The coated powder cathode: A medium current density, high reliability cathode

The Coated Powder Cathode has been developed in response to the need for a cathode combining the virtues of the various conventional cathode types, which would be suited to use in modern high power, high reliability electron tubes. It is best considered as a modification of the classic oxide cathode in which each particle of the emissive coating is covered with a thin layer of nickel. Inherent advantages of the cathode over the oxide cathode include the ability to sustain current densities up to 1 amp/cm²at approximately 810°C, improved coating adhesion and reduced coating resistance. This paper describes the concept, fabrication and mechanism of the cathode and presents data obtained from a diode evaluation program.