Multiplicity counter development with 6LiF/ZnS

The ³He shortage has driven a search for alternative neutron detection technologies. One of the active areas of research for ³He alternatives is safeguards applications. Neutron coincidence and multiplicity counters that do not rely on ³He are being designed and developed. Simulations with the Monte Carlo particle transport code MCNPX were used to compare the potential performance of multiplicity counters designed with a neutron capture media of either ¹⁰B or ⁶Li. The simulation results indicated that a high performing system, based on a standard figure of merit which considers the efficiency and die-away time, could be achieved with a counter constructed with sheets of ⁶LiF/ZnS layered with a plastic light guide. A four-panel bench-top counter based on the simulated configuration was constructed to demonstrate design feasibility and verify the model predictions. Presented here are the results of the system characterization, including efficiency, die-away time, gamma ray rejection, and vertical efficiency uniformity, and a comparison of the simulated results.