Degradation of oxide cathode properties in vacuum diode configuration

In this paper we investigate the oxide cathode life limiting effects on the basis of accelerated life predictions. In the diode accelerated life tests we found as a typical behaviour not only a shift of the space charge limit corresponding to a change of the diode distance, but also a continuous decrease of the space charge slope form an initial value of 1.46 to 1.40 and even below. We also investigate the sintering shrinkage and I/U characteristics of oxide coating as a function of operating time.