Role of Transport and MHD Stability in Simulations of H-mode Pedestal Development in ELMy Plasmas

This study addresses the development of a scaling of the H-mode pedestal in tokamak plasmas with type I ELMs. In particular, the scaling studies carried out illustrate the dependence of the pedestal properties and the resulting divertor heat load width as a function of plasma elongation and plasma current. H-mode pedestal profiles for DIII-D and Alcator C-Mod tokamaks are considered: DIII-D for low B-field, low-density, high temperature plasmas; and Alcator C-Mod for a high B-field, high-density plasmas. The simulations in this study use realistic diverted geometry and are self-consistent with the inclusion of kinetic neoclassical physics, theorybased anomalous transport models with the E B flow shearing effects, as well as an MHD ELM triggering criterion. Scalings for the pedestal width and height are developed as a function of the scanned plasma parameters. Differences in the electron and ion temperature pedestal scaling are investigated. The neoclassical divertor heat load fluxes are computed with the XGC0 code and a relation for the dependence of the divertor heat load width on the plasma current is derived. In the development of this relationship, effects of neutral collisions and anomalous transport are taken into account. Changes in the neoclassical divertor heat load fluxes associated with the introduction of the neutral collision and anomalous transport effects are described.