Physics and Engineering of Radiation Detection

354 Chapter 6. Scintillation Detectors and Photodetectors

Radiation

Incident

Electron Hole

Eg

Valence Band

Core Valence Band

Conduction Band

E

Scintillation Light

Figure 6.3.3: Principle of core valence band luminescence in an in-

organic scintillator.

however, the choice is generally a compromise since a scintillator that is suitable due
to some other properties may not haveλmaxfor which the photocathode has highest
efficiency. Light yield is certainly another factor specially if the detector is to be
used in a low radiation environment.
In the following subsections we will list the advantages and disadvantages of some
inorganic scintillators that are commonly used in radiation detectors.

C.1 Thallium Doped Sodium Iodide (NaI:Tl)

Sodium iodide doped with thallium is the most widely used scintillator. Its key
features include

high light yield ( 41,000 photons perMeV),

blue emission that coincides with the requirement of most PMTs,

very low self absorption of scintillation light,

good spectroscopic performance,

easy availability and low production cost, and

possibility to produce large area crystals.