Extending the Operating Pressure Range of a Forevacuum-Pressure Plasma-Cathode Ribbon Electron Beam Source

We show that the use of a two-stage discharge system—an extended hollow-cathode main discharge system with an auxiliary hollow-cathode discharge system mounted on the ends of the main discharge region—extends the operating pressure range toward a lower pressure range, down to 0.1 Pa. We have measured the electron flux from the auxiliary discharge cells to the hollow cathode of the main discharge as a function of operating gas pressure and the gas species and determined the dependence of main discharge ignition voltage on auxiliary discharge current. In the extended operating pressure range of 0.1–20 Pa, the source is capable of generating ribbon electron beams ( $20\times 2$ cm2) at an electron energy of 5 keV and a current density of 10 mA/cm2, while the nonuniformity along the length of the beam is less than 10%.