电子枪束源部件结构尺寸对束流品质影响的CST仿真

在直热式电子枪中,电子枪束源部件结构尺寸的改变会改变静电场对电子束的初次汇聚,从而影响束流品质。针对电子枪中静电场以及电子运动轨迹难以用常规方法直接测量的问题,通过建立1∶1三维模型,并利用CST电磁仿真粒子工作室对整个束流产生过程进行模拟。利用控制单一变量的方法,结合模拟所得数据,得到了在不同条件下,静电场分布、电子的运动轨迹以及各个变量与最终焦点处束流电流密度关系曲线,最终得到了束流品质最优的束源部件结构尺寸。用优化了阴阳极结构及阴阳极距离后的电子枪在铝合金板材上进行实际焊接试验,所得焊缝形貌优于原有电子枪焊接所得焊缝,证明了模拟结果的正确性。此种模拟方法为改善现有电子枪束流品质以及未来电子枪设计提供了参考依据。

CST Simulation on Effect of Beam Source Component Struture size on Beam Quality in Electron Guns

There will be an electrostatic field between cathode grid and anode in directly heated electron guns.This electrostatic field has a primary convergence effect on the beam current.The change of distance between anode and cathode,and the change of grid and anode shape will affect this electrostatic field and ultimately affect beam quality.Aiming at the problem that the electrostatic field and the movement track of electron are both difficult to measure directly by conventional method,this paper built a 1 ∶ 1 3D model and simulated the whole process of beam generation by using the simulation software CST particlestudio.By using the single variable method and analyzing the date,we obtain electrostatic field distribution,clear electron movement track under different conditions and graph of each variable parameter and beam current energy density at the focus position.Finally,the best structure size for beam quality is obtained.Then we took actual welding test on aluminum alloy plate with optimized electron gun structure.The welding seams we got are better than the original electron gun structure,which proves the simulation result is correct.This method provides a basis for the improvement of the beam quality of the existing electron guns and future design of the electron guns.