Using the Super H-Mode as a Platform for Integrated Core-Edge Studies

DIII-D experiments assess compatibility of Super H-mode (SH) pedestals with up to 100% of injected power radiated dominantly in the divertor region using advanced feedback algorithms for density and radiated power control with impurity seeding. A current limited pedestal allows access to high density and low collisionality, providing high pedestal and separatrix density that produce a high pressure core plasma with a cold, dense divertor plasma. The SH regime maximizes physics parameters likely in future devices such as pedestal pressure, collisionality and separatrix density, providing a platform to study the impacts of a high-performance core on divertor conditions in present devices. Three optimization avenues for core edge integration have been developed: 1) Attached SH plasmas with high performance cores and pedestals (stored energy > 2MJ, pedestal normalized beta >1), but modestly cooled divertors (Te~15eV) represent a core-focused solution; 2) Nitrogen seeded partially detached plasmas with ~25% degradation to core performance represent a divertor-focused solution; 3) High recycling divertor at the onset of detachment with modest penalties (<5%) to core performance, 80% radiated power fraction, 30% reduced heat flux, and divertor temperatures ~5eV represent a path towards a balanced solution. At detachment onset, there is still plasma present at the strike point and in the scrape off layer, allowing most of the power to be radiated outside of the separatrix, maximizing confinement on closed flux surfaces and providing a target plasma for testing high heat flux scenarios on various divertor configurations. EPED predictions are consistent with experimental pedestal stability, and prospects for access to a stationary balanced core-edge solution are proposed for future experiments.