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Kobayashi, Takayuki; Sawahata, Masayuki; Terakado, Masayuki; Hiranai, Shinichi; Ikeda, Ryosuke; Oda, Yasuhisa; Wada, Kenji; Hinata, Jun; Yokokura, Kenji; Hoshino, Katsumichi; et al.
Proceedings of 40th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2015) (USB Flash Drive), 3 Pages, 2015/08
A gyrotron for electron cyclotron heating and current drive (ECH/CD) has been developed for JT-60SA (Super-Advanced). In high-power, long-pulse operations, oscillations of 1 MW/100 s have been demonstrated at both 110 GHz and 138 GHz, for the first time. These results fully satisfied the requirements for JT-60SA. Moreover, it was experimentally shown that the higher power operation at each frequency is expected to be acceptable for this gyrotron from the viewpoint of heat load at the cavity resonator, collector, and stray radiation absorbers. An oscillation at 82 GHz, which is an additional frequency, has been demonstrated up to 2 s at the output power of 0.4 MW, so far. High power experiments toward higher power of 1.5 MW (110/138 GHz) and 1 MW (82 GHz) are ongoing.
Kobayashi, Takayuki; Moriyama, Shinichi; Yokokura, Kenji; Sawahata, Masayuki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Hoshino, Katsumichi; et al.
Nuclear Fusion, 55(6), p.063008_1 - 063008_8, 2015/06
Times Cited Count：25 Percentile：77.57(Physics, Fluids & Plasmas)A gyrotron enabling high-power, long-pulse oscillations at both 110 GHz and 138 GHz has been developed for electron cyclotron heating (ECH) and current drive (CD) in JT-60SA. Oscillations of 1 MW for 100 s have been demonstrated at both frequencies, for the first time as a gyrotron operating at two frequencies. The optimization of the anode voltage, or the electron pitch factor, using a triode gun was a key to obtain high power and high efficiency at two frequencies. It was also confirmed that the internal losses in the gyrotron were sufficiently low for expected long pulse operation at the higher power level of 
1.5 MW. Another important result is that an oscillation at 82 GHz, which enables to use fundamental harmonic waves in JT-60SA while the other two frequencies are used as second harmonics waves, was demonstrated up to 0.4 MW for 2 s. These results of the gyrotron development significantly contribute to enhancing operation regime of the ECH/CD system in JT-60SA.
spp. under the ISS environmental conditions for performing exposure experiments of microbes in the Tanpopo missionKawaguchi, Yuko*; Yang, Y.*; Kawashiri, Narutoshi*; Shiraishi, Keisuke*; Takasu, Masako*; Narumi, Issey*; Sato, Katsuya; Hashimoto, Hirofumi*; Nakagawa, Kazumichi*; Tanigawa, Yoshiaki*; et al.
Origins of Life and Evolution of Biospheres, 43(4-5), p.411 - 428, 2013/10
Times Cited Count：41 Percentile：80.34(Biology)Tsuchida, Noriyuki*; Kawahata, Takuji*; Ishimaru, Eiichiro*; Takahashi, Akihiko*; Suzuki, Hiroshi; Shobu, Takahisa
ISIJ International, 53(7), p.1260 - 1267, 2013/07
Times Cited Count：24 Percentile：73.74(Metallurgy & Metallurgical Engineering)To investigate the tensile deformation behavior of a lean duplex stainless steel (S32101) from the viewpoints of plastic deformability among phases or grains, we performed static tensile tests, in situ neutron diffraction, and white X-ray diffraction experiments at room temperature. From the experimental results of synchrotron radiation white X-ray diffraction experiments, the hard phase of S32101 was changed from the ferrite phase to austenite one during tensile deformation. This led to a larger stress partitioning between the phases at the latter stage of deformation. From the experimental results of in situ neutron diffraction, it was found that the stress partitioning of the 
phase in the S32101 was the largest among the present results. Therefore, the larger work hardening rate of S32101 can be explained by the large stress partitioning of the phase, that between and 
phases and volume fraction.
Kobayashi, Takayuki; Isayama, Akihiko; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Sato, Fumiaki; Wada, Kenji; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; et al.
Fusion Engineering and Design, 86(6-8), p.763 - 767, 2011/10
Times Cited Count：6 Percentile：44.28(Nuclear Science & Technology)Progress of antenna development of the Electron Cyclotron Range of Frequency system for JT-60 SA is presented. Capability of pulse length of 100 s, which requires active cooling for mirrors, and flexibility of beam injection angles in both poloidal and toroidal directions are required for the antenna with high reliability. Mechanical and structural design works of the launcher (antenna and its support with steering structure) based on a linear motion antenna concept are in progress. The key component is a long-stroke bellows which enables to alter poloidal injection angle and a bellows which enables to alter toroidal injection angle. Using a newly fabricated mock-up of the steering structure, it was confirmed that the antenna was mechanically realized for poloidal and toroidal injection angle ranges of -10 to +45
and -15 to +15, respectively. Those angles are consistent with angles required in JT-60SA. The results of thermal and structural analyses are also presented.
Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Sato, Fumiaki; et al.
Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10
Times Cited Count：19 Percentile：62.41(Physics, Fluids & Plasmas)A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.
Kobayashi, Takayuki; Moriyama, Shinichi; Isayama, Akihiko; Hoshino, Katsumichi; Sakamoto, Keishi; Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Kasugai, Atsushi
Denki Gakkai Kenkyukai Shiryo, Genshiryoku Kenkyukai (NE-11-6), p.11 - 15, 2011/09
The developments of radio frequency systems for plasma heating and current drive have been continued for magnetically-confined fusion devices, such as JT-60SA, ITER. The specifications of the systems are shown. Recent progress in the electron cyclotron range of frequency system developments, especially for the JT-60SA, is summarized.
states in 
Gd populated by the 
decay of EuNagae, Daisuke*; Ishii, Tetsuro; Takahashi, Ryuta*; Asai, Masato; Makii, Hiroyuki; Osa, Akihiko; Sato, Tetsuya; Ichikawa, Shinichi; Shimizu, Yoshifumi*; Shoji, Takuya*
AIP Conference Proceedings 1224, p.156 - 160, 2010/04
Times Cited Count：2 Percentile：64.17(Physics, Nuclear)Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Nuclear Fusion, 49(8), p.085001_1 - 085001_7, 2009/07
Times Cited Count：21 Percentile：61.72(Physics, Fluids & Plasmas)In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 
1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
Moriyama, Shinichi; Ikeda, Yoshitaka; Seki, Masami; Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken*; Isayama, Akihiko; Suzuki, Takahiro; Fukuda, Takeshi*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 79(9), p.935 - 944, 2003/09
An optimization of current profile is a key issue for attaining higher plasma performance in Tokamak, such as stabilization of neo-classical tearing mode (NTM) and control of internal transport barrier (ITB). In JT-60U, a high power electron cyclotron heating (ECH) system at 110 GHz has been developed for local plasma heating and current drive. We have demonstrated the technical feasibility of the antenna which can scan EC beam in both toroidal and poloidal directions. The toroidal scan enabled co- and counter- current drive and also pure plasma heating. An automatic stabilization of the NTM was demonstrated by means of current drive at the location of magnetic island using a feedback control of poloidal beam angle. The total injected power has been extended to 2.8 MW for 3.6 sec and each gyrotron delivers ~ 1 MW for 5 sec. This world record of the injection energy was attained by an upgrade of the gyrotron using RF absorber in the beam tunnel to suppress the parasitic oscillation and improvement of the transmission efficiency of the waveguide system.
Ikeda, Yoshitaka; Ide, Shunsuke; Suzuki, Takahiro; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken; Isayama, Akihiko; Oikawa, Toshihiro; Hamamatsu, Kiyotaka; Kamada, Yutaka; et al.
Nuclear Fusion, 42(4), p.375 - 382, 2002/04
Times Cited Count：28 Percentile：65.15(Physics, Fluids & Plasmas)no abstracts in English
H-mode discharges in JT-60UIsayama, Akihiko; Kamada, Yutaka; Ozeki, Takahisa; Ide, Shunsuke; Fujita, Takaaki; Oikawa, Toshihiro; Suzuki, Takahiro; Neyatani, Yuzuru; Isei, Nobuaki; Hamamatsu, Kiyotaka; et al.
Nuclear Fusion, 41(6), p.761 - 768, 2001/06
Times Cited Count：50 Percentile：80.13(Physics, Fluids & Plasmas)no abstracts in English
Isayama, Akihiko; Isei, Nobuaki; Ishida, Shinichi; Sato, Masayasu; Kamada, Yutaka; Ide, Shunsuke; Ikeda, Yoshitaka; Takahashi, Koji; Kajiwara, Ken; Hamamatsu, Kiyotaka; et al.
Fusion Engineering and Design, 53(1-4), p.129 - 135, 2001/01
Times Cited Count：12 Percentile：64.73(Nuclear Science & Technology)no abstracts in English
Takahashi, Koji; Kajiwara, Ken; Kasugai, Atsushi; Isayama, Akihiko; Ikeda, Yoshitaka; Ide, Shunsuke; Sakamoto, Keishi; Imai, Tsuyoshi; Fujii, Tsuneyuki
Fusion Engineering and Design, 53(1-4), p.511 - 516, 2001/01
Times Cited Count：18 Percentile：76.49(Nuclear Science & Technology)no abstracts in English
Ikeda, Yoshitaka; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken; Isayama, Akihiko; Ide, Shunsuke; Terakado, Masayuki; Shinozaki, Shinichi; Yokokura, Kenji; Anno, Katsuto; et al.
Fusion Engineering and Design, 53(1-4), p.351 - 363, 2001/01
Times Cited Count：40 Percentile：92.11(Nuclear Science & Technology)no abstracts in English
Isayama, Akihiko; Ikeda, Yoshitaka; Ide, Toshiyuki; Suzuki, Takahiro; Moriyama, Shinichi; Takahashi, Koji; Kajiwara, Ken; Oikawa, Toshihiro; Hamamatsu, Kiyotaka; Kamada, Yutaka; et al.
AIP Conference Proceedings 595, p.267 - 274, 2001/00
no abstracts in English
H-mode discharges in JT-60UIsayama, Akihiko; Kamada, Yutaka; Ozeki, Takahisa; Ide, Shunsuke; Fujita, Takaaki; Oikawa, Toshihiro; Suzuki, Takahiro; Neyatani, Yuzuru; Isei, Nobuaki; Hamamatsu, Kiyotaka; et al.
IAEA-CN-77/EXP3/03 (CD-ROM), 5 Pages, 2000/00
no abstracts in English
Ikeda, Yoshitaka; Fujita, Takaaki; Hamamatsu, Kiyotaka; Ide, Shunsuke; Imai, Tsuyoshi; Isayama, Akihiko; Iwase, Makoto; Kasugai, Atsushi; Kondoh, Takashi; Kusama, Yoshinori; et al.
AIP Conference Proceedings 485, p.279 - 287, 1999/09
no abstracts in English
U at 13.9MeV excitationYokoyama, Akihiko*; *; *; *; *; *; *; Takamiya, Koichi*; Shinohara, Nobuo; Tsukada, Kazuaki; et al.
Z. Phys., A, 356(1), p.55 - 60, 1996/00
no abstracts in English
