The Effect of Recycling C Ion Impact Energy and Angle on C/W Material Mixing and Intra-ELM W Erosion Predictions on the Small Angle Slot V-Shaped W Divertor at DIII-D*

The effect of various D₂ injection rates at the midplane and the impact on carbon (C) plasma impurity concentrations (%) and intra-edge localized mode (ELM) tungsten (W) erosion in the Small Angle Slot V-Shaped W (SAS-VW) divertor has been studied in the DIII-D tokamak. D_α (656.19 nm), WI (400.9 nm), and CIII (465 nm) filterscopes and Langmuir probes were used to determine deuterium (D) and C fluxes incident to the divertor, along with gross W erosion rates. The Free Stream Recycling Model (FSRM) vastly overpredicts intra-ELM W erosion using experimental parameters and may further overpredict intra-ELM W erosion for plasma shots with a higher C %. To correct the FSRM predictions, we incorporate a near-surface mixed-material C/W layer by multiplying the estimated fractional W concentration at the divertor. C ion-W material interactions computed by binary collision codes (RustBCA and SD.TRIM.SP) obtain C/W model sputtering and reflection coefficients at various C ion impact energies and angles, shown to have a large effect on the divertor C deposition and gross W erosion predictions. By coupling sputtered and reflected C distributions to GITR plasma transport codes, we provide novel estimations of the recycling C impact angle and consequent C coverage of the W divertor during ELMs.