-HFS RF power transmission at 8.2 GHz, using an RG-50-type vacuum waveguide in a bench-scale device filled with SF6 gas at 0.03 Mpa, revealed that an RF power of 10.8 kW could traverse the fundamental electron cyclotron resonance layer for 60 s without breakdown. The short-length, open-ended waveguide antenna used in the HFS injection-induced wave diffraction reduced the efficiency of power delivery to the upper hybrid resonance (UHR) by approximately 7% at an electron temperature of 50 eV. The HFS injection was able to produce brighter camera images than the standard LFS injection. The location of the UHR, as estimated by measuring the density with an interferometer, agreed with its location as measured by plasma radiation low-field, side-edge positions shown by fast camera imaging. This indicates that the plasma was produced by mode-converted EBW. The HFS injection had an absorption efficiency of 96%, compared to 40% for LFS. A greater fluctuation of floating potential adjustable to the lower hybrid wave (LHW) was observed in the HFS case by installing a Langmuir probe, confirming that EBW conversion efficiency was higher in the HFS case. Moreover, after setting the poloidal field to BPF = 7.6 mT, plasma current (IP) in the HFS peaked at 1.3 kA, as opposed to 0.3 kA for LFS, despite LFS injection having a total power of 55 kW, compared to 40 kW for HFS. However, as the impurity level was comparatively high, it is believed that this IP is dominated by pressure-drive, which makes it difficult to analyze EBWCD. Finally, the line-integrated density in the HFS injection peaked at 1.6 × 1018 m−2, compared to 8 × 1017 m−2 in the LFS one..
14. 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, 10.1088/1741-4326/ab4c12, 60, 1, 016030-1- 016030-13, Nucl. Fusion 60 (2020) 016030 (13pp), 2019.12, [URL], 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..
15. Canbin HUANG, Kazuaki HANADA, Kengoh KURODA, Shinichro KOJIMA, Hiroaki FUJIYOSHI, Hiroki MIURA, Tomoki YAMADA, Hiroshi IDEI, Makoto HASEGAWA and Takumi ONCHI, Fast tangentially viewed soft X-ray imaging system based on image intensifier with microchannel plate detector on QUEST, Plasma and Fusion Research, 10.1585/pfr.14.1402128, 14, 1402128, 1402128-1-1402128-8, Volume 14, 1402128 (2019), 2019.06, [URL], A two-dimensional (2D) soft X-ray (SXR) imaging system for obtaining tangential views of plasmaproduced SXR has been installed on the QUEST tokamak. The system comprises a chevron micro-channel
plate (MCP) and a phosphor screen, which together serve as an SXR detector and image intensifier, along with a
high-speed video camera for capturing and storing image data. The system can be used in imaging mode to obtain
high spatial- and time-resolution images or in photon counting mode at an ultra-high framing rate of 100 kHz to
obtain SXR energy spectra. Here, we propose a method of in situ energy calibration based on the transmission
characteristics of a 25-µm Be filter. The proposed method was used to obtain SXR spectra in the energy range
1.5 - 3.5 keV with a core electron temperature in agreement with electron temperatures measured by the Thomson
scattering method. Furthermore, oscillations based on the modification of plasma parameters and rapid increases
in impurity radiation were detected in imaging mode. This dual-mode-compatible method for obtaining 2D SXR
diagnostics is useful for the study of high temperature plasmas..
16. 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, 10.1088/1741-4326/ab1858, 59, 7, 076007-1-076007-9, 2019.05, [URL], The fuel particle balance during long duration discharges in the Q-shu University Experiment with steady state spherical tokamak (QUEST) was investigated. QUEST has all-metal plasma facing walls (PFWs) that were temperature controlled during the experiments. The presence of a transport barrier for hydrogen (H) at the interface between a plasma-induced deposition layer and metallic substrate was confirmed by nuclear reaction analysis with exposing deuterium plasma. An effective method to evaluate global hydrogen flux to PFWs is proposed, taking advantage of the nature of wall saturation. The outgoing flux of fuel particles from the PFWs just after the plasma termination was proportional to the square of wall-stored H, which indicates that enhanced recombination of solved hydrogen played an essential role in dynamic retention and was in agreement with predictions from the H-barrier model. A simple calculation based on the combination of wall modelling and rate equations of the H states denoted a significant impact of wall modelling on the time response of the plasma density. Hence, a proper wall model including the effects of the deposition layer creating the H barrier is required to be developed, even for all-metal PFW devices..
17. 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, 146, Part B, 2567-2570, Volume 146, Part B, September 2019, Pages 2567-2570, 2019.05, [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..
18. K. Hanada, N. Yoshida, I. Takagi, T. Hirata, A. Hatayama, K. Okamoto, Y. Oya, T. Shikama, Z. Wang, H. Long, C. Huang, M. Oya, H. Idei, Y. Nagashima, T. Onchi, M. Hasegawa, K. Nakamura, H. Zushi, K. Kuroda, S. Kawasaki, A. Higashijima, T. Nagata, S. himabukuro, 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, https://doi.org/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..
19. 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, https://doi.org/10.1016/j.fusengdes.2019.04.059, 146, Part B, 2628-2631, Volume 146, Part B, September 2019, Pages 2628-263, 2019.04, [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..
20. 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, 146, Part A, 1149-1152, Volume 146, Part A, September 2019, Pages 1149-1152, 2019.02, [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..
21. 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, https://doi.org/10.1585/pfr.14.1205038, 14, 1205038, 1205038-1-1205038-3, 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 mid-plane 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 Hα 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 35 A in the LFS injection. The electron density ne predicted from the position of the upper hybrid resonance agreed with the line-averaged ne 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..
22. Banerjee Santanu,Zushi Hideki,Nishino Nobuhiro,Hanada Kazuaki, Idei Hiroshi, Nakamura K, Hasegawa Makoto, Fujisawa Akihide, Nagashima Yoshihiko, Mishra Kishore, Tashima Saya, Onchi Takumi, Kuzmin Arseniy, Matsuoka Keisuke, Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST, Plasma Physics and Controlled Fusion, 60, 085014, Vol. 60, 085014, 2018, 2018.06.
23. 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, In tokamaks, the temperature of the plasma-facing wall is an important parameter for achieving particle balanceand therefore steady-state operation. QUEST, which is a middle-sized spherical tokamak, has hot walls that act asplasma-facing walls. They can be actively heated with sheath heaters and actively cooled with water. To controlthe wall temperature, heating and cooling systems have been developed. These systems adjust the power of thesheath heaters and the motor valves of the cooling system, respectively. The two systems communicate viaEthernet through UDP and control the hot-wall temperature cooperatively. The plasma control system (PCS) inQUEST has also been modified, especially with respect to gas fueling, in order to enable long-duration plasmasustainment. A feedback controller has been installed in the PCS, together with a mass flow controller, allowingHα emission from the plasma which is used as a reference signal, to be well controlled. Plasma density calculationsusing a field-programmable gate array are proposed for the feedback control system..
24. H. Idei1, T. Kariya2, T. Imai2, K. Mishra4, T. Onchi1, O. Watanabe1, H. Zushi1, K. Hanada1, J. Qian3, A. Ejiri5, M.M. Alam4, K. Nakamura1, A. Fujisawa1, Y. Nagashima1, M. Hasegawa1, K. Matsuoka1, A. Fukuyama6, S. Kubo7, T. Shimozuma7, M. Yoshikawa2, M. Sakamoto2, S. Kawasaki1, H. Nakashima1, A. Higashijima1, S. Ide8, T. Maekawa9, Y. Takase5 and K. Toi7, Fully non-inductive second harmonic electron cyclotron plasma ramp-up in the QUEST spherical tokamak, Nuclear Fusion, 10.1088/1741-4326/aa7c20, 57, 12, 126045 (11pp), 126045 (11pp), 2017.12, 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..
25. Z. Wang1, K. Hanada2, N. Yoshida2, T. Shimoji1, M. Miyamoto3, Y. Oya4, H. Zushi2, H. Idei2, K. Nakamura2, A. Fujisawa2, Y. Nagashima2, M. Hasegawa2, S. Kawasaki2, A. Higashijima2, H. Nakashima2, T. Nagata2, A. Kawaguchi2, T. Fujiwara2, K. Araki2, O. Mitarai5, A. Fukuyama6, Y. Takase7, and K. Matsumoto8, 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, 093502-1-093502-8, Review of Scientific Instruments 88, 093502 (2017); doi: 10.1063/1.5000739, 2017.09, 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..
26. R. Yoneda1, K. Hanada2, K. Nakamura2, H. Idei2, N. Yoshida2, M. Hasegawa2, T. Onchi2, K. Kuroda2, S. Kawasaki2, A. Higashijima2, T. Nagata2, A. Isayama3, O. Mitarai4, A. Fukuyama5, and Y. Takase6, Effect of magnetic structure on RF-induced breakdown in QUEST, 10.1063/1.4985142, 24, 6, 062513-1-062513-10, Physics of Plasmas 24, 062513 (2017); https://doi.org/10.1063/1.4985142, 2017.06, 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/B v )·(∂B v /∂R)
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..
27. Kengoh KURODA, Roger RAMAN1), Kazuaki HANADA, Makoto HASEGAWA, Takumi ONCHI, Masayuki ONO2), Thomas JABOE1), Brian A. NELSON1), Masayoshi NAGATA3), Osamu MITARAI4), Kazuo NAKAMURA, Hiroshi IDEI, John ROGERS1), Shoji KAWASAKI, Takahiro NAGATA, Arseniy KUZMIN, Shinichiro KOJIMA, Osamu WATANABE, Aki HIGASHIJIMA, Yuichi TAKASE5) and Atsushi FUKUYAMA6) , Current Start-Up Using the New CHI System, Plasma and Fusion Research, 10.1585/pfr.12.1202020, 12, 1202020-1-1202020-3, Volume 12, 1202020 (2017), 2017.04, 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..
28. Makoto Hasegawa, Kazuo Nakamura, Hideki Zushi, K.Hanada, Fujisawa Akihide, K. Tokunaga, Hiroshi Idei, Nagashima Yoshihiko, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Current status and prospect of plasma control system for steady-stateoperation on QUEST, Fusion Engineering and Design, http://dx.doi.org/10.1016/j.fusengdes.2016.04.016, 112, 699-702, Vol. 112, pp. 699-702, 2016.12, The plasma control system (PCS) of QUEST is developed according to the progress of QUEST project. Sinceone of the critical goals of the project is to achieve the steady-state operation with high temperaturevacuum 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 ofreflective memories (RFMs). The PCS controls the plasma edge position with the real-time identificationof 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 H signal filtered by a digital low-pass filterare proposed and suitable for the steady-state operation on QUEST. The present status and prospect ofthe PCS are presented with recent topics..
29. K. Hanada1, H. Zushi1, H. Idei1, K. Nakamura1, M. Ishiguro2, S. Tashima2, E. I. Kalinnikova2, Y. Nagashima1, M. Hasegawa1, A. Fujisawa1, A. Higashijima1, S. Kawasaki1, H. Nakashima1, O. Mitarai3, A. Fukuyama4, Y. Takase5, X. Gao6, H. Liu6, J. Qian6, M. Ono7 and R. Raman8, 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, 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..
30. K. Nakamura 1, M.M. Alam 2, Y.Z. Jiang 3, O. Mitarai 4, K. Kurihara 5, Y. Kawamata 5, M. Sueoka 5, M. Takechi 5, M. Hasegawa 1, K. Tokunaga 1, K. Araki 1, H. Zushi 1, K. Hanada 1, A. Fujisawa 1, H. Idei 1, Y. Nagashima 1, S. Kawasaki 1, H. Nakashima 1, A. Higashijima 1, T. Nagata 1, A. Fukuyama 6, 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, 109-111 (Part B), 11, 1528-1533, Volumes 109–111, Part B, 1 November 2016, Pages 1528-1533, 2016.11, In the present RF-driven (ECCD) steady-state plasma on QUEST (Bt = 0.25 T, R = 0.68 m, a = 0.40 m), plasma current seems to flow in the open magnetic surface outside of the closed magnetic surface in the low-field region according to plasma current fitting (PCF) method. We consider that the current in the open magnetic surface is due to orbit-driven current by high-energy particles in RF-driven plasma. So based on the analysis of current density profile based on the orbit-driven current, plasma equilibrium is to be calculated. We calculated high energy particles guiding center orbits as a contour plot of conserved variable in Hamiltonian formulation and considered particles initial position with different levels of energy and pitch angles that satisfy resonance condition. Then the profile of orbit-driven current is estimated by multiplying the particle density on the resonance surface and the velocity on the orbits. This analysis shows negative current near the magnetic axis and hollow current profile is expected even if pressure driven current is considered. Considering the hollow current profile shifted toward the low-field region, the equilibrium is fitted by J-EFIT coded by MATLAB..
31. O. Mitarai 1, K. Nakamura 2, M. Hasegawa 2, T. Onchi 2, H. Idei 2, A. Fujisawa 2, K. Hanada 2, H. Zushi 2, A. Higashijima 2, H. Nakashima 2, S. Kawasaki 2, QUEST group 2, K. Matsuoka 3, S. Koike 4, T. Takahashi 4, H. Tsutsui 5, 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, 109-111 (Part B), 11, 1365-1370, Volumes 109–111, Part B, 1 November 2016, Pages 1365-1370, 2016.11, As QUEST has a small central solenoid (CS), a larger Ohmic discharge current has been obtained when the plasma shifts to the inboard side. This tendency restricts a divertor operation to the smaller plasma current regime. As the inner divertor coil has a smaller mutual inductance, it would be expected that its utilization seems to be better for easier plasma current ramp-up for a divertor operation. In this work, we made comparative studies on the plasma current ramp-up for two divertor coils. It is found that while the inner divertor coil with smaller mutual inductance needs a larger coil current, the outer divertor coil with larger mutual inductance needs a smaller coil current for divertor operation. Thus we have found that the plasma current ramp-up characteristics are almost similar for both configurations. We also propose a new fueling method for spherical tokamak (ST) using the coaxial helicity injection (CHI). The main plasma current would be generated at first, and then the CHI plasma current is created between bottom two electrode plates and merged into the main plasma current for fueling..
32. Md Mahbub Alam 1, Kazuo Nakamura 2, Fan Xia 3, Osamu Mitarai 4, Makoto Hasegawa 2, Kazutoshi Tokunaga 2, Kuniaki Araki 2, Hideki Zushi 2, Kazuaki Hanada 2, Akihide Fujisawa 2, Hiroshi Idei 2, Yoshihiko Nagashima 2, Shoji Kawasaki 2, Hisatoshi Nakashima 2, Aki Higashijima 2, Takahiro Nagata 2, 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, 109-111 (Part B), 11, 1624-1630, Volumes 109–111, Part B, 1 November 2016, Pages 1624-1630, 2016.11, In the present RF-driven divertor plasma of QUEST, it has been observed that orbit-driven current flows in the open magnetic surfaces outside of the closed magnetic surfaces. To observe this phenomenon and the characteristics of the orbit-driven current, current density profiles have been calculated on two different equilibrium conditions. We calculated current density profiles from particle guiding center orbits both for the fundamental and the second harmonic resonances for the 8.2 GHz electron cyclotron current drive. From this calculation, hollow current density profiles have been obtained with significant characteristics on both conditions. Only positive current distribution has been observed in the open magnetic surfaces outside of the closed magnetic surfaces..
33. T Onchi1, H Zushi1, K Mishra2,3, Y Oyama2, Y Nagashima1, K Hanada1, H Idei1, M Hasegawa1, A Kuzmin1, H Miura2, K Nakamura1, A Fujisawa1 and K Nagaoka4, 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, 115004 (12pp), Plasma Phys. Control. Fusion 58 (2016) 115004 (12pp), 2016.09, 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..
34. Santanu Banerjee1, H. Zushi2, N. Nishino3, K. Mishra1, Y. Mahira2, S. Tashima2, A. Ejiri4, T. Yamaguchi4, T. Onchi2, Y. Nagashima2, K. Hanada2, K. Nakamura2, H. Idei2, M. Hasegawa2, A. Fujisawa2, A. Kuzmin2, and K. Matsuoka2, 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, 082507-1-082507-8, Physics of Plasmas 23, 082507 (2016);, 2016.08, 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..
35. A. Kuzmin 1, H. Zushi 1, I. Takagi 2, S.K. Sharma 3, Y. Hirooka 4, M. Kobayashi 4, M. Sakamoto 5, K. Hanada 1, T. Onchi 1, Y. Oyama 6, N. Youshida 1, K. Nakamura 1, A. Fujisawa 1, H. Idei 1, Y. Nagashima 1, M. Hasegawa 1, K. Mishra 6, Hydrogen flux measurements with permeation probes in spherical tokamak QUEST, Vacuum, 10.1016/j.vacuum.2016.04.025, 129, 178-182, Volume 129, July 2016, Pages 178-182, 2016.07, 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..
36. Kazuo Nakamura, Md Mahbub Alam, Yanzheng Jiang, Osasmu Mitarai, Manabu Takechi, Makoto Hasegawa, K. Tokunaga, Kuniaki Araki, Zushi Hideki, K.Hanada, Fujisawa Akihide, H. Idei, Nagashima Yoshihiko, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Atsushi Fukuyama, Analysis of Plasma Equilibrium Based on Orbit-Driven Current Density Profile in Steady-State Plasma on QUEST, FUSION ENGINEERING AND DESIGN, Available online 17 December 2015, 2015.12.
37. Md Mahbub Alam, Kazuo Nakamura, Fan Xia, Osamu Mitarai, Makoto Hasegawa, K. Tokunaga, Kuniaki Araki, Zushi Hideki, K.Hanada, Fujisawa Akihide, H. Idei, Nagashima Yoshihiko, Shoji Kawasaki, Hisatoshi nakashima, Aki Higashijima, Takahiro Nagata, Comparison of current density profiles based on particle orbit-driven current in steady-state plasma on QUEST, Fusion Engineering and Design, Available online 23 November 2015, 2015.11.
38. Kazuaki Hanada, Zushi Hideki, Naoaki Yoshida, N. Yugami, T. Honda, Makoto Hasegawa, MISHRA KISHORE KANTI, Aleksandrovich Arseniy Kuzmin, Kazuo Nakamura, Fujisawa Akihide, H. Idei, Nagashima Yoshihiko, Osamu Watanabe, Takumi Onchi, H. Watanabe, K. Tokunaga, Aki Higashijima, Shoji Kawasaki, Hisatoshi Nakashima, Particle balance in long duration RF driven plasmas on QUEST, Journal of Nuclear Materials, 463, 1084-1086, 2015.08.
39. Takumi Onchi, Y. Mahira, K. Nagaoka, S. Tashima, S.Banerjee, MISHRA KISHORE KANTI, H. Idei, K.Hanada, Kazuo Nakamura, Fujisawa Akihide, Nagashima Yoshihiko, Makoto Hasegawa, K. Matsuoka, Aleksandrovich Arseniy Kuzmin, Oamu Watanabe, Shoji Kawasaki, Hisatoshi Nakashima, Aki 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.
40. Aleksandrovich Arseniy Kuzmin, Zushi Hideki, I. Takagi, S.K. Sharma, A. Rusinov, Y. Inoue, Y. Hirooka, H. Zhou, M. Kobayashi, Mizuki Sakamoto, K.Hanada, Naoaki Yoshida, Kazuo Nakamura, Fujisawa Akihide, K. Matsuoka, H. Idei, Nagashima Yoshihiko, Makoto Hasegawa, Takumi Onchi, 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.
41. Takumi Onchi, Zushi Hideki, K. Mishra, Y. Mahira, Kenichi Nagaoka, K.Hanada, H. Idei, Makoto Hasegawa, Kazuo Nakamura, Fujisawa Akihide, Nagashima Yoshihiko, Keisuke Matsuoka, Saya Tashima, Santanu Banerjee, Aleksandrovich Arseniy Kuzmin, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Osamu 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, Vol.22
082513
(14pp), 2015.08.
42. Makoto Hasegawa, Kazuo Nakamura, hideki zushi, kazuaki hanada, Akihide Fujisawa, Osamu Mitarai, KAZUTOSHI TOKUNAGA, Hiroshi Idei, Yoshihiko Nagashima, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Development of a high-performance control system bydecentralization with reflective memory on QUEST, Fusion Engineering and Design, 96-97, 629-632, 96-97 (2015) 629-632, 2015.07, The plasma control system (PCS) of QUEST was a centralized system, which lost its scalability because ofthe overload imposed on its central processing unit (CPU) of the PCS, making it impossible to add newfunctions. Thus, the PCS is distributed into a main workstation (WS) and subsystem (SS) with a reflectivememory (RFM) in order to share data between these systems so as to mitigate the load on each system.As a result, 128 double-precision floating-point numbers (DBLs) can be transferred from the SS to the WSwith a maximum latency of 250 s. The WS and the SS each have quad-core CPUs, and tasks are executedin parallel. Although one of the four cores is intermittently occupied by up to 90% by this transaction, theoccupation is normally 60%. A time correction procedure is used to map the recorded data sets on theWS and the SS to a common time base by referring to the time difference between two systems..
43. Hiroki Miura　, Kazuaki Hanada, Zushi Hideki, Kazuo Nakamura, Fujisawa Akihide, Hiroshi Idei, Nagashima Yoshihiko, 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, 3402066, 2015.07.
44. MISHRA KISHORE KANTI, zushi hideki, Hiroshi Idei, Makoto Hasegawa, Takumi Onchi, Saya Tashima, Banerjee S, Kazuaki Hanada, H Togashi, T Yamaguchi, Akira Ejiri, Yuichi Takase, Kazuo Nakamura, Fujisawa Akihide, Nagashima Yoshihiko, Aleksandrovich Arseniy Kuzmin, Self Organization of High　βp Plasma Equilibrium with an Inboard Proidal Magnetic Field Null in QUEST, Nuclear Fusion, 55 (2015) 083009 (13pp), 2015.07.
45. 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..
46. Makoto Hasegawa, Kazuo Nakamura, hideki zushi, kazuaki hanada, Akihide Fujisawa, Keisuke Matsuoka, Hiroshi Idei, Yoshihiko Nagashima, KAZUTOSHI TOKUNAGA, Shoji Kawasaki, Hisatoshi Nakashima, Aki 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, A drift error correction technique with machine vision and a real-time equilibrium calculation code have been developed on the QUEST (Q-shu university experiment with the steady-state spherical tokamak) for steady-state operation. The drift error caused by the long time-integration of magnetic raw signals has to be removed. With a captured image of the plasma’s cross section, the plasma’s position is identified by use of image filters. The measured magnetic flux values are corrected to the calculated flux values estimated by using this plasma position. The correction with the captured image work as expected in the preliminary result using a flashlight instead of a plasma..
47. 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..
48. 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..
49. 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..
50. 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..
51. 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.
52. 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, 9.0, RA, Article No. 3402093, 2014.06.
53. H. Togashi, A. Ejiri, K. Nakamura, Y. Takase, T. Yamaguchi, H. Furui, K. Imamura, T. Inada, H. Kakuda, A. Nakanishi, T. Oosako, T. Shinya, M. Sonehara, S. Tsuda, N. Tsujii, T. Wakatsuki, makoto hasegawa, Yoshihiko Nagashima, K. Narihara, I. Yamada and H. Tojo, Multi-pass Thomson Scattering Measurement on the TST-2 Spherical Tokamak, REVIEW OF SCIENTIFIC INSTRUMENTS, 85.0, Article No. 056103, 2014.06, In multi-pass Thomson scattering (TS) scheme, a laser pulse makes multiple round trips through the plasma, and the effective laser energy is enhanced, and we can increase the signal-to-noise ratio as a result. We have developed a coaxial optical cavity in which a laser pulse is confined, and we performed TS measurements using the coaxial cavity in tokamak plasmas for the first time. In the optical cavity, the laser energy attenuation was approximately 30% in each round trip, and we achieved a photon number gain of about 3 compared with that obtained in the first round trip. In addition, the temperature measurement accuracy was improved by accumulating the first three round trip waveforms..
54. K. Hanada, H. Zushi, N. Yoshida, M. Hasegawa, K. Mishra, Kuzumina, K. Nakamura, A. Fujisawa, H. Idei, Y. Nagashima, O. Watanabe, T. Onchi, H. Watanabe, K. Tokunaga, A. Higashijima, S. Kawasaki, H. Nakashima, Y. Takase, A. Fukuyama, O. Mitarai, T. Maekawa and M. Peng, Particle balance in long duration RF driven plasmas on QUEST, 21st International Conference on Plasma Surface Interactions 2014, 2014.06.
55. Togashi, H.; Ejiri, A.; Hiratsuka, J.; Nakamura, K.; Takase, Y.; Yamaguchi, T.; Furui, H.; Imamura, K.; Inada, T.; Kakuda, H.; Nakanishi, A.; Oosako, T.; Shinya, T.; Sonehara, M.; Tsuda, S.; Tsujii, N.; Wakatsuki, T.; Hasegawa, M.; Nagashima, Y.; Narihara, K.; Yamada, I.; Tojo, H., Note: Multi-pass Thomson scattering measurement on the TST-2 spherical tokamak, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.4878260, 85.0, 5.0, 1.0, Article No. 056103, 2014.05, In multi-pass Thomson scattering (TS) scheme, a laser pulse makes multiple round trips through the plasma, and the effective laser energy is enhanced, and we can increase the signal-to-noise ratio as a result. We have developed a coaxial optical cavity in which a laser pulse is confined, and we performed TS measurements using the coaxial cavity in tokamak plasmas for the first time. In the optical cavity, the laser energy attenuation was approximately 30% in each round trip, and we achieved a photon number gain of about 3 compared with that obtained in the first round trip. In addition, the temperature measurement accuracy was improved by accumulating the first three round trip waveforms. (C) 2014 AIP Publishing LLC..
56. Santanu 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, Proceedings of the 12th Asia Pacific Physics Conference, JPS Conf. Proc. ，015036 (2014), 2014.03.
57. 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)..
58. Hiro TOGASHI, Akira EJIRI, Makoto HASEGAWA, Junichi HIRATSUKA, Yoshihiko NAGASHIMA, Keishun NAKAMURA, Kazumichi NARIHARA, Yuichi TAKASE, Hiroshi TOJO, Naoto TSUJII, Ichihiro YAMADA, Takashi YAMAGUCHI and the TST-2 Team, Injection and Confinement of a Laser Pulse in an Optical Cavity for Multi-Pass Thomson Scattering Diagnostics in the TST-2 Spherical Tokamak Device, Plasma and Fusion Research, 9.0, RC, 2.0, Article No. 1202005, 2014.01, A multi-pass Thomson scattering (TS) system based on confining laser pulses in an optical cavity was constructed for measuring very low-density plasma in the TST-2 spherical tokamak device. This paper describes the setup of the optical system, injection of the laser pulse into the cavity, and properties of the confined laser pulse. A combination of Pockels cell plus polarizer, which serves as an optical shutter, allows us to inject and then confine intense laser pulses in the cavity. A photodiode signal monitoring the very weak light leaking from the cavity mirrors demonstrated that the laser pulse makes many round trips, with a round-trip efficiency of approximately 0.73. The effective number of round trips (i.e., the signal enhancement factor) is approximately 3.7. For an injection efficiency of approximately 0.69, a cavity-confined laser pulse, applied to Thomson scattering, will yield a scattered signal that is five times larger than that from a single-pass laser pulse..
59. Mishra, Kishore; Idei, H; Zushi, H; Nagata, K; Akimoto, R; Yamamoto, MK; Hanada, K; Hasegawa, M; Nakamura, K; Fujisawa, A; , Thermal imaging of plasma with a phased array antenna in QUESTa), REVIEW OF SCIENTIFIC INSTRUMENTS, 85.0, 11.0, Article No. 11E808, 2014.01.
60. 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..
61. Kishore, Mishra; Zushi, H; Idei, H; Tashima, S; Banerjee, S; Hasegawa, M; Hanada, K; Nakamura, K; Fujisawa, A; Nagashima, Y; , 28pKB-2 On formation of a natural inboard separatrix in ECW heated Ohmic plasma on the spherical tokamak QUEST, 日本物理学会講演概要集, 68.0, 2.0, 208.0, 2013.09.
62. 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 and QUEST Team, Non-Inductive Current Drive by EC Waves in an Inboard Poloidal Magnetic Field Null Configuration on the Spherical Tokamak QUEST, Plasma and Fusion Research, 8.0, RA, 5.0, Article No. 2402118, 2013.09, 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..
63. 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..
64. Kishore Mishra, Hiroshi Idei, Hideki Zushi, Saya Tashima, Santanu Banerjee, Makoto Hasegawa, Kazuaki Hanada, Kazuo Nakamura, Akihide Fujisawa, Keisuke Matsuoka, Yoshihiko Nagashima, S. Kawasaki, A. Higashijima, H. Nakashima, and Quest Group, Characteristics of High Poloidal Beta (β p) Plasma Formed by Electron Cyclotron Waves in Spherical Tokamak QUEST, Proceedings of the 12th Asia Pacific Physics Conference (APPC12), 1.0, 5.0, Article No. 015031, 2013.07.
65. 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..
66. K. Tokunaga, T. Hotta, K. Araki, Y. Miyamoto, T. Fujiwara, M. Hasegawa, K. Nakamura, K. Ezato, S. Suzuki, M. Enoeda, M. Akiba, T. Nagasaka, R. Kasada, A. Kimura, High heat loading properties of vacuum plasma spray tungsten coatings on reduced activation ferritic/martensitic steel, JOURNAL OF NUCLEAR MATERIALS, 438.0, S905-S908, 2013.07.
67. NAKAMURA Kazuo, FUJITA Hiroki, LIU Xiaolong, XUE Erbing, MITARAI Osamu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki, Quaternion Concept in Matrix Converter Design for Feedback Stabilization by Magnetic Field Coil, Proc. International Conference on Electrical Engineering (ICEE 2013)，Xiamen，July 2013, S7-02，FP0393, 2013.07.
68. 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.
69. Kazutoshi Tokunaga, Tomohiro Hotta, Teppei Otsuka, Akira Kobayashi, Kuniaki Araki, Yoshio Miyamoto, Tadashi Fujiwara, Makoto Hasegawa, Kazuo Nakamura, Koichiro Ezato, Satoshi Suzuki, Mikio Enoeda, Masato Akiba, Takuya Nagasaka, Ryuta Kasada, Akihiko Kimura, Material behavior on heat loading and hydrogen penetration of vacuum plasma spray tungsten coatings on reduced activation ferritic/martensitic steel, 溶接学会論文集，一般社団法人 溶接学会, 31，4，183s-187s, 2013.04.
70. Kazutoshi Tokunaga, Tomohiro Hotta, Teppei Otsuka, Akira Kobayashi, Kuniaki Araki, Yoshio Miyamoto, Tadashi Fujiwara, Makoto Hasegawa, Kazuo Nakamura, Koichiro Ezato, Satoshi Suzuki, Mikio Enoeda, Masato Akiba, Takuya Nagasaka, Ryuta Kasada, Akihiko Kimura, Material behavior on heat loading and hydrogen penetration of vacuum plasma spray tungsten coatings on reduced activation ferritic/martensitic steel, 溶接学会論文集，一般社団法人 溶接学会, 31，4，183s-187s, 2013.04.
71. 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..
72. Liu Xiaolong; Nakamura, Kazuo; Yoshisue, Tatsuya; Mitarai, Osamu; Hasegawa, Makoto; Tokunaga, Kazutoshi; Xue Erbing; Zushi, Hideki; Hanada, Kazuaki; Fujisawa, Akihide; Idei, Hiroshi; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki; Araki, Kuniaki, H-infinity Loop Shaping Control for Plasma Vertical Position Instability on QUEST, PLASMA SCIENCE & TECHNOLOGY, 10.1088/1009-0630/15/3/21, 15.0, 3.0, 295.0-299.0, 0.0, 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..
73. Takashi YAMAGUCHI, Akira EJIRI, Junichi HIRATSUKA, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Kazumichi NARIHARA, Yuichi TAKASE, Hideki ZUSHI and the QUEST group, Electron Temperature Measurement on QUEST Spherical Tokamak by Thomson Scattering System, Plasma and Fusion Research, 8.0, RA, Article No. 1302001, 2013.02.
74. Nakanishi, Hideya; Hasegawa, Makoto; Yoshikawa, Masayuki;, Status of remote experiments in fusion reactor, issues and plans. Remote participations for LHD and other experiments at universities, Journal of Plasma and Fusion Research, 89.0, 7.0, v. 89(7); p. 468-473, 2013.01.
75. Nakanishi, H.; Kojima, M.; Takahashi, C.; Ohsuna, M.; Imazu, S.; Nonomura, M.; Hasegawa, M.; Yoshikawa, M.; Nagayama, Y.; Kawahata, K., Fusion virtual laboratory: The experiments' collaboration platform in Japan, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2012.04.027, 87.0, 12.0, 2189.0-2193.0, 2012.12, Fusion virtual laboratory (FVL) is the experiments' collaboration platform covering multiple fusion projects in Japan. Major Japanese fusion laboratories and universities are mutually connected through the dedicated virtual private network, named SNET, on SINET4. It has 3 different categories; (i) LHD remote participation, (ii) bilateral experiments' collaboration, and (iii) remote use of supercomputer. By extending the LABCOM data system developed at LHD, FVL supports (i) and (ii) so that it can deal with not only LHD data but also the data of two remote experiments: QUEST at Kyushu University and GAMMA10 at University of Tsukuba. FVL has applied the latest "cloud" technology for both data acquisition and storage architecture. It can provide us high availability and performance scalability of the whole system. With a well optimized TCP data transferring method, the unified data access platform for both experimental data and numerical computation results could become realistic on FVL. The FVL project will continue demonstrating the ITER-era international collaboration schemes and the necessary technology. (c) 2012 Elsevier B.V. All rights reserved..
76. 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..
77. Santanu Banerjee, H. Zushi, N. Nishino, Y. Nagashima, K. Hanada, S. Tashima, T. Inoue, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa and K. Matsuoka, Edge turbulence characteristics of the Ohmic-ECRH driven plasma current phase investigated with fast visible imaging in QUEST, Proc. 22nd International Toki Conference November 19- 22，2012, P3-32, 2012.11.
78. H. Takahashi, K. Hanada, M. Ishiguro, H. Zushi, H. Fujisawa, K. Nakamura, H. Idei, Y. Nagashima, M. Hasegawa, S. Kawasaki, H. Nakashima, A, Higashijima, Y. Takase, A. Fukuyama, O. Mitarai, X. Gao, and H. Q. Liu, Measurement of ion saturation current and floating potential profile in divertor region on QUEST, Proc. 22nd International Toki Conference, （※）, 2012.11.
79. 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 and QUEST Team, Non-Inductive Current Drive by EC Waves in an Inboard Poloidal Magnetic Field Null Configuration on the Spherical Tokamak QUEST, Proc. 22nd International Toki Conference November 19- 22, 2012, 2012.11.
80. 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].
81. 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.
82. Santanu BANERJEE, H ZUSHI, N NISHINO, Y NAGASHIMA, K HANADA, S TASHIMA, T INOUE, K NAKAMURA, H IDEI, M HASEGAWA, A FUJISAWA, K MATSUOKA, 18aFA-6 Fluctuation characteristics and flow at the SOL of ECRH driven plasma in QUEST, 日本物理学会講演概要集, 67.0, 2.0, 185.0, 2012.09.
83. 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..
84. Nakamura, Kazuo; Liu, Xiaolong; Tomoda, Masashi; Yoshisue, Tatsuya; Mitarai, Osamu; Hasegawa, Makoto; Tokunaga, Kazutoshi; Zushi, Hideki; Hanada, Kazuaki; Idei, Hiroshi; , Effect of Shell Cut and Diagnostic Port on Stabilizing Characteristics of Vertical Position Instability on QUEST, Research Institute for Applied Mechanics，Kyushu University, 143.0, 2012.09.
85. 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.
86. 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.
87. 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, 132.0, 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..
88. 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..
89. Junichi HIRATSUKA, Akira EJIRI, hasegawa makoto, Nagashima Yoshihiko, Yuichi TAKASE, Hiroshi TOJO, Takashi YAMAGUCHI, Takanori AMBO, Hirokazu FURUI, Takahiro HASHIMOTO, Hidetoshi KAKUDA, Kunihiko KATO, Takuya OOSAKO, Takuya SAKAMOTO, Ryota SHINO, Takahiro SHINYA, Masateru SONEHARA, Takuma WAKATSUKI, Osamu WATANABE, Off-Axis Temperature Anisotropy Measurement by Double-Pass Thomson Scattering Diagnostic System on TST-2, Plasma and Fusion Research, 7.0, RA, Article No. 2402092, 2012.07.
90. 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。.
91. LIU Xiaolong, YOSHISUE Tatsuya, NAKAMURA Kazuo, XUE Erbing, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki, Robust Control on Plasma Vertical Position Instability by a Matrix Converter as Power Supply of QUEST, Proc. International Conference on Electrical Engineering (ICEE 2012)，Kanazawa，July 2012 , （※）, 2012.07.
92. 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.
93. NAKAMURA Kazuo, YOSHISUE Tatsuya, LIU Xiaolong, XUE Erbing, MITARAI Osamu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki, Three Phase-to-Single Phase Matrix Converter Design for Feedback Stabilization by Magnetic Field Coil, Proc. International Conference on Electrical Engineering (ICEE 2012)，Kanazawa，July 2012 , （※）, 2012.07.
94. 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].
95. 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..
96. 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..
97. 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 and K. Toi, Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased-array Antenna in QUEST, AIP Conference Proceedings （Radio Frequency Power in Plasmas）, 1406，473-476, 2011.12.
98. H. Nakanishi, M. Ohsuna, M. Kojima, S. Imazu, M. Nonomura, T. Yamamoto, M. Emoto, M. Yoshida, C. Iwata, M. Shoji, Y. Nagayama, K. Kawahata, M. Hasegawa, A. Higashijima, K. Nakamura, Y. Ono, M. Yoshikawa and S. Urushidani, Data acquisition system for steady-state experiments at multiple sites, NUCLEAR FUSION, 51.0, 11.0, Article No. 113014, 2011.11.
99. 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].
100. 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 (
101. 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, Optimal Control on Plasma Vertical Position Instability in QUEST, Proc. 13th Cross Straits Symposium，Kyushu University，Fukuoka，Nov.，2011, 31.0-21.0, 2011.11.
102. 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..
103. 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..
104. 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 and Kuniaki ARAKI, Study of Matrix Converter as a Current-Controlled Power Supply in QUEST Tokamak, Plasma and Fusion Research, 6.0, RA, 5.0, Article No. 2405137, 2011.10, 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..
105. Santanu Banerjee, H Zushi, N Nishino, K Hanada, H Honma, HQ Liu, M Ishiguro, T Ryoukai, S Tashima, K Nakamura, H Idei, M Hasegawa, A Fujisawa, 26pGW-12 B_Z dependence of the higher order moments of density fluctuations in slab geometry plasma in QUEST, 日本物理学会講演概要集, 66.0, 1.0, 256.0, 2011.09.
106. HQ Liu, K Hanada, N Nishino, R Ogata, M Ishiguro, H Zushi, K Nakamura, A Fujisawa, H Idei, M Hasegawa, 26pGW-13 Experimental observation and Statistical Analysis of Blob-like Structures in QUEST, 日本物理学会講演概要集, 66.0, 1.0, 256.0, 2011.09.
107. Junichi HIRATSUKA, Akira EJIRI, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Yuichi TAKASE, Hiroshi TOJO, Takashi YAMAGUCHI, Takanori AMBO, Hidetoshi KAKUDA, Takuya SAKAMOTO, Ryota SHINO, Masateru SONEHARA, Takuma WAKATSUKI and Osamu WATANABE, Development of a Double-pass Thomson Scattering System in the TST-2 Spherical Tokamak, Plasma and Fusion Research, 6.0, RC, Article No. 1202133, 2011.09, A double-pass Thomson scattering system, in which a laser pulse makes a round trip through the plasma, was constructed. Using the same optics and a fast detection unit, we can resolve backward and forward scattering pulses in the signal. Because these scatterings reflect velocity distribution along different directions, electron temperature anisotropy can be estimated from the double-pass Thomson scattering system..
108. 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..
109. 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].
110. Xiaolong Liu, Kazuo Nakamura, 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 Stabilizing Power Supply for Vertical Position Instability on QUEST Tokamak, Proc. 2011 Annual Conference of I.E.E. of Japan，Industry Applications Society，Okinawa，Sept. 6-8，2011, （※）, 2011.09.
111. 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..
112. 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..
113. 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.
114. K. Nakamura, X. L. Liu, T. Yoshisue, O. Mitarai, K. Tokunaga, M. Hasegawa, H. Zushi, K. Hanada, A. Fujisawa, M. Sakamoto, H. Idei, S. Kawasaki, H. Nakashima, A. Higashijima, K. Araki , Venturini Method and Space Vector Modulation Method in Matrix Converter, Proc. International Conference on Electrical Engineering (ICEE2011)，Hong Kong，July 11-14，2011, （※）, 2011.07.
115. 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 and K. Toi, Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased-array Antenna in QUEST, RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 19th Topical Conference, 1406.0, 1.0, 473.0-476.0, 2011.06, 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 (
116. 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..
117. Xiaolong Liu, Kazuo Nakamura, Kazutoshi Tokunaga, Makoto Hasegawa, Kuniaki Araki, Yi Jiang, Tatsuya Yoshisue, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Simulation on Toroidal Field Power Supply of HL-2A Tokamak: Application of Dual DQ0 Transformation for Six-Phase Synchronous Generator Model, Engineering Sciences Reports，Kyushu University, Vol.33，pp.7-10, 2011.06.
118. 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)..
119. Ejiri, Akira; Yamaguchi, Takashi; Hiratsuka, Junichi; Takase, Yuichi; Hasegawa, Makoto; Narihara, Kazumichi;, Development of a Bright Polychromator for Thomson Scattering Measurements, Plasma and Fusion Research, 5.0, RA, Article No. S2082, 2010.12.
120. 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..
121. 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..
122. 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..
123. 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, 11-16 October 2010 Daejon, Korea, 2010.11.
124. Nakanishi, H; Emoto, M; Nagayama, Y; Yamamoto, T; Imazu, S; Iwata, C; Kojima, M; Nonomura, M; Ohsuna, M; Yoshida, M; Iwata, C; Shoji, M; Nagayama, Y; Kawahata, K; Hasegawa, M;, Data acquisition system for steady state experiments at multi-sites, Proceedings of 23rd IAEA Fusion Energy Conference (IAEA FEC 2010), 453.0, FTP/P6-27, 2010.10, A high-performance data acquisition system (LABCOM system) has been developed for steady state fusion experiments in Large Helical Device (LHD). It also acquires experimental data of multiple remote machines through the 1 Gbps fusion-dedicated virtual private network (SNET) in Japan. The LABCOM system consists of distributed data acquisition (DAQ) computers, data storage devices, and the index database of data locations. Its key objectives are (1) real-time DAQ with the same sampling rates as burst acquisition, and (2) scalability of both the performance and quantity, even in the number of sites. LHD now uses 80 DAQs in parallel and acquires 10.6 GB/shot raw data in short-pulse experiments of 3 min. iteration. In steady state operation, huge kHz or MHz fluctuation data for plasma diagnostics must be processed in real time. In LHD, each DAQ computer can deal with max. 110 MB/s continuous data. The DAQ cluster has established the world record of acquired data amount of 90 GB/shot, which almost reaches the ITER data estimate of 100 or 1000 GB/shot. As for the data storage, the massively parallel processing (MPP) structure is important for scalable input/output performance and data redundancy. Hundreds of tera-byte compressed data are stored in the two-stage storage devices. The data mediation service is a distinguishing characteristic that manages the peer-to-peer data handling among many server and client computers. As every element of the LABCOM system are ds every element of the LABCOM system are distributed on the local area network (LAN), the data of remote fusion devices are acquired simply by extending the LAN to the wide-area SNET. LABCOM system acquires data from three remote experiments of different universities. The speed lowering problem in distant TCP/IP communication, e.g. 60 Mbps on 1 Gbps SNET, is improved by using the optimized congestion control and packet pacing technology. Its bandwidth tests between Japan and France achieved effective 881 Mbps over 10 000 s. A light-weight access control is implemented in the LABCOM system because it provides enough security for a closed VPN like SNET. Toward the fusion goal, a common data-accessing platform is indispensable so that physicists can easily make detailed comparisons between multiple large and small experiments. The demonstrated bilateral scheme will be analogous to that of ITER and the supporting machines..
125. H. Q. Liu, K. Hanada, N. Nishino, R. Ogata, M. Ishiguro, H. Zushi, K. Nakamura, M. Sakamoto, H. Idei, M. Hasegawa, Y. Higashizono, S. Kawasaki, H. Nakashima, A. 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, 2010.10.
126. 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.
127. 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..
128. 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, 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..
129. 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..
130. 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.
131. 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.
132. 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, (Proc.APFA2009?APPTC200, 9.0, ，Volume 9 (2010) pp007-011，(Proc.APFA2009?APPTC2009), 2010.08.
133. 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.
134. 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.
135. 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.
136. Nakanishi, H.; Ohsuna, M.; Kojima, M.; Imazu, S.; Nonomura, M.; Hasegawa, M.; Nakamura, K.; Higashijima, A.; Yoshikawa, M.; Emoto, M.; Yamamoto, T.; Nagayama, Y.; Kawahata, K., DATA ACQUISITION AND MANAGEMENT SYSTEM OF LHD, FUSION SCIENCE AND TECHNOLOGY, 0.0, 58.0, 1.0, 445.0-457.0, 2010.07, The data acquisition (DAQ) and management system of the Large Helical Device (LHD), named the LABCOM system, has been in development since 1995. The recently acquired data have grown to 7 gigabytes per shot, 10 times bigger than estimated before the experiment. In 2006 during 1-h pulse experiments, 90 gigabytes of data was acquired, a new world record. This data explosion has been enabled by the massively distributed processing architecture and the newly developed capability of real-time streaming acquisition. The former provides linear expandability since increasing the number of parallel DAQs avoids I/O bottlenecks. The latter improves the unit performance from 0.7 megabytes/s in conventional CA MAC digitizers to nonstop 110 megabytes/s in CompactPCI The technical goal of this system is to be able to handle one hundred 100 megabytes/s concurrent DAQs even for steady-state plasma diagnostics. This is similar to the data production rate of the next-generation experiments, such as ITER. The LABCOM storage has several hundred terabytes of storage in double-tier structure: The first consists of tens of hard drive arrays, and the second some Blu-ray Disc libraries. Multiplex and redundant storage servers are mandatory for higher availability and throughputs. They together serve sharable volumes on Red Hat GFS2 cluster file systems. The LABCOM system is used not only for LHD but also for the QUEST and GAMMA10 experiments, creating a new Fusion Virtual Laboratory remote participation environment that others can access regardless of their location..
137. 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.
138. 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.
139. Hideya NAKANISHI, Mamoru KOJIMA, Masaki OHSUNA, Setsuo IMAZU, Miki NONOMURA, Takashi YAMAMOTO, Masahiko EMOTO, Yoshio NAGAYAMA, Kazuo KAWAHATA, LHD exp. group, Makoto HASEGAWA, Aki HIGASHIJIMA, Kazuo NAKAMURA, Masayuki YOSHIKAWA, Clustered Data Storage for Multi-Site Fusion Experiments, Plasma and Fusion Research, 5.0, RA, Article No. S1042, 2010.03, Least square method has been used to solve the inverse problem from flux loop measurement to the boundary
values on the CCS (Cauchy Condition Surface). When the CCS method is applied to real experimental data, noise
superposition is inevitable. By introduction of SVD (Singular Value Decomposition) and truncation of the least SV
components, we can expect the shape reproduction robustness against the noise. The truncation simulation of the
less SV component shows shape reproduction error less than no truncation, when the measurement error exceeds a
certain value. .
140. 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.
141. 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.
142. 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.
143. 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.
144. 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.
145. 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.
146. 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, 0.0, 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..
147. Nakanishi, H.; Ohsuna, M.; Kojima, M.; Imazu, S.; Nonomura, M.; Yamamoto, T.; Emoto, M.; Nagayama, Y.; Kawahata, K.; Hasegawa, M.; Nakamura, K.; Higashijima, A..; Yoshikawa, M.;, LABCOM/X Experiment Data Platform and Fusion Virtual Laboratory in Japan, Proceedings (slides, posters) of the 7. IAEA Technical Meeting on Contro, 2009.06.
148. 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)
149. 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, 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..
150. 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, 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..
151. Sakamoto, Mizuki; Ogawa, Masanori; Higashizono, Yuta; Zushi, Hideki; Sato, Konosuke; Nakamura, Kazuo; Hanada, Kazuaki; Idei, Hiroshi; Hasegawa, Makoto; Kawasaki, Shoji; , Erosion and Re-deposition of Plasma-Facing material in Long Duration Discharges on TRIAM-1M, Reports of Research Institute for Applied Mechanics,Kyushu University , 136.0, 19.0-22.0, 43.0，CRPP-ARTICLE-2009-085, 2009.03.
152. 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.
153. 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, Proc.22nd IAEA Fusion Energy Conference, 2008.10.
154. 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..
155. 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.
156. H. ZUSHI, Y. HIROOKA, R. BHATTACHARYAY, M. SAKAMOTO, Y. NAKASHIMA, T. YOSHINAGA, Y. HIGASHIZONO, K. HANADA, N. NISHINO, N. YOSHIDA, K. TOKUNAGA, S. KADO, T. SHIKAMA, S. KAWASAKI, K. OKAMOTO, T. MIYAZAKI, H. HONMA, K. N. SATO, K. NAKAMURA, H. IDEI, M. HASEGAWA, H. NAKASHIMA, A. HIGASHIJIMA, Particle Recycling in the Compact Plasma wall interaction Device 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.
157. 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.
158. 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..
159. 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.
160. K. N. SATO, H. ZUSHI, K. HANADA, K. NAKAMURA, M. SAKAMOTO, H. IDEI, M. HASEGAWA, Y. HIGASHIZONO, S. KAWASAKI, H. NAKASHIMA, A. HIGASHIJIMA, ALL JAPAN ST RESEARCH GROUP, Project of Long Term Sustained Spherical Tokamak “QUEST”, Proceedings of the Joint Meeting of 4th IAEA Technical Meeting on Spherical Tori 14th International Workshop on Spherical Torus, （※）, 2008.10.
161. 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.
162. 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.
163. 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..
164. 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..
165. 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..
166. 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..
167. Xu, Handong; Hanada, Kazuaki; Hasegawa, Makoto; Zushi, Hideki; Nakamura, Kazuo;Sato, N;Sakamoto, Mizuki;Idei, Hiroshi;TRIAM Group, The plasma current control in the TRIAM-1M tokamak, 九州大学大学院総合理工学府，Interdisciplinary Graduate School of Engineering Sciences，Kyushu University, Vol. 29, No. 4, Pages 365-368, 2008.03.
168. 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..
169. 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..
170. 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..
171. 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..
172. 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.
173. 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..
174. 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, 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..
175. 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..
176. 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, 0.0, 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)..
177. 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..
178. Yoshinaga, T; Hanada, K; Sato, K; Nakamura, K; Zushi, H; Idei, H; Sakamoto, M; Hasegawa, M;, Non-Inductive Plasma Current Start-up Experiment by Electron Cyclotron Heating in the CPD Device, The Korean Vacuum Soiety, 185-185, 2007.08.
179. 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..
180. 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..
181. 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..
182. 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..
183. 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..
184. 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..
185. 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..
186. M. Sakamoto, M. Ogawa, M. Tokitani, H. Zushi, K. Tokunaga, N. Yoshida, K. Nakamura, K. Hanada, K. N. Sato, H. Idei, M. Hasegawa, M. Miyamoto, S. Kawasaki, H. Nakashima, T. Fujiwara, A. Higashijima, B. Rajendraprasad, K. Sasaki, Global Wall Recycling and Hydrogen Retention in Co-deposites in Long Duration Discharges on TRIAM-1M, Proc. 5th IAEA Technical Meeting on Steady State Operation of Magnetic Fusion Devices, 2007.05.
187. 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.
188. 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 [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..
189. 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.
190. 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.
191. 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.
192. 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..
193. 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, #<:excel::error:0xaf79bd0>-#<:excel::error:0xaf79ae0>, 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..
194. 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.
195. 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..
196. 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.
197. 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.
198. Ｍ. Ogawa, M. Sakamoto, K. N. Sato, H. Zushi, K. Nakamura, K. Hanada, H. Idei, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, and TRIAM group, Effect of repetition of discharges on oxygen impurity behavior in long duration discharge on TRIAM-1M, Proc. International Conference on Plasma Surface Interactions in ControlledFusion Device，Hefei Anhui，China(2006), 2006.05.
199. H. Zushi, K. Hanada, H. Idei, M. Hasegawa, K. Sasaki, R. Bhattacharyay, M. Sakamoto, K. Nakamura, K. N. Sato, S. Kawasaki, H. Nakashima, A. Higashijima, ELECTRON CYCLOTRON COUNTER CURRENT DRIVE EXPERIMENTS IN BI-DIRECTIONAL LOWER HYBRID CURRENT DRIVE PLASMA IN TRIAM-1M, 14th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, Thira, Santorini Island, Greece, 9-12 May 2006, 2006.05.
200. 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..
201. 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..
202. 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, 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..
203. 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, 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..
204. 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, 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..
205. 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..
206. 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..
207. 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, #<:excel::error:0xc0d6cc0>-#<:excel::error:0xc0d6acc>, 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..
208. H. Zushi, K. Nakamura, K. Hanada, K. N. Sato, M. Sakamoto, H. Idei, M. Hasegawa, A. Iyomasa, S. Kawasaki, H. Nakashima, A. Higashijima, T. Kuramoto1, A. Tanaka1, Y. Matsuo1, K. Esaki1, H. Akanishi, T. Sugata1, H. Hoshika, K. Sasaki, N. Maezono, M. Kitaguch, Steady-state tokamak operation，ITB transition and sustainment and ECCD experiments in TRIAM-1M, NUCLEAR FUSION, 45，10（※Vol.45 S142-S156）, 2005.10.
209. 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.
210. 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.
211. 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.
212. 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.
213. 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.
214. 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.
215. 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.
216. 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.
217. 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
218. Nakamura, K; Ji, ZS; Shen, B; Qin, PJ; Itoh, S; Hanada, K; Sakamoto, M; Jotaki, E; Hasegawa, M; Iyomasa, A; Kawasaki, S; Nakashima, H, Magnetic sensorless sensing of plasma position in the superconducting tokamak HT-7, PLASMA SCIENCE & TECHNOLOGY, 10.1088/1009-0630/6/5/006, 6.0, 5.0, 2459.0-2462.0, 0.0, 2004.10, Magnetic sensorless sensing experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The horizontal position is calculated from the vertical field coil current and voltage without using signals of magnetic probes placed nearby a plasma. The calculations are focused on the ripple frequency component of the power supply. There is no drift problem with the time integration of magnetic probe signals. The error of the derived plasma position is lower than 2% of the plasma minor radius..
219. 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
220. 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.
221. Sakamoto, M; Yuno, M; Itoh, S; Hanada, K; Nakamura, K; Zushi, H; Jotaki, E; Hasegawa, M; Kulkarni, S; Iyomasa, A; Kawasaki, S; Nakashima, H, Global particle balance and wall recycling properties of long duration discharges on TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/44/7/001, 44.0, 7.0, 693.0-698.0, PII S0029-5515(04)79641-6, 2004.07, The longest tokamak discharge, with a duration of 11406 s (3 It 10 min), has been achieved. The global particle balance has been investigated. In the longest discharge, the global balance between the particle absorption and release of the wall was achieved at t similar to 30 min. After that, the plasma density was maintained by the recycling flux alone until the end of the discharge. The maximum wall inventory is about 3.6 x 10(20) H at t similar to 30 min, but it is finally released from the wall at the end of the discharge. The hydrogen release seems to be caused by the temperature increase in the whole toroidal area of the main chamber. Moreover, it has been observed that there is a large difference between the properties of wall recycling in the continuous gas feed case (i.e. static condition) and in the additional gas puff case (i.e. dynamic condition). In the static condition, the effective particle confinement time increases to similar to 10 s during the I min discharge and it increases to similar to 100 s before the global balance in the longest discharge. In the dynamic condition, the decay time of the electron density just after the gas puff, i.e. the effective particle confinement time, is constant at 0.2-0.3 s during the discharge. The large difference in the effective particle confinement time between the static and dynamic conditions seems to be caused by the reduction in the recycling coefficient due to the enhanced wall pumping resulting from the additional gas puff..
222. 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.
223. 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, 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..
224. Hanada, K; Nakamura, K; Hasegawa, M; Itoh, S; Zushi, H; Sakamoto, M; Jotaki, E; Kulkarni, SV; Iyomasa, A; Kawasaki, S; Nakashima, H; Yoshida, N; Tokunaga, K; Fujiwara, T; Mitarai, O, Current ramp-up experiments in full current drive plasmas in TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/44/2/019, 44.0, 2.0, 357.0-361.0, PII S0029-5515(04)74023-5, 2004.02, Four types of plasma current ramp-up experiments in full non-inductively lower hybrid current driven (LHCD) plasmas were executed in TRIAM-1M: (1) current start-up by a combination of electron cyclotron resonance heating (ECRH) and LHCD, (2) tail heating by additional LHCD, (3) bulk heating by ECRH and (4) spontaneous ramp-up by a transition to enhanced current drive (ECD) mode. The time evolutions of plasma current during four types of ramp-up phase were adjusted by a simple model with two different time constants, which are a time defined by the total current diffusion time and a time constant for improving the current drive efficiency. In the case of (1) and (4), the latter time constant is significant during the current ramp-up phase. The improvement in the current drive efficiency in the ECD mode is likely to be caused by the increase in the effective refractive index along the magnetic field of the lower hybrid wave..
225. 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.
226. 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. Maez, Overview of steady state tokamak operation and current drive experiments in TRIAM-1M, Proc. 20th IAEA Fusion Energy Conference, IAEA-CN-116-OV5-2, 2004.01.
227. M. Hasegawa, K. Hanada, S. Itoh, K. Nakamura, H. Zushi, M. Sakamoto, E. Jotaki, S. V. Kulkarni, A. Iyomasa, S. Kawasaki, H. Nakashima, K. Nagasaki, Plasma Experiments Using a New 170GHz EC System and a Simple Model for Plasma Production, JOURNAL OF NUCLEAR MATERIALS, Vol.80, No.1 pp.53-58, 2004.01.
228. 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.
229. Zushi, H; Itoh, S; Hanada, K; Nakamura, K; Sakamoto, M; Jotaki, E; Hasegawa, M; Pan, YD; Kulkarni, SV; Iyomasa, A; Kawasaki, S; Nakashima, H; Yoshida, N; Tokunaga, K; Fujiwara, T; Miyamoto, M; Nakano, H; Yuno, M; Murakami, A; Nakamura, S; Sakamoto, N; Shinoda, K; Yamazoe, S; Akanishi, H; Kuramoto, K; Matsuo, Y; Iwamae, A; Fuijimoto, T; Komori, A; Morisaki, T; Suzuki, H; Masuzaki, S; Hirooka, Y; Nakashima, Y; Mitarai, O, Overview of steady state tokamak plasma experiments in TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/43/12/006, 43.0, 12.0, 1600.0-1609.0, PII S0029-5515(03)71915-2, 2003.12, An overview of steady state tokamak studies in TRIAM-IM (R-0 = 0.8 m, a x b = 0.12 m x 0.18 m and B = 8 T) is presented. The current ramp-up scenario without using centre solenoid coils is reinvestigated with respect to controllability of the current ramp-up rate at the medium density region of (1-2) x 10(19) m(-3). The plasma is initiated by ECH (fundamental o-mode at 170 GHz with 200 kW) at B = 6.7 T, and the ramp-up rate below the technical limit of 150 kA s(-1) for ITER can be achieved by keeping the LH power less than 100 kW during the current ramp-up phase. The physics understanding of the enhanced current drive (ECD) mode around the threshold power level has progressed from a viewpoint of transition probability. A transition frequency, f(trans), for the ECD transition is determined as a function Of P-CD. At similar to70 kW no transition occurs for an f(trans), value of similar to0.017 Hz, meaning almost zero transition probability. With increasing P-CD > P-th, f(trans) increases up to 10 Hz, and the transition tends to occur with high probability. The record value of the discharge duration is updated to 3 h 10 min in a low (n) over tilde (e) similar to 1 x 10(18) m(-3) and low power (
230. H. Zushi, S. Itoh, N. Yoshida, K. Hanada, K. Nakamura, M. Sakamoto, E. Jotaki, M. Hasegawa, K. Tokunaga, A. Iyomasa, A. Iwamae, Y. Hirooka, Physics and Technological Issues for Steady-State Tokamak Operation on TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, Vol.79, pp.1302-1316, 2003.12.
231. Nakamura, K; Ji, ZS; Shun, B; Qin, PQ; Itoh, S; Hanada, K; Sakamoto, M; Jotaki, E; Hasegawa, M; Iyomasa, A; Kawasaki, S; Nakashima, H, Sensorless sensing of plasma horizontal position on HT-7, FUSION ENGINEERING AND DESIGN, 10.1016/S0920-3796(03)00308-9, #<:excel::error:0xacee67c>, 0.0, 771.0-777.0, 0.0, 2003.09, Sensorless sensing experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The horizontal position is calculated from the vertical field coil current and voltage in two ways. The calculations are made focusing on the low frequency component and the ripple frequency component of the power supply. In the latter case, there is no drift problem and the error is lower than 2% of the plasma minor radius. (C) 2003 Elsevier Science B.V. All rights reserved..
232. T. KURAMOTO, H. ZUSHI, S. NAKAMURA, K. HANADA, K. SHINODA, M. SAKAMOTO, K. NAKAMURA, M. HASEGAWA, A. IYOMASA, S. KAWASAKI, H. NAKASHIMA, The effects of the hot spot on sustainment of LHCDplasma on TRIAM-1M, 30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, P-2.125, 27A, P-2.125, 2003.07.
233. S. Itoh, E. Jotaki, K. Nakamura, M. Sakamoto, K. Hanada, H. Zushi, M. Hasegawa, S. Kawasaki, H. Nakasima, Current Ramp-up Experiments Using ECRW on TRIAM-1M, Juornal of Plasma and Fusion Science, 79.0, 4.0, 413.0-419.0, Vol. 79, No. 4, pp.413-419, 2003.04, The operation of tokamak devices is based on the principle of the transformer, so it has been considered that pulse operation of such devices is inevitable. But the superconducting high-field tokamak TRIAM-1M has been demonstrated continuous operation for last 15 years and succeeded in sustaining 3 hours of constant operation in 2001. Fusion reactors of the future will use the center solenoid (CS) coil only in the ramp-up phase of the plasma current. If the coil is removed from the tokamak device, the device can be simplified and its cost will be decreased. In TRIAM-1M experiments, a perfect CS-free ramp-up was demonstrated and succeeded in sustaining the plasma current longer than 30 s. In this paper, the operation scenario, especially plasma position control, and the results of the analysis of plasma control are described..
234. L. G.Bruskin, N. Oyama, K. Shinohara, Y. Miura, Y. Kogi, A. Mase, M. Hasegawa, K. Hanada, Measurements of density fluctuations in reflectometry of cylindrical plasmas, REVIEW OF SCIENTIFIC INSTRUMENTS, 74.0, 3.0, 1473.0-1476.0, 2003.03, An analytical model of fluctuationreflectometry is developed, which is capable of handling the plasma profiles of arbitrary shape and curvature. The experimental profiles are piece-wise approximated by the functions, which allow for the integration of the full-wave O-mode equation. The model is applied to the reflectometry of the JT-60U tokamak plasma to provide a preliminary estimation of the fluctuation amplitude and spectral width..
235. Bruskin, LG; Oyama, N; Shinohara, K; Miura, Y; Kogi, Y; Mase, A; Hasegawa, M; Hanada, K, Measurements of density fluctuations in reflectometry of cylindrical plasmas, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.1538355, 74.0, 3.0, 1473.0-1476.0, 0.0, 2003.03, An analytical model of fluctuation reflectometry is developed, which is capable of handling the plasma profiles of arbitrary shape and curvature. The experimental profiles are piece-wise approximated by the functions, which allow for the integration of the full-wave O-mode equation. The model is applied to the reflectometry of the JT-60U tokamak plasma to provide a preliminary estimation of the fluctuation amplitude and spectral width. (C) 2003 American Institute of Physics..
236. Sakamoto, M; Nakashima, H; Kawasaki, S; Iyomasa, A; Kulkarni, SV; Hasegawa, M; Jotaki, E; Zushi, H; Nakamura, K; Hanada, K; Itoh, S, Static and dynamic properties of wall recycling in TRIAM-1M, JOURNAL OF NUCLEAR MATERIALS, 10.1016/S0022-3115(02)01390-9, 313.0, 0.0, 519.0-523.0, PII S0022-3115(02)01390-9, 2003.03, A large difference between properties of wall recycling in the continuous gas feed case (i.e. static condition) and the additional gas puff case (i.e. dynamic condition) has been observed. In the static condition, the effective particle confinement time, tau(p)(*), increases almost linearly to about 10 s during the I min discharge. In the dynamic condition, tau(p)(*) is 0.2-0.3 s during the I min discharge. This difference of tau(p)(*) is also confirmed in the ultra-long discharge. tau(p)(*) in the static condition becomes similar to100 s before the global balance between particle absorption and release of the wall is achieved at t similar to30 min. tau(p)(*) in the dynamic condition is, however, still on the order of similar to0.3 s. The large difference between tau(p)(*) in the static and dynamic conditions is attributed to a reduction in the recycling coefficient due to enhanced wall pumping resulting from the gas puff. (C) 2003 Elsevier Science B.V. All rights reserved..
237. Takase, Y; Aramasu, M; Ejiri, A; Kasahara, H; Ohara, S; Shiraiwa, S; Yamada, T; Hanada, K; Hasegawa, M; Hoshika, H; , EBW and Outer PF Start-up on the TST-2 Spherical Tokamak, APS Meeting Abstracts, 1.0, 1063.0, 2003.01.
238. M. Sakamoto, H. Nakashima, S. Kawasaki, A. Iyomasa, S. V. Kulkarni, M. Hasegawa, E. Jotaki, H. Zushi, K. Nakamura, K. Hanada, S. Itoh, Static and dynamic properties of wall recycling in TRIAM-1M, Proc. 15th Int. Conf. on Plasma Surface Interaction (Gifu) (to be published in J. Nucl. Material), 313.0, 313.0, 2003.01.
239. K. Hanada, K. Nakamura, M. Hasegawa, S. Itoh, H. Zushi, M. Sakamoto, E. Jotaki, S. V. Kulkarni, A. Iyomasa, S. Kawasaki, H. Nakashima, N. Yoshida, K. Tokunaga, T. Fujiwara and O. Mitarai, Current ramp-up experiments in full current drive plasmas on TRIAM-1M, 19th IAEA Fusion Energy Conference, IAEA-CN-94/EX/P4-15, 2002.11.
240. M. Sakamoto, M. Yuno, S. Itoh, K. Hanada, K. Nakamura, H. Zushi, E. Jotaki, M. Hasegawa, S. V. Kulkani, A. Iyomasa, S. Kawasaki, H. Nakashima, Global particle balance and wall recycling properties of long duration discharges on TRIAM-1M, 19th IAEA Fusion Energy Conference, IAEA-CN-94/EX/P4-07, 2002.10.
241. Hiromasa Ninomiya, Akio Kitsunezaki, Masatsugu Shimizu, Masaaki Kuriyama, JT-60 Team, Haruyuki Kimura, Hisato Kawashima, Kazuhiro Tsuzuki, Masayasu Sato, Nobuaki Isei, Yukitoshi Miura, Katsumichi Hoshino, Kensaku Kamiya, Toshihide Ogawa, Hiroaki Ogawa, Kengo Miyachi, JFT-2M Group, Satoshi Itoh, Naoaki Yoshida, Kazuaki Hanada, Kazuo Nakamura, Hideki Zushi, Mizuki Sakamoto, Eriko Jotaki, Makoto Hasegawa, TRIAM Group, Research Activities on Tokamaks in Japan: JT-60U, JFT-2M, and TRIAM-1M, FUSION SCIENCE AND TECHNOLOGY, 42.0, 1.0, 7.0-31.0, 2002.07, Research activities of the Japanese tokamaks JT-60U, JFT-2M, and TRIAM-1M are described. The recent JT-60 program is focused on the establishment of a scientific basis of advanced steady-state operation. Plasma performance in transient and quasi steady states has been significantly improved, utilizing reversed shear and weak shear (high-p) ELMy H-modes characterized by both internal and edge transport barriers and high bootstrap current fractions. Development of each key issue for advanced steady-state operation has also been advanced. Advanced and basic research of JFT-2M has been performed to develop high-performance tokamak plasma as well as the structural material for a fusion reactor. Toroidal field ripple reduction with ferritic steel plates outside the vacuum vessel is successfully demonstrated. No adverse effects to the plasma were observed with poloidal fields inside the vacuum vessel (partial covering). Preparation is in progress for full-scale testing of the compatibility of the ferritic steel wall (full covering) with plasma. A heavy ion beam probe has been installed to study H-mode plasmas. Compact toroid (CT) injection experiments are performed, showing deep CT penetration into the core region of the H-mode. The TRIAM project has investigated steady-state operation and high-performance plasma of a tokamak with the high toroidal magnetic field superconducting tokamak. Four important contributions in the fields of fusion technology of superconducting tokamaks, steady-state operation, high-performance plasma, and startup of plasma current without the assistance of center solenoid coils have been achieved on TRIAM-1M, especially regarding steady-state operation by realization of a discharge for >3 h..
242. H. Zushi, S. Itoh, K. Hanada, K. Nakamura, M. Sakamoto, E. Jotaki, M. Hasegawa, Y. D. Pan, S. V. Kulkarni, A. Iyomasa, S. Kawasaki, H. Nakashima, N. Yoshida, K. Tokunaga, T. Fujiwara, M. Miyamoto, H. Nakano, M. Yuno, A. Murakami, S. Nakamura, N. Sakamoto, K. Shinoda, S. Yamazoe, H. Akanishi, K. Kuramoto, Y. Matsuo, A. Iwamae, T. Fuijimoto, A. Komori, T. Morisaki, H. Suzuki, S. Masuzaki, Y. Hirooka, Y. Nakashima and O. Mitarai, Overview of Steady State Tokamak Plasma Experiments on TRIAM-1M, 19th IAEA Fusion Energy Conference(Lyon，2002), 43，12（※19th IAEA Fusion Energy Conference(Lyon，2002) IAEA-CN-94/OV/4-6.）, 2002.03.
243. K. Hanada, Y. Shinoda, M. Sakamoto, S. Itoh, K. Nakamura, H. Zushi, E. Jotaki, M. Hasegawa, S. V.Kulkarni, S. Kawasaki, H. Nakashima, A. Iyomasa, N. Yoshida, K. Tokunaga, T. Fujiwara, Measurement of prompt loss of energetic electrons in a long LHCD discharge on TRIAM-1M, 29th European Physical Society Conference on Plasma Physics and Controlled Fusion, P-2.085, 2002.01.
244. SAKAMOTO Mizuki, ITOH Satoshi, NAKAMURA Kazuo, ZUSHI Hideki, HANADA Kazuaki, JOTAKI Eriko, HASEGAWA Makoto, PAN Yudong, KAWASAKI Shoji and NAKASHIMA Hisatoshi, Wall Recycling on the Superconducting Tokamak TRIAM-1M, Journal of Plasma and Fusion Research, 78.0, 1.0, 52.0-58.0, 2002.01.
245. Hanada, K; Itoh, S; Nakamura, K; Zushi, H; Sakamoto, M; Jotaki, E; Pan, YD; Hasegawa, M; Kawasaki, S; Nakashima, H, Enhanced current drive efficiency in a long discharge on TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/41/11/302, 41.0, 11.0, 1539.0-1542.0, 2001.11, The enhanced current drive (ECD) efficiency mode, which is characterized by a spontaneous increase of current drive efficiency eta (CD) from (0.3-0.4) x 10(19) A/W m(-2) to (0.6-1.0) x 10(19) A/W M(-2), is observed in long pure LHCD plasmas on TRIAM-1M. The energy confinement time is also improved due to the increase of line averaged electron density, and of the ion and electron temperatures. The current drive efficiency is proportional to the electron density. The transition to ECD mode occurs at a critical density, which depends slightly on the refractive index in the toroidal direction N(parallel to) of the injected wave..
246. Zushi, H; Itoh, S; Nakamura, K; Sakamoto, M; Hanada, K; Jotaki, E; Pan, YD; Hasegawa, M; Kawasaki, S; Nakashima, H, Steady state experiments on current profile control and long sustainment of high performance LHCD plasmas on the superconducting tokamak TRIAM-1M, NUCLEAR FUSION, 10.1088/0029-5515/41/10/315, 41.0, 10.0, 1483.0-1493.0, 0.0, 2001.10, The main purpose of TRIAM-1M (R-0 = 0.8 m, a x b = 0.12 m x 0.18 m, B = 8 T) is to study the route towards a high field compact steady state fusion reactor. In the advanced steady state operation programme, a heating mechanism for the high ion temperature mode with an internal transport barrier has been studied, an enhanced current drive mode in an extended (higher power and higher density) operation regime has been obtained, current density profile control experiments using multicurrent drive systems have been performed and the effects of wall recycling, wall pumping and wall saturation on particle control have been investigated..
247. K. Hanada, S. Itoh, K. Nakamura, H. Zushi, M. Sakamoto, E. Jotaki, Y. D. Pan 1), M. Hasegawa, S. Kawasaki, H. Nakashima, New Transition Phenomena in a Long Discharge on TRIAM-1M, 18th IAEA Fusion Energy Conference (Sorrento)，IAEA-CN-77/EXP5/25, IAEA-CN-77/EXP5/26, 2000.10.
248. Zushi, H; Itoh, S; Nakamura, K; Sakamoto, M; Hanada, K; Jotaki, E; Pan, YD; Hasegawa, M; Kawasaki, S; Nakashima, H;, Steady State Experiments on High Performance，Current Profile Control and Long Sustainment of LHCD Plasmas on the Superconducting Tokamak TRIAM-1M, 18th IAEA Fusion Energy Conference (Sorrento)，IAEA-CN-77/OV5/3, IAEA-CN-77/OV5/3 (2000), 2000.10.
249. K Shinohara, K Hoshino, S Shiraiwa, K Hanada, H Toyama, Y Miura, N Suzuki, K Yamagishi, T Oikawa, H Totsuka, E Ishiyama, N Shinoda, M Hasegawa, H Saito, Y Endo, Measurement of density fluctuations by JFT-2M reflectometer, FUSION ENGINEERING AND DESIGN, 34.0, 433-436, 34，433-436, 1997.03.
250. K. Hanada, M. Hasegawa, K. Shinohara, S. Ohdachi, T. Shoji, Y. Miura, H. Tamai, T. Oikawa, H. Totsuka, E. Ishiyama, N. Shinoda, S. Shiraiwa, H. Saito, Y. Endo, K. Yamagishi, H. Toyama, H-L Transition caused by Irregular Probe Insertion in the JFT-2M Tokamak, PLASMA PHYSICS AND CONTROLLED FUSION, 38.0, 8.0, 1255.0-1259.0, 1996.08.
251. H. Toyama, K. Hanada, K. Yamagishi, T. Oikawa, K. Shinohara, H. Totsuka, E. Ishiyama, H. Saito, S. Shiraiwa, M. HAsegawa, I. Nakajima, M. Ushigome, Helicity Injection Experiments and Turbulence Measurements on the Spherical Tokamak TST, Proc. 16th IAEA Fusion Energy Conference，Montreal (Canada)，Vol.2 223-228，1996, 1996.01.
252. K. Hanada, M. Hasegawa, K. Shinohara, S. Ohdach, et al. (Total 52), Investigation of Causality in H-L Transition on the JFT-2M Tokamak, Proc. 16th IAEA Fusion Energy Conference，Montreal (Canada)，Vol.1 885-890，1996, 885.0-890.0, 1996.01.
253. Sasaki, K; Hanada, K; Sato, KN; Zushi, H; Nakamura, K; Sakamoto, M; Idei, H; Hasegawa, M; Kawasaki, S; Nakashima, T; , Soft X-ray measurement in IRE on the TST-2 tokamak, 16th International Toki Conference, P6-28, 1904.01.


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