Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI<sub>2</sub>(Eu)-based gamma ray
spectrometers provide detection performance advantages over standard detectors. SrI<sub>2</sub>(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” SrI<sub>2</sub>(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 Eu<sup>2+</sup>-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 SrI<sub>2</sub>(Eu) radioisotope identifier is described.
Development of the Europium-doped Strontium Iodide scintillator, SrI2(Eu2+), has progressed significantly in recent years. SrI2(Eu2+) has excellent material properties for gamma ray spectroscopy: high light yield (<80,000 ph/MeV), excellent light yield proportionality, and high effective atomic number (Z = 49) for high photoelectric cross-section. High quality 1.5” and 2” diameter boules are now available due to rapid advances in SrI2(Eu) crystal growth. In these large SrI2(Eu) crystals, optical self-absorption by Eu<sup>2+</sup> degrades the energy resolution as measured by analog electronics, but we mitigate this effect through on-the-fly correction of the scintillation pulses by digital readout electronics. Using this digital correction technique we have demonstrated energy resolution of 2.9% FWHM at 662 keV for a 4 in3 SrI<sub>2</sub>(Eu) crystal, over 2.6 inches long. Based on this digital readout technology, we have developed a detector prototype with greatly improved radioisotope identification capability compared to Sodium Iodide, NaI(Tl). The higher resolution of SrI<sub>2</sub>(Eu) yields a factor of 2 to 5 improvement in radioisotope identification (RIID) error rate compared to NaI(Tl).