Simulation of arc crater formation and evolution on plasma facing materials

Abstract

Abstract Arc erosion on plasma facing materials in tokamak devices is a potential source of impurities and dust in plasma. A two dimensional axially symmetric COMSOL model with heat transfer, fluid dynamics including phase transition and surface tension effect has been used to describe the formation and evolution of arc craters on plasma facing materials. The formation and evolution of arc crater on W cathode is described in detail. The energy flux loading causes melting of central area within a few nanoseconds. Due to the gradients of incident pressure, the melted layer is extruded out, and thus forms the melt jets. The differences of the arc craters on several related materials in tokamaks under the same pressure and energy flux density are also discussed. The crater temperature of W and Mo is much higher than that of Cu and Al. And, the melting volume of refractory metals W and Mo is significantly lower than that of Cu and Al. Refractory metals are more difficult to be damaged by the arcs, and more suitable for plasma facing materials.