直流-射频超导光阴极电子枪  

DC-SRF photocathode gun

作　　者：黄森林 刘克新[1,2] 赵夔[1,2] 陈佳洱[1,2] Senlin Huang;Kexin Liu;Kui Zhao;Jiaer Chen(State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871,China;Institute of Heavy lon Physics,School of Physics,Peking University Bejing 10871,China)

机构地区：[1]北京大学核物理与核技术国家重点实验室,北京100871 [2]北京大学物理学院重离子物理研究所,北京100871

出　　处：《科学通报》2023年第9期1036-1046,共11页Chinese Science Bulletin

基　　金：国家重点研发计划(2016YFA0401904,2017YFA0701000)资助。

摘　　要：直流-射频超导(direct current-superconducting radio frequency,DC-SRF)光阴极电子枪是由北京大学射频超导加速器实验室提出并发展的一种连续波电子源,可产生MHz及以上重复频率、皮秒至亚皮秒脉冲、Me V能量的电子束.作为一类重要的超导型光阴极电子枪,DC-SRF将具有高量子效率的半导体光阴极与射频超导加速腔分离,成功地解决了二者之间的兼容问题,并具有结构紧凑、暗电流低等优点.DC-SRF光阴极电子枪的研发经历了样机、DC-SRF-I及DC-SRF-II三个阶段,其中,DC-SRF-I于2014年实现稳定载束运行,并开展了系列应用实验;DCSRF-II于2021年建成,2022年实现100 p C束团电荷量、1 MHz重复频率的连续波模式运行,暗电流小于1 pA,归一化发射度达到亚mm-mrad级,综合性能指标处于领先地位.本文总结DC-SRF电子枪的研究工作,主要内容包括DCSRF-I电子枪、DC-SRF-II电子枪、光阴极与驱动激光等.The DC-SRF photocathode gun,an important member of superconducting radio-frequency(SRF)guns,is a distinguished compact mega-electron-volt(MeV)electron source capable of generating picosecond to sub-picosecond electron pulses at megahertz(MHz)and higher repetition rate.The concept of DC-SRF was conceived by the SRF Accelerator Laboratory of Peking University in 2001,which combines a DC gap and a 1.3 gigahertz(GHz)SRF cavity connected by a short drift tube around 10 mm long.By introducing the DC gap,the semiconductor photocathode is moved out from the SRF cavity,which successfully solves the compatibility problem between the photocathode and the SRF cavity as validated by later experiments.Besides,the high vacuum in the cryogenic DC structure allows the usage of green laser photocathodes,which benefits the generation of high repetition rate,high average current electron beams.The development of the DC-SRF photocathode gun has so far undergone three stages:The prototype,DC-SRF-I,and DC-SRF-II.The feasibility of the DCSRF concept was first tested in 2004 with the prototype employing a 1.5-cell SRF cavity and operated at pulsed mode under 4.2-4.4 K.In the following decade,the first-generation DC-SRF gun,DC-SRF-I,was developed with the purpose to deliver electron beams for research on infrared(IR)FEL,energy recovery linac,terahertz(THz)radiation,etc,and for a higher energy gain,it employed a 3.5-cell SRF cavity.The DC-SRF-I gun was brought into stable operation in 2014 with a DC voltage of 45-50 kV,an SRF cavity gradient of 7-9 MV/m(corresponding to an energy gain around 3 MeV),and a dark current evaluated to be lower than 1 nA.It is the first SRF gun that can operate steadily with semiconductor photocathodes.The MHz repetition rate electron beam from the DC-SRF-I gun had been used for applications including high repetition rate superradiant THz undulator radiation,ultrafast electron diffraction,etc.In 2015,the electron beam was injected into a 2×9-cell SRF linac and the energy was boosted to 10-20 MeV.Until DC-SRF-I'

关 键 词：连续波电子源 光阴极电子枪 高重复频率电子束 直流-射频超导电子枪 半导体光阴极 光阴极驱动激光 

分 类 号：TL53[核科学技术—核技术及应用]