Bifurcation of Perpendicular Rotation and Field Penetration at the Transition to RMP-Induced ELM-Crash Suppression

Full text: The bifurcation of perpendicular rotation (ν_⊥) at the transition of ELM-crash suppression has been measured using electron cyclotron emission imaging (ECEI) system on KSTAR. The ECEI revealed that the ELM crashes are suppressed along with a rapid reduction of ν_⊥, which synchronizes with the transition into and out of the ELM-crash suppression. The ν_⊥ bifurcation is mainly attributed to the rapid change of E x B velocity and the ν_⊥ magnitude is maintained the smallest near the q₉₅ rational flux surface during the ELM crash suppression. The plasma response to the RMP, normalized by ν_⊥ changes, is strongest in the vicinity of q₉₅ rational flux surface during the ELM-crash suppression. (author)