Development on ECRF system for JT-60SA

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Hoshino, Katsumichi; Shimono, Mitsugu; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Hinata, Jun; Sato, Yoshikatsu

Development and design of ECRF system are being carried on toward JT-60SA. In spite of the huge earthquake on March 11th, damage on the system was small, and we restart the gyrotron operation after 2 months of careful inspection and test. The diffraction loss in the gyrotron was kept low and the temperature of the DC break cooling water, which limited the pulse length, was saturated at about half of that before the improvement of the mode convertor. The pulse length reached 31 s at 1 MW and 99 s at 0.3 MW. In JT-60SA, ECRF of about 130-140 GHz would make possible central heating/current drive at BT = 2.25 T. From this point of view, development of dual frequency gyrotron was started. In calculation, oscillation conditions with efficiency of 0.4 were obtained for TE22,8 mode (110 GHz) and TE27,10 mode (137.6 GHz). Fabrication of the gyrotron has just been started. The high power test will be started in the next fiscal year.