光阴极直流高压电子枪的极高真空系统

Design of Extreme High Vacuum System for Photocathode DC Electron Gun of Energy Recovery Linear Accelerator

设计了一套用于光阴极直流高压电子枪的极高真空系统。首先对电子枪真空腔室的钛阳极、阴极和高压陶瓷分别进行表面处理及烘烤除气后确定材料表面放气率,然后对真空室压强进行模拟计算并确定配泵方案,最后在现场组装、检漏后对真空系统进行调试。调试过程中为了保证不能被直接加热的内部阴极杆在烘烤时充分除气,使用ANSYS-Fluent软件的S2S辐射模型对烘烤过程进行模拟并确定烘烤温度与时间。经过真空调试,电子枪腔内真空度为5.6×10^(-10)Pa,满足其极高真空设计要求。

An extreme high vacuum（ XHV） system,dedicated to the photocathode DC electron gun for energy recovery linear accelerator,was designed,fabricated and tested. The vacuum chamber made of the titanium to minimize the outgassingrate and the ceramic insulators was fabricated with alumina. First,the total outgassing rate of the well-cleaned,fully-degassed surfaces of all titanium components and alumina insulators were measured and the pressure distribution in the vacuum chamber was experimentally simulated to optimize the pumping unit. Next,the temperature field in baking of the electron gun was formulated with S2S radiation model and simulated with ANSYSFluent to determine the safe baking conditions of the photocathode. Finally,the pressure of the electron gun,assembled,leak checked,baked and tested on site,was pumped down to 5. 6 × 10^-10 Pa,satisfying the stringent requirements of the DC electron gun with GaAs photocathode.