中文摘要：

为优化离子推力器中栅极系统设计，采用三维粒子云网格（PIC）仿真方法对三栅极系统等离子体输运过程进行了仿真，并与两栅极仿真结果进行对比，分析了三栅极特有的减速栅对栅极系统内束流分布、电子返流阀值、截止电流和交叉电流阀值、离子通过率和发散角损失等参数的影响。研究结果表明减速栅的主要作用包括：对离子通过率无影响，对截止电流影响不明显，但可大幅减弱甚至消除交叉电流限制问题；对加速栅腐蚀有明显的抑制作用，工作区间内的加速栅电流降低50％；增强了下游区域的径向电场，部分离子会偏离主束流区域，导致发散角损失增大；可改善加速栅孔附近电势分布，对电子返流阀值影响明显，对于1-4A的束电流，仅需-60—50 v的负偏压便可实现对电子返流的抑制。

英文摘要：

To optimize the optics systems of ion thrusters, we simulated a plasma transport process in three-grid systemusing the 3-D particle in cell （PIC） method, compared the results with the simulation of two-grid systems, and discussedthe impact of decelerator grid on the ion distribution, electron reflux threshold, cut-off current threshold, crossover currentthreshold, ion through rate, and divergence loss. Based on the results, the main effects of introducing decelerator grid intothe system were summarized. It is found that introducing decelerator grid does not affect the ion rate but affects thecut-off current, and it greatly reduces or even eliminates the limitation of cross current. Moreover, introducing deceleratorgrid inhibits the corrosion of accelerator grid through reducing the current in accelerator grid current in operating range byabout 50%, and greatly enhances the radial electric field of downstream, which makes ions to deviate from the main beamregion and hence lead to a higher divergence loss. Therefore, the potential distribution around the accelerator grid hole isimproved and the electron backstream threshold is remarkably affected： for a beam current of 1-4 A, a negative bias vol-tage of only -60--50 V can realize the suppression of electron backstream.