PROPERTIES OF PHOTOMULTIPLIERS WITH CAESIUM TELLURIDE PHOTOCATHODES

Measurements are described of the properties of a sample (seven tubes) of EMI type 9616 developmental photomultipliers having solar-blind, caesium telluride photocathodes. Results are given for the spectral sensitivity, the tube electron gain and pulse height distribution, and the cathode dark emission as a function of temperature. The results are compared with previous studies of this type of cathode and it is suggested that both the small unwanted response in the visible part of the spectrum (about 10-4 electrons per photon) and the slight dark emission (about 10 electrons cm-2 s-1 at 20°C) that are observed in the present cathodes are associated with an excess of caesium over the stoichiometric amount required for the compound caesium telluride.