| 1. |
H. Idei , M. Sakaguchi , K. Mishra , T. Onchi , R. Ikezoe , O. Watanabe , Y. Tanaka , T. Saito , T. Ido , K. Hanada , 8.56-GHz quasi-optical launcher system with incident-mode selectivity on
the QUEST spherical tokamak, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2023.113479, 189 (2023) 113479, 2023.04, An 8.56-GHz quasi-optical launcher system with incident-mode selectivity was developed for non-inductive electron cyclotron (EC) plasma ramp-up and long-pulse sustainment, and effective bulk-electron heating on the Q-shu University experiment with steady-state spherical tokamak (QUEST). A novel polarization-selective system was proposed to conduct fundamental and second harmonic EC heating and current drive experiments with ordinary and extra-ordinary mode waves, respectively. Selectivity of the incident modes or polarizations was confirmed using the whole developed system at a low power level. A large-sized mirror launcher was developed to inject the beam whose size was as small as possible near the QUEST major radius. The designed mirror performance was checked using a three-dimensional electromagnetic-wave simulator and a low-power test. Ultimately, 0.15-m sized beams for both the two polarizations were successfully attained near the QUEST major radius, even in low-frequency applications with long propagation..  |
| 2. |
H. Idei, M. Fukuyama, S. Sakai, K. Mishra, K. Nishimura, R. Ikezoe, T. Onchi, T. Ido, Adaptive Capon beamforming for lensless electron cyclotron emission imaging with high spatial resolution, Review of Scientific Instruments, https://doi.org/10.1063/5.0101632, 93, 103531 (2022), 2022.10, Electron cyclotron emission (ECE) imaging diagnostics incorporating a lensless approach have been developed for measurements involving active spatial selectivity and direction-of-arrival estimation. The Capon method for adaptive-array analysis was proposed to improve the spatial resolution of the two-dimensional ECE imaging technique. Broadband noise source emissions were used to simulate the ECE to verify the practical effectiveness of the Capon method in the ECE imaging. Multiple noise source emission positions were properly estimated with a high spatial resolution using the Capon method.. |
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Idei, Hiroshi; Onchi, Takumi; Mishra, Kishore; Zushi, Hideki; Kariya, Tsuyoshi; Imai, Tsuyoshi; Watanabe, Osamu; Ikezoe, Ryuya; Hanada, Kazuaki; Ono, Masayuki; ejiri, akira; Qian, Jinping; Nakamura, K; Fujisawa, Akihide; Nagashima, Yoshihiko; Hasegawa, Makoto; Matsuoka, Keisuke; Fukuyama, Atsushi; Kubo, Shin; Yoshikawa, M; Sakamoto, Mizuki; Kawasaki, Shoji; Higashijima, Aki; Ide, Shunsuke; Takase, Yuichi; Murakami, Sadayoshi, Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ab4c12, Volume 60, Number 1, 2019.12, A 28 GHz system with a high-power gyrotron tube has been used for the QUEST spherical tokamak to form an over-dense plasma for electron Bernstein wave (EBW) heating and current drive with an 8.2 GHz-wave. Non-inductive high-density plasma ramp-up experiments with dual-frequency (dual-f ) electron cyclotron (EC) (8.2 GHz and 28 GHz) waves were conducted. A spontaneous density jump (SDJ) to an over-dense state was first observed as a bifurcation phenomenon in the dual-f wave experiment. The over-dense plasma on the 8.2 GHz wave was non-inductively ramped up to 25 kA, and was maintained for 0.4 s under stable plasma equilibrium after two such jumps in one shot. Heating to mildly energetic electrons and bulk electrons was observed even in the over-dense region. The electrostatic EBW heating effect on the mildly energetic electrons in the over-dense region is assessed following a dispersion analysis of the 8.2 GHz wave. The bulk electron heating effect observed is explained as heat exchange from mildly energetic electrons heated by the electrostatic EBW. Remarkably, a high hard-x-ray-radiation temperature of ~500 keV was also observed in tangential viewing for current-carrying electrons in the over-dense core region. Synergetic heating from the overlap of different 28 GHz EC harmonic resonances as well as higher harmonic heating is discussed for maintaining the highly energetic electrons in the over-dense core region. In addition, the SDJ process and mechanism are considered based on the discussion of the electron heating effects with the 8.2 GHz wave.. |
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H. Idei, T. Onchi, T. Kariya, T.I. Tsujimura, S. Kubo, S. Kobayashi, M. Sakaguchi, T. Imai, M. Hasegawa, K. Nakamura, K. Mishra, M. Fukuyama, M. Yunoki, S. Kojima, O. Watanabe, K. Kuroda, K. Hanada, Y. Nagashima, A. Ejiri, N. Matsumoto, M. Ono, A. Higashijima, T. Nagata, S. Shimabukoro, Y. Takase, A. Fukuyama, S. Murakami, 28-GHz ECHCD system with beam focusing launcher on the QUEST spherical tokamak, Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2019.02.027, 2019.02, New polarizer and launcher systems on a 28-GHz electron-cyclotron (EC) heating and current drive (HCD) system have been developed for non-inductive second-harmonic EC-plasma-current ramp-up in the QUEST spherical tokamak. A launcher system with two quasi-optical mirrors providing beam steering capability was designed to focus the incident beam to a small-sized waist of ∼0.05 m at the second-harmonic EC resonance layer. A relatively large focusing mirror was designed based on a Kirchhoff integral code developed to derive wave solutions. The focusing property of the launched beam was first confirmed with a 3-dimensional (3D) electromagnetic-wave simulator. Focusing characteristics were also checked at low-power test facilities, together with the steering capability. The performance of this launcher system was demonstrated to work as designed, and assembled in the QUEST device. The system was applied to the non-inductive second-harmonic EC plasma ramp-up experiments with no optimization required regarding the incident polarization. The results obtained for the non-inductive plasma ramp-up are also presented.. |
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Hiroshi Idei, T. Kariya, T. Imai, K. Mishra, Takumi Onchi, O. Watanabe, H. Zushi, Kazuaki Hanada, J. Qian, A. Ejiri, M. M. Alam, K. Nakamura, akihide fujisawa, Yoshihiko Nagashima, Makoto Hasegawa, K. Matsuoka, A. Fukuyama, S. Kubo, T. Shimozuma, M. Yoshikawa, M. Sakamoto, S. Kawasaki, H. Nakashima, A. Higashijima, S. Ide, T. Maekawa, Y. Takase, K. Toi, Fully non-inductive second harmonic electron cyclotron plasma ramp-up in the QUEST spherical tokamak, Nuclear Fusion, 10.1088/1741-4326/aa7c20, 57, 12, 2017.10, 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.. |
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Hiroshi Idei, K. Mishra, M. K. Yamamoto, M. Hamasaki, akihide fujisawa, Yoshihiko Nagashima, Y. Hayashi, Takumi Onchi, Kazuaki Hanada, H. Zushi, Adaptive-Array electron cyclotron emission diagnostics using data streaming in a software defined radio system, Journal of Instrumentation, 10.1088/1748-0221/11/04/C04010, 11, 4, 2016.04, Measurement of the Electron Cyclotron Emission (ECE) spectrum is one of the most popular electron temperature diagnostics in nuclear fusion plasma research. A 2-dimensional ECE imaging systemwas developed with an adaptive-Array approach. Aradio-frequency (RF) heterodyne detection system with Software Defined Radio (SDR) devices and a phased-Array receiver antenna was used to measure the phase and amplitude of the ECE wave. The SDR heterodyne system could continuously measure the phase and amplitude with sufficient accuracy and time resolution while the previous digitizer system could only acquire data at specific times. Robust streaming phase measurements for adaptive-Arrayed continuous ECE diagnostics were demonstrated using Fast Fourier Transform (FFT) analysis with the SDR system. The emission field pattern was reconstructed using adaptive-Array analysis. The reconstructed profileswere discussed using profiles calculated from coherent single-frequency radiation from the phase array antenna.. |
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H. Idei, K.Mishra, M.K.Yamamoto, A. Fujisawa, Y. Nagashima, M.Hamasaki, Y.Hayashi, T. Onchi, K.Hanada, H. Zushi, QUEST Team, Multiple Wall-Reflection Effect in Adaptive-array Differential-phase Reflectometry on QUEST, Journal of Instrumentation, 11, C01014, 2016.01, A phased array antenna and Software-Defined Radio (SDR) heterodyne-detection systems have been developed for adaptive array approaches in reflectometry on the QUEST. In the QUEST device considered as a large oversized cavity, standing wave (multiple wall-reflection) effect was significantly observed with distorted amplitude and phase evolution even if the adaptive array analyses were applied. The distorted fields were analyzed by Fast Fourier Transform (FFT) in wavenumber domain to treat separately the components with and without wall reflections. The differential phase evolution was properly obtained from the distorted field evolution by the FFT procedures. A frequency derivative method has been proposed to overcome the multiple-wall reflection effect, and SDR super-heterodyned components with small frequency difference for the derivative method were correctly obtained using the FFT analysis.. |
| 8. |
Idei, Hiroshi; Kawasaki, Shohji; Zushi, Hideki; Inagaki, Shigeru; Nagayama, Yoshio; Kawahata, Kazuo; Wataya, Yuichi, Broadband radiometer system with fast frequency switching synthesizer for electron cyclotron emission measurements in LHD, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 380.0-381.0, 0.0, 2007.09, The broadband fast frequency-switching heterodyne radiometers have been developed to measure simultaneously three-band components of electron cyclotron emission with high time and frequency resolutions in the large helical device (LHD). The fast frequency-switching system was prepared as a local oscillator part of the heterodyne radiometers. The frequency switching time was 10 mu s. The fundamental electron cyclotron emission spectrum was successfully measured using the radiometer in the LHD experiment.. |
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Idei, Hiroshi; Kawasaki, Shouji; Hanada, Kazuaki; Zushi, Hideki; Sakamoto, Kohnosuke Sato Kazuo Nakamura Mizuki; Hasegawa, Makoto; Nakashima, Hisatoshi; Higashijima, Aki; Wataya, Yuichi; Matsubara, Shinji; Kawano, Shuhei, Initial results of AM reflectometory on CPD, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 0.0, 0.0, 518.0-519.0, 2007.09, The amplitude modulation reflectometer system has been developed to measure the density profile in detail on the Compact PWI ( plasma-wall interaction) Device (CPD) experiments. The probing frequency range was 6-18 GHz, and its frequency-switching time was 10 mu s in an arbitrary step. Using the broadband fast-scanning reflectometer, the wide-range density profile can be measured with high time resolution. In X-mode reflectometory, the developed system successfully measured the phase delay of propagating waves at 6.6, 8.8 and 13.2 GHz, reflected at the vessel wall of the CPD and the R-cutoff layers in the CPD plasma.. |
| 10. |
Idei, Hiroshi; Shapiro, Michael; Temkin, Richard J.; Shimozuma, Takashi; Kubo, Shin, Mode content analysis in circular corrugated waveguide using radiated field, 2007 JOINT 32ND INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 15TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, VOLS 1 AND 2, 0.0, 0.0, 69.0-70.0, 0.0, 2007.04, The fields radiated from the waveguide were used to analyze propagating mode content in an oversized circular corrugated waveguide. The radiated fields were calculated by the Kirchhoff Integral in the paraxial approximation. The irradiant waveguide modes of the radiated field are orthogonal within the paraxial approximation. The waveguide mode content was evaluated from the irradiant waveguide modes. The radiated intensity and phase profiles were directly measured with a vector network analyzer system at 84GHz for the analysis. The analyzed waveguide mode content was consistent with that excited in the waveguide, predicted by the coupling theory.. |
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Idei, Hiroshi; Shimozuma, Takashi; Shapiro, Michael A.; Notake, Takashi; Kubo, Shin; Temkin, Richard J., Experimental verification of phase retrieval of quasi-optical millimeter-wave beams, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, 10.1109/TMTT.2006.884632, 54.0, 11.0, 3899.0-3905.0, 2006.11, The accuracy of a phase-retrieval procedure for microwave beams was analyzed and verified using an 84-GHz quasi-optical beam transmitted by a corrugated waveguide. The output intensity and phase profiles of the beam were directly measured with a microwave receiver. The beam intensity was also measured at several planes and the data were used with a phase-retrieval algorithm to yield an independent estimate of the phase. Moment and matching coefficient methods were used to analyze the retrieved profiles. In the higher order moment analysis, the intensity profiles, which were calculated from the retrieved phase profiles, coincided well with the measured profiles in terms of the beam size, asymmetric property (skewness), and flatness/peakedness (kurtosis) over the entire profile. Analysis indicated that the mode content of the beam obtained by phase retrieval matched that of the direct measurement with a matching coefficient of 0.97 using both the intensity and phase profiles.. |
| 12. |
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.. |
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Wataya, Y.; Idei, H.; Inagaki, S.; Shimozuma, T.; Nagayama, Y.; Kawahata, K.; Zushi, H., Wide-band heterodyne-radiometer with fast frequency-switching local oscillator for electron cyclotron emission diagnostics, Conference Digest of the 2006 Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics, 0.0, 0.0, 501.0-501.0, 0.0, 2006.04, 0.0. |
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Idei, Hiroshi; Shimozuma, Takashi; Shapiro, Michael; Temkin, Richard; Notake, Takashi; Ito, Satoshi; Kubo, Shin; Ohkubo, Kunizo; , Quasi-optical beam analysis based on direct phase measurement at low power level, Journal of Plasma and Fusion Research, 81.0, 3.0, 186.0-190.0, 2005.01. |
