本底真空对推力器加速栅截获CEX离子电流

Simulation of Influence of Base Pressure on Ion Thruster Accelerator Grid Charge Exchange Ion Current

离子推力器地面寿命考核和加速寿命试验是在地面真空舱中进行的,真空舱本底真空会对离子推力器性能和寿命特别是加速栅截获电流有重要影响。为了确定20 cm氙离子推力器地面试验本底压力,本文采用PIC-MCC方法,计算了不同本底真空下栅极系统中性原子位置、密度分布和交换电荷(Charge Exchange,CEX)离子位置、速度和密度分布。模拟计算了在不同真空舱本底真空下20 cm氙离子推力器加速栅极截获的CEX离子电流,与实验结果符合较好,并通过理论方法确定了加速栅电流随真空舱本底真空变化的"拐点"。计算结果可以为离子推力器长寿命考核试验和栅极系统加速寿命试验真空舱本底真空的选择提供了参考。

The impacts of the base pressure in vacuum chamber on various key factors of the ion thruster, such as the service lifetime of the thruster, operational life proof cycle of acceleration, and charge exchange（ CEX）ion current of the accelerator grid were modeled and simulated to optimize the base pressure in the ground simulation test of the 20cm xenon ion thruster. The position and density distributions of the neutral atoms and CEX ions, and CEX ion velocity distri- bution at different base pressures were simulated with software package PIC-MCC. In addition, the influence of the base pressure on the CEX ion current in the 20 cm xenon ion thruster accelerator grid, originated from the impinging CEX ions on the surfaces of the grid, was modeled, simulated and tested. The simulated CEX ion current was found to agree fairly well with the measured result, and the inflection of the dependence of the CEX ion current on the base pressure was also theoretically determined.