负氢离子源中多峰磁场形态数值模拟

Numerical simulation on multi-peak magnetic field configuration for negative hydrogen ion source

基于磁荷模型,在有限差分法基础上,推导了3维永磁体数值算法,结合全3维PIC/MCC粒子模拟算法,数值分析比较了外置型和"伞状"型两种特殊形态多峰磁场对电子能量沉积的影响。模拟结果表明:二者都能对粒子起到约束作用且能过滤引出负氢离子,同时二者电子能量分布规律基本一致,都呈现了双电子能态,符合等离子体放电基本机理;外置型过滤磁场对粒子的约束能力更强,能明显产生更多的粒子,总粒子数大约是"伞状"型过滤磁场情况下的4倍;"伞状"型过滤磁场能有效地抑制由磁场不均匀所引起的电子漂移,使产生的负氢离子空间分布更均匀。模拟结果与国外实验结果基本一致。

Based on the magnetic charge model,the numerical algorithm of three-dimensional permanent magnets was derived by the finite difference method.Then combining the full three-dimensional particle-in-cell/Monte Carlo algorithm（PIC/MCC）,two multi-peak magnetic field configurations,external magnetic filter and tent-shaped filter,were analyzed respectively,and their influences on electron energy distribution were compared.The simulation results show that both configurations can confine the diffusion of particles and can extract negative hydrogen ions;their electron energy distributions are basically similar,presenting double energy state,which are consistent with the basic mechanism of plasma discharge.The former configuration is stronger in confining and can produce more particles,whose total number is approximately four times that of the latter.The tent-shaped magnetic filter can efficiently prevent electron drift caused by inhomogeneous longitudinal magnetic field,leading to more uniform spatial distribution of negative hydrogen ions.The results of simulation are consistent with those from the foreign experiment.