Light Induced Afterpulses in Photomultipliers

Various spurious effects limit the effectiveness of Photomultipliers when used in low-light-level coincidence counting experiments. One of these effects is afterpulses from light emission in the Photomultiplier. Here we present a study on the light emission in Photomultipliers using a variety of methods. First we image the light emission directly. Second we characterize the light emission spectrum. Finally we investigate the time resolved light emission. In particular we find that, not only the dynodes “glow,” but also the support structure emits light. A fluorescent effect is found. The experiments performed help to understand the fundamental effects of light emission and afterpulses in Photomultipliers.