Constricted Discharges in the Rare Gases. II. Analysis of the Macroscopic Properties of the Discharge

Abstract

Articles you may be interested inThe constricted glow discharge: A stationary source of vacuum-UV raregas excimer continua Rev. Sci. Instrum. 59, 565 (1988); 10.1063/1.1139834 Current density for cold cathode discharge gap in rare gasesThe macroscopic properties of the rare gas constricted discharges are discussed. For the rf excited discharge an equivalent circuit for the electrode coupling has been found, comprising a capacitor with the electrode and plasma forming the plates and the discharge tube wall the dielectric. An explanation for the observed striations is advanced, based upon the existence of voltage standing waves at the plasma resonance frequency. A numerical analysis based on an energy balance indicates that these discharges should have a finite radius, in this case smaller than the discharge tube radius. It is necessary to require that the electron energy distribution be Maxwellian near the center of the discharge and that deviation from this energy distribution causes the sharp boundary observed for the heavier rare gases. For the microwave discharge it is pointed out that it is necessary to include the electromagnetic field equations in the analysis and that this requirement naturally leads to a maximum radius for a single discharge channel which is much smaller than for the rf-excited case. This, in turn leads to an explanation of the multicolumn effect observed.

Propagation of a Surface Wave Sustaining a Plasma Column at Atmospheric Pressure

“…The diameter a t which the initial filament breaks into two or more smaller filaments is connected with the skin effect [22]: the higher the field frequency, the thinner the filaments observed: for example, a t 10 GHz, with 300 watts, using a surfaguide launcher…”

“…The dominant factor has to be the fact that the gas temperature is much higher in the plasma region than outside it creating a radial heat flow toward the tube wall. This leads to a constriction effect [22]. Under such conditions, the plasma diameter will depend on the neutral gas pressure, and on its temperature along the radius.…”

“…These considerations show that the constriction is connected with both thermal processes [22, 301 and skin effect. The latter determines the maximum plasma diameter that can be obtained a t a given frequency [22].…”

A Critical Review of Published Data on the Gas Temperature and the Electron Density in the Electrolyte Cathode Atmospheric Glow Discharges

“…The evaluation of the available data was based on the following three conditions: In order to offer an accurate method for the determination of T G , the gas composition of the ELCAD plasma was studied. Since the ELCAD is an atmospheric glow discharge, hence for T G and T e electron temperature, T G = T e [ 22 , 23 ] or T e ≈ T G [ 24 – 26 ] can be expected. If T e is also measured, T e = T G or T e ≈ T G relation can be used for the mutual validation of the received values.…”

“…If T e is also measured, T e = T G or T e ≈ T G relation can be used for the mutual validation of the received values. As a consequence of the T e = T G (or T e ≈ T G ) relation referring to an local thermodynamic equilibrium (LTE) [ 22 , 23 ] (or a good approximation of it [ 24 – 26 ]), the corresponding values of T G and n e can be calculated from the Engel-Brown approximation [ 8 , 10 ] of the Saha-equation [ 27 , 28 ] related to the weakly ionized glow discharges with low charge densities. …”