The plasma-cathode electron gun

The plasma-cathode electron gun, which is being developed for operation with pulsed and cw e-beam lasers, is described. This device employs a plasma generated within a low-voltage hollow-cathode discharge as the source of electrons (1). Electrons extracted from the plasma pass through a triode-type control grid structure and are accelerated to high energies in a plasma-free region prior to emerging from the gun through a thin foil window. Experimental results obtained with 4×40 cm and 5×125 cm e-guns will be described. These devices have operated under cw conditions at beam energies in excess of 150 keV and beam current densities of 0.1 mA/cm²; earlier experiments have demonstrated the capability for cw and pulsed current densities up to 1 mA/cm² and 100 mA/cm², respectively. The plasma cathode electron gun offers an attractive alternative to other e-gun designs for many applications.