Demonstration of a Re-Activatable Scandate Cathode for a High-Current Sheet Beam Electron Gun

A re-activatable scandate cathode for a high-current sheet beam electron gun was demonstrated in experiment. The re-activatable scandate cathode was impregnated with high purity emission-active materials composed of $\beta $ -Ba2ScAlO5 and Ba3Al2O6, which were synthesized employing the polyacrylamide-assisted sol-gel method. The emission-active materials are essential for the scandate cathode to achieve low hygroscopicity and re-activatability. As a result, the re-activatable scandate cathode exhibits a low mass gain of only 0.005% after 1000 hours in air, and delivers an emission current density of 42 A/cm2 at 1140 °C. The high-performance scandate cathode was integrated into a compact sheet beam electron gun, which features a stepped elliptical focus electrode to enable anisotropic electrostatic compression. At a cathode temperature of 1140 °C and a beam voltage of 24.6 kV, the sheet beam electron gun yields a compressed sheet beam with a peak beam current of 189 mA. During three independent air-exposure, evacuation, and re-activation cycles, the beam current varied by no more than 5%. These findings confirm that the re-activatable scandate cathode is suitable for the high-current sheet beam electron gun.