Recent Work on Fast Photomultipliers Utilizing GaP(Cs) Dynodes

There exists an increasing demand for photomultipliers with better time resolution, higher count rate capabilities and generally faster time response. This paper discusses fundamental electron-optical considerations which determine the speed of response of electrostatically-focussed photomultipliers. The nature of time broadening is discussed with regard to geometrical and initial velocity effects at dynode surfaces. Time limitations inherent in the dynode material itself are also treated. Examples of different fast photomultiplier structures are given. A discussion of various delta-function light sources is included and the relative merits of these sources with respect to time performance, ease of use and cost is reviewed.