Characterization of a silicon photo-multiplier array with summing board as a photo-multiplier tube replacement in organic scintillator assemblies

Abstract

We report on the energy, timing, and pulse-shape discrimination performance of cylindrical 5.08 cm diameter × 5.08 cm thick and 7.62 cm diameter × 7.62 cm thick trans-stilbene crystals read out with the passively summed output of three different commercial silicon photo-multiplier arrays. Our results indicate that using the summed output of an 8 × 8 array of SiPMs provides performance competitive with photo-multiplier tubes for many neutron imaging and correlated particle measurements. For a 5.08 cm diameter × 5.08 cm thick crystal read out with SensL’s ArrayJ-60035_64P-PCB, which had the best overall properties, we measure the energy resolution as 17.8 ± 0.8% at 341 keVee (σ/E), the timing resolution in the 180–400 keVee range as 236 ± 61 ps (σ), and the pulse-shape discrimination figure-of-merit as 2.21 ± 0.03 in the 230–260 keVee energy range. For a 7.62 cm diameter × 7.62 cm thick crystal read out with SensL’s ArrayJ-60035_64P-PCB, we measure the energy resolution as 21.9 ± 2.3% at 341 keVee, the timing resolution in the 180–400 keVee range as 518 ± 42 ps, and the pulse-shape discrimination figure-of-merit as 1.49 ± 0.01 in the 230–260 keVee energy range. These results enable many scintillator-based instruments to enjoy the size, robustness, and power benefits of silicon photo-multiplier arrays as replacement for the photo-multiplier tubes that are predominantly used today.