Development of Eu:SrI2 Scintillator Array for Gamma-Ray Imaging Applications

Eu:SrI
₂
bulk single crystals with 1.5-in diameter were grown using the Bridgman-Stockbarger technique and special-shaped crucibles. We will report on the growth of the 1.5-in size Eu:SrI
₂
single crystal and the preliminary test of the same sample cut in size of 10×10×10 mm
³
with polishing. An energy resolution of 3.2% full width at half maximum (FWHM) was obtained for
¹³⁷
Cs. After cutting and polishing the grown crystal to the size of 3×3×3 mm
³
, 8×8 matrix Eu:SrI
₂
arrays were fabricated. We made a test module consisting of Eu:SrI
₂
arrays, which was optically coupled with position sensitive photomultiplier tube (PSPMT) and multi-pixel photon counter (MPPC) array. The position and energy performance of the test module were evaluated using
¹³⁷
Cs and
⁵⁷
Co radioactive sources. As a result, we were able to resolve all pixels clearly. A good energy resolution of 6.7% ± 0.7% (FWHM) and 8.2% ± 2.5% (FWHM) for 662 keV was obtained using PSPMT and MPPC arrays, respectively. In the same way, energy resolution of 12.7% ± 1.3% and 14.7% ± 3.4% (FWHM) for 122 keV was obtained using PSPMT and MPPC-array, respectively. These energy resolutions considerably degraded compared with an energy resolution of the single piece of Eu:SrI
₂
sample owing to the thinness of the Teflon reflector. This conclusion can be considered as a strong motivation for future research on the choice of reflector materials and structure of the Eu:SrI
₂
array.