20cm口径离子推力器寿命模型及评估

Simulation of LIPS-200 Ion Thruster and Failure Analysis

为了系统地分析LIPS-200离子推力器交换电荷(CEX)离子对加速栅壁面的轰击溅射腐蚀机理,本文针对该推力器栅极系统最关键的两种磨损失效模式,即加速栅结构失效和电子反流失效,利用数值模拟Paritle-in-cell(PIC)和Monte-Carlo collision(MCC)方法,仿真模拟了束流引出过程中CEX离子的产生、加速及引出过程,得到了主束流离子空间位置分布、静电势分布、CEX离子分布和对应的密度分布。同时,采用数值仿真计算和理论分析相结合的方法对栅极寿命进行了评估。计算结果显示在现有几何结构和工作电参数一定的情况下,LIPS-200离子推力器栅极系统能很好地引出束流离子,无CEX离子直接轰击到加速栅壁面,程序统计到的整个栅极系统加速栅壁面截获的CEX离子电流约为9.76×10-4A。证明了加速栅电流的主要来源是冲击到壁面的CEX离子,计算得到的加速栅电流与束流电流比例为0.122%。LIPS-200离子推力器栅极寿命为11230.1 h,其对应的关键失效模式为加速栅结构失效。

The sputtering erosion of the acceleration grid assembly of LIPS-200 ion-thruster by the charge exchange xenon （CEX） ions,generated by collision between Xe-ions and neutral atoms, was approximated, modeled, analyzed and numerically simulated in Monte-Carlo collision method and with software Particle-in-ceU （PIC） to understand the grid＇ s failure mechanisms. The generation, acceleration and extraction of CEX ions were investigated;the spatial distributions of the Xe-ion beam, electrostatic potential and CEX density were calculated and the lifetime of the grid assembly was evalu- ated. The calculated and simulated results show that LIPS-200 ion-thruster is capable of extracting the beam current under the routine conditions; the grid surfaces suffer no direct sputtering erosion by the CEX ions; and that the CEX ion current, intercepted by the accelerator, is calculated to be 9.76 ×10.4 A, dominating the acceleration current and being only 0.122% of the beam current.The lifetime of LIlXS-200 ion-thruster is about 11230.1 h and erosion damage of the grid structure accounts for the failure mechanism.