氮化硼微结构表面低能电子诱导次级电子发射的Monte Carlo模拟
Monte Carlo modeling of low-energy electron-induced secondary electron emission yields in micro-architected boron nitride surfaces
摘要：
表面腐蚀和次级电子发射（SEE）是空间推进用霍尔效应推力器通道壁最关键的寿命限制因素。最近提出了基于微结构表面的壁概念，以减轻表面侵蚀和SEE。这些设计背后的想法是利用非常高的表面积与体积比，通过内部捕获和再沉积来减少SEE和离子侵蚀。这导致了新的兴趣，研究相关的推力器壁材料中的电子-电子过程。在这项工作中，我们提出了计算的SEE产量在微孔六方BN表面使用随机模拟的离散表面几何形状的电子-材料相互作用。我们的模型由两个互补的部分组成。首先，我们使用电子多次散射过程的蒙特卡罗模拟研究了作为初级电子能量和入射角的函数的平面中的SEE。然后，使用的结果表示的响应函数的离散的表面元素，使用射线跟踪蒙特卡罗模型产生的单个电子射线。我们发现，微孔表面导致SEE产量减少超过50%的能量范围内经历霍尔推进器。这表明这些微结构表面概念适用于减轻紧凑型电力推进装置中的SE相关问题。
英文摘要：
Surface erosion and secondary electron emission (SEE) have been identified as the most critical life-limiting factors in channel walls of Hall-effect thrusters for space propulsion. Recent wall concepts based on micro-architected surfaces have been proposed to mitigate surface erosion and SEE. The idea behind these designs is to take advantage of very-high surface-to-volume ratios to reduce SEE and ion erosion by internal trapping and redeposition. This has resulted in renewed interest to study electron-electron processes in relevant thruster wall materials. In this work, we present calculations of SEE yields in micro-porous hexagonal BN surfaces using stochastic simulations of electron-material interactions in discretized surface geometries. Our model consists of two complementary parts. First we study SEE as a function of primary electron energy and incidence angle in flat surfaces using Monte Carlo simulations of electron multi-scattering processes. The results are then used to represent the response function of discrete surface elements to individual electron rays generated using a ray-tracing Monte Carlo model. We find that micro-porous surfaces result in SEE yield reductions of over 50% in the energy range experienced in Hall thrusters. This points to the suitability of these micro-architected surface concepts to mitigate SEE-related issues in compact electric propulsion devices.
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