Changes

[[Image:Pulses_Detected.JPG|thumb|150px|Data]] ||

[[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''^- 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.  Visually integrating the red shaded area in the figure gives about 6.5 squares.  Each square is 0.40 mA * 250 ns = 100 * 10^-12.

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''^- 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.  Visually integrating the red shaded area in the figure gives about 6.5 squares.  Each square is 0.40 mA * 250 ns = 100 * 10^-12C. The charge of each electron is 1.6 * 10^-19 C, so this integral is 600 million collected electrons.  Dividing by 2700 collected electrons per photoelectron gives 230,000 detected photons per pulse.

<math>\int\ {f(x)}\, dx \approx 1000\ photons</math>

 

 

:<math>\int\ {f(x)}\, dx \approx 230000\ photons</math>