Incidence angle dependence of the output response uniformity of photomultipliers

A simple system is described that allows the study of the photoelectron collection and quantum efficiency uniformity, i.e. the output response of a photomultiplier as a function of the angle of incidence of the light for a variety of wavelengths. Results are presented for the EMI 9956QQB and are discussed for both this model and the 9956QB photomultipliers, tubes frequently used in gas proportional scintillation counters. It is shown that the response uniformity is better for the shorter wavelengths and for incidence angles which are not too large