Scintillation properties of SrI_2(Eu^2+) (Strontium iodide doped with europium) for high energy astrophysical detectors: Nonproportionality as a function of temperature and at high gamma-ray energies

摘要

Strontium iodide doped with europium is a new scintillator material beingdeveloped as an alternative to lanthanum bromide doped with cerium for use inhigh energy astrophysical detectors. As with all scintillators, the issue ofnonproportionality is important because it affects the energy resolution of thedetector. In this study, we investigate how the nonproportionality of strontiumiodide doped with europium changes as a function of temperature 16 deg. C to 60deg. C by heating the strontium iodide doped with europium scintillatorseparate from the photomultiplier tube. In a separate experiment, we alsoinvestigate the nonproportionality at high energies (up to 6 MeV) of strontiumiodide doped with europium at a testing facility located at NASA Goddard SpaceFlight Center. We find that the nonproportionality increases nearlymonotonically as the temperature of the strontium iodide doped with europiumscintillator is increased, although there is evidence of non-monotonic behaviornear 40 deg. C, perhaps due to electric charge carriers trapping in thematerial. We also find that within the energy range of 662 keV to 6.1 MeV, thechange in the nonproportionality of the strontium iodide doped with europium isabout 1.5 to 2 percent.