A 4 to 0.1 nm FEL Based on the SLAC Linac (open access)

A 4 to 0.1 nm FEL Based on the SLAC Linac

The author show that using existing electron gun technology and a high energy linac like the one at SLAC, it is possible to build a Free Electron Laser operating around the 4 nm water window. A modest improvement in the gun performance would further allow to extend the FEL to the 0.1 nm region. Such a system would produce radiation with a brightness many order of magnitude above that of any synchrotron radiation source, existing or under construction, with laser power in the multigawatt region and subpicosecond pulse length.
Date: June 5, 2012
Creator: Pellegrini, C.
Object Type: Article
System: The UNT Digital Library
Effect of SOFC Interconnect-Coating Interactions on Coating Properties and Performance (open access)

Effect of SOFC Interconnect-Coating Interactions on Coating Properties and Performance

The high operating temperature of solid oxide fuel cells (SOFCs) provides good fuel flexibility which expands potential applications, but also creates materials challenges. One such challenge is the interconnect material, which was the focus of this project. In particular, the objective of the project was to understand the interaction between the interconnect alloy and ceramic coatings which are needed to minimize chromium volatilization and the associated chromium poisoning of the SOFC cathode. This project focused on coatings based on manganese cobalt oxide spinel phases (Mn,Co)3O4, which have been shown to be effective as coatings for ferritic stainless steel alloys. Analysis of diffusion couples was used to develop a model to describe the interaction between (Mn,Co)3O4 and Cr2O3 in which a two-layer reaction zone is formed. Both layers form the spinel structure, but the concentration gradients at the interface appear like a two-phase boundary suggesting that a miscibility gap is present in the spinel solid solution. A high-chromium spinel layer forms in contact with Cr2O3 and grows by diffusion of manganese and cobalt from the coating material to the Cr2O3. The effect of coating composition, including the addition of dopants, was evaluated and indicated that the reaction rate could be decreased …
Date: September 5, 2012
Creator: Fergus, Jeffrey W.
Object Type: Report
System: The UNT Digital Library
Pacific Northwest National Laboratory Potential Impact Categories for Radiological Air Emission Monitoring (open access)

Pacific Northwest National Laboratory Potential Impact Categories for Radiological Air Emission Monitoring

In 2002, the EPA amended 40 CFR 61 Subpart H and 40 CFR 61 Appendix B Method 114 to include requirements from ANSI/HPS N13.1-1999 Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stack and Ducts of Nuclear Facilities for major emission points. Additionally, the WDOH amended the Washington Administrative Code (WAC) 246-247 Radiation protection-air emissions to include ANSI/HPS N13.1-1999 requirements for major and minor emission points when new permitting actions are approved. A result of the amended regulations is the requirement to prepare a written technical basis for the radiological air emission sampling and monitoring program. A key component of the technical basis is the Potential Impact Category (PIC) assigned to an emission point. This paper discusses the PIC assignments for the Pacific Northwest National Laboratory (PNNL) Integrated Laboratory emission units; this revision includes five PIC categories.
Date: June 5, 2012
Creator: Ballinger, Marcel Y.; Gervais, Todd L. & Barnett, J. M.
Object Type: Report
System: The UNT Digital Library
Final Technical Report - Integrated Hydrogeophysical and Hydrogeologic Driven Parameter Upscaling for Dual-Domain Transport Modeling (open access)

Final Technical Report - Integrated Hydrogeophysical and Hydrogeologic Driven Parameter Upscaling for Dual-Domain Transport Modeling

The three major components of this research were: 1. Application of minimally invasive, cost effective hydrogeophysical techniques (surface and borehole), to generate fine scale (~1m or less) 3D estimates of subsurface heterogeneity. Heterogeneity is defined as spatial variability in hydraulic conductivity and/or hydrolithologic zones. 2. Integration of the fine scale characterization of hydrogeologic parameters with the hydrogeologic facies to upscale the finer scale assessment of heterogeneity to field scale. 3. Determination of the relationship between dual-domain parameters and practical characterization data.
Date: November 5, 2012
Creator: Shafer, John M
Object Type: Report
System: The UNT Digital Library
Two- and Three-Body Charmless B Decays at BaBar (open access)

Two- and Three-Body Charmless B Decays at BaBar

We report recent measurements of rare charmless B decays performed by BaBar. The results are based on the final BaBar dataset of 424 fb{sup -1} collected at the PEP-II B-factory based at the SLAC National Accelerator Laboratory. The study of rare B decays is a key ingredient to meet two of the main goals of the B-factories: assessing the validity of the Cabibbo-Kobayashi-Maskawa (CKM) picture of CP-violation by precisely measuring the elements of the Unitarity Triangle (UT), and searching for hints of New Physics (NP), or otherwise constraining NP scenarios, in processes which are suppressed in the Standard Model (SM). In loop processes, in particular, NP at some higher energy scale may manifest itself in the low energy effective theory as new couplings, such as those introduced by new very massive virtual particles in the loop. In NP searches hadronic uncertainties can play a major role, expecially for branching fraction measurements. Many theoretical uncertainties cancel in ratios of amplitudes, and most NP probes are therefore of this kind. In the following sections we report recent measurements, performed by the BaBar Collaboration, that are relevant to NP searches in charmless hadronic B decays.
Date: April 5, 2012
Creator: Stracka, Simone
Object Type: Article
System: The UNT Digital Library
Change Management Project award submission (open access)

Change Management Project award submission

None
Date: December 5, 2012
Creator: Teslich, R
Object Type: Article
System: The UNT Digital Library
Long-Term Colloid Mobilization And Colloid-Facilitated Transport Of Radionuclides In A Semi-Arid Vadose Zone (open access)

Long-Term Colloid Mobilization And Colloid-Facilitated Transport Of Radionuclides In A Semi-Arid Vadose Zone

The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclide transport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigations of single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a …
Date: November 5, 2012
Creator: Flury, Markus; Harsh, James B; Zhang, Fred; Gee, Glendon W; Mattson, Earl D & Lichtner, Peter C
Object Type: Text
System: The UNT Digital Library
The suppression of magnetism and the development of superconductivity within the collapsed tetragonal phase of Ca0.67Sr0.33Fe2As2 at high pressure (open access)

The suppression of magnetism and the development of superconductivity within the collapsed tetragonal phase of Ca0.67Sr0.33Fe2As2 at high pressure

None
Date: March 5, 2012
Creator: Jeffries, J R; Butch, N P; Kirshenbaum, K; Saha, S R; Weir, S T; Vohra, Y K et al.
Object Type: Article
System: The UNT Digital Library
A Multigrid-in-Time Algorithm for Solving Evolution Equations in Parallel (open access)

A Multigrid-in-Time Algorithm for Solving Evolution Equations in Parallel

None
Date: December 5, 2012
Creator: Friedhoff, S; Falgout, R D; Kolev, T V; MacLachlan, S & Schroder, J B
Object Type: Article
System: The UNT Digital Library
Re-architecting TEIMS Web-based Legacy Applications Using the Model View Controller Paradigm (open access)

Re-architecting TEIMS Web-based Legacy Applications Using the Model View Controller Paradigm

None
Date: September 5, 2012
Creator: Barbosa, E & Laguna, G W
Object Type: Article
System: The UNT Digital Library
Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport (open access)

Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, partial pressure of carbon dioxide, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. In this final report, we provide detailed descriptions of our results from this three-year study, completed in 2012 following a one-year no cost extension.
Date: November 5, 2012
Creator: Chorover, Jon; Perdrial, Nico; Mueller, Karl; Strepka, Caleb; O’Day, Peggy; Rivera, Nelson et al.
Object Type: Report
System: The UNT Digital Library
Ab-initio calculation of optical properties of wurtzitic In_x Ga_1x N and In_x Al_1x N alloys including excitonic effects (open access)

Ab-initio calculation of optical properties of wurtzitic In_x Ga_1x N and In_x Al_1x N alloys including excitonic effects

None
Date: September 5, 2012
Creator: de Carvalho, L C; Schleife, A; Furthmueller, J & Bechstedt, F
Object Type: Article
System: The UNT Digital Library
Search for a Low-Mass Higgs Boson (A0) at BaBar (open access)

Search for a Low-Mass Higgs Boson (A0) at BaBar

The BABAR Collaboration has performed three searches for a light Higgs boson, A{sup 0}, in radiative Upsilon ({Upsilon}) decays: {Upsilon}(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {tau}{sup +}{tau}{sup -}; {Upsilon}(nS) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {mu}{sup +}{mu}{sup -} (n = 2,3); and {Upsilon}(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} invisible. Such a Higgs boson (A{sup 0}) appears in the Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson couples strongly to b-quarks. The searches are based on data samples that consist of 122 x 10{sup 6} {Upsilon}(3S) and 99 x 10{sup 6} {Upsilon}(2S) decays, collected by the BABAR detector at the SLAC National Accelerator Laboratory. The searches reveal no evidence for an A{sup 0}, and product of branching fractions upper limits, at 90% C.L., of (1.5-16) x 10{sup -5}, (0.44-44) x 10{sup -6}, and (0.7-31) x 10{sup -6} were obtained for these searches, respectively. Also, we set the upper limits {Beta}({eta}{sub b} {yields} {tau}{sup +}{tau}{sup -}) < 8% and {Beta}({eta}{sub b} {yields} {mu}{sup +}{mu}{sup -}) < 0.9%.
Date: April 5, 2012
Creator: Mokhtar, Arafat Gabareen
Object Type: Article
System: The UNT Digital Library
Electron Transport Studies of Annular Exploders (open access)

Electron Transport Studies of Annular Exploders

None
Date: November 5, 2012
Creator: Strozzi, D. J.; Tabak, M.; Shay, H. D. & Larson, D. J.
Object Type: Article
System: The UNT Digital Library
High Cost/High Risk Components to Chalcogenide Molded Lens Model: Molding Preforms and Mold Technology (open access)

High Cost/High Risk Components to Chalcogenide Molded Lens Model: Molding Preforms and Mold Technology

This brief report contains a critique of two key components of FiveFocal's cost model for glass compression molding of chalcogenide lenses for infrared applications. Molding preforms and mold technology have the greatest influence on the ultimate cost of the product and help determine the volumes needed to select glass molding over conventional single-point diamond turning or grinding and polishing. This brief report highlights key areas of both technologies with recommendations for further study.
Date: October 5, 2012
Creator: Bernacki, Bruce E.
Object Type: Report
System: The UNT Digital Library
Towards Recovering Provenance with Experiment Explorer (open access)

Towards Recovering Provenance with Experiment Explorer

None
Date: October 5, 2012
Creator: Davis, D. B.; Asuncion, H. U.; Abdulla, G. M. & Carr, C. W.
Object Type: Article
System: The UNT Digital Library
Compressing Phasor Measurement Data (open access)

Compressing Phasor Measurement Data

None
Date: December 5, 2012
Creator: Top, P. & Breneman, J.
Object Type: Article
System: The UNT Digital Library
Observation of Laser Induced Magnetization Dynamics in Co/Pd Multilayers with Coherent X-ray Scattering (open access)

Observation of Laser Induced Magnetization Dynamics in Co/Pd Multilayers with Coherent X-ray Scattering

We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.
Date: April 5, 2012
Creator: Wu, Benny
Object Type: Article
System: The UNT Digital Library
ENERGY PARTITIONING, ENERGY COUPLING (EPEC) EXPERIMENTS AT THE NATIONAL IGNITION FACILITY (open access)

ENERGY PARTITIONING, ENERGY COUPLING (EPEC) EXPERIMENTS AT THE NATIONAL IGNITION FACILITY

The energy-partitioning, energy-coupling (EPEC) experiments at the National Ignition Facility (NIF) will simultaneously measure the coupling of energy into both ground shock and air-blast overpressure from a laser-driven target. The source target for the experiment is positioned at a known height above the ground-surface simulant and is heated by four beams from NIF. The resulting target energy density and specific energy are equal to those of a low-yield nuclear device. The ground-shock stress waves and atmospheric overpressure waveforms that result in our test system are hydrodynamically scaled analogs of seismic and air-blast phenomena caused by a nuclear weapon. In what follows, we discuss the motivation for our investigation and briefly describe NIF. Then, we introduce the EPEC experiments, including diagnostics, in more detail.
Date: January 5, 2012
Creator: Fournier, K B; Brown, C G; May, M J; Dunlop, W H; Compton, S M; Kane, J O et al.
Object Type: Report
System: The UNT Digital Library
Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2) (open access)

Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2)

The Department of Energy’s High Temperature, Low Relative Humidity Membrane Program was begun in 2006 with the Florida Solar Energy Center (FSEC) as the lead organization. During the first three years of the program, FSEC was tasked with developing non-Nafion® proton exchange membranes with improved conductivity for fuel cells. Additionally, FSEC was responsible for developing protocols for the measurement of in-plane conductivity, providing conductivity measurements for the other funded teams, developing a method for through-plane conductivity and organizing and holding semiannual meetings of the High Temperature Membrane Working Group (HTMWG). The FSEC membrane research focused on the development of supported poly[perfluorosulfonic acid] (PFSA) – Teflon membranes and a hydrocarbon membrane, sulfonated poly(ether ether ketone). The fourth generation of the PFSA membrane (designated FSEC-4) came close to, but did not meet, the Go/No-Go milestone of 0.1 S/cm at 50% relative humidity at 120 °C. In-plane conductivity of membranes provided by the funded teams was measured and reported to the teams and DOE. Late in the third year of the program, DOE used this data and other factors to decide upon the teams to continue in the program. The teams that continued provided promising membranes to FSEC for development of membrane electrode …
Date: September 5, 2012
Creator: Fenton, James; Slattery, Darlene & Mohajeri, Nahid
Object Type: Report
System: The UNT Digital Library
The Injection System of the INFN-SuperB Factory Project: Preliminary Design (open access)

The Injection System of the INFN-SuperB Factory Project: Preliminary Design

The ultra high luminosity B-factory (SuperB) project of INFN requires a high performance and reliable injection system, providing electrons at 4 GeV and positrons at 7 GeV, to fulfil the very tight requirements of the collider. Due to the short beam lifetime, continuous injection of electron and positron bunches in both LER and HER rings is necessary to maintain an high average luminosity. Polarized electrons are required for experiments and must be delivered by the injection system, due to the beam lifetime shorter than the ring polarization build-up: they will be produced by means of a SLAC-SLC polarized gun. The emittance and the energy spread of the e{sup -}/e{sup +} beams are reduced in a 1 GeV Damping Ring (DR) before injection in the main rings. Two schemes for positron production are under study, one with e{sup -}/e{sup +} conversion at low energy (< 1 Gev) and one with conversion at 6 GeV and a recirculation line to bring the positrons back to the DR. Acceleration through the Linac is provided by a 2856 MHz RF system made of travelling wave (TW), room temperature accelerating structures.
Date: July 5, 2012
Creator: Boni, Roberto; Guiducci, Susanna; Preger, Miro; Raimondi, Pantaleo; Chance, Antoine; Dadoun, Olivier et al.
Object Type: Article
System: The UNT Digital Library
Gauge Properties Of The Guiding Center Variational Symplectic Integrator (open access)

Gauge Properties Of The Guiding Center Variational Symplectic Integrator

Recently, variational symplectic algorithms have been developed for the long-time simulation of charged particles in magnetic fields1-3. As a direct consequence of their derivation from a discrete variational principle, these algorithms have very good long-time energy conservation, as well as exactly preserving discrete momenta. We present stability results for these algorithms, focusing on understanding how explicit variational integrators can be designed for this type of system. It is found that for explicit algorithms an instability arises because the discrete symplectic structure does not become the continuous structure in the t → 0 limit. We examine how a generalized gauge transformation can be used to put the Lagrangian in the "antisymmetric discretization gauge," in which the discrete symplectic structure has the correct form, thus eliminating the numerical instability. Finally, it is noted that the variational guiding center algorithms are not electromagnetically gauge invariant. By designing a model discrete Lagrangian, we show that the algorithms are approximately gauge invariant as long as A and #30; are relatively smooth. A gauge invariant discrete Lagrangian is very important in a variational particle-in-cell algorithm where it ensures current continuity and preservation of Gauss's law4.
Date: March 5, 2012
Creator: J. Squire, H. Qin and W. Tang
Object Type: Report
System: The UNT Digital Library
Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime (open access)

Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime

A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for three years. The major outcome has been the demonstration of stable 100 MV/m gradient operation of a number of CLIC prototype structures. These structures were fabricated using the technology developed from 1994 to 2004 for the GLC/NLC linear collider initiative. One of the goals has been to refine the essential parameters and fabrication procedures needed to realize such a high gradient routinely. Another goal has been to develop structures with stronger dipole mode damping than those for GLC/NLC. The latter requires that the surface temperature rise during the pulse be higher, which may increase the breakdown rate. One structure with heavy damping has been RF processed and another is nearly finished. The breakdown rates of these structures were found to be higher by two orders of magnitude compared to those with equivalent acceleration mode parameters but without the damping features. This paper presents these results together with some of the earlier results from non-damped structures.
Date: July 5, 2012
Creator: Higo, Toshiyasu; Higashi, Yasuo; Matsumoto, Shuji; Yokoyama, Kazue; Adolphsen, Chris; Dolgashev, Valery et al.
Object Type: Article
System: The UNT Digital Library
Discovery of Very High Energy Gamma Rays from PKS 1424+240 and Multiwavelength Constraints on its Redshift (open access)

Discovery of Very High Energy Gamma Rays from PKS 1424+240 and Multiwavelength Constraints on its Redshift

We report the first detection of very-high-energy (VHE) gamma-ray emission above 140GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140GeV measured by VERITAS is well described by a power law with a photon index of 3.8 {+-}0.5{sub stat} {+-} 0.3{sub syst} and a flux normalization at 200 GeV of (5.1 {+-} 0.9{sub stat} {+-} 0.5{sub syst}) x 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1}, where stat and syst denote the statistical and systematical uncertainty, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (2009 February 19 to June 21). Flux variability is also not observed in contemporaneous high energy observations with the Fermi Large Area Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from the Swift XRT and MDM observatory, respectively. The broadband spectral energy distribution (SED) is well described by a one-zone synchrotron self-Compton (SSC) model favoring a redshift of less than 0.1. Using the photon index measured with Fermi in combination with recent extragalactic background light (EBL) absorption models it can be concluded from the VERITAS data that the redshift of PKS 1424+240 is less than 0.66.
Date: April 5, 2012
Creator: Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M. et al.
Object Type: Report
System: The UNT Digital Library