Studies of radial electric field formation and its effect on fluctuations and transport barriers in the JFT-2M tokamak
JFT-2Mにおける径電場形成がプラズマ揺動と輸送障壁形成に及ぼす影響に関する研究
居田 克巳*; 三浦 幸俊; 井戸 毅*; 永島 芳彦*; 篠原 孝司
Ida, Katsumi*; Miura, Yukitoshi; Ido, Takeshi*; Nagashima, Yoshihiko*; Shinohara, Koji
改善閉じ込めの物理は、プラズマ中に形成される勾配を持つ径方向電場と磁場によるEB流が揺動のポテンシャルを分断することにより起こると考えられている。プラズマ境界の閉じ込めが改善されるH-mode及びプラズマコアの閉じ込めが改善される場合の電場形成のメカニズムと観測されたプラズマ揺動についてレビューするとともに、ゾンナル流の一種でありシア流が形成されるGeodesic Acoustic Modeとプラズマ揺動との関係解明に関するJFT-2Mでの実験結果をレビューした。
The mechanism of EB flow formation, the effect of EB flow on parallel flow, the reduction of fluctuation by the shearing effect of EB flow, the relation between GAM and density fluctuation are discussed based on the experiments using various Er measurements on JFT-2. The experiments in the plasma with H-mode and counter-NB mode shows that the feedback loop of the EB flow shear, fluctuation suppression and an increase of ion diamagnetic flow is a key of the formation of the transport barrier in toroidal plasmas. Two important effects of radial electric field are presented, one is fluctuation suppression by EB flow shear and the other is a drive of parallel flow by radial electric field, which explain a driving mechanism of a spontaneous toroidal flow. The relation between GAM and density fluctuation is also discussed. The GAM is observed to be excited by the non-linear coupling of density fluctuations, while GAM itself affects the amplitude of density fluctuation.