TITLE: Numerical Studies of Sheath at Tokamak Edge*

Plasma-surface interaction has been considered to be of great importance during a tokamak disruption event. Plasma particles interact with solid surface within the sheath layer which has a strong influence on the particle and energy flux towards the wall. In classical sheath model, many assumptions are made in order to obtain a simplified analytical model. However, at the tokamak edge, where sharp temperature gradient, strong inelastic collisions, and high recycling regime exists, some of the assumptions may not be valid. Thus, a kinetic study of divertor sheath will be helpful for understanding the physics. In present work, we develop a Monte Carlo Collision (MCC) package for vector particle in cell (VPIC) code, where elastic and inelastic interactions between charged particles and neutrals are included. Simulation results of plasma distribution profile and sheath parameters will be presented.