DIII-D upper-divertor baffle optimization for pumping high-triangularity discharges

Magnetic equilibria with high divertor triangularity provide a potential path to stable high-beta discharges in DIII-D at higher pedestal density. Core plasma density control utilizing a cryo pump adjacent to the upper/outer divertor of DIII-D is a key component for this scenario.¹ The present study focuses on the impact of self-consistent plasma+neutral 2D profiles in the full scrape-off layer using UEDGE solutions with cross-field plasma drifts in a double-null magnetic geometry. The results provide local plasma fluxes for an analytic pumping-rate model benchmarked with Monte Carlo neutral simulations¹ and in turn, pumping is shown to modify the plasma. The highest pumping rates are obtained for the ion B´B drift directed away from the upper divertor region, which leads to a densification of the outer target. Optimization of the baffle and pump-duct locations and shapes are obtained via iteration between the plasma and pumping models.

¹ R. Wilcox et al., these proceedings.