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Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08
Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.
Yokokura, Kenji; Hiranai, Shinichi; Shibayama, Minoru*; Ikeda, Yoshitaka; Moriyama, Shinichi; Shinozaki, Shinichi; Sato, Fumiaki*; Kasugai, Atsushi
JAERI-Tech 2003-047, 58 Pages, 2003/06
JAERI-Tech-2003-047.pdf:9.52MB
This report represents a MW-class RF transmission system at 110 GHz in JT-60U electron cyclotron heating system. Its basic design, performances, features, construction experiences, and improvements fed-back from the operation experiences are described. The transmission system has successfully demonstrated high power long pulse operation, e.g., 1MW for 4s with 20 
25% of low transmission loss which agrees with the designed value.
Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sato, Fumiaki; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; Wada, Kenji; Shimono, Mitsugu; et al.
no journal, ,
It is recognized that stabilization of neoclassical tearing mode (NTM) instabilities using power modulated electron cyclotron current drive (ECCD) is effective. Although a modulation frequency of around 5 kHz was required to NTM suppression experiments in JT-60U, the achieved frequency had been limited to 3 kHz due to the slow response time of the high voltage circuit and over-current during charging/discharging. In this study, the anode voltage divider of the system was improved and the capacitance and resistance in the high voltage circuit was optimized resulting in the modulation frequency of over 5 kHz. The robust modulated operation region was also studied with suppressing undesired mode. Moreover, the real-time synchronizing system was developed to control the phase and duty ratio of the modulated ECCD synchronizing with the NTM frequency which varies during ECCD with plasma rotation, and modulated ECCD experiments with NTM suppression was carried out in JT-60U.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
The electron cyclotron range of frequency (ECRF) system (3 MW 
5s at 110 GHz with 4 gyrotrons) of JT-60U will be upgrade to the system having 9 gyrotrons (7 MW 100s) for JT-60SA (super advanced). As heat removal from the mirrors is essential for a long pulse antenna, a new concept with a mirror driven in the linear motion which eliminates the flexible tube for coolant supply is under development. The design study featuring beam profile calculation showed feasibility of the antenna in the 0.48 m 0.48 m port. The low power rf test with simple mockup antenna has just been begun. Aging of the gyrotron with improved mode converter was started in the end of 2008, aiming at 1 MW, 100s oscillation. Because the current capacity of the present high voltage power supply is not enough to realize 100s oscillation, LHRF power supply having twice larger current capacity is connected to the gyrotron in March 2009. The gyrotron aging will be started soon again.
Isayama, Akihiko; Kobayashi, Takayuki; Moriyama, Shinichi; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
no abstracts in English
Kobayashi, Takayuki; Isayama, Akihiko; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Sato, Fumiaki; Wada, Kenji; Shibayama, Minoru; Yokokura, Kenji; Moriyama, Shinichi
no journal, ,
no abstracts in English
Isayama, Akihiko; Kobayashi, Takayuki; Moriyama, Shinichi; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
no abstracts in English
Moriyama, Shinichi; Isayama, Akihiko; Kobayashi, Takayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Hasegawa, Koichi; Shimono, Mitsugu; Yokokura, Kenji; et al.
no journal, ,
no abstracts in English
Wada, Kenji; Kobayashi, Takayuki; Isayama, Akihiko; Hasegawa, Koichi; Sato, Fumiaki; Yokokura, Kenji; Suzuki, Sadaaki; Shibayama, Minoru; Hiranai, Shinichi; Shimono, Mitsugu; et al.
no journal, ,
no abstracts in English
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
Full specification of 4 MW for 5s was achieved by simultaneous operation of 4 gyrotrons, and 3 MW was injected to the JT-60U plasma by the completion of experiments in August 2008. In the inspection of the antenna after the operation, there were no large damages but the color of the mirror surfaces were slightly changed and some evidences of arcing were found. In the statistical analysis of operation, the rate of successful shots to the plasma was higher than 85% in the last 3 years. Development of long-pulse gyrotron with improved mode converter is on going and the conditioning was started in the end of 2008 aiming at 1 MW, 100s for JT-60SA. It was confirmed that the diffraction loss was remarkably decreased and the pulse length reached 1 MW 17s so far. A new operation technique of active anode voltage control was developed to obtain high efficiency, and the pulse length for 1.5 MW oscillation was extended from 1s to 4s.