Investigating DIII-D H-mode pedestal microstability and transport with CGYRO

The spectral multiscale gyrokinetic code CGYRO is used to calculate theoretical microstability and transport in the edge region of DIII-D H-mode discharges. We focus on two discharges with different divertor geometries in an attempt to clarify the role of transport vs. particle source in setting the pedestal density and temperature profiles. Initial linear simulations predict that ion scale instabilities dominate at the top of the pedestal (ψ_N=0.9-0.96), where strong rotation shear enhances the growth rates and leads to significant changes in the predicted quasilinear fluxes. In contrast, in the steep gradient region (ψ_N=0.98), E×B shearing rates are much larger than ion scale instabilities. Instead, the electron temperature profiles appear to closely follow the electron scale ETG instability threshold. Nonlinear simulations are being pursued to predict the energy and particle fluxes in these regions for comparison to experimental analysis.