Hollow-cathode electron source with a fast gas-puff valve

Summary form only given, as follows. In this paper the design and characteristics of a hollow-cathode electron source are presented. A pressure gradient between the cathode cavity and the drift region which is necessary for simultaneous operation of the hollow cathode discharge and the microwave generation is provided by a gas-puff valve. To produce a plasma inside the hollow cathode we used a pulse forming network (PFN) generator with output parameters of 10 kV, 10 /spl mu/s and 5 /spl Omega/. For reliable operation and the ignition of the hollow cathode discharge a mesh keep-alive electrode was used. Generation of high-current electron beams was provided by PFN generator: 30 kV 300 ns and 7 /spl Omega/. To protect the power supplies from the high-voltage accelerating pulse decoupling inductances were used. The gas distribution inside the cathode was measured by two fast Penning probes. The plasma temperature and density were studied by floating electric probes. It was found that at a discharge current amplitude of 130-470 A the potential drop between the hollow cathode and the output grid is 140-160 V. Inside the hollow cathode the density of the helium plasma is (2-3)*10/sup 12/ cm/sup -3/ and the plasma electron temperature is /spl sim/8 eV at a discharge current 120-270 A. It was shown that the plasma from the cathode cavity penetrates into the anode-cathode gap prior to the application of the accelerating pulse. Therefore, the observed amplitude of the electron current exceeds the value predicted by Child-Langmuir law.