Progress in modeling erosion and redeposition on plasma facing materials

The unavoidable contact of plasmas with surrounding walls results in plasma-surface interactions (PSIs). Computer modeling has become increasingly important in understanding PSI mechanisms within current fusion devices, ITER, and those beyond. This paper describes recent modeling codes covering various PSI themes and their physical and chemical bases. Particular emphasis is placed on physical and chemical sputtering of wall surfaces, transport of impurities released in the plasma, redeposition of returning impurities and resultant material mixing. Calculation results, such as those corresponding to light emission patterns above surfaces and deposition/erosion distributions on surfaces, are used for comparison with experimental observations made with small test limiters and tracing gas injections. Although the given profiles of various plasma parameters are taken from measurements or plasma code simulations, direct coupling to a plasma code is under development for the express purpose of better understanding local and global features of erosion and redeposition in fusion devices.