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Imprinted spiral structures as neutron polarizers.

Description: Neutron diffraction from magnetic spiral structures is governed by strong selection rules for the polarization of the outgoing beam. When the sample is entirely of one chirality--for instance a right handed spiral--the neutrons diffracted by some Bragg reflections are fully polarized. While the scattering theory has been formulated long ago, attempts to controllably modify the population of left handed and right handed spiral domains in natural magnetic structures (which for instance occur in some rare earth metals) have been largely unsuccessful. In contrast, we have been able to imprint helical magnetic structures in La/Fe multilayers (each layer approximately 30 {angstrom} thick) simply by rotating the growing sample in a weak external field (30e). A first estimate is given of the efficiency of these multilayers as polarizers of neutron beams.
Date: October 7, 1998
Creator: Lohstroh, W.
Partner: UNT Libraries Government Documents Department

Ten years of sourcery at CAMS/LLNL - evolution of a Cs ion source

Description: The present performance and status of the LLNL AMS ion source and the rationale for the series of changes which led to the present design are discussed.
Date: October 7, 1999
Creator: Roberts, M & Southon, J
Partner: UNT Libraries Government Documents Department

Simulations of laser-initiated stress waves

Description: We present a study of the short-time scale (< 250 ns) fluid dynamic response of water to a fiber-delivered laser pulse of variable energy and spatial profile. The laser pulse was deposited on a stress confinement time scale. The spatial profile was determined by the fiber core radius r (110 and 500 microns) and the water absorption coefficient {mu}{sub 2} (200 and 50 l/cm). Considering 2D cylindrical symmetry, the combination of fiber radius and absorption coefficient parameters can be characterized as near planar (1{mu}{sub 2} greater than r), symmetric (1/{mu}{sub 2}=r), and side-directed (1/{mu}{sub 2} less than r). The spatial profile study shows how the stress wave various as a function of geometry. For example, relatively small absorption coefficients can result in side-propagating shear and tensile fields.
Date: March 7, 1997
Creator: Maitland, D.J.; Celliers, P.; Amendt, P.; Da Silva, L.; London, R.A.; Matthews, D. et al.
Partner: UNT Libraries Government Documents Department

LEU conversion status of US research reactors, September 1996

Description: This paper summarizes the conversion status of research and test reactors in the United States from the use of fuels containing highly- enriched uranium (HEU, greater than or equal to 20%) to the use of fuels containing low-enriched uranium (LEU, < 20%). Estimates of the uranium densities required for conversion are made for reactors with power levels greater than or equal to 1 MW that are not currently involved in the LEU conversion process.
Date: October 7, 1996
Creator: Matos, J.E.
Partner: UNT Libraries Government Documents Department

Fabrication of MEMS Devices by Powder-Filling into DXRL-Formed Molds

Description: We have developed a variety of processes for fabricating components for micro devices based on deep x-ray lithography (DXRL). Although the techniques are applicable to many materials, we have demonstrated them using hard (Nd{sub 2}Fe{sub 14}B) and soft (Ni-Zn ferrite) magnetic materials because of the importance of these materials in magnetic micro-actuators and other devices and because of the difficulty fabricating them by other means. The simplest technique involves pressing a mixture of magnetic powder and a binder into a DXRL-formed mold. In the second technique, powder is pressed into the mold and then sintered to densify. The other two processes involve pressing at high temperature either powder or a dense bulk material into a ceramic mold that was previously made using a DXRL mold. These techniques allow arbitrary 2-dimensional shapes to be made 10 to 1000 micrometers thick with in-plane dimensions as small as 50 micrometers and dimensional tolerances in the micron range. Bonded isotropic Nd{sub 2}Fe{sub 14}B micromagnets made by these processes had an energy product of 7 MGOe.
Date: January 7, 1999
Creator: Christenson, T.; Garino, T.J. & Venturini, E.
Partner: UNT Libraries Government Documents Department

Resolution of the nuclear criticality safety issue for the Hanford site high-level waste tanks

Description: This paper describes the approach used to resolve the Nuclear Criticality Safety Issue for the Hanford Site high-level waste tanks. Although operational controls have been in place at the Hanford Site throughout its operating life to minimize the amount of fissile material discarded as waste, estimates of the total amount of plutonium that entered the waste tanks range from 500 to 1,000 kg. Nuclear criticality safety concerns were heightened in 1991 based on a review of waste analysis results and a subsequent U.S. Department of Energy 1399 review of the nuclear criticality program. Although the DOE review team concluded that there was no imminent risk of a criticality at the Hanford Site tank farms, the team also stated its concern regarding the lack of definitive knowledge of the fissile material inventory and distribution within the waste tanks and the lack of sufficient management support for the overall criticality safety program. An in-depth technical review of the nuclear criticality safety of the waste tanks was conducted to develop a defensible technical basis to ensure that waste tanks are subcritical. The review covered all relevant aspects of nuclear criticality safety including neutronics and chemical and physical phenomena of the waste form under aging waste conditions as well as during routine waste management operations. This paper provides a review of the technical basis to support the conclusion that given current plutonium inventories and operating conditions, a nuclear criticality is incredible. The DOE has been requested to close the Nuclear Criticality Safety Issue. The Defense Nuclear Facilities Safety Board is currently reviewing the technicalbasis.
Date: January 7, 1997
Creator: Bratzel, D.R.
Partner: UNT Libraries Government Documents Department

Parameter identification and on-line estimation for reduced kinetic model

Description: The base hydrolysis process for the destruction of energetic or explosive materials results is a high pH hydrolysate solution with reaction products that include a series of carboxylic acid salts, glycolates, amines, and nitrates. The hydrolysate solutions obtained from this process contain from two to ten wt% of organic carbon and nitrogen compounds that must be further treated before disposal. Hydrothermal oxidation at elevated temperatures (450 C) and pressure (14,000 psi) was selected as the treatment process for the hydrolysate solutions obtained from hydrolysis of the high explosive PBX 9404 at the Department of Energy Pantex facility in Amarillo, Texas. In this work, the authors describe the use of receding horizon identification and estimation techniques to determine the model parameters for a reduced kinetic model describing the oxidation-reduction reactions in a hydrothermal oxidation reactor. This model is used in a model predictive controller that minimizes the total aqueous nitrogen in the hydrothermal oxidation reactor effluent.
Date: August 7, 1998
Creator: Littel, J.D.; Muske, K.R.; Del`Orco, P.C.; Le, L.A. & Flesner, R.L.
Partner: UNT Libraries Government Documents Department

Cosmic Closure: Relating the Ultimate Fate of Massive Stars and the Ultimate Fate of the Universe

Description: We give a brief overview of the status of core collapse supernova modeling, particularly as it pertains to predictions of neutrino signatures for the next galactic or near extragalactic supernova. We also consider the implications of neutrino mass for both the supernova mechanism and neutrino signature predictions.
Date: September 7, 1998
Creator: Bruenn, S.W. & Mezzacappa, A.
Partner: UNT Libraries Government Documents Department

Recent Progress on the Standardized DOE Spent Nuclear Fuel Canister

Description: The Department of Energy (DOE) has developed a set of containers for the handling, interim storage, transportation, and disposal in the national repository of DOE spent nuclear fuel (SNF). This container design, referred to as the standardized DOE SNF canister or standardized canister, was developed by the Department's National Spent Nuclear Fuel Storage Program (NSNFP) working in conjunction with the Office of Civilian Radioactive Waste Management (OCRWM) and the DOE spent fuel sites. This canister had to have a standardized design yet be capable of accepting virtually all of the DOE SNF, be placed in a variety of storage and transportation systems, and still be acceptable to the repository. Since specific design details regarding the storage, transportation, and repository disposal of DOE SNF were not finalized, the NSNFP recognized the necessity to specify a complete DOE SNF canister design. This allowed other evaluations of canister performance and design to proceed as well as providing standardized canister users adequate information to proceed with their work. This paper is an update of a paper presented to the 1999 American Nuclear Society of Mechanical Engineers (ASME) Pressure Vessels and Piping (PVP) Conference. It discusses recent progress achieved in various areas to enhance acceptance of this canister not only by the DOE complex but also fabricators and regulatory agencies.
Date: May 7, 2002
Creator: Morton, D.K.; Snow, S.D.; Rahl, T.E.; Hill, T.J. (INEEL) & Morissette, R.P. (Beckman and Associates, Inc.)
Partner: UNT Libraries Government Documents Department

Oxidative Mineralization and Characterization of Polyvinyl Alcohol Solutions for Wastewater Treatment

Description: Photochemical and ultrasonic treatment of polyvinyl alcohol (PVA), derived from PVA fabric material, with hydrogen peroxide was evaluated as a primary method for PVA mineralization into simpler organic molecules. PVA-based waste streams have been found to be compatible with nuclear process wastewater treatment facilities only when solubilized PVA is more than 90 percent mineralized with hydrogen peroxide. No undesirable solid particles are formed with other nuclear process liquid waste when they are mixed, pH adjusted, evaporated and blended with this type of oxidized PVA waste streams. The presence of oxidized PVA in a typical nuclear process wastewater has been found to have no detrimental effect on the efficiency of ion exchange resins, inorganic, and precipitation agents used for the removal of radionuclides from nuclear waste streams. The disappearance of PVA solution in hydrogen peroxide with ultrasonic/ ultraviolet irradiation treatment was characterized by pseudo-first-order reaction kinetics. Radioactive waste contaminated PVA fabric can be solubilized and mineralized to produce processible liquid waste, hence, no bulky solid waste disposal cost can be incurred and the radionuclides can be effectively recovered. Therefore, PVA fabric materials can be considered as an effective substitute for cellulose fabrics that are currently used in radioactive waste decontamination processes.
Date: August 7, 2003
Creator: Oji, L.N.
Partner: UNT Libraries Government Documents Department

Field quality measurements of Fermilab Nb{sub 3}Sn common coil dipole model

Description: A short model of single-layer Nb{sub 3}Sn common coil magnet has been fabricated and is being tested at Fermilab. This paper summarizes results of magnetic measurements in this model. The geometrical harmonics, coil magnetization and iron saturation effects, ramp-rate dependence, field decay and the ''snap-back'' effect at injection are presented.
Date: November 7, 2003
Creator: al., Vadim Kashikhin et
Partner: UNT Libraries Government Documents Department

Determining size-specific emission factors for environmental tobacco smoke particles

Description: Because size is a major controlling factor for indoor airborne particle behavior, human particle exposure assessments will benefit from improved knowledge of size-specific particle emissions. We report a method of inferring size-specific mass emission factors for indoor sources that makes use of an indoor aerosol dynamics model, measured particle concentration time series data, and an optimization routine. This approach provides--in addition to estimates of the emissions size distribution and integrated emission factors--estimates of deposition rate, an enhanced understanding of particle dynamics, and information about model performance. We applied the method to size-specific environmental tobacco smoke (ETS) particle concentrations measured every minute with an 8-channel optical particle counter (PMS-LASAIR; 0.1-2+ micrometer diameters) and every 10 or 30 min with a 34-channel differential mobility particle sizer (TSI-DMPS; 0.01-1+ micrometer diameters) after a single cigarette or cigar was machine-smoked inside a low air-exchange-rate 20 m{sup 3} chamber. The aerosol dynamics model provided good fits to observed concentrations when using optimized values of mass emission rate and deposition rate for each particle size range as input. Small discrepancies observed in the first 1-2 hours after smoking are likely due to the effect of particle evaporation, a process neglected by the model. Size-specific ETS particle emission factors were fit with log-normal distributions, yielding an average mass median diameter of 0.2 micrometers and an average geometric standard deviation of 2.3 with no systematic differences between cigars and cigarettes. The equivalent total particle emission rate, obtained integrating each size distribution, was 0.2-0.7 mg/min for cigars and 0.7-0.9 mg/min for cigarettes.
Date: July 7, 2002
Creator: Klepeis, Neil E.; Apte, Michael G.; Gundel, Lara A.; Sextro, Richard G. & Nazaroff, William W.
Partner: UNT Libraries Government Documents Department

Frequency chirp and pulse shape effects in self-modulated laser wakefield accelerators

Description: The effect of asymmetric laser pulses on plasma wave excitation in a self-modulated laser wakefield accelerator is examined. Laser pulse shape and frequency chirp asymmetries, controlled experimentally in the laser system through a grating pair compressor, are shown to strongly enhance measured electron yields for certain asymmetries. It is shown analytically that a positive (negative) frequency chirp enhances (suppresses) the growth rate of the Raman forward scattering and near-forward Raman sidescatter instabilities, but is of minimal importance for the experimental parameters. Temporal laser pulse shapes with fast rise times (< plasma period) are shown to generate larger wakes (compared to slow rise time pulses) which seed the growth of the plasma wave, resulting in enhanced electron yield.
Date: November 7, 2002
Creator: Schroeder, C.B.; Esarey, E.; Geddes, C.G.R.; Toth, Cs.; Shadwick, B.A.; van Tilborg, J. et al.
Partner: UNT Libraries Government Documents Department

Observation of high energy atmospheric neutrinos with antarctic muon and neutrino detector array

Description: The Antarctic Muon and Neutrino Detector Array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 10{sup 6} times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05 x 10{sup 9} cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90 percent of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.
Date: May 7, 2002
Creator: Ahrens, J.; Andres, E.; Bai, X.; Barouch, G.; Barwick, S.W.; Bay, R.C. et al.
Partner: UNT Libraries Government Documents Department

Gallium Safety in the Laboratory

Description: A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.
Date: May 7, 2003
Creator: Cadwallader, L.C.
Partner: UNT Libraries Government Documents Department

Time Evolution of Beam in the Recycler Ring

Description: We study the time evolution of the beam current in the Fermilab Recycler Ring due to abrupt physical processes (single coulomb scattering, nuclear scattering) that cause sudden loss of beam, and diffusive processes (multiple coulomb scattering, lattice dependence, etc.) which cause emittance growth. This emittance growth combined with finite aperture of the beam pipe will lead to eventual loss of most beam. We develop a fitting technique to the time evolution of beam current to estimate emittance growth. Finally we compare the directly measured growth with the fitted value.
Date: May 7, 2003
Creator: Krish Gounder, John Marriner and Shekhar Mishra
Partner: UNT Libraries Government Documents Department

Proposal for Qualification of Gas-Generating Radioactive Payloads for Transportation within a Type B Package

Description: Characterization data describing radioactive materials (RAM) in storage are likely those associated with the processes that produced the materials or with the mission for which they were produced. Along with impurity data, often absent or unknown as a result of post-processing storage environment is moisture content. Radiolysis of moisture may lead to a hydrogen flammability hazard within a closed volume such as a storage can or a transportation package. This paper offers a practical means of qualifying payloads of unknown moisture content for shipment within Type B packaging, while supporting the DOE program to maintain radworker dose as low as reasonable achievable (ALARA). Specifically, the paper discusses part of a qualification program carried out at the Savannah River Site for onsite shipment of legacy RAM within the DDF-1 package. The DDF-1 is an onsite-only prototype of the currently certified 9975 package. Measurement of storage-can lid bulge can provide an upper bound for pressure within a storage can. Subsequent belljar testing can measure the rate of gas leakage from a storage can. These actions are shown sufficient to ensure that the performance of the 9975 containment vessels can accommodate the deflagration energy from flammable gas mixtures within Normal Conditions of Transport, and, and the consequences of a detonation shock wave within Hypothetical Accident Conditions.
Date: June 7, 2002
Creator: Houghtaling, T.K.
Partner: UNT Libraries Government Documents Department

Extrapolation of supersymmetry-breaking parameters to high energy scales

Description: The author studies how well one can extrapolate the values of supersymmetry-breaking parameters to very high energy scales using future data from the Large Hadron Collider and an e{sup +}e{sup -} linear collider. He considers tests of the unification of squark and slepton masses in supergravity-inspired models. In gauge-mediated supersymmetry breaking models, he assess the ability to measure the mass scales associated with supersymmetry breaking. He also shows that it is possible to get good constraints on a scalar cubic stop-stop-Higgs couplings near the high scale. Different assumptions with varying levels of optimism about the accuracy of input parameter measurements are made, and their impact on the extrapolated results is documented.
Date: November 7, 2002
Creator: Martin, Stephen P
Partner: UNT Libraries Government Documents Department