Investigation of pedestal parameters and divertor heat fluxes in small ELM regimes on DIII-D

Small ELM regimes offer a potential solution for core-edge integration as a means to avoid high transient heat loads from type-I ELMs, without large reduction in plasma performance and stored energy. An important physics question to answer remains, how these currently observed small ELM regimes scale to a future fusion reactor. An investigation into the divertor heat flux and its dependencies on pedestal parameters has been performed on DIII-D. DIII-D's flexible plasma-shaping and pressure control provide the capability to study a wide-range of naturally occurring small ELM regimes including high beta poloidal, type-II/grassy, and ELMs in negative triangularity H-modes. Using high-time resolution infrared thermography, the parallel heat flux and total heat loads to the divertor are determined and compared to the observed losses in stored energy. Additionally, the pedestal parameters are obtained from the self-consistent kinetic equilibrium reconstructions using the profile measurements conditionally averaged over the ELM cycle. The pedestal parameters are presented as a function of normalized ELM energy loss across the various small ELM regimes and compared to the type-I ELM energy density scalings.