成像法在电磁叠加型光阴极注入器中的应用  

Application of imaging method in overlapping field type photoinjector

作　　者：范培亮 王科[1] 何小中[1] 杨柳[1] 魏涛[1] 江孝国[1] 杨治勇[1] 杨兴林[1] Fan Peiliang;Wang Ke;He Xiaozhong;Yang Liu;Wei Tao;Jiang Xiaoguo;Yang Zhiyong;Yang Xinglin(Institute of Fluid Physics,CAEP,Mianyang 621900,China)

机构地区：[1]中国工程物理研究院流体物理研究所,四川绵阳621900

出　　处：《强激光与粒子束》2022年第10期150-155,共6页High Power Laser and Particle Beams

基　　金：国家自然科学基金项目(11805191,12035012,11875242)。

摘　　要：光阴极注入器为X射线自由电子激光提供高品质电子束团,其中,阴极面上电子发射的均匀性在很大程度上影响着电子束团的束流品质,实验中常通过测量光阴极量子效率分布来评估电子发射的均匀性。成像法测量光阴极量子效率分布时具有实时、高分辨的特点,目前,此方法只在电磁分离型光阴极注入器中有所应用。探索成像法在电磁叠加型光阴极注入器中应用的可行性,采用理论分析结合数值模拟的方法,研究结果显示成像法适用于电磁叠加型光阴极注入器,且由此获得的量子效率分布具有阴极面中心位置处分辨率优于外层的特点。此外,针对成像法在初始束团横向动量分布测量中的应用进行模拟计算分析,并在此基础上提出一种判断阴极面剩余磁场是否为零的方法。The photoinjectors are promising high quality electron sources for X-ray free electron laser(XFEL).The uniformity of the electron emission from the photocathode has big influence on the electron beam quality.Usually, the quantum efficiency(QE) mapping is used to evaluate the uniformity in experiments. The QE mapping imaging method used to measure the QE mapping has high resolution and it can be used in real-time measurement, so far it is only used in separated type photoinjectors. In our photoinjector, the electric field and magnetic field are overlapping in the cathode vicinity, according to theoretical analysis and simulations, we analyze the application of this method in overlapping field. Finally, we demonstrate that the imaging method is suitable for this overlapping field,and the results show that the QE mapping has higher resolution in the center of the photocathode than the outer part.We also analyze the imaging method used to measure the transverse momentum distribution, and one way is proposed to judge whether the rest magnetic field on the cathode is zero or not.

关 键 词：量子效率 成像法 叠加场 注入器 

分 类 号：O59[理学—应用物理]