Development of semiconductor switches for high-power crowbar circuits for J-PARC accelerator

Ono, Ayato; Takayanagi, Tomohiro   ; Fuwa, Yasuhiro   ; Shinozaki, Shinichi ; Ueno, Tomoaki*; Horino, Koki*; Sugita, Moe ; Yamamoto, Kazami   ; Kinsho, Michikazu  ; Ikoma, Naoya*; Tokuchi, Akira*

In J-PARC, an ignitron is used for the crowbar device of the klystron power supply to excite the RF acceleration voltage in a Linac cavity. Mercury, that is used in the ignitron, would be prohibition of use in the future due to environmental protection. Therefore, we designed a semiconductor crowbar switch for short-circuit protection of klystron using a MOS gate thyristor. We have manufactured an oval-type board module that realizes an operating output of 3kV, 40kA, and 50us per board. Because a high voltage of 120 kV is applied on each board, we adopted a self-power supply method to supply a electricity for the control system. This method can create the electricity from a high-voltage DCDC converter. We confirmed the operating performance on a 1/2 scale (60 kV, 40 kA) of the voltage in the existing ignitron system (120 kV, 40 kA). We also studied a test circuit in a higher voltage range of more than 90 kV. Our latest result is well promising for an alternative system of ignitron.