History and current status of strontium iodide scintillators

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu2+-doped crystals. Its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability make SrI2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI2(Eu) radioisotope identifier is described.