High-Temperature Performance of Metal-Ceramic Photomultipliers

The origins of afterpulses in photomultipliers

“…By varying the discriminator level for the stop channel it was shown that the peaks with M / Z equal to 2 and 8 (He2+ and 02+) contained a much higher proportion of large afterpulses than those with M / Z equal to 4 and 16 (He+ and O+). Unlike the experiments described by Morton et a1 (1967) and Matheson and Helvy (1968), no positive identification of any molecular ions could be made.…”

“…Because the probability of afterpulse formation y and the afterpulse height distribution A(h) contain little explicit information, they were not of value in this investigation. However, as the work of Morton et al(l967) and Matheson and Helvy (1968) has shown, the afterpulse time distribution enables ions of different masses to be separated, so that the composition of the gas may be studied. In addition, because the secondary electron yield of photocathodes upon ion impact is high, most of the ions that strike the cathode may be detected as afterpulses at the anode.…”