Characterization of FBK NUV-HD-Cryo SiPMs near LHe temperature

Five FBK “NUV-HD-Cryo” SiPMs have been characterized at 7 K and 10 K, with 405 nm and 530 nm LED light, respectively. The dark count rate (DCR) was measured to be 1 Hz for the 100 mm -size SiPMs, or 0.01 Hz/mm , which is 7 orders lower than the DCR at room temperature (RT). Given the very low DCR at these cryogenic temperatures, we measured the SiPMs’ I–V curves with such a method: illuminated the SiPMs with weak light, which differs from the conventional measurements at RT. Then, we measured the photo-detection efficiency (PDE), after-pulse (AP), and cross-talk probabilities (CT) with a bias voltage ranging from overvoltage (OV) 5 to 11 V. At the OV interval (5 to 11 V), the PDE was between 20%–45%, and the AP and CT were both between 5% and 20%. With an OV higher than 10 V, the PDE would be 40%, and the AP and CT are 20%. Combining all of the measurements, we are confident that the SiPMs can be equipped as the photosensors on liquid helium detectors, including but not limited to the time projection chambers, which we have proposed in hunting for low-mass dark matter directly and beyond.