The behavior of various types of photomultipliers (CsAg cathodes and CsSb cathodes) at very low temperatures has been investigated and reported in the literature. No information was found on the behavior of photomultipliers having Ag-Bi-O-Cs photocathodes (S-10 type). A study was therefore made to investigate changes of the spectral sensitivity of two RCA 6217 photomultipliers as a function of temperature. The results show a behavior quite different from that of other types of photomultipliers. Efforts were made to separate dynode effects from cathode effects. No definite explanation as to the origin of this extraordinary behavior has been found.
W. Budde and P. Kelly, "Variations of the Spectral Sensitivity of RCA 6217 and 5819 Photomultipliers at Low Temperature," Appl. Opt. 10, 2612-2616 (1971)