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Photomultiplier
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The output from the scintillation crystal is a quantity of light which must be measured and converted into an electrical signal. Conventionally this is done by a photomultiplier tube shown here.

  • the light photon strikes a light sensitive layer, the photocathode, causing it to emit a photoelectron;

  • the photoelectrons are focused electrostatically onto the first of a series of electron multiplier stages called dynodes;

  • the dynodes emit more electrons than they receive thus the signal is amplified;

  • the amplifier signal is then collected at the anode and hence can be measured; and

  • the magnitude of the final signal is proportional to the scintillator light output, which is proportional to the energy loss that produced the scintillation.

 

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1999, 2000 The University of Liverpool, Department of Physics

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