Position sensitive photosensors based on SiPM arrays

We report two approaches for a high-resolution, position sensitive, gamma ray detector, based on solid estate photosensors and scintillation crystals. Scintillation photons are detected with a custom-made array of 144 SiPMs (12×12) covering an area of 5×5cm². Individual SiPM signals are processed with 3 multiplexing ASICs. The performance of such assemble has been compared with a standard array of also 144 SiPM from SensL and a diode readout (AiT instruments) with 24 outputs corresponding to the number of rows and columns. The standard configuration easily permits to distinguish pixels of 1.57×1.57mm² with a timing resolution of 1.2ns. The custom configuration can hardly resolve pixels of 1.57×1.57mm² but reached a promising timing resolution of 750ps. This readout has the advantage to allow programing small array regions reducing the dark noise contribution. When 6×6 SiPMs are enabled, 1mm pixels are well resolved. Both approaches showed an energy resolution as good as 10%.