Investigation and application of impregnated scandate cathodes

This paper describes the investigation and application of scandate cathodes in Beijing Vacuum Electronics Research Institute (BVERI). The data of emission performance and lifetime were acquired both in closed-spaced diodes and in microwave tubes. Evaporation rates and gas poisoning properties have been determined. From the results of a series of diode experiments and the feedback information of practical usage in tubes, there are three key factors that in our opinion limit the practical application of scandate cathodes in general. These are no obvious saturation onset of I/U characteristics, weak ion bombardment resistivity and non-uniform emission. The authors conclude that to a certain extent, impregnated scandate cathodes (I-Sc) can be used as alternative electron sources instead of M-type cathode in microwave tubes.