BEPCII电子枪系统设计

 BEPCII改进工程需要更高流强的电子枪。新电子枪系统的物理设计、机械设计、控制系统设计等均进行了描述。电子枪的设计发射电流在脉宽为1 ns时大于10 A，重复频率50 Hz。将会采用脉冲电源来为电子枪提供最高200 kV的脉冲高压。在设计阶段，电子枪的几何结构和束流传输过程利用计算机模拟进行了优化。EGUN和DGUN的计算结果表明导流系数为0.22 mA·V^-3/2，电子枪出口的发射度为16 p·mm·mrad。PARMELA的模拟结果表明束流能顺利地传输至第一根加速管末端，捕获效率为67%，出口的均方根发射度为25 mm·mrad。基于EPICS平台的电子枪控制系统设计也已完成，提供了全新的双脉冲运行模式和2.5 μs长脉冲运行模式。

Design of the BEPCII electron gun system

BEPCII upgrading project needs a new high current electron gun. The design stage such as physical design, mechanical design and control system design of this new electron gun is described. The emission current is designed to be higher than 10 A for the pulse width of 1 ns with repetition rate of 50 Hz. The gun will operate with a pulsed high voltage power supply which can provide up to 200 kV high voltage. Computer simulations and optimizations have been carried out in the design stage, including the gun geometry and beam transport. EGUN and DGUN codes are used to simulate the gun geometry, and the results show that the perveance is about 0.22 μA·V-3/2,and the emittance at gun exit is about 16 π·mm·mrad. PARMELA code shows that the electron beam can be easily transported to the end of the first accelerating tube with a capture efficiency of 67% and root mean square emittance of 25 mm·mrad. New scheme of the gun control system based on EPICS is also presented. Twobunch operation mode and 2.5 μs long pulse operation mode are available in the control system.