Inorganic crystalline scintillators are single crystals that emit optical radiation upon exposure to X-ray, gamma-ray or neutron radiation. The scintillator crystals composed of the alkali, alkaline earth and rare earth halide crystals generally have an activator dopant uniformly dispersed throughout the crystal lattice. The most common scintillator crystal in use today is NaI(Tl). Some examples of other scintillator crystals are CsI(Tl), CsI(Na), LiI(Eu), CaF2(Eu), CdWO4, LSO, and LYSO. In the past 10 years there has been a major resurgence in scintillator research. In the search for brighter and more responsive scintillators, a major push has been made in developing improved scintillators from the alkaline earth and the rare earth halide families. Some examples of these crystals are LaBr3(Ce), LaCl3(Ce), CeBr3, SrI2(Eu), Cs2LiYCl6(Ce), Cs2LiLaCl6(Ce), and Cs2LiLaBr6(Ce). They have higher light output, better energy resolution and improved decay times in comparison to common scintillators such as NaI(Tl).
A number of the halide crystals are hygroscopic and need to be hermetically sealed in a container with an optical window to prevent absorption of moisture from the air. The scintillator crystal assemblies are closely coupled to either a photomultiplier tube or an avalanche photodiode to measure the light emitted. An example of an as-grown SrI2 (Eu) scintillator crystal in a quartz ampoule is shown in on the left.
An example of an as-grown SrI2 (Eu) scintillator crystal in a quartz ampoule.