High current, low pressure plasma cathode electron gun

A plasma-cathode electron gun based on a moderate pressure (> 5 mTorr) cold -cathode discharge and a high perveance, multiaperture accelerator was prev iously developed at Hughes Research Laboratories and produced electron beam currents of up to 1 kA at voltages of over 200 kV for pulse lengths of 100 mu s. This gun was limited in pulse repetition frequency and duty by the g as-puff system that provided adequate gas pressure in the hollow cathode to operate the glow discharge while keeping the pressure in the beam transpor t region sufficiently low. We describe a new plasma cathode electron gun (P CE gun) that eliminates this problem by replacing the glow-discharge plasma generator in the electron gun by a low-pressure thermionic discharge in a magnetic multipole confinement chamber. Proper design of the plasma generat or and electrical circuit provides high electron-current densities to the a ccelerator structure at very low gas pressure (< 10(-4) Torr). The static g as pressure permits the pulse repetition frequency to be very high (> 1.5 k Hz demonstrated) with electron beam currents up to 200 A at voltages up to 120 kV demonstrated. The design and performance of the PCE gun, along with several models used to predict and scale the performance, are discussed. (C ) 2000 American Institute of Physics. [S0034-6748(00)05302-8].