Comparison of SiPM and SDD based readouts of 1'' LaBr3:Ce scintillator for nuclear physics applications

Silicon Drift Detectors (SDDs) and Silicon PhotoMultipliers (SiPMs) are two silicon based photo-detector technologies for scintillator readout with applications in medical imaging, nuclear physics, space research and others. These devices provide compact scintillator readout solutions for spectroscopy, imaging and timing measurements. Goal of this work, is to make a comparison between these two photo-detector technologies, in particular for gamma-ray spectroscopy measurements. SDDs are characterized by very high quantum efficiency (> 80%) with no multiplication which helps to keep the statistical contribution to the energy resolution close to Poisson limit but, at the same time, makes the system very sensitive to readout electronics noise. SiPM devices on the other hand, have a very high multiplication gain (105-106) which makes the electronics noise contribution almost negligible, with only the dark count rate contribution which can be reduced with moderate cooling. However, they are characterized by lower Photo Detection Efficiency (PDE) ∼30-40% and statistical spread of the multiplication gain. In order to compare the spectroscopy performances of the two photo-detectors, we evaluate the energy resolution achievable with them using a large Lanthanum Bromide scintillator. Expected energy resolution with 1″ LaBr3:Ce and its sensitivity to various parameters of SDDs and SiPMs are evaluated to analyze the photo-detector performances. With SDD arrays of 2 nA/cm2 leakage current technology, an energy resolution of 3.0% has already been measured at -20 °C with Cs-137 source at a shaper peaking time of 6 μs. In this work, we measure an energy resolution of 4.9% with a SiPM tile readout by an RC filter (300 ns time constant) and a temperature of around 36 °C. These results are then used to validate the theoretical energy resolution estimates and to generalize the comparison of these two readout technologies.