Basically, the liquid scintillation process is the conversion of the energy of a radioactive decay event into photons of light in a liquid. Photomultipliers (PM-tubes) detect the emission of light and convert the light pulse into an electrical signal. The intensity of the light pulse (number of photons emitted) is proportional to the energy of the radioactive decay event. Furthermore, the size (height) of the electrical pulse is proportional to the intensity of the light and, accordingly, also proportional to the energy of the decay event.

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