Test procedures and characterization of silicon photomultipliers for photometric detection in astrophysics

Silicon photomultipliers (SiPM) are a typology of solid-state sensors that in recent years are replacing the established photomultiplier tube technology in a variety of uses. This kind of sensors find high demand in experiments carried out at very low light intensity (in the order of single photon detection) and also where high temporal precision (of the order of ns) and a reduced geometric encumbrance is required. The Bruno Kessler Foundation (FBK) has developed the near ultra violet high density low cross-talk (NUV-HD Low-CT) sensor optimized for the detection of photons in the ultraviolet spectrum jointly with a minimization of the optical cross-talk between adjacent microcells. These sensors are particularly suitable for equipping the imaging air cherenkov telescopes as intended for the CTA observatory. Optical modules consisting of 16 SiPMs (each one of 6 x 6 mm(2)) were assembled in INFN laboratories to be integrated into the focal plane of the medium-sized telescope prototype with a Schwarzschild-Couder double-mirror optic (SCT). This report will describe the test procedures to verify the performance of these 6 x 6 mm(2) sensors. Furthermore the assembly procedures developed to integrate the sensors on the detection modules and equip the focal plane chamber of the SCT prototype telescope (currently operational and under testing at the Fred Lawrence Whipple Observatory, Arizona) will also be presented.