Modeling tungsten response under helium plasma irradiation: a review

Tungsten, a leading candidate for plasma-facing materials (PFM) in future fusion devices, will be exposed to high-flux low-energy helium plasma under the anticipated fusion operation conditions. In the past two decades, experiments have revealed that exposure to helium plasma strongly modifies the surface morphology and hence the sputtering, thermal and other properties of tungsten, posing a serious danger to the performance and lifetime of tungsten and the steady-state operation of plasma. In this article, we provide a review of modeling and simulation efforts on the long-term evolution of helium bubbles, surface morphology, and property changes of tungsten exposed to low-energy helium plasma. The current gap and outstanding challenges to establish a predictive modeling capability for dynamic evolution of PFM are discussed.