DC-SC光阴极注入器的束载实验的调试进展

 北京大学射频超导实验室设计了新型超导光电子枪——DC-SC光阴极注入器，目标是为自由电子激光平台提供能量在2~3MeV，脉宽小于10ps，脉冲重复频率为81.25MHz，平均流强约为1mA的低发射度电子束。现在已经建成了DC-SC光阴极注入器实验平台，包括激光驱动光阴极系统，Pierce直流高压加速结构，1.3GHz 1＋1/2纯铌超导腔，恒温器低温系统，4.5kW连续波微波系统，1/16分频与同步控制系统，束流诊断系统和能量分析系统等。并且完成了超导腔的静态实验，直流加速结构也经过了100μA低电流测试。实验结果符合设计要求，整体调试后即可以进行束载实验。

Process of DC-SC photoinjector

The DC-SC photoinjector at Peking University is designed to provide an electron beam of average current 1mA with the energy of 2～3MeV and normalized rms transverse emittance of 3πmm-mrad at an 81.25MHz repetition rate. The test facility has been completely installed in our lab. In this paper some of the ongoing experimental activities are summarized. First results from the cold test of superconducting cavity have been presented. According the results, we have improved the main coupler to repress the multipacting. The beam test of 100μA on the DC gun has been done, photocathode preparation chamber can produce Cs_2Te cathodes (5%@266nm), and the laser system can provide laser pulse with 266nm wavelength. The time synchronization between laser and RF power has been achieved by a timing stabilizer. A new method using "due image pattern" of Cherenkov radiation will be commissioned to measure beam emittance. The next step is under way, to prepare all the equipment for the beam tests.