Investigation of pedestal stability in SPARC

The SPARC Primary Reference Discharge (PRD) is a proposed scenario capable of achieving performance exceeding the mission of Q > 2. Previous analysis has assessed the impact of varied pedestal pressure on core profiles [Rodriguez-Fernandez JPP 2020], as well as estimated pedestal pressure using EPED indicating a pedestal regime subject to peeling instabilities over a broad range of proposed operating densities [Hughes JPP 2020]. However, SPARC will require a set of staged scenarios leading up to the PRD as well as potential scenarios to be used in lieu of the PRD if certain SPARC parameters cannot be met [Creely APS DPP 2020].

Pedestal stability is investigated using the ELITE code for several SPARC scenarios of interest, including 1) Primary reference discharge (PRD), 2) Full field reduced confinement H-mode (H07), 3) Full field high density (HIDEN), and 4) 8T H-mode (8T). Dominantly unstable toroidal mode numbers and growth rates are calculated along with peeling-ballooning eigenmode structures spanning the pedestal region. Potential profiles for each scenario are presented along with self-consistent plasma equilibria. Additionally, sensitivity of growth rates to Alfven normalization as well as ion diamagnetic stabilization for several variations in pedestal profiles is explored