6.1. Scintillation Mechanism and Scintillator Properties 323
Figure 6.1.2: Relative light
yield of various scintillators at
different electron energies (34).resolution of different commonly used scintillation materials as a function of their
light output.
A point that should be kept in mind is that the production of scintillation light is
a very inefficient process since most of the energy delivered by the incident radiation
goes into radiationless transitions. for example the light yield of anthracene is only
about 20,000 photons perMeVof energy transferred by high energy particles. This
corresponds to an efficiency of approximately 5% for blue light (see example below).
However not all scintillators have such a low efficiency. Plastic scintillators are
obvious exceptions with an efficiency that is about 10 times that of anthracene. The
light yield of a scintillator is generally given in literature with reference to either
anthracene orNaI. The light yield ofNaIis about twice that of anthracene.
It should be pointed out that even though light yield is an extremely important
parameter but it is not the only criterion for selecting a scintillator for a specific