Gyrokinetic prediction of microstability and transport in NSTX H-mode pedestals

Gyrokinetic analysis (CGYRO) predicts that a variety of NSTX H-modes are within 10% of kinetic ballooning mode (KBM) stability thresholds across the entire pedestal. This is true from narrow ELMy to wide-pedestal ELM-free cases, indicating that KBM remains a viable candidate for constraining the maximum pressure gradient at low aspect ratio where EPED predictions have yet to be successfully validated. Other transport mechanisms are likely responsible for establishing profiles prior to their reaching KBM limits, as the ratio of experimental electron particle to thermal diffusivity is much smaller than that predicted for KBM. Microtearing mode (MTM) and trapped electron mode instabilities are also unstable across the pedestals, while the electron temperature gradient (ETG) instability is unstable in the outer half of the pedestals. Electron heat flux predicted from nonlinear ETG simulations approaches experimental values in some cases. An ETG pedestal transport model is presented, integrating similar results from conventional aspect ratio analysis. Nonlinear MTM simulations are progressing to determine how much transport they contribute. This work supported by the U.S. Department of Energy under DE-AC02-09CH11466, DE-FC02-04ER54698 and DE-AC02-05CH11231.