The ion thruster plume model was established and a numerical simulation using the particle-in-cell method was a-dopted to obtain charge-exchange(CEX) ions distribution in the plume. The full approximation storage-algebraic multigrid method is used to update the electric field. A three dimensional parallel particle simulation code has been developed by using the compute unified device architecture for graphic processor unit. The results show that CEX ions will go toward outside of the ion beam due to the expansion structure of the electric potential and some will go back to the upstream of the ion thruster. The ion number density is three to four order lower than that in the beam. The backflow current of CEX ions will be reduced as the electric temperature in the plume is reduced.%建立了离子发动机羽流的物理模型,采用粒子网格对羽流中的交换电荷离子的分布进行了模拟,电场方程使用完全近似格式的代数多重网格方法求解.利用计算设备统一架构技术开发出一套基于图形处理器的3维并行粒子模拟程序.计算结果表明,交换电荷离子在径向扩张型电势结构下会向束流区外运动,一部分交换离子在电场力作用下会向发动机上游运动,从而形成返流.发动机上游区域的交换电荷数密度与束流等离子体数密度相比降低了3～4个数量级.通过降低电子温度可有效降低返流电流.
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