Measurement of fluctuation induced particle flux by microwave imaging reflectometry in KSTAR plasma

Abstract

This paper presents a spectral analysis technique [1, 2] to measure the frequency spectrum of particle flux induced by fluctuations across confining magnetic fields using microwave imaging reflectometry (MIR) diagnostic [3, 4] in toroidal devices. In this method density fluctuations measured by two correlated MIR radial channels are used to calculate radial particle flux spectrum over a finite frequency range. Analysis shows that during n=2 (with 0 phasing) non-axisymmetric magnetic perturbation (MP) the particle flux in the outward direction enhances and energy confinement degrades in a neutral beam heated Lmode discharge. Degradation of particle confinement is confirmed by reduction in line averaged density and stored energy signals during MP field application. Confinement regains its value due to decrease in the outward particle flux after the MP field is switched off.