低发射度L波段光阴极微波电子枪物理设计-中国科学院上海应用物理.PDF

第39 卷 第9 期 核 技 术 Vol.39, No.9 2016 年9 月 NUCLEAR TECHNIQUES September 2016 低发射度L 波段光阴极微波电子枪物理设计 李成龙 汤振兴 裴元吉 （中国科学技术大学国家同步辐射实验室 合肥 230022 ） 摘要 太赫兹(THz)光源对电子束的能量、能散及发射度有极高要求，研发高性能电子源是基于自由电子激光 (Free Electron Laser, FEL)的THz 光源的重要挑战。对电子腔中束团发射度增长机制的研究，有助于设计针对 有效的发射度补偿方案。本文首先描述了L 波段光阴极微波电子枪腔的设计，利用POISSON Superfish 软件给 出了腔内电磁场分布，详细分析了束流发射度增长的因素，讨论发射度补偿原理。由此提出基于主副螺线管 线圈抑制发射度增长的补偿方案，并用ASTRA 程序对补偿效果进行模拟计算。结果表明，采用该补偿方案后， 电子腔输出束团的能散和发射度有显著改善，达到THz 光源对于电子源的要求。 关键词 高性能电子束源，光阴极微波电子枪，发射度，补偿线圈，空间电荷力，能散 中图分类号 TL503.5 DOI: 10.11889/j.0253-3219.2016.hjs.39.090203 Physical design of low-emittance L-band photocathode microwave electron gun LI Chenglong TANG Zhenxing PEI Yuanji (National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230022, China) Abstract Background: The development of high performance electron beam source has been a challenge for Free-electron Laser (FEL) based THz source which is critical for the energy, energy spread and emittance of the electron beam. Purpose: This work aims to find out the mechanism of emittance growth and developing a compensation technique for this emittance growth in the Radio Frequency (RF) gun cavity. Methods: First of all, a RF gun cavity is designed using POISSON Superfish to calculate its electro-magnetic field distribution for analysis of the emittance growth mechanism. Then, a compensation scheme is developed by employing a pair of solenoids to reduce the space charge emittance.