Status of 500-kV DC gun at JAEA

Nishimori, Nobuyuki; Nagai, Ryoji; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*; Nakanishi, Tsutomu*; Okumi, Shoji*

We have developed a 500-kV DC gun at JAEA. It is difficult to apply DC high voltage on a ceramic insulator with a stem electrode because of field emission from the electrode. By employing a segmented insulator, we succeeded in applying 500-kV on the ceramics for eight hours without any discharge in Dec. 2009. In Jul. 2009, we reached 380-kV with electrodes in place before we suffered field emission problem from the cathode electrode. Then we generated beam at 300-kV in Nov. 2010. After beam generation we have continued high voltage testing with electrodes in place. In Jul. 2011, we reached 510-kV, before suffering another field emission problem from cathode electrodes. The problem may be attributed to small dust inside our gun chamber. We are trying to reach 550-kV by solving the small dust problem. Our current status of development will be presented in the workshop.