High-rate counters versus integrating devices in synchrotron experiments

The purpose of this paper is to illustrate the finite precision of counting measurements, due to the Poisson distribution of the photons from a pulsed source. This limitation of precision is important when the count rate is of the same order of magnitude as the bunch rate. We compare analytic results with measurements from a counting experiment using an avalanche photodiode and an integrating detector. Simple formulas are given stating both the dynamic and precision of counting with a periodic source.