Electron-beam sustained plasmas in optically pumped atmospheric pressure air

Summary form only given, as follows. Stable, low-power-budget, atmospheric pressure air plasmas are sustained using a combination of an electron beam as an efficient volume ionization source. Simultaneous optically pumped vibrational nonequilibrium of the diatomic air species is maintained to reduce the electron removal rate. The electron production rate in the plasmas is measured using a Thomson discharge probe and electron densities are determined from conductivity measurements as well as using microwave attenuation. Energy is transferred into the vibrational modes of the diatomic air species using resonant absorption of CO laser radiation by small amounts (1-5%) of carbon monoxide seeded into the air with subsequent vibration-vibration energy transfer between carbon monoxide and the other diatomics. Perpendicular to the laser beam axis a 0-80 keV, 0-20 mA electron beam enters the plasma cell through an aluminum foil window. The e-beam is operated in pulsed mode with a low duty cycle to reduce thermal stress on the foil window. At the intersection of the laser and the electron beam a plasma region with a volume of approximately 1 ccm is formed. We present measurements of the dependence of the electron removal rate on the level of vibrational excitation within the plasma. The power budgets required for the electron beam ionization and for maintaining a vibrational nonequilibrium by optical pumping as well as the total power budget required to sustain the cold atmospheric pressure air plasmas will be presented.