Abstract The authors redesigned the discharge chamber for the μ10 microwave discharge ion thruster to improve its thrust performance and succeeded in enhancing the maximum beam current and thrust efficiency. However, it was found that the ion current ratio extracted from the discharge chamber with the redesigned configuration was lower than that obtained with the original configuration. To investigate the relationship between ion extraction and the magnetic field geometry, the ion loss current distribution in these two types of discharge chamber were measured by electrostatic probes. Using planar probes with a guard ring, the ion current that flowed into the wall was measured without disturbing the ion beam current. The results show that ionization occurs mainly near the upstream magnet. In addition, the ion flux on the sidewall in the redesigned discharge chamber is about 1.5-2 times larger than that in the original discharge chamber. This suggests that the distance between the edge of the plasmaproduction region and the chamber wall with consideration of the Larmor radius of ions is an important parameter in discharge chamber design. In addition, although the ion beam current showed a tendency to saturate at high microwave power, the ion loss to each part in the discharge chamber increased in proportion to input microwave power. The decrease in the extracted ion ratio in the redesigned discharge chamber is considered to be caused by a decrease in the electrostatic ion transparency of the screen grid. Therefore, in a well-tuned microwave discharge ion thruster, it is difficult to improve the thrust efficiency by increasing the discharge power. A design that suppresses the wall loss of ions is thus important.

中文翻译：

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放电室几何形状对微波放电离子推进器中离子损失的影响

摘要 作者重新设计了μ10微波放电离子推进器的放电室，以提高其推力性能，并成功提高了最大束流和推力效率。然而，发现从具有重新设计的配置的放电室中提取的离子电流比低于使用原始配置获得的离子电流比。为了研究离子提取与磁场几何形状之间的关系，通过静电探针测量了这两种放电室中的离子损失电流分布。使用带有保护环的平面探针，可以在不干扰离子束电流的情况下测量流入壁的离子电流。结果表明电离主要发生在上游磁体附近。此外，重新设计的放电室侧壁上的离子通量比原来的放电室大1.5-2倍左右。这表明在考虑离子的拉莫尔半径的情况下，等离子体产生区边缘与室壁之间的距离是放电室设计中的一个重要参数。此外，虽然离子束电流在高微波功率下呈现饱和趋势，但放电室中各部分的离子损失与输入的微波功率成正比增加。重新设计的放电室中提取离子比的降低被认为是由屏栅静电离子透明度降低引起的。因此，在调谐良好的微波放电离子推进器中，增加放电功率难以提高推力效率。因此，抑制离子壁损失的设计很重要。