An efficient large area filamentary gun for E-beam stabilization of gas lasers

A filamentary electron gun utilizing a novel planar tetrode configuration was developed as a uniform large area, high energy electron source. The tetrode configuration consists of an anode, a grid situated between the cathode and anode, a filamentary cathode comprised of parallel equispaced filament wires and a spreader electrode located in a plane parallel to the filaments on the opposite side of the grid. The anode is in the form of a thin metallic foil window that transmits the high energy electron beam from the gun vacuum to the laser gas. By adjusting the electrode potentials and spacings, the divergent electron flow from individual filaments can be controlled to form a uniform anode beam current density distribution. For certain designs, beam uniformity can be achieved with the grid and spreader operated as noncurrent intercepting electrodes. This mode of operation is thermally efficient, both as a result of the low thermal conduction losses for directly heated filaments and because none of the kinetic beam power is dissipated by the low voltage gun electrodes.