3D modeling of boron transport in DIII-D L-mode wall conditioning experiments
F. Effenberg, A. Bortolon, H. Frerichs, B. A. Grierson, J. Lore, T. Abrams, T.E. Evans, Y. Feng, R. Lunsford, R. Maingi, A. Nagy, R. Nazikian, D.M. Orlov, Jun Ren, D.L. Rudakov, W.R. Wampler, Huiqian Wang
Abstract
DIII-D L-mode experiments with local boron powder injection for real-time wall conditioning have been interpreted for the first time with the 3D plasma edge transport Monte Carlo code EMC3-EIRENE. Local B sourcing in plasma scenarios with upstream densities 1.5⋅1019 m−3 and 2.2 MW heating results in a non-axisymmetric B distribution in the scrape-off layer (SOL) and on the divertor. The SOL frictional flows at high plasma density cause a strong inboard drag of injected impurities (≈90%), while lower background plasma densities tend to result in a more uniform distribution. The thermal forces prevent B deposition in the near SOL while the frictional force causes B fluxes to cover the divertor plasma-facing components in a region 7–10 cm beyond the strike line. Radiative dissipation occurs for B influxes above 1⋅1020 s−1 and causes a moderate, non-axisymmetric reduction of the far SOL divertor heat fluxes. A comparison of top and midplane B injection shows no substantial difference in inboard vs. outboard asymmetries of the B distribution. On the other hand, erosion or recycling at the strike line may distribute the boron more uniformly in the SOL.