A Modified EDDY Code to Simulate Erosion/Redeposition of Carbon Target in an ITER-FEAT Divertor

Modification of a Monte Carlo simulation code, Erosion and Deposition based on DYnamic model (EDDY), for plasma-surface interactions in a designed tokamak, International Thermonuclear Experimental Reactor-Fusion Energy Advanced Tokamak (ITER-FEAT), and its application for erosion and redeposition of a carbon target in the divertor are presented. The modified EDDY code allows us to treat the deposition of plasma impurities and the prompt redeposition of sputtered atoms and molecules on the target surface. At elevated temperatures, furthermore, the impurity diffusion inside the target and chemical sputtering of carbon are taken into account. In the ITER-FEAT, physical sputtering of the divertor target is very small in the scrape-off layer (SOL) region, and chemical sputtering dominates the erosion near the strike point and in the private flux region. Prompt redeposition strongly suppresses the sputtering of the target and plasma carbon impurity deposits on it. As a result, no erosion is calculated in the SOL region and a thick deposition layer is produced near the strike point. A narrow erosion zone remains only in the private flux region. Furthermore, radial distributions of each particle species released in the plasma and their redeposition profiles on the surface are discussed.