Repetitively-pulsed DC glow discharge in atmospheric pressure air: modeling and experiments with a 12 kV, 10 Ns, 100 kHz pulse generator

Summary form only given, as follows. Low-temperature, low-power atmospheric-pressure air plasmas with high electron number densities have numerous potential applications such as medical sterilization, biochemical decontamination and EM-wave shielding. DC discharges can be used to create such plasmas, but as most of the energy goes into vibrational excitation of nitrogen molecules the power budget is extremely large (about 30 kW/cm/sup 3/ for n/sub e/=10/sup 13/ cm/sup -3/). The power budget can be greatly reduced however through the use of high-voltage electric pulses. In an air discharge under a wide range of conditions, the rate of recombination of electrons is approximately set by n/sub e/ and must be compensated for by ionization. DC discharges can maintain n/sub e//spl sim/10/sup 13/ cm/sup -3/ with electric fields producing electron temperatures on the order of 1 eV. Short (1-10 ns)-pulse discharges require higher peak electron temperatures of about 3-5 eV. As the energy lost to nitrogen molecules, per electron created, is several orders of magnitude smaller at T/sub e/=3 eV than at T/sub e/=1 eV, the ionization efficiency is much larger in the pulsed case than in the DC case, and the power budget decreases accordingly. We have devised a repetitively-pulsed discharge scheme using this principle. Parametric studies of the pulsed-discharge parameters were performed with a 2-temperature chemical-kinetic and a collisional-radiative model. A power reduction of more than 2 orders of magnitude at n/sub e/=10/sup 13/ cm/sup -3/ is predicted. This result is supported by experiments conducted in our laboratory with a single electric pulse. Experiments using a 100 kHz repetitive pulse generator, with typical voltage pulses of 12 kV amplitude and 10 ns FWHM, have also been conducted in atmospheric-pressure air at 1800 K. Electrical and optical measurements of the discharge are compared to the modeling predictions. The experimental and modeling results to date indicate th- t low-temperature atmospheric pressure air plasmas with n/sub e//spl sim/3/spl times/10/sup 12/ cm/sup -3/ can be sustained with power requirements of /spl sim/60 W/cm/sup 3/.