Comparison of divertor performance dependence on geometric configuration in DIII-D and MAST-U

A comparison between DIII-D and MAST-U has been initiated to examine divertor detachment performance dependence on divertor magnetic geometry, leg length, and baffle structure. The ultimate goal of this work is to determine the optimal divertor configuration for operating a detached divertor with complete heat flux dissipation, while maintaining a high temperature X-point for a high-performance core plasma. Initial work has included the successful control of the magnetic geometry for advanced divertor configurations in MAST-U, including strike-point and poloidal flux expansion control in the Super-X configuration. Modeling with the 2D fluid code SOLPS-ITER is examining detached divertor conditions in DIII-D and MAST-U with a long divertor leg and divertor baffling. Comparison of initial experimental results from DIII-D and MAST-U are presented. Primary differences for DIII-D higher magnetic field and power density, but with a vertical divertor leg compared to MAST-U's Super-X configuration. A focus of the initial studies is the poloidal electron temperature gradients in the divertor and its dependence on magnetic configuration, divertor baffling and power density. Results of this work are expected to guide future divertor design, including upgrades to the DIII-D divertor.