Electron heating in atmospheric pressure air discharges

Abstract

Summary form only given. Atmospheric pressure air plasmas have gained interest because of possible use as plasma reactors, light sources, for thin film deposition, surface modification and as plasma ramparts. For plasma ramparts, which are air plasmas serving as protective shields against incident microwave radiation, the required free electron density must be on the order of 10/sup 13/ cm/sup -3/ at gas temperatures of less than 2000 K. At equilibrium conditions, where the electron energy distribution is determined only by the value of the reduced electric field (E/N), the power density required to sustain an atmospheric pressure air plasma of 10/sup 13/ cm/sup -3/ electron density is approximately 5 kW/cm/sup 3/, a value which makes the generation and sustainment of large plasma volumes extremely expensive. However, since the rate coefficient for electron gain and loss processes, which define the power consumption, are dependent on the electron energy distribution function (EEDF), manipulation of the EED might allow us to reduce the power. Particularly shifting the EEDF towards higher electron energies (electron heating), without heating the gas, will cause an increase in ionization rate and decrease in attachment and recombination rate. Experiments with nanosecond high voltage pulses applied to a dc atmospheric pressure air plasma have been performed to study this effect.