电子束团纵向长度是束流诊断中的重要参数,电光频谱解码法(Electro-Optical Spectral Decoding,EOSD)是为数不多的可进行单发测量的高时间分辨率测量方法.本文基于上海深紫外自由电子激光装置(Shanghai Deep Ultraviolet Free Electron Laser,SDUV-FEL)设计了一套电光频谱解码法测量束团长度实验方案.通过采用针尖粗同步和可调的光栅展宽器可实现长度在1?10 ps内变化的束团无损测量.通过对电光调制过程及其后探测的仿真研究表明,选用0.5 mm厚的ZnTe晶体在距离束流中心3?5 mm处测量时,时间分辨率最高可达180fs(Root Mean Square,RMS),信号展宽在3%以内,测量的电场形状无可观测畸变,满足SDUV-FEL的实验需求.%Background:The longitudinal length of electron bunch is an important parameter in beam diagnostics. Electro-Optical Spectral Decoding (EOSD) is one of the few powerful approaches to accurately measure bunches down to sub-picosecond level.Purpose:This study aims to design and evaluate a complete system to measure the bunch length at Shanghai Deep Ultraviolet Free Electron Laser (SDUV-FEL).Methods:The EOSD with a probe used for coarse synchronization and a tunable grating pair used as laser stretcher was designed, and the processes of Electro-Optical modulation and detection were simulated in detail.Results:The bunch length varying from 1 ps to 10ps can be measured without beam destruction in the whole process. The time resolution (Root Mean Square, RMS) is expected up to 180 fs at best and signal broadening within 3%.Conclusion: The longitudinal bunch length can be measured with high quality utilizing our EOSD setup. The system can meet the demands of SDUV-FEL.
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