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Magnetron co-sputtering system for coating ICF targets (open access)

Magnetron co-sputtering system for coating ICF targets

Fabrication of Inertial Confinement Fusion (ICF) targets requires deposition of various types of coatings on microspheres. The mechanical strength, and surface finish of the coatings are of concern in ICF experiments. The tensile strength of coatings can be controlled through grain refinement, selective doping and alloy formation. We have constructed a magnetron co-sputtering system to produce variable density profile coatings with high tensile strength on microspheres. The preliminary data on the properties of a Au-Cu binary alloy system by SEM and STEM analysis is presented.
Date: December 9, 1981
Creator: Hsieh, E. J.; Meyer, S. F.; Halsey, W. G.; Jameson, G. T. & Wittmayer, F. J.
System: The UNT Digital Library
An Extensible Open-Source Compiler Infrastructure for Testing (open access)

An Extensible Open-Source Compiler Infrastructure for Testing

Testing forms a critical part of the development process for large-scale software, and there is growing need for automated tools that can read, represent, analyze, and transform the application's source code to help carry out testing tasks. However, the support required to compile applications written in common general purpose languages is generally inaccessible to the testing research community. In this paper, we report on an extensible, open-source compiler infrastructure called ROSE, which is currently in development at Lawrence Livermore National Laboratory. ROSE specifically targets developers who wish to build source-based tools that implement customized analyses and optimizations for large-scale C, C++, and Fortran90 scientific computing applications (on the order of a million lines of code or more). However, much of this infrastructure can also be used to address problems in testing, and ROSE is by design broadly accessible to those without a formal compiler background. This paper details the interactions between testing of applications and the ways in which compiler technology can aid in the understanding of those applications. We emphasize the particular aspects of ROSE, such as support for the general analysis of whole programs, that are particularly well-suited to the testing research community and the scale of the …
Date: December 9, 2005
Creator: Quinlan, D; Ur, S & Vuduc, R
System: The UNT Digital Library
Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics (open access)

Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.
Date: December 9, 2008
Creator: Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke et al.
System: The UNT Digital Library
Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films (open access)

Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films

We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that reveal the underlying energetics driving the overall reversal mechanisms.
Date: December 9, 2008
Creator: Hauet, Thomas; Gunther, Christian M.; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter et al.
System: The UNT Digital Library
Multiscale integration schemes for jump-diffusion systems (open access)

Multiscale integration schemes for jump-diffusion systems

We study a two-time-scale system of jump-diffusion stochastic differential equations. We analyze a class of multiscale integration methods for these systems, which, in the spirit of [1], consist of a hybridization between a standard solver for the slow components and short runs for the fast dynamics, which are used to estimate the effect that the fast components have on the slow ones. We obtain explicit bounds for the discrepancy between the results of the multiscale integration method and the slow components of the original system.
Date: December 9, 2008
Creator: Givon, D. & Kevrekidis, I.G.
System: The UNT Digital Library
Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion (open access)

Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. these relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser ablation can be particularly convenient. The TRIDENT laser has been used to impart shocks and isentropic compression waves from {approx}1 to 200GPa in a range of elements and alloys, with diagnostics including surface velocimetry (line-imaging VISAR), surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically-driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response. These results will help to constrain acceptable tolerances on manufacturing, and possible …
Date: December 9, 2004
Creator: Swift, D. C.; Tierney, T. E.; Luo, S. N.; Paisley, D. L.; Kyrala, G. A.; Hauer, A. et al.
System: The UNT Digital Library
DEVELOPMENT OF AG-1 SECTION FI ON METAL MEDIA FILTERS - 9061 (open access)

DEVELOPMENT OF AG-1 SECTION FI ON METAL MEDIA FILTERS - 9061

Development of a metal media standard (FI) for ASME AG-1 (Code on Nuclear Air and Gas Treatment) has been under way for almost ten years. This paper will provide a brief history of the development process of this section and a detailed overview of its current content/status. There have been at least two points when dramatic changes have been made in the scope of the document due to feedback from the full Committee on Nuclear Air and Gas Treatment (CONAGT). Development of the proposed section has required resolving several difficult issues associated with scope; namely, filtering efficiency, operating conditions (media velocity, pressure drop, etc.), qualification testing, and quality control/acceptance testing. A proposed version of Section FI is currently undergoing final revisions prior to being submitted for balloting. The section covers metal media filters of filtering efficiencies ranging from medium (less than 99.97%) to high (99.97% and greater). Two different types of high efficiency filters are addressed; those units intended to be a direct replacement of Section FC fibrous glass HEPA filters and those that will be placed into newly designed systems capable of supporting greater static pressures and differential pressures across the filter elements. Direct replacements of FC HEPA filters …
Date: December 9, 2008
Creator: Adamson, D & Charles A. Waggoner, C
System: The UNT Digital Library
A three-level BDDC algorithm for Mortar discretizations (open access)

A three-level BDDC algorithm for Mortar discretizations

In this paper, a three-level BDDC algorithm is developed for the solutions of large sparse algebraic linear systems arising from the mortar discretization of elliptic boundary value problems. The mortar discretization is considered on geometrically non-conforming subdomain partitions. In two-level BDDC algorithms, the coarse problem needs to be solved exactly. However, its size will increase with the increase of the number of the subdomains. To overcome this limitation, the three-level algorithm solves the coarse problem inexactly while a good rate of convergence is maintained. This is an extension of previous work, the three-level BDDC algorithms for standard finite element discretization. Estimates of the condition numbers are provided for the three-level BDDC method and numerical experiments are also discussed.
Date: December 9, 2007
Creator: Kim, H. & Tu, X.
System: The UNT Digital Library
Electronic interactions between gold nanoclusters in constrainedgeometries (open access)

Electronic interactions between gold nanoclusters in constrainedgeometries

None
Date: December 9, 2005
Creator: Kim, Sang Hoon; Hwang, S.; Shon, Young-Seok; Ogletree, D. Frank & Salmeron, Miquel
System: The UNT Digital Library
Vector-vector production in photon-photon interactions (open access)

Vector-vector production in photon-photon interactions

Measurements of exclusive untagged /rho//sup 0//rho//sup 0/, /rho//phi/, K/sup *//bar K//sup */, and /rho/..omega.. production and tagged /rho//sup 0//rho//sup 0/ production in photon-photon interactions by the TPC/Two-Gamma experiment are reviewed. Comparisons to the results of other experiments and to models of vector-vector production are made. Fits to the data following a four quark model prescription for vector meson pair production are also presented. 10 refs., 9 figs.
Date: December 9, 1988
Creator: Ronan, M.T.
System: The UNT Digital Library
Integrated planning: A baseline development perspective (open access)

Integrated planning: A baseline development perspective

The FEMP Baseline establishes the basis for integrating environmental activity technical requirements with their cost and schedule elements. The result is a path forward to successfully achieving the FERMCO mission. Specific to cost management, the FEMP Baseline has been incorporate into the FERMCO Project Control System (PCS) to provide a time-phased budget plan against which contractor performance is measured with an earned value management system. The result is the Performance Measurement Baseline (PMB), an important tool for keeping cost under control.
Date: December 9, 1994
Creator: Clauss, L. & Chang, D.
System: The UNT Digital Library
The effect of process parameters on the surface finish of plasma polymers (open access)

The effect of process parameters on the surface finish of plasma polymers

The surface finish of plasma polymers deposited in an inductively coupled discharge were measured as a function of gas flow rates. Surface finish was measured both optically and by AFM. The process parameters of the plasma polymerization were found to effect the surface finish. The gases used were trans-2- butene and hydrogen for hydrocarbon polymers. For bromocarbon polymers we added ethylbromide. The smoothest hydrocarbon polymer coatings had an RMS surface finish better than 1 nm. Bumps 200 nm high spaced approximately 1 {mu}m apart grew on the surface of bromocarbon coatings when they were exposed to air. The composition of the bumps was found to be NH{sub 4}Br by XRD and XPS analysis. We believe that nitrogen (from a small leak or desorption) dissociates in the discharge and reacts with hydrogen to form ammonia. The ammonia then reacts with HBr, a dissociation product of ethylbromide, to form NH{sub 4}Br which is dispersed throughout the deposited layer. Humidity facilitates the transport of the NH{sub 4}Br to the surface where it crystallizes. Bump growth was prevented by either dry storage or overcoating with 3 {mu}m of hydrocarbon plasma polymer. Alternatively, the bumps could be washed from the surface with water.
Date: December 9, 1992
Creator: Letts, S. A.; Cook, R. C.; Welch, P.; McEachern, R. & Fearon, E.
System: The UNT Digital Library
From Crisis to Transition: The State of Russian Science Based on Focus Groups with Nuclear Physicists (open access)

From Crisis to Transition: The State of Russian Science Based on Focus Groups with Nuclear Physicists

The collapse of the Soviet system led to a sharp contraction of state funding for science. Formerly privileged scientists suddenly confronted miserly salaries (often paid late), plummeting social prestige, deteriorating research facilities and equipment, and few prospects for improvement. Many departed the field of science for more lucrative opportunities, both within Russia and abroad. The number of inventions, patent applications, and publications by Russian scientists declined. Reports of desperate nuclear physicists seeking work as tram operators and conducting hunger strikes dramatized the rapid collapse of one of the contemporary world's most successful scientific establishments. Even more alarming was the 1996 suicide of Vladimir Nechai, director of the second largest nuclear research center in Russia (Chelyabinsk-70, now known as Snezhinsk). Nechai, a respected theoretical physicist who spent almost 40 years working on Soviet and Russian nuclear programs, killed himself because he could no longer endure his inability to rectify a situation in which his employees had not been paid for more than 5 months and were ''close to starvation.'' The travails of Russia's scientists sparked interest in the West primarily because of the security threat posed by their situation. The seemingly relentless crisis in science raised fears that disgruntled scientists might …
Date: December 9, 2001
Creator: Gerber, T P & Ball, D Y
System: The UNT Digital Library
The WARP Code: Modeling High Intensity Ion Beams (open access)

The WARP Code: Modeling High Intensity Ion Beams

The Warp code, developed for heavy-ion driven inertial fusion energy studies, is used to model high intensity ion (and electron) beams. Significant capability has been incorporated in Warp, allowing nearly all sections of an accelerator to be modeled, beginning with the source. Warp has as its core an explicit, three-dimensional, particle-in-cell model. Alongside this is a rich set of tools for describing the applied fields of the accelerator lattice, and embedded conducting surfaces (which are captured at sub-grid resolution). Also incorporated are models with reduced dimensionality: an axisymmetric model and a transverse ''slice'' model. The code takes advantage of modern programming techniques, including object orientation, parallelism, and scripting (via Python). It is at the forefront in the use of the computational technique of adaptive mesh refinement, which has been particularly successful in the area of diode and injector modeling, both steady-state and time-dependent. In the presentation, some of the major aspects of Warp will be overviewed, especially those that could be useful in modeling ECR sources. Warp has been benchmarked against both theory and experiment. Recent results will be presented showing good agreement of Warp with experimental results from the STS500 injector test stand. Additional information can be found on …
Date: December 9, 2004
Creator: Grote, D. P.; Friedman, A.; Vay, J. L. & Haber, I.
System: The UNT Digital Library
Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings (open access)

Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings

Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this paper, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting beams, to the work of Sacherer on a bunched beam, and ending with the Oide and Yokoya method of discretization. This theoretical survey will be supplemented with key experimental results over the years. Finally, we will describe the recent theoretical development of utilizing the Laguerre polynomials in the presence of potential-well distortion. This self-consistent method will be applied to study the microwave instability driven the impedances due to the coherent synchrotron radiation. Over the past quarter century, there has been steady progress toward smaller transverse emittances in electron storage rings used for synchrotron light sources, from tens of nm decades ago to the nm range recently. In contrast, there is not much progress made in the longitudinal plane. For an electron bunch in a typical …
Date: December 9, 2011
Creator: Cai, Y.
System: The UNT Digital Library
Solid State NMR Investigations of Chain Dynamics and Network Order in Model Poly(dimethylsiloxane) Elastomers (open access)

Solid State NMR Investigations of Chain Dynamics and Network Order in Model Poly(dimethylsiloxane) Elastomers

This work is at a relatively early stage, however it has been demonstrated that we can reliably probe basic network architectures using the MQ-NMR technique. The initial results are in good agreement with what is known from standard network theory and will serve as a basis for the study of progressively increasing structural complexity in Siloxane network systems.
Date: December 9, 2010
Creator: Lewicki, J P; Mayer, B P; Wilson, T S; Chinn, S C & Maxwell, R S
System: The UNT Digital Library
Constructing Amplitudes from Their Soft Limits (open access)

Constructing Amplitudes from Their Soft Limits

The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.
Date: December 9, 2011
Creator: Boucher-Veronneau, Camille & Larkoski, Andrew J.
System: The UNT Digital Library
Main Injector Particle Production Experiment (MIPP) at Fermilab (open access)

Main Injector Particle Production Experiment (MIPP) at Fermilab

The Main Injector Particle Production Experiment at Fermilab uses particle beams of charged pions, kaons, proton and anti-proton with beam momenta of 5 to 90 GeV/c and thin targets spanning the periodic table from (liquid) hydrogen to uranium to measure particle production cross sections in a full acceptance spectrometer with charged particle identification for particles from 0.1 to 120 GeV/c using Time Projection Chamber, Time of Flight, multicell Cherenkov, and Ring Imaging Cherenkov detectors and Calorimeter for neutrons. Particle production using 120 GeV/c protons from Main Injector on the MINOS target was also measured. We describe the physics motivation to perform such cross section measurements and highlight the impact of hadronic interaction data on neutrino physics. Recent results on forward neutron cross sections and analysis of MINOS target data are also presented.
Date: December 9, 2010
Creator: Mahajan, Sonam
System: The UNT Digital Library
Flux and Photon Spectral Index Distributions of Fermi-LAT Blazars and Contribution to the Extragalactic Gamma-ray Background (open access)

Flux and Photon Spectral Index Distributions of Fermi-LAT Blazars and Contribution to the Extragalactic Gamma-ray Background

We present a determination of the distributions of gamma-ray flux - the so called LogN-LogS relation - and photon spectral index for the 352 blazars detected with a greater than approximately seven sigma detection threshold and located above {+-} 20{sup o} Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true LogN-LogS counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation among the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law of slopes -2.37 {+-} 0.13 and -1.70 {+-} 0.26, and the intrinsic photon index distribution can be represented by a Gaussian with mean 2.41 {+-} 0.13 and 1{sigma} …
Date: December 9, 2011
Creator: Singal, J.; /KIPAC, Menlo Park /SLAC /Stanford U.; Petrosian, V.; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.; Ajello, M. & /KIPAC, Menlo Park /SLAC /Stanford U.
System: The UNT Digital Library
Lessons Learned From a Site-Wide Power Outage (open access)

Lessons Learned From a Site-Wide Power Outage

None
Date: December 9, 2011
Creator: Bartelt, John
System: The UNT Digital Library
MiniBooNE "Windows on the Universe" (open access)

MiniBooNE "Windows on the Universe"

Progress in the last few decades has left neutrino physics with several vexing issues. Among them are the following questions: (1) Why are lepton mixing angles so different from those in the quark sector? (2) What is the most probable range of the reactor mixing angle? (3) Is the atmospheric mixing angle maximal? (4) What is the number of fermion generations? These are some of the issues that neutrino science hopes to study; this article will explore these questions as part of a more general scientific landscape, and will discuss the part MiniBooNE might play in this exploration. We discuss the current state of measurements taken by MiniBooNE, and emphasize the uniqueness of neutrino oscillations as an important probe into the 'Windows on the Universe.'
Date: December 9, 2010
Creator: Stefanski, Ray
System: The UNT Digital Library
Cartan calculus on quantum Lie algebras (open access)

Cartan calculus on quantum Lie algebras

A generalization of the differential geometry of forms and vector fields to the case of quantum Lie algebras is given. In an abstract formulation that incorporates many existing examples of differential geometry on quantum spaces we combine an exterior derivative, inner derivations, Lie derivatives, forms and functions au into one big algebra, the ``Cartan Calculus.``
Date: December 9, 1993
Creator: Schupp, P.; Watts, P. & Zumino, B.
System: The UNT Digital Library
Reactor Operations Management Plan (open access)

Reactor Operations Management Plan

The K-Reactor last operated in April 1988. At that time, K-Reactor was one of three operating reactors at the Savannah River Site (SRS). Following an incident in P-Reactor in August 1988, it was decided to discontinue SRS reactor operation and conduct an extensive program to upgrade operating practices and plant hardware prior to restart of any of the reactors. The K-reactor was the first of three reactors scheduled to resume production. At the present time, it is the only reactor with planned restart. WSRC assumed management of SRS on April 1, 1989. WSRC established the Safety Basis for Restart and a listing of the actions planned to satisfy the Safety Basis. In consultation with DOE, it was determined that proper management of the restart activities would require a single plan that integrated the numerous activities. The plan was entitled the Reactor Operations Management Plan and is referred to simply as the ROMP. The initial version of ROMP was produced in July of 1989. Subsequent modifications led to Revision 3 which was approved by DOE in May, 1990. Other changes were made in a formal change process, resulting in the latest version, Revision 5, being issued in October, 1990. The ROMP …
Date: December 9, 1991
Creator: Rice, Paul D.
System: The UNT Digital Library
Impedance-power effects on plasma polymer surface finish using a helical resonator discharge (open access)

Impedance-power effects on plasma polymer surface finish using a helical resonator discharge

Plasma polymerized organic coatings are used in the fabrication of targets for experiments in the Inertial Confinement Fusion (ICF) program at Lawrence Livermore National Laboratory. The authors are performing experiments to understand the process conditions leading to the preparation of smooth ({approx}100{Angstrom}) plasma polymer surfaces while maintaining the highest deposition rate possible. It had been reported by Howling et al., that the formation of particulate matter in the deposition of silicon by the plasma reaction of silane affected the plasma impedance. This suggested that experiments designed to examine the correlation of surface texture with plasma impedance would be of interest. Furthermore, it is possible that an impedance change may cause a change in the power coupling efficiency from the transmitter to the plasma. Preliminary work in the authors laboratory indicated that the reactor temperature influenced the surface texture. The focus of this paper is to carefully examine the effects of reactor temperature on the surface texture of the plasma polymer, ensuring constant reactor conditions especially with respect to rf power.
Date: December 9, 1992
Creator: Brusasco, R.; Ferguson, S. W. & Stever, R.
System: The UNT Digital Library