Plasma–surface interactions caused by electric propulsion devices are an important spacecraft aspect of the design that is difficult to measure in ground-based facilities. The negatively biased solar panel surfaces attract the slow-moving charge exchange (CEX) ions generated inside an ion core plume, which can cause surface sputtering on the protective coatings of the solar panels. We use a fully kinetic particle-in-cell direct simulation Monte Carlo (PIC-DSMC) approach that models both electron and ion trajectories to allow us to fully characterize the plasma sheath formed near these surfaces and to understand how the plasma sheath affects the trajectories of CEX ions, their incident energies and angles, and surface sputtering rates. We find that, outside the plasma core, the ion and electron distribution functions are highly non-Maxwellian, and the assumption of electron temperatures is questionable. We introduce a novel floating potential ground boundary condition that enables us to emulate the spacecraft ground for a high range of plasma number densities and surface charging conditions. Finally, we estimate the erosion of the surface using the kinetic results and surface yield empirical relations.

中文翻译：

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羽流回流区域中航天器表面的动力学建模

由电力推进装置引起的等离子体-表面相互作用是航天器设计的一个重要方面，在地面设施中难以测量。负偏压的太阳能电池板表面会吸引离子核心羽流内产生的缓慢移动的电荷交换 (CEX) 离子，这会导致太阳能电池板保护涂层的表面溅射。我们使用完全动力学粒子在细胞内直接模拟蒙特卡罗 (PIC-DSMC) 方法，该方法对电子和离子轨迹进行建模，使我们能够充分表征在这些表面附近形成的等离子体鞘，并了解等离子体鞘如何影响轨迹CEX 离子、它们的入射能量和角度以及表面溅射速率。我们发现，在等离子体核心之外，离子和电子分布函数是高度非麦克斯韦分布的，并且电子温度的假设是有问题的。我们引入了一种新颖的浮动电位地面边界条件，使我们能够模拟航天器地面的高等离子体数密度和表面充电条件。最后，我们使用动力学结果和表面屈服经验关系来估计表面的侵蚀。