Transition from diffuse to constricted low current discharge in argon

Institute of Physics Belgrade, Pregrevica 118, POB 68, 11080 Zemun Belgrade, Yugoslavia

Corresponding author: is@plas.ruhr-uni-bochum.de

Received: 20 March 2000
Revised: 25 May 2000
Accepted: 25 May 2000
Published online: 15 July 2000

Abstract

We have measured the basic characteristics of low current diffuse discharges in argon for low pressures. The data for the voltage current characteristics and negative differential resistance were obtained together with the data for the frequency and for the damping coefficient of the induced oscillations. These data were compared with the predictions of a simple analytic model of Phelps, Petrović and Jelenković [A.V. Phelps, Z.Lj. Petrović and B.M. Jelenković, Phys. Rev. E 47, 2825 (1993)] and it was found that, while most observables may be represented correctly, there is a systematic discrepancy between the predictions for frequency of induced oscillations based on the data for transport coefficients from the literature and measurements. The basic idea of the present work is thus to check the fundamental assumptions of the theory and to extend the application of the experiment to study the transition to constrictions in order to initiate modifications of the theory to cover the transition to the constricted regime. Very good agreement was found between the spatial profiles of the electric field calculated from the model and the data obtained from the spatial profiles of emission and these data may be extended to follow the transition to the constricted regime and the development of the cathode sheath.