Pedestal behavior in DIII-D negative triangularity discharges*

In DIII-D negative triangularity L-mode-edge discharges the pedestal region exhibits I-mode-like features; the T_e profiles have an elevated pedestal height similar to H-mode while the n_e profile is nearly the same as typical L-mode.  In matched negative (NT) and positive triangularity (PT) L-mode plasmas with the same B_T, I_p, and cross-sectional area, the T_e pedestal at ρ=0.95 is 50% higher in NT over PT, and the NT T_e gradient for 0.7 < ρ < 0.9 is 20% higher than the PT one. The resulting increase in electron pedestal pressure contributes to the higher stored energy in the NT compared to the PT discharges. Ion temperatures near ρ ~ 0.95 in the two cases appear to be about the same. No weakly coherent mode, as seen on C-MOD I-modes, has been detected in DIII-D NT discharges. In recent experiments in a lower diverted shape with upper negative triangularity a rapidly ELMing H-mode is obtained at relaxed delta (δ_upper = -0.2), and the pedestal height increases 60% compared to the stronger shaped (δ_upper = -0.4) case in L-mode.  However, the global confinement remains the same in both cases, with H_98(y2) = 1, indicating decreased core transport in the H-mode with relaxed negative triangularity. We explore the causes of this behavior.