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Sakamoto, Keishi; Kasugai, Atsushi; Minami, Ryutaro; Takahashi, Koji; Kobayashi, Noriyuki*
Journal of Physics; Conference Series, 25, p.8 - 12, 2005/00
The present status of ITER gyrotron development of JAERI is reported. Up to now, we demonstrated 100 sec operation at 0.5 MW level power output. On the other hand, some issues were recognized for CW operation, i.e., the beam current decreased as pulse duration expanded. And the large amount of stray RF of 170 GHz exists in the gyrotron. Former, pre-programming control of the heater power of electron gun was introduced to keep the beam current constant. Latter, the inner surface of the radiator was optimized to minimize the diffraction, and loss was reduced by 1/5. Prior to the RF pulse extension, we tried an electron beam test without RF oscillation. As a result, the constant beam current was demonstrated up to 1000 sec.
Kasugai, Atsushi; Minami, Ryutaro; Takahashi, Koji; Kobayashi, Noriyuki*; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Hayashi, Kenichi*; Sakamoto, Keishi
Shingaku Giho, 104(520), p.37 - 42, 2004/12
no abstracts in English
Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Hoshi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi
Proceedings of 2004 International Symposium on Microwave Science and Its Application to Related Fields (Microwave 2004), p.527 - 530, 2004/07
An electron cyclotron current drive (ECCD) system is, especially, necessary to suppress the neoclassical tearing mode instability in ITER. The polarizers are one of the important components in the ECCD system, to generate optimum polarization for an efficient ECCD. An ohmic loss of the polarizers is evaluated, when 170GHz, high power RF wave taransmits, in oreder to investigate its performance. The maximum temperature increase on the back plate of the deep grooved and the conventinal type were 65
C and 30C, respectively. RF power and pulse were 441kW and 6sec, respectively. The dependence of temperature increase on the plolarizer angle obtained in the experiment agrees with the calculation, qualitatively. It was also found that the significant reduction of ohmic loss on the polarizers was achievable with the optimized rotation angle of the linearly polarized incident wave.
Takahashi, Koji; Moeller, C. P.*; Sakamoto, Keishi; Hayashi, Kenichi*; Imai, Tsuyoshi
Fusion Engineering and Design, 65(4), p.589 - 598, 2003/07
Times Cited Count：22 Percentile：78.49(Nuclear Science & Technology)High power radiation experiments of a remote steering launcher for an EC H&CD system were carried out to study the characteristic of the rf beam steering and transmission. The remote steering launcher consists of a 4.632m corrugated square waveguide (45.7 
45.7mm
) and a movable flat mirror which is placed at the input of the waveguide. Measurements were made in the range 0-10 at a frequency of 170GHz. The measured radiation pattern is clearly a Gaussian-like distribution, which is in agreement with the low power measurements. A steering capability of up to 10 was experimentally confirmed. Transmission and radiation of 0.5 MW-3.0 sec and 0.2 MW-10.0 sec pulses were successfully demonstrated over a steering angle range of 0-10. No arcing was observed during the experiments and no damage to the waveguide was found after the experiments were finished. We confirmed that remote steering was a possibly alternative scheme of rf beam steering for EC H&CD.
Sakamoto, Keishi; Kasugai, Atsushi; Ikeda, Yoshitaka; Hayashi, Kenichi*; Takahashi, Koji; Moriyama, Shinichi; Seki, Masami; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Fujii, Tsuneyuki; et al.
Nuclear Fusion, 43(7), p.729 - 737, 2003/07
Development of high power gyrotrons at 170GHz and 110GHz have beed carried out. At 170GHz gyrotron that is required for ITER, high power outputs of 0.9MW/9sec, 0.75MW/17sec, 0.5MW/30sec, 0.3MW/60sec have been obtained. At 110GHz gyrotron for JT-60U, 1.2MW/4sec was obtained. The 110GHz gyrotron is under operation at 4MW electron cyclotron heating and current drive system on JT-60U.
Takahashi, Koji; Moeller, C. P.*; Kasugai, Atsushi; Minami, Ryutaro; Sakamoto, Keishi; Imai, Tsuyoshi
Proceedings of 28th International Conference on Infrared and Millimeter Waves, p.385 - 386, 2003/00
no abstracts in English
Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Kashiwa, Yoshitada*; Hoshi, Yuki*; Kobayashi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi
Proceedings of IAEA TM on ECRH Physics and Technology for ITER (CD-ROM), 7 Pages, 2003/00
The specified elliptical polarization which is necessary to excite a pure ordinary or extraordinary mode, when rf waves obliquely propagate in plasma, for electron cyclotron current drive(ECCD) can be produced by a grooved mirror polarizer. The Joule loss of deeped groove mirrors has been experimentally investigated at a frequency of 170 GHz. The strange dependence of the Joule loss of groove mirror on the mirror rotation angle was obtained. In addition, maximum loss of 0.8% in regard to the injection rf power to the mirrors was estimated. The calculation code to estimate the Joule loss of grooved mirror is developed for the structure analysis. The dependence of the mirror on its rotation angle can be explained by the calculation results, clearly.
Takahashi, Koji; Imai, Tsuyoshi; Sakamoto, Keishi; Kobayashi, Noriyuki*; Mori, Seiji*; Mori, Kensuke*; Ito, Yasuyuki*; Shoyama, Hiroaki; Kasugai, Atsushi
Fusion Engineering and Design, 56-57, p.587 - 592, 2001/10
Times Cited Count：7 Percentile：48.68(Nuclear Science & Technology)no abstracts in English
mode with depressed collectorShoyama, Hiroaki; Sakamoto, Keishi; Hayashi, Kenichi*; Kasugai, Atsushi; Tsuneoka, Masaki; Takahashi, Koji; Ikeda, Yukiharu; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Imai, Tsuyoshi
Japanese Journal of Applied Physics, Part 2, 40(8B), p.L906 - L908, 2001/08
Times Cited Count：28 Percentile：71.93(Physics, Applied)no abstracts in English
Sakamoto, Keishi; Kasugai, Atsushi; Shoyama, Hiroaki; Hayashi, Kenichi*; Takahashi, Koji; Tsuneoka, Masaki; Ikeda, Yukiharu; Ikeda, Yoshitaka; Kajiwara, Ken; Moriyama, Shinichi; et al.
25th International Conference on Infrared and Millimeter Waves Conference Digest, p.11 - 12, 2000/00
no abstracts in English
Sakamoto, Keishi; Kasugai, Atsushi; Tsuneoka, Masaki; Takahashi, Koji; Imai, Tsuyoshi; *; Mitsunaka, Yoshika*
Review of Scientific Instruments, 70(1), p.208 - 212, 1999/01
Times Cited Count：68 Percentile：94.42(Instruments & Instrumentation)no abstracts in English
Takahashi, Koji; Sakamoto, Keishi; Kasugai, Atsushi; Tsuneoka, Masaki; ; Imai, Tsuyoshi; *; Mitsunaka, Yoshika*
Fusion Technology 1998, 1, p.415 - 418, 1998/00
no abstracts in English
Sakamoto, Keishi; Kasugai, Atsushi; Tsuneoka, Masaki; ; Imai, Tsuyoshi; *; Hayashi, Kenichi*; Mitsunaka, Yoshika*; Hirata, Yosuke*; *; et al.
Proceedings of 17th IEEE/NPSS Symposium Fusion Engineering (SOFE'97), 1, p.441 - 444, 1998/00
no abstracts in English
Sakamoto, Keishi; Kasugai, Atsushi; Tsuneoka, Masaki; Takahashi, Koji; ; Imai, Tsuyoshi; *; Hayashi, Kenichi*; Mitsunaka, Yoshika*; Hirata, Yosuke*; et al.
22nd International Conference on Infrared and Millimeter Waves Conference Digest, p.106 - 107, 1997/00
no abstracts in English
Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Tsuneoka, Masaki; Imai, Tsuyoshi; Kariya, Tsuyoshi*; Hayashi, Kenichi*
Journal of the Physical Society of Japan, 65(7), p.1888 - 1890, 1996/07
Times Cited Count：19 Percentile：81.95(Physics, Multidisciplinary)no abstracts in English
Kasugai, Atsushi; Sakamoto, Keishi; Tsuneoka, Masaki; Takahashi, Koji; Maebara, Sunao; Imai, Tsuyoshi; Kariya, Tsuyoshi*; Hayashi, Kenichi*; Mitsunaka, Yoshika*; Hirata, Yosuke*
Fusion Technology 1996, 1, p.549 - 552, 1996/00
no abstracts in English
