A dissipative small-angle slot divertor for DIII-D high triangularity and low radius plasmas

A numerical assessment using SOLPS-ITER is presented of a new dissipative divertor for DIII-D high triangularity and low radius plasmas in the upper single-null configuration, with and without drifts. Sequential modifications to the DIII-D upper divertor are planned to explore a series of missions. Initially, the divertor will remain short to maximize the plasma volume for advanced tokamak scenarios. Later, it will be replaced by a dissipative divertor for power exhaust optimization. This contribution discusses a design for the second phase. To minimize divertor leakage of neutrals and impurities, the proposed design features tight wall baffling on both the private and common flux sides. Several slot shaping options are explored to minimize electron temperature, and thus erosion, across a large fraction of the SOL. These include a symmetric V-target (as in the SAS-V divertor now installed on DIII-D) and a progressive increase of the SOL target angle (as in the SAS divertor, formerly installed). To characterize the transition to divertor detachment, modeling is performed for a range of plasma densities and input powers, using in-slot pumping for particle control.