Argonne's Laboratory Computing Center - 2007 Annual Report. (open access)

Argonne's Laboratory Computing Center - 2007 Annual Report.

Argonne National Laboratory founded the Laboratory Computing Resource Center (LCRC) in the spring of 2002 to help meet pressing program needs for computational modeling, simulation, and analysis. The guiding mission is to provide critical computing resources that accelerate the development of high-performance computing expertise, applications, and computations to meet the Laboratory's challenging science and engineering missions. In September 2002 the LCRC deployed a 350-node computing cluster from Linux NetworX to address Laboratory needs for mid-range supercomputing. This cluster, named 'Jazz', achieved over a teraflop of computing power (1012 floating-point calculations per second) on standard tests, making it the Laboratory's first terascale computing system and one of the 50 fastest computers in the world at the time. Jazz was made available to early users in November 2002 while the system was undergoing development and configuration. In April 2003, Jazz was officially made available for production operation. Since then, the Jazz user community has grown steadily. By the end of fiscal year 2007, there were over 60 active projects representing a wide cross-section of Laboratory expertise, including work in biosciences, chemistry, climate, computer science, engineering applications, environmental science, geoscience, information science, materials science, mathematics, nanoscience, nuclear engineering, and physics. Most important, many …
Date: May 28, 2008
Creator: Bair, R. & Pieper, G. W.
Object Type: Report
System: The UNT Digital Library
Investigations of Solar Prominence Dynamics Using Laboratory Simulations (open access)

Investigations of Solar Prominence Dynamics Using Laboratory Simulations

Laboratory experiments simulating many of the dynamical features of solar coronal loops have been carried out. These experiments manifest collimation, kinking, jet flows, and S-shapes. Diagnostics include high-speed photography and x-ray detectors. Two loops having opposite or the same magnetic helicity polarities have been merged and it is found that counter-helicity merging provides much greater x-ray emission. A non-MHD particle orbit instability has been discovered whereby ions going in the opposite direction of the current flow direction can be ejected from a magnetic flux tube.
Date: May 28, 2008
Creator: Bellan, Paul M
Object Type: Report
System: The UNT Digital Library
Factorization and resummation for collinear poles in QCD amplitudes (open access)

Factorization and resummation for collinear poles in QCD amplitudes

We study the origin of subleading soft and collinear poles of form factors and amplitudes in dimensionally-regulated massless gauge theories. In the case of form factors of fundamental fields, these poles originate from a single function of the coupling, denoted G({alpha}{sub s}), depending on both the spin and gauge quantum numbers of the field. We relate G({alpha}{sub s}) to gauge-theory matrix elements involving the gluon field strength. We then show that G({alpha}{sub s}) is the sum of three terms: a universal eikonal anomalous dimension, a universal non-eikonal contribution, given by the coefficient B{sub {delta}}({alpha}{sub s}) of {delta}(1-z) in the collinear evolution kernel, and a process-dependent short-distance coefficient function, which does not contribute to infrared poles. Using general results on the factorization of soft and collinear singularities in fixed-angle massless gauge theory amplitudes, we conclude that all such singularities are captured by the eikonal approximation, supplemented only by the knowledge of B{sub {delta}}({alpha}{sub s}). We explore the consequences of our results for conformal gauge theories, where in particular we find a simple exact relation between the form factor and the cusp anomalous dimension.
Date: May 28, 2008
Creator: Dixon, Lance J.; Magnea, Lorenzo & Sterman, George
Object Type: Article
System: The UNT Digital Library
Development of Materials Resistant to Metal Dusting Degradation-Vol 1 (open access)

Development of Materials Resistant to Metal Dusting Degradation-Vol 1

This is Volume 1 of a two-volume report. It provides general information on industrial participation and commercialization. Volume 2 contains details of technical work and results.
Date: May 28, 2008
Creator: Ford, Emory A
Object Type: Report
System: The UNT Digital Library
SUSY at the ILC and Solving the LHC Inverse Problem (open access)

SUSY at the ILC and Solving the LHC Inverse Problem

Recently a large scale study of points in the MSSM parameter space which are problematic at the Large Hadron Collider (LHC) has been performed. This work was carried out in part to determine whether the proposed International Linear Collider (ILC) could be used to solve the LHC inverse problem. The results suggest that while the ILC will be a valuable tool, an energy upgrade may be crucial to its success, and that, in general, precision studies of the MSSM are more difficult at the ILC than has generally been believed.
Date: May 28, 2008
Creator: Gainer, James S.
Object Type: Article
System: The UNT Digital Library
Gas Mixing Analysis in a Large-Scaled Saltstone Facility (open access)

Gas Mixing Analysis in a Large-Scaled Saltstone Facility

Computational fluid dynamics (CFD) methods have been used to estimate the flow patterns mainly driven by temperature gradients inside vapor space in a large-scaled Saltstone vault facility at Savannah River site (SRS). The purpose of this work is to examine the gas motions inside the vapor space under the current vault configurations by taking a three-dimensional transient momentum-energy coupled approach for the vapor space domain of the vault. The modeling calculations were based on prototypic vault geometry and expected normal operating conditions as defined by Waste Solidification Engineering. The modeling analysis was focused on the air flow patterns near the ventilated corner zones of the vapor space inside the Saltstone vault. The turbulence behavior and natural convection mechanism used in the present model were benchmarked against the literature information and theoretical results. The verified model was applied to the Saltstone vault geometry for the transient assessment of the air flow patterns inside the vapor space of the vault region using the potential operating conditions. The baseline model considered two cases for the estimations of the flow patterns within the vapor space. One is the reference nominal case. The other is for the negative temperature gradient between the roof inner and …
Date: May 28, 2008
Creator: Lee, S.
Object Type: Article
System: The UNT Digital Library
Photoemission Study of Cs-NF3 Activated GaAs(100) Negative Electron Affinity Photocathodes (open access)

Photoemission Study of Cs-NF3 Activated GaAs(100) Negative Electron Affinity Photocathodes

GaAs based negative electron affinity photocathodes activated with Cs and NF{sub 3} are used as polarized electron sources for linear accelerators. It is generally believed that the activation layer consists of CsF. The activation layers of Cs-NF{sub 3} on GaAs photocathodes are herein investigated using synchrotron radiation photoelectron spectroscopy (SR-PES). F1s, N1s and other core levels are recorded at photon energies ranging from 70eV to 820eV. Surprisingly, a significant amount of nitrogen is observed in the activation layers. Two distinct species of nitrogen are observed, one of which decreases along with the Fluorine signal as the yield of the photocathode decays with time.
Date: May 28, 2008
Creator: Liu, Z.; Sun, Y.; Peterson, S. & Pianetta, P.
Object Type: Article
System: The UNT Digital Library
Development of Materials Resistant to Metal Dusting Degradation-Vol 2 (open access)

Development of Materials Resistant to Metal Dusting Degradation-Vol 2

This is volume 2 of a two-volume report on the project. Volume 1 provides general information about industry participation and commercialization plan. This volume provides details of technical work and results.
Date: May 28, 2008
Creator: Natesan, Ken
Object Type: Report
System: The UNT Digital Library
Final Report for "Gyrotron Design and Evaluation using New Particle-in-Cell Capability" (open access)

Final Report for "Gyrotron Design and Evaluation using New Particle-in-Cell Capability"

ITER will depend on high power CW gyrotrons to deliver power to the plasma at ECR frequencies. However, gyrotrons can suffer from undesirable low frequency oscillations (LFO’s) which are known to interfere with the gun-region diagnostics and data collection, and are also expected to produce undesirable energy and velocity spread in the beam. The origins and processes leading to these oscillations are poorly understood, and existing gyrotron R&D tools, such as static gun solvers and interaction region models, are not designed to look at time-dependant oscillatory behavior. We have applied a time-domain particle-in-cell method to investigate the LFO phenomenon. Our company is at the forefront of smooth-curved-boundary treatment of the electromagnetic fields and particle emission surfaces, and such methods are necessary to simulate the adiabatically trapped and reflected electrons thought to be driving the oscillations. This approach provides the means for understanding, in microscopic detail, the underlying physical processes driving the low-frequency oscillations. In the Phase I project, an electron gun region from an existing gyrotron, known to observe LFO’s, was selected as a proof-of-principle geometry, and was modeled with the curved-geometry time-domain simulation tool, in order to establish the feasibility of simulating LFO physics with this tool on office-scale, …
Date: May 28, 2008
Creator: Smithe, David N
Object Type: Report
System: The UNT Digital Library
Back-Up/ Peak Shaving Fuel Cell System (open access)

Back-Up/ Peak Shaving Fuel Cell System

This Final Report covers the work executed by Plug Power from 8/11/03 – 10/31/07 statement of work for Topic 2: advancing the state of the art of fuel cell technology with the development of a new generation of commercially viable, stationary, Back-up/Peak-Shaving fuel cell systems, the GenCore II. The Program cost was $7.2 M with the Department of Energy share being $3.6M and Plug Power’s share being $3.6 M. The Program started in August of 2003 and was scheduled to end in January of 2006. The actual program end date was October of 2007. A no cost extension was grated. The Department of Energy barriers addressed as part of this program are: Technical Barriers for Distributed Generation Systems: o Durability o Power Electronics o Start up time Technical Barriers for Fuel Cell Components: o Stack Material and Manufacturing Cost o Durability o Thermal and water management Background The next generation GenCore backup fuel cell system to be designed, developed and tested by Plug Power under the program is the first, mass-manufacturable design implementation of Plug Power’s GenCore architected platform targeted for battery and small generator replacement applications in the telecommunications, broadband and UPS markets. The next generation GenCore will be …
Date: May 28, 2008
Creator: Staudt, Rhonda L.
Object Type: Report
System: The UNT Digital Library
Distortion of Crabbed Bunch Due to the Electron Cloud (open access)

Distortion of Crabbed Bunch Due to the Electron Cloud

In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This note briefly estimates the bunch shape distortion due to the electron cloud in KEKB LER.
Date: May 28, 2008
Creator: Wang, L. & Raubenheimer, T.
Object Type: Report
System: The UNT Digital Library