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Parallel Operation Of Miniature Hollow Cathode Discharges

The pressure where hollow cathode discharges operate scales inversely with the cathode hole diameter. By reducing the size of the cathode hole to less than one millimeter, the authors were able to obtain stable operation of the hollow cathode glow discharge in air, up to ten`s of torr. The current-voltage characteristic was found to have a positive slope below approximately 5 torr. This allows the authors to operate hollow cathode discharges in parallel at these pressures without using ballast resistors for the individual discharges. In an experiment with four 0.75 mm diameter cathode holes drilled in a 0.75 mm copper plate, the authors obtained stable operation of the discharges at a threshold voltage of 380 V and a total current of 0.16 mA. The intensity of the glow from each hole tended to equalize after several hours of operation. The system was run for approximately 40 hours without evident change in performance. The stability with respect to parallel operation offers the possibility to use miniature hollow cathode discharge arrays as flat panel electron and ion sources.