Interpretive Modeling of Pumping Experiments in DIII-D and Comparisons to Measurements using SOLPS-ITER

Using SOLPS-ITER to model H-mode experiments in the closed upper divertor of the DIII-D tokamak, downstream plasma conditions are found to be critically dependent on neutral pathways, including particle sources and sinks. Upstream plasma profiles are matched to Thomson scattering and charge exchange measurements by iteratively modifying the radial transport coefficients, while core particle and energy source rates are taken from the experiment. Resulting downstream plasma profiles generally do not match those measured using Langmuir probes without modification of core particle flux from experimental values. Cross-field drifts are not yet included in the calculations, but adding them would be expected to push the modeled results in the direction of the measurements in attached conditions. When downstream plasma conditions are matched to experiment, modeled divertor neutral pressures compare more favorably with pressure gauge measurements.