Paleoclassical Model for Edge Te Pedestal

A model is proposed for the edge electron temperature profile T_e(ρ) in high (H) confinement mode, diverted tokamak plasmas based on the paleoclassical model [1] for the minimum possible radial electron heat transport. In the paleoclassical model as one moves inward from the separatrix the electron heat diffusivity first decreases (until λ_e∼πRq); then it increases moving further inward into the paleoclassical collisional (Alcator-scaling) regime. The T_e profile predictions from the paleoclassical model as one moves inward from the separatrix are: 1) first an increasing T_e gradient with η_e≡dT_e/dn_e=2, 2) a maximum |∇T_e| where q drops to ∼ 5--7, 3) then a decreasing T_e gradient, and 4) finally a pedestal electron pressure determined by balancing collisional paleoclassical transport against gyro-Bohm-scaled anomalous electron heat transport, β_e^p ≡n_e^p T_e^p / (B^2/2μ₀) a/Rq, which implies p_e^p ≡n_e^p T_e^p B_pB_t. The relatively favorable omparisons of these paleoclassical model predictions with DIII-D experimental data on H-mode T_e pedestals just before an ELM will be shown. 0.5ex[1] J.D. Callen, Phys. Plasmas 12, 092512 (2005).