Production and characterization of high-pressure microwave glow discharge in a microgap aiming at VUV light source

Using microwave excitation, a high-pressure (∼ 1 atm), high-density (∼ 1015 cm− 3), non-equilibrium plasma is produced continuously in the 100-μm-microgap between two knife-edge electrodes at a power deposition level of ∼ 1 MW/cm3. In discharges using Ar and Xe, vacuum ultraviolet emission due to Ar2 and Xe2 excimers has been confirmed. To obtain plasma with a gas temperature as low as possible for efficient production of excimer molecules, the gas temperature characteristics of the microgap discharge was studied in detail for air and He/N2 discharges. The results indicate that the gas temperature is rather insensitive to the gas flow even if the flow is rapid enough to affect the diffusive heat conduction in the plasma. This appears to suggest the existence of a rapid heat transport mechanism other than diffusive heat conduction in the microgap plasma.