Effect of edge turbulence on ELM-crash-suppression under n=1 RMP

Abstract

The effect of n = 1 RMP on the edge-localized mode (ELM) and edge turbulence has been investigated by using electron cyclotron emission imaging (ECEI) system [1] in the KSTAR. The ECEI revealed that the filamentary structure of ELM is maintained with substantial fluctuation in amplitude without large scale collapse. Correlation analysis showed that the RMP enhances turbulent fluctuations in the edge toward the ELM-crashsuppression phase. The spectral power distribution of the turbulence has been obtained showing a linear dispersion for wide ranges of wavenumber (kθ < 1 cm−1) and frequency (< 70 kHz). Velocimetry analysis [2] confirmed that the potential and density fluctuations of turbulent eddies are approximately out of phase and thus the turbulence involves a net radial transport. Bispectral analysis [3] clearly shows that the coexisting ELM and edge turbulence nonlinearly interact each other.