基于相干渡越辐射的束团长度测量研究

电子束团长度是束流诊断中的重要参数,基于相干渡越辐射(Coherent Transition Radiation,CTR)的测量方法是一种简单易行的高时间分辨率测量方法。本文调研并分析了不同电子束团长度测量方法的优缺点,选择基于CTR方法作为主要研究方向,主要针对上海深紫外自由电子激光实验装置(Shanghai Deep Ultra-Violet Free Electron Laser,SDUV-FEL)和X射线自由电子激光试验装置(Shanghai X-ray Free Electron Laser,SXFEL)进行了实验方案设计和模拟分析。结果表明,通过合理的参数选择和方案优化,用该方法可对飞秒至皮秒范围内的束团长度进行测量,时间分辨率能到达飞秒量级,满足SDUV-FEL的实验需求和SXFEL的工程需求。

Measurement study of electron bunch length based on the coherent transition radiation

Background:Longitudinal electron bunch length is an important parameter in accelerator beam diagnostics.It plays a significant role in single-pass free electron lasers,since the high-gain Free Electron Laser (FEL) process depends strongly on a high peak current of the electron bunches.Purpose:It is necessary to measure the electron bunch lengths in both Shanghai Deep Ultra-Violet Free Electron Laser (SDUV-FEL) and Shanghai X-ray Free Electron Laser (SXFEL).Methods:In this paper,the advantages and disadvantages of three standard diagnostic tools for bunch length measurement are compared and a measuring system based on coherent transition radiation (CTR) for SDUV-FEL and SXFEL is designed and analyzed.Results:The simulation shows that the measuring system can measure the electron bunch length from 20 fs to 1 ps effectively and time resolution of the measuring system can reach 20 fs.Conclusion:Electron bunch length measurement by means of CTR is an easy way to achieve high time resolution with inexpensive experimental instruments.The measuring system meets the demands of SDUV-FEL and SXFEL well.