LIPS-200离子推力器放电室出口离子密度分布研究

Study on Ion Density Distribution in Discharge Chamber Exit of LIPS-200 Ion Thruster

为了明确国内200 mm口径离子推力器放电室出口(即栅极上游附近)离子密度径向分布,采用实验与数值仿真相结合的方法对LIPS-200推力器放电室出口离子密度进行研究。应用法拉第筒分别测试推力器栅极下游50mm和100mm位置处束流特性,结合经验模型计算出栅极出口(z=0mm)束流离子径向分布。在此基础上,通过栅极数值模拟仿真,分析出栅极系统透过率随栅孔电流变化关系,进而反推计算出放电室出口离子密度径向分布。结果显示:放电室出口离子密度平均值约为9.0×10^(17)m^(-3),最大值约为1.54×10^(18)m^(-3),最小值约为4.6×10^(17)m^(-3);离子密度径向分布具有较好的中心轴对称性,离子密度从中心处沿着径向先缓慢减小,在径向位置约为50mm时出现快速下降;对比放电室出口与栅极出口离子密度径向分布发现,中心位置两者相差最大,边缘处相差最小。

In order to clarify the ion density distribution in discharge chamber exit of a 200mm diameter ion thruster, the ion density distribution in the discharge chamber exit of the LIPS-200 thruster is analyzed and discussed based on the combination of experiment and numerical simulation. The beam characteristics at 50mm and 100ram downstream of the accelerator grid are measured by a Faraday cup, and then the ion current radial distribution in the accelerator grid exit is calculated combined with empirical model. Further, the relationship between grid system transmittance and the grid current is obtained by optics system numerical simulation. At last the ion density radial distribution in the discharge chamber exit is calculated. The results show that the average ion density in discharge chamber exit is 9.0×l0^17m^-3, the maximum is 1.54×10^18m^-3 and the minimum is 4.6×10^17m^-3. The ion density radial distribution has a good central axial symmetry, ion density decrease slowly from the center along the radial direction and drop rapidly near the radial position of 50mm. Compared with the ion density in the discharge chamber exit and accelerator grid exit, there are the largest difference at the center but the smallest at the edges.