Resource Type

Language

Analysis of oxygen on and in beryllium using 2 MeV helium ions (open access)

Analysis of oxygen on and in beryllium using 2 MeV helium ions

Analysis of oxygen on beryllium can be routinely performed using helium-ion backscattering (RBS). However, determination of the bulk oxygen concentration by this technique is limited to about 350 atomic parts per million (appM). We have performed simultaneous RBS and particle-induced x-ray emission (PIXE) measurements to improve the detection limit for bulk oxygen. The RBS measurements allowed determination of the surface oxygen before and after in-situ sputter cleaning by argon ions in an ultra-high-vacuum system. PIXE measurements of specimens with surfaces maintained clean by sputtering permitted assessment of the concentration of oxygen in the bulk. For our geometry and detector sensitivities, 90% of the oxygen x-ray signal originated in the first 2.1 ..mu..m of the beryllium and a detection limit of 10 appM was found. 12 refs., 3 figs.
Date: October 2, 1986
Creator: Musket, R.G.
System: The UNT Digital Library
Review of the state of the art in personnel neutron monitoring with solid state detectors (open access)

Review of the state of the art in personnel neutron monitoring with solid state detectors

Albedo systems are the mainstay at many facilities and continue to be refined. Advanced electrochemical etching techniques for CR-39 now yield a dose equivalent response that is nearly constant from 0.1 to 4.0 MeV. Recent studies include use of converters to enhance CR-39 response at both low and high energies. Methods have been suggested for use of CR-39, either alone or in conjunction with albedo and other detectors to provide spectral information as a step to more accurate dosimetry. Limitations in the use of CR-39 primarily center on the lack of consistent, high-quality, dosimetry-grade material, significant angular dependence, and poor dose equivalent response at both low and high energies. Work continues on silicon diodes, with some new designs. The most attractive new dosimetry technique is the bubble-damage or superheated drop detector. Metal-on-silicon (MOS) microelectronics present exciting possibilities for the future. 25 refs., 6 figs.
Date: October 2, 1987
Creator: Griffith, R.V.
System: The UNT Digital Library
Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure (open access)

Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure

Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.
Date: October 2, 2007
Creator: Berryman, J.G.
System: The UNT Digital Library
DiMES Studies of Temperature Dependence of Carbon Erosion and Re-Deposition in the DIII-D Divertor (open access)

DiMES Studies of Temperature Dependence of Carbon Erosion and Re-Deposition in the DIII-D Divertor

A strong effect of a moderately elevated surface temperature on net carbon deposition and deuterium co-deposition in the DIII-D divertor was observed under detached conditions. A DiMES sample with a gap 2 mm wide and 18 mm deep was exposed to lower-single-null (LSN) L-mode plasmas first at room temperature, and then at 200 C. At the elevated temperature, deuterium co-deposition in the gap was reduced by an order of magnitude. At the plasma-facing surface of the heated sample net carbon erosion was measured at a rate of 3 nm/s, whereas without heating net deposition is normally observed under detachment. In a related experiment three sets of molybdenum mirrors recessed 2 cm below the divertor floor were exposed to identical LSN ELMy H-mode discharges. The first set of mirrors exposed at ambient temperature exhibited net carbon deposition at a rate of up to 3.7 nm/s and suffered a significant drop in reflectivity. In contrast, two other mirror sets exposed at elevated temperatures between 90 C and 175 C exhibited virtually no carbon deposition.
Date: October 2, 2006
Creator: Rudakov, D.; Jacob, W.; Krieger, K.; Litnovsky, A.; Philipps, V.; West, W. et al.
System: The UNT Digital Library
Introduction to Electroweak Symmetry Breaking (open access)

Introduction to Electroweak Symmetry Breaking

The Standard Model (SM) is the backbone of elementary particle physics-not only does it provide a consistent framework for studying the interactions of quark and leptons, but it also gives predictions which have been extensively tested experimentally. In these notes, I review the electroweak sector of the Standard Model, discuss the calculation of electroweak radiative corrections to observables, and summarize the status of SM Higgs boson searches. Despite the impressive experimental successes, however, the electroweak theory is not completely satisfactory and the mechanism of electroweak symmetry breaking is untested. I will discuss the logic behind the oft-repeated statement: 'There must be new physics at the TeV scale'. These lectures reflect my strongly held belief that upcoming results from the LHC will fundamentally change our understanding of electroweak symmetry breaking. In these lectures, I review the status of the electroweak sector of the Standard Model, with an emphasis on the importance of radiative corrections and searches for the Standard Model Higgs boson. A discussion of the special role of the TeV energy scale in electroweak physics is included.
Date: October 2, 2008
Creator: Dawson,S.
System: The UNT Digital Library
Measurement of Transverse Single-Spin Asymmetries for Di-JetProduction in Proton-Proton Collisions at sqrt s = 200 GeV (open access)

Measurement of Transverse Single-Spin Asymmetries for Di-JetProduction in Proton-Proton Collisions at sqrt s = 200 GeV

We report the first measurement of the opening angledistribution between pairs of jets produced in high-energy collisions oftransversely polarized protons. The measurement probes (Sivers)correlations between the transverse spin orientation of a proton and thetransverse momentum directions of its partons. With both beams polarized,the wide pseudorapidity (-1 leq eta leq +2) coverage for jets permitsseparation of Sivers functions for the valence and sea regions. Theresulting asymmetries are all consistent with zero and considerablysmaller than Sivers effects observed in semi-inclusive deep inelasticscattering (SIDIS). We discuss theoretical attempts to reconcile the newresults with the sizable transverse spin effects seen in SIDIS andforward hadron production in pp collisions.
Date: October 2, 2007
Creator: Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System: The UNT Digital Library
Telomere dysfunction and cell survival: Roles for distinct TIN2-containing complexes (open access)

Telomere dysfunction and cell survival: Roles for distinct TIN2-containing complexes

Telomeres are maintained by three DNA binding proteins (TRF1, TRF2 and POT1), and several associated factors. One factor, TIN2, binds TRF1 and TRF2 directly and POT1 indirectly. Along with two other proteins, TPP1 and hRap1, these form a soluble complex that may be the core telomere maintenance complex. It is not clear whether sub-complexes also exist in vivo. We provide evidence for two TIN2 sub-complexes with distinct functions in human cells. We isolated these two TIN2 sub-complexes from nuclear lysates of unperturbed cells and cells expressing TIN2 mutants TIN2-13, TIN2-15C, which cannot bind TRF2 or TRF1, respectively. In cells with wild-type p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere uncapping and eventual growth arrest. In cells lacking p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere dysfunction and cell death. Our findings suggest that distinct TIN2 complexes exist, and that TIN2-15C-sensitive subcomplexes are particularly important for cell survival in the absence of functional p53.
Date: October 2, 2007
Creator: Kim, Sahn-ho; Davalos, Albert R.; Heo, Seok-Jin; Rodier, Francis; Zou, Ying; Beausejour, Christian et al.
System: The UNT Digital Library
Toward a Mesoscale Model for the Dynamics of Polymer Solutions (open access)

Toward a Mesoscale Model for the Dynamics of Polymer Solutions

To model entire microfluidic systems containing solvated polymers we argue that it is necessary to have a numerical stability constraint governed only by the advective CFL condition. Advancements in the treatment of Kramers bead-rod polymer models are presented to enable tightly-coupled fluid-particle algorithms in the context of system-level modeling.
Date: October 2, 2006
Creator: Miller, G H & Trebotich, D
System: The UNT Digital Library
Compton scattering measurements from dense plasmas (open access)

Compton scattering measurements from dense plasmas

Compton scattering has been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.
Date: October 2, 2007
Creator: Glenzer, S. H.; Neumayer, P.; Doeppner, T.; Landen, L.; Lee, R. W.; Wallace, R. et al.
System: The UNT Digital Library
MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on Angular Scales of 10' to 5 Degrees (open access)

MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on Angular Scales of 10' to 5 Degrees

We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of MAXIMA. MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg region of the sky with 10' resolution at frequencies of 150, 240 and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields a power spectrum for the CMB anisotropy over the range 36 {le} {ell} {le} 785. The spectrum shows a peak with an amplitude of 78 {+-} 6 {mu}K at {ell} {approx_equal} 220 and an amplitude varying between {approx} 40 {mu}K and {approx} 50 {mu}K for 400 {approx}< {ell} {approx}< 785.
Date: October 2, 2000
Creator: Ade, P.; Balbi, A.; Bock, J.; Borrill, J.; Boscaleri, A.; deBernardis, P. et al.
System: The UNT Digital Library
The Genetically Remote Pathogenic Strain NVH391-98 of the Bacillus cereus Group Represents the Cluster of Thermophilic Strains (open access)

The Genetically Remote Pathogenic Strain NVH391-98 of the Bacillus cereus Group Represents the Cluster of Thermophilic Strains

Bacteria of the Bacillus cereus group are known to cause food poisoning. A rare phylogenetically remote strain, NVH391-98, was recently characterized to encode a particularly efficient cytotoxin K presumably responsible for food poisoning. This pathogenic strain and its close relatives can be phenotypically distinguished from other strains of the B. cereus group by the inability to grow at temperatures below 17 degrees C and by the ability to grow at temperatures from 48 to 53 degrees C. A temperate phage, phBC391A2, residing in the genome of NVH391-98 allows us to distinguish the three known members of this thermophilic strain cluster.
Date: October 2, 2007
Creator: Auger, Sandrine; Galleron, Nathalie; Bidnenko, Elena; Ehrlich, S. Dusko; Lapidus, Alla & Sorokin, Alexei
System: The UNT Digital Library
Java Tool Framework for Automation of Hardware Commissioning and Maintenance Procedures (open access)

Java Tool Framework for Automation of Hardware Commissioning and Maintenance Procedures

The National Ignition Facility (NIF) is a 192-beam laser system designed to study high energy density physics. Each beam line contains a variety of line replaceable units (LRUs) that contain optics, stepping motors, sensors and other devices to control and diagnose the laser. During commissioning and subsequent maintenance of the laser, LRUs undergo a qualification process using the Integrated Computer Control System (ICCS) to verify and calibrate the equipment. The commissioning processes are both repetitive and tedious when we use remote manual computer controls, making them ideal candidates for software automation. Maintenance and Commissioning Tool (MCT) software was developed to improve the efficiency of the qualification process. The tools are implemented in Java, leveraging ICCS services and CORBA to communicate with the control devices. The framework provides easy-to-use mechanisms for handling configuration data, task execution, task progress reporting, and generation of commissioning test reports. The tool framework design and application examples will be discussed.
Date: October 2, 2007
Creator: Ho, J. C.; Fisher, J. M.; Gordon, J. B.; Lagin, L. J. & West, S. L.
System: The UNT Digital Library
Olivine-FeS Partial-Melt (open access)

Olivine-FeS Partial-Melt

The figure shows Fe-S-filled melt channels in olivine created at high temperature and pressure. The 3D image was obtained on Beamline 8.3.2 at the Advanced Light Source, Lawrence Berkeley Laboratory, with a spatial resolution of better than two microns (bar is 10 microns). Permeability of Fe-S melts in olivine at high temperatures and pressures provides an important constraint on models of planetary core formation. Permeability must be inferred from empirical relationships based on microstructure. To date, estimates of permeability have varied by more than five orders of magnitude. To provide more accurate constraints, we used high-resolution synchrotron radiation computed tomography to image the three-dimensional network of melt-containing pores in an olivine matrix, and calculated the permeability directly by solving the equations of Stokes flow through the actual pore network using a lattice-Boltzmann approach. These calculations provide an independent constraint on models of planetary core formation.
Date: October 2, 2006
Creator: Roberts, J.; Siebert, J.; Ryerson, F. J. & Kinney, J.
System: The UNT Digital Library
RHIC Performance with polarized protons in run-6 (open access)

RHIC Performance with polarized protons in run-6

In this study, an array of vibration measurements at the undisturbed NSLS II site has been performed in order to establish the 'green-field' vibration environment and its spectral characteristics. The interaction of the green-field vibration environment with the NSLS II accelerator structure and the quantification of the storage ring vibration, both in terms of amplitude and spectral content have been assessed through a state-of-the-art wave propagation and scattering analysis. This paper focuses on the wave propagation and scattering aspect as well as on the filtering effects of accelerator structural parameters.
Date: October 2, 2006
Creator: Ptitsyn, V.; Ahrens, L.; Bai, M.; Beebe-Wang, J.; Blaskiewicz, M.; Bravar, S. et al.
System: The UNT Digital Library
The VISTA spacecraft: Advantages of ICF (Inertial Confinement Fusion) for interplanetary fusion propulsion applications (open access)

The VISTA spacecraft: Advantages of ICF (Inertial Confinement Fusion) for interplanetary fusion propulsion applications

Inertial Confinement Fusion (ICF) is an attractive engine power source for interplanetary manned spacecraft, especially for near-term missions requiring minimum flight duration, because ICF has inherent high power-to-mass ratios and high specific impulses. We have developed a new vehicle concept called VISTA that uses ICF and is capable of round-trip manned missions to Mars in 100 days using A.D. 2020 technology. We describe VISTA's engine operation, discuss associated plasma issues, and describe the advantages of DT fuel for near-term applications. Although ICF is potentially superior to non-fusion technologies for near-term interplanetary transport, the performance capabilities of VISTA cannot be meaningfully compared with those of magnetic-fusion systems because of the lack of a comparable study of the magnetic-fusion systems. We urge that such a study be conducted.
Date: October 2, 1987
Creator: Orth, C.D.; Klein, G.; Sercel, J.; Hoffman, N.; Murray, K. & Chang-Diaz, F.
System: The UNT Digital Library
Transport/installation of the MFTF magnet and magnetic-field measurements (open access)

Transport/installation of the MFTF magnet and magnetic-field measurements

After the two C-coils were joined to form a yin-yang magnet, it was moved to the Mirror Fusion Test Facility (MFTF) at the Lawrence Livermore National Laboratory. Additional preparatory work was done before the magnet assembly could be moved into the vacuum vessel for final hookup. Apparatus was designed and built to determine magnet mechanical and magnetic centerlines and establish a magnetic-field profile between the mirror points and yin-yang center. Hall probes were installed to measure magnetic fields during startup and operation. A system using linear potentiometers was used to detect magnet movement during operation.
Date: October 2, 1981
Creator: Hanson, C. L.; Hinkle, R. E. & DePue, D. W.
System: The UNT Digital Library
Machine and plasma diagnostic instrumentation systems for the Tandem Mirror Experiment Upgrade (open access)

Machine and plasma diagnostic instrumentation systems for the Tandem Mirror Experiment Upgrade

To evaluate performance of a second generation Tandem Mirror Machine, an extensive instrumentation system is being designed and installed as part of the major device fabrication. The systems listed will be operational during the start-up phase of the TMX Upgrade machine and provide bench marks for future performance data. In addition to plasma diagnostic instrumentation, machine parameter monitoring systems will be installed prior to machine operation. Simultaneous recording of machine parameters will permit evaluation of plasma parameters sensitive to machine conditions.
Date: October 2, 1981
Creator: Coutts, G. W.; Coffield, F. E.; Lang, D. D. & Hornady, R. S.
System: The UNT Digital Library
Practical applications of coherent transition radiation (open access)

Practical applications of coherent transition radiation

The predictable nature of transition radiation (TR) emissions has been demonstrated under a wide variety of experimental conditions. The reliable character of TR allows the design of specific practical applications that use emissions from the optical to the x-ray spectral regions. Applications often can be enhanced by the spatial coherence of TR, and some have become highly developed. New applications may be developed through the use of other related radiation mechanisms. 20 refs., 3 figs.
Date: October 2, 1987
Creator: Moran, M. J.
System: The UNT Digital Library
The LLNL (Lawrence Livermore National Laboratory) ICF (Inertial Confinement Fusion) Program: Progress toward ignition in the Laboratory (open access)

The LLNL (Lawrence Livermore National Laboratory) ICF (Inertial Confinement Fusion) Program: Progress toward ignition in the Laboratory

The Inertial Confinement Fusion (ICF) Program at the Lawrence Livermore National Laboratory (LLNL) has made substantial progress in target physics, target diagnostics, and laser science and technology. In each area, progress required the development of experimental techniques and computational modeling. The objectives of the target physics experiments in the Nova laser facility are to address and understand critical physics issues that determine the conditions required to achieve ignition and gain in an ICF capsule. The LLNL experimental program primarily addresses indirect-drive implosions, in which the capsule is driven by x rays produced by the interaction of the laser light with a high-Z plasma. Experiments address both the physics of generating the radiation environment in a laser-driven hohlraum and the physics associated with imploding ICF capsules to ignition and high-gain conditions in the absence of alpha deposition. Recent experiments and modeling have established much of the physics necessary to validate the basic concept of ignition and ICF target gain in the laboratory. The rapid progress made in the past several years, and in particular, recent results showing higher radiation drive temperatures and implosion velocities than previously obtained and assumed for high-gain target designs, has led LLNL to propose an upgrade of …
Date: October 2, 1990
Creator: Storm, E.; Batha, S. H.; Bernat, T. P.; Bibeau, C.; Cable, M. D.; Caird, J. A. et al.
System: The UNT Digital Library
Limits on the masses of supersymmetric particles from 1. 8 TeV p p collisions (open access)

Limits on the masses of supersymmetric particles from 1. 8 TeV p p collisions

Preliminary analysis of p{bar p} collision events at {radical}s = 1.8 TeV using events with large missing transverse energy and on two (four) jets in a minimal SUSY model places new limits on the masses of squarks (gluinos). The data sample (4 pb{sup {minus}1}) was taken in 1988--89 and is approximately 160 times as large as the data sample from our earlier 1987 run (25 nb{sup {minus}1}). 5 refs., 1 fig.
Date: October 2, 1990
Creator: Beretvas, A.
System: The UNT Digital Library
Ion cyclotron resonance heating (ICRH) start-up antenna for the mirror fusion test facility (MFTF-B) (open access)

Ion cyclotron resonance heating (ICRH) start-up antenna for the mirror fusion test facility (MFTF-B)

The purpose of the ICRH start-up antenna on MFTF-B is to heat the plasma and control the ion distribution as the density increases during start-up. The antenna, consisting of two center fed half turn loops phased 180/sup 0/ apart, has been designed for 1 MW of input power, with a goal of coupling 400 kW into the ions. To vary the heating frequency relative to the local ion cyclotron frequency, the antenna is tunable over a range from 7.5 to 12.5 MHz. The thermal requirements common to low duty cycle ICRH antennas are especially severe for the MFTF-B antenna. The stress requirements are also unique, deriving from the possibility of seismic activity or JxB forces if the magnets unexpectedly quench. Considerable attention has been paid to contact control at high current bolt-up joints, and arranging geometries so as to minimize the possibility of voltage breakdown.
Date: October 2, 1985
Creator: McCarville, T.M. & Romesser, T.E.
System: The UNT Digital Library
Multiscale modeling of MEMS dynamics and failure (open access)

Multiscale modeling of MEMS dynamics and failure

This work studies multiscale phenomena in silicon micro-resonators which comprise the mechanical components of next-generation Micro-Electro-Mechanical Systems (MEMS). Unlike their larger relatives, the behavior of these sub-micron MEMS is not described well by conventional continuum models and finite elements, but it is determined appreciably by the interplay between physics at the Angstrom, nanometer and micron scales. As device sizes are reduced below the micron scale, atomistic processes cause systematic deviations from the behavior predicted by conventional continuum elastic theory. [1] These processes cause anomalous surface effects in the resonator frequency and quality factor-even for single crystal devices with clean surfaces due to thermal fluctuations. The simulation of these atomistic effects is a challenging problem due to the large number of atoms involved and due to the fact that they are finite temperature phenomena. Our simulations include up to two million atoms in the device itself, and hundreds of millions more are in the proximal regions of the substrate. A direct, atomistic simulation of the motion of this many atoms is prohibitive, and it would be inefficient. The micron-scale processes in the substrate are well described by finite elements, and an atomistic simulation is not required. On the other hand, atomistic …
Date: October 2, 2000
Creator: Rudd, R E
System: The UNT Digital Library
Phase Competition in Trisected Superconducting Dome (open access)

Phase Competition in Trisected Superconducting Dome

None
Date: October 2, 2012
Creator: Vishik, I.M.; Hashimoto, M; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui et al.
System: The UNT Digital Library
Development of high-creep-strength molybdenum and tungsten alloys by the internal nitriding process (open access)

Development of high-creep-strength molybdenum and tungsten alloys by the internal nitriding process

Substantial increases in the high-temperature creep strength of Mo-Hf alloys can be obtained by internal nitriding. The creep resistance of internally nitrided Mo-1.86 wt % Hf is more than 100 times greater than that of other commercially available molybdenum-base alloys. The HfN precipitates appear to be stable over long times at temperatures near 1600 K. Internally nitrided Mo-Hf alloys appear to be good candidates for fabrication of components of space power systems where the ratio of high-temperature strength to weight is important. They are particularly good candidates for components that can be fabricated from the lower-strength unnitrided alloy and subsequently nitrided to provide high-temperature strength.
Date: October 2, 1986
Creator: Mitchell, J. B.
System: The UNT Digital Library