Publications

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Fast neutron based inspection systems are of interest in many Homeland Security applications because they offer the potential for elemental identification particularly for low Z elements which are the prime constituents of explosives. We are investigating a resonance tomography technique which may address some of the current problems found in fast neutron based inspection systems. A commercial off-the-shelf DT generator is used with an array of detectors to probe materials simultaneously over a large energy range and multiple viewing angles allowing for simultaneous 3-D imaging and materials identification. A prototype system has been constructed and we present here recent results for the identification of materials with differing H, C, N, O compositions. © 2011 IEEE.

Passive detection of special nuclear material (SNM) at long range or under heavy shielding can only be directly achieved by observing the penetrating neutral particles that it emits: gamma rays and neutrons in the MeV energy range. The ultimate SNM standoff detector system would have sensitivity to both gamma and neutron radiation, a large area and high efficiency to capture as many signal particles as possible, and good discrimination against background particles via directional and energy information. We are exploring the use of time-modulated collimators that may lead to practical gamma-neutron imaging detector systems that are highly efficient with the potential to exhibit simultaneously high angular and energy resolution. We will present results from a large standoff SNM detection demonstration using a prototype high sensitivity time encoded modulation imager. © 2011 IEEE.

The neutron scatter camera was originally developed for a range of SNM detection applications. We are now exploring the feasibility of applications in treaty verification and warhead monitoring using experimentation, maximum likelihood estimation method (MLEM), detector optimization, and MCNP-PoliMi simulations.

We present advances with a 32 element scalable, segmented dual mode imager. Scaling up the number of cells results in a 1.4 increase in efficiency over a system we deployed last year. Variable plane separation has been incorporated which further improves the efficiency of the detector. By using 20 cm diameter cells we demonstrate that we could increase sensitivity by a factor of 6. We further demonstrate gamma ray imaging in from Compton scattering. This feature allows for powerful dual mode imaging. Selected results are presented that demonstrate these new capabilities.

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Because of their penetrating power, energetic neutrons and gamma rays ({approx}1 MeV) offer the best possibility of detecting highly shielded or distant special nuclear material (SNM). Of these, fast neutrons offer the greatest advantage due to their very low and well understood natural background. We are investigating a new approach to fast-neutron imaging - a coded aperture neutron imaging system (CANIS). Coded aperture neutron imaging should offer a highly efficient solution for improved detection speed, range, and sensitivity. We have demonstrated fast neutron and gamma ray imaging with several different configurations of coded masks patterns and detectors including an 'active' mask that is composed of neutron detectors. Here we describe our prototype detector and present some initial results from laboratory tests and demonstrations.

Because of their penetrating power, energetic neutrons and gamma rays ({approx}1 MeV) offer the best possibility of detecting highly shielded or distant special nuclear material (SNM). Of these, fast neutrons offer the greatest advantage due to their very low and well understood natural background. We are investigating a new approach to fast-neutron imaging- a coded aperture neutron imaging system (CANIS). Coded aperture neutron imaging should offer a highly efficient solution for improved detection speed, range, and sensitivity. We have demonstrated fast neutron and gamma ray imaging with several different configurations of coded masks patterns and detectors including an 'active' mask that is composed of neutron detectors. Here we describe our prototype detector and present some initial results from laboratory tests and demonstrations.

We present advances with a 32 element scalable, segmented dual mode imager. Scaling up the number of cells results in a 1.4 increase in efficiency over a system we deployed last year. Variable plane separation has been incorporated which further improves the efficiency of the detector. By using 20 cm diameter cells we demonstrate that we could increase sensitivity by a factor of 6. We further demonstrate gamma ray imaging in from Compton scattering. This feature allows for powerful dual mode imaging. Selected results are presented that demonstrate these new capabilities.

We have developed a novel modular automated processing system (MAPS) that enables reliable, high-throughput analysis as well as sample-customized processing. This system is comprised of a set of independent modules that carry out individual sample processing functions: cell lysis, protein concentration (based on hydrophobic, ion-exchange and affinity interactions), interferent depletion, buffer exchange, and enzymatic digestion of proteins of interest. Taking advantage of its unique capacity for enclosed processing of intact bioparticulates (viruses, spores) and complex serum samples, we have used MAPS for analysis of BSL1 and BSL2 samples to identify specific protein markers through integration with the portable microChemLab{trademark} and MALDI.

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The Neutron Scatter Camera (NSC) can image fission sources and determine their energy spectra at distances of tens of meters and through significant thicknesses of intervening materials in relatively short times [1]. We recently completed a 32 element scatter camera and will present recent advances made with this instrument. A novel capability for the scatter camera is dual mode imaging. In normal neutron imaging mode we identify and image neutron events using pulse shape discrimination (PSD) and time of flight in liquid scintillator. Similarly gamma rays are identified from Compton scatter in the front and rear planes for our segmented detector. Rather than reject these events, we show it is possible to construct a gamma-ray image by running the analysis in a 'Compton mode'. Instead of calculating the scattering angle by the kinematics of elastic scatters as is appropriate for neutron events, it can be found by the kinematics of Compton scatters. Our scatter camera has not been optimized as a Compton gamma-ray imager but is found to work reasonably. We studied imaging performance using a Cs137 source. We find that we are able to image the gamma source with reasonable fidelity. We are able to determine gamma energy after some reasonable assumptions. We will detail the various algorithms we have developed for gamma image reconstruction. We will outline areas for improvement, include additional results and compare neutron and gamma mode imaging.

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Because of their penetrating power, energetic neutrons and gamma rays (>-1 MeV) offer the best possibility of detecting highly shielded or distant special nuclear material (SNM). Of these, fast neutrons offer the greatest advantage due to their very low and well understood natural background. We are investigating a wholly new approach to fast-neutron imaging - an active coded-aperture system that uses a coded mask composed of neutron detectors. The only previously demonstrated method for long-range fast neutron imaging is double-scatter imaging. Active coded-aperture neutron imaging should offer a highly efficient alternative for improved detection speed, range, and sensitivity. We will describe our detector including design considerations and present initial results from a lab prototype. ©2009 IEEE.

Coded aperture neutron imaging detectors have the potential to be a powerful tool for the detection of special nuclear material at long range or under heavy shielding, using the signature of fast neutrons from spontaneous fission. We are building a prototype system using liquid scintillator cells, measuring 20'' x 2.5'' x 2.5'' each, in a reconfigurable arrangement. A cross-calibration of the observed detector data with the output of Monte Carlo simulation can both improve the sensitivity of the detector to fast neutron sources and increase the simulation accuracy, allowing the study of next-generation detector designs. Here we describe the tools and procedures developed to calibrate and simulate the detector response, including energy scale and resolution, interaction position, and gamma-neutron separation using pulse shape discrimination. Detector data and simulation are in good agreement for a test configuration. ©2009 IEEE.

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