根据光阴极直流高压电子枪超高真空和高电压工作特点, 采取技术措施, 金属腔体采用大通径、短管设计, 利用非蒸散型吸气剂(NEG)泵的抽气, 封闭储气空间预置排气通道, 电极系统增加中间电极, 降低系统峰值场强, 采用均压环非均匀分布, 在绝缘子内表面获得更加均匀的场分布。结果表明, 腔体真空度已小于5×10-9 Pa, 电压可升至300 kV。

A key technology issue of high-average-power free-electron laser (FEL) is the demonstration of stable, reliable, high-brightness, high-power electron source operation. The photocathode DC high voltage electron gun requires extreme-height-vacuum and more than 250 kV operating voltage. The vacuum vessel is a high conductance design, and the pump ability of NEG’s can act well. To realize high voltage operating stability, the electrode system introduces a middle-potential electrode and the electric field strength can be depressed to 70 percent on the cathode support tube surface. Based on the design thoughts, the vacuum has been up to less than 5×10-9 Pa and the operating voltage reaches 300 kV without abnormity. In this report, we concentrate on the description of considerations for engineering design and some details of the photo-DC-Gun that have been proven fitting in practice.