Timing resolution of SiPM technologies before and after neutron irradiation

In recent years, silicon photomultiplier (SiPM) technology has been getting attention from various applications due to its low cost, immunity to magnetic field, compactness and ruggedness. However, its applicability in experiments with harsh radiation environments is still limited due to lack of corresponding radiation damage studies. A 10-year lifetime operation in a typical Small Angle Neutron Scattering (SANS) experiment with an acceptable degradation in photon detection efficiency has already been reported. In this article, we discuss the feasibility study of SiPM technology in neutron time of flight experiments. For this purpose, two analog SiPMs, developed by SensL and Hamamatsu, have been irradiated with cold neutrons (5 Å ) up to a dose of 6ċ1012 n/cm2 at the KWS-1 instrument of the Heinz Maier-Leibnitz Zentrum (MLZ) in Germany. After irradiation, the timing resolutions of the SiPMs have been measured under pulsed laser beam with a few hundred photons (405 nm) per pulse, and a degradation of up to 6 ps has been observed. The degradation might be a result of noise increase, introduced by surface defects caused by neutron exposure damage. Additionally, variation of the excess voltage helped to reveal the difference in the timing resolutions between irradiated and non-irradiated SiPMs, which remained almost constant.