Production of sheet electron beams with crossed-field secondary emission diodes

This paper is concerned with the development of a crossed-field secondary emission plane diode that is capable of producing sheet electron beams. Several diode designs having cathode widths of 45-80 mm have been tested and characteristics of output electron beams were investigated. For diode voltages in the 25-40 kV range, the electron beams were generated with currents of 15-45 A and linear current densities of 1-8 A/cm depending on the diode voltage, magnetic field strength, and the diode design. Cathode edge effects were found to be major contributory factors to nonuniformity of the linear current density distributions j(x) but their influence has been greatly reduced by incorporation of axial edge electrodes and downstream reflectors into the diode design and, as a result, ±12% uniformity of j(x) has been achieved. It has been shown that generation of thin (a few mm) sheet electron beams of ∼1 m wide with ∼1-5 A/cm current density is feasible.