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Materials Science at the Extremes of Pressure and Strain Rate (open access)

Materials Science at the Extremes of Pressure and Strain Rate

Solid state experiments at very high pressures and strain rates are possible on high power laser facilities, albeit over brief intervals of time and spatial small scales. A new shockless drive has been developed on the Omega laser. VISAR measurements establish the high strain rates, 10{sup 7}-10{sup 8} s{sup -1}. Solid-state strength is inferred using the Rayleigh-Taylor instability as a ''diagnostic''. Temperature and compression in polycrystalline samples can be deduced from EXAFS measurements. Lattice response can be inferred from time-resolved x-ray diffraction. Deformation mechanisms can be identified by examining recovered samples. We will briefly review this new area of laser-based materials science research, then present a path forward for carrying these solid-state experiments to much higher pressures, P >> 1 Mbar, on the NIF laser facility.
Date: August 20, 2003
Creator: Remington, B. A.; Cavallo, R. M.; Edwards, M. J.; Lasinski, B. F.; Lorenz, K. T.; Lorenzana, H. E. et al.
System: The UNT Digital Library
A Neutron Source Facility for Neutron Cross-Section Measurements on Radioactive Targets at RIA (open access)

A Neutron Source Facility for Neutron Cross-Section Measurements on Radioactive Targets at RIA

The stockpile stewardship program is interested in neutron cross-section measurements on nuclei that are a few nucleons away from stability. Since neutron targets do not exist, radioactive targets are the only way to directly perform these measurements. This requires a facility that can provide high production rates for these short-lived nuclei as well as a source of neutrons. The Rare Isotope Accelerator (RIA) promises theses high production rates. Thus, adding a co-located neutron source facility to the RIA project baseline would allow these neutron cross-section measurements to be made. A conceptual design for such a neutron source has been developed, which would use two accelerators, a Dynamitron and a linac, to create the neutrons through a variety of reactions (d-d, d-t, deuteron break-up, p-Li). This range of reactions is needed in order to provide the desired energy range from 10's of keV to 20 MeV. The facility would also have hot cells to perform chemistry on the radioactive material both before and after neutron irradiation. The present status of this design and direction of future work will be discussed.
Date: May 20, 2003
Creator: Ahle, L. E.; Bernstein, L.; Rusnak, B. & Berio, R.
System: The UNT Digital Library
PLEIADES: A Picosecond Compton Scattering X-Ray Source for Advanced Backlighting and Time-Resolved Material Studies (open access)

PLEIADES: A Picosecond Compton Scattering X-Ray Source for Advanced Backlighting and Time-Resolved Material Studies

The PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 {micro}m rms, at 57 MeV, with 260 C of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820-nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x-rays were captured with a cooled charge-coupled device using a Cesium Iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3 x 10{sup 6} photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently underway, with the goal of reaching 10{sup 8} photons per shot and a peak brightness approaching 10{sup 20} photons/mm{sup 2}/mrad{sup 2}/s/0.1%bandwidth.
Date: October 20, 2003
Creator: Gibson, D J; Anderson, S G; Barty, C P; Betts, S M; Booth, R; Brown, W J et al.
System: The UNT Digital Library
Multi-scale Science: Supporting Emerging Practice with Semantically Derived Provenance (open access)

Multi-scale Science: Supporting Emerging Practice with Semantically Derived Provenance

Scientific progress is becoming increasingly dependent of our ability to study phenomena at multiple scales and from multiple perspectives. The ability to recontextualize third party data within the semantic and syntactic framework of a given research project is increasingly seen as a primary barrier in multi-scale science. Within the Collaboratory for Multiscale Chemical Science (CMCS) project, we are developing a general-purpose informatics-based approach that emphasizes ''on-demand'' metadata creation, configurable data translations, and semantic mapping to support the rapidly increasing and continually evolving requirements for managing data, metadata, and data relationships in such projects. A concrete example of this approach is the design of the CMCS provenance subsystem. The concept of provenance varies across communities, and multiple independent applications contribute to and use provenance. In CMCS, we have developed generic tools for viewing provenance relationships and for using them to, for example, scope notifications and searches. These tools rely on a configurable concept of provenance defined in terms of other relationships. The result is a very flexible mechanism capable of tracking data provenance across many disciplines and supporting multiple uses of provenance information.
Date: October 20, 2003
Creator: Myers, James D.; Pancerella, Carmen M.; Lansing, Carina S.; Schuchardt, Karen L.; Didier, Brett T. & Ashish, N., Goble, C
System: The UNT Digital Library
Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds (open access)

Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds

Spatially Resolved X-Ray Diffraction (SRXRD) has been used to identify a previously unobserved low temperature ferrite ({delta})/austenite({gamma}) phase transformation in the heat affected zone (HAZ) of 2205 Duplex Stainless Steel (DSS) welds. In this ''ferrite dip'' transformation, the ferrite transforms to austenite during heating to peak temperatures on the order of 750 C, and re-transforms to ferrite during cooling, resulting in a ferrite volume fraction equivalent to that in the base metal. Time Resolved X-Ray Diffraction (TRXRD) and laser dilatometry measurements during Gleeble{reg_sign} thermal simulations are performed in order to verify the existence of this low temperature phase transformation. Thermodynamic and kinetic models for phase transformations, including both local-equilibrium and para-equilibrium diffusion controlled growth, show that diffusion of substitutional alloying elements does not provide a reasonable explanation for the experimental observations. On the other hand, the diffusion of interstitial alloying elements may be rapid enough to explain this behavior. Based on both the experimental and modeling results, two mechanisms for the ''ferrite dip'' transformation, including the formation and decomposition of secondary austenite and an athermal martensitic-type transformation of ferrite to austenite, are considered.
Date: August 20, 2003
Creator: Palmer, T A; Elmer, J W; Babu, S S & Vitek, J M
System: The UNT Digital Library
Hard processes in hadron-nucleus and nucleus-nucleusinteractions (open access)

Hard processes in hadron-nucleus and nucleus-nucleusinteractions

None
Date: February 20, 2003
Creator: Satz (Ed.), H. & Wang (Ed.), X.-N.
System: The UNT Digital Library
Supergravity Analysis of Hybrid Inflation Model from D3--D7 System (open access)

Supergravity Analysis of Hybrid Inflation Model from D3--D7 System

The slow-roll inflation is a beautiful paradigm, yet the inflaton potential can hardly be sufficiently flat when unknown gravitational effects are taken into account. However, the hybrid inflation models constructed in D = 4 N = 1 supergravity can be consistent with N = 2 supersymmetry, and can be naturally embedded into string theory. This article discusses the gravitational effects carefully in the string model, using D = 4 supergravity description. We adopt the D3--D7 system of Type IIB string theory compactified on K3 x T^2/Z_2 orientifold for definiteness. It turns out that the slow-roll parameter can be sufficiently small despite the non-minimal Kahler potential of the model. The conditions for this to happen are clarified in terms of string vacua. We also find that the geometry obtained by blowing up singularity, which is necessary for the positive vacuum energy, is stabilized by introducing certain 3-form fluxes.
Date: November 20, 2003
Creator: Koyama, Fumikazu; Tachikawa, Yuji & Watari, Taizan
System: The UNT Digital Library
Tissue architecture: the ultimate regulator of breast epithelial function (open access)

Tissue architecture: the ultimate regulator of breast epithelial function

A problem in developmental biology that continues to take center stage is how higher organisms generate diverse tissues and organs given the same cellular genotype. In cell and tumor biology, the key question is not the production of form, but its preservation: how do tissues and organs maintain homeostasis, and how do cells within tissues lose or overcome these controls in cancer? Undoubtedly, mechanisms that maintain tissue specificity should share features with those employed to drive formation of the tissues. However, they are unlikely to be identical. At a simplistic level, developmental pathways may be thought of as a series of extremely rapid short-term events. Each new step depends on what came before, and the outcome is the organism itself at birth. All organs, with a few notable exceptions, such as the mammary gland and the brain, 'arrive' together and are complete when the organism is born. In mice and humans, these events occur in a mere 21 days and 9 months respectively. The stability of the differentiated state and the homeostasis of the organism, on the other hand, will last 40-110 times longer. How does the organism achieve this feat? How are tissues maintained? These questions also relate fundamentally …
Date: October 20, 2003
Creator: Bissell, Mina J; Rizki, Aylin & Mian, Saira
System: The UNT Digital Library
Pulse shape and spectrum of coherent diffraction-limited transition radiation from electron beams (open access)

Pulse shape and spectrum of coherent diffraction-limited transition radiation from electron beams

The electric field in the temporal and spectral domain of coherent diffraction-limited transition radiation is studied. An electron bunch, with arbitrary longitudinal momentum distribution, propagating at normal incidence to a sharp metal-vacuum boundary with finite transverse dimension is considered. A general expression for the spatiotemporal electric field of the transition radiation is derived, and closed-form solutions for several special cases are given. The influence of parameters such as radial boundary size, electron momentum distribution, and angle of observation on the waveform (e.g., radiation pulse length and amplitude) are discussed. For a Gaussian electron bunch, the coherent radiation waveform is shown to have a single-cycle profile. Application to a novel THz source based on a laser-driven accelerator is discussed.
Date: December 20, 2003
Creator: van Tilborg, J.; Schroeder, C. B.; Esarey, E. & Leemans, W. P.
System: The UNT Digital Library
The DOE Water Cycle Pilot Study (open access)

The DOE Water Cycle Pilot Study

A Department of Energy (DOE) multi-laboratory Water Cycle Pilot Study (WCPS) investigated components of the local water budget at the Walnut River Watershed in Kansas to study the relative importance of various processes and to determine the feasibility of observational water budget closure. An extensive database of local meteorological time series and land surface characteristics was compiled. Numerical simulations of water budget components were generated and, to the extent possible, validated for three nested domains within the Southern Great Plains; the DOE Atmospheric Radiation Measurement/Cloud Atmospheric Radiation Testbed (ARM/CART), the Walnut River Watershed (WRW), and the Whitewater Watershed (WW), Kansas A 2-month Intensive Observation Period (IOP) was conducted to gather detailed observations relevant to specific details of the water budget, including fine-scale precipitation, streamflow, and soil moisture measurements not made routinely by other programs. Event and season al water isotope (delta 18O, delta D) sampling in rainwater, streams, soils, lakes, and wells provided a means of tracing sources and sinks within and external to the WW, WRW, and the ARM/CART domains. The WCPS measured changes in leaf area index for several vegetation types, deep groundwater variations at two wells, and meteorological variables at a number of sites in the WRW. …
Date: September 20, 2003
Creator: Miller, N. L.; King, A. W.; Miller, M. A.; Springer, E. P.; Wesely, M. L.; Bashford, K. E. et al.
System: The UNT Digital Library
Rapidity and centrality dependence of proton and anti-proton production from 197Au+197Au collisions at {radical}(s{sub NN}) = 130 GeV (open access)

Rapidity and centrality dependence of proton and anti-proton production from 197Au+197Au collisions at {radical}(s{sub NN}) = 130 GeV

We report on the rapidity and centrality dependence of proton and anti-proton transverse mass distributions from {sup 197}Au + {sup 197}Au collisions at {radical}s{sub NN} = 130 GeV as measured by the STAR experiment at RHIC. Our results are from the rapidity and transverse momentum range of |y| < 0.5 and 0.35 < p{sub t} < 1.00 GeV/c. For both protons and anti-protons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within |y| < 0.5. Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton(anti-proton) yields and transverse mass distributions the possibility of pre-hadronic collective expansion may have to be taken into account.
Date: June 20, 2003
Creator: Adams, J.; Adler, C.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System: The UNT Digital Library
Electrochemical studies of the LiFePO<sub 4> thin films prepared with pulsed laser deposition (open access)

Electrochemical studies of the LiFePO<sub 4> thin films prepared with pulsed laser deposition

Thin films of LiFePO4 have been prepared on stainless steel substrates with pulsed laser deposition utilizing an Ar atmosphere. Films were characterized with XRD, SEM, Raman spectroscopy and electrochemistry in liquid electrolyte. Raman spectral analysis revealed the presence of carbon in the films, even though the targets contained less than a few percent residual carbon. The Raman spectra also suggest the presence of various iron oxide species on the surface of the film. The 75nm film showed reversible cycling of more than 90 mAh/g for 60 cycles and a coulombic efficiency close to 1. Variable sweep rate cyclic voltammetry showed a diffusion-controlled reaction with an effective diffusivity of about 10-12 cm2/s. The performance of the thicker film was poor with a coulombic efficiency much less than 1.
Date: May 20, 2003
Creator: Song, Seung-Wan; Reade, Ronald P. & Striebel, Kathryn A.
System: The UNT Digital Library
The approach curve method for large anode-cathode distances (open access)

The approach curve method for large anode-cathode distances

An important technique used to characterize field emission is the measurement of the emitted current against electric field (IxE). In this work we discuss a procedure for obtaining IxE data based on multiple approach curves. We show that the simulated features obtained for an idealized uniform surface matches available experimental data for small anode-cathode distances, while for large distances the simulation predicts a departure from the linear regime. We also discuss the shape of the approach curves for large anode-cathode distances for a cathode made of carbon nanotubes.
Date: September 20, 2003
Creator: Mammana, Victor P.; Monteiro, Othon R. & Fonseca, Leo R.C.
System: The UNT Digital Library
Using XDAQ in application scenarios of the CMS experiment (open access)

Using XDAQ in application scenarios of the CMS experiment

XDAQ is a generic data acquisition software environment that emerged from a rich set of use-cases encountered in the CMS experiment. They cover not the deployment for multiple sub-detectors and the operation of different processing and networking equipment as well as a distributed collaboration of users with different needs. The use of the software in various application scenarios demonstrated the viability of the approach. We discuss two applications, the tracker local DAQ system for front-end commissioning and the muon chamber validation system. The description is completed by a brief overview of XDAQ.
Date: October 20, 2003
Creator: al., V. Brigljevic et
System: The UNT Digital Library
Microphonics detuning compensation in 3.9 GHZ superconducting RF cavities (open access)

Microphonics detuning compensation in 3.9 GHZ superconducting RF cavities

Mechanical vibrations can detune superconducting radio frequency (SCRF) cavities unless a tuning mechanism counteracting the vibrations is present. Due to their narrow operating bandwidth and demanding mechanical structure, the 13-cell 3.9GHz SCRF cavities for the Charged Kaons at Main Injector (CKM) experiment at Fermilab are especially susceptible to this microphonic phenomena. We present early results correlating RF frequency detuning with cavity vibration measurements for CKM cavities; initial detuning compensation results with piezoelectric actuators are also presented.
Date: October 20, 2003
Creator: al., Ruben Carcagno et
System: The UNT Digital Library
System level radiation validation studies for the CMS HCAL front-end electronics (open access)

System level radiation validation studies for the CMS HCAL front-end electronics

Over a 10 year operating period, the CMS Hadron Calorimeter (HCAL) detector will be exposed to radiation fields of approximately 1 kRad of total ionizing dose (TID) and a neutron fluence of 4E11 n/cm{sup 2}. All front-end electronics must be qualified to survive this radiation environment with no degradation in performance. In addition, digital components in this environment can experience single-event upset (SEU) and single-event latchup (SEL). A measurement of these single-event effects (SEE) for all components is necessary in order to understand the level that will be encountered. System level studies of the performance of the front-end boards in a 200 MeV proton beam are presented. Limits on the latch-up immunity along with the expected SEU rate for the full front-end system have been measured. The first results from studies of the performance of the two Fermilab custom-designed chips in a radiation environment also are shown.
Date: October 20, 2003
Creator: Whitmore, J.
System: The UNT Digital Library
Searching for X(5) behavior in nuclei (open access)

Searching for X(5) behavior in nuclei

None
Date: May 20, 2003
Creator: Clark, Rod M.; Cromaz, Mario A.; Deleplanque, Marie-Agnes; Descovich, Martina; Diamond, Richard M.; Fallon, Paul et al.
System: The UNT Digital Library
Adaptive low mach number simulations of a premixed turbulent laboratory burner (open access)

Adaptive low mach number simulations of a premixed turbulent laboratory burner

A parallel adaptive low Mach number model is used to study an experimental lean premixed turbulent methane V-flame that is stabilized on a rod spanning the exit plane of a circular nozzle. The fuel is turbulent due to an upstream perforated-plate, and the resulting flame extends downstream of the rod. We present three-dimensional time-dependent simulations of this configuration. The computations incorporate detailed reaction chemistry and transport using a dynamically adaptive block-structured grid algorithm and a time-split integration procedure. Flow field and flame surface statistics are gathered from the experiment and are compared to the computed results.
Date: October 20, 2003
Creator: Day, M.S.; Bell, J.B.; Lijewski, M.J.; Johnson, M.; Cheng, R.K. & Shepherd, I.G.
System: The UNT Digital Library
4th International Plant Biomechanics Conference Proceedings (Abstracts) (open access)

4th International Plant Biomechanics Conference Proceedings (Abstracts)

The 4th International Plant Biomechanics Conference facilitated an interdisciplinary exchange between scientists, engineers, and educators addressing the major questions encountered in the field of Plant Biomechanics. Subjects covered by the conference include: Evolution; Ecology; Mechanoreception; Cell Walls; Genetic Modification; Applied Biomechanics of Whole Plants, Plant Products, Fibers & Composites; Fluid Dynamics; Wood & Trees; Fracture Mechanics; Xylem Pressure & Water Transport; Modeling; and Introducing Plant Biomechanics in Secondary School Education.
Date: July 20, 2003
Creator: Telewski, Frank W.; Koehler, Lothar H. & Ewers, Frank W.
System: The UNT Digital Library
Implementations of mesh refinement schemes for particle-in-cell plasma simulations (open access)

Implementations of mesh refinement schemes for particle-in-cell plasma simulations

Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation region, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations and present two implementations in more detail, with examples.
Date: October 20, 2003
Creator: Vay, J. L.; Colella, P.; Friedman, A.; Grote, D. P.; McCorquodale, P. & Serafini, D. B.
System: The UNT Digital Library
Tune-Shift Compensation Using the Tevatron Electron Lens (open access)

Tune-Shift Compensation Using the Tevatron Electron Lens

The Tevatron Electron Lens was originally designed to alleviate the tune shift and spread induced in Tevatron antiproton bunches from interactions with the proton bunches. We report recent developments and successful results of such tune-shift compensation. Lifetime measurements are central to our data and the basis of our analysis. Future goals and possible uses for the lens are also discussed.
Date: August 20, 2003
Creator: al., Kip Bishofberger et
System: The UNT Digital Library
Simulation aspects of beam collimation and their remedies in the MARS14 code (open access)

Simulation aspects of beam collimation and their remedies in the MARS14 code

Simulation aspects of beam collimation are described along with a number of tools and methods developed and used within the MARS14 framework. The tools and methods were implemented in order to relieve the burden of simulations needed for reliable calculations required for design of efficient collimation systems at high-intensity accelerators and colliders.
Date: August 20, 2003
Creator: al., Mikhail A Kostin et
System: The UNT Digital Library
Fabrication of large diameter alumino-silicate K{sup +} sources (open access)

Fabrication of large diameter alumino-silicate K{sup +} sources

Alumino-silicate K{sup +} sources have been used in HIF experiments for many years. For example the Neutralized Transport Expt. (NTX) and the High Current Transport Expt. (HCX) are now using this type of ion source with diameters of 2.54 cm and 10 cm respectively. These sources have demonstrated ion currents of 80 mA and 700 mA, for typical HIF pulse lengths of 5-10 {micro}s. The corresponding current density is {approx} 10-15 mA/cm{sup 2}, but much higher current density has been observed using smaller size sources. Recently we have improved our fabrication techniques and, therefore, are able to reliably produce large diameter ion sources with high quality emitter surface without defects. This note provides a detailed description of the procedures employed in the fabrication process. The variables in the processing steps affecting surface quality, such as substrate porosity, powder size distribution, coating technique on large area concave surfaces, drying, and heat firing temperature have been investigated.
Date: February 20, 2003
Creator: Baca, D.; Chacon-Golcher, E.; Kwan, J. W. & Wu, J. K.
System: The UNT Digital Library
Comprehensive Environmental Management System Approach: The Right Tool for Stewardship (open access)

Comprehensive Environmental Management System Approach: The Right Tool for Stewardship

Expertise, methodologies and equipment from separate programs at the large Department of Energy sites can be combined to produce a powerful risk-based planning tool for stewardship. Modeling expertise has been developed while conducting required Performance Assessments and Composite Analyses. Data management and display capabilities of modern Geographical Information Systems can make the modeling results useful tools for planning and stewardship.
Date: January 20, 2003
Creator: Cook, J. R.
System: The UNT Digital Library