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Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams (open access)

Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams

Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.
Date: October 24, 2011
Creator: Siemann, R. H.
System: The UNT Digital Library
ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity (open access)

ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity

Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications.
Date: March 24, 2011
Creator: Biener, M M; Biener, J; Wichmann, A; Wittstock, A; Baumann, T F; Baeumer, M et al.
System: The UNT Digital Library
Beam Transport in Dielectric Wall Accelerator for Intensity Modulated Proton Therapy (open access)

Beam Transport in Dielectric Wall Accelerator for Intensity Modulated Proton Therapy

None
Date: August 24, 2011
Creator: Chen, Y.; Blackfield, D.; Nelson, S. D. & Poole, B.
System: The UNT Digital Library
BLV-2011 Workshop, September 22-24, 2011 (open access)

BLV-2011 Workshop, September 22-24, 2011

The 3-rd International 3-days Workshop "Baryon and Lepton Number Violations: BLV-2011" took place at Gatlinburg, TN for September 22-24, 2011. Workshop was organized by the International Organizing Committee and had received advice from the International Program Advisory Committee (see Appendix 1). Workshop was co-chaired by Pavel Fileviez Perez (University of Wisconsin) for theory and Yuri Kamyshkov (University of Tennessee) for experiment and local organization. Workshop was supported and sponsored by the University of Tennessee, Indiana University, North Carolina State University together with TUNL, and by the HEP office of the Department of Energy. DOE financial support in this sponsoring grant was $8,000; that was 23% of the overall budget of the Workshop. Remaining 77% were provided by the sponsoring Universities. Workshop sponsors including DOE are shown on the Workshop webpage. There were 90 workshop participants with 52 from US and remaining from Bosnia/Herzegovina (1), Brazil (1), China (1), Columbia (1), France (1), Germany (10), Italy (9), Japan (4), Russian Federation (3), Slovenia (2), Spain (4), and Switzerland (1). Among Workshop participants there were 17 postdocs and young researchers and 11 graduate students. Total 67 talks and 14 posters were presented at Workshop during 3 days of sessions. Appendix 2 shows …
Date: September 24, 2011
Creator: Committee, Y. A. Kamyshkov (University of Tennessee) co-Chair of the Workshop Organizing; Committee, P. Fileviez Perez (University of Wisconsin) co-Chair of the Workshop Organizing; W. M. Snow (Indiana University), member of Workshop Organizing Committee & A.R. Young (North Carolina State University), member of Workshop Organizing Committee
System: The UNT Digital Library
The Chandra Deep Field-South Survey: 4 Ms Source Catalogs (open access)

The Chandra Deep Field-South Survey: 4 Ms Source Catalogs

This article presents source catalogs for the 4 Ms Chandra Deep Field-South.
Date: May 24, 2011
Creator: Xue, Yongquan; Luo, Bin; Brandt, William Nielsen; Bauer, Franz E.; Lehmer, Bret; Broos, Patrick et al.
System: The UNT Digital Library
Computational Hydrocode Study of Target Damage due to Fragment-Blast Impact (open access)

Computational Hydrocode Study of Target Damage due to Fragment-Blast Impact

A target's terminal ballistic effects involving explosively generated fragments, along with the original blast, are of critical importance for many different security and safety related applications. Personnel safety and protective building design are but a few of the practical disciplines that can gain from improved understanding combined loading effects. Traditionally, any engineering level analysis or design effort involving explosions would divide the target damage analysis into two correspondingly critical areas: blast wave and fragment related impact effects. The hypothesis of this paper lies in the supposition that a linear combination of a blast-fragment loading, coupled with an accurate target response description, can lead to a non-linear target damage effect. This non-linear target response could then stand as the basis of defining what a synergistic or combined frag-blast loading might actually look like. The table below, taken from Walters, et. al. categorizes some of the critical parameters driving any combined target damage effect and drives the evaluation of results. Based on table 1 it becomes clear that any combined frag-blast analysis would need to account for the target response matching similar ranges for the mechanics described above. Of interest are the critical times upon which a blast event or fragment impact …
Date: March 24, 2011
Creator: Hatch-Aguilar, T; Najjar, F & Szymanski, E
System: The UNT Digital Library
Constrained-Transport Magnetohydrodynamics with Adaptive-Mesh-Refinement in CHARM (open access)

Constrained-Transport Magnetohydrodynamics with Adaptive-Mesh-Refinement in CHARM

We present the implementation of a three-dimensional, second order accurate Godunov-type algorithm for magneto-hydrodynamic (MHD), in the adaptivemesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit Corner-Transport-Upwind (CTU) scheme. Thefluid quantities are cell-centered and are updated using the Piecewise-Parabolic- Method (PPM), while the magnetic field variables are face-centered and areevolved through application of the Stokes theorem on cell edges via a Constrained- Transport (CT) method. The so-called ?multidimensional MHD source terms?required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracyor robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These includeface-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. Thecode is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests,a three-dimensional shock-cloud interaction problem and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence isshown to remain negligible throughout. Subject headings: cosmology: theory - methods: numerical
Date: May 24, 2011
Creator: Miniatii, Francesco & Martin, Daniel
System: The UNT Digital Library
DEPOSITION OF NIOBIUM AND OTHER SUPERCONDUCTING MATERIALS WITH HIGH POWER IMPULSE MAGNETRON SPUTTERING: CONCEPT AND FIRST RESULTS (open access)

DEPOSITION OF NIOBIUM AND OTHER SUPERCONDUCTING MATERIALS WITH HIGH POWER IMPULSE MAGNETRON SPUTTERING: CONCEPT AND FIRST RESULTS

Niobium coatings on copper cavities have been considered as a cost-efficient replacement of bulk niobium RF cavities, however, coatings made by magnetron sputtering have not quite lived up to high expectations due to Q-slope and other issues. High power impulse magnetron sputtering (HIPIMS) is a promising emerging coatings technology which combines magnetron sputtering with a pulsed power approach. The magnetron is turned into a metal plasma source by using very high peak power density of ~ 1 kW/cm{sup 2}. In this contribution, the cavity coatings concept with HIPIMS is explained. A system with two cylindrical, movable magnetrons was set up with custom magnetrons small enough to be inserted into 1.3 GHz cavities. Preliminary data on niobium HIPIMS plasma and the resulting coatings are presented. The HIPIMS approach has the potential to be extended to film systems beyond niobium, including other superconducting materials and/or multilayer systems.
Date: July 24, 2011
Creator: High Current Electronics Institute, Tomsk, Russia; Anders, Andre; Mendelsberg, Rueben J.; Lim, Sunnie; Mentink, Matthijs; Slack, Jonathan L. et al.
System: The UNT Digital Library
Design of a 10**36 CM-2 S-1 Super-B Factory (open access)

Design of a 10**36 CM-2 S-1 Super-B Factory

Parameters have been studied for a high luminosity e{sup +}e{sup -} collider operating at the Upsilon 4S that would deliver a luminosity of 1 to 4 x 10{sup 36}/cm{sup 2}/s. This collider, called a Super-B Factory, would use a combination of linear collider and storage ring techniques. In this scheme an electron beam and a positron beam are stored in low-emittance damping rings similar to those designed for a Linear Collider (LC) or the next generation light source. A LC style interaction region is included in the ring to produce sub-millimeter vertical beta functions at the collision point. A large crossing angle (+/- 24 mrad) is used at the collision point to allow beam separation. A crab-waist scheme is used to reduce the hourglass effect and restore peak luminosity. Beam currents of 1.8 A at 4 x 7 GeV in 1251 bunches can produce a luminosity of 10{sup 36}/cm{sup 2}/s with upgrade possibilities. Such a collider would produce an integrated luminosity of about 10,000 fb{sup -1} (10 ab{sup -1}) in a running year (10{sup 7} sec) at the {gamma}(4S) resonance. Further possibilities include having longitudinally polarized e- at the IR and operating at the J/Psi and Psi beam energies.
Date: October 24, 2011
Creator: Biagini, M.E.; Boni, R.; Boscolo, M.; Demma, T.; Drago, A.; Guiducci, S. et al.
System: The UNT Digital Library
Detection of adventitious viruses from biologicals using a broad spectrum Microbial Detection Array (open access)

Detection of adventitious viruses from biologicals using a broad spectrum Microbial Detection Array

None
Date: May 24, 2011
Creator: Jaing, C; Gardner, S; McLoughlin, K; Thissen, J & Slezak, T
System: The UNT Digital Library
Developing State and National Evaluation Infrastructures- Guidance for the Challenges and Opportunities of EM&V (open access)

Developing State and National Evaluation Infrastructures- Guidance for the Challenges and Opportunities of EM&V

Evaluating the impacts and effectiveness of energy efficiency programs is likely to become increasingly important for state policymakers and program administrators given legislative mandates and regulatory goals and increasing reliance on energy efficiency as a resource. In this paper, we summarize three activities that the authors have conducted that highlight the expanded role of evaluation, measurement and verification (EM&V): a study that identified and analyzed challenges in improving and scaling up EM&V activities; a scoping study that identified issues involved in developing a national efficiency EM&V standard; and lessons learned from providing technical assistance on EM&V issues to states that are ramping up energy efficiency programs. The lessons learned are summarized in 13 EM&V issues that policy makers should address in each jurisdiction and which are listed and briefly described. The paper also discusses how improving the effectiveness and reliability of EM&V will require additional capacity building, better access to existing EM&V resources, new methods to address emerging issues and technologies, and perhaps foundational documents and approaches to improving the credibility and cross jurisdictional comparability of efficiency investments. Two of the potential foundational documents discussed are a national EM&V standard or resource guide and regional deemed savings and algorithm databases.
Date: June 24, 2011
Creator: Schiller, Steven R. & Goldman, Charles A.
System: The UNT Digital Library
Development of a Microchannel Plate-Based Gated X-ray Imager for Imaging and Spectroscopy Experiments on Z (open access)

Development of a Microchannel Plate-Based Gated X-ray Imager for Imaging and Spectroscopy Experiments on Z

This poster describes a microchannelplate (MCP)–based, gated x-ray imager developed by National Security Technologies, LLC (NSTec), and Sandia National Laboratories(SNL) over the past several years. The camera consists of a 40 mm × 40 mm MCP, coated with eight 4 mm wide microstrips. The camera is gated by sending subnanosecond high-voltage pulses across the striplines. We have performed an extensive characterization of the camera, the results of which we present here. The camera has an optical gate profile width (time resolution) as narrow as 150 ps and detector uniformity of better than 30% along the length of a strip, far superior than what was achieved in previous designs. The spatial resolution is on the order of 40 microns for imaging applications and a dynamic range of between ~100 and ~1000. We also present results from a Monte Carlo simulation code developed by NSTec over the last several years. Agreement between the simulation results and the experimental measurements is very good.
Date: June 24, 2011
Creator: Wu, M.; Kruschwitz, C. A.; Tibbitts, A. & Rochau, G.
System: The UNT Digital Library
DOE/NNSA Aerial Measuring System (AMS): Flying the 'Real' Thing (open access)

DOE/NNSA Aerial Measuring System (AMS): Flying the 'Real' Thing

This slide show documents aerial radiation surveys over Japan. Map product is a compilation of daily aerial measuring system missions from the Fukushima Daiichi power plant to 80 km radius. In addition, other flights were conducted over US military bases and the US embassy.
Date: June 24, 2011
Creator: Lyons, Craig
System: The UNT Digital Library
Emergence of the Persistent Spin Helix in Semiconductor Quantum Wells (open access)

Emergence of the Persistent Spin Helix in Semiconductor Quantum Wells

According to Noether's theorem, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with respect to rotation of the electron's spin, or SU(2) symmetry, leads to conservation of spin polarization. For electrons in a solid, this symmetry is ordinarily broken by spin-orbit (SO) coupling, allowing spin angular momentum to flow to orbital angular momentum. However, it has recently been predicted that SU(2) can be recovered in a two-dimensional electron gas (2DEG), despite the presence of SO coupling. The corresponding conserved quantities include the amplitude and phase of a helical spin density wave termed the 'persistent spin helix' (PSH). SU(2) is restored, in principle, when the strength of two dominant SO interactions, the Rashba ({alpha}) and linear Dresselhaus ({beta}{sub 1}), are equal. This symmetry is predicted to be robust against all forms of spin-independent scattering, including electron-electron interactions, but is broken by the cubic Dresselhaus term ({beta}{sub 3}) and spin-dependent scattering. When these terms are negligible, the distance over which spin information can propagate is predicted to diverge as {alpha} {yields} {beta}{sub 1}. Here we observe experimentally the emergence of the …
Date: August 24, 2011
Creator: Koralek, Jake; Weber, Chris; Orenstein, Joe; Bernevig, Andrei; Zhang, Shoucheng; Mack, Shawn et al.
System: The UNT Digital Library
Engineering Prototype for a Compact Medical Dielectric Wall Accelerator (open access)

Engineering Prototype for a Compact Medical Dielectric Wall Accelerator

None
Date: August 24, 2011
Creator: Zografos, A.; Hening, A.; Joshkin, V.; Leung, K.; Pearson, D.; Pearce-Percy, H. et al.
System: The UNT Digital Library
Fast Camera Imaging of Hall Thruster Ignition (open access)

Fast Camera Imaging of Hall Thruster Ignition

Hall thrusters provide efficient space propulsion by electrostatic acceleration of ions. Rotating electron clouds in the thruster overcome the space charge limitations of other methods. Images of the thruster startup, taken with a fast camera, reveal a bright ionization period which settles into steady state operation over 50 μs. The cathode introduces azimuthal asymmetry, which persists for about 30 μs into the ignition. Plasma thrusters are used on satellites for repositioning, orbit correction and drag compensation. The advantage of plasma thrusters over conventional chemical thrusters is that the exhaust energies are not limited by chemical energy to about an electron volt. For xenon Hall thrusters, the ion exhaust velocity can be 15-20 km/s, compared to 5 km/s for a typical chemical thruster
Date: February 24, 2011
Creator: Ellison, C. L.; Raitses, Y. & Fisch, N. J.
System: The UNT Digital Library
Future directions of accelerator-based NP and HEP facilities (open access)

Future directions of accelerator-based NP and HEP facilities

Progress in particle and nuclear physics has been closely connected to the progress in accelerator technologies - a connection that is highly beneficial to both fields. This paper presents a review of the present and future facilities and accelerator technologies that will push the frontiers of high-energy particle interactions and high intensity secondary particle beams.
Date: July 24, 2011
Creator: Roser, T.
System: The UNT Digital Library
Gluon Saturation in QCD at High Energy: Beyond Leading Logarithms (open access)

Gluon Saturation in QCD at High Energy: Beyond Leading Logarithms

Progresses towards the calculation and the understanding of NLO/NLL contributions to Deep Inelastic Scattering at low x with gluon saturation are being reviewed.
Date: July 24, 2011
Creator: G., Beuf
System: The UNT Digital Library
H-CANYON AIR EXHAUST TUNNEL INSPECTION VEHICLE DEVELOPMENT (open access)

H-CANYON AIR EXHAUST TUNNEL INSPECTION VEHICLE DEVELOPMENT

The H-Canyon at Savannah River Site is a large concrete structure designed for chemical separation processes of radioactive material. The facility requires a large ventilation system to maintain negative pressure in process areas for radioactive contamination control and personnel protection. The ventilation exhaust is directed through a concrete tunnel under the facility which is approximately five feet wide and 8 feet tall that leads to a sand filter and stack. Acidic vapors in the exhaust have had a degrading effect on the surface of the concrete tunnels. Some areas have been inspected; however, the condition of other areas is unknown. Experience from historical inspections with remote controlled vehicles will be discussed along with the current challenge of inspecting levels below available access points. The area of interest in the exhaust tunnel must be accessed through a 14 X 14 inch concrete plug in the floor of the hot gang valve corridor. The purpose for the inspection is to determine the condition of the inside of the air tunnel and establish if there are any structural concerns. Various landmarks, pipe hangers and exposed rebar are used as reference points for the structural engineers when evaluating the current integrity of the air …
Date: May 24, 2011
Creator: Minichan, R.; Fogle, R. & Marzolf, A.
System: The UNT Digital Library
In Situ X-Ray Probing Reveals Fingerprints of Surface Platinum Oxide (open access)

In Situ X-Ray Probing Reveals Fingerprints of Surface Platinum Oxide

In situ x-ray absorption spectroscopy (XAS) at the Pt L{sub 3} edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard x-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF8 code and complementary extended x-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.
Date: August 24, 2011
Creator: Friebel, Daniel
System: The UNT Digital Library
Laboratory Experiments Bearing on the Origin and Evolution of Olivine-rich Chondrules (open access)

Laboratory Experiments Bearing on the Origin and Evolution of Olivine-rich Chondrules

Evaporation rates of K2O, Na2O, and FeO from chondrule-like liquids and the associated potassium isotopic fractionation of the evaporation residues were measured to help understand the processes and conditions that affected the chemical and isotopic compositions of olivine-rich Type IA and Type IIA chondrules from Semarkona. Both types of chondrules show evidence of having been significantly or totally molten. However, these chondrules do not have large or systematic potassium isotopic fractionation of the sort found in the laboratory evaporation experiments. The experimental results reported here provide new data regarding the evaporation kinetics of sodium and potassium from a chondrule-like melt and the potassium isotopic fractionation of evaporation residues run under various conditions ranging from high vacuum to pressures of one bar of H2+CO2, or H2, or helium. The lack of systematic isotopic fractionation of potassium in the Type IIA and Type IA chondrules compared with what is found in the vacuum and one-bar evaporation residues is interpreted as indicating that they evolved in a partially closed system where the residence time of the surrounding gas was sufficiently long for it to have become saturated in the evaporating species and for isotopic equilibration between the gas and the melt. A diffusion …
Date: June 24, 2011
Creator: Richter, Frank M.; Mendybaev, Ruslan A.; Christensen, John N.; Ebel, Denton & Gaffney, Amy
System: The UNT Digital Library
Limits on the use of Nuclear Explosives for Asteroid Deflection (open access)

Limits on the use of Nuclear Explosives for Asteroid Deflection

None
Date: May 24, 2011
Creator: Dearborn, D S & Bruck, M
System: The UNT Digital Library
MGA++ Studies of U/Pu Gamma-ray Standards with two Falcon 5000 Mechanical cooled HPGe Detection Systems (open access)

MGA++ Studies of U/Pu Gamma-ray Standards with two Falcon 5000 Mechanical cooled HPGe Detection Systems

None
Date: May 24, 2011
Creator: Wang, T. F.
System: The UNT Digital Library
Modeling Personalized Email Prioritization: Classification-based and Regression-based Approaches (open access)

Modeling Personalized Email Prioritization: Classification-based and Regression-based Approaches

Email overload, even after spam filtering, presents a serious productivity challenge for busy professionals and executives. One solution is automated prioritization of incoming emails to ensure the most important are read and processed quickly, while others are processed later as/if time permits in declining priority levels. This paper presents a study of machine learning approaches to email prioritization into discrete levels, comparing ordinal regression versus classier cascades. Given the ordinal nature of discrete email priority levels, SVM ordinal regression would be expected to perform well, but surprisingly a cascade of SVM classifiers significantly outperforms ordinal regression for email prioritization. In contrast, SVM regression performs well -- better than classifiers -- on selected UCI data sets. This unexpected performance inversion is analyzed and results are presented, providing core functionality for email prioritization systems.
Date: October 24, 2011
Creator: Yoo, S.; Yang, Y. & Carbonell, J.
System: The UNT Digital Library