Enhanced Pedestal Pressure and Parameter-Linkages Determining Edge Pedestal Structure in JT-60U Type I and Type II ELMy H-mode
Y. Kamada 1), H. Takenaga 1), H. Urano 2), T. Takizuka 1), T. Hatae 1) ,Y. Miura 1)
1) Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Ibaraki-ken, Japan
2) Max-Planck-Institut fur Plasmaphysik, Garching, Germany
Abstract.
Based on the expanded H-mode operational regimes in JT-60U utilizing the improved capability of high triangularity (δ) operation, the multiple pellet injection and high power heating including the negative ion based NB (NNB), we have clarified the pedestal parameter-linkages determining the pedestal structure (i.e. 'The pedestal width' increases with ρpi and does not depend on βp-ped . 'The normalized pressure gradient α' is almost constant at low δ, while α ∝ βp at high δ). Based on these results, we have enhanced the pedestal pressure of the ELMy H-mode by factors of 2-2.5 at the same plasma current and plasma shape, and extended the high confinement regime to a high density. We have found that the pedestal stored energy Wped increases with the core energy (or βp-core) at high &δ (>0.3-0.4), while Wped is low and almost constant independent of, for example, heating power at low δ (<0.2). In addition, we have expanded the type II (grassy) ELMy high confinement regime with a small heat load on to divertor plates to the low-q (q95<4) regime, and demonstrated successful compatibility of the type II ELMs with the pellet injection. Based on a variety of JT-60U experiments, possible linkages among the pedestal and the core parameters has been proposed.