The Fast Neutron Imaging Telescope (FNIT) instrument is a NA-22 funded project for the design, construction, calibration and modeling of an instrument specifically tailored to measure and identify sources of fission neutrons - a key signature of Special Nuclear Material (SNM). A neutron detector that is sensitive to this energy range is of utmost importance to stop the proliferation of these materials. The proof of concept of this instrument has been successfully demonstrated with a limited FNIT prototype. After being constructed and fine-tuned at the University of New Hampshire (UNH), the prototype was calibrated with quasi-monoenergetic neutron beams at Crocker Nuclear Laboratory. Extensive Monte Carlo calculations are currently in the advance stages for the modeling of FNIT. These simulations, along with the calibration and tests that have been performed with a 252Cf source at UNH, will be used to determine the instrument efficiency and response. Further instrument simulations will allow us to determine the best methods for spectral and imaging de-convolution. Ultimately, these methods will be implemented into ldquoon-linerdquo software being designed for real-time analysis algorithms to be used in conjunction with a fully populated, portable neutron telescope. We present the most recent laboratory and instrument modeling results.
Leising M, Boggs S, Wunderer C, Beacom J, Diel R, Gehrels N, Hartmann D, Hernanz M, McConnell M, Milne P, et al.Nuclear Gamma-Ray Astrophysics, in astro2010: The Astronomy and Astrophysics Decadal Survey. Vol 2010. ; 2009.
McConnell M, Baring MG, Bellazzini R, Bloser PF, Costa E, Dennis B, Depaola G, Dovciak M, Elsner R, Emslie AG, et al.X-Ray and Gamma-Ray Polarimetry, in astro2010: The Astronomy and Astrophysics Decadal Survey. Vol 2010. ; 2009.
McConnell ML, Angelini L, Baring MG, Barthelmy S, Black JK, Bloser PF, Dennis B, Emslie AG, Greiner J, Hajdas W, et al.GRB Polarimetry with POET, in American Institute of Physics Conference Series. Vol 1133. ; 2009 :64–66.
McConnell ML, Bloser P, Case G, Cherry M, Guzik T, Hill J, Hunter S, Hurley K, Isbert J, Legere J, et al.The CASTER Black Hole Finder Probe, in AAS/High Energy Astrophysics Division #10. Vol 10. ; 2008 :41.09–41.09.
The spare detectors from NASA Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of g radiation or the movement of material that might shield γ-ray sources. The Gamma-Ray Experimental Telescope Assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of- flight for each coincident detection and compiles histograms of total energy and incident angle as computed using the kinematics of Compton scattering. The GRETA field of view is a cone with full angle approximately 120°. The sensitive energy range is 0.3 to 2.6 MeV. Energy resolution is 10% FWHM. The angular resolution, 19° in the simplified configuration tested, will improve to better than 5° with well-defined enhancements to the data acquisition hardware and data analysis routines. When operated in the mode that was used in space, the instrument is capable of measuring and imaging up to 30 MeV with an angular resolution of 1.5°. The response of the instrument was mapped in the laboratory with 14 Ci 22Na source 3 m from the instrument. Later, we conducted demonstrations under two measurement scenarios. In one, the remotely located instrument observed an increase of background radiation counts at 1.4 MeV when a large amount of lead was removed from a building and a corresponding decrease when the lead was replaced. In the other scenario, the location and isotope-identifying energy spectrum of a 500 μCi137Cs source 3-5 m from the instrument with two intervening walls was determined in less than one minute. We report details of the instrument design and these measurements.