Role of ion mass in the generation of fluctuations and poloidal flows in a simple toroidal plasma

Abstract

Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma, at a given magnetic field strength for varying ion masses. Under similar discharge conditions, the fluctuation induced poloidal flux is found to decrease with increasing ion mass. Consequently, the absolute net poloidal flow velocity is found to scale down systematically with increase in the ion mass. The net poloidal flow in units of ion acoustic velocity is, however, comparable for all masses on the low field side and shows minor variations on the high field side. The frequency of the first harmonic in the density and potential power spectra is found to decrease with decreasing absolute net flow. A transition occurs in the fluctuation behavior from highly coherent state to a turbulent state with increase in the ion mass, from argon to xenon.