Direct-current glow discharges in atmospheric pressure air plasmas

Investigations have been conducted to experimentally validate the mechanisms of ionization in two-temperature atmospheric pressure air plasmas in which the electron temperature is elevated with respect to the gas temperature. To test a predicted S-shaped dependence of steady-state electron number density on the electron temperature and its macroscopic interpretation in terms of current density versus electric field, direct-current (dc) glow discharge experiments have been conducted in flowing low temperature, atmospheric pressure air plasmas. These experiments show that it is feasible to create stable diffuse glow discharges with electron number densities in excess of 10(12) cm(-3) in atmospheric pressure air plasmas. Electrical characteristics were measured and the thermodynamic parameters of the discharge were obtained by spectroscopic measurements. The measured gas temperature is not noticeably affected by whether or not the dc discharge is applied. The discharge area was determined from spatially resolved optical measurements of plasma emission during discharge excitation. The measured discharge characteristics are found to be in good agreement with the predicted electrical characteristics. (C) 2002 American Institute of Physics.