New readout system of the FATIMA detectors based on Silicon Photomultipliers arrays

We present a new readout system based on large area Silicon Photomultipliers arrays coupled with cylindrical 1.5” × 2” LaBr 3 (Ce) FATIMA-type crystals. This readout achieves the fast-timing capabilities of such crystals coupled to the usual Photomultiplier Tubes. Energy calibration was measured with 137 Cs and 152 Eu standard radioactive sources, while the timing performances were investigated with a 60 Co radioactive source. We benchmark our results against the corresponding results obtained with the fast R9779 Photomultiplier tubes and highlight the importance of achieving similar energy and timing performances for nuclear structure experiments. The FWHM energy resolution for the 1.5” × 2” LaBr 3 (Ce) crystal coupled with the SiPM and PMT was found to be 3.31(2) % and 3.85(1) % , respectively, for the 661.6 keV transition of the 137 Cs source. The timing resolution was measured between a conical crystal known for its fast response and a cylindrical crystal coupled to a SiPM or PMT readout. We obtain values of FWHM = 230(1) ps and 232(1) ps, respectively, between the 1173.2–1332.5 keV transitions of the 60 Co source. In addition, a temperature effect compensation circuit was developed to maintain a good stability of the gain during long measurements, typical for in-beam/off-beam experiments in nuclear physics.