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(EX/P2-05) Observation of High Recycling Steady H-mode Edge and Compatibility with Improved Core Confinement Mode on JFT-2M

K. Kamiya¹⁾, H. Kimura¹⁾, H. Ogawa¹⁾, H. Kawashima¹⁾, K. Tsuzuki¹⁾, M. Sato¹⁾, Y. Miura^1)
 
1) Japan Atomic Energy Reseach Institute, Ibaraki-ken, Japan

Abstract.  A new operational regime has been discovered on JFT-2M under the boronized first wall condition to produce High Recycling Steady (HRS) H-mode, which is characterized by good energy confinement (H89Psim1.6) at high density around 70% of the Greenwald density, low radiation power fraction, and the complete disappearance of large (Giant) ELMs. Accompanying the HRS H-mode, a coherent magnetic fluctuation is observed at around 50-150 kHz, whose characteristics are similar to the Enhanced D-alpha (EDA) H-mode reported from Alcator C-Mod. The H'-mode, previously observed on JFT-2M, had common feaures with EDA-mode in terms of the coherent density fluctuation, but it appeared transiently. The HRS operating regime is also similar to EDA-mode, except that HRS is seen even at low q95 (2<q95<3). The most important feature of the HRS H-mode edge condition is the compatibility with an improved core confinement mode at high density without large ELMs. We have demonstrated that an internal transport barrier (ITB) can be produced with the HRS H-mode edge condition, achieving beta-NxH89P 6.2 at the Greenwald density 70%, transiently.

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