Investigations of the Possibility of Reducing the Thermionic Sensitivity Occurring in Composite Photocathodes

The reduction of the thermionic emissivity of composite photocathodes of the Cs 2 O‐type is discussed in detail. Experiments are reported which achieve this result by surface treatment of a Rb 2 O‐substrate with Cs‐vapour. The thermionic emissivity can be reduced by at least two orders of magnitude while still maintaining good sensitivity in the infrared region. Conclusions are also drawn from the experiments with regard to the mechanism of the emission processes.