Negative Differential Resistance, Oscillations and Constrictions of Low Pressure, Low Current Discharges

Abstract

A brief review is given of the recent experimental and theoretical studies of low current diffuse discharges. Two models are developed, one that is based on phenomenological description by effective discharge circuit parameters and the other which is based on the calculation of the field profile from the ion distribution for uniform field. In the first case the physical process responsible for the development of the negative differential resistance is the dependence of the secondary electron yield on current through modification of the field close to the cathode. Experimental systems were developed to provide observables that include: breakdown voltage, voltampere characteristics (which in the low current limit is represented very well by a negative differential resistance), limits and the profile of the low current oscillations, frequency and damping of the induced oscillations, current growth coefficient and the onsets for constrictions. All of the observables are very well predicted by the theory based on the data taken from independent sources, once the steady state secondary electron yield has been fitted to predict the breakdown voltage.