Cathode testing at the Air Force Research Laboratory

An integral part of any vacuum rf device is the cathode. Many rf and microwave tubes utilize thermionic cathodes. However, these cathodes are generally limited to current densities less than 100 A/cm2, a limitation too great for the majority of High Power Microwave tubes. At the Air Force Research Laboratory, Directed Energy Directorate, we have to study a variety of explosive emission cathodes. This paper presents results on studies of several types of cathodes tested in a simple circular geometry. We also present results of research on different types of anode material. The data includes measurements of current, voltage, cathode lifetime, and cathode/anode out-gassing.15