Two-Dimensional Visualization of Growth and Burst of the Edge-Localized Filaments in KSTAR H-Mode Plasmas

The filamentary nature and dynamics of edge-localized modes (ELMs) in the KSTAR high-confinement mode plasmas have been visualized in 2D via electron cyclotron emission imaging. The ELM filaments rotating with a net poloidal velocity are observed to evolve in three distinctive stages: initial linear growth, interim quasisteady state, and final crash. The crash is initiated by a narrow fingerlike perturbation growing radially from a poloidally elongated filament. The filament bursts through this finger, leading to fast and collective heat convection from the edge region into the scrape-off layer, i.e., ELM crash.