Energy resolution of scintillation detectors with SiPM light readout

A development of silicon photomultipliers (SiPM), with a large number of micro-pixels and improved linearity of the pulse height response, allow discussing their possible application to gamma spectrometry with scintillators. Most of the measurements were done with Hamamatsu MPPCs sensors equipped with 3600 and 14400 pixels because of their well pronounced single photoelectron spectra. It allowed precisely measure the photoelectron (phe) numbers/fired pixels and then to discuss in a quantitative manner an obtainable energy resolution. The studied detectors were characterized first by means of a laser light pulser and then by 3×3×3 mm³ LFS and CsI(Tl) crystals coupled to 3×3 mm² Hamamatsu MPPC. In the study with the light pulser, the linearity of the MPPC response, expressed in the photoelectron number measured in relation to the first photoelectron, versus a light pulse intensity observed with PMT was checked and then the pulse height resolution was measured. Through analysis of the energy resolution the lower limit of the phe number was derived, assuming Poisson statistic. Further on, based on a directly measured phe number, the discussion of an excess noise factor of MPPC was done. In scintillation tests the measurements of the energy resolution and non-proportionality of the light yield were done with LFS and CsI(Tl) and discussed in a quantitative way, based on the measured PHE number, for both types of 3×3 mm² MPPC detectors.