Near-surface bipartition model for the study of material response of plasma-facing surfaces exposed to energetic charged particles

In order to predict the erosion rates and lifetimes of candidate plasma facing component (PFC) materials, the sputtering yields of Mo, W and deuterium-saturated Li surfaces bombarded by energetic charged particles were calculated by a new near-surface analytical sputtering model based on a bipartition model of charge particle transport theory. Lithium was considered as an alternative material providing low-recycling regime operation in advanced tokamak devices; expected charged-particle energies range from 100–1000eV. Comparisons were made with Monte Carlo calculations of the TRIM code and experimental results, where available. The maximum sputtering yield of W by 3keV He+ ions, for example, was 0.032 and for Li by 0.4keV He+ ions was 0.17. Also calculated were the dependencies of maximum energy deposition and particle and energy reflection coefficients on the incident energy of energetic runaway electrons impinging on different material surfaces. The results are particularly important for estimating the lifetime of PFCs and analyzing the extent of impurity contamination, especially for high-power density and with a high plasma current fusion reactor.