Some Statistical Properties of Pulses from Photomultipliers

An examination of the integrated counts from 9502S and 9558A photomultipliers suggests that the statistical distribution is closely Poisson. An examination of the time intervals between consecutive pulses has shown an interesting effect: with a 9502S tube, a highly significant, although small, number of intervals are much longer than expected on a random hypothesis. This effect is explicable in terms of a loss of electrons between cathode and anode. Data on the variation of the signal/noise ratio with differing discriminator bias levels, are also presented.