Analysis of dynamics and spatial structure on the filament during type I ELMy H-mode using VUVI system on EAST

Abstract

In type I ELMy H-mode experiment, Edge localized mode (ELM) filaments are clearly captured by the high-speed vacuum ultraviolet imaging (VUVI) system which is developed on the Experimental Advanced Superconducting Tokamak. To analyze the ELM filament structures, the so-called singular value decomposition is performed on the imaging data to extract the key fluctuating components. In this work, the filament structure is characterized by the pitch angle and poloidal width. In a single ELM crash, it is found that the poloidal width increases (decreases) in the rise (decay) phase of the VUVI intensity induced by ELM crash. The pitch angle derived from the VUVI data agrees well with that calculated by the Equilibrium FITting code, indicating the filaments are aligned with the field lines. The poloidal velocity shows no obvious change during the rise and decay phases in an ELM crash. In addition, both the poloidal width and the poloidal velocity of the filament increase with the heating power. Since the filament structures are extracted from the line-integrated imaging data, all these results are obtained on the condition that the ELMs are confined to a narrow layer in the plasma.