Sipm Readout Of Stilbene Crystals For Safeguards Applications

We developed and tested a compact neutron detector, based on a cylindrical stilbene crystal, directly read out by a silicon photomultiplier (SiPM). We experimentally studied the effect of light guides to improve the light collection efficiency when coupling small SiPMs to large-area crystals. The use of the light guide for a crystal-SiPM area ratio of 14x increased the overall detection efficiency approximately 5%, compared to a direct coupling. This modest efficiency improvement hardly justifies the additional design complexity due to adding a light guide to the assembly. Based on a simple readout scheme, a pair of detectors was used to measure correlated emissions from laboratory fission sources (i.e. Cf-252). An amplified SiPM readout board is being developed. Detectors equipped with this readout device will be used in a multiplicity counter assembly to inspect special nuclear materials.