Molecular dynamics simulation and modelling on the dust-wall interactions in tokamak

Abstract

Dust velocity in fusion devices covers a wide range (several hundreds of m/s to over 10 km/s), which can cause various interactions between energetic dust grains and wall materials. Dust grain with low energy can influence the wall properties by deposition. Intense dust-wall interactions can cause serious wall damage such as sputtering, degradation, deformation and so on. As beryllium and tungsten are the material of the first wall and divertor, respectively, systematically molecular dynamics simulations have been performed to study the interactions between beryllium/tungsten dust and the beryllium/tungsten wall in the present study. A wide range of dust velocity has been considered to cover the velocity from experiments. Our result shows that the influences of dust on the wall are greatly affected by the impact velocity of dust grains and the properties of the wall material. A detailed analysis shows that the dust-wall interaction can be divided into four levels and an analytical model has been developed to explain the mechanism. Character velocities that separate the interaction levels are also provided by the model. The comparison between the MD result and the model shows a good agreement. Our result is helpful for the understanding of the mechanisms and the prediction of dust-wall interactions.