On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime

LEANDRO PREVOSTO; HÉCTOR KELLY; BEATRIZ MANCINELLI; JUAN CAMILO CHAMORRO GARCÉS; EZEQUIEL CEJAS

PHYSICS OF PLASMAS

AMER INST PHYSICS

Lugar: American Institute of Physics; Año: 2015 vol. 22 p. 1 - 8

1070-664X

Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage?current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V, independent of the current discharge, and a constant current density at the cathode surface of about 11 A/cm2 for different discharge currents were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow thus suggesting a similar electric field distribution in the discharge. A kinetic model for the ionization processes in the discharge is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O and N which are usually absent in low-current glows thus causing that the ionization by electron-impact will be replaced with associative ionization which is independent of the reduced electric field. This leads to a negative V-I characteristic curve, in spite of the glow features of the discharge. Besides several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that this discharge regime may be considered to be close to an arc, but it is still a glow discharge as demonstrated by its overall properties, supported also by thermal non-equilibrium.