WallDYN simulations of material migration and fuel retention in ITER low power H plasmas and high power neon-seeded DT plasmas

Abstract

Deposition and fuel retention profiles in low power hydrogen L-mode plasmas and neon (Ne) seeded ITER DT burning plasmas have been investigated. Two different Ne seeded plasma backgrounds with varying sub-divertor neutral pressures but the same Ne impurity concentration are considered, representing high recycling and partially detached divertor solutions. The 2D SOLPS numerical grid does not extend all the way to the wall surfaces so that an extrapolation of the plasma background is required and is performed using a second simulation stage in which the far scrape-off layer (SOL) region is numerically gridded and plasma transport solved on the extended grid using the OSM (a 1D simplified Braginski code) approach [1]. The plasma conditions chosen for this far SOL region strongly influence the results. The hydrogenic flux is calculated from the electronic density and ion flow, the latter of which has an assumed distribution. Depending on the main-SOL plasma flow parameters and far-SOL density, fuel retention is driven by deposition on the first wall (when parallel flow through the main-SOL is switched off), or by deposition on the divertor (parallel flow through the main-SOL is switched on). When retention is dominated by deposition on the first wall, there is slightly more retention in the partially detached case compared to a high recycling scenario. In the low power cases, there is insignificant deposition and fuel retention.