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

The 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.