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A second-generation cosmic axion experiment

Description: An experiment is described to detect dark matter axions trapped in the halo of our galaxy. Galactic axions are converted into microwave photons via the Primakoff effect in a static background field provided by a superconducting magnet. The photons are collected in a high Q microwave cavity and detected by a low noise receiver. The axion mass range accessible by this experiment is 1.3 {minus} 13 {mu}eV. The expected sensitivity will be roughly 50 times greater than achieved by previous experimen… more
Date: May 1, 1995
Creator: Hagmann, C.; Stoeffl, W. & van Bibber, K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Search for pseudoscalar cold dark matter

Description: AH dynamical evidence points to the conclusion that the predominant form of matter in the universe is in a non-luminous form. Furthermore, large scale deviations from uniform Hubble flow, and the recent COBE reports of inhomogeneities in the cosmic microwave background strongly suggest that we live in an exactly closed universe. If this is true, then ordinary baryonic matter could only be a minority component (10% at most) of the missing mass, and that what constitutes the majority of the dark … more
Date: May 29, 1992
Creator: van Bibber, K.; Stoeffl, W. & Collaborators, LLNL
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Trapped macroparticles in electron storage rings

Description: Sudden drops of the beam lifetime ascribed to the capture of positively charged macroparticles (`dust`) are observed at many high-energy electron storage rings. A trapped macroparticle has a certain thermal lifetime due to energy transfer from the beam; the interplay of different ionizing and discharging processes gives rise to an equilibrium charge. The beam lifetime is reduced by bremsstrahlung both in the field of the atomic nuclei and in the macroscopic field of the highly charged dust part… more
Date: June 1, 1995
Creator: Zimmermann, F.; Seeman, J. T.; Zolotorev, M. & Stoeffl, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Dual-phase argon ionization detector for measurement of coherent elastic neutrino scattering and medium-energy nuclear recoils

Description: We propose to build and deploy a 10-kg dual-phase argon ionization detector for the detection of coherent neutrino-nucleus scattering, which is described by the reaction; (V) + (Z,N) {yields} (v) + (Z,N). Our group would be the first to make this measurement. Its detection would validate (or refute) central tenets of the Standard Model. The existence of this process is also relevant to astrophysics, where coherent neutrino scattering is assumed to impede energy transport within neutron stars. W… more
Date: September 13, 2006
Creator: Winant, C D; Bernstein, A; Hagmann, C; Madden, N & Stoeffl, W
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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High intensity positron program at LLNL

Description: Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration wit… more
Date: September 23, 1998
Creator: Asoka-Kumar, P.; Howell, R.H. & Stoeffl, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Materials analysis using positron beam lifetime spectroscopy

Description: We are using a defect analysis capabilities based on two positron beam lifetime spectrometers: the first is based on a 3 MeV electrostatic accelerator and the second on our high current linac beam. The high energy beam lifetime spectrometer is routinely used to perform positron lifetime analysis with a 3 MeV positron beam on thick sample specimens. It is being used for bulk sample analysis and analysis of samples encapsulated in controlled environments for in situ measurements. A second, low en… more
Date: November 12, 1998
Creator: Hartley, J.; Howell, R. H., Asoka-Kumar, P.; Sterne, P. & Stoeffl, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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High current pulsed positron microprobe

Description: We are developing a low energy, microscopically focused, pulsed positron beam for defect analysis by positron lifetime spectroscopy to provide a new defect analysis capability at the 10{sup 10} e{sup +}s{sup -l} beam at the Lawrence Livermore National Laboratory electron linac. When completed, the pulsed positron microprobe will enable defect specific, 3-dimensional maps of defect concentrations with sub-micron resolution of defect location. By coupling these data with first principles calculat… more
Date: May 1, 1997
Creator: Howell, R. H.; Stoeffl, W.; Kumar, A.; Sterne, P. A.; Cowan, T. E. & Hartley, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Kinematically Beamed, Low Energy Pulsed Neutron Source for Active Interrogation

Description: We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of SNM (Special Nuclear Materials) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals, (1) Energy discrimination allows us to measure the prompt fast fission neutrons produced while the interrogation beam is on; (2) Neutr… more
Date: October 7, 2004
Creator: Dietrich, D; Hagmann, C; Kerr, P; Nakae, L; Rowland, M; Snyderman, N et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Proposal for First-Ever Measurement of Coherent Neutrino-Nucleus Scattering

Description: We propose to build and deploy a 10-kg dual-phase argon ionization detector for the detection of coherent neutrino-nucleus scattering, which is described by the reaction; {nu} + (Z,N) {yields} {nu} + (Z,N), where {nu} is the scattering neutrino, and (Z,N) is the target nucleus of atomic number Z and neutron number N. Its detection would validate central tenets of the Standard Model. We have built a gas-phase argon ionization detector to determine the feasibility of measuring the small recoil en… more
Date: February 5, 2008
Creator: Winant, C D; Bernstein, A; Foxe, M P; Hagmann, C A; Jovanovic, I; Kazkaz, K M et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Radiochemical Analysis of Gaseous Samples (RAGS) Apparatus for Nuclear Diagnostics at the National Ignition Facility

Description: The RAGS (Radiochemical Analysis of Gaseous Samples) diagnostic apparatus was recently installed at the National Ignition Facility. Following a NIF shot, RAGS is used to pump the gas load from the NIF chamber for purification and isolation of the noble gases. After collection, the activated gaseous species are counted via gamma spectroscopy for measurement of the capsule areal density and fuel-ablator mix. Collection efficiency was determined by injecting a known amount of {sup 135}Xe into the … more
Date: May 11, 2012
Creator: Shaughnessy, D A; Velsko, C A; Jedlovec, D R; Yeamans, C B; Moody, K J; Tereshatov, E et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nondestructive Neutron And Gamma-Ray Technologies Applied To GNEP And Safeguards

Description: In recent years, LLNL has developed methods for diagnosing significant quantities of special nuclear material (SNM). Homeland security problems have recently focused our attention on detection of shielded highly enriched uranium (HEU), which is a weak signal problem. Current and advanced safeguards applications will require working in the opposite extreme of strong but buried signals. We will review some of the technologies that have been developed at LLNL for homeland security applications and… more
Date: June 27, 2007
Creator: Dougan, A D; Snyderman, N; Ham, Y; Nakae, L; Dietrich, D; Kerr, P et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Active Detection of Small Quantities of Shielded Highly-Enriched Uranium Using Low-Dose 60-keV Neutron Interrogation

Description: Active interrogation with low-energy neutrons provides a search technique for shielded highly-enriched uranium. We describe the technique and show initial results using a low-dose 60 keV neutron beam. This technique produces a clear induced fission signal in the presence of small quantities of {sup 235}U. The technique has been validated with low-Z and high-Z shielding materials. The technique uses a forward-directed beam of 60 keV neutrons to induce fission in {sup 235}U. The induced fission p… more
Date: August 16, 2006
Creator: Kerr, P.; Rowland, M.; Dietrich, D.; Stoeffl, W.; Wheeler, B.; Nakae, L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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In-beam Spectroscopy Using the (t,p) Reaction: Recent Results Near A = 100

Description: Charged particle spectroscopy using the (t,p) reaction has been employed for more than two decades to study the low-energy structure of nuclei. This reaction has contributed significantly to the elucidation of single-particle and collective phenomena for neutron rich nuclei in virtually every mass region. We have begun to use the (t,p) reaction in conjunctionuclei with in-beam ..gamma..-ray and conversion-electron spectroscopy to bring additional understanding to low-energy nuclear structure. I… more
Date: September 4, 1985
Creator: Henry, E. A.; Estep, R. J.; Meyer, R. A.; Kantele, J.; Decman, D. J.; Mann, L. G. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Status of the large-scale dark-matter axion search

Description: If axions constitute the dark matter of our galactic halo they can be detected by their conversion into monochromatic microwave photons in a high-Q microwave cavity permeated by a strong magnetic field. A large-scale experiment is under construction at LLNL to search for halo axions in the mass range 1.3 - 13 {mu}eV, where axions may constitute closure density of the universe. The search builds upon two pilot efforts at BNL and the University of Florida in the late 1980`s, and represents a larg… more
Date: September 1, 1994
Creator: Van Bibber, K.; Hagmann, C.; Stoeffl, W.; Daw, E.; Rosenberg, L.; Sikivie, P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Study of Positronium in Low-k Dielectric Films by means of 2D-Angular Correlation Experiments at a High-Intensity Slow-Positron Beam

Description: Depth-resolved measurements of the two-dimensional angular correlation of annihilation radiation (2D-ACAR) were performed at the high-intensity slow-positron beam of Lawrence Livermore National Laboratory. We studied the formation of positronium in thin films of methyl-silsesquioxane (MSSQ) spin-on glass containing open-volume defects in the size of voids. Samples with different average void sizes were investigated and positronium formation could be found in all cases. The width of the angular … more
Date: June 20, 2001
Creator: Gessmann, T; Petkov, M P; Weber, M H; Lynn, K G; Rodbell, K P; Asoka-Kumar, P et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Radiochemistry as a (rho)R Diagnostic with the RAGS Gas Collection System

Description: Radiochemical diagnostic techniques such as gas-phase capsule debris analysis may prove to be successful methods for establishing the success or failure of ignition experiments at the National Ignition Facility (NIF). Samples in the gas phase offer the most direct method of collection by simply pumping out the large target chamber following a NIF shot. The target capsules will be prepared with dopants which will produce radioactive noble gas isotopes upon activation with neutrons. We have desig… more
Date: May 21, 2010
Creator: Nelson, S. L.; Shaughnessy, D. A.; Schneider, D. H.; Stoeffl, W.; Moody, K. J.; Cerjan, C. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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An Improved RF Cavity Search for Halo Axions

Description: The axion is a hypothetical elementary particle and cold dark matter candidate. In this RF cavity experiment, halo axions entering a resonant cavity immersed in a static magnetic field convert into microwave photons, with the resulting photons detected by a low-noise receiver. The ADMX Collaboration presents new limits on the axion-to-photon coupling and local axion dark matter halo mass density from a RF cavity axion search in the axion mass range 1.9-2.3 {micro}eV, broadening the search range… more
Date: November 11, 2003
Creator: Asztalos, S.; Bradley, R.; Duffy, L.; Hagmann, C.; Kinion, D.; Moltz, D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Design and Construction of a Gamma Reaction History Diagnostic for the National Ignition Facility

Description: Gas Cherenkov detectors have been used to convert fusion gammas into photons to achieve gamma reaction history (GRH) measurements. These gas detectors include a converter, pressurized gas volume, relay optics, and a photon detector. A novel design for the National Ignition Facility (NIF) using 90º Off-Axis Parabolic mirrors efficiently collects signal from fusion gammas with 8-ps time dispersion.1 Fusion gammas are converted to Compton electrons, which generate broadband Cherenkov light (our re… more
Date: June 5, 2009
Creator: R.M. Malone, B.C. Cox, B.C. Frogget, M.I. Kaufman, T.W. Tunnell; H.W. Herrmann, S.C. Evans, J.M. Mack, C.S. Young & Stoeffl, W.
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Partner: UNT Libraries Government Documents Department
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Gamma Reaction History for the NIF

Description: Bang time and reaction history measurements are fundamental components of diagnosing ICF implosions and will be essential contributors to diagnosing attempts at ignition on the National Ignition Facility (NIF). Fusion gammas provide a direct measure of fusion interaction rate without being compromised by Doppler spreading. Gamma-based gas Cherenkov detectors that convert fusion gamma rays to optical Cherenkov photons for collection by fast recording systems have been developed and fielded at Om… more
Date: June 5, 2009
Creator: Herrmann, H. W.; Evans, S. C.; Kim, Y.; Mack, J. M.; Young, C. S.; Cox, B. C. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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