Investigation of Sheath Phenomena in Electronegative Glow Discharges
Abstract
Two different methods of analyzing the cathode fall region of low pressure glow discharges were developed and applied to three different electronegative gas mixtures. One method was based on a selfconsistent numerical solution to Poisson's equation, the current continuity equations for electrons and negative ions, and the current conservation equation. This method assumes the electrons are always in equilibrium with the electric field. The other method was based on a selfconsistent numerical solution of the Boltzmann transport equation for electrons, Poisson's equation, and the current conservation equation. This method allows the electrons not to be in equilibrium with the field. Comparing these two methods revealed that nonequilibrium prevails throughout the cathode fall region. The electronegative gas mixtures investigated were small concentrations (less than 10%) of hydrogen chloride in helium, argon, or xenon. The electric field, Townsend ionization and attachment coefficients, electron and negative ion current densities, and electron, positive ion, and negative ion number densities are plotted as functions of distance through the cathode fall region. Discharge current densities, cathode fall lengths, and voltages are compared to other theoretical and experimental data through a scaling relationship. The experimentally observed contraction of the cathode fall length in electronegative gases with helium as a buffer is described and not predicted for argon or xenon mixtures. Other regions such as the negative glow and anode fall are also briefly discussed.
 Publication:

Ph.D. Thesis
 Pub Date:
 1983
 Bibcode:
 1983PhDT........13D
 Keywords:

 CATHODE FALL;
 ELECTRON KINETICS;
 Physics: Fluid and Plasma;
 Gas Mixtures;
 Glow Discharges;
 Plasma Sheaths;
 Anions;
 Argon;
 Boltzmann Transport Equation;
 Cathodes;
 Cations;
 Current Density;
 Electric Fields;
 Electrons;
 Equilibrium;
 Helium;
 Hydrogen Chlorides;
 Ionization Coefficients;
 Low Pressure;
 Poisson Equation;
 Reaction Kinetics;
 Xenon;
 Physics (General)