4.3.2.2 Other low energy resolution scintillation detectors
Thallium-activated caesium-iodide CsI(Tl) crystals are neither hygroscopic nor particularly fragile. They have a density of 4.51 g/cm3, and a dead time of the order 10-9 s. However, these crystals are too expensive for widespread use.
Plastic scintillators consist of a solid solution of organic scintillating molecules in a polymerized solvent, and can be easily shaped and fabricated. The scintillation emission of a typical plastic scintillator has a maximum wavelength around 400 nm. Plastic scintillators are characterized by a relatively large light output (typically 25-30% of NaI(Tl)) and a short decay time, in the order of a nanosecond. This makes the material well suited for fast timing measurements required in high dose rate /activity applications. Plastic scintillators are often used for detection of charged particles, or when large-volume solid scintillators are needed. A large number of different plastic scintillators are commercially available in a wide selection of standard sizes and shapes, such as rod, cylinder, or flat sheet.
BGO (Bismuth-germanate-oxyde Bi4Ge3O12) scintillation crystals have been applied to field gamma ray spectrometry in boreholes. Due to their high density (7.13 g/cm3) they are efficient at high gamma ray energies and can be manufactured in smaller sizes.