Direct-current glow discharges in atmospheric pressure air and nitrogen plasmas

Abstract

Summary form only given. There is considerable interest in methods for efficiently producing large volumes of atmospheric pressure air plasmas at gas temperatures below 2000 K with free electron densities of 10/sup 13/ cm/sup -3/. One approach consists in targeting the energy addition to the free electrons by application of electric fields. Investigations have been conducted to understand and validate the mechanisms of ionization in two-temperature atmospheric pressure air and nitrogen plasmas in which the electron temperature is elevated with respect to the gas temperature. With a new two-temperature chemical kinetic model for air and nitrogen plasmas, we found that, for a given gas temperature, the steady state electron number density exhibits an S-shaped dependence on the electron temperature. This S-shaped behavior is the result of competition between ionization and charge transfer reactions and is characteristic of molecular plasmas. The numerical results are then interpreted in terms of macroscopic discharge parameter (electric field and current density) by means of Ohm's law and the electron energy equation. The resulting current density vs. electric field characteristic also exhibits an S-shaped dependence. DC glow discharge experiments have been conducted in flowing low temperature atmospheric air and nitrogen plasmas. Electrical characteristics were measured and the thermodynamic parameters of the discharge were obtained by spectroscopic measurements.