Characterization and performance of SiPM-CsI(Tl) detector for low-energy γ- and X-ray spectroscopy

In this study, we coupled the low background CsI(Tl) crystal to a SensL J-series 60035 SiPM and detected low-energy γ and X-rays from Cobalt (⁵⁷Co) and Iron (⁵⁵Fe) radioactive sources. A distinct and well-resolved 5.9 keV X-ray peak was observed from the ⁵⁵Fe source. The 6.4 and 14.4 KeV X-ray peaks from the ⁵⁷Co source were measured and found to be very well separated from the background as well. Based on the SiPM single photoelectron peak mean value, the light output of CsI(Tl)+SiPM detector and absolute light yield of CsI(Tl) was calculated down to 5.9 keV. After correcting the reflectivity, and crosstalk factor the Absolute light yield was estimated to be 55 ± 3 ph/keV. The detector light output in terms of photoelectron per equivalent energy was calculated to be 13 ∼16PE/keV_ee. Furthermore, measurements of energy resolution and non-proportionality were done all the way down to the X-ray region. According to our findings, the SiPM coupled to CsI(Tl) could be an excellent detector for lower energy experiments such as dark matter searches and can be used in the study of neutrino physics as well as other high energy physics experiments.