Stability and Transport of Gyrokinetic Critical Pedestals

A gyrokinetic threshold model for pedestal width-height scaling prediction is applied to multiple devices and to a shaping and aspect-ratio scan giving Δ_ped = 0.92 A^1.04κ^-1.24 0.38^δβ_θ,ped^1.05 for pedestal width Δ_ped, aspect-ratio A, elongation κ, triangularity δ, and normalized pedestal height β_θ,ped. We also find a width-transport scaling Δ_ped = 0.028 (q_e/Γ_e - 1.7 )^1.5∼η_e ^1.5 where q_e and Γ_e are turbulent electron heat and particle fluxes and η_e = ∇ln T_e / ∇ln n_e for electron temperature T_e and density n_e. Pedestals close to those limited by kinetic-ballooning-modes (KBMs) have modified turbulent transport properties compared to strongly driven KBMs. The role of flow shear is studied as a width-height scaling constraint and pedestal saturation mechanism for a standard and wide pedestal discharge.