Counting individual photons

Meeting Notes

• January 30, 2007
• February 15, 2007
• March 1, 2007
• March 28, 2007
• April 5, 2007
• April 19, 2007

Research Project Pages

• Overview of the GlueX experiment
• My research paper
• Poster from Westport Science Fair
• Method for determining how many photons are in a pulse

Poster from Westport Science Fair

main poster

center top

center_bottom

Measured pulse photon count

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^-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.

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Article(s)

http://argus.phys.uregina.ca/gluex/DocDB/0007/000760/001/report-2-2007.pdf

PPT of the article Powerpoint_Silicon-Photomultiplier