DEVELOPMENT OF HIGH POWER LONG PULSE ITER GYROTRONS

Recent progress on the development of a high power 170 GHz gyrotron obtained in Japan Atomic Energy Agency (JAEA) is presented. Firstly, a repetitive operation of 800 kW/600 s with an interval of 20-30 min was performed. The electrical efficiency was 52-57 % with a depressed collector. The 72 shots of 88 shots was very stable 600 s oscillation. No damage was found on the gyrotron after the test. Secondly, 5 kHz-full power modulation was demonstrated with pulse duration of 60 s. For this purpose, a full beam current modulation was realized to minimize the collector heat load by adopting an anode voltage switching. Thirdly, in the dual frequency gyrotron development, the 1.3 MW oscillations at 170 GHz and 136.8 GHz were successfully demonstrated at short pulse operation by changing the cavity field and the anode voltage keeping other parameters constant.