Development of a compact, versatile electron beam source

The operating characteristics of a high-energy electron beam source are described. Electrons are extracted from a hollow cathode plasma and then accelerated by anode located downstream from the cathode. The anode to cathode surface area ratio is less than the root of the electron to ion mass ratio such that an electron sheath forms at the anode; a bias on this anode then accelerates the electron flux into a beam. Varying the hollow cathode current allows direct control of the beam current, while the bias on the accelerating anode determines the beam energy. A magnetic field can be used to assist in the beam collimation. Beams up to 5kV and 100mA have been produced with this device. Critical component designs for stable operation in both CW and pulsed operation are discussed.