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Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider (open access)

Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider

None
Date: May 27, 2005
Creator: Pivi, M; Raubenheimer, T.; /SLAC; Ghalam, A.; U., /Southern California; Harkay, K. et al.
System: The UNT Digital Library
The Tachyon at the End of the Universe (open access)

The Tachyon at the End of the Universe

None
Date: June 27, 2005
Creator: McGreevy, John; Silverstein, Eva & /SLAC /Stanford U., Phys. Dept.
System: The UNT Digital Library
QLC relation and neutrino mass hierarchy (open access)

QLC relation and neutrino mass hierarchy

Latest measurements have revealed that the deviation from a maximal solar mixing angle is approximately the Cabibbo angle, i.e., QLC relation. We argue that it is not plausible that this deviation from maximality, be it a coincidence or not, comes from the charged lepton mixing. Consequently we have calculated the required corrections to the exactly bimaximal neutrino mass matrix ansatz necessary to account for the solar mass difference and the solar mixing angle. We point out that the relative size of these two corrections depends strongly on the hierarchy case under consideration. We find that the inverted hierarchy case with opposite CP parities, which is known to guarantee the RGE stability of the solar mixing angle, offers the most plausible scenario for a high energy origin of a QLC-corrected bimaximal neutrino mass matrix. This possibility may allow us to explain the QLC relation in connection with the origin of the charged fermion mass matrices.
Date: January 27, 2005
Creator: Ferrandis, Javier & Pakvasa, Sandip
System: The UNT Digital Library
The Roles of Sparse Direct Methods in Large-scale Simulations (open access)

The Roles of Sparse Direct Methods in Large-scale Simulations

Sparse systems of linear equations and eigen-equations arise at the heart of many large-scale, vital simulations in DOE. Examples include the Accelerator Science and Technology SciDAC (Omega3P code, electromagnetic problem), the Center for Extended Magnetohydrodynamic Modeling SciDAC(NIMROD and M3D-C1 codes, fusion plasma simulation). The Terascale Optimal PDE Simulations (TOPS)is providing high-performance sparse direct solvers, which have had significant impacts on these applications. Over the past several years, we have been working closely with the other SciDAC teams to solve their large, sparse matrix problems arising from discretization of the partial differential equations. Most of these systems are very ill-conditioned, resulting in extremely poor convergence deployed our direct methods techniques in these applications, which achieved significant scientific results as well as performance gains. These successes were made possible through the SciDAC model of computer scientists and application scientists working together to take full advantage of terascale computing systems and new algorithms research.
Date: June 27, 2005
Creator: Li, Xiaoye S.; Gao, Weiguo; Husbands, Parry J. R.; Yang, Chao & Ng, Esmond G.
System: The UNT Digital Library
High Temperature Strain Gages for SOFC Application (open access)

High Temperature Strain Gages for SOFC Application

This presentation discusses the investigation/extension of high temperature strain gage applications sensors to SOFC applications.
Date: January 27, 2005
Creator: Pineault, R. L.; Johnson, C.; Gemmen, R. S.; Gregory, O. & You, T.
System: The UNT Digital Library
The Modular Point Design for Heavy Ion Fusion (open access)

The Modular Point Design for Heavy Ion Fusion

We report on an ongoing study on modular Heavy Ion Fusion drivers. The modular driver is characterized by tens ({approx} 20) nearly identical induction linacs, each carrying a single high current beam. In this scheme, the Integrated Research Experiment (IRE) can be one of the full size induction linacs. Hence, this approach offers significant advantages in terms of driver development path. For beam transport, these modules use solenoids which are capable of carrying high line charge densities, even at low energies. A new injector concept allows compression of the beam to high line densities right at the source. The final drift compression is performed in a plasma, in which the large repulsive space charge effects are neutralized. Finally, the beam is transversely compressed onto the target, using either external solenoids or current-carrying channels (in the Assisted Pinch Mode of beam propagation). We will report on progress towards a self-consistent point design from injector to target. Considerations of driver architecture, chamber environment as well as the methodology for meeting target requirements of spot size, pulse shape and symmetry will also be described. Finally, some near-term experiments to address the key scientific issues will be discussed.
Date: January 27, 2005
Creator: Yu, S. S.; Barnard, J. J.; Briggs, R. J.; Callahan-Miller, D.; Celata, C. M.; Chao, L. et al.
System: The UNT Digital Library
CP VIOLATION HIGHLIGHTS: CIRCA 2005 (open access)

CP VIOLATION HIGHLIGHTS: CIRCA 2005

Recent highlights in CP violation phenomena, are reviewed. B-factory results imply that, CP-violation phase in the CKM matrix is the dominant contributor to the observed CP violation in K and B-physics. Deviations from the predictions of the CKM-paradigm due to beyond the Standard Model CP-odd phase are likely to be a small perturbation. Therefore, large data sample of clean B's will be needed. Precise determination of the unitarity triangle, along with time dependent CP in penguin dominated hadronic and radiative modes are discussed. Null tests in B, K and top-physics and separate determination of the K-unitarity triangle are also emphasized.
Date: February 27, 2005
Creator: A., SONI
System: The UNT Digital Library
Identifying the Basal Angiosperm Node in Chloroplast GenomePhylogenies: Sampling One's Way Out of the Felsenstein Zone (open access)

Identifying the Basal Angiosperm Node in Chloroplast GenomePhylogenies: Sampling One's Way Out of the Felsenstein Zone

While there has been strong support for Amborella and Nymphaeales (water lilies) as branching from basal-most nodes in the angiosperm phylogeny, this hypothesis has recently been challenged by phylogenetic analyses of 61 protein-coding genes extracted from the chloroplast genome sequences of Amborella, Nymphaea and 12 other available land plant chloroplast genomes. These character-rich analyses placed the monocots, represented by three grasses (Poaceae), as sister to all other extant angiosperm lineages. We have extracted protein-coding regions from draft sequences for six additional chloroplast genomes to test whether this surprising result could be an artifact of long-branch attraction due to limited taxon sampling. The added taxa include three monocots (Acorus, Yucca and Typha), a water lily (Nuphar), a ranunculid(Ranunculus), and a gymnosperm (Ginkgo). Phylogenetic analyses of the expanded DNA and protein datasets together with microstructural characters (indels) provided unambiguous support for Amborella and the Nymphaeales as branching from the basal-most nodes in the angiospermphylogeny. However, their relative positions proved to be dependent on method of analysis, with parsimony favoring Amborella as sister to all other angiosperms, and maximum likelihood and neighbor-joining methods favoring an Amborella + Nympheales clade as sister. The maximum likelihood phylogeny supported the later hypothesis, but the likelihood for …
Date: May 27, 2005
Creator: Leebens-Mack, Jim; Raubeson, Linda A.; Cui, Liying; Kuehl,Jennifer V.; Fourcade, Matthew H.; Chumley, Timothy W. et al.
System: The UNT Digital Library
Transport & Disposal of TPBARs at the Tritium Extraction Facility (open access)

Transport & Disposal of TPBARs at the Tritium Extraction Facility

As a part of the Department of Energy Tritium Readiness Program, the Tritium Extraction Facility (TEF) at the Savannah River Site (SRS) is preparing to receive the first shipment of irradiated Tritium Producing Burnable Absorber Rods (TPBARs) from the Tennessee Valley Authority's Watts Bar Nuclear Plant. Tritium will be extracted from the TPBARs at the TEF. The spent TPBARs will be transported and disposed on site using the TEF Waste Container, designed and fabricated by Packaging Technology, Inc. This paper describes the TPBAR waste form, the TEF Waste Container to be used to store the waste, the operational sequence associated with management of the TBPAR waste form and the disposal facility at the SRS.
Date: January 27, 2005
Creator: BENJAMIN, SNIDER
System: The UNT Digital Library
Evidence of vectorial photoelectric effect on copper (open access)

Evidence of vectorial photoelectric effect on copper

Quantum Efficiency (QE) measurements of single photon photoemission from a Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150 fs-6.28 eV laser pulses, are reported over a broad range of incidence angle, both in s and p polarizations. The maximum QE (approx. = 4x10-4) for polycrystalline Cu is obtained in p polarization at an angle of incidence theta = 65 deg. We observe a QE enhancement in p polarization which can not be explained in terms of optical absorption, a phenomenon known as vectorial photoelectric effect. Issues concerning surface roughness and symmetry considerations are addressed. An explanation in terms of non local conductivity tensor is proposed.
Date: May 27, 2005
Creator: Pedersoli, E.; Banfi, F.; Ressel, B.; Pagliara, S.; Giannetti,C.; Galimberti, G. et al.
System: The UNT Digital Library
Neutron Capture and Total Cross Section Measurements and Resonance parameters of Gadolinium (open access)

Neutron Capture and Total Cross Section Measurements and Resonance parameters of Gadolinium

None
Date: June 27, 2005
Creator: Leinweber, G.; Barry, D. P.; Trbovich, M. J.; Burke, J. A.; Drindak, N. J.; Knox, H. D. et al.
System: The UNT Digital Library
A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting. (open access)

A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting.

Solidification of dendritic alloys is modeled using stabilized finite element techniques to study convection and macrosegregation driven by buoyancy and shrinkage. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume-averaging method. A single domain model is considered with a fixed numerical grid and without boundary conditions applied explicitly on the freezing front. The mushy zone is modeled here as a porous medium with either an isotropic or an anisotropic permeability. The stabilized finite-element scheme, previously developed by authors for modeling flows with phase change, is extended here to include effects of shrinkage, density changes and anisotropic permeability during solidification. The fluid flow scheme developed includes streamline-upwind/Petrov-Galerkin (SUPG), pressure stabilizing/Petrov-Galerkin, Darcy stabilizing/Petrov-Galerkin and other stabilizing terms arising from changes in density in the mushy zone. For the energy and species equations a classical SUPG-based finite element method is employed with minor modifications. The developed algorithms are first tested for a reference problem involving solidification of lead-tin alloy where the mushy zone is characterized by an isotropic permeability. Convergence studies are performed to validate the simulation results. Solidification of the same alloy in the absence of shrinkage is studied to …
Date: April 27, 2005
Creator: Dr. Zabaras, N. & Samanta, D.
System: The UNT Digital Library
Engineering Monosodium Titanate for Adsorption Column Processes (open access)

Engineering Monosodium Titanate for Adsorption Column Processes

Monosodium titanate is an inorganic adsorbent powder that effectively removes strontium, plutonium, neptunium, and other trace elements from alkaline high-level waste supernate. This work tested one commercial titanate and four general methods to engineer MST into particles large enough to use in adsorption columns. The most successful of the engineered products selected from batch contact and chemical stability testing succeeded in treating 2900 bed volumes of simulated salt waste containing dissolved plutonium and strontium. There was no detectable strontium breakthrough and only 6 percent plutonium breakthrough--well within the processing goal--at the end of the demonstration which operated at 5.3 BV/hour. Additional column tests at nominally 15 BV/hr demonstrated similar removal performance. Batch testing of adsorbents used both actual Savannah River Site tank supernate as well as simulated salt solutions spiked with strontium, neptunium, and plutonium. In tank waste tests, internal gelation beads produced by the Oak Ridge National Laboratory demonstrated a batch distribution coefficient of 35,000 +/- 4,000 mL/g for plutonium at a phase ratio of 1970 mL/g. In the same batch the sorbent demonstrated a batch distribution coefficient of 99,000 +/- 7,500 mL/g for strontium. These results indicate that this material should be able to process thousands of bed …
Date: February 27, 2005
Creator: CHARLES, NASH
System: The UNT Digital Library
Structural properties of free-standing 50 mm diameter GaN waferswith (101_0) orientation grown on LiAlO2 (open access)

Structural properties of free-standing 50 mm diameter GaN waferswith (101_0) orientation grown on LiAlO2

(10{und 1}0) GaN wafers grown on (100) face of {gamma}-LiAlO{sub 2} were studied using transmission electron microscopy. Despite good lattice matching in this heteroepitaxial system, high densities of planar structural defects in the form of stacking faults on the basal plane and networks of boundaries located on prism planes inclined to the layer/substrate interface were present in these GaN layers. In addition, significant numbers of threading dislocations were observed. High-resolution electron microscopy indicates that stacking faults present on the basal plane in these layers are of low-energy intrinsic I1type. This is consistent with diffraction contrast experiments.
Date: September 27, 2005
Creator: Jasinski, Jacek; Liliental-Weber, Zuzanna; Maruska, Herbert-Paul; Chai, Bruce H.; Hill, David W.; Chou, Mitch M.C. et al.
System: The UNT Digital Library
DIFFRACTION DISSOCIATION - 50 YEARS LATER. (open access)

DIFFRACTION DISSOCIATION - 50 YEARS LATER.

The field of Diffraction Dissociation, which is the subject of this workshop, began 50 years ago with the analysis of deuteron stripping in low energy collisions with nuclei. We return to the subject in a modern context- deuteron dissociation in {radical}s{sub NN} = 200 GeV d-Au collisions recorded during the 2003 RHIC run in the PHENIX experiment. At RHIC energy, d {yields} n+p proceeds predominantly (90%) through Electromagnetic Dissociation and the remaining fraction via the hadronic shadowing described by Glauber. Since the dissociation cross section has a small theoretical error we adopt this process to normalize other cross sections measured in RHIC.
Date: April 27, 2005
Creator: White, Sebastian N.
System: The UNT Digital Library
NEXT-TO-LEADING ORDER ZCD CORRECTOINS TO ATT FOR SINGLE-INCLUSIVE HADRON PRODUCTION. (open access)

NEXT-TO-LEADING ORDER ZCD CORRECTOINS TO ATT FOR SINGLE-INCLUSIVE HADRON PRODUCTION.

We report on a calculation of the next-to-leading order QCD corrections to the partonic cross sections contributing to single-inclusive high-p{sub T} hadron production in collisions of transversely polarized hadrons. We give some predictions for the double spin asymmetry A{sub TT}{sup {pi}} for the proposed experiments at RHIC and at the GSI.
Date: April 27, 2005
Creator: MUKHERJEE, A.; STRATMANN, M. & VOGELSANG, W.
System: The UNT Digital Library
Material Interface Reconstruction in VisIt (open access)

Material Interface Reconstruction in VisIt

In this paper, we first survey a variety of approaches to material interface reconstruction and their applicability to visualization, and we investigate the details of the current reconstruction algorithm in the VisIt scientific analysis and visualization tool. We then provide a novel implementation of the original VisIt algorithm that makes use of a wide range of the finite element zoo during reconstruction. This approach results in dramatic improvements in quality and performance without sacrificing the strengths of the VisIt algorithm as it relates to visualization.
Date: January 27, 2005
Creator: Meredith, J S
System: The UNT Digital Library
Development of Chaos in the Color Glass Condensate. (open access)

Development of Chaos in the Color Glass Condensate.

Noting that the number of gluons in the hadron wave function is discrete, and their formation in the chain of small x evolution occurs over discrete rapidity intervals of {Delta}y {approx} 1/{alpha}{sub s}, we formulate the discrete version of the Balitsky-Kovchegov evolution equation and show that its solution behaves chaotically in the phenomenologically interesting kinematic region.
Date: April 27, 2005
Creator: Tuchin, K.
System: The UNT Digital Library
The Dissociation Enthalpies of Terminal (N--O) Bonds in Organic Compounds (open access)

The Dissociation Enthalpies of Terminal (N--O) Bonds in Organic Compounds

Article on the dissociation enthalpies of terminal (N-O) bonds in organic compounds.
Date: May 27, 2005
Creator: Acree, William E. (William Eugene); Pilcher, Geoffrey & Silva, Maria D. M. C. Ribeiro da
System: The UNT Digital Library
Evidence for the Net Addition of Arene C-H Bonds across a Ru(II)-Hydroxide Bond (open access)

Evidence for the Net Addition of Arene C-H Bonds across a Ru(II)-Hydroxide Bond

Article discussing evidence for the net addition of Arene C-H bonds across a Ru(II)-Hydroxide bond.
Date: September 27, 2005
Creator: Feng, Yuee; Lail, Marty; Barakat, Khaldoon A.; Cundari, Thomas R., 1964-; Gunnoe, T. Brent & Petersen, Jeffrey L.
System: The UNT Digital Library
The 2mrad horizontal crossing angle IR layout for a TeV ILC (open access)

The 2mrad horizontal crossing angle IR layout for a TeV ILC

The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.
Date: July 27, 2005
Creator: Appleby, R.; Angal-Kalinin, D.; /Daresbury; Bambade, P.; Mouton, B.; /Orsay, LAL et al.
System: The UNT Digital Library
Tiling Models for Spatial Decomposition in AMTRAN (open access)

Tiling Models for Spatial Decomposition in AMTRAN

Effective spatial domain decomposition for discrete ordinate (S{sub n}) neutron transport calculations has been critical for exploiting massively parallel architectures typified by the ASCI White computer at Lawrence Livermore National Laboratory. A combination of geometrical and computational constraints has posed a unique challenge as problems have been scaled up to several thousand processors. Carefully scripted decomposition and corresponding execution algorithms have been developed to handle a range of geometrical and hardware configurations.
Date: May 27, 2005
Creator: Compton, J. C. & Clouse, C. J.
System: The UNT Digital Library
Extracting Critical Path Graphs from MPI Applications (open access)

Extracting Critical Path Graphs from MPI Applications

The critical path is one of the fundamental runtime characteristics of a parallel program. It identifies the longest execution sequence without wait delays. In other words, the critical path is the global execution path that inflicts wait operations on other nodes without itself being stalled. Hence, it dictates the overall runtime and knowing it is important to understand an application's runtime and message behavior and to target optimizations. We have developed a toolset that identifies the critical path of MPI applications, extracts it, and then produces a graphical representation of the corresponding program execution graph to visualize it. To implement this, we intercept all MPI library calls, use the information to build the relevant subset of the execution graph, and then extract the critical path from there. We have applied our technique to several scientific benchmarks and successfully produced critical path diagrams for applications running on up to 128 processors.
Date: July 27, 2005
Creator: Schulz, M
System: The UNT Digital Library
High Energy Density Physics and Exotic Acceleration Schemes (open access)

High Energy Density Physics and Exotic Acceleration Schemes

The High Energy Density and Exotic Acceleration working group took as our goal to reach beyond the community of plasma accelerator research with its applications to high energy physics, to promote exchange with other disciplines which are challenged by related and demanding beam physics issues. The scope of the group was to cover particle acceleration and beam transport that, unlike other groups at AAC, are not mediated by plasmas or by electromagnetic structures. At this Workshop, we saw an impressive advancement from years past in the area of Vacuum Acceleration, for example with the LEAP experiment at Stanford. And we saw an influx of exciting new beam physics topics involving particle propagation inside of solid-density plasmas or at extremely high charge density, particularly in the areas of laser acceleration of ions, and extreme beams for fusion energy research, including Heavy-ion Inertial Fusion beam physics. One example of the importance and extreme nature of beam physics in HED research is the requirement in the Fast Ignitor scheme of inertial fusion to heat a compressed DT fusion pellet to keV temperatures by injection of laser-driven electron or ion beams of giga-Amp current. Even in modest experiments presently being performed on the laser-acceleration …
Date: September 27, 2005
Creator: Cowan, T.; /General Atomics, San Diego & Colby, E.
System: The UNT Digital Library