High-Resolution Gamma-Ray Spectroscopy with a SiPM-Based Detection Module for 1' and 2' LaBr3:Ce Readout

In this paper, we present a silicon photomultiplier (SiPM)-based photodetector module designed to readout large cerium-doped lanthanum bromide (LaBr3:Ce) scintillators (cylindrical 1 '' x 1 '' and 2 '' x 2 '') for nuclear physics experiments. The detector prototype has a modular structure and implements a real-time stabilization of the SiPM gain to compensate for the gain drift with temperature. The SiPM module consists of an array of 5 by 6 near-ultraviolet high-density SiPMs (Fondazione Bruno Kessler, Italy), each one having an active area of 6 mm x 6 mm and 30-mu m microcells. The single array is used for the 1 '' crystal readout, and it is assembled in a 2 x 2 format to read the 2 '' scintillator. Spectroscopic measurements were performed with both crystals. The 2 '' crystal was irradiated with different radioactive sources in an energy range between 122 keV and 1.3 MeV, and an energy resolution of 3.19 +/- 0.01% full-width at half-maximum (FWHM) has been achieved at 662 keV. The result is very close to the 3.07 +/- 0.03% FWHM measured with Super Bialkali photomultiplier tube (PMT) (Hamamatsu R6233-100) at the same energy with the same 2 '' crystal. In the framework of the comparison between SiPM and PMT for LaBr3:Ce readout, we provide an analysis of the energy resolution contributions based on the measurements performed with the developed gamma-ray detection system.