计算微结构表面次级电子发射的蒙特卡罗射线追踪法
Monte Carlo Raytracing Method for Calculating Secondary Electron Emission from Micro-Architected Surfaces
摘要：
空间推进电推力器等离子体室内衬层的次级电子发射（SEE）会对装置的性能和效率产生破坏性影响。SEE通常使用弹性和非弹性电子散射理论通过独立电子轨迹的蒙特卡罗模拟来计算。然而，在实践中，该方法只能应用于理想的光滑表面和薄膜，不代表真实的材料表面。最近，已经提出了具有纳米特征的微结构表面，以减轻等离子体暴露的推力器衬里中的SEE和离子诱导的侵蚀。在本文中，我们提出了一种方法来计算次级电子产额从任意复杂的几何形状的表面使用的\emph{ray tracing}蒙特卡罗（RTMC）技术的扩展。我们研究了具有不同孔隙率的纳米泡沫结构作为代表性的微结构表面，并使用RTMC产生初级电子轨迹和跟踪次级电子，直到它们从外表面逃逸。实际表面表示为从钨纳米泡沫的X射线断层扫描图像获得的离散有限元网格。在局部水平上，撞击到表面元件中的初级射线产生次级电子的子射线，其数量、能量和角度特性由来自理想平坦表面的SEE产率和能量的预先计算的表格设定。我们发现，这些微结构的几何形状可以减少SEE高达50%，相对于平坦的表面取决于孔隙率和初级电子能量。
英文摘要：
Secondary electron emission (SEE) from inner linings of plasma chambers in electric thrusters for space propulsion can have a disruptive effect on device performance and efficiency. SEE is typically calculated using elastic and inelastic electron scattering theory by way of Monte Carlo simulations of independent electron trajectories. However, in practice the method can only be applied for ideally smooth surfaces and thin films, not representative of real material surfaces. Recently, micro-architected surfaces with nanometric features have been proposed to mitigate SEE and ion-induced erosion in plasma-exposed thruster linings. In this paper, we propose an approach for calculating secondary electron yields from surfaces with arbitrarily-complex geometries using an extension of the \emph{ray tracing} Monte Carlo (RTMC) technique. We study nanofoam structures with varying porosities as representative micro-architected surfaces, and use RTMC to generate primary electron trajectories and track secondary electrons until their escape from the outer surface. Actual surfaces are represented as a discrete finite element meshes obtained from X-ray tomography images of tungsten nanofoams. At the local level, primary rays impinging into surface elements produce daughter rays of secondary electrons whose number, energies and angular characteristics are set by pre-calculated tables of SEE yields and energies from ideally-flat surfaces. We find that these micro-architected geometries can reduce SEE by up to 50\% with respect to flat surfaces depending on porosity and primary electron energy.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
