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 GHz͒ 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 (pр10 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 rotation͒ 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 analysis͒ 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.

Travelling-wave-sustained discharges

“…[39][40][41][42][43][44][45][46]) which motivate aspects of the reported modelling are also pointed out in the review.…”

“…The self-organization of TWSDs with increasing gas pressure has been experimentally observed in microwave discharges (at f = 2.45 GHz) produced in SW fields in argon gas [13,41]. The discharge is sustained-by azimuthally symmetric SWs-at a constant power P (with values P = 40 -150 W) applied in a cw regime.…”

“…Such a behaviour results from the increase of the losses with the pressure increase: the increased losses do not permit-at a constant power applied for the discharge maintenance-plasma production in a large volume. The filamentation of TWSDs was first observed in experiments [41] with varying gas pressure in an argon discharge maintained in a cw regime. Starting from a stage of a stationary plasma column at low gas pressure, the discharge evolution-with the gas-pressure increase-passes through different stages of self-organization of the field↔plasma nonlinear structure showing evidence of general trends of behaviour of non-equilibrium dissipative systems [332].…”

“…For a given dp/dt it decreases with increasing p. Increasing dp/dt causes an increase of the velocity of 95. Axial variation of the end of a filament (signal from a photomultiplier); P = 140 W, dp/dt = 1 Torr/s (from [41]). rotation as well as narrowing of the pressure range of regular rotation of the structure and its shift towards lower p-values.…”

Interaction of current filaments in dielectric barrier discharges with relation to surface charge distributions

“…Self-organized structures appear in numerous gases and in a wide parameter range. They become investigated in low frequency devices as well as in radio frequency discharges [1,4]. Besides the pattern formation itself, their temporal dynamic has been investigated in the past [6,10,11,13].…”