Production of CW High-Density Non-Equilibrium Plasma in the Atmosphere Using Microgap Discharge Excited by Microwave

A new technique for cw production of high-pressure, high-density, non-equilibrium plasma is presented. Using microwave excitation at 2.45 GHz, a stable atmospheric glow discharge was sustained between two knife-edge electrodes, having a length of 10 mm and facing each other across a ∼100 µm microgap. Laser Thomson scattering diagnostics indicates that the plasma density in the microgap is as high as 1.6×10 15 cm -3 at a microwave power of 100 W. The optical emission of the N 2 second positive band indicates that the gas temperature in the microgap is 1800 K, much lower than the electron temperature.