Studies of radial electric field formation and its effect on fluctuations and transport barriers in the JFT-2M tokamak

Ida, Katsumi*; Miura, Yukitoshi; Ido, Takeshi*; Nagashima, Yoshihiko*; Shinohara, Koji

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.