Detached divertor operation in DIII-D's new compact Shape and Volume Rise divertor

Experiments on the DIII-D tokamak achieved detached divertor conditions in the new compact Shape and Volume Rise (SVR) divertor by increasing deuterium fueling (plasma density) or extrinsic nitrogen seeding, across a range of operational scenarios with concurrent modeling. Variables explored include toroidal field direction, fueling location (main chamber vs private flux region), and heating strategy (stationary vs. ramped power to mitigate pedestal degradation). The resulting dataset is used to (1) assess detachment effects on pedestal and core plasma performance, (2) identify strategies to better integrate cold, detached divertor conditions with high-performance pedestals in shallow divertor geometries like the SVR, and (3) validate edge modeling codes such as SOLPS-ITER, enhancing their predictive power for divertor design in future tokamaks. The DIII-D program is testing a compact divertor geometry designed for high-performance pedestal operation. This geometry enables larger core plasma volumes, higher plasma currents, and thus higher absolute divertor densities and pressures, approaching the values expected in FPPs. However, its reduced divertor volume also brings the X-point closer to the divertor targets, raising the risk of unacceptable core degradation during detachment. This study presents preliminary results from dedicated DIII-D experiments, supported by SOLPS-ITER simulations.