Observation of high recycling steady H-mode edge and compatibility with improved core confinement mode on JFT-2M

A new operational regime has been discovered on JFT-2M under the boronized first wall condition to produce the high recycling steady H-mode edge, whose characteristics and operational regime are similar to EDA-mode reported from Alcator C-mod. The H-mode, previously observed on JFT-2M, had common features with EDA-mode in terms of the coherent density fluctuation, but it appeared transiently. The most important feature of the high recycling steady H-mode edge condition is the compatibility with an improved core confinement mode at high density without giant ELMs. An improved core confinement with the high recycling steady H-mode edge condition is sustained for about 5 global energy confinement times with H89P confinement enhancement factors of 1.5 at the line averaged electron density around 70%-80% of the Greenwald density limit. (author)