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Figure 1
An example of the typical signal presented to the threshold comparator, resulting from a relatively short shaping time and a constant discharge current (black line), corresponding to discrete photon arrival times (red line). The two comparator thresholds (½ and [{3 \over 2}]) are indicated by the blue dotted lines. Typically, individual photons only trigger the lower threshold (most photons shown), but occasionally the time difference between two photons is short enough to lead to pile-up and triggering of the higher threshold (near t = 0.6 µs). The example shown here corresponds to a normalized photon rate 2λτ = 0.2, where 2τ is the decay time of the analog signal from 1 to 0. τ indicates the time for the signal from one photon to return to ½, 2τ for the one-photon signal to return to 0 and 4τ for the two-photon signal to return to zero.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 26| Part 5| September 2019| Pages 1621-1630
https://doi.org/10.1107/S1600577519007409
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