Computational analysis of plasma-wall interactions in beryllium: A detailed study of physical and chemically assisted physical sputtering

Understanding plasma-wall interactions is one of the main challenges in the design and development of fusion reactors. Among the primary effects of these interactions is the erosion of plasma-facing components through physical or chemical sputtering, which can limit the availability and performance of the device. We simulate this phenomenon in beryllium surfaces with varying concentrations of hydrogen isotopes using atomistic molecular dynamics. Special attention is given to chemical sputtering and the overall behavior of molecules emitted from the surface. Our findings indicate that the balance between physical and chemical sputtering is considerably affected by isotope type, impact energy, and incident angle of the plasma particle. We compare the results with predictions from SDTrimSP, a tool that utilizes the more computationally efficient binary collision approximation, to elucidate the conditions where the higher accuracy of molecular dynamics is needed. Moreover, we highlight the effect of surface temperature, which determines the concentration of hydrogen isotopes in the surface layers, on the contribution of chemical sputtering to total erosion, and the types of sputtered molecules. Lastly, we demonstrate that the escape energies and angles of the sputtered species are also significantly influenced by the impact energy and angle of the plasma particles.