Dynamics of melting, evaporation, and resolidification of materials exposed to plasma disruptions

Abstract

First wall components exposed to a high energy flux during a plasma disruption experience a sequence of processes which consists of rapid heating, melting, intense evaporation, resolidification, and cool-down. The dynamics of all these processes has an impact on both the melt layer stability and the thermal stress cycle in the component of the first wall that stays solid. The detailed time history of the temperature distribution is accurately computed by solving a two-moving-boundary problem. The time behavior of the melt layer thickness for both stainless steel and molybdenum is calculated for different disruption energies and different energy fluxes. The duration of melting, which is an important factor in determining the melt layer stability under different forces, is calculated for both stainless steel and molybdenum. The duration of the melt layer may in fact be shorter for materials with thicker melt layers. The effect of vapor shielding (the stopping of the incoming plasma ions by the vaporized wall material) on the dynamics of melting is also investigated.