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Now showing items 1 - 16 of 46100

  • PROSPECT- A Precision Reactor Oscillation and Spectrum Experiment

    Bowden, N. S.  

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  • The PROSPECT physics program

    Ashenfelter, J.   Balantekin, A. B.   Band, H. R.   Barclay, G.   Bass, C. D.   Berish, D.   Bignell, L.   Bowden, N. S.   Bowes, A.   Brodsky, J. P.   Bryan, C. D.   Cherwinka, J. J.   Chu, R.   Classen, T.   Commeford, K.   Conant, A. J.   Davee, D.   Dean, D.   Deichert, G.   Diwan, M. V.   Dolinski, M. J.   Dolph, J.   DuVernois, M.   Erikson, A. S.   Febbraro, M. T.   Gaison, J. K.   Galindo-Uribarri, A.   Gilje, K.   Glenn, A.   Goddard, B. W.   Green, M.   Hackett, B. T.   Han, K.   Hans, S.   Heeger, K. M.   Heffron, B.   Insler, J.   Jaffe, D. E.   Jones, D.   Langford, T. J.   Littlejohn, B. R.   Caicedo, D. A. Martinez   Matta, J. T.   McKeown, R. D.   Mendenhall, M. P.   Mueller, P. E.   Mumm, H. P.   Napolitano, J.   Neilson, R.   Nikkel, J. A.   Norcini, D.   Pushin, D.   Qian, X.   Romero, E.   Rosero, R.   Seilhan, B. S.   Sharma, R.   Sheets, S.   Surukuchi, P. T.   Trinh, C.   Varner, R. L.   Viren, B.   Wang, W.   White, B.   White, C.   Wilhelmi, J.   Williams, C.   Wise, T.   Yao, H.   Yeh, M.   Yen, Y-R   Zangakis, G. Z.   Zhang, C.   Zhang, X.  

    The precision reactor oscillation and spectrum experiment, PROSPECT, is designed to make a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and probe eV-scale sterile neutrinos by searching for neutrino oscillations over a distance of several meters. PROSPECT is conceived as a 2-phase experiment utilizing segmented Li-6-doped liquid scintillator detectors for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT Phase. I consists of a movable 3 ton antineutrino detector at distances of 7-12 m from the reactor core. It will probe the best-fit point of the v(e) disappearance experiments at 4 sigma in 1 year and the favored region of the sterile neutrino parameter space at >3 sigma in 3 years. With a second antineutrino detector at 15-19. m from the reactor, Phase II of PROSPECT can probe the entire allowed parameter space below 10 eV(2) at 5 sigma in 3 additional years. The measurement of the reactor antineutrino spectrum and the search for short-baseline oscillations with PROSPECT will test the origin of the spectral deviations observed in recent theta(13) experiments, search for sterile neutrinos, and conclusively address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly.
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  • Background radiation measurements at high power research reactors

    Ashenfelter, J.   Balantekin, B.   Baldenegro, C. X.   Band, H. R.   Barclay, G.   Bass, C. D.   Berish, D.   Bowden, N. S.   Bryan, C. D.   Cherwinka, J. J.   Chu, R.   Classen, T.   Davee, D.   Dean, D.   Deichert, G.   Dolinski, M. J.   Dolph, J.   Dwyer, D. A.   Fan, S.   Gaison, J. K.   Galindo-Uribarri, A.   Gilje, K.   Glenn, A.   Green, M.   Han, K.   Hans, S.   Heeger, K. M.   Heffron, B.   Jaffe, D. E.   Kettell, S.   Langford, T. J.   Littlejohn, B. R.   Martinez, D.   McKeown, R. D.   Morrell, S.   Mueller, P. E.   Mumm, H. P.   Napolitano, J.   Norcini, D.   Pushin, D.   Romero, E.   Rosero, R.   Saldana, L.   Seilhan, B. S.   Sharma, R.   Stemen, N. T.   Surukuchi, P. T.   Thompson, S. J.   Varner, R. L.   Wang, W.   Watson, S. M.   White, B.   White, C.   Wilhelmi, J.   Williams, C.   Wise, T.   Yao, H.   Yeh, M.   Yen, Y. -R.   Zhang, C.   Zhang, X.  

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including gamma-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. The general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein. (C) 2015 Elsevier B.V. All rights reserved.
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  • Design of a transportable high efficiency fast neutron spectrometer

    Roecker, C.   Bernstein, A.   Bowden, N. S.   Cabrera-Palmer, B.   Dazeley, S.   Gerling, M.   Marleau, P.   Sweany, M. D.   Vetter, K.  

    A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV and a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm(2) rising to 5000 cm(2). For neutron energies above 20 MeV, the capture gating analysis predicted an effective area between 1800 cm(2) and 2500 cm(2). The multiplicity mode was found to be sensitive to the incident neutron angular distribution. (C) 2016 Elsevier B.V. All rights reserved.
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  • A note on neutron capture correlation signals, backgrounds, and efficiencies

    Bowden, N. S.   Sweany, M.   Dazeley, S.  

    A wide variety of detection applications exploit the timing correlations that result from the slowing and eventual capture of neutrons. These include capture-gated neutron spectrometry, multiple neutron counting for fissile material detection and identification, and antineutrino detection. There are several distinct processes that result in correlated signals in these applications. Depending on the application, one class of correlated events can be a background that is difficult to distinguish from the class that is of interest. Furthermore, the correlation timing distribution depends on the neutron capture agent and detector geometry. Here, we explain the important characteristics of the neutron capture timing distribution, making reference to simulations and data from a number of detectors currently in use or under development. We point out several features that may assist in background discrimination, and that must be carefully accounted for if accurate detection efficiencies are to be quoted. (c) 2012 Elsevier B.V. All rights reserved.
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  • Investigation of large LGB detectors for antineutrino detection

    Nelson, P.   Bowden, N. S.  

    A detector material or configuration that can provide an unambiguous indication of neutron capture can substantially reduce random coincidence backgrounds in antineutrino detection and capture-gated neutron spectrometry applications. Here we investigate the performance of such a material, a composite of plastic scintillator and (6)L(6)(nat) Gd((10)BO(3))(3) : Ce (LGB) crystal shards of as approximate to 1 mm dimension and comprising 1% of the detector by mass. While it is found that the optical propagation properties of this material as currently fabricated are only marginally acceptable for antineutrino detection, its neutron capture identification ability is encouraging. (C) 2011 Elsevier B.V. All rights reserved.
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  • Reactor monitoring using antineutrino detectors

    Bowden, N. S.  

    Nuclear reactors have served as the antineutrino source for many fundamental physics experiments. The techniques developed by these experiments make it possible to use these weakly interacting particles for a practical purpose. T he large flux of antineutrinos that leaves a reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Measurements made with antineutrino detectors could therefore offer an alternative means for verifying the power history and fissile inventory of a reactor as part of International Atomic Energy Agency (IAEA) and/or other reactor safeguards regimes. Several efforts to develop this monitoring technique are underway worldwide.
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  • Large-scale gadolinium-doped water Cherenkov detector for nonproliferation

    Sweany, M.   Bernstein, A.   Bowden, N. S.   Dazeley, S.   Keefer, G.   Svoboda, R.   Tripathi, M.  

    Fission events from Special Nuclear Material (SNM), such as highly enriched uranium or plutonium, can produce simultaneous emission of multiple neutrons and high-energy gamma-rays. The observation of time correlations between any of these particles is a significant indicator of the presence of fissionable material. Cosmogenic processes can also mimic these types of correlated signals. However, if the background is sufficiently low and fully characterized, significant changes in the correlated event rate in the presence of a target of interest constitutes a robust signature of the presence of SNM. Since fission emissions are isotropic, adequate sensitivity to these multiplicities requires a high efficiency detector with a large solid angle with respect to the target. Water Cherenkov detectors are a cost-effective choice when large solid angle coverage is required. In order to characterize the neutron detection performance of large-scale water Cherenkov detectors, we have designed and built a 3.5 kL water Cherenkov-based gamma-ray and neutron detector, and modeled the detector response in Geant4 [1]. We report the position-dependent neutron detection efficiency and energy response of the detector, as well as the basic characteristics of the simulation. (C) 2011 Elsevier B.V. All rights reserved.
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  • Directional fast neutron detection using a time projection chamber

    Bowden, N. S.   Heffner, M.   Carosi, G.   Carter, D.   O'Malley, P.   Mintz, J.   Foxe, M.   Jovanovic, I.  

    Measurement of the three dimensional trajectory and specific ionization of recoil protons using a hydrogen gas time projection chamber provides directional information about incident fast neutrons Here we demonstrate directional fast neutron detection using such a device The wide field of view and excellent gamma rejection that are obtained suggest that this device is well suited to searches for special nuclear materials among other applications (C) 2010 Elsevier B V All rights reserved
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  • Improved fast neutron spectroscopy via detector segmentation

    Bowden, N. S.   Marleau, P.   Steele, J. T.   Mrowka, S.   Aigeldinger, G.   Mengesha, W.  

    Organic scintillators are widely used for fast neutron detection and spectroscopy. Several effects complicate the interpretation of results from detectors based upon these materials. First, fast neutrons will often leave a detector before depositing all of their energy within it. Second, fast neutrons will typically scatter several times within a detector, and there is a non-proportional relationship between the energy of, and the scintillation light produced by, each individual scatter; therefore, there is not a deterministic relationship between the scintillation light observed and the neutron energy deposited. Here we demonstrate a hardware technique for reducing both of these effects. Use of a segmented detector allows for the event-by-event correction of the light yield non-proportionality and for the preferential selection of events with near-complete energy deposition, since these will typically have high segment multiplicities. (C) 2009 Elsevier B.V. All rights reserved.
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  • Observation of neutrons with a Gadolinium doped water Cherenkov detector

    Dazeley, S.   Bernstein, A.   Bowden, N. S.   Svoboda, R.  

    Spontaneous and induced fission in Special Nuclear Material (SNM) such as (235)U and (239)Pu results in the emission of neutrons and high energy gamma-rays. The multiplicities of and time correlations between these particles are both powerful indicators of the presence of fissile material. Detectors sensitive to these signatures are consequently useful for nuclear material monitoring, search, and characterization. In this article, we demonstrate sensitivity to both high energy gamma-rays and neutrons with a water Cherenkov-based detector. Electrons in the detector medium, scattered by gamma-ray interactions, are detected by their Cherenkov light emission. Sensitivity to neutrons is enhanced by the addition of a Gadolinium compound to the water in low concentrations. Cherenkov light is similarly produced by an 8 MeV gamma-ray cascade following neutron capture on the Gadolinium. The large solid angle coverage and high intrinsic efficiency of this detection approach can provide robust and low cost neutron and gamma-ray detection with a single device. (C) 2009 Elsevier B.V. All rights reserved.
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  • Neutron Time Projection Chamber for Nuclear Security and Verification Applications

    Jovanovic, I.   Bowden, N. S.   Carosi, G. P.   Heffner, M.   Roecker, C.  

    Detection of fast neutrons produced by fission is a powerful method for discovering, verifying the presence, or monitoring significant quantities of special nuclear material (SNM) at up to moderate distances. Fast neutrons are relatively rare in the natural background and can be very penetrating, even in situations when the energetic gamma-rays are well shielded. Fast neutrons point in the direction of their source and can thus be considered for use in imaging, a feature desirable for rapid, high-signal-to-noise detection of concealed SNM and for nuclear verification. We describe the development and performance of a prototype neutron time projection chamber (nTPC) and its use for directional neutron detection and high-resolution neutron imaging. The nTPC is based on similar to 0.025 m(3) of a hydrogen-methane mixture and utilizes a readout system with low channel count and is optimized for low event rates. We experimentally demonstrate robust operation, reliable particle identification, event-by-event directional reconstruction over the entire 4 pi solid angle, and insensitivity to gamma-rays. High-efficiency and high-resolution modes of operation based on single and double neutron scatters, respectively, have also been demonstrated.
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  • Performance of a segmented Li-6-loaded liquid scintillator detector for the PROSPECT experiment

    Ashenfelter, J.   Balantekin, A. B.   Band, H. R.   Bass, C. D.   Bergeron, D. E.   Berish, D.   Bowden, N. S.   Brodsky, J. P.   Bryan, C. D.   Telles, A. Bykadorova   Cherwinka, J. J.   Classen, T.   Commeford, K.   Conant, A.   Davee, D.   Deichert, G.   Diwan, M., V   Dolinski, M. J.   Erickson, A.   Foust, B. T.   Gaison, J. K.   Galindo-Uribarri, A.   Gilje, K.   Hackett, B.   Han, K.   Hans, S.   Hansenll, A.   Heeger, K. M.   Heffron, B.   Insler, J.   Jaffe, D. E.   Jones, D.   Kyzylova, O.   Lane, C. E.   Langford, T. J.   LaRosa, J.   Littlejohn, B. R.   Lopez, F.   Caicedo, D. A. Martinez   Matta, J.   McKeown, R. D.   Mendenhall, M. P.   Minock, J.   Mueller, P. E.   Mumm, H. P.   Napolitano, J.   Neilson, R.   Nikkel, J. A.   Norcini, D.   Nour, S.   Pushin, D. A.   Qian, X.   Romero-Romero, E.   Rosero, R.   Surukuchi, P. T.   Trinh, C.   Tyra, M. A.   Wagner, J. M.   White, C.   Wilhelmi, J.   Wise, T.   Yeh, M.   Yen, Y-R   Zhang, A.   Zhang, C.   Zhang, X.  

    This paper describes the design and performance of a 50 liter, two-segment Li-6-loaded liquid scintillator detector that was designed and operated as prototype for the PROSPECT (Precision Reactor Oscillation and Spectrum) Experiment. The two-segment detector was constructed according to the design specifications of the experiment. It features low-mass optical separators, an integrated source and optical calibration system, and materials that are compatible with the Li-6-doped scintillator developed by PROSPECT. We demonstrate a high light collection of 850 +/- 20PE/MeV, an energy resolution of sigma =3D 4.0 +/- 0.2% at 1 MeV, and efficient pulse-shape discrimination of low dE /dx (electronic recoil) and high dE/dx (nuclear recoil) energy depositions. An effective scintillation attenuation length of 85 +/- 3 cm is measured in each segment. The 0.1% by mass concentration of Li-6 in the scintillator results in a measured neutron capture time of tau =3D 42.8 + 0.2 mu s. The long-term stability of the scintillator is also discussed. The detector response meets the criteria necessary for achieving the PROSPECT physics goals and demonstrates features that may find application in fast neutron detection.
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  • Experimental results from an antineutrino detector for cooperative monitoring of nuclear reactors

    Bowden, N. S.   Bernstein, A.   Allen, M.   Brennan, J. S.   Cunningham, M.   Estrada, J. K.   Greaves, C. M. R.   Hagmann, C.   Lund, J.   Mengesha, W.   Weinbeck, T. D.   Winant, C. D.  

    Our collaboration has designed, installed, and operated a compact antineutrino detector at a nuclear power station, for the purpose of monitoring the power and plutonium content of the reactor core. This paper focuses on the basic properties and performance of the detector. We describe the site, the reactor source, and the detector, and provide data that clearly show the expected antineutrino signal. Our data and experience demonstrate that it is possible to operate a simple, relatively small, antineutrino detector near a reactor, in a non-intrusive and unattended mode for months to years at a time, from outside the reactor containment, with no disruption of day-today operations at the reactor site. This unique real-time cooperative monitoring capability may be of interest for the International Atomic Energy Agency (IAEA) reactor safeguards program and similar regimes. (c) 2007 Elsevier B.V. All rights reserved.
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  • First measurement of theta(13) from delayed neutron capture on hydrogen in the Double Chooz experiment

    Abe, Y.   Aberle, C.   dos Anjos, J. C.   Barriere, J. C.   Bergevin, M.   Bernstein, A.   Bezerra, T. J. C.   Bezrukhovn, L.   Blucher, E.   Bowden, N. S.   Buck, C.   Busenitz, J.   Cabrera, A.   Caden, E.   Camilleri, L.   Carr, R.   Cerrada, M.   Chang, P. -J   Chimenti, R.   Classen, T.   Collin, A. P.   Conover, E.   Conrad, J. M.   Crespo-Anadon, J. I.   Crum, K.   Cucoanes, A.   Damon, E.   Dawson, J. V.   Dazeley, S.   Dietrich, D.   Djurcic, Z.   Dracos, M.   Durand, V.   Ebert, J.   Efremenko, Y.   Elnimr, M.   Erickson, A.   Etenko, A.   Fallot, M.   Fechner, M.   von Feilitzsch, F.   Felde, J.   Fernandes, S. M.   Fischer, V.   Franco, D.   Franke, A. J.   Franke, M.   Furuta, H.   Gama, R.   Gil-Botella, I.   Giot, L.   Goeger-Neff, M.   Gonzalez, L. F. G.   Goodenough, L.   Goodman, M. C.   Goon, J. T. M.   Greiner, D.   Haag, N.   Habib, S.   Hagner, C.   Hara, T.   Hartmann, F. X.   Haser, J.   Hatzikoutelis, A.   Hayakawa, T.   Hofmann, M.   Horton-Smith, G. A.   Hourlier, A.   Ishitsuka, M.   Jochum, J.   Jollet, C.   Jones, C. L.   Kaether, T. F.   Kalousis, L. N.   Kamyshkov, Y.   Kaplan, D. M.   Kawasaki, T.   Keefer, G.   Kemp, E.   De Kerret, H.   Konno, T.   Kryn, D.   Kuze, M.   Lachenmaier, T.   Lane, C. E.   Langbrandtner, C.   Lasserre, T.   Letourneau, A.   Lhuillier, D.   Lima, H. P., Jr.   Lindner, M.   Lopez-Castano, J. M.   LoSecco, J. M.   Lubsandorzhiev, B. K.   Lucht, S.   McKee, D.   Maeda, J.   Maesano, C. N.   Mariani, C.   Maricic, J.   Martino, J.   Matsubara, T.   Mention, G.   Meregaglia, A.   Meyer, M.   Miletic, T.   Milincic, R.   Miyata, H.   Mueller, Th. A.   Nagasaka, Y.   Nakajima, K.   Novella, P.   Obolensky, M.   Oberauer, L.   Onillon, A.   Osborn, A.   Ostrovskiy, I.   Palomares, C.   Pepe, I. M.   Perasso, S.   Perrin, P.   Pfahler, P.   Porta, A.   Potzel, W.   Pronost, G.   Reichenbacher, J.   Reinhold, B.   Remoto, A.   Roehling, M.   Roncin, R.   Roth, S.   Rybolt, B.   Sakamoto, Y.   Santorelli, R.   Sato, F.   Schoenert, S.   Schoppmann, S.   Schwetz, T.   Shaevitz, M. H.   Shimojima, S.   Shrestha, D.   Sida, J. -L.   Sinev, V.   Skorokhvatov, M.   Smith, E.   Spitz, J.   Stahl, A.   Stancu, I.   Stokes, L. F. F.   Strait, M.   Stueken, A.   Suekane, K.   Sukhotin, S.   Sumiyoshi, T.   Sun, Y.   Svoboda, R.   Terao, K.   Tonazzo, A.   Toups, M.   Thi, H. H. Trinh   Valdiviesso, G.   Veyssiere, C.   Wagner, S.   Watanabe, H.   White, B.   Wiebusch, C.   Winslow, L.   Worcester, M.   Wurm, M.   Yermia, F.   Zimmer, V.  

    The Double Chooz experiment has determined the value of the neutrino oscillation parameter theta(13) from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds sin(2) 2 theta(13) = 0.097 +/- 0.034 (stat.) +/- 0.034 (syst.), excluding the no-oscillation hypothesis at 2.0 sigma. This result is consistent with previous measurements of sin(2) 2 theta(13). (c) 2013 Elsevier B.V. All rights reserved.
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  • Observation of the isotopic evolution of pressurized water reactor fuel using an antineutrino detector

    Bowden, N. S.   Bernstein, A.   Dazeley, S.   Svoboda, R.   Misner, A.   Palmer, T.  

    By operating an antineutrino detector of simple design during several fuel cycles, we observed long term changes in antineutrino flux that result from the isotopic evolution of a commercial pressurized water reactor. Measurements made with simple antineutrino detectors of this kind offer an alternative means for verifying fissile inventories at reactors, as part of International Atomic Energy Agency and other reactor safeguards regimes.
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