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' × 1' and 2' × 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 × 6 mm and 30-μmmicrocells. The single array is used for the 1' crystal readout, and it is assembled in a 2× 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.