Characteristic Features of Edge Localized Mode under the Presence of Edge Ergodic Magnetic Field Layer in LHD

Abstract

Existence of the ergodic magnetic field layer surrounding the core plasma argues one of typical characters in Large Helical Device (LHD). A new type of H-mode-like discharges have been obtained at an outwardly shifted configuration of R_ax=4.00m with extremely thick ergodic layer, where the iota/2pi=1 position is located in the middle of the ergodic layer. These H-mode-like discharges can be triggered by changing P_NBI (<12MW) from 3 beams to 2 beams in a density range of 4-8x10^13 cm^-3, although the spontaneous transition is also observed. ELM-like bursts appeared with a radial propagation of density bursts are occurred at the iota/2pi =1position and are mainly excited at the inboard side of the torus. The frequency of the ELM-like bursts increases with heating power, at which the edge pressure profile is steeper. ELM-like bursts in LHD are briefly interpreted