This study employs electron-scale gyrokinetic simulations to investigate the electron temperature gradient (ETG) driven instabilities, turbulence, and transport in the pedestal region of the National Spherical Torus Experiment, comparing non-lithiated (narrow pedestal) and lithiated (wide pedestal) scenarios. Our findings reveal that, in the non-lithiated case, a branch of strongly unstable ETG modes exhibiting finite parallel magnetic field fluctuations () emerges at the pedestal top and upper density pedestal region. This branch is uncovered only when is retained in the simulations and is associated with substantial electrostatic electron heat flux. This region of strong ETG transport corresponds to the only region in the plasma where the pressure gradient is far below the critical gradient for kinetic ballooning modes. We investigated the origin of this finite ETG branch by analyzing the gyrokinetic field equations. Nonlinear saturation is also analyzed and contrasted for simulations with and without . In contrast with the nonlithiated case, ETG modes in the lithiated case produce substantial transport in the steep gradient region, but are negligible at the pedestal top.
This study investigates how magnetic field fluctuations () affect electron temperature gradient (ETG) instabilities, turbulence, and heat transport in the pedestal region of the National Spherical Torus Experiment (NSTX). The findings show that including reveals a strongly unstable ETG mode branch at the pedestal top, leading to significant electron heat flux. This is in contrast with the lithiated case, where ETG modes have a smaller impact on transport.