Identification of MHD Mode Structure using ECE and SX Measurements

Abstract

This study reports characteristics of the interchange mode-like magnetohydrodynamic (MHD) mode through comparisons between fluctuations measured by electron cyclotron emission (ECE) and Soft X-ray (SX) in the Large Helical Device (LHD). The MHD mode, whose frequency is 0.74 to 2.7 kHz, is enhanced near ρ = 0.8, ι = 1. T_e fluctuation data measured by ECE can identify the mode width by using the displacement amplitude profile whereas SX data cannot show the structure clearly. Furthermore the dependence of the width and amplitude on the pressure gradient is shown using T_e fluctuations.