Modelling and analysis of DIII-D/DiMES sputtered impurity transport experiments

A comprehensive modelling effort to analyse sputtering erosion and redeposi tion in the DIII-D/DiMES 70, 71 and 79 experiments using metal films (beryl lium, vanadium, molybdenum, tungsten) on a carbon divertor probe hay been p erformed. These materials were exposed at the outer strike point of an atta ched H mode plasma with peak at T-e similar to 75 eV. The analysis uses cou pled impurity transport (REDEP, WBC) and related codes with inputs of measu red plasma parameters. The code output was compared with measured erosion a nd redeposition profiles, and other data. The predicted redeposition profil es for beryllium, carbon, molybdenum and tungsten agree well with the data. Beryllium and carbon exhibit longer transport distances compared with thos e of high-Z metals - primarily due to longer mean free paths for sputtered atom ionization. Photon emission calculations for beryllium also compare we ll with the data, thereby tending to validate coupled models for plasma par ameters, impurity transport and atomic data. For vanadium the comparison of the code with the data varies from poor to fair depending on the ionizatio n model used. For most metal films, the absolute erosion is less than that predicted for the 'pure' metal, a fact iue attribute to the effect of a car bon overlay or mixture. For carbon the predicted peak net erosion rate (sim ilar to 4 nm/s) is approximately 5 times less than the gross rate, and this is confirmed by the data. Carbon net erosion and core contamination result primarily from the quiescent (intra-ELM) period oblique incidence deuteriu m physical sputtering and self-sputtering. ELM period sputtering: and chemi cal erosion appear to play a small role in net erosion in these plasmas.