Multi-physics modeling of the long-term evolution of helium plasma exposed surfaces
A. Lasa, J.M. Canik, Sophie Blondel, Tim Younkin, Davide Curreli, Jon Drobny, Philip C. Roth, M. Cianciosa, Wael Elwasif, David L. Green, Brian D. Wirth
Abstract
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.