The Fast Neutron Imaging Telescope (FNIT) - hardware development and prototype testing

We describe the design and performance of a prototype instrument with capabilities for both imaging and spectroscopy of sources of 1-10 MeV neutrons. The laboratory prototype is composed of custom-designed liquid scintillator detectors and employs measurements of double neutron-proton scattering to determine the direction and energy of incident neutrons. The detectors provide measurements of the position, energy deposit and pulse shape for each interaction. Pulse shape discrimination and a time-of-flight measurement between coincident interactions in two detectors are used to identify the neutron events, reject background due to Compton scattered gamma radiation and provide a measure of the scattered neutron energy. Calculations employing double n-p scattering kinematics are used to accumulate images and spectra of the neutron source. The quality of these images and spectra is correlated with the energy, position and timing resolution of the detectors. The prototype instrument achieves ~5deg angular resolution and 20% energy resolution (1sigma). This paper presents the design and the most recent results.