Language

Performance of the Anti-Coincidence Detector on the GLAST Large Area Telescope (open access)

Performance of the Anti-Coincidence Detector on the GLAST Large Area Telescope

The Anti-Coincidence Detector (ACD), the outermost detector layer in the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT), is designed to detect and veto incident cosmic ray charged particles, which outnumber cosmic gamma rays by 3-4 orders of magnitude. The challenge in ACD design is that it must have high (0.9997) detection efficiency for singly-charged relativistic particles, but must also have a low probability for self-veto of high-energy gammas by backsplash radiation from interactions in the LAT calorimeter. Simulations and tests demonstrate that the ACD meets its design requirements. The performance of the ACD has remained stable through stand-alone environmental testing, shipment across the U.S., installation onto the LAT, shipment back across the U.S., LAT environmental testing, and shipment to Arizona. As part of the fully-assembled GLAST observatory, the ACD is being readied for final testing before launch.
Date: October 22, 2007
Creator: Thompson, D. J.; Charles, E.; Hartman, R. C.; Moiseev, A. A. & Ormes, J. F.
Object Type: Article
System: The UNT Digital Library
GRB Simulations in GLAST (open access)

GRB Simulations in GLAST

The Gamma-ray Large Area Space Telescope (GLAST), scheduled to be launched in fall of 2007, is the next generation satellite for high-energy gamma-ray astronomy. The Large Area Telescope (LAT) is a pair conversion telescope built with a high precision silicon tracker, a segmented CsI electromagnetic calorimeter and a plastic anticoincidence shield. The LAT will survey the sky in the energy range between 20 MeV to more than 300 GeV, shedding light on many issues left open by its highly successful predecessor EGRET. LAT will observe Gamma-Ray Bursts (GRB) in an energy range never explored before; to tie these frontier observations to the better-known properties at lower energies, a second instrument, the GLAST Burst Monitor (GBM) will provide important spectra and timing in the 10 keV to 30 MeV range. We briefly present the instruments onboard the GLAST satellite, their synergy in the GRB observations and the work done so far by the collaboration in simulation, analysis, and GRB sensitivity estimation.
Date: October 22, 2007
Creator: Omodei, Nicola; /INFN, Pisa; Battelino, Milan; Observ., /Stockholm; Komin, Nukri; U., /Montpellier et al.
Object Type: Article
System: The UNT Digital Library
Exploring the Polarization of Gluons in the Nucleon. (open access)

Exploring the Polarization of Gluons in the Nucleon.

We give an overview of the current status of investigations of the polarization of gluons in the nucleon. We describe some of the physics of the spin-dependent gluon parton distribution and its phenomenology in high-energy polarized hadronic scattering. We also review the recent experimental results.
Date: October 22, 2007
Creator: Stratmann, M. & Vogelsang, W.
Object Type: Article
System: The UNT Digital Library
Final Report - From Measurements to Models: Cross-Comparison of Measured and Simulated Behavioral States of the Atmosphere (open access)

Final Report - From Measurements to Models: Cross-Comparison of Measured and Simulated Behavioral States of the Atmosphere

The ARM sites and the ARM Mobile Facility (AMF) were constructed to make measurements of the atmosphere and radiation system in order to quantify deficiencies in the simulation of clouds within models and to make improvements in those models. While the measurement infrastructure of ARM is well-developed and a model parameterization testbed capability has been established, additional effort is needed to develop statistical techniques which permit the comparison of simulation output from atmospheric models with actual measurements. Our project establishes a new methodology for objectively comparing ARM measurements to the outputs of leading global climate models and reanalysis data. The quantitative basis for this comparison is provided by a statistical procedure which establishes an exhaustive set of mutually-exclusive, recurring states of the atmosphere from sets of multivariate atmospheric and cloud conditions, and then classifies multivariate measurements or simulation outputs into those states. Whether measurements and models classify the atmosphere into the same states at specific locations through time provides an unequivocal comparison result. Times and locations in both geographic and state space of model-measurement agreement and disagreement will suggest directions for the collection of additional measurements at existing sites, provide insight into the global representativeness of the current ARM sites …
Date: October 22, 2007
Creator: Del Genio, Anthony D; Hoffman, Forrest M & Hargrove, Jr, William W
Object Type: Report
System: The UNT Digital Library
Sixth International Conference on Systems Biology (ICSB 2005) (open access)

Sixth International Conference on Systems Biology (ICSB 2005)

This grant supported the Sixth International Conference on Systems Biology (ICSB 2005), held in Boston, Massachusetts from October 19th to 22nd, 2005. The ICSB is the only major, annual, international conference focused exclusively on the important emerging field of systems biology. It draws together scientists with expertise in theoretical, computational and experimental approaches to understanding biological systems at many levels. Previous ICSB meetings have been held in Tokyo (2000), at Caltech (2001), at the Karolinska Institute (2002), at Washington University in St. Louis (2003), and in Heidelberg (2004). These conferences have been increasingly successful at bringing together the growing community of established and junior researchers with interests in this area. Boston is home to several groups that have shown leadership in the field and was therefore an ideal place to hold this conference . The executive committee for the conference comprised Jim Collins (Biomedical Engineering, Boston University), Marc Kirschner (chair of the new Department of Systems Biology at Harvard Medical School), Eric Lander (director of the Broad Institute of MIT and Harvard), Andrew Murray (director of Harvard’s Bauer Center for Genomics Research) and Peter Sorger (director of MIT’s Computational and Systems Biology Initiative). There are almost as many definitions of …
Date: October 22, 2005
Creator: Murray, Professor Andrew
Object Type: Report
System: The UNT Digital Library
LAT Observation of GRBs: Simulations and Sensitivity Studies (open access)

LAT Observation of GRBs: Simulations and Sensitivity Studies

The GLAST Large Area Telescope (LAT) is the next generation satellite experiment for high-energy gamma-ray astronomy. It employs a pair conversion technique to record photons in the energy range from 20 MeV to more than 300 GeV. The LAT will follow the steps from its predecessor EGRET (1991-2000), and will explore the high-energy gamma-ray sky with unprecedented capabilities. The observation of Gamma-Ray Bursts is one of the main science goal of the LAT: in this contribution we compute an estimation of the LAT sensitivity to GRB, adopting a phenomenological description of GRBs, where the high-energy emission in GRB is obtained extrapolating the observed BATSE spectrum up to LAT energies. The effect of the cosmological attenuation is included. We use the BATSE current catalog to build up our statistics.
Date: October 22, 2007
Creator: Omodei, Nicola; /INFN, Pisa; Norris, Jay & U., /Denver
Object Type: Article
System: The UNT Digital Library
Production of Ultrashort FEL XUV Pulses via a Reverse Undulator Taper (open access)

Production of Ultrashort FEL XUV Pulses via a Reverse Undulator Taper

We adapt the "reverse taper" scheme presented by Saldin etal. (Phys. Rev. ST Accel. Beams, 9, 050702 [2006]) for attosecond pulseproduction to the XUV/soft-xray regime. We find that that GW-level pulsesof a few femtosecond duration or shorter can be produced using electronbeams of quite moderate parameters and undulators of 20-m length orshorter. The output pulse is significantly shifted in wavelength relativeto the main background which permits a further increase in contrast ratiovia simple monochromatization. Moreover, the output pulse has a naturalwavelength chirp that allows further temporal compression, if wanted.Both positive and negative chirps can be produced depending uponthe signof the undulator taper.
Date: October 22, 2007
Creator: Fawley, William M.
Object Type: Article
System: The UNT Digital Library
Summary (open access)

Summary

The first International GLAST Symposium was held at Stanford, with less than a year to launch. Recent advances in the TeV and MeV ranges augur well for GLAST making major discoveries in GeV astronomy. Expectations for observations of several source types and backgrounds are summarized, along with some remaining organizational challenges.
Date: October 22, 2007
Creator: Blandford, Roger
Object Type: Article
System: The UNT Digital Library
String Cosmology: A Review (open access)

String Cosmology: A Review

We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the structure of an ultraviolet-complete theory.
Date: October 22, 2007
Creator: McAllister, Liam P. & Silverstein, Eva
Object Type: Article
System: The UNT Digital Library
Core Parameter Study for a 300-Mw Sodium Graphite Reactor (open access)

Core Parameter Study for a 300-Mw Sodium Graphite Reactor

A core parameter study of the operating costs was performed for a 300- Mwe sodium graphite reactor, a scale-up of the Hallam Power Reactor. The results of the study indicate that the core design is nsar optimum and that core modifications would reduce the power costs by less than 5%. The lattice spacing, fuel rod diameter, and sodium flow can be varied within a rather broad range without significant changes in power generation costs. The effect of the fuel cladning thickness is more significant; fuel cycle costs can be reduced if stainless steel canning is replaced with zirconium canning. Use of UC in place of uraniummolybdenum fuel would also permit cost reductions. (D.L.C.)
Date: October 22, 1959
Creator: Corcoran, W.P.
Object Type: Report
System: The UNT Digital Library
Proton Form Factors Measurements in the Time-Like Region (open access)

Proton Form Factors Measurements in the Time-Like Region

I present an overview of the measurement of the proton form factors in the time-like region. BABAR has recently measured with great accuracy the e{sup +}e{sup -} {yields} p{bar p} reaction from production threshold up to an energy of {approx} 4.5 GeV, finding evidence for a ratio of the electric to magnetic form factor greater than unity, contrary to expectation. In agreement with previous measurements, BABAR confirmed the steep rise of the magnetic form factor close to the p{bar p} mass threshold, suggesting the possible presence of an under-threshold N{bar N} vector state. These and other open questions related to the nucleon form factors both in the time-like and space-like region, wait for more data with different experimental techniques to be possibly solved.
Date: October 22, 2007
Creator: Anulli, F.
Object Type: Article
System: The UNT Digital Library
Electromagnetic Models of Extragalactic Jets (open access)

Electromagnetic Models of Extragalactic Jets

Relativistic jets may be confined by large-scale, anisotropic electromagnetic stresses that balance isotropic particle pressure and disordered magnetic field. A class of axisymmetric equilibrium jet models will be described and their radiative properties outlined under simple assumptions. The partition of the jet power between electromagnetic and mechanical forms and the comoving energy density between particles and magnetic field will be discussed. Current carrying jets may be recognized by their polarization patterns. Progress and prospects for measuring this using VLBI and GLAST observations will be summarized.
Date: October 22, 2007
Creator: Lisanti, M.; Blandford, R. & /KIPAC, Menlo Park
Object Type: Article
System: The UNT Digital Library
COLD TEST LOOP INTEGRATED TEST LOOP RESULTS (open access)

COLD TEST LOOP INTEGRATED TEST LOOP RESULTS

A testing facility (Cold Test Loop) was constructed and operated to demonstrate the efficacy of the Accelerated Waste Retrieval (AWR) Project's planned sluicing approach to the remediation of Silos 1 and 2 at the Fernald Environmental Management Project near Cincinnati, Ohio. The two silos contain almost 10,000 tons of radium-bearing low-level waste, which consists primarily of solids of raffinates from processing performed on ores from the Democratic Republic of Congo (commonly referred to as ''Belgium Congo ores'') for the recovery of uranium. These silos are 80 ft in diameter, 36 ft high to the center of the dome, and 26.75 ft to the top of the vertical side walls. The test facility contained two test systems, each designed for a specific purpose. The first system, the Integrated Test Loop (ITL), a near-full-scale plant including the actual equipment to be installed at the Fernald Site, was designed to demonstrate the sluicing operation and confirm the selection of a slurry pump, the optimal sluicing nozzle operation, and the preliminary design material balance. The second system, the Component Test Loop (CTL), was designed to evaluate many of the key individual components of the waste retrieval system over an extended run. The major results …
Date: October 22, 2003
Creator: Abraham, TJ
Object Type: Report
System: The UNT Digital Library
PILOT PEAT-BED TREATMENT SYSTEM FOR NPDES OUTFALL H-12 (open access)

PILOT PEAT-BED TREATMENT SYSTEM FOR NPDES OUTFALL H-12

A National Pollutant Discharge Elimination System (NPDES) Permit was issued to the Savannah River Site (SRS) by the South Carolina Department of Health and Environmental Control (SCDHEC) and became effective on December 1, 2003. The new permit contained revised limits for copper and zinc derived by adjusting the South Carolina aquatic life water quality standards in accordance with dissolved metals criteria. The new copper and zinc limits are very low and may not be met consistently at Outfall H-12. The outfall has periodically exceeded the new 6 {micro}g/l (0.006 mg/L) monthly average limit and the 8 {micro}g/l (0.008 mg/L) maximum limit for copper and recently has begun exceeding the 100 {micro}g/l (0.100 mg/L) limit for zinc. The compliance date for Outfall H-12 is November 1, 2008. A study was conducted on this outfall and other outfalls to evaluate possible alternatives for meeting the new permit limits (Shipman and Bugher 2004). The study team recommended construction of a peat bed for treatment of the Outfall H-12 effluent. This recommendation was repeated by a second alternatives study team in 2007 (WSRC 2007). A bench-scale laboratory study demonstrated the feasibility of peat-bed treatment for Outfall H-12 effluent, with the peat demonstrating excellent removal …
Date: October 22, 2007
Creator: Halverson, N; Ralph Nichols, R & Topher Berry, T
Object Type: Report
System: The UNT Digital Library
Insulation and Heat Treatment of Bi-2212 Wire for Wind-and-React Coils (open access)

Insulation and Heat Treatment of Bi-2212 Wire for Wind-and-React Coils

Higher Field Magnets demand higher field materials such as Bi-2212 round superconducting wire. The Bi-2212 wire manufacture process depends on the coil fabrication method and wire insulation material. Considering the wind-and-react method, the coil must unifirmly heated to the melt temperature and uniformly cooled to the solidification temperature. During heat treat cycle for tightly wound coils, the leakage melt from conductor can chemically react with insulation on the conductor and creat short turns in the coils. In this research project, conductor, insulation, and coils are made to systemically study the suitable insulation materials, coil fabrication method, and heat treatment cycles. In this phase I study, 800 meters Bi-2212 wire with 3 different insulation materials have been produced. Best insulation material has been identified after testing six small coils for insulation integrity and critical current at 4.2 K. Four larger coils (2" dia) have been also made with Bi-2212 wrapped with best insulation and with different heattreatment cycle. These coils were tested for Ic in a 6T background field and at 4.2 K. The test result shows that Ic from 4 coils are very close to short samples (1 meter) result. It demonstrates that HTS coils can be made with Bi-2212 …
Date: October 22, 2007
Creator: Hwang, Peter K. F.
Object Type: Report
System: The UNT Digital Library
Using Pin as a Memory Reference Generator for Multiprocessor Simulation (open access)

Using Pin as a Memory Reference Generator for Multiprocessor Simulation

In this paper we describe how we have used Pin to generate a multithreaded reference stream for simulation of a multiprocessor on a uniprocessor. We have taken special care to model as accurately as possible the effects of cache coherence protocol state, and lock and barrier synchronization on the performance of multithreaded applications running on multiprocessor hardware. We first describe a simplified version of the algorithm, which uses semaphores to synchronize instrumented application threads and the simulator on every memory reference. We then describe modifications to that algorithm to model the microarchitectural features of the Itanium2 that affect the timing of memory reference issue. An experimental evaluation determines that while cycle-accurate multithreaded simulation is possible using our approach, the use of semaphores has a negative impact on the performance of the simulator.
Date: October 22, 2005
Creator: McCurdy, C
Object Type: Report
System: The UNT Digital Library
Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition (open access)

Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition

We study dependence of jet quenching on matter density, using 'tomography' of the fireball provided by RHIC data on azimuthal anisotropy v{sub 2} of high p{sub t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a 'layer-wise geometrical limit' v{sub 2}{sup max} which is indeed above the data v{sub 2} < v{sub x}{sup max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T{sub c} region. We show two models that simultaneously describe the high p{sub t} v{sub 2} and R{sub AA} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T{sub c} region relative to QGP at T > T{sub c}. One possible reason for that may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.
Date: October 22, 2008
Creator: Liao, Jinfeng & Shuryak, Edward
Object Type: Article
System: The UNT Digital Library
Commercial and Cost Effective Production of Two-Dimensional Read-Out Boards for Sub-Atomic Particle Detectors (open access)

Commercial and Cost Effective Production of Two-Dimensional Read-Out Boards for Sub-Atomic Particle Detectors

Tech-Etch has considerable experience in numerous related high precision etched Kapton® products including production of GEM foils. The required precision and production process for 2-D readout boards is similar to that developed for GEM foil production. Additionally, Tech-Etch has strong ties with several research institutions (namely Brookhaven National Laboratory, MIT and Yale University) that can help design and evaluate the performance of the readout boards produced at Tech-Etch. Since Tech-Etch is a small company, it also has the capability to produce a large variety of part configurations, optimized for a particular customer’s requirements. We report results from research aimed at developing and demonstrating production of 2-D readout structures for GEM (Gas Electron Multiplier) charged particle tracking chambers at Tech-Etch. Readout boards of two types, bi-planar and single plane, were fabricated and evaluated. The results show that Tech-Etch can produce suitable boards of either type however the single plane board has a number of advantages both in production and use that will likely make it the preferred choice for GEM tracking chambers.
Date: October 22, 2010
Creator: Crary, David & Majka, Richard
Object Type: Report
System: The UNT Digital Library
Comments on Economides and Ehlig-Economides,"Sequestering carbon dioxide in a closed underground volume," SPE 124430, October 2009 (open access)

Comments on Economides and Ehlig-Economides,"Sequestering carbon dioxide in a closed underground volume," SPE 124430, October 2009

The paper examines the pressure increase resulting from injection of CO2 into a 1D radial system with closed boundaries. The finding is that unacceptably high pressures are obtained when only 1% or less of the pore volume is occupied by injected CO2. These results are used to make the general conclusion that large-scale CCS is not feasible.
Date: October 22, 2009
Creator: Oldenburg, Curt; Pruess, Karsten; Birkholzer, Jens & Doughty, Christine
Object Type: Report
System: The UNT Digital Library
United States Department of Energy Office of Environmental Management Technology Development Report Fiscal Year 2010 (open access)

United States Department of Energy Office of Environmental Management Technology Development Report Fiscal Year 2010

The mission of the Department of Energy's (DOE's) Office of Environmental Management (EM) is to clean up the environmental legacy of nuclear weapons research and production during the Cold War. That mission includes cleaning up nuclear waste, contaminated groundwater and soil, nuclear materials, and contaminated facilities covering two million acres of land in thirty-five states. EM's principal program goals include timely completion of tank waste treatment facilities, reduction of the life-cycle costs and acceleration of the cleanup of the Cold War legacy, and reduction of the EM footprint. The mission of the EM Technology Innovation and Development program is to transform science and innovation into practical solutions to achieve the EM mission. During fiscal year 2010 (October 2009-September 2010), EM focused upon accelerating environmental cleanup by expeditiously filling identified gaps in available knowledge and technology in the EM program areas. This report describes some of the approaches and transformational technologies in tank waste processing, groundwater and soil remediation, nuclear materials disposition, and facility deactivation and decommissioning developed during fiscal year 2010 that will enable EM to meet its most pressing program goals.
Date: October 22, 2010
Creator: Bush, S.
Object Type: Report
System: The UNT Digital Library
SUPPLEMENT TO: CURVE PLOTTING ROUTINE FOR THE ORACLE (open access)

SUPPLEMENT TO: CURVE PLOTTING ROUTINE FOR THE ORACLE

None
Date: October 22, 1957
Creator: Lietzke, M.P.
Object Type: Report
System: The UNT Digital Library
Electromagnetic pulse source characteristics experiment on an underground nuclear event (open access)

Electromagnetic pulse source characteristics experiment on an underground nuclear event

From EMP technical meeting; Kirtland AFB, New Mexico, USA (25 Sep 1973). Under sponsorship of the Advanced Research Projects Agency, the Lawrence Livermore Laboratory conducted an EMP experiment in conjunction with an underground nuclear event. The purpose of the overall study of which this experiment was a part was to document the characteristics of EMP signals generated by various underground nuclear events to provide checks for theoretical models under development. A major goal was to establish how a specific event configuration affects the signals generated. For this experiment, two separate EMP source mechanisms were considered: that due to an asymmetric gamma ray distribution resulting from shielding and configuration constraints in the vicinity of the device and that due to current induced on the line-of-sight pipe. The instrumentation was not ideally located to sort out the two mechanisms because of significant differences between the planned and as-fired configuration. Nevertheless, signals characteristic of the two mechanisms seem to be apparent in the data. An impulsive (10 MHz) component of the signal is probably a result of the asymmetric gamma distribution. A ringing component (1 MHz) has been attributed to currents on the line-of- sight pipe. (auth)
Date: October 22, 1973
Creator: Knapp, M. W. & Bailey, N. D.
Object Type: Article
System: The UNT Digital Library
Neon 18 (open access)

Neon 18

None
Date: October 22, 1953
Creator: Gow, J. D. & Alvarez, L. W.
Object Type: Report
System: The UNT Digital Library
Development of Hydrogen-Oxygen Recombiners. Progress Report (open access)

Development of Hydrogen-Oxygen Recombiners. Progress Report

It is the purpose of this report to review our experience with recombiners under actual reactor operating conditions, and to discuss new developments in the field.
Date: October 22, 1953
Creator: Ransohoff, J.A. & Spiewak, I.
Object Type: Report
System: The UNT Digital Library