Recent progress in gyrotron development for JT-60SA

Kobayashi, Takayuki; Isayama, Akihiko; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Yokokura, Kenji; Hoshino, Katsumichi; Moriyama, Shinichi; Sakamoto, Keishi

Gyrotron developments for JT-60SA electron cyclotron range of frequency heating system have been carried out. A dual frequency gyrotron was developed for extending operation region of the system. A dual frequency gyrotron for 110 GHz and 138 GHz was designed and fabricated. Oscillations of 1 MW and 0.5 MW were obtained at 110 GHz and 138 GHz, respectively, for 0.1 s, so far. The oscillation efficiencies were consistent with the design. Experiments of a gyrotron equipping an improved mode convertor for reducing temperature increase of internal components due to stray radiation were also carried out toward long pulse operations of 100 s required in JT-60SA. Since an increase of waveguide temperature had been limited the pulse length, waveguide components with wider diameter, which is suitable for long pulse operation, were installed. An oscillation of 70 s at 1 MW, which is twice longer than the previous record, was obtained. A high power oscillation of 1.4 MW for 9 s was also obtained.