Characterisation of electron beams produced by crossed-field secondary emission diodes

The crossed-field secondary emission (CFSE) diode is a compact, simple and cheap source of tubular electron beams. The physical mechanism of current p roduction is a self-sustained secondary electron emission, in this study, v oltage-current, temporal and spatial characteristics of electron beams prod uced by axisymmetric and non-axisymmetric CFSE diodes have been investigate d. The highest current obtained at the present stage of research is similar to 240 A generated with a diode having a cathode diameter of 64mm and oper ated with an applied voltage of similar to 20 kV. The electron beams are ch aracterised by extremely high temporal stability and narrow (similar to1.4m m) radial current density distributions. In axisymmetric diodes, the azimut hal current density distribution j (phi) is uniform but this is only achiev ed by careful adjustment of the cathode-anode assembly. In nonaxisymmetric diodes, the j (phi) distributions are strongly non-uniform and depend not o nly on the magnitude but also on the direction of the magnetic field.