Experimental Analysis of a Low Frequency Instability in a Magnetized Discharge Plasma

Abstract

Abstract In the paper we present the results of an investigation of a low frequency (30‐100 kHz) instability in a weakly magnetized discharge plasma. The instability is triggered by a disc electrode which terminates the magnetized plasma column and is biased above the plasma potential. Frequency dependence on various parameters, e.g. electrode diameter, electrode bias, neutral gas pressure and plasma density is measured. Space and time dependence of the plasma potential and density in the perturbed region during one period of the electrode current oscillation are measured. During the phase of the current decrease a potential structure moves in axial direction from the edge of the perturbed region towards the electrode. During the phase of current saturation the motion of ions is mostly radial. The observed phenomenon is approximately modeled as a two dimensional potential relaxation instability (PRI).