Comparisons of small ELM H-Mode regimes on the Alcator C-Mod and JFT-2M tokamaks

Comparisons of H-mode regimes were carried out on the Alcator C-Mod and JFT-2M tokamaks.Shapes were matched apart from aspect ratio, which is lower on C-Mod.The High Recycling Steady (HRS) H-mode on JFT-2M and Enhanced D α (EDA) regime on C-Mod, which both feature very small or no ELMs, are found to have similar access conditions in q 95 -ν* space, occurring for pedestal collisionality ν* > 1. Differences in edge fluctuations were found, with lower frequencies but higher mode numbers on C-Mod.In both tokamaks an attractive regime with small ELMs on top of an enhanced D α baseline was obtained at moderate ν* and higher pressure.The JFT-2M shape favoured the appearance of ELMs on C-Mod, and also resulted in the appearance of a lower frequency component of the quasicoherent mode during EDA.