Turbulence induced particle flux measurements by microwave imaging reflectometry

Abstract

In this paper we present a spectral analysis method [1] to measure the frequency spectrum of particle flux induced by fluctuations across confining magnetic fields using microwave imaging reflectometry (MIR) diagnostic [2, 3] in toroidal devices. In this technique 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 discharge. Degradation of particle confinement is confirmed by reduction in line averaged density and stored energy signals. Confinement regains its value due to decrease in the outward particle flux after the MP field is switched off.