Performance characteristics and measurements used to predict life expectancy of barium oxide cathodes

Barium Oxide Cathodes are perhaps the best known of all thermionic emitters. Discovered by Welinelt in 1903, they have been used in vacuum electron devices (VEDs) since shortly after that. Even today there are as many as 300 million oxide cathodes made each year for use in display devices worldwide. This paper addresses their use in VEDs such as high power klystrons where they are still employed in critical medical and radar applications. Compared to display devices these medical and radar systems are very expensive and the life of the klystrons used is significant in their overall cost. This paper will describe techniques that can be used to predict life expectancy of the oxide cathodes used in these klystrons.