Ion Backscattering and Sputtering of Plasma-Irradiated Carbon and Tungsten Surfaces in an Oblique Magnetic Field

Abstract

A Monte Carlo simulation model which combines ion backscattering and sputtering of solids with transport of emitted particles in the scrape-off layer plasma is developed for the study of the plasma-wall interaction in magnetic confinement fusion devices. The emphasis is put on the precise understanding of ionization and redeposition processes of backscattered and sputtered particles. In the model, Maxwellian ion-solid interaction, ionization of backscattered and sputtered neutral particles in the plasma, and gyromotion of the ionized particles in an oblique magnetic field are included. The heavier masses (lower charge states and lower energies) the particles have, the more they are redeposited. Due to impact of carbon ions on carbon and tungsten, therefore, less backscattered carbon is redeposited, whereas most of the sputtered tungsten atoms are redeposited. The redeposition causes substantially lower effective sputtering yields and a decrease in low-energy component of the sputtered atoms.