Application of an added-sinusoid, signal-multiplexing scheme to a compact, multiplexed neutron scatter camera

The development of compact and portable neutron imagers could be transformative for nuclear nonproliferation and security. Of the currently feasible neutron imaging concepts, the neutron scatter camera is the one that can be made most compact and versatile. Beneficially, this design also inherently measures the energy of incident neutrons on an event-by-event basis. Single volume and quasi-single volume neutron scatters have been proposed to fully maximize the potential of neutron scatter cameras and enable truly man-portable neutron imagers. Such imagers will likely have a very large number of readout channels to maximize the efficiency, so signal multiplexing to reduce readout channels would significantly reduce costs and size and facilitate wide-spread deployment. In this work a multiplexing method based on adding well-defined sinusoids to detector signal is applied to a quasi-single volume neutron scatter camera comprised of 6-mm × 6-mm × 60-mm EJ-299-34 plastic scintillators coupled to arrays of SensL 60035 C-series silicon photomultipliers to create a multiplexed neutron imager (MiNI). Such straightforward multiplexing enables the use of more detector elements for a given number of available signal readouts. The necessary calibrations and system characterizations are carried out to assess the multiplexing method's performance and to understand the behavior of the prototype MiNI. Its ability to successfully image a neutron source is demonstrated with a ²⁵²Cf spontaneous fission source placed in various locations around the MiNI. Finally, neutron spectroscopy is also performed, and the feasibility and benefits of multiplexing a quasi-single volume neutron scatter camera are demonstrated.