Erosion/redeposition analysis: status of modeling and code validation for semi-detached tokamak edge plasmas.

摘要

We are analyzing erosion and tritium codeposition for ITER, DIII-D, and other devices with a focus on carbon divertor and metallic wall sputtering, for detached and semi-detached edge plasmas. Carbon chemical-sputtering hydrocarbon-transport is computed in detail using upgraded models for sputtering yields, species, and atomic and molecular processes. For the DIII-D analysis this includes proton impact and dissociative recombination for the full methane and higher hydrocarbon chains. Several mixed material (Si-C doping and Be/C) effects on erosion are examined. A semi-detached reactor plasma regime yields peak net wall erosion rates of (approximately)1.0 (Be), (approximately)0.3 (Fe), and (approximately)0.01 (W) cm/burn-yr, and (approximately)50 cm/burn-yr for a carbon divertor. Net carbon erosion is dominated by chemical sputtering in the (approximately)1-3 eV detached plasma zone. Tritium codeposition in divertor-sputtered redeposited carbon is high ((approximately)10-20 g-T/1000 s ). Silicon and beryllium mixing tends to reduce carbon erosion. Initial hydrocarbon transport calculations for the DIII-D DiMES-73 detached plasma experiment show a broad spectrum of redeposited molecules with (approximately)90% redeposition fraction.