Electron density and electron temperature in pulsed atmospheric pressure air plasmas

Summary form only given, as follows. The use of atmospheric pressure air plasmas as reflectors for microwave radiation with frequencies up to 30 GHz requires electron densities of approximately 10/sup 13/ cm/sup -3/. It has been shown, that direct current microhollow cathode sustained (MCS) discharges meet this requirement. However, the power consumption of such air glow discharges of 5 kW/cm/sup 3/ does not permit scaling to large volumes. Pulsing the discharge on a time scale, which is less than the characteristic time for glow-to-arc transition allows us to reduce the power density while keeping the average electron density at the required high value. So far the electron density in these pulsed discharges has been estimated using information on the plasma conductivity; data on the electron energy which is sharply shifted towards higher energies during the pulse have only been obtained through modeling. We have measured the electron density in a pulsed atmospheric air plasma by means of heterodyne interferometry. A measure for the electron energy, the electron temperature, was obtained by means of emission spectroscopy. 20% argon was added to atmospheric air, and the relative intensities of two argon lines, at 810.37 nm and 811.52 nm, were measured. Assuming a Maxwell-Boltzmann distribution of the electron energies allowed us to determine a value for the electron temperature.