Study of tube storage life degradation by means of mass spectrometer analysis

Electron tubes with small internal volume often fail by arcing when turned on after extended shelf life. We have identified the major failure mechanism in a particular tube type which has an internal volume of 0.1 cm³by using quadrupole mass analysis (QMA) of internal gases and Auger electron spectroscopy (AES) of impurity deposits on internal electrodes. The major failure mechanism is the release of nitrogen from ceramic voids during microcrack propagation. This gas adsorbs on the filament, electrodes, and internal tube surfaces and is released by thermal and electron stimulated desorption when the tube is turned on.