# Monte Carlo modeling of low-energy electron-induced secondary electron emission yields in micro-architected boron nitride surfaces

## TL;DR

This study uses Monte Carlo simulations to analyze how micro-porous boron nitride surfaces can significantly reduce secondary electron emission yields, improving the durability of Hall-effect thruster walls.

## Contribution

It introduces a novel stochastic modeling approach combining multi-scattering Monte Carlo simulations with ray-tracing to evaluate SEE yields on micro-architected BN surfaces.

## Key findings

- Micro-porous BN surfaces reduce SEE yields by over 50%.
- The model accurately predicts SEE behavior across relevant energy ranges.
- Micro-architected surfaces are promising for mitigating SEE in electric propulsion.

## Abstract

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.