Study of edge turbulence through correlation analysis of 2-D ECEI channels in the KSTAR

Abstract

The measurement of a long wavelength (kyρs ∼ 0.1) edge turbulence has been carried out using correlation study of the 2-D electron cyclotron emission imaging (ECEI) [1] data in KSTAR. The correlation technique provides a clear response to poloidal wavenumber in the range of < 1cm−1 and average group velocity of ∼ 3 km/s with the electron diamagnetic direction during the ELM crash suppressed phase. Besides, the radial and poloidal size of turbulenct eddies are small compared to typical ELM flux tube and the parallel wavenumber of turbulence is in the range of 0.67 < kk < 6 m−1. It is also applied to both L- and H-mode to compare the turbulence properties and the result shows that the turbulence features of the ELM crash suppression is similar to those of L-mode. In addition, the velocimetry technique [2] has been applied to ECE imaging data to yield time dependent 2-D velocity field of Te turbulence at the plasma edge in the ELM crash suppression phase.