A powerful quality assurance technique for dispenser cathodes and electron guns

Normalized cathode current vs temperature plots, also known as Miram curves, are generally used for the determination of cathode emission characteristics as a function of time. These plots have since become a powerful tool for the design and quality assurance of electron guns used in microwave tubes. This paper describes practical methods of interpreting these plots to verify gun fabrication quality as well as cathode electron emission capability. Almost all gun characteristics can be verified and often corrected during initial testing before the gun is attached to the tube. After attachment to the tube the gun performance can be verified. Since these curves depend on cathode temperature, a detailed method of assuring heater quality is included. This allows heater current to be used as a measure of temperature when pyrometric measurements cannot be made.