Direct Evaluation of Spatio-Temporal Change in Current Density Profile Applied to a Discharge with Neo-Classical Tearing Mode

Abstract

An analytical method to evaluate spatio-temporal change in the current density profile directly from the motional Stark effect (MSE) diagnostic is applied to a discharge, where a neo-classical tearing mode (NTM) appeared and was stabilized by electron cyclotron current drive (ECCD). The analysis clearly shows a spatially localized decrease in current density at the magnetic island location, implying a decrease in bootstrap current due to a flattening of the pressure profile within the island. When the NTM is stabilized after the start of the ECCD application, an increase in current density at the island location is observed.