Experimental apparatus for massive characterization of SiPM detectors at cryogenic temperature.

The silicon photomultipliers (SiPMs) are matrices of single-photon avalanche photodiodes (SPADs) that are often used to measure scintillation light in nuclear experiments due to their high sensitivity and dynamic range, combined with high mechanical robustness and low cost. These sensors require a bias above the breakdown voltage to operate, and cryogenic temperatures to reach low-dark-noise conditions. Some important parameters for the characterization of SiPMs are the previously mentioned breakdown voltage ($V_{bd}$), the quenching resistor ($R_{q}$), and the dark count rate (DCR). The experimental apparatus developed by the collaboration of the Ferrara and Bologna Universities and the Ferrara and Bologna INFN sites is capable to perform automatic characterization of 120 SiPMs in parallel, both at cryogenic and room temperature, in one measurement session. The setup can perform current-voltage characterizations, from which it extrapolates $R_{q}$ and $V_{bd}$ of each SiPM by fitting data in the forward and reverse region, respectively. It also governs a mechanical stage for SiPMs immersion in liquid nitrogen and has a FPGA-based countersystem dedicated to DCR measurements.