Development of high power gyrotron for ITER application

Recent progress on the development of a high power 170 GHz gyrotron obtained in Japan Atomic Energy Agency (JAEA) is presented. Firstly, the repetitive operation of 800 kW/600 s with an interval of 20-30 min was performed. The electrical efficiency was 52-57% with the depressed collector. The 72 shots of 88 shots was very stable 600 s oscillation. No damage was found on the gyrotron by this test. Secondly, 5 kHz-full power modulation was demonstrated at CW mode. For this purpose, a full beam current modulation was realized by switching the anode voltage to minimized the collector heat load. Thirdly, in the dual frequency gyrotron development, the 1.3 MW oscillations at 170 GHz and 136.8 GHz were successfully demonstrated by changing the cavity field and the anode voltage keeping other parameters constant.