Self-organization of surface wave sustained discharges in the pressure range from 10 to 200 Torr

Abstract

Experiments showing the dynamics in the self-organization of surface wave sustained discharges are presented. Microwave (2.4 GHz) discharges maintained in an argon gas in a continuous wave regime at a constant applied power and varying gas pressure are studied. The evolution of the discharge from a stationary plasma column at comparatively low pressure (p⩽10 Torr) to a plasma torch at atmospheric pressure passes through different stages of self-organization of the wave-field↔plasma nonlinear structure showing evidence of the general trends of behavior of nonequilibrium dissipative systems. The measurements are carried out at the stage of the discharge self-organization into a filamentary structure with an azimuthal rotation. Macroscopic characteristics (number, size, velocity of rotation) of the filaments and their dependence on the gas pressure and its time variation are given. The total light emission of the plasma considered as giving information about the plasma density is measured and different methods of signal processing (including correlation-spectrum analysis) are applied. Oscillations of the filament ends are also observed. The different types of interrelation between plasma density and field intensity, registrated in the different pressure ranges, call for variety in the instability mechanisms. Although the scenario of the discharge self-organization is stressed in the discussions, the observations are important with their relation to the discharge applications, which require avoiding conditions of development of instabilities.