Evaluation of large volume SrI<inf>2</inf>(Eu) scintillator detectors

Abstract

Abstract-There is an ever increasing demand for gamma-ray detectors which can achieve good energy resolution, high detection efficiency, and room-temperature operation. We are working to address each of these requirements through the development of large volume SrI 2 (Eu) scintillator detectors. In this work, we have evaluated a variety of SrI 2 crystals with volumes >10 cm 3 . The goal of this research was to examine the causes of energy resolution degradation for larger detectors and to determine what can be done to mitigate these effects. Testing both packaged and unpackaged detectors, we have consistently achieved better resolution with the packaged detectors. Using a collimated gamma-ray source, it was determined that better energy resolution for the packaged detectors is correlated with better light collection uniformity. A number of packaged detectors were fabricated and tested and the best spectroscopic performance was achieved for a 3% Eu doped crystal with an energy resolution of 2.93% FWHM at 662keV. Simulations of SrI 2 (Eu) crystals were also performed to better understand the light transport physics in scintillators and are reported. This study has important implications for the development of SrI 2 (Eu) detectors for national security purposes.

Preliminary investigation of scintillator materials properties: SrI2:Eu, CeBr3 and GYGAG:Ce for gamma rays up to 9 MeV

“…The position of the centroid shows a variation of  3%, moving the source along the x and the y axes. Based on previous studies, we believe this to be due to optical "light-trapping" resulting from the Eu 2+ self-absorption and reemission [27]. Along lateral surfaces we also observe small variations of the centroid position (those are included in the ~ 3%, mention above), FWHM, owing to absorption phenomena.…”

“…Small samples (i.e. 1"x 1") of CeBr 3 and SrI 2 :Eu crystals appeared a few years later and there is still an intense R&D work on such detectors as the produced volume is constantly increasing over time [20][21][22][23][24][25][26][27][28][29]. The development of ceramic scintillator materials offers the possibility to have high-resolution gamma-ray spectroscopy at low cost.…”

“…SrI 2 :Eu has the best energy resolution (< 3%) among the studied detectors, and contains no internal radioactivity, but it is characterized by a slow signal and self-absorption [25][26][27][28][29]. The study of a large volume crystal is then important to understand how much the energy resolution is affected from this phenomenon.…”

“…Even though all three scintillator detectors studied in this work could be excellent substitutes of LaBr 3 :Ce, at the moment, only few detailed studies on large volume SrI 2 :Eu and CeBr 3 or in general on GYGAG:Ce scintillators [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] are available in literature. Table I.…”