TESTRUMENTATION
A gamma-ray photon is detectable only by means of
the enersy it loses in an interaction or interactions
with matter.
processes:
Gamma-ray photons lose energy by three main
photoelectric effect, Compton effect, and
positron-negatron pair production.
The cross-section for
each effect is dependent on the energy of the gamma-ray
photon and the atomic number of the detecting material.
The enersy given up by the gamma-ray photon under-
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soing any of these processes ultimately manifests itself
in the molecular excitation of the detecting meterial.
+ ee
Many organic crystals({such as anthracene, stilbene, and
diphenylbutadiene Jana many inoranic crystals(such as
thallium-activated sodium iodide, indium- or thalliumactivated lithiumiodide, and potassium iodide) relieve
this excitation in the form of useful scintillations of
light whose predominant color depends on the crystal.
The intensity of the light flashes produced in these
materials is dependent (in some cases, linearly) on the
energy of the incident photon (provided it is totally
absorbed).
These light pulses are detected by a photo-
multivolier tube which converts them into elettrical pulses.
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