多模式离子推力器栅极系统三维粒子模拟仿真

栅极系统是离子推力器推力产生的主要部件,推力器的性能和寿命都与栅极系统密切相关.对于具有多种工作模态的离子推力器,基于电流电压入口的仿真可以有效评估推力器的工作状况.采用三维粒子模拟方法对两栅极系统等离子体输运过程进行了仿真,获得了不同模式下的推力器性能参数,对比NSTAR的在轨测试参数,验证了模型的正确性;分析了工作模式变化对栅极区域电场分布和束流状态的影响以及离子推力器多模式设计需求.分析结果表明:远离栅极系统的外凸型屏栅鞘层和内凹型零等势面、低鞍点电势值和平缓的下游电势分布,有利于提高栅极系统离子通过率,抑制电子返流,减小Pits-and-Grooves腐蚀,是离子推力器工作模式的设计方向;提高束流电压会导致发散角损失增大,但可扩展栅极工作电流范围,在束流强度较大的模式下,使束流具有较好的聚焦状态,有利于减小Barrel腐蚀.研究结果为多模式离子推力器工作模式设计提供了参考.

Three-dimensional particle in cell simulation of multi-mode ion thruster optics system

The optics is one of the main components of an ion thrust, which influences the performance and thruster lifetime. The operation of ion thruster can be evaluated by numerical simulation based on the current-voltage entrance condition, especially for thruster with a variety of operating modes. The plasma transport process is simulated with 3D-PIC (particle in cell) method for a two-grids optic. The performances of the NSTAR thruster under different operating modes are calculated and compared with the results of in-orbit test, verifying the correctness of the simulation mode. The influences of operation modes on the electric field distribution and the beam state are analyzed, and the requirements of multi-mode design for ion thruster are discussed. The results show that a convex sheath and concave zero equipotential surface away from the optic, low value of “saddle point”, and gentle downstream potential distribution, which help to improve ion pass rate, suppress electronic reflux and reduce Pits-and-Grooves corrosion, are the target of ion thruster mode design. Increasing beam voltage will result in a high loss caused by the divergence angle, and extend the beam current range for a good operation condition. For a large beam current mode, high beam voltage will make the beam have a better “focus” state, and reduce the Barrel corrosion. The results will provide a reference for the operation mode design for the multi-mode ion thruster.
Keywords： particle in cell ion thruster optic plasma simulation