Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Abstract

A dedicated series of ELMing H-mode discharges on Alcator C-Mod spanning a broad range of plasma parameters, including plasma current (400–1000 kA), magnetic field (3.5–8 T), and plasma shaping, are presented with experimental scalings of the plasma pedestal with bulk plasma and engineering parameters. The H-modes presented achieve pedestals with densities spanning 5 × 10¹⁹–2.5 × 10²⁰ m⁻³ and temperatures of 150–1000 eV (corresponding to 5–40 kPa in the pressure pedestal), over a width of 3–5% of poloidal flux. The observed pedestal structure is compared with the most recent iteration of the EPED class of models, which uniquely predict the pedestal width and height for a set of scalar input parameters via a combination of stability calculations for peeling–ballooning MHD modes and kinetic-ballooning modes.