磁透镜内径比对条纹变像管性能的影响

Influence of Magnetic Solenoid Lens on Characteristics of Streak Image Tube

针对一款高时空分辨率飞秒条纹变像管的带极靴磁透镜结构,提出了更加符合实际磁场分布规律的"高斯型"磁场分析模型,并且研究了磁透镜内径比对条纹变像管时间、空间分辨特性的影响。利用Lorentz软件数值研究了条纹变像管中不同内径比的磁透镜所产生的磁场分布,并且采用Monte-Carlo方法对大量光电子初始参量进行抽样计算,通过跟踪行波偏转前置短磁聚焦条纹变像管中大量光电子的运行轨迹,统计分析了光电子在最佳像面上的位置分布,最后利用调制传递函数对条纹管时空分辨能力进行评价。结果表明:当磁透镜内径比r1/r2=0.83时,磁场对电子束进行有效聚焦,获得物理时间分辨率优于190 fs,且狭缝边缘(狭缝总长度为6 mm)空间分辨率达到100 lp/mm的结果。

The magnetic field in the pole piece magnetic lens of a new type of femto-second （fs） streak image tube with both high temporal and spatial resolution was re-modeled to improve the precision. The influence of the magnetic solenoid lens on the magnetic field distribution and on the temporal and spatial resolution characteristics of the streak im- age tube was investigated. The magnetic field distributions, generated by the magnetic lens with different radius ratios, were simulated with Lorentz software; and the emission and trajectories of up to 3000 photoelectrons were sampled and calculated in Monte Carlo method with software CST PARTICLE STUDIO to statistically evaluate the temporal and spatial resolution of the image tube with the modulation transfer function. The simulated results show that the Gaussian model out- performs the bell-shaped model when it comes to description of the realistic magnetic field, and that the magnetic lens with a radius ratio of 0.83 most effectively focuses the electron beam with a temporal resolution of 190 fs and a spatial resolution over 100 lp/mm.