Development and Characterization of a Versatile Neutron Detection and Interrogation System for PROACTIVE's Multi-Energy, Multi-Signature Neutron Interrogation Task

This work aims to develop an active interrogation approach focused on neutron-mediated fission signatures to characterize shielded uranium in arms control contexts with a reduced level of collateral information collection (e.g., without gamma spectroscopy) while maintaining some sensitivity to geometric (e.g., amount of shielding) and isotopic (e.g., fissile or fissionable material) features. In particular, the use of multiple neutron interrogation sources of different energy are proposed in combination with several fission-based signatures, each with their own dependencies: energythresholded neutron counting (i.e., coarse neutron spectroscopy), coincidence counting, differential dieaway, and beta-delayed neutron analyses. To support this research, an experimental capability is required to test the approach and understand realistic experimental systematics such as neutron generator nonideality. Specifically, a versatile, neutron interrogation and detection system is required to provide access to the range of signatures considered prior to system optimization. Such a system has been established at Lawrence Livermore National Laboratory (LLNL)/B262 that includes EJ-301 organic scintillators, 3He neutron detectors, and multiple DD and DT electronic neutron generators. Characterization of the system is reported on in this paper.