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Search Results: 1 - 10 of 401374 matches for " M. Sweany "
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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.
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.
Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors
M. Sweany,A. Bernstein,S. Dazeley,J. Dunmore,J. Felde,R. Svoboda,M. Tripathi
Physics , 2011, DOI: 10.1016/j.nima.2011.10.064
Abstract: Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 $\pm$ 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 $\pm$ 0.03 for Carbostyril-124, and 1.20 $\pm$ 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
M. Szydagis,N. Barry,K. Kazkaz,J. Mock,D. Stolp,M. Sweany,M. Tripathi,S. Uvarov,N. Walsh,M. Woods
Physics , 2011,
Abstract: A comprehensive model for explaining scintillation yield in liquid xenon is introduced. We unify various definitions of work function which abound in the literature and incorporate all available data on electron recoil scintillation yield. This results in a better understanding of electron recoil, and facilitates an improved description of nuclear recoil. An incident gamma energy range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are incorporated into this heuristic model. We show results from a Geant4 implementation, but because the model has a few free parameters, implementation in any simulation package should be simple. We use a quasi-empirical approach, with an objective of improving detector calibrations and performance verification. The model will aid in the design and optimization of future detectors. This model is also easy to extend to other noble elements. In this paper we lay the foundation for an exhaustive simulation code which we call NEST (Noble Element Simulation Technique).
A search for cosmogenic production of $β$-neutron emitting radionuclides in water
S. Dazeley,M. Askins,M. Bergevin,A. Bernstein,N. S. Bowden,P. Jaffke,S. D. Rountree,T. M. Shokair,M. Sweany
Physics , 2015,
Abstract: Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of $\beta$-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the $\beta$-neutron measurement, we also provide a first look at isolating single-$\beta$ producing radionuclides following showering muons as a check of the detection capabilities of WATCHBOY. The data taken over $207$ live days indicates a $^{9}$Li production yield upper limit of $1.9\times10^{-7}\mu^{-1}g^{-1}\mathrm{cm}^2$ at $\sim400$ meters water equivalent (m.w.e.) overburden at the $90\%$ confidence level. In this work the $^{9}$Li signal in WATCHBOY was used as a proxy for the combined search for $^{9}$Li and $^{8}$He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.
Towards energy resolution at the statistical limit from a negative ion time projection chamber
Peter Sorensen,Mike Heffner,Adam Bernstein,Josh Renner,Melinda Sweany
Physics , 2012, DOI: 10.1016/j.nima.2012.05.078
Abstract: We make a proof-of-principle demonstration that improved energy resolution can be obtained in a negative-ion time projection chamber, by individually counting each electron produced by ionizing radiation.
The Physics and Nuclear Nonproliferation Goals of WATCHMAN: A WAter CHerenkov Monitor for ANtineutrinos
M. Askins,M. Bergevin,A. Bernstein,S. Dazeley,S. T. Dye,T. Handler,A. Hatzikoutelis,D. Hellfeld,P. Jaffke,Y. Kamyshkov,B. J. Land,J. G. Learned,P. Marleau,C. Mauger,G. D. Orebi Gann,C. Roecker,S. D. Rountree,T. M. Shokair,M. B. Smy,R. Svoboda,M. Sweany,M. R. Vagins,K. A. van Bibber,R. B. Vogelaar,M. J. Wetstein,M. Yeh
Physics , 2015,
Abstract: This article describes the physics and nonproliferation goals of WATCHMAN, the WAter Cherenkov Monitor for ANtineutrinos. The baseline WATCHMAN design is a kiloton scale gadolinium-doped (Gd) light water Cherenkov detector, placed 13 kilometers from a civil nuclear reactor in the United States. In its first deployment phase, WATCHMAN will be used to remotely detect a change in the operational status of the reactor, providing a first- ever demonstration of the potential of large Gd-doped water detectors for remote reactor monitoring for future international nuclear nonproliferation applications. During its first phase, the detector will provide a critical large-scale test of the ability to tag neutrons and thus distinguish low energy electron neutrinos and antineutrinos. This would make WATCHMAN the only detector capable of providing both direction and flavor identification of supernova neutrinos. It would also be the third largest supernova detector, and the largest underground in the western hemisphere. In a follow-on phase incorporating the IsoDAR neutrino beam, the detector would have world-class sensitivity to sterile neutrino signatures and to non-standard electroweak interactions (NSI). WATCHMAN will also be a major, U.S. based integration platform for a host of technologies relevant for the Long-Baseline Neutrino Facility (LBNF) and other future large detectors. This white paper describes the WATCHMAN conceptual design,and presents the results of detailed simulations of sensitivity for the project's nonproliferation and physics goals. It also describes the advanced technologies to be used in WATCHMAN, including high quantum efficiency photomultipliers, Water-Based Liquid Scintillator (WbLS), picosecond light sensors such as the Large Area Picosecond Photo Detector (LAPPD), and advanced pattern recognition and particle identification methods.
Intraspecific Aflatoxin Inhibition in Aspergillus flavus Is Thigmoregulated, Independent of Vegetative Compatibility Group and Is Strain Dependent
Changwei Huang, Archana Jha, Rebecca Sweany, Catherine DeRobertis, Kenneth E. Damann
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023470
Abstract: Biological control of preharvest aflatoxin contamination by atoxigenic stains of Aspergillus flavus has been demonstrated in several crops. The assumption is that some form of competition suppresses the fungus's ability to infect or produce aflatoxin when challenged. Intraspecific aflatoxin inhibition was demonstrated by others. This work investigates the mechanistic basis of that phenomenon. A toxigenic and atoxigenic isolate of A. flavus which exhibited intraspecific aflatoxin inhibition when grown together in suspended disc culture were not inhibited when grown in a filter insert-plate well system separated by a .4 or 3 μm membrane. Toxigenic and atoxigenic conidial mixtures (50:50) placed on both sides of these filters restored inhibition. There was ~50% inhibition when a 12 μm pore size filter was used. Conidial and mycelial diameters were in the 3.5–7.0 μm range and could pass through the 12 μm filter. Larger pore sizes in the initially separated system restored aflatoxin inhibition. This suggests isolates must come into physical contact with one another. This negates a role for nutrient competition or for soluble diffusible signals or antibiotics in aflatoxin inhibition. The toxigenic isolate was maximally sensitive to inhibition during the first 24 hrs of growth while the atoxigenic isolate was always inhibition competent. The atoxigenic isolate when grown with a green fluorescent protein (GFP) toxigenic isolate failed to inhibit aflatoxin indicating that there is specificity in the touch inhibiton. Several atoxigenic isolates were found which inhibited the GFP isolate. These results suggest that an unknown signaling pathway is initiated in the toxigenic isolate by physical interaction with an appropriate atoxigenic isolate in the first 24 hrs which prevents or down-regulates normal expression of aflatoxin after 3–5 days growth. We suspect thigmo-downregulation of aflatoxin synthesis is the mechanistic basis of intraspecific aflatoxin inhibition and the major contributor to biological control of aflatoxin contamination.
The LUX Prototype Detector: Heat Exchanger Development
D. S. Akerib,X. Bai,S. Bedikian,A. Bernstein,A. Bolozdynya,A. Bradley,S. Cahn,D. Carr,J. J. Chapman,K. Clark,T. Classen,A. Curioni,C. E. Dahl,S. Dazeley,L. deViveiros,M. Dragowsky,E. Druszkiewicz,S. Fiorucci,R. J. Gaitskell,C. Hall,C. Faham,B. Holbrook,L. Kastens,K. Kazkaz,J. Kwong,R. Lander,D. Leonard,D. Malling,R. Mannino,D. N. McKinsey,D. Mei,J. Mock,M. Morii,J. Nikkel,P. Phelps,T. Shutt,W. Skulski,P. Sorensen,J. Spaans,T. Steigler,R. Svoboda,M. Sweany,J. Thomson,M. Tripathi,N. Walsh,R. Webb,J. White,F. L. H. Wolfs,M. Woods,C. Zhang
Physics , 2012, DOI: 10.1016/j.nima.2013.01.036
Abstract: The LUX (Large Underground Xenon) detector is a two-phase xenon Time Projection Chamber (TPC) designed to search for WIMP-nucleon dark matter interactions. As with all noble element detectors, continuous purification of the detector medium is essential to produce a large ($>$1ms) electron lifetime; this is necessary for efficient measurement of the electron signal which in turn is essential for achieving robust discrimination of signal from background events. In this paper we describe the development of a novel purification system deployed in a prototype detector. The results from the operation of this prototype indicated heat exchange with an efficiency above 94% up to a flow rate of 42 slpm, allowing for an electron drift length greater than 1 meter to be achieved in approximately two days and sustained for the duration of the testing period.
Status of the LUX Dark Matter Search
S. Fiorucci,D. S. Akerib,S. Bedikian,A. Bernstein,A. Bolozdynya,A. Bradley,D. Carr,J. Chapman,K. Clark,T. Classen,A. Curioni,E. Dahl,S. Dazeley,L. de Viveiros,E. Druszkiewicz,R. Gaitskell,C. Hall,C. Hernandez Faham,B. Holbrook,L. Kastens,K. Kazkaz,R. Lander,K. Lesko,D. Malling,R. Mannino,D. McKinsey,D. Mei,J. Mock,J. Nikkel,P. Phelps,U. Schroeder,T. Shutt,W. Skulski,P. Sorensen,J. Spaans,T. Stiegler,R. Svoboda,M. Sweany,J. Thomson,J. Toke,M. Tripathi,N. Walsh,R. Webb,J. White,F. Wolfs,M. Woods,C. Zhang
Physics , 2009, DOI: 10.1063/1.3327777
Abstract: The Large Underground Xenon (LUX) dark matter search experiment is currently being deployed at the Homestake Laboratory in South Dakota. We will highlight the main elements of design which make the experiment a very strong competitor in the field of direct detection, as well as an easily scalable concept. We will also present its potential reach for supersymmetric dark matter detection, within various timeframes ranging from 1 year to 5 years or more.
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