Optimal design of a CsI(Tl) crystal in a SiPM based compact radiation sensor

Abstract

In this study, a compact radiation sensor for integration into mobile applications is proposed consisting of a CsI(Tl) crystal and a silicon photomultiplier with a 3 x 3 mm(2) active area. Considering the size limit of mobile devices, the optimal size of the CsI(Tl) crystal was determined so that it has the best figure of merit (the absolute detection efficiency over the relative energy resolution) in the gamma energy spectrum while satisfying the criteria for the uniformity of the angular response. The final suggested dimensions consist of a cylindrically shaped crystal with a diameter of 5 mm, a total length of 5 mm and a tapered head length of 1 mm.