Comments by "George Reynolds" (@karhukivi) on "The Glowing Crystals Behind a PET Scan" video.

  1. That is fluorescence, not scintillation. If you want to see scintillation, look at the luminous hands of an old radioactive watch with a strong lens, you will see the individual scintillations of the alpha particles striking the phosphor.
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  2.  @DrDeuteron  Most scintillators will also fluoresce . But if for example you have a ZnS screen and bombard it with alpha particles, there will be a succession of flashes which translate into pulses in a PMT. I would not consider that as fluorescence. A bit like the distinctions between killing, murder and dying, it depends on the circumstances!
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  3. A bit nit-picking I know, but 511 KeV radiation is not "high-energy" gamma radiation, rather it is on the low end of the gamma radiation range of 300 to 3000 KeV.
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  4. Nevertheless, the 511 peak will be apparent in the output spectrum of a typical PMT-NaI detector. The Compton scattering produces a "tail" on the low energy side. The pulse energy discriminators in the spectrometer will separate the 511 peak with about 6% efficiency. It is analogous to the "characteristic" energy of an X-ray tube, a strong "peak" and a tail.
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