A plasma-wall interaction model for the erosion of materials under ion bombardment

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Logarzo, Hernan Javier
Rimoli, Julian J.
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Understanding the evolution and behavior of materials exposed to plasma is critical for the design of future electric propulsion devices. As ions are ejected from the device generating thrust, they also impact the ceramic walls. This induces wall erosion, ultimately exposing the magnetic circuit leading to malfunction and failure of the device. This problem is only going to be amplified as the field moves towards high power density devices. There are several models that try to predict this effect by accounting for material sputtering. However, they cannot predict the millimeter-scale surface features that develop after prolonged exposure. In this work, we address this issue by introducing a plasma-material interaction model able to capture the evolution of surface features at the macroscopic scale on materials exposed to plasma over a long period of time. The model is based on (i) data from plasma dynamics simulations, (ii) a probability model of erosion, (iii) geometric effects to account for shadowing effects and feature size and (iv) a continuum finite element model for the thermo-mechanical response of the dielectric walls that uses machine learning to account for the complex response of the material. Results show that the model is able to reproduce not only the mean erosion rate but also the macroscopic anomalous ridges that appear after prolonged exposure. Furthermore, it highlights the need to account for complex thermo-mechanical material behavior to be able to explain such features.
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