Tungsten divertor sourcing in DIII-D H-mode discharges and its impact on core impurity accumulation in different ELM regimes
ORAL
Abstract
Significant progress has been made understanding W sourcing during Type I ELMy H-mode on DIII-D using fast high-resolution measurements of W sourcing coupled with OEDGE/ERO and TRIM.SP modeling. ERO modeling of the inter-ELM phase, using a new OEDGE capability for charge state-resolved carbon ion fluxes and a material mixing model, shows measured W erosion is well explained by C-$>$W sputtering. Ion impact energies in the DIII-D divertor during ELMs, inferred from ratios of heat flux to ion flux, are 200-500 eV. Comparisons with TRIM.SP indicate C-$>$W sputtering dominates W sourcing during ELMs. This is in contrast to JET where ion impact energies are 3-5 keV during ELMs, predicted by the "free streaming model," and D-$>$W sputtering strongly contributes to W sourcing. Fast measurements of W erosion dynamics during ELMs agree well with TRIM.SP-based sputtering models assuming C/W surface concentrations of 0.5-0.8 and a 2$\%$ C$^{2+}$ ion flux fraction. Core W accumulation and SOL W density measurements made during the DIII-D high-Z tile array mini-campaign correlate with ELM frequency and W source rate.
*Supported by US DOE under DE-FC02-04ER54698
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