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

TL;DR

This study examines how the nonproportionality of SrI_2(Eu^2+) scintillators varies with temperature and high gamma-ray energies, impacting their suitability for astrophysical detectors.

Contribution

It provides new data on temperature-dependent nonproportionality and high-energy response of SrI_2(Eu^2+) scintillators, informing their application in space-based detection.

Findings

Nonproportionality increases with temperature, with a possible non-monotonic trend near 40°C.

At high energies (up to 6 MeV), nonproportionality changes by about 1.5 to 2 percent.

Nonproportionality behavior suggests charge trapping effects at certain temperatures.

Abstract

Strontium iodide doped with europium is a new scintillator material being developed as an alternative to lanthanum bromide doped with cerium for use in high energy astrophysical detectors. As with all scintillators, the issue of nonproportionality is important because it affects the energy resolution of the detector. In this study, we investigate how the nonproportionality of strontium iodide doped with europium changes as a function of temperature 16 deg. C to 60 deg. C by heating the strontium iodide doped with europium scintillator separate from the photomultiplier tube. In a separate experiment, we also investigate the nonproportionality at high energies (up to 6 MeV) of strontium iodide doped with europium at a testing facility located at NASA Goddard Space Flight Center. We find that the nonproportionality increases nearly monotonically as the temperature of the strontium iodide doped with europium scintillator is increased, although there is evidence of non-monotonic behavior near 40 deg. C, perhaps due to electric charge carriers trapping in the material. We also find that within the energy range of 662 keV to 6.1 MeV, the change in the nonproportionality of the strontium iodide doped with europium is about 1.5 to 2 percent.