Comparative Evaluation of Cesium Iodide Scintillators Coupled to a Silicon Photomultiplier (SiPM): Effect of Thickness and Doping on the scintillators

Abstract

Cesium Iodide (CsI) crystals are referred as the ‘state of art’ scintillator materials used in most of Nuclear Medical Imaging systems, because of their high light yield outputs and low cost. In this work, a characterization in terms of energy resolution, photo-fraction, sensitivity as well as the figure of merit (FOM), of CsI:Na and CsI:Tl scintillators, are presented. A set of samples with 9 mm2 of cross section and a thickness ranging from 1 to 7 mm have been tested on a silicon photomultiplier (PM3350) using two different radioactive sources: 133Ba (0.081 MeV and 0.356 MeV) and 137Cs (0.662 MeV). The best energy resolution value was achieved by the 3x3x7 mm3 CsI:Na at 0.662MeV equal to 8%. For the CsI:Tl scintillator with the same dimensions the energy resolution was equal to 8.2%. At 0.081MeV the best energy resolution was recorded for crystals with 3x3x5 mm3 dimensions equal to 18.9% for CsI:Na and 24.9% for CsI:Tl. Results were compared to a reference NaI:Tl 3x3x5 mm3 and 3x3x10 mm3 as well as with previous published data.