离子推力器束流引出状态对栅极刻蚀的影响

孙明明; 耿海; 杨俊泰; 岳士超; 张文涛

doi:10.11884/HPLPB202133.200229

离子推力器束流引出状态对栅极刻蚀的影响

doi: 10.11884/HPLPB202133.200229

兰州空间技术物理研究所，真空技术与物理重点实验室，兰州 730000

基金项目: 国家自然科学基金项目（61901202，61901204）；十三五星箭可靠性增长项目（ZKCP0701）；国防科工局稳定支持重点实验室基金项目；民用航天预研项目（D010509）

详细信息

作者简介:
孙明明（1985—），男，博士，高级工程师，主要从事空间电推进技术研究；smmhappy@163.com

中图分类号: V439.4
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出版历程
- 收稿日期: 2020-08-03
- 修回日期: 2020-12-17
- 刊出日期: 2021-01-07

Influence of ion beam perveance condition on grids erosion for ion thruster

Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000, China

摘要

摘要: 为了研究30 cm离子推力器束流引出状态对栅极刻蚀的影响，建立了束流引出模型，并采用PIC-MCC方法对CEX离子造成的栅极腐蚀速率进行了计算，最后将计算结果与1500 h寿命试验结果进行比对分析。结果显示：束流正常聚焦时，在3 kW和5 kW两种工作模式下，加速栅和减速栅的质量刻蚀速率分别为(1.11～1.72)×10⁻¹⁵ kg/s及(1.22～1.26)×10⁻¹⁷ kg/s。在5 kW工况下，当屏栅上游等离子体密度达到4.03×10¹⁷ m⁻³时，束流出现欠聚焦现象，此时加速栅和减速栅的最大离子刻蚀速率分别为4.33×10⁻¹⁵ kg/s和4.02×10⁻¹⁵ kg/s；在3 kW工况下，当屏栅上游等离子体密度达到0.22×10¹⁷ m⁻³时，束流出现过聚焦现象，此时加速栅和减速栅的最大离子刻蚀速率分别为3.24×10⁻¹⁵ kg/s和5.01×10⁻¹⁵ kg/s。寿命试验结果表明，加速栅孔质量刻蚀速率的计算值与试验值比对误差较小，而由于束流离子对减速栅孔的直接轰击，导致减速栅孔刻蚀速率的计算值和试验值差异极大。经研究认为，对屏栅小孔采用变孔径设计，是降低当束流处于欠聚焦或过聚焦状态下，CEX离子造成加速栅孔和减速栅孔刻蚀速率，并提升推力器工作寿命的有效措施。
- 离子推力器 /
- 栅极腐蚀 /
- 束流 /
- 聚焦状态
Abstract: To study the influence of ion beam perveance condition on the grids erosion velocity for 30 cm diameter ion thruster, we established a beam perveance model and calculated the grids erosion velocity caused by CEX (charge exchange) ions by PIC-MCC method, and then compared and analyzed the calculation results with 1500 h short time life test results. The results show that under the normal beam perveance condition, the mass erosion velocity of the accelerator grid and the decelerator grid are (1.11−1.72)×10⁻¹⁵ kg/s and (1.22−1.26)×10⁻¹⁷ kg/s in 3 kW and 5 kW working modes, respectively. Under 5 kW working mode, when the upstream plasma density of the screen grid reaches 4.03×10¹⁷ m⁻³, the beam is under perveance condition, and the maximum ion erosion velocity of the accelerator grid and the decelerator grid is about 4.33×10⁻¹⁵ kg/s and 4.02×10⁻¹⁵ kg/s respectively. Under 3 kW working mode, when the upstream plasma density of the screen grid reaches 0.22×10¹⁷ m⁻³, the beam is in over perveance condition. Meanwhile, the maximum ion erosion velocity of the accelerator grid and the decelerator grid is about 3.24×10⁻¹⁵ kg/s and 5.01×10⁻¹⁵ kg/s respectively. The life test results show that the calculation value of mass erosion velocity of the accelerator grid hole has a small error to the test value. However, the calculation results of erosion velocity of the decelerator grid hole differ greatly from the test results, which is mainly because of the direct bombardment of the beam ions on the decelerator grid hole. From the current research conclusions, it is considered that the variable aperture design for the screen grid hole is an effective measure to reduce the erosion velocity of the accelerator grid hole and the decelerator grid hole caused by CEX ions when the beam is in under or over perveance condition. In addition, variable aperture design of the grids can significantly improve the working life of the thruster.
- ion thruster /
- grid erosion /
- ion beam /
- perveance condition

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图 1 离子束流引出过程示意图

Figure 1. Schematic diagram of the ion beam extraction process

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图 2 采用PIC-MCC方法的离子加速计算区域

Figure 2. Calculation region of ions acceleration based on PIC-MCC method

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图 3 不同工况下的CEX离子密度分布

Figure 3. CEX ion density in different work mode

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图 4 5 kW工况下的束流欠聚焦仿真结果

Figure 4. Simulation results of under perveance condition in 5 kW mode

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图 5 3 kW工况下束流过聚焦状态时的离子位置分布

Figure 5. Ions position distribution of over-perveance condition in 3 kW mode

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图 6 离子刻蚀后的加速栅小孔半径变化示意图

Figure 6. Radius of the accelerator grid hole after ion etched

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表 1 PIC-MCC方法的关键参数设置

Table 1. Parameters set for simulation by PIC-MCC method

${r_{{\rm{sc}}}}$/mm	${r_{{\rm{ac}}}}$/mm	${t_{{\rm{sc}}}}$/mm	${t_{{\rm{ac}}}}$/mm	${d_{{\rm{s - a}}}}$/mm	${r_{{\rm{del}}}}$/mm	${t_{{\rm{del}}}}$/mm	${V_{{\rm{acc}}}}$/V
0.95	0.55	0.40	0.50	1	0.65	0.5	−400

${V_{\rm{p}}}$/V	${T_{\rm{i}}}$/K	${T_{{\rm{eu}}}}$/eV	${T_{{\rm{ed}}}}$/eV	${n_{\rm{0}}}$/m⁻³	${V_{{\rm{sc}}}}$/V	${d_{{\rm{a - d}}}}$/mm	${V_{{\rm{del}}}}$/V
37	600	4.5	1.50	−	1200	0.9	0

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表 2 离子推力器不同工作模式的输入条件

Table 2. Input parameters of ion thruster in different work mode

work mode	anode mass flow/（kg·s⁻¹）	cathode mass flow/（kg·s⁻¹）	total mass flow/（mg·s⁻¹）	anode voltage/V
3 kW	1.97	0.38	2.35	32
5 kW	5.37	0.26	5.63	30.5

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表 3 栅极上游中性原子密度分布

Table 3. Neutral density in upstream of the grids

work mode	${n_{\rm{0}}}$/m⁻³	${n_{{\rm{01}}}}$/m⁻³	anode voltage/V	screen grid voltage/V	accelerator grid voltage/V
3 kW	1.42×10¹⁷	8.75×10¹⁷	32	1415	−220
5 kW	3.36×10¹⁷	2.11×10¹⁸	30.5	1165	−400

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表 4 不同模式下的刻蚀速率仿真计算结果

Table 4. Simulation results of erosion velocity in different work mode

work mode	erosion velocity of acc. grid/（kg·s⁻¹）	erosion velocity of dec. grid/（kg·s⁻¹）
3 kW	1.11×10⁻¹⁵	1.22×10⁻¹⁷
5 kW	1.72×10⁻¹⁵	1.26×10⁻¹⁷

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