Microhollow cathode discharges as electron sources

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. Reducing the size of the cathode opening to 100 /spl mu/m has allowed us to generate stable, direct current discharges in argon and xenon up to atmospheric pressure, in air up to 400 Torr. Results of previous experiments with a hollow electrode configuration in air at several Torr indicated the presence of an "electron-beam" emitted through the anode hole. Experiments in a similar geometry but at much higher pressure, in air and in argon, point again to the fact that the energy distribution of the electrons emitted through the anode hole is anisotropic, with a strong component in forward direction. The dependence of the directed emission of electrons through the hollow anode from the hollow cathode discharge parameters, was studied in argon and air for pressures up to several hundred Torr, using a third, biased electrode as electric probe. A model for the observed directed electron emission, and its effect on the sustainment of a large volume discharge between hollow anode and the third electrode will be presented.