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== Data ==
== Measured pulse photon count ==
[[Image:Pulses_Detected.JPG|thumb|150px|Data]] ||
At the right is a snapshot of the pulses produced by a hybrid photodiode (HPD, blue trace) illuminated by a blue light-emitting diode (LED, yellow trace). The average number of photons detected by the HPD per pulse is computed by taking the integral of the charge in a single pulse and dividing it by the average charge per photoelectron in the HPD. The manufacturer (DEP, Netherlands) specifies that the HPD collects 2700 ''e''<sup>-</sup> of charge per photoelectron produced in the cathode. The signal from the HPD was not amplified. It was measured in Volts by the oscilloscope with a 50Ω terminating resistor. The blue trace in the figure displays 20 mV per division, which becomes 0.40 mA / division after dividing by R=50Ω
<math>\int\ {f(x)}\, dx \approx 1000\ photons</math>
<math>\int\ {f(x)}\, dx \approx 1000\ photons</math>