FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA's Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic scintillators. By reconstructing n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. We describe the design of the FNIT prototype and present its energy reconstruction and imaging performance, assessed by exposing FNIT to a neutron beam and to a Pu fission neutron source.
Digital Object Identifier (DOI)
James M. Ryan ; Ulisse Bravar ; Erwin O. Flückiger ; John R. Macri ; Mark L. McConnell ; Benoit Pirard and Richard S. Woolf "Development and performance of the Fast Neutron Imaging Telescope for SNM detection", Proc. SPIE 6945, Optics and Photonics in Global Homeland Security IV, 694509 (April 11, 2008); doi:10.1117/12.777699; http://dx.doi.org/10.1117/12.777699
© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering.