A compact neutron detector based on the use of a SiPM detector

This paper explores the performance characteristcs of a compact neutron detector based on the use of a silicon photo-multiplier (SiPM). These devices offer the first true solid-state alternative to traditional photomultiplier tubes in that they provide similar gain and photon-detection efficiency but with the small size and ruggedness of PIN diodes. The performance of a design based on the use of a 23mm diameter LiI crystal, viewed by a 14×14mm square SiPM, has been modeled and tested experimentally using Cf²⁵² fission-neutrons. The design incorporates a 10mm thick HDPE moderator in front of the 3mm crystal and an acrylic light-guide behind it. This provides the ability to detect a 10⁴ n/s source at 25cm in 12s with a confidence level of 93.5%. The gamma-ray rejection capability of the detector is excellent, allowing reliable detection of neutrons in a Co⁶⁰ gamma-ray background equivalent to a count-rate equivalent to 100kcps in a 2×2” NaI crystal. The impact of temperature changes on the performance of the detector, have also been explored along with methods to compensate for these changes.