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A neutron sensor based on synthetic single crystal diamond (open access)

A neutron sensor based on synthetic single crystal diamond

We report the first neutron data for a single crystal Chemical Vapor Deposition (CVD) diamond sensor. Results are presented for 2.5, 14.1, and 14.9 MeV incident neutrons. We show that the energy resolution for 14.1 MeV neutrons is at least 2.9% (as limited by the energy spread of the incident neutrons), and perhaps as good as 0.4% (as extrapolated from high resolution {alpha} particle data). This result could be relevant to fusion neutron spectroscopy at machines like the International Thermonuclear Experimental Reactor (ITER). We also show that our sensor has a high neutron linear attenuation coefficient, due to the high atomic density of diamond, and this could lead to applications in fission neutron detection.
Date: October 17, 2003
Creator: Schmid, G. J.; Koch, J. A.; Lerche, R. A. & Moran, M. J.
System: The UNT Digital Library
Correlated Nitrogen and Carbon Anomalies in an Anhydrous Interplanetary Dust Particle - Implications for Extraterrestrial Organic Matter Accreted by the Prebiotic Earth (open access)

Correlated Nitrogen and Carbon Anomalies in an Anhydrous Interplanetary Dust Particle - Implications for Extraterrestrial Organic Matter Accreted by the Prebiotic Earth

Given the ubiquitous presence of H and N isotopic anomalies in interplanetary dust particles (IDPs) and their probable association with carbonaceous material, the lack of similar isotopic anomalies in C has been a major conundrum. We report here the first observation of correlated N and C isotopic anomalies in organic matter within an anhydrous IDP. The {sup 15}N composition of the anomalous region is the highest seen to date in an IDP and is accompanied by a moderate depletion in {sup 13}C. Our observations establish the presence of hetero-atomic organic compounds of presolar origin among the constant flux of carbonaceous material accreting to the terrestrial planets within IDPs. Theoretical models suggest that low temperature formation of organic compounds in cold interstellar molecular clouds does produce C and N fractionations, but it remains to be seen if these models can reproduce the specific effects we observe here.
Date: December 17, 2003
Creator: Floss, C; Stadermann, F J; Bradley, J P; Dai, Z; Bajt, S & Graham, G
System: The UNT Digital Library
Tool Gear: Infrastructure for Parallel Tools (open access)

Tool Gear: Infrastructure for Parallel Tools

Tool Gear is a software infrastructure for developing performance analysis and other tools. Unlike existing integrated toolkits, which focus on providing a suite of capabilities, Tool Gear is designed to help tool developers create new tools quickly. It combines dynamic instrumentation capabilities with an efficient database and a sophisticated and extensible graphical user interface. This paper describes the design of Tool Gear and presents examples of tools that have been built with it.
Date: April 17, 2003
Creator: May, J & Gyllenhaal, J
System: The UNT Digital Library
Theoretical Progress for the Associated Production of a Higgs Boson With Heavy Quarks at Hadron Colliders. (open access)

Theoretical Progress for the Associated Production of a Higgs Boson With Heavy Quarks at Hadron Colliders.

The production of a Higgs boson in association with a pair of t{bar t} or b{bar b} quarks plays a very important role at both the Tevatron and the Large Hadron Collider. The theoretical prediction of the corresponding cross sections has been improved by including the complete next-to-leading order QCD corrections. After a brief introduction, we review the results obtained for both the Tevatron and the Large Hadron Collider.
Date: July 17, 2003
Creator: Dawson, S.; Jackson, C. B.; Orr, L. H.; Reina, L. & Wackeroth, D.
System: The UNT Digital Library
Moment Magnitude Calibration for the Eastern Mediterranean Region from Broadband Regional Coda Envelopes (open access)

Moment Magnitude Calibration for the Eastern Mediterranean Region from Broadband Regional Coda Envelopes

The following is an overview of results from ROA01-32 that focuses on an empirical method of calibrating stable seismic source moment-rate spectra derived from regional coda envelopes using broadband stations. The main goal was to develop a regional magnitude methodology that had the following properties: (1) it is tied to an absolute scale and is thus unbiased and transportable; (2) it can be tied seamlessly to the well-established teleseismic and regional catalogs; (3) it is applicable to small events using a sparse network of regional stations; (4) it is flexible enough to utilize S{sub n}-coda, L{sub g}-coda, or P-coda, whichever phase has the best signal-to-noise ratio. The results of this calibration yield source spectra and derived magnitudes that were more stable than any other direct-phase measure to date. Our empirical procedure accounted for all propagation, site, and S-to-coda transfer function effects. The resultant coda-derived moment-rate spectra were used to provide traditional band-limited magnitude (e.g., M{sub L}, m{sub b} etc.) as well as an unbiased, unsaturated magnitude (moment magnitude, M{sub w}) that is tied to a physical measure of earthquake size (i.e., seismic moment). We validated our results by comparing our coda-derived moment estimates with those obtained from long-period waveform modeling. …
Date: July 17, 2003
Creator: Mayeda, K; Eken, T; Hofstetter, A; Turkelli, N; O'Boyle, J; Orgulu, G et al.
System: The UNT Digital Library
Adaptive Optics Applications in Vision Science (open access)

Adaptive Optics Applications in Vision Science

Adaptive optics can be used to correct the aberrations in the human eye caused by imperfections in the cornea and the lens and thereby, improve image quality both looking into and out of the eye. Under the auspices of the NSF Center for Adaptive Optics and the DOE Biomedical Engineering Program, Lawrence Livermore National Laboratory has joined together with leading vision science researchers around the country to develop and test new ophthalmic imaging systems using novel wavefront corrector technologies. Results of preliminary comparative evaluations of these technologies in initial system tests show promise for future clinical utility.
Date: March 17, 2003
Creator: Olivier, S. S.
System: The UNT Digital Library
Nondipole effects in the photoionization of Xe 4d5/2 and 4d3/2: Evidence for quadrupole satellites (open access)

Nondipole effects in the photoionization of Xe 4d5/2 and 4d3/2: Evidence for quadrupole satellites

Strong evidence for the existence and importance of quadrupole satellite transitions is found in spin-orbit-resolved Xe 4d nondipole photoionization in a combined experimental/theoretical study.
Date: November 17, 2003
Creator: Manson, S T; Johnson, W R; Lindle, D W; Rolles, D.; Cheng, K T; Zhou, H L et al.
System: The UNT Digital Library
rSUGRA: Putting Nonuniversal Gaugino Masses on the (W)MAP (open access)

rSUGRA: Putting Nonuniversal Gaugino Masses on the (W)MAP

In this talk, we investigate the relic density and direct detection prospects of rSUGRA, a simple paradigm for supersymmetry breaking that allows for nonuniversal gaugino masses. We present updated plots reflecting the latest cosmological measurements from WMAP.
Date: June 17, 2003
Creator: Birkedal-Hansen, Andreas
System: The UNT Digital Library
Nonlinear diffusion and image contour enhancement (open access)

Nonlinear diffusion and image contour enhancement

None
Date: February 17, 2003
Creator: Barenblatt, G.I. & Vazquez, J.L.
System: The UNT Digital Library
Flow focusing in unsaturated fracture networks: A numerical investigation (open access)

Flow focusing in unsaturated fracture networks: A numerical investigation

A numerical modeling study is presented to investigate flow-focusing phenomena in a large-scale fracture network, constructed using field data collected from the unsaturated zone of Yucca Mountain, Nevada, the proposed repository site for high-level nuclear waste. The two-dimensional fracture network for an area of 100 m x 150 m contains more than 20,000 fractures. Steady-state unsaturated flow in the fracture network is investigated for different boundary conditions and rock properties. Simulation results indicate that flow paths are generally vertical, and that horizontal fractures mainly provide pathways between neighboring vertical paths. In addition to fracture properties, flow-focusing phenomena are also affected by rock-matrix permeability, with lower matrix permeability leading to a high degree of flow focusing. The simulation results further indicate that the average spacing between flow paths in a layered system tends to increase and flow tends to becomes more focused, with depth.
Date: April 17, 2003
Creator: Zhang, Keni; Wu, Yu-Shu; Bodvarsson, G.S. & Liu, Hui-Hai
System: The UNT Digital Library
Grid collector: An event catalog with automated file management (open access)

Grid collector: An event catalog with automated file management

High Energy Nuclear Physics (HENP) experiments such as STAR at BNL and ATLAS at CERN produce large amounts of data that are stored as files on mass storage systems in computer centers. In these files, the basic unit of data is an event. Analysis is typically performed on a selected set of events. The files containing these events have to be located, copied from mass storage systems to disks before analysis, and removed when no longer needed. These file management tasks are tedious and time consuming. Typically, all events contained in the files are read into memory before a selection is made. Since the time to read the events dominate the overall execution time, reading the unwanted event needlessly increases the analysis time. The Grid Collector is a set of software modules that works together to address these two issues. It automates the file management tasks and provides ''direct'' access to the selected events for analyses. It is currently integrated with the STAR analysis framework. The users can select events based on tags, such as, ''production date between March 10 and 20, and the number of charged tracks > 100.'' The Grid Collector locates the files containing relevant events, transfers …
Date: October 17, 2003
Creator: Wu, Kesheng; Zhang, Wei-Ming; Sim, Alexander; Gu, Junmin & Shoshani, Arie
System: The UNT Digital Library
Repair of a Melter Pour Spout Using an Expanding Ring (open access)

Repair of a Melter Pour Spout Using an Expanding Ring

An expanding ring was developed that provided remote repair of the pour spout for a radioactive waste vitrification melter. This passive device used gas pressure to expand a metal ring against the irregularly shaped pour spout wall. Laboratory modeling and testing were performed for proof of concept and optimization before final design and field deployment. The ring expanded radially more than 4.8 mm and successfully repaired the melter pour spout allowing continued glass pouring operation.
Date: June 17, 2003
Creator: Imrich, K. J.
System: The UNT Digital Library
Jet Breakup and Spray Formation in a Diesel Engine (open access)

Jet Breakup and Spray Formation in a Diesel Engine

The breakup of injected fuel into spray is of key interest to the design of a fuel efficient, nonpolluting diesel engine. We report preliminary progress on the numerical simulation of diesel fuel injection spray with the front tracking code FronTier. Our simulation design is set to match experiments at ANL, and our present agreement is semi-quantitative. Future efforts will include mesh refinement studies, which will better model the turbulent flow.
Date: June 17, 2003
Creator: Glimm, J.; Li, X.; Kim, M. N.; Oh, W.; Marchese, A.; Samulyak, R. et al.
System: The UNT Digital Library
Status of the MINOS Experiment (open access)

Status of the MINOS Experiment

We report on the status of the MINOS long baseline neutrino experiment presently under construction at the Fermi National Accelerator Laboratory and the Soudan mine. There is growing evidence that the solar neutrino and atmospheric neutrino anomalies [1] are the result of neutrino oscillations. The MINOS experiment is a long baseline neutrino oscillation experiment designed to study the region of parameter space indicated by the SuperKamiokande atmospheric neutrino results [2]. The experiment consists of two detectors, one with a mass of 980 tons located at Fermilab (the near detector) and the other of mass 5400 tons located 731 km away in the Soudan mine in northern Minnesota (the far detector). The third component is the neutrino beam which is currently under construction at Fermilab.
Date: March 17, 2003
Creator: Buckley-Geer, Elizabeth
System: The UNT Digital Library
Measurements of field decay and snapback effect on Tevatron dipole magnets (open access)

Measurements of field decay and snapback effect on Tevatron dipole magnets

The performance of Fermilab's Tevatron accelerator, currently in its Run II stage, is degraded by beam loss and emittance dilution during ramping from injection to collision energy. This could be related in part to insufficient compensation of dynamic effects such as the decay of the magnetic field in the dipoles during the dwell at injection and the following so-called snapback during the first few seconds of the energy ramp. The two effects are closely related and depend on the powering history of the magnets. Dynamic effects, which were originally discovered at the Tevatron, were investigated on Tevatron magnets in various past measurement campaigns in the 1980s and later in 1996. This paper reports on the most recent measurements performed on an additional set of Tevatron magnets.
Date: June 17, 2003
Creator: al., Gueorgui V Velev et
System: The UNT Digital Library
Investigation of Plutonium and Uranium Precipitation Behavior with Gadolinium as a Neutron Poison (open access)

Investigation of Plutonium and Uranium Precipitation Behavior with Gadolinium as a Neutron Poison

The caustic precipitation of plutonium (Pu)-containing solutions has been investigated to determine whether the presence of 3:1 uranium (U):Pu in solutions stored in the H-Canyon Facility at the U.S. Department of Energy's (DOE) Savannah River Site (SRS) would adversely impact the use of gadolinium nitrate (Gd(NO3)3) as a neutron poison. In the past, this disposition strategy has been successfully used to discard solutions containing approximately 100 kg of Pu to the SRS high level waste (HLW) system. In the current experiments, gadolinium (as Gd(NO3)3) was added to samples of a 3:1 U:Pu solution, a surrogate 3 g/L U solution, and a surrogate 3 g/L U with 1 g/L Pu solution. A series of experiments was then performed to observe and characterize the precipitate at selected pH values. Solids formed at pH 4.5 and were found to contain at least 50 percent of the U and 94 percent of the Pu, but only 6 percent of the Gd. As the pH of the solution increased (e.g., pH greater than 14 with 1.2 or 3.6 M sodium hydroxide (NaOH) excess), the precipitate contained greater than 99 percent of the Pu, U, and Gd. After the pH greater than 14 systems were undisturbed …
Date: October 17, 2003
Creator: Visser, A.E.
System: The UNT Digital Library
BTeV Silicon Detector integration issues (open access)

BTeV Silicon Detector integration issues

The BTeV silicon pixel detector contains 30 planar stations that reside inside the vacuum of the Tevatron machine close to the beam. The detector sits within the analysis magnet. The location of the detector leads to unique constraints on the mechanical support, cooling systems, RF shielding, flex-cable feedthrough, and vacuum system.The design is based on these constraints and a number of technical specifications required of the detector. The baseline design was presented at the Pixel 2002 Conference.
Date: October 17, 2003
Creator: al., Mayling Wong et
System: The UNT Digital Library
Bnl Prediction of Nupecs Field Model Tests of Npp Structures Subject to Small to Moderate Magnitude Earthquakes. (open access)

Bnl Prediction of Nupecs Field Model Tests of Npp Structures Subject to Small to Moderate Magnitude Earthquakes.

As part of a verification test program for seismic analysis codes for NPP structures, the Nuclear Power Engineering Corporation (NUPEC) of Japan has conducted a series of field model test programs to ensure the adequacy of methodologies employed for seismic analyses of NPP structures. A collaborative program between the United States and Japan was developed to study seismic issues related to NPP applications. The US Nuclear Regulatory Commission (NRC) and its contractor, Brookhaven National Laboratory (BNL), are participating in this program to apply common analysis procedures to predict both free field and soil-structure Interaction (SSI) responses to recorded earthquake events, including embedment and dynamic cross interaction (DCI) effects. This paper describes the BNL effort to predict seismic responses of the large-scale realistic model structures for reactor and turbine buildings at the NUPEC test facility in northern Japan. The NUPEC test program has collected a large amount of recorded earthquake response data (both free-field and in-structure) from these test model structures. The BNL free-field analyses were performed with the CARES program while the SSI analyses were preformed using the SASS12000 computer code. The BNL analysis includes both embedded and excavated conditions, as well as the DCI effect, The BNL analysis results …
Date: August 17, 2003
Creator: Xu, J.; Costantino, C.; Hofmayer, C.; Murphy, A. & Kitada, Y.
System: The UNT Digital Library
Prospects for next generation long-baseline oscillation experiments (open access)

Prospects for next generation long-baseline oscillation experiments

This document describes some of the exciting possibilities for the next steps in the field of long baseline neutrino oscillation measurements. Because the primary goals of these new experiments are so different from those of the current generation, one cannot simply increase the running time or detector mass of the current programs. There are several new strategies which have been discussed for taking the next steps: sometimes the detectors, sometimes the beamlines, and sometimes both are radically different from what is now in place.
Date: June 17, 2003
Creator: Harris, Deborah A
System: The UNT Digital Library
Microbial Forensics: A Scientific Assessment (open access)

Microbial Forensics: A Scientific Assessment

Microorganisms have been used as weapons in criminal acts, most recently highlighted by the terrorist attack using anthrax in the fall of 2001. Although such ''biocrimes'' are few compared with other crimes, these acts raise questions about the ability to provide forensic evidence for criminal prosecution that can be used to identify the source of the microorganisms used as a weapon and, more importantly, the perpetrator of the crime. Microbiologists traditionally investigate the sources of microorganisms in epidemiological investigations, but rarely have been asked to assist in criminal investigations. A colloquium was convened by the American Academy of Microbiology in Burlington, Vermont, on June 7-9, 2002, in which 25 interdisciplinary, expert scientists representing evolutionary microbiology, ecology, genomics, genetics, bioinformatics, forensics, chemistry, and clinical microbiology, deliberated on issues in microbial forensics. The colloquium's purpose was to consider issues relating to microbial forensics, which included a detailed identification of a microorganism used in a bioattack and analysis of such a microorganism and related materials to identify its forensically meaningful source--the perpetrators of the bioattack. The colloquium examined the application of microbial forensics to assist in resolving biocrimes with a focus on what research and education are needed to facilitate the use of …
Date: February 17, 2003
Creator: Keim, Paul
System: The UNT Digital Library
HRTEM at half-Angstrom resolution: From OAM to TEAM (open access)

HRTEM at half-Angstrom resolution: From OAM to TEAM

Transmission electron microscopy (TEM) at sub-Angstrom resolution is important for nanotechnology. Identifying atom positions requires appropriate resolution, the ability to separate distinct objects in images. With Cs corrected, the information limit of the TEM controls resolution. The OAM has demonstrated that a resolution of 0.78A is possible. The TEAM (transmission electron achromatic microscope) will be a TEM using hardware correction of Cs with a monochromator to improve its information limit beyond that of the OAM by improvement of the electron-beam energy spread. It is shown that A 300keV HRTEM TEAM does not require a Cc corrector to reach 0.5A as long as beam energy spread and objective-lens current ripple are lowered sufficiently. A lower-voltage TEAM will require stricter limits on objective-lens current ripple to reach the targeted 0.5A resolution. No improvement in HT ripple or noise is required to improve the information limit per se since the monochromator determines the energy spread in the beam. However, improved HT ripple and noise will improve the beam current statistics (number of electrons passing through the monochromator) by placing more of the electrons closer to the center of the energy-spread distribution
Date: February 17, 2003
Creator: O'Keefe, Michael A.
System: The UNT Digital Library
CDF - Run II Status and Prospects (open access)

CDF - Run II Status and Prospects

After a five year upgrade period, the CDF detector located at the Fermilab Tevatron Collider is back in operation taking high quality data with all subsystems functional. We report on the status of the CDF experiment in Run II and discuss the start-up of the Tevatron accelerator. First physics results from CDF are presented. We also discuss the prospects for B physics in RunII, in particular the measurements of B{sub S}{sup 0} flavour oscillations and CP violation in B decays.
Date: March 17, 2003
Creator: Paulini, Manfred
System: The UNT Digital Library
Run II diffractive measurements at CDF (open access)

Run II diffractive measurements at CDF

We present results on hard diffraction obtained by the CDF Collaboration in Run II proton-antiproton collisions at the Fermilab Tevatron. Run I CDF results on hard diffraction are also reviewed.
Date: September 17, 2003
Creator: Terashi, K.
System: The UNT Digital Library
Resurrection of beam conditioning for free electron lasers (open access)

Resurrection of beam conditioning for free electron lasers

Recently Emma and Stupakov identified a fatal flaw in a Free Electron Laser (FEL) beam conditioning scheme. They showed that the conditioning is always accompanied by a projected transverse emittance growth that is so large as to make the beam conditioning completely impractical for short wavelength FELs. Furthermore, they provided a general proof along with evidence of computer simulation and reached a conclusion that any beam conditioner, regardless of the method, would suffer from the same constraints and limitations. In this paper, the author proposes an easy surgical removal of the fatal flaw by making a critical yet simple modification to the very scheme analyzed, thus resurrect the beam conditioning for short wavelength FELs. More generally, the also explain why a general search for removing have failed, why the concept and definition of beam conditioning.
Date: February 17, 2003
Creator: Xie, Ming
System: The UNT Digital Library