SOLPS modeling of neutral fueling effects on pedestal structure in DIII-D

Neutral fueling location was varied in a series of DIII-D discharges by comparing plasmas fueled with: 1) core NBI only, 2) core NBI + deuterium pellet injection, 3) minimal NBI + ECH + external gas puff and 4) minimal NBI + ECH. The discharges with core fueling show increased pedestal density and an increase of over 30% in the ratio of the pedestal to separatrix density. Initial interpretive SOLPS modeling of these experimental results shows that for discharges, which are otherwise similar except for the fueling location, very similar anomalous diffusion profiles are required to match the experimental values when modeled with no pellets or gas puff, and drift and pinch effects are off. Pellet fueling is modeled as a constant neutral source in the pedestal region where pellet ablation is observed. The addition of a fueling source in the pedestal due to pellet injection requires a significant change in the anomalous diffusion to match the experimental density profile from the recycling only fueled case. SOLPS-ITER will be used to determine the relative importance of drifts as well as anomalous diffusion and pinch effects on the particle transport in the pedestal.