高压直流连续波光阴极注入器中电子束流发射度研究

 高平均功率自由电子激光研究中，电子束质量是关键。针对高平均功率自由电子激光目标参数，提出了直流高压连续波光阴极注入器，给出了注入器的束流动力学过程。为了降低输出束流横向发射度，采用特殊结构设计的静电加速腔，加速电压1MV，最大加速梯度10MV/m。用PARMELA程序进行了粒子动力学模拟，电子束束团电荷为0.5nC，束团长度10ps时，注入器输出束流归一化发射度均方根值为5.8mm·mrad。     

高压直流连续波光阴极注入器中电子束流发射度研究

高平均功率自由电子激光研究中,电子束质量是关键。针对高平均功率自由电子激光目标参数,提出了直流高压连续波光阴极注入器,给出了注入器的束流动力学过程。为了降低输出束流横向发射度,采用特殊结构设计的静电加速腔,加速电压1MV,最大加速梯度10MV/m。用PARMELA程序进行了粒子动力学模拟,电子束束团电荷为0.5nC,束团长度10ps时,注入器输出束流归一化发射度均方根值为5.8mm·mrad。     

射频腔光阴极注入器发射度研究

 在激光驱动的光阴极注入器产生的高亮度电子束中，空间电荷引起发射度的增长。分析了射频腔中引起发射度增长的因素以及解决这个问题的办法——在射频腔的阴极附近加一个螺旋聚焦磁场进行补偿，也给出了补偿后电子束的发射度并和数值模拟结果进行比较，实验测试表明，所得结果比较符合。     

射频腔光阴极注入器发射度研究

在激光驱动的光阴极注入器产生的高亮度电子束中,空间电荷引起发射度的增长。分析了射频腔中引起发射度增长的因素以及解决这个问题的办法——在射频腔的阴极附近加一个螺旋聚焦磁场进行补偿,也给出了补偿后电子束的发射度并和数值模拟结果进行比较,实验测试表明,所得结果比较符合。     

光阴极RF腔注入器束流发射度研究

分析了光阴极RF腔注入器中的RF场效应和空间电荷效应,给出了电子在加速腔中束流发射度的解析表达式,它说明在加速过程中束流发射度是振荡变化的。利用SUPERFISH和GPT程序模拟计算了光阴极1+1/2腔注入器输出束流发射度与加速场强、注入相位、束团大小和形状、束团电荷的关系。适当选择这些条件,可以获得横向发射度小于2πmm·mrad 的输出束流。     

光阴极RF腔注入器束流发射度研究

 分析了光阴极RF腔注入器中的RF场效应和空间电荷效应，给出了电子在加速腔中束流发射度的解析表达式，它说明在加速过程中束流发射度是振荡变化的。利用SUPERFISH和GPT程序模拟计算了光阴极1+1/2腔注入器输出束流发射度与加速场强、注入相位、束团大小和形状、束团电荷的关系。适当选择这些条件，可以获得横向发射度小于2πmm·mrad 的输出束流。     

连续波光阴极注入器的驱动激光器研究

 在连续波光阴极注入器的研究中,驱动激光器是一个关键技术,采用连续锁模振荡器的锁模输出作为种子源,用二极管连续泵浦放大,再连续倍频,可以产生符合注入器要求的激光脉冲列作为驱动激光。     

连续波光阴极注入器的驱动激光器研究

在连续波光阴极注入器的研究中,驱动激光器是一个关键技术,采用连续锁模振荡器的锁模输出作为种子源,用二极管连续泵浦放大,再连续倍频,可以产生符合注入器要求的激光脉冲列作为驱动激光。     

RF腔光阴极注入器中热发射度的测量研究

论文介绍RF腔光阴极注入器中热发射度的测量方法，在注入器中有三个因素影响热发射度的测量，它们是：射频场效应、空间电荷效应和发射度测量误差. 在注入器出口处，电子束发射度由：热发射度、射频场效应引起的发射度增长和空间电荷效应的发射度增长三部分组成. 论文从注入器中发射度增长理论和模拟出发，给出了一个能够消除射频场效应和空间电荷效应的热发射度测量方法.     

光阴极微波电子枪中发射度补偿及模拟计算

介绍了上海深紫外自由电子激光用光阴极微波电子枪采用发射度补偿技术的结果 .详细分析了线性空间电荷力的特点及对束流发射度的影响 ,从束流动力学和相空间两方面讨论了发射度补偿原理 .给出了补偿线圈的设计结构及其轴向场分布 .利用PARMELA程序对补偿效果作了模拟计算 .结果表明 ,设计的腔体对单圈 1 .5nC束团 ,在枪出口后 1 .2m处 ,电子能量为 5 .7MeV ,横向归一化发射度εn ,RMS=1 .61 2πmm·mrad. The emittance compensation technology will be used on the photo cathode RF gun for Shanghai SDUV FEL. In this paper, the space charge force and its effect on electron beam transverse emittance in RF gunis is studied, the principle of emittance compensation in phase space is discussed. We have designed a compensation solenoid and calulated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emi...     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source （LUCX） is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm·mrad to 3.66 πmm·mrad.     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough.A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform.In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance.With the uniform driving laser and the unbalanced RF gun,the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm.mrad.     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that ...     

Simulation study on the emittance compensation of off-axis emitted beam in RF photoinjector

To make full use of the photocathode material and improve its quantum efficiency lifetime, it can be necessary to operate the laser away from the cathode center in photoinjectors. In RF guns, the off-axis emitted beam will see a time-dependent RF effect, which would generate a significant growth in transverse emittance. It has been demonstrated that such an emittance growth can be almost completely compensated by orienting the beam on a proper orbit in the downstream RF cavities along the injector [1]. In this paper we analyze in detail the simulation techniques used in reference [1] and the issues associated with them. The optimization of photoinjector systems involving off-axis beams is a challenging problem. To solve this problem, one needs advanced simulation tools including both genetic algorithms and an efficient algorithm for 3D space charge. In this paper, we report on simulation studies where the two codes ASTRA and IMPACT-T are used jointly to overcome these challenges, in order to optimize a system designed to compensate for the emittance growth in a beam emitted off axis.