Development of a SIPM based gamma-ray imager using a Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillator array

In this study we present the performance evaluation of a 6×6 Gd3Al2Ga3O12:Ce (GAGG:Ce) pixellated scintillator with 2×2×5mm³ crystal size elements, coupled to a silicon photomultiplier array (ArraySL-4). Evaluation was carried out with low energy isotopes i.e. ⁵⁷Co and ⁹⁹mTc. A symmetric resistive charge division matrix was used reducing array's 16 outputs to 4 position signals. A Field Programmable Gate Array (FPGA) Spartan 6 LX16 was used for triggering and signal processing of the signal pulses acquired using a free running sampling technique. Raw images of the crystals maps were acquired. The mean energy resolution at 140keV and 122.1 keV was 16.1±0.52% and 18.1±0.64% respectively, and the peak to valley ratio was found equal to 17.7±2.7. Comparative measurements of two 3×3×5mm³ CsI:Tl and GAGG:Ce scintillators of same thickness are also presented. All measurements were performed at room temperature ~25°C, without additional cooling. According to our knowledge this is the first time that the new developed GAGG:Ce scintillator array has been evaluated at low energies.