Abstract
The preparation of photocathodes in practical imaging tubes is generally carried out with alkali generating channels mounted in a side arm. In order to study the effect of the conductance of the tube connecting the side arm to the diode on the activation process, multialkali photocathodes were processed in diodes having two different values of conductance, viz. 5 / s −1 and 0.05 / s −1 respectively. The diodes were processed in a conventional mercury diffusion pump system giving a base pressure of approx. 10 −8 torr. An integral sensitivity of 150 μA/1m was obtained reproducibly in the case of diodes with higher values of conductance. The reproducibility of the sensitivity in the case of diodes with a smaller conductance value was found to be low. Quantitative analysis of the dynamics of the alkali vapours is being carried out with the help of an ion gauge based on the phenomenon of thermal ionization.
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