Beauty, charm and hyperon production at fixed-target experiments (open access)

Beauty, charm and hyperon production at fixed-target experiments

Over the years fixed-target experiments have performed numerous studies of particle production in strong interactions. The experiments have been performed with different types of beam particles of varying energies, and many different target materials. Since the physics of particle production is still not understood, ongoing research of phenomena that we observe as beauty, charm and strange-particle production is crucial if we are to gain an understanding of these fundamental processes. It is in this context that recent results from fixed-target experiments on beauty, charm, and hyperon production will be reviewed.
Date: December 11, 2002
Creator: Gottschalk, Erik
Object Type: Article
System: The UNT Digital Library
Determination of Primordial Metallicity and Mixing in the Type IIP Supernova 1993W (open access)

Determination of Primordial Metallicity and Mixing in the Type IIP Supernova 1993W

We present the results of a large grid of synthetic spectra and compare them to early spectroscopic observations of SN 1993W. This supernova was discovered close to its explosion date and at a recession velocity of 5400 km/s is located in the Hubble flow. We focus here on two early spectra that were obtained approximately 5 and 9 days after explosion. We parameterize the outer supernova envelope as a power-law density profile in homologous expansion. In order to extract information on the value of the parameters a large number of models was required. We show that very early spectra combined with detailed models can provide constraints on the value of the power law index, the ratio of hydrogen to helium in the surface of the progenitor, the progenitor metallicity and the amount of radioactive nickel mixed into the outer envelope of the supernova. The spectral fits reproduce the observed spectra exceedingly well. The spectral results combined with the early photometry predict that the explosion date was 4.7 {+-} 0.7 days before the first spectrum was obtained. The ability to obtain the metallicity from early spectra make SN IIP attractive probes of chemical evolution in the universe and by showing that …
Date: December 11, 2002
Creator: Baron, E.; Nugent, Peter E.; Branch, David; Hauschildt, Peter H.; Turatto, M. & Cappellaro, E.
Object Type: Article
System: The UNT Digital Library
Electron cloud instabilities in the Proton Storage Ring andSpallation Neutron Source (open access)

Electron cloud instabilities in the Proton Storage Ring andSpallation Neutron Source

Electron cloud instabilities in the Los Alamos ProtonStorage Ring (PSR) and those foreseen forthe Oak Ridge SpallationNeutron Source (SNS) are examined theoretically, numerically, andexperimentally.
Date: December 11, 2002
Creator: Blaskiewicz, M.; Furman, M. A.; Pivi, M. & Macek, R. J.
Object Type: Article
System: The UNT Digital Library
Evaluation of uncertainties due to hydrogeological modeling and groundwater flow analysis: Steady flow, transient flow, and thermal studies (open access)

Evaluation of uncertainties due to hydrogeological modeling and groundwater flow analysis: Steady flow, transient flow, and thermal studies

Starting with regional geographic, geologic, surface and subsurface hydrologic, and geophysical data for the Tono area in Gifu, Japan, we develop an effective continuum model to simulate subsurface flow and transport in a 4 km by 6 km by 3 km thick fractured granite rock mass overlain by sedimentary layers. Individual fractures are not modeled explicitly. Rather, continuum permeability and porosity distributions are assigned stochastically, based on well-test data and fracture density measurements. Lithologic layering and one major fault, the Tsukiyoshi Fault, are assigned deterministically. We conduct three different studies: (1) the so-called base case, in which the model simulates the steady-state groundwater flow through the site, and then stream trace analysis is used to calculate travel times to the model boundary from specified release points; (2) simulations of transient flow during long term pump tests (LTPT) using the base-case model; and (3) thermal studies in which coupled heat flow and fluid flow are modeled, to examine the effects of the geothermal gradient on groundwater flow. The base-case study indicates that the choice of open or closed lateral boundaries has a strong influence on the regional groundwater flow patterns produced by the models, but no field data exist that can …
Date: December 11, 2002
Creator: Doughty, Christine & Karasaki, Kenzi
Object Type: Report
System: The UNT Digital Library
Fabrication and test of a racetrack magnet using pre-reacted Nb3Sn cable (open access)

Fabrication and test of a racetrack magnet using pre-reacted Nb3Sn cable

A racetrack magnet, using Nb{sub 3}Sn superconducting cable reacted before winding, has been fabricated and tested at Fermilab. It consists of two flat racetrack coils, connected in a common-coil configuration, separated by a 5 mm thick fiberglass plate. Synthetic oil was used to prevent sintering of the strands during the heat treatment. The coils were wound and vacuum impregnated in the mechanical structure. The turn-to-turn insulation, consisting of Kapton{reg_sign}and pre-impregnated fiberglass tapes as wide as the cable, was wound together with the bare cable in order to form a continuous inter-turn spacer. The coils were instrumented with voltage taps, temperature sensors, spot heaters and quench heaters. The maximum current achieved was 12675 A which is 78% of the short sample limit at 5.1 K (minimum temperature in the coil during 75 A/s ramp). Measurement of the temperature margin revealed a low degradation in the innermost turns. Quench performances at different temperatures and ramp rate effects have been measured and are presented and discussed.
Date: December 11, 2002
Creator: al., Giorgio Ambrosio et
Object Type: Article
System: The UNT Digital Library
Lithographic Characterization of the Printability of Programmed EUV Substrate Defects (open access)

Lithographic Characterization of the Printability of Programmed EUV Substrate Defects

None
Date: December 11, 2002
Creator: Naulleau, Patrick; Goldberg, Kenneth A.; Anderson, Erik H.; Bokor, Jeffrey; Gullikson, Eric; Harteneck, Bruce et al.
Object Type: Article
System: The UNT Digital Library
Thermo-mechanical characterization of insulated and epoxy-impregnated Nb3Sn composites (open access)

Thermo-mechanical characterization of insulated and epoxy-impregnated Nb3Sn composites

Nb{sub 3}Sn is, at present, the best superconductor for high field accelerator magnets. Several models using Nb{sub 3}Sn are under development in many laboratories. Knowledge of the thermo-mechanical properties of the impregnated coils is of crucial importance for the design of these magnets. In fact, the performance of epoxy-impregnated coils is sensitive to the thermal conductivity value, especially in case of heating caused by hysteretic losses, which are usually relevant in Nb{sub 3}Sn magnets, and in the case of continuous heat deposition, such as in magnets near the interaction region of a collider. Thermal contraction measurements are necessary to estimate the stresses during the magnet thermal cycle. Different insulation materials have been studied at Fermilab utilizing various design approaches and fabrication methods. Thermal conductivity and thermal contraction measurements, at cryogenic temperatures, have been performed respectively at INFN-LASA and Fermilab. The results are reported and discussed in this paper.
Date: December 11, 2002
Creator: al., Linda Imbasciati et
Object Type: Article
System: The UNT Digital Library
Autonomous Pathogen Detection System FY02 Annual Progress Report (open access)

Autonomous Pathogen Detection System FY02 Annual Progress Report

The objective of this project is to design, fabricate and field demonstrate a biological agent detection and identification capability, the Autonomous Pathogen Detector System (APDS). Integrating a flow cytometer and real-time polymerase chain reaction (PCR) detector with sample collection, sample preparation and fluidics will provide a compact, autonomously operating instrument capable of simultaneously detecting multiple pathogens and/or toxins. The APDS will operate in fixed locations, continuously monitoring air samples and automatically reporting the presence of specific biological agents. The APDS will utilize both multiplex immunoassays and nucleic acid assays to provide ''quasi-orthogonal'' multiple agent detection approaches to minimize false positives and increase the reliability of identification. Technical advances across several fronts must occur, however, to realize the full extent of the APDS. The end goal of a commercially available system for civilian biological weapon defense will be accomplished through three progressive generations of APDS instruments. The APDS is targeted for civilian applications in which the public is at high risk of exposure to covert releases of bioagent, such as major subway systems and other transportation terminals, large office complexes and convention centers. APDS is also designed to be part of a monitoring network of sensors integrated with command and control …
Date: November 11, 2002
Creator: Colston, B.; Brown, S.; Burris, K.; Elkin, C.; Hindson, B.; Langlois, R. et al.
Object Type: Report
System: The UNT Digital Library
Bulk Materials Analysis Using High-Energy Positron Beams (open access)

Bulk Materials Analysis Using High-Energy Positron Beams

This article reviews some recent materials analysis results using high-energy positron beams at Lawrence Livermore National Laboratory. We are combining positron lifetime and orbital electron momentum spectroscopic methods to provide electron number densities and electron momentum distributions around positron annihilation sites. Topics covered include: correlation of positron annihilation characteristics with structural and mechanical properties of bulk metallic glasses, compositional studies of embrittling features in nuclear reactor pressure vessel steel, pore characterization in Zeolites, and positron annihilation characteristics in alkali halides.
Date: November 11, 2002
Creator: Glade, S C; Asoka-Kumar, P; Nieh, T G; Sterne, P A; Wirth, B D; Dauskardt, R H et al.
Object Type: Article
System: The UNT Digital Library
Current Status and Future Technical Challenges for Tokamak Magnets (open access)

Current Status and Future Technical Challenges for Tokamak Magnets

Magnet technology for fusion in the last decade has been focusing mostly on the development of magnets for tokamaks--the most advanced fusion concept at the moment. The largest and the most complex tokamak under development is ITER. To demonstrate adequate design approaches to large magnets for ITER and to develop industrial capabilities, two large model coils and three insert coils, all using full-scale conductor, were built and tested by the international collaboration during 1994-2002. The status of the magnet technology and directions of future developments are discussed in this paper.
Date: November 11, 2002
Creator: Martovetsky, N.; Minervini, J.; Okuno, K.; Salpiero, E. & Filatov, O.
Object Type: Article
System: The UNT Digital Library
Damping of coupled bunch instabilities by rf frequency modulation (open access)

Damping of coupled bunch instabilities by rf frequency modulation

None
Date: November 11, 2002
Creator: Zotter, Bruno
Object Type: Report
System: The UNT Digital Library
Hydrogen and Its Desorption in Rhic. (open access)

Hydrogen and Its Desorption in Rhic.

Hydrogen is the dominating gas specie in room temperature, ultrahigh vacuum systems of particle accelerators and storage rings, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. Rapid pressure increase of a few decades in hydrogen and other residual gases was observed during RHIC's recent high intensity gold and proton runs. The type and magnitude of the pressure increase were analyzed and compared with vacuum conditioning, beam intensity, number of bunches and bunch spacing. Most of these pressure increases were found to be consistent with those induced by beam loss and/or electron stimulated desorption from electron multipacting.
Date: November 11, 2002
Creator: Hseuh, H. C.
Object Type: Article
System: The UNT Digital Library
Hydrogen Outgassing and Surface Properties of Tin Coated Stainless Steel Chambers. (open access)

Hydrogen Outgassing and Surface Properties of Tin Coated Stainless Steel Chambers.

The stainless steel vacuum chambers of the 248m accumulator ring of Spallation Neutron Source (SNS) are coated with {approx} 100 nm of titanium nitride (TiN) to reduce the secondary electron yield. The coating is produced by DC magnetron sputtering using a long cathode imbedded with permanent magnets. The outgassing rates of several SNS half-cell chambers were measured with and without TiN coating, and before and after in-situ bake. One potential benefit of a TiN coating is to serve as hydrogen permeation barrier that reduces the ultimate outgassing rate. By varying the coating parameters, films of different surface roughness were produced and analyzed by Auger electron spectroscopy, scanning electron microscopy and atomic force microscopy to illustrate the dependence of the outgassing on the film structure.
Date: November 11, 2002
Creator: He, P.; Hseuh, H. C.; Mapes, M.; Todd, R.; Weiss, D. & Wilson, D.
Object Type: Article
System: The UNT Digital Library
Multiscale Thermohydrologic Model Analyses of Heterogeneity and Thermal-Loading Factors for the Proposed Repository at Yucca Mountain (open access)

Multiscale Thermohydrologic Model Analyses of Heterogeneity and Thermal-Loading Factors for the Proposed Repository at Yucca Mountain

The MultiScale ThermoHydrologic Model (MSTHM) predicts thermohydrologic (TH) conditions in emplacement drifts and the adjoining host rock throughout the proposed nuclear-waste repository at Yucca Mountain. The MSTHM is a computationally efficient approach that accounts for TH processes occurring at a scale of a few tens of centimeters around individual waste packages and emplacement drifts, and for heat flow at the multi-kilometer scale at Yucca Mountain. The modeling effort presented here is an early investigation of the repository and is simulated at a lower temperature mode and with a different panel loading than the repository currently being considered for license application. We present these recent lower temperature mode MSTHM simulations that address the influence of repository-scale thermal-conductivity heterogeneity and the influence of preclosure operational factors affecting thermal-loading conditions. We can now accommodate a complex repository layout with emplacement drifts lying in non-parallel planes using a superposition process that combines results from multiple mountain-scale submodels. This development, along with other improvements to the MSTHM, enables more rigorous analyses of preclosure operational factors. These improvements include the ability to (1) predict TH conditions on a drift-by-drift basis, (2) represent sequential emplacement of waste packages along the drifts, and (3) incorporate distance- and time-dependent …
Date: November 11, 2002
Creator: Glascoe, Lee G.; Buscheck, Thomas A.; Gansemer, James; Sun, Yunwei & Lee, Kenrick
Object Type: Article
System: The UNT Digital Library
Safety Issues of HG and PB as IFE Target Materials: Radiological Versus Chemical Toxicity (open access)

Safety Issues of HG and PB as IFE Target Materials: Radiological Versus Chemical Toxicity

We have performed a safety assessment of mercury and lead as possible hohlraum materials for Inertial Fusion Energy (IFE) targets, including for the first time a comparative analysis of the radiological and toxicological consequences of an accidental release. In order to calculate accident doses to the public, we have distinguished between accidents at the target fabrication facility and accidents at other areas of the power plant. Regarding the chemical toxicity assessment, we have used the USDOE regulations to determine the maximum allowable release in order to protect the public from adverse health effects. Opposite to common belief, it has been found that the chemical safety requirements for these materials appear to be more stringent than the concentrations that would result in an acceptable radiological dose.
Date: November 11, 2002
Creator: Reyes, S; Latkowski, J F; Cadwallader, L C; Moir, R W; Rio, G. D & Sanz, J
Object Type: Article
System: The UNT Digital Library
THE ALGEBRA OF TAYLOR SERIES AND THE ROOTS OF A GENERAL POLYNOMIAL. (open access)

THE ALGEBRA OF TAYLOR SERIES AND THE ROOTS OF A GENERAL POLYNOMIAL.

We develop the basic elements of the algebra of Taylor series. This knowledge allows us to derive a series expression for an exact root of a general polynomial of arbitrary degree.
Date: October 11, 2002
Creator: Herrera, J.
Object Type: Report
System: The UNT Digital Library
Analysis of Raster Scanning Damage and Conditioning Experiments (open access)

Analysis of Raster Scanning Damage and Conditioning Experiments

The raster scan technique is used for large optics damage tests and laser conditioning. We show that the ''effective area'' concept enables the possibility to compare various scanning schemes and to use raster scan experiments for NIF optics damage prediction. It is shown that the hexagonal lattice of laser beam imprints yields optimal use of each shot for most of the typically used parameters. The effects of beam fluence fluctuations and pointing inaccuracies on experiments are evaluated. To analyze raster scan conditioning experiments, we introduce the concept of ''effective dose'', i.e. total dose averaged over a unit cell of the scan lattice. This allows various scanning schemes to be compared quantitatively.
Date: October 11, 2002
Creator: Feit, M D & Rubenchik, A M
Object Type: Article
System: The UNT Digital Library
Ductile Necking and Fragmentation of Ductile Materials at High Rates of Extension. Final Report (open access)

Ductile Necking and Fragmentation of Ductile Materials at High Rates of Extension. Final Report

A summary is provided of research concerning ductile necking and fragmentation of ductile materials at high rates of extension, and crack growth and crack pattern formation in strained thin films. Final Report.
Date: October 11, 2002
Creator: Freund, L. B.
Object Type: Report
System: The UNT Digital Library
Extreme Bal quasars from the Sloan Digital Sky Survey (open access)

Extreme Bal quasars from the Sloan Digital Sky Survey

The Sloan Digital Sky Survey has discovered a population of broad absorption line quasars with various extreme properties. Many show absorption from metastable states of Fe II with varying excitations; several objects are almost completely absorbed bluewards of Mg II; at least one shows stronger absorption from Fe III than Fe II, indicating temperatures T > 35000 K in the absorbing region; and one object even seems to have broad H{beta} absorption. Many of these extreme BALs are also heavily reddened, though ''normal'' BALs (particularly LoBALs) from SDSS also show evidence for internal reddening.
Date: October 11, 2002
Creator: al., Patrick B. Hall et
Object Type: Article
System: The UNT Digital Library
Hydroacoustic Evaluation of Fish-Passage Efficiency at Bonneville Dam in 2001 (open access)

Hydroacoustic Evaluation of Fish-Passage Efficiency at Bonneville Dam in 2001

The Portland District of the U.S. Army Corps of Engineers requested that scientists with the Pacific Northwest National Laboratory (PNNL) and the U.S. Army Engineer Research and Development Center (ERDC) conduct the hydroacoustic fish-passage studies described in this report. The ERDC also contracted with MEVATEC Corporation and Dyntel to provide staff ranging from scientists to technicians for the study. This study supports the Portland-District goal of maximizing fish passage efficiency (FPE) and obtaining 95% survival for juvenile salmon passing the Bonneville Project. This report presents results of two hydroacoustic studies of juvenile salmonids. One was a Project-wide study of fish-passage efficiency, and the other was more narrowly focused upon the approach, vertical distribution, and fish-guidance efficiency (FGE) of fish at Unit 15, where the Portland District extensively modified the gatewell and vertical barrier screen to improve gatewell flow and FGE. The goal of the larger of the two studies was to provide project-wide estimates of FPE, spill efficiency, and spill effectiveness for run-of-river fish passing the Bonneville Project during the 2001 out-migration. This type of study also provides estimates of the horizontal, vertical, and diel distributions of fish passage and FGE by turbine unit. These data will provide a baseline …
Date: October 11, 2002
Creator: Ploskey, Gene R.; Schilt, Carl R.; Hanks, Michael E.; Johnson, Peter N.; Kim, Jina; Skalski, John R. et al.
Object Type: Report
System: The UNT Digital Library
Methods for Mitigating Growth of Laser-Initiated Surface Damage on DKDP Optics at 351nm (open access)

Methods for Mitigating Growth of Laser-Initiated Surface Damage on DKDP Optics at 351nm

We report an experimental investigation of mitigating surface damage growth at 351nm for machine-finished DKDP optics. The objective was to determine which methods could be applied to pre-initiated or retrieved-from-service optics, in order to stop further damage growth for large aperture DKDP optics used in high-peak-power laser applications. The test results, and the evaluation thereof, are presented for several mitigation methods applied to DKDP surface damage. The mitigation methods tested were CW-CO{sub 2} laser processing, aqueous wet-etching, short-pulse laser ablation, and micro-machining. We found that micro-machining, using a single crystal diamond tool to completely remove the damage pit, produces the most consistent results to halt the growth of surface damage on DKDP. We obtained the successful mitigation of laser-initiated surface damage sites as large as 0.14mm diameter, for up to 1000 shots at 351nm and fluences in the range of 2 to 13J/cm{sup 2}, {approx} 11ns pulse length. Data obtained to-date indicates that micro-machining is the preferred method to process large-aperture optics.
Date: October 11, 2002
Creator: Hrubesh, L. W.; Brusasco, R. B.; Grundler, W.; Norton, M. A.; Donohue, E. E.; Molander, W. A. et al.
Object Type: Article
System: The UNT Digital Library
NEUTRINOS, PAST AND PRESENT. (open access)

NEUTRINOS, PAST AND PRESENT.

None
Date: October 11, 2002
Creator: GOLDHABER,M.
Object Type: Article
System: The UNT Digital Library
A particle-bed gas cooled fast reactor core design for waste minimization. (open access)

A particle-bed gas cooled fast reactor core design for waste minimization.

The issue of waste minimization in advanced reactor systems has been investigated using the Particle-Bed Gas-Cooled Fast Reactor (PB-GCFR) design being developed and funded under the U.S. Department of Energy Nuclear Energy Research Initiative (USDOE NERI) Program. Results indicate that for the given core power density and constraint on the maximum TRU enrichment allowable, the lowest amount of radiotoxic transuranics to be processed and hence sent to the repository is obtained for long-life core designs. Calculations were additionally done to investigate long-life core designs using LWR spent fuel TRU and recycle TRU, and different feed, matrix and reflector materials. The recycled TRU and LWR spent TRU fuels give similar core behaviors, because of the fast spectrum environment which does not significantly degrade the TRU composition. Using light elements as reflector material was found to be unattractive because of power peaking problems and large reactivity swings. The application of a lead reflector gave the longest cycle length and lowest TRU processing requirement. Materials compatibility and performance issues require additional investigation.
Date: October 11, 2002
Creator: Hoffman, E. A.; Taiwo, T. A.; Yang, W. S. & Fatone, M.
Object Type: Article
System: The UNT Digital Library
Simulations of Boundary Turbulence in Tokamak Experiments (open access)

Simulations of Boundary Turbulence in Tokamak Experiments

Comparisons between the boundary plasma turbulence observed in the BOUT code and experiments on C-Mod, NSTX, and DIII-D are presented. BOUT is a 3D non-local electromagnetic turbulence simulation code which models boundary-plasma turbulence in a realistic divertor geometry using the modified Braginskii equations for plasma vorticity, density, the electron and ion temperatures and parallel momenta. Many features of the Quasi-Coherent (QC) mode, observed at high densities during enhanced D-alpha (EDA) H-Mode in Alcator C-Mod, are reproduced in BOUT simulations. The spatial structure of boundary plasma turbulence as observed by gas puff imaging (GPI) from discharges on NSTX and C-Mod are in general (NSTX) to good (CMod) agreement with BOUT simulations. Finally, BOUT simulations of DIII-D L-mode experiments near the Hmode transition threshold are in broad agreement with the experimental results.
Date: October 11, 2002
Creator: Nevins, W. M.; Xu, X. Q.; Carlstrom, T. N.; Cohen, R. H.; Groebner, R.; Jennings, T. et al.
Object Type: Article
System: The UNT Digital Library