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Author: Paul James Rose
Publisher:
ISBN:
Category : Imaging systems
Languages : en
Pages : 208
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Author: Paul James Rose
Publisher:
ISBN:
Category : Imaging systems
Languages : en
Pages : 208
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages : 4
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A coded aperture neutron imaging system developed at Brookhaven National Laboratory (BNL) has demonstrated that it is possible to record not only a flux of thermal neutrons at some position, but also the directions from whence they came. This realization of an idea which defied the conventional wisdom has provided a device which has never before been available to the nuclear physics community. A number of potential applications have been explored, including (1) counting warheads on a bus or in a storage area, (2) investigating inhomogeneities in drums of Pu-containing waste to facilitate non-destructive assays, (3) monitoring of vaults containing accountable materials, (4) detection of buried land mines, and (5) locating solid deposits of nuclear material held up in gaseous diffusion plants.
Author: Kenneth M. Gibbs
Publisher:
ISBN:
Category : Image processing
Languages : en
Pages : 498
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Category :
Languages : en
Pages : 13
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Category :
Languages : en
Pages :
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Category :
Languages : en
Pages : 5
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Category :
Languages : en
Pages : 6
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To facilitate the process of re-entry vehicle on-site inspections, it would be useful to have an imaging technique which would allow the counting of deployed multiple nuclear warheads without significant disassembly of a missile's structure. Since neutrons cannot easily be shielded without massive amounts of materials, they offer a means of imaging the separate sources inside a sealed vehicle. Thermal neutrons carry no detailed spectral information, so their detection should not be as intrusive as gamma ray imaging. A prototype device for imaging at close range with thermal neutrons has been constructed using an array of 3He position-sensitive gas proportional counters combined with a uniformly redundant coded aperture array. A sealed 252Cf source surrounded by a polyethylene moderator is used as a test source. By means of slit and pinhole experiments, count rates of image-forming neutrons (those which cast a shadow of a Cd aperture on the detector) are compared with the count rates for background neutrons. The resulting ratio, which limits the available image contrast, is measured as a function of distance from the source. The envelope of performance of the instrument is defined by the contrast ratio, the angular resolution, and the total count rate as a function of distance from the source. These factors will determine whether such an instrument could be practical as a tool for treaty verification.
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Category :
Languages : en
Pages :
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In the past year, a prototype fast-neutron coded-aperture imager has been developed that has sufficient efficiency and resolution to make the counting of warheads for possible future treaty confirmation scenarios via their fission-neutron emissions practical. The imager is constructed from custom-built pixelated liquid scintillator detectors. The liquid scintillator detectors enable neutron-gamma discrimination via pulse shape, and the pixelated construction enables a sufficient number of pixels for imaging in a compact detector with a manageable number of channels of readout electronics. The imager has been used to image neutron sources at ORNL, special nuclear material (SNM) sources at the Idaho National Laboratory (INL) Zero Power Physics Reactor (ZPPR) facility, and neutron source and shielding configurations at Sandia National Laboratories. This paper reports on the design and construction of the imager, characterization measurements with neutron sources at ORNL, and measurements with SNM at the INL ZPPR facility.
Author: Timothy Donald Jackson
Publisher:
ISBN:
Category : Fast neutrons
Languages : en
Pages : 241
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Quantification of the mass of plutonium in facilities that process plutonium is important for both nuclear safeguards concerns and safety concerns, and multiple methods to non-destructively quantify plutonium sample characteristics have been proposed, particularly when the sample is located directly adjacent to or within the measurement device. In prior work, coded-aperture fast neutron imaging has been developed to demonstrate the imaging of neutron emitting radiation sources in a qualitative fashion, where the sources may be located meters to tens of meters away. Building upon prior work, this work develops the use of a Maximum Likelihood Expectation Maximization (MLEM) reconstruction technique to simultaneously reconstruct neutron sources measured from different detector positions. Moreover, a modified system response model is developed to accurately but quickly perform forward projections in order to accurately reconstruct and quantify neutron source characteristics including source intensity and location. The system response model incorporates mask transmission, a heterogeneous detector pixel array, scattering within the mask, and scattering within the detector, allowing for the expected detector data from a single source position to be generated in less than a second. The behavior of the MLEM reconstruction technique is discussed, and measuremen ts of Cf-252 sources, acting as a surrogate Pu material, are reconstructed and analyzed. Using the methods developed here, a single 74 [mu]Ci [microcurie] Cf-252 point source placed at a distance of 200 cm is reconstructed within 2% of the known position and within 3% of known intensity at distances up to 300 cm. Measurements of more than one source and implications for Pu measurements in facilities are also discussed.
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Languages : en
Pages :
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