The solution for single-photon timing with conventional photomultiplier tubes is similar to that recommended above for microchannel plate PMTs. The significant difference is that conventional photomultiplier tubes have slower rise times (~2 ns) and higher gains. A fast preamplifier is still needed between the detector output and the input to the timing discriminator, but the preamplifier gain can be lower, and the preamplifier rise time can be in the neighborhood of 1 to 3 ns. As a result, the preamplifier input noise normally does not contribute significantly to the timing jitter.

The PMT should be selected for low transit time spread from the cathode to first dynode, high first dynode gain, and a moderately fast single-electron response. For such a PMT, the timing jitter will usually be controlled by (a) the transit time spread from cathode to first dynode, and (b) the amplitude fluctuations caused by variations in secondary electron yields at the first dynode.

In this application, the signal rise time is slow enough that a conventional constant-fraction discriminator will provide optimum time resolution while minimizing the walk from the wide range of pulse heights produced by the detector. Alternatively, the Model 9307 pico-TIMING Discriminator can be used instead of the constant-fraction discriminator or the Model 9327 can be employed.