Multi-physics modeling of the long-term evolution of helium plasma exposed surfaces

In this manuscript we introduce a simulation tool-suite for predicting plasma-surface interactions (PSI), which aims to predict the evolution of the plasma-facing surfaces that continually change due to exposure to fusion plasmas. A comprehensive description of PSI involves a wide range of physical phenomena, of which we include components for (a) the gas implantation and its dynamic evolution below the divertor surface; (b) erosion of wall material; (c) transport and re-deposition of the eroded impurities; and (d) the scrape-off layer plasma including fuel ions and extrinsic impurities. These components are integrated to predict changes in surface morphology and fuel recycling, and the effect of material erosion and re-deposition in fuel retention. Integrated simulations for ITER-like parameters in a helium plasma environment are presented, focused on the response of the tungsten divertor. The model is also applied to predicting the response of the tungsten surface pre-damaged by He plasma, to burning plasma operations. This case further demonstrates the capability to model the effect of sub-surface helium dynamics, which include helium nucleation, clustering and the bursting of over-pressurized bubbles, its impact on fuel recycling as well as the effect of sputtering on the surface evolution.