High pressure hollow cathode discharges

Summary form only given. The current-voltage characteristics of DC discharges in argon at pressures in the tens of Torr range in a hollow cathode geometry with a 0.7 mm cathode hole diameter have a positive slope for discharge currents of less than 30 mA. This resistive behavior has allowed us to operate the discharges in parallel without ballast. According to the "White-Allis" similarity law, the sustaining voltage of hollow cathode discharges is dependent on the product of gas pressure and cathode hole diameter. In order to extend the pressure range to higher values we have reduced the cathode hole diameter to 0.2 mm. With this cathode we were able to obtain stable discharges in air at a pressure of 50 Torr in a pulsed mode. Further reduction of the hole diameter to 75 /spl mu/m allowed us to extend the pressure range of hollow cathode discharge operation to 350 Torr in air with pulses of 1 ms duration. Both experiments were performed with hollow cathode arrays, where 48 and 90 cathode holes, respectively, were placed in parallel. The results indicate that atmospheric pressure hollow cathode discharges in air on be obtained if the hole diameter is reduced to values below 50 pm, and the discharge is operated in a pulsed mode. The possibility of generating large arrays of high pressure micro-hollow cathode discharges without ballast suggests their use as simple flat panels in light sources at high pressures. The nonthermal electron energy distribution typical for hollow cathode discharges might also allow their use as gas processing devices.