Transition energy correlations in the three-body continuum of Borromean halo nuclei (open access)

Transition energy correlations in the three-body continuum of Borromean halo nuclei

Energy correlations in transitions from the bound state to the three-body continuum of Borromean halo nuclei are considered. A core+n+n three-body cluster model which reproduces experimentally known properties of {sup 6}He and {sup 11}Li has been used to study low-lying resonances and soft modes. The analysis of the correlated responses in {sup 6}He shows that in the case of the narrow three-body 2{sub 1}{sup +} resonance the transition energy correlations are the same as in the intrinsic correlated structure in 3 {yields} 3 scattering. They differ significantly for wide 2{sub 2}{sup +}, 1{sub 1}{sup +} resonances, and also for the soft dipole and monopole modes, where, due to the transition operators, the intertwining of the ground state and the three-body continuum plays a significant role.
Date: June 5, 2007
Creator: Danilin, B V; Vaagen, J S; Rogde, T; Ershov, S N; Thompson, I J & Zhukov, M V
Object Type: Article
System: The UNT Digital Library
High-Resolution Spectroscopy of K-shell Praseodymium with a High-Energy Calorimeter (open access)

High-Resolution Spectroscopy of K-shell Praseodymium with a High-Energy Calorimeter

We present a measurement of the K-shell spectrum of He-like through Be-like praseodymium ions trapped in the Livermore SuperEBIT electron beam ion trap using a bismuth absorber pixel on the XRS/EBIT microcalorimeter. This measurement is the first of its kind where the n=2 to n=1 transitions of the various charge states are spectroscopically resolved. The measured transition energies are compared with theoretical calculations from several atomic codes.
Date: June 5, 2007
Creator: Thorn, D B; Brown, G V; Clementson, J T; Chen, H; Chen, M H; Beiersdorfer, P et al.
Object Type: Article
System: The UNT Digital Library
World Best Practice Energy Intensity Values for SelectedIndustrial Sectors (open access)

World Best Practice Energy Intensity Values for SelectedIndustrial Sectors

"World best practice" energy intensity values, representingthe most energy-efficient processes that are in commercial use in atleast one location worldwide, are provided for the production of iron andsteel, aluminium, cement, pulp and paper, ammonia, and ethylene. Energyintensity is expressed in energy use per physical unit of output for eachof these commodities; most commonly these are expressed in metric tonnes(t). The energy intensity values are provided by major energy-consumingprocesses for each industrial sector to allow comparisons at the processlevel. Energy values are provided for final energy, defined as the energyused at the production facility as well as for primary energy, defined asthe energy used at the production facility as well as the energy used toproduce the electricity consumed at the facility. The "best practice"figures for energy consumption provided in this report should beconsidered as indicative, as these may depend strongly on the materialinputs.
Date: June 5, 2007
Creator: Worrell, Ernst; Price, Lynn; Neelis, Maarten; Galitsky,Christina & Zhou, Nan
Object Type: Report
System: The UNT Digital Library
Ionization efficiency studies for xenon ions with thesuperconducting ECR ion source VENUS (open access)

Ionization efficiency studies for xenon ions with thesuperconducting ECR ion source VENUS

Ionization efficiency studies for high charge state xenon ions using a calibrated gas leak are presented. A 75% enriched {sup 129}Xe gas leak with a gas flow equivalent to 5.11p{mu}A was used in all the measurements. The experiments were performed at the VENUS (Versatile ECR ion source for Nuclear Science) ion source for 18 GHz, 28 GHz and double frequency operation. Overall, total ionization efficiencies close to 100% and ionization efficiencies into a single charge state up to 22% were measured. The influence of the biased disk on the ionization efficiency was studied and the results were somewhat surprising. When the biased disk was removed from the plasma chamber, the ionization efficiency was dramatically reduced for single frequency operation. However, using double frequency heating the ionization efficiencies achieved without the biased disk almost matched the ionization efficiencies achieved with the biased probe. In addition, we have studied the influence of the support gas on the charge state distribution of the xenon ions. Either pure oxygen or a mixture of oxygen and helium were used as support gases. The addition of a small amount of helium can increase the ionization efficiency into a single charge state by narrowing the charge state …
Date: June 5, 2007
Creator: Leitner, Daniela; Lyneis, Claude M.; Todd, DamonS. & Tarvainen,Olli
Object Type: Article
System: The UNT Digital Library
Kinetic-Ion Simulations Addressing Whether Ion Trapping Inflates Stimulated Brillouin Backscattering Reflectivities (open access)

Kinetic-Ion Simulations Addressing Whether Ion Trapping Inflates Stimulated Brillouin Backscattering Reflectivities

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Date: June 5, 2007
Creator: Cohen, B; Williams, E & Vu, H
Object Type: Article
System: The UNT Digital Library
Edge Simulation Laboratory Progress and Plans (open access)

Edge Simulation Laboratory Progress and Plans

The Edge Simulation Laboratory (ESL) is a project to develop a gyrokinetic code for MFE edge plasmas based on continuum (Eulerian) techniques. ESL is a base-program activity of OFES, with an allied algorithm research activity funded by the OASCR base math program. ESL OFES funds directly support about 0.8 FTE of career staff at LLNL, a postdoc and a small fraction of an FTE at GA, and a graduate student at UCSD. In addition the allied OASCR program funds about 1/2 FTE each in the computations directorates at LBNL and LLNL. OFES ESL funding for LLNL and UCSD began in fall 2005, while funding for GA and the math team began about a year ago. ESL's continuum approach is a complement to the PIC-based methods of the CPES Project, and was selected (1) because of concerns about noise issues associated with PIC in the high-density-contrast environment of the edge pedestal, (2) to be able to exploit advanced numerical methods developed for fluid codes, and (3) to build upon the successes of core continuum gyrokinetic codes such as GYRO, GS2 and GENE. The ESL project presently has three components: TEMPEST, a full-f, full-geometry (single-null divertor, or arbitrary-shape closed flux surfaces) code …
Date: June 5, 2007
Creator: Cohen, R
Object Type: Report
System: The UNT Digital Library
Modeling the Galaxy Three-Point Correlation Function (open access)

Modeling the Galaxy Three-Point Correlation Function

We present new theoretical predictions for the galaxy three-point correlation function (3PCF) using high-resolution dissipationless cosmological simulations of a flat Lambda CDM Universe which resolve galaxy-size halos and subhalos. We create realistic mock galaxy catalogs by assigning luminosities and colors to dark matter halos and subhalos, and we measure the reduced 3PCF as a function of luminosity and color in both real and redshift space. As galaxy luminosity and color are varied, we find small differences in the amplitude and shape dependence of the reduced 3PCF, at a level qualitatively consistent with recent measurements from the SDSS and 2dFGRS. We confirm that discrepancies between previous 3PCF measurements can be explained in part by differences in binning choices. We explore the degree to which a simple local bias model can fit the simulated 3PCF. The agreement between the model predictions and galaxy 3PCF measurements lends further credence to the straightforward association of galaxies with CDM halos and subhalos.
Date: June 5, 2007
Creator: Marin, Felipe; /Chicago U., Astron. Astrophys. Ctr.; Wechsler, Risa; /Chicago U., Astron. Astrophys. Ctr. /KIPAC, Menlo Park /SLAC; Frieman, Joshua A.; /Chicago U., Astron. Astrophys. Ctr. /Fermilab et al.
Object Type: Article
System: The UNT Digital Library
The Mean and Scatter of the Velocity Dispersion-Optical Richness Relation for MaxBCG Galaxy Clusters (open access)

The Mean and Scatter of the Velocity Dispersion-Optical Richness Relation for MaxBCG Galaxy Clusters

The distribution of galaxies in position and velocity around the centers of galaxy clusters encodes important information about cluster mass and structure. Using the maxBCG galaxy cluster catalog identified from imaging data obtained in the Sloan Digital Sky Survey, we study the BCG--galaxy velocity correlation function. By modeling its non-Gaussianity, we measure the mean and scatter in velocity dispersion at fixed richness. The mean velocity dispersion increases from 202 {+-} 10 km s{sup -1} for small groups to more than 854 {+-} 102 km s{sup -1} for large clusters. We show the scatter to be at most 40.5{+-}3.5%, declining to 14.9{+-}9.4% in the richest bins. We test our methods in the C4 cluster catalog, a spectroscopic cluster catalog produced from the Sloan Digital Sky Survey DR2 spectroscopic sample, and in mock galaxy catalogs constructed from N-body simulations. Our methods are robust, measuring the scatter to well within one-sigma of the true value, and the mean to within 10%, in the mock catalogs. By convolving the scatter in velocity dispersion at fixed richness with the observed richness space density function, we measure the velocity dispersion function of the maxBCG galaxy clusters. Although velocity dispersion and richness do not form a true …
Date: June 5, 2007
Creator: Becker, M. R.; McKay, T. A.; Koester, B.; Wechsler, R. H.; Rozo, E.; Evrard, A. et al.
Object Type: Article
System: The UNT Digital Library
Simulation of Enhanced-Explosive Devices in Chambers and Tunnels (open access)

Simulation of Enhanced-Explosive Devices in Chambers and Tunnels

Introduction: Shock-dispersed fuel (SDF) explosives use a small chemical charge to disperse a combustible fuel that burns in the post-detonation environment. The energy released in the combustion process has the potential for generating higher pressures and temperatures than conventional explosives. However, the development of these types of novel explosive systems requires a detailed understanding of all of the modes of energy release. Objective: The objective of this project is develop a simulation capability for predicting explosion and combustion phase of SDF charges and apply that capability to quantifying the behavior of these types of explosives. Methodology: We approximate the dynamics of an SDF charge using high Reynolds number, fast chemistry model that effectively captures the thermodynamic behavior of SDF charges and accurately models the key modes of energy release. The overall computational model is combined with Adaptive Mesh Refinement (AMR) , implemented in a parallel adaptive framework suited to the massively parallel computer systems. Results: We have developed a multiphase version of the model and used it to simulate an SDF charge in which the dispersed fuel is aluminum flakes. Flow visualizations show that the combustion field is turbulent for the chamber and tunnel cases studied. During the 3 milli-seconds …
Date: June 5, 2007
Creator: Bell, J B; Kuhl, A L & Beckner, V E
Object Type: Article
System: The UNT Digital Library
Commissioning the SPEAR3 Diagnostic Beamlines (open access)

Commissioning the SPEAR3 Diagnostic Beamlines

SPEAR3 has two diagnostic beam lines: an x-ray pinhole camera and a visible/UV beam line. The pinhole camera images {approx}8 keV dipole synchrotron radiation (SR) incident on a phosphor screen. The visible beam line delivers conventional optical radiation to an array of cameras and diagnostic elements on a 1x3m optical bench. This paper briefly reviews the pinhole camera system while concentrating more on visible beam line power transmission calculations and streak camera data. Impedance estimates in the nominal optics and bunch length measurements in low-alpha optics are presented.
Date: June 5, 2007
Creator: Corbett, W. J.; Limborg-Deprey, C.; Mok, W. Y. & Ringwall, A.
Object Type: Article
System: The UNT Digital Library
Neutron Correlations in Special Nuclear Materials, Experiments and Simulations (open access)

Neutron Correlations in Special Nuclear Materials, Experiments and Simulations

Fissile materials emit neutrons with an unmistakable signature that can reveal characteristics of the material. We describe here measurements, simulations, and predicted signals expected and prospects for application of neutron correlation measurement methods to detection of special nuclear materials (SNM). The occurrence of fission chains in SNM can give rise to this distinctive, measurable time correlation signal. The neutron signals can be analyzed to detect the presence and to infer attributes of the SNM and surrounding materials. For instance, it is possible to infer attributes of an assembly containing a few kilograms of uranium, purely passively, using detectors of modest size in a reasonable time. Neutron signals of three radioactive sources are shown to illustrate the neutron correlation and analysis method. Measurements are compared with Monte Carlo calculations of the authenticated sources.
Date: June 5, 2007
Creator: Verbeke, J. M.; Dougan, A.; Nakae, L. F.; Sale, K. E. & Snyderman, N. J.
Object Type: Article
System: The UNT Digital Library