Gyrokinetic pedestal studies with varying plasma shaping in AUG

Abstract

The pedestal region in tokamak plasmas plays a critical role in determining overall confinement and performance, yet the interplay between turbulence and plasma shaping within this region is not fully understood. In this work, we present a comprehensive characterization of pedestal instabilities and their sensitivity to plasma shaping effects using the gyrokinetic code GENE. We consider a well documented H-mode discharge at two different time points where the plasma shaping is varied at constant (Formula presented) (Formula presented). Local linear simulations reveal microinstabilities present at all scales in both shaping cases. Global nonlinear simulations show a turbulence reduction with increased shaping, leading to an increased pedestal density in the high shaping case. At electron scales, the nature and impact on transport of these modes is assessed, confirming a significant amount of heat-flux driven at such scales while comparing with novel reduced models. Finally, the heat transport is compared with experimental fluxes across different transport channels with either correct order of magnitude or better agreement.