Resource Type

Month

Complex potential surface for the {sup 2}B{sub 1} metastable state of the water anion (open access)

Complex potential surface for the {sup 2}B{sub 1} metastable state of the water anion

The potential energy surface corresponding the complex resonance energy of the 2B1 Feshbach resonance state of the water anion is constructed in its full dimensionality. Complex Kohn variational scattering calculations are used to compute the resonance width, while large-scale Configuration Interaction calculations are used to compute the resonance energy. Near the equilibrium geometry, an accompanying ground state potential surface is constructed from Configuration Interaction calculations that treat correlation at a level similar to that used in the calculations on the anion.
Date: April 23, 2004
Creator: Haxton, Daniel J.; Zhang, Zhiyong; McCurdy, C. William & Rescigno, Thomas N.
System: The UNT Digital Library
A step towards a computing grid for the LHC experiments: ATLAS Data Challenge 1 (open access)

A step towards a computing grid for the LHC experiments: ATLAS Data Challenge 1

The ATLAS Collaboration at CERN is preparing for the data taking and analysis at the LHC that will start in 2007. Therefore, a series of Data Challenges was started in 2002 whose goals are the validation of the Computing Model, of the complete software suite, of the data model, and to ensure the correctness of the technical choices to be made. A major feature of the first Data Challenge was the preparation and the deployment of the software required for the production of large event samples as a worldwide-distributed activity. It should be noted that it was not an option to ''run everything at CERN'' even if we had wanted to; the resources were not available at CERN to carry out the production on a reasonable time-scale. The great challenge of organizing and then carrying out this large-scale production at a significant number of sites around the world had the refore to be faced. However, the benefits of this are manifold: apart from realizing the required computing resources, this exercise created worldwide momentum for ATLAS computing as a whole. This report describes in detail the main steps carried out in DC1 and what has been learned from them as a …
Date: April 23, 2004
Creator: Sturrock, R.; Bischof, R.; Epp, B.; Ghete, V. M.; Kuhn, D.; Mello, A. G. et al.
System: The UNT Digital Library
Could There Be a Hole in Type Ia Supernovae? (open access)

Could There Be a Hole in Type Ia Supernovae?

In the favored progenitor scenario, Type Ia supernovae (SNe Ia) arise from a white dwarf accreting material from a non-degenerate companion star. Soon after the white dwarf explodes, the ejected supernova material engulfs the companion star; two-dimensional hydrodynamical simulations by Marietta et al. (2001) show that, in the interaction, the companion star carves out a conical hole of opening angle 30-40 degrees in the supernova ejecta. In this paper we use multi-dimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry. We calculate the variation of the spectrum, luminosity, and polarization with viewing angle for the aspherical supernova near maximum light. We find that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole. In the latter case, one sees into the deeper, hotter layers of ejecta. The supernova is relatively brighter and has a peculiar spectrum characterized by more highly ionized species, weaker absorption features, and lower absorption velocities. The spectrum viewed down the hole is comparable to the class of SN 1991T-like supernovae. We consider how the ejecta-hole asymmetry may explain the current spectropolarimetric observations of SNe Ia, and suggest a few observational signatures of …
Date: April 23, 2004
Creator: Kasen, Daniel; Nugent, Peter; Thomas, R. C. & Wang, Lifan
System: The UNT Digital Library
Dynamics of dissociative attachment of electrons to water through the {sup 2}B{sub 1} metastable state of the anion (open access)

Dynamics of dissociative attachment of electrons to water through the {sup 2}B{sub 1} metastable state of the anion

None
Date: April 23, 2004
Creator: Haxton, Daniel A.; Zhang, Zhiyong; Meyer, Hans-Dieter; Rescigno, Thomas N. & McCurdy, C. William
System: The UNT Digital Library
Laboratory design for high-performance electron microscopy (open access)

Laboratory design for high-performance electron microscopy

Proliferation of electron microscopes with field emission guns, imaging filters and hardware spherical aberration correctors (giving higher spatial and energy resolution) has resulted in the need to construct special laboratories. As resolutions improve, transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) become more sensitive to ambient conditions. State-of-the-art electron microscopes require state-of-the-art environments, and this means careful design and implementation of microscope sites, from the microscope room to the building that surrounds it. Laboratories have been constructed to house high-sensitive instruments with resolutions ranging down to sub-Angstrom levels; we present the various design philosophies used for some of these laboratories and our experiences with them. Four facilities are described: the National Center for Electron Microscopy OAM Laboratory at LBNL; the FEGTEM Facility at the University of Sheffield; the Center for Integrative Molecular Biosciences at TSRI; and the Advanced Microscopy Laboratory at ORNL.
Date: April 23, 2004
Creator: O'Keefe, Michael A.; Turner, John H.; Hetherington, Crispin J. D.; Cullis, A. G.; Carragher, Bridget; Jenkins, Ron et al.
System: The UNT Digital Library
ALS control system IP I/O module upgrade (open access)

ALS control system IP I/O module upgrade

The Control System for the Advanced Light Source uses in-house designed IndustryPack (IP) I/O Modules in compact PCI (cPCI) chassis to control instrumentation. Each module consists of digital I/O ports and 16-bit analog I/O interfaced to instrumentation via a cPCI rear I/O card. During the past few years of installed operation, several factors have prompted investigation into the design of a new IP I/O Module. The ADC channels have significant offset drift over periods of days of initial installed operation. An in-situ calibration procedure was developed to address this problem, but it lacks speed and is inconvenient to perform. Digital I/O port limitations have led to increasing amounts of wasted I/O. Fast orbit feedback requires faster ADC sampling and better filtering than the current IP module offers. This paper discusses the issues related to the current IP I/O Module and the design of a new Double-size IP I/O Module.
Date: April 23, 2004
Creator: Weber, Jonah M. & Chin, Michael
System: The UNT Digital Library
Drop Test Results for the Combustion Engineering Model No. ABB-2901 Fuel Pellet Package (open access)

Drop Test Results for the Combustion Engineering Model No. ABB-2901 Fuel Pellet Package

The U.S. Nuclear Regulatory Commission (USNRC) contracted with the Packaging Review Group (PRG) at Lawrence Livermore National Laboratory (LLNL) to conduct a single, 30-ft shallow-angle drop test on the Combustion Engineering ABB-2901 drum-type shipping package. The purpose of the test was to determine if bolted-ring drum closures could fail during shallow-angle drops. The PRG at LLNL planned the test, and Defense Technologies Engineering Division (DTED) personnel from LLNL's Site-300 Test Group executed the plan. The test was conducted in November 2001 using the drop-tower facility at LLNL's Site 300. Two representatives from Westinghouse Electric Company in Columbia, South Carolina (WEC-SC); two USNRC staff members; and three PRG members from LLNL witnessed the preliminary test runs and the final test. The single test clearly demonstrated the vulnerability of the bolted-ring drum closure to shallow-angle drops-the test package's drum closure was easily and totally separated from the drum package. The results of the preliminary test runs and the 30-ft shallow-angle drop test offer valuable qualitative understandings of the shallow-angle impact.
Date: April 23, 2004
Creator: Hafner, R S; Mok, G C & Hagler, L G
System: The UNT Digital Library
Hydrogen Technology Development and Demonstration at the Savannah River Technology Center (open access)

Hydrogen Technology Development and Demonstration at the Savannah River Technology Center

The Savannah River Technical Center (SRTC) has been active in teaming with academic and industrial partners to advance hydrogen technology. A primary focus of SRTC's R and D has been hydrogen storage using metal and complex hydrides. SRTC and its Hydrogen Technology Laboratory (HyTech) have been very successful in leveraging their defense infrastructure, capabilities and investments to help solve this country's energy problems. Many of HyTech's programs support dual-use applications. HyTech has participated in projects to convert public transit and utility vehicles for operation on hydrogen fuel. Two major projects include the H2Fuel Bus and an Industrial Fuel Cell Vehicle (IFCV) also known as the GATORTM. Both of these projects were funded by DOE and cost shared by industry.
Date: April 23, 2004
Creator: Danko, E. T.
System: The UNT Digital Library