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Plasma discharges with a negative triangularity (δ=-0. 4) shape have been created in the DIII-D tokamak with a significant normalized beta (β₍=2. 7) and confinement characteristic of the high confinement mode (H₉₈ₘ₂=1. 2) despite the absence of an edge pressure pedestal and no edge localized modes (ELMs). These inner-wall-limited plasmas have a similar global performance as a positive triangularity (δ=+0. 4) ELMing H-mode discharge with the same plasma current, elongation and cross sectional area. For cases both of dominant electron cyclotron heating with T₄/T₈>1 and dominant neutral beam injection heating with T₄/T₈=1, turbulent fluctuations over radii 0. 5<ρ<0. 9 were reduced by 10-50% in the negative triangularity shape compared to the matching positive triangularity shape, depending on the radius and conditions.
Austin et al. (Mon,) studied this question.