Performance evaluation of newly developed SrI_2(Eu) scintillator

摘要

The development of europium-doped strontium iodide (SrI_2(Eu)) has attracted considerable attention, because of its excellent material properties as regards gamma-ray scintillator applications. These include its excellent energy resolution, high light output (＞80, 000 ph/MeV), and high effective atomic number (Z=49). Here we report on the performance of φ 1 in × 1 in SrI_2(Eu) cylindrical crystals newly fabricated by Union Materials Inc. In this study, we measured the energy resolution and light output at 10 ℃ temperature intervals between -40 and 40 ℃, using an optically coupled 2-in photomultiplier tube (PMT) (Super Bialkali, Hamamatsu). The Srl2(Eu) light output increased by 0.12%/℃ as the temperature decreased. At -40 ℃, we obtained the optimal energy resolution recording 2.91 +0.02% full width at half maximum (FWHM) for 662 keV gamma rays measured with ~(137)Cs. For comparison, we also measured the same crystal using both a large-area (19×19 mm~2) avalanche photodiode detector (APD) and 8×8 multi-pixel photon counter (MPPC) arrays of 3×3 mm~2 pixels. The energy resolutions of 2.94 ± 0.02%, 3.14 ± 0.06% and 3.99 ± 0.01% were obtained using PMT, APD, and MPPC, respectively, as measured at -20 ℃. We also measured the inherent background of SrI_2(Eu) in a cave composed of Cu-Pb blocks with their thickness of 5-10 cm confirming that SrI_2(Eu) has an extremely low inherent background radiation. In this study, we have shown that SrI_2(Eu) is a promising scintillator that can be utilized for radiation measurements incorporating low-energy X-rays to high-energy gamma rays, and can thus be applied in various medical, industrial, and environmental treatment fields in the near future.