Microhollow cathode discharges in atmospheric air

Summary form only given. Microhollow electrode discharges (MHCD) are gas discharges between closely spaced (submillimeter) electrodes containing openings with diameter, D, on the same order as the electrode gap. In previous experiments the reduction of the size of the cathode opening to 100 /spl mu/m has allowed us to generate stable, direct current discharges in air up to atmospheric pressure. The microhollow cathode discharges were operated at currents of up to 20 mA, corresponding to current densities of 250 A/cm/sup 2/ and at average electric fields of 16 kV/cm. The gas temperature of the MHCD was determined by spectroscopic measurements of the excited vibrational states of the nitrogen molecules. First results indicate that the gas temperature at atmospheric pressure and currents of 20 mA is close to 2000/spl deg/K. Parallel operation of MHCDs can be achieved by ballasting each discharge resistively. Without resistive ballast, the discharge itself needs to be resistive, that means the current voltage characteristic of the discharge must have a positive slope. Results of modeling show an increase of the forward voltage with current at high current values. However, overheating of the electrodes prevents DC operation of parallel discharges in atmospheric air in this current range. In order to extend the range of operation into the high current mode, were the discharge becomes resistive, it needs to be pulsed.