Characterisation of a silicon photomultiplier device for applications in liquid argon based neutrino physics and dark matter searches

The performance of a silicon photomultiplier has been assessed at low temperature in order to evaluate its suitability as a scintillation readout device in liquid argon particle physics detectors. The gain, measured as 2.1 × 10⁶ for a constant over-voltage of 4V was measured between 25°C and -196°C and found to be invariant with temperature, the corresponding single photoelectron dark count rate reducing from 1MHz to 40Hz respectively. Following multiple thermal cycles no deterioration in the device performance was observed. The photon detection efficiency (PDE) was assessed as a function of photon wavelength and temperature. For an over-voltage of 4V, the PDE, found again to be invariant with temperature, was measured as 25% for 460nm photons and 11% for 680nm photons. Device saturation due to high photon flux rate, observed both at room temperature and -196°C, was again found to be independent of temperature. Although the output signal remained proportional to the input signal so long as the saturation limit was not exceeded, the photoelectron pulse resolution and decay time increased slightly at −196°C.