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2019_EJRNL_PP_M__E__AUSTIN_1.pdf
Terbatas Ratnasari
» ITB

Plasma discharges with a negative triangularity (? ¼ ?0.4) shape have been created in the DIII-D tokamak with a significant normalized beta (?N ¼ 2.7) and confinement characteristic of the high confinement mode (H98y2 ¼ 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 (? ¼ þ0.4) ELMing H-mode discharge with the same plasma current, elongation and cross sectional area. For cases both of dominant electron cyclotron heating with Te=Ti > 1 and dominant neutral beam injection heating with Te=Ti ¼ 1, turbulent fluctuations over radii 0.5 < ? < 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.