Full high-power modulation on a 170 GHz 1 MW ITER gyrotron with a triode magnetron injection gun
3極管型電子銃を用いた170GHz/1MW-ITER用ジャイロトロンによる高パワー完全変調
梶原 健; 坂本 慶司; 小田 靖久; 林 一生*; 高橋 幸司; 春日井 敦
Kajiwara, Ken; Sakamoto, Keishi; Oda, Yasuhisa; Hayashi, Kazuo*; Takahashi, Koji; Kasugai, Atsushi
A 5 kHz full power modulation experiment is demonstrated on a 170 GHz gyrotron. 5 kHz high power and beam on/off modulation is achieved by employing a fast short-circuited switch between the anode and the cathode of the triode type electron gun (single anode switch). Lower heat load on the cavity and the collector compared to CW operation realizes more than 1 MW oscillation with 1 MW designed gyrotron. The maximum achieved power is 1.16 MW with electrical efficiency of 48%. In the high efficiency operation, an unwanted mode oscillation is observed at the start-up phase of each pulse, which is induced by slow voltage rise time of the anode. For faster rise up of the anode voltage, another fast switch is inserted between an anode voltage divider and the anode electrode (double anode switch). In the experiment, it is shown that the successful fast start up of the anode voltage and the minimized unwanted mode generation.