Cryogenic characterisation of Silicon Photomultipliers for future Dark Matter experiments

The recent R&D for underground low energy particle physics experiments involve SiPMs extensively as the prime photo-detectors due to their ability to enhance the sensitivity of the rare particle events. For cryogenic applications, the SiPMs by LFoundry are being characterised at LNGS, Italy have Dark Count rate of 0.1 cps/𝑐𝑚2-0.3 cps/𝑐𝑚2 over the range of 5-8V over-voltage with afterpulse probability upto 10%. The internal CrossTalk (iCT) on the other hand, increases significantly with over-voltage introducing an excess of noise that can spoil the resolution of the measurement. Specific electronics was designed to test 1cm^2 SiPMs to calculate the iCT. A dedicated Poissonian laser model was constructed to satisfy the observed data. The PDE is another vital parameter that was modelled for cryogenic temperatures down to 87-77K through the direct measurements of triggering probability. For this purpose, a separate setup with two 1 mm^2 SiPMs were mounted and cooled down to 77K and then equally illuminated by different wavelengths' lasers. With the careful modelling of depletion region and absorption length in the SiPM lattice structure, SiPMs can be customised for cryogenic applications with PDE close to 60%. Additionally, external CrossTalk (eCT) phenomena was also explored through a dedicated setup. With maximum likelihood analysis, the parameters for eCT probability were extracted. In this talk, large area SiPM performance at cryogenic temperatures will be highlighted.