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Search Results: 1 - 10 of 471678 matches for " N. S. Bowden "
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Reactor monitoring and safeguards using antineutrino detectors
N. S. Bowden
Physics , 2008, DOI: 10.1088/1742-6596/136/2/022008
Abstract: 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 very weakly interacting particles for a practical purpose. The 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 reactors, as part of International Atomic Energy Agency (IAEA) and other reactor safeguards regimes. Several efforts to develop this monitoring technique are underway across the globe.
Investigation of Large LGB Detectors for Antineutrino Detection
P. Nelson,N. S. Bowden
Physics , 2011, DOI: 10.1016/j.nima.2011.09.027
Abstract: 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 $^6$Li$_6^{nat}$Gd$(^{10}$BO$_{3})_{3}$:Ce (LGB) crystal shards of ~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.
A Note on Neutron Capture Correlation Signals, Backgrounds, and Efficiencies
N. S. Bowden,M. Sweany,S. Dazeley
Physics , 2012, DOI: 10.1016/j.nima.2012.07.005
Abstract: 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.
Observation of Neutrons with a Gadolinium Doped Water Cerenkov Detector
S. Dazeley,A. Bernstein,N. S. Bowden,R. Svoboda
Physics , 2008, DOI: 10.1016/j.nima.2009.03.256
Abstract: Spontaneous and induced fission in Special Nuclear Material (SNM) such as 235U and 239Pu 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 Cerenkov based detector. Electrons in the detector medium, scattered by gamma-ray interactions, are detected by their Cerenkov light emission. Sensitivity to neutrons is enhanced by the addition of a gadolinium compound to the water in low concentrations. Cerenkov 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.
Monitoring the Thermal Power of Nuclear Reactors with a Prototype Cubic Meter Antineutrino Detector
A. Bernstein,N. S. Bowden,A. Misner,T. Palmer
Physics , 2008, DOI: 10.1063/1.2899178
Abstract: In this paper, we estimate how quickly and how precisely a reactor's operational status and thermal power can be monitored over hour to month time scales, using the antineutrino rate as measured by a cubic meter scale detector. Our results are obtained from a detector we have deployed and operated at 25 meter standoff from a reactor core. This prototype can detect a prompt reactor shutdown within five hours, and monitor relative thermal power to three percent within seven days. Monitoring of short-term power changes in this way may be useful in the context of International Atomic Energy Agency's (IAEA) Reactor Safeguards Regime, or other cooperative monitoring regimes.
Improved Fast Neutron Spectroscopy via Detector Segmentation
N. S. Bowden,P. Marleau,J. T. Steele,S. Mrowka,G. Aigeldinger,W. Mengesha
Physics , 2009, DOI: 10.1016/j.nima.2009.07.061
Abstract: 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.
Observation of the Isotopic Evolution of Pressurized Water Reactor Fuel Using an Antineutrino Detector
N. S. Bowden,A. Bernstein,S. Dazeley,R. Svoboda,A. Misner,T. Palmer
Physics , 2008, DOI: 10.1063/1.3080251
Abstract: By operating an antineutrino detector of simple design during several fuel cycles, we have observed long term changes in antineutrino flux that result from the isotopic evolution of a commercial Pressurized Water Reactor (PWR). 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 (IAEA) and other reactor safeguards regimes.
Large-scale Gadolinium-doped Water Cerenkov Detector for Non-Proliferation
M. Sweany,A. Bernstein,N. S. Bowden,S. Dazeley,G. Keefer,R. Svoboda,M. Tripathi
Physics , 2011,
Abstract: 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 Cerenkov 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 Cerenkov detectors, we have designed and built a 3.5 kL water Cerenkov-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.
Coaxial Wire Measurements In NLC Accelerating Structures
N. Baboi,R. M. Jones,G. B. Bowden,V. Dolgashev,S. G. Tantawi,J. W. Wang
Physics , 2002,
Abstract: The coaxial wire method provides an experimental way of measuring wake fields without the need for a particle beam. A special setup has been designed and is in the process of being fabricated at SLAC to measure the loss factors and synchronous frequencies of dipole modes in both traveling and standing wave structures for the Next Linear Collider (NLC). The method is described and predictions based on electromagnetic field simulations are discussed
Transverse Impedance Bench Measurements in NLC/JLC Accelerating Structures
N. Baboi,G. B. Bowden,R. M. Jones,S. G. Tantawi,J. R. Lewandowski
Physics , 2003,
Abstract: The wire method is a more rapid and less costly method to measure impedances of RF components compared to methods using a beam. A setup using a single displaced wire to excite and measure transverse resonant modes in accelerating structures for the Next Linear Collider/ Japanese Linear Collider (NLC/JLC) has been built. The RF signal is coupled into and out of the structure using two matching sections with a broadband frequency from 11 to 18 GHz. Their contribution to the scattering parameter is minimized by a calibration technique. A standing wave structure has been measured. Difficulties in accurately predicting the modal loss factors were encountered related to the approximations made and to experimental issues. The measurements are presented and comparisons with simulations are made.
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