High-voltage testing of a 500-kV dc photocathode electron gun

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

A high-voltage dc photocathode electron gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 hours was demonstrated at an acceleration voltage of 500 kV. The dc photocathode electron gun is designed for future light sources based on energy-recovery linac and consists of a Cockcroft-Walton generator, a segmented cylindrical ceramic insulator, guard-ring electrodes, a support-rod electrode, a vacuum chamber and a pressurized insulating gas tank. The segmented cylindrical ceramic insulator and the guard-ring electrodes were utilized to prevent any damage to the insulator from electrons emitted by the support-rod electrode.