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Local Structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies (open access)

Local Structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies

The combined local structure techniques, extended x-ray absorption fine structure (EXAFS) and neutron pair distribution function analysis, have been used for temperatures 4<= T<= 330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1?xSrxCoO3 for a significant fraction of Co sites (x<= 0.35), indicating few, if any, JT-active, singly occupied eg Co sites exist.
Date: January 26, 2009
Creator: Sundaram, N.; Jiang, Y.; Anderson, I. E.; Belanger, D. P.; Booth, C. H.; Bridges, F. et al.
System: The UNT Digital Library
Dalitz Plot Analysis of Ds+->pi+pi-pi+ (open access)

Dalitz Plot Analysis of Ds+->pi+pi-pi+

A Dalitz plot analysis of {approx} 13, 000 D{sub s}{sup +} decays to {pi}{sup +}{pi}{sup +}{pi}{sup -} has been performed. A 384 fb{sup -1} data sample, recorded by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring running at center of mass energies near 10.6 GeV, is used. Amplitudes and phases of the intermediate resonances which contribute to this final state are measured. A high precision measurement of the ratio: {Beta}(D{sub s}{sup +} {yields} {pi}{sup +}{pi}{sup +}{pi}{sup -})/{Beta}(D{sub s}{sup +} {yields} K{sup +}K{sup -}{pi}{sup +}) = 0.199 {+-} 0.004 {+-} 0.006 is performed. Using a model independent partial wave analysis the amplitude and phase of the S-wave have been measured.
Date: January 26, 2009
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
AAAR 28th Annual Conference Symposia Focusing on Topics of Interest to the U.S. DOE Atmospheric Science Program - October 26-30, 2009 (open access)

AAAR 28th Annual Conference Symposia Focusing on Topics of Interest to the U.S. DOE Atmospheric Science Program - October 26-30, 2009

This report addresses the secondary aerosol is an important component of atmospheric fine particles that generally consists of organics, sulfates, and nitrates.
Date: October 26, 2009
Creator: Ziemann, Paul
System: The UNT Digital Library
Analysis of High-Te Plasmas Heated by HHFW in NSTX (open access)

Analysis of High-Te Plasmas Heated by HHFW in NSTX

The implementation in TRANSP of a recent version of TORIC capable of calculating power deposition for HHFW conditions is used to analyze NSTX plasma under different operating conditions. The power deposition profile into the electrons is obtained for high-Te conditions - Te ≤ 5keV - obtained in He and D plasmas with ITB. HHFW heating of NBI-induced H-mode plasmas is discussed. At the RF onset the RF power is divided evenly between the electrons and the fast particles, but as the latter thermalize and the electron density increases, the HHFW power repartition shifts progressively toward the electrons. Power deposition profiles for the electrons and for the fast particles are shown.
Date: June 26, 2009
Creator: LeBlanc, P.; Bell, R. E.; Bonoli, P.; Hosea, J. C.; Mazzucato, E.; Phillips, C. K. et al.
System: The UNT Digital Library
Simulation Results for the New NSTX HHFW Antenna Straps Design by Using Microwave Studio (open access)

Simulation Results for the New NSTX HHFW Antenna Straps Design by Using Microwave Studio

Experimental results have shown that the high harmonic fast wave (HHFW) at 30 MHz can provide substantial plasma heating and current drive for the NSTX spherical tokamak operation. However, the present antenna strap design rarely achieves the design goal of delivering the full transmitter capability of 6 MW to the plasma. In order to deliver more power to the plasma, a new antenna strap design and the associated coaxial line feeds are being constructed. This new antenna strap design features two feedthroughs to replace the old single feed-through design. In the design process, CST Microwave Studio has been used to simulate the entire new antenna strap structure including the enclosure and the Faraday shield. In this paper, the antenna strap model and the simulation results will be discussed in detail. The test results from the new antenna straps with their associated resonant loops will be presented as well.
Date: May 26, 2009
Creator: Kung, C. C.; Brunkhorst, C.; Greenough, N.; Fredd, E.; Castano, A.; Miller, D. et al.
System: The UNT Digital Library
Time-dependent amplitude analysis of $B^0 \to K^0_S\pi^ pi^-$ (open access)

Time-dependent amplitude analysis of $B^0 \to K^0_S\pi^ pi^-$

In this paper we present results from a time-dependent amplitude analysis of the B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decay. In Sec. II we describe the time-dependent DP formalism, and introduce the signal parameters that are extracted in the fit to data. In Sec. III we briefly describe the BABAR detector and the data set. In Sec. IV, we explain the selection requirements used to obtain the signal candidates and suppress backgrounds. In Sec. V we describe the fit method and the approach used to control experimental effects such as resolution. In Sec. VI we present the results of the fit, and extract parameters relevant to the contributing intermediate resonant states. In Sec. VII we discuss systematic uncertainties in the results, and finally we summarize the results in Sec. VIII.
Date: May 26, 2009
Creator: Aubert, B.
System: The UNT Digital Library
800MHz Crab Cavity Conceptual Design For the LHC Upgrade (open access)

800MHz Crab Cavity Conceptual Design For the LHC Upgrade

In this paper, we present an 800 MHz crab cavity conceptual design for the LHC upgrade. The cell shape is optimized for lower maximum peak surface fields as well as higher transverse R/Q. A compact coax-to-coax coupler scheme is proposed to damp the LOM/SOM modes. A two-stub antenna with a notch filter is used as the HOM coupler to damp the HOM modes in the horizontal plane and rejects the operating mode at 800MHz. Multipacting (MP) simulations show that there are strong MP particles at the disks. Adding grooves along the short axis without changing the operating mode's RF characteristics can suppress the MP activities. Possible input coupler configurations are discussed.
Date: May 26, 2009
Creator: Xiao, Liling; Li, Zenghai; Ng, Cho-Kuen; Seryi, Andrei & /SLAC
System: The UNT Digital Library
Tolerance Study for the Echo-Enabled Harmonic Generation Free Electron Laser (open access)

Tolerance Study for the Echo-Enabled Harmonic Generation Free Electron Laser

The echo-enabled harmonic generation free electron laser (EEHG FEL) holds great promise in generation of coherent soft x-ray directly from a UV seed laser within one stage. The density modulation in the harmonic generation process is affected by the smearing effect caused by the fluctuations of energy and current along the beam, as well as the field error of the dispersive elements. In this paper we study the tolerance of the EEHG FEL on beam quality and field quality. The diffusion effect from incoherent synchrotron radiation (ISR) in the dispersion sections and the second modulator are also studied.
Date: May 26, 2009
Creator: Xiang, D. & Stupakov, G.
System: The UNT Digital Library
Future BNL plans for a polarized electron-ion collider (eRHIC) (open access)

Future BNL plans for a polarized electron-ion collider (eRHIC)

To provide polarized electron-proton collisions of {radical}s = 100 GeV; addition of a 10 GeV electron accelerator to the existing RHIC facility is currently under study. Two design lines are under consideration: a self-polarizing electron ring, and an energy recovery linac. While the latter provides significantly higher luminosities, it is technologically very challenging. We present both design approaches and discuss their advantages and limitations.
Date: July 26, 2009
Creator: Montag, C.
System: The UNT Digital Library
Optimal Technology Investment and Operation in Zero-Net-Energy Buildings with Demand Response (open access)

Optimal Technology Investment and Operation in Zero-Net-Energy Buildings with Demand Response

The US Department of Energy has launched the Zero-Net-Energy (ZNE) Commercial Building Initiative (CBI) in order to develop commercial buildings that produce as much energy as they use. Its objective is to make these buildings marketable by 2025 such that they minimize their energy use through cutting-edge energy-efficient technologies and meet their remaining energy needs through on-site renewable energy generation. We examine how such buildings may be implemented within the context of a cost- or carbon-minimizing microgrid that is able to adopt and operate various technologies, such as photovoltaic (PV) on-site generation, heat exchangers, solar thermal collectors, absorption chillers, and passive / demand-response technologies. We use a mixed-integer linear program (MILP) that has a multi-criteria objective function: the minimization of a weighted average of the building's annual energy costs and carbon / CO2 emissions. The MILP's constraints ensure energy balance and capacity limits. In addition, constraining the building's energy consumed to equal its energy exports enables us to explore how energy sales and demand-response measures may enable compliance with the CBI. Using a nursing home in northern California and New York with existing tariff rates and technology data, we find that a ZNE building requires ample PV capacity installed to …
Date: May 26, 2009
Creator: Stadler, Michael; Siddiqui, Afzal; Marnay, Chris; Aki, Hirohisa & Lai, Judy
System: The UNT Digital Library
Reduction of Beam Emittance of Pep-X Using Quadruple Bend Achromat Cell (open access)

Reduction of Beam Emittance of Pep-X Using Quadruple Bend Achromat Cell

SLAC National Accelerator Laboratory is studying an option of building a high brightness synchrotron light source machine, PEP-X, in the existing PEP-II tunnel [1, 2]. By replacing 6 arcs of FODO cells of PEPII High Energy Ring (HER) with two arcs of DBA and four arcs of TME and installation of 89.3 m long damping wiggler an ultra low beam emittance of 0.14 nm-rad (including intra-beam scattering) at 4.5 GeV is achieved. In this paper we study the possibility to further reduce the beam emittance by releasing the constraint of the dispersion free in the DBA straight. The QBA (Quadruple Bend Achromat) cell is used to replace the DBA. The ratio of outer and inner bending angle is optimized. The dispersion function in the non-dispersion straight is controlled to compromise with lower emittance and beam size at the dispersion straight. An undulator of period length 23 mm, maximum magnetic field of 1.053 T, and total periods of 150 is used to put in the 30 straights to simulate the effects of these IDs on the beam emittance and energy spread. The brightness including all the ID effects is calculated and compared to the original PEP-X design.
Date: May 26, 2009
Creator: Wang, Min-Huey; Cai, Yunhai; Hettel, Robert & Nosochkov, Yuri
System: The UNT Digital Library
Collins Mechanism Contributions to Single Spin Asymmetry (open access)

Collins Mechanism Contributions to Single Spin Asymmetry

We present recent developments on the single transverse spin physics, in particular, the Collins mechanism contributions in various hadronic reactions, such as semi-inclusive hadron production in DIS process, azimuthal distribution of hadron in high energy jet in pp collisions. We will demonstrate that the transverse momentum dependent and collinear factorization approaches are consistent with each other in the description of the Collins effects in the semi-inclusive hadron production in DIS process.
Date: May 26, 2009
Creator: Yuan,F.
System: The UNT Digital Library
Microbunching Instability in Velocity Bunching (open access)

Microbunching Instability in Velocity Bunching

Microbunching instability is one of the most challenging threats to FEL performances. The most effective ways to cure the microbunching instability include suppression of the density modulation sources and suppression of the amplification process. In this paper we study the microbunching instability in velocity bunching. Our simulations show that the initial current and energy modulations are suppressed in velocity bunching process, which may be attributed to the strong plasma oscillation and Landau damping from the relatively low beam energy and large relative slice energy spread. A heating effect that may be present in a long solenoid is also preliminarily analyzed.
Date: May 26, 2009
Creator: Xiang, D. & Wu, J.
System: The UNT Digital Library
Recent Improvements in Fast Wave Heating in NSTX (open access)

Recent Improvements in Fast Wave Heating in NSTX

Recent improvements in high-harmonic fast wave (HHFW) core heating in NSTX are attributed to using lithium conditioning, and other wall conditioning techniques, to move the onset density for perpendicular fast wave propagation further from the antenna. This has resulted in the first observation of HHFW core electron heating in deuterium plasma at a launched toroidal wavenumber, kφ = -3 m-1, NSTX record core electron temperatures of 5 keV in helium and deuterium discharges and, for the first time, significant HHFW core electron heating of deuterium neutral-beam-fuelled H-mode plasmas. Also, kφ = -8 m-1 heating of the plasma startup and plasma current ramp-up has resulted in significant core electron heating, even at central electron densities as low as ~ 4x1018 m-3.
Date: June 26, 2009
Creator: G. Taylor, R.E. Bell, R.W. Harvey, J.C. Hosea, E.F. Jaeger, B.P. LeBlanc, C.K. Phillips, P.M. Ryan, E.J. Valeo, J.B. Wilgen, J.R. Wilson, and the NSTX Team
System: The UNT Digital Library
INNOVATIVE APPROACHES TO COMPLYING WITH VERY LOW NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) PERMIT LIMITS FOR METALS (open access)

INNOVATIVE APPROACHES TO COMPLYING WITH VERY LOW NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) PERMIT LIMITS FOR METALS

The NPDES permit issued to the Savannah River Site (SRS) in 2003 contained very low metals limits for several outfalls. Copper, lead and zinc limits were as low as seven micrograms per liter (7 ug/l), 1 ug/l, and 100 ug/l, respectively. The permit contained compliance schedules that provided SRS with only three to five years to select and implement projects that would enable outfall compliance. Discharges from a few outfalls were eliminated or routed into other locations relatively inexpensively. However, some outfall problems were much more difficult to correct. SRS personnel implemented several innovative projects in order to meet compliance schedule deadlines as inexpensively as possible. These innovations included (1) connecting several outfall discharges to the site's Central Sanitary Wastewater Treatment Facility (CSWTF), (2) constructing a treatment wetlands and completing a water-effects ratio (WER) on its effluent, (3) installing a stannous chloride feed system to remove mercury in an existing air stripper, and (4) constructing a humic acid feed system to increase effluent dissolved organic carbon (DOC) content and take advantage of biotic ligand modeling to raise effluent limits.
Date: June 26, 2009
Creator: Payne, B
System: The UNT Digital Library
Hetero-Epitaxial Anion Exchange Yields Single-Crystalline Hollow Nanoparticles (open access)

Hetero-Epitaxial Anion Exchange Yields Single-Crystalline Hollow Nanoparticles

Anion exchange with S was performed on ZnO colloidal nanoparticles. The resulting hollow ZnS nanoparticles are crystal whose shape is dictated by the initial ZnO. Crystallographic and elemental analyses provide insight into the mechanism of the anion exchange.
Date: August 26, 2009
Creator: Park, Jungwon; Zheng, Haimei; Jun, Young-wook & Alivisatos, A. Paul
System: The UNT Digital Library
NAVIGATING A QUALITY ROUTE TO A NATIONAL SAFETY AWARD (open access)

NAVIGATING A QUALITY ROUTE TO A NATIONAL SAFETY AWARD

Deming quality methodologies applied to safety are recognized with the National Safety Council's annual Robert W. Campbell Award. Over the last ten years, the implementation of Statistical Process Control and quality methodologies at the U.S. Department of Energy's Hanford Site have contributed to improved safety. Improvements attributed to Statistical Process Control are evidenced in Occupational Safety and Health records and documented through several articles in Quality Progress and the American Society of Safety Engineers publication, Professional Safety. Statistical trending of safety, quality, and occurrence data continues to playa key role in improving safety and quality at what has been called the world's largest environmental cleanup project. DOE's Hanford Site played a pivotal role in the nation's defense beginning in the 1940s, when it was established as part of the Manhattan Project. After more than 50 years of producing material for nuclear weapons, Hanford, which covers 586 square miles in southeastern Washington state, is now focused on three outcomes: (1) Restoring the Columbia River corridor for multiple uses; (2) Transitioning the central plateau to support long-term waste management; and (3) Putting DOE assets to work for the future. The current environmental cleanup mission faces challenges of overlapping technical, political, regulatory, environmental, …
Date: May 26, 2009
Creator: SS, PREVETTE
System: The UNT Digital Library
On the importance of nuclear quantum motions in near edge x-ray absorption fine structure (NEXAFS) spectroscopy of molecules (open access)

On the importance of nuclear quantum motions in near edge x-ray absorption fine structure (NEXAFS) spectroscopy of molecules

We report the effects of sampling nuclear quantum motion with path integral molecular dynamics (PIMD) on calculations of the nitrogen K-edge spectra of two isolated organic molecules. S-triazine, a prototypical aromatic molecule occupying primarily its vibrational ground state at room temperature, exhibits substantially improved spectral agreement when nuclear quantum effects are included via PIMD, as compared to the spectra obtained from either a single fixed-nuclei based calculation or from a series of configurations extracted from a classical molecular dynamics trajectory. Nuclear quantum dynamics can accurately explain the intrinsic broadening of certain features. Glycine, the simplest amino acid, is problematic due to large spectral variations associated with multiple energetically accessible conformations at the experimental temperature. This work highlights the sensitivity of NEXAFS to quantum nuclear motions in molecules, and the necessity of accurately sampling such quantum motion when simulating their NEXAFS spectra.
Date: February 26, 2009
Creator: Schwartz, Craig P.; Uejio, Janel S.; Saykally, Richard J. & Prendergast, David
System: The UNT Digital Library
Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites (open access)

Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites

Nonlinear-elastic fracture mechanics methods are used to assess the fracture toughness of bulk metallic glass (BMG) composites; results are compared with similar measurements for other monolithic and composite BMG alloys. Mechanistically, plastic shielding gives rise to characteristic resistance?curve behavior where the fracture resistance increases with crack extension. Specifically, confinement of damage by second?phase dendrites is shown to result in enhancement of the toughness by nearly an order of magnitude relative to unreinforced glass.
Date: May 26, 2009
Creator: Launey, Maximilien E.; Hofmann, Douglas C.; Suh, Jin-Yo; Kozachkov, Henry; Johnson, William L. & Ritchie, Robert O.
System: The UNT Digital Library
Collins Fragmentation and the Single Transverse Spin Asymmetry (open access)

Collins Fragmentation and the Single Transverse Spin Asymmetry

We study the Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach. The correspondent twist-three fragmentation function is identified. We show that the Collins function calculated in this approach is universal.We further examine its contribution to the single transverse spin asymmetry of semi-inclusive hadron production in deep inelastic scattering and demonstrate that the transverse momentum dependent and twist-three collinear approaches are consistent in the intermediate transverse momentum region where both apply.
Date: March 26, 2009
Creator: Yuan, Feng & Zhou, Jian
System: The UNT Digital Library
Undulator-Based Production of Polarized Positrons (open access)

Undulator-Based Production of Polarized Positrons

None
Date: May 26, 2009
Creator: Alexander, Gideon; Barley, John; Batygin, Yuri; Berridge, Steven; Bharadwaj, Vinod; Bower, Gary et al.
System: The UNT Digital Library
Start-to-End Simulations of the LCLS Accelerator and FEL Performance at Very Low Charge (open access)

Start-to-End Simulations of the LCLS Accelerator and FEL Performance at Very Low Charge

The Linac Coherent Light Source (LCLS) is an x-ray Free-electron Laser (FEL) being commissioned at Stanford Linear Accelerator Center (SLAC). Recent beam measurements have shown that, using the LCLS injector-linac-compressors, the beam emittance is very small at 20 pC. In this paper we perform start-to-end simulations of the entire accelerator including the FEL undulator and study the FEL performance versus the bunch charge. At 20 pC charge, these calculations associated with the measured beam parameters suggest the possibility of generating a longitudinally coherent single x-ray spike with 2-femtosecond (fs) duration at a wavelength of 1.5 nm. At 100 pC charge level, our simulations show an x-ray pulse with 10 femtosecond duration and up to 10{sup 12} photons at a wavelength of 1.5 {angstrom}. These results open exciting possibilities for ultrafast science and single shot molecular imaging.
Date: May 26, 2009
Creator: Ding, Y; Brachmann, A.; Decker, F. J.; Dowell, D.; Emma, P.; Frisch, J. et al.
System: The UNT Digital Library
Coherent Soft X-Ray Generation in the Water Window with the EEHG Scheme (open access)

Coherent Soft X-Ray Generation in the Water Window with the EEHG Scheme

Recently a scheme entitled echo-enabled harmonic generation (EEHG) was proposed for producing short wavelength FEL radiation that allows far higher harmonic numbers to be accessed as compared with the normal limit arising from incoherent energy spread. In this paper we study the feasibility of a single EEHG stage to generate coherent radiation in the 'water window' (2--4 nm wavelength) directly from a UV seed laser at 190-nm wavelength. We present time-dependent simulation results which demonstrate that the single-stage EEHG FEL can generate high power soft x-ray radiation in the water window with narrow bandwidth close to Fourier transform limit directly from a UV seed laser. The schemes to generate short x-ray pulse from femtosecond to attosecond using EEHG FEL are also discussed.
Date: May 26, 2009
Creator: Xiang, D. & Stupakov, G.
System: The UNT Digital Library
Strain-dependent photoluminescence behavior in three geometries of CdSe/CdS nanocrystals (open access)

Strain-dependent photoluminescence behavior in three geometries of CdSe/CdS nanocrystals

In recent years, a new generation of quantum confined colloidal semiconductor structures has emerged, with more complex shapes than simple quantum dots1, 2. These include nanorods3 and tetrapods4. Beyond shape, it is also now possible to spatially vary the electron and hole potentials within these nanoparticles by varying the composition. Examples of these new structures include seeded dots, rods, and tetrapods, which contain a CdSe core embedded within a CdS shell5, 6. These structures may have many uses beyond those envisioned for simple quantum dots, which are frequently employed in luminescent applications7. This paper is concerned with changes in the optoelectronic properties of tetrapods when the arms are bent. We demonstrate that seeded tetrapods can serve as an optical strain gauge, capable of measuring forces on the order of nanonewtons. We anticipate that a nanocrystal strain gauge with optical readout will be useful for applications ranging from sensitive optomechanical devices to biological force investigations.
Date: May 26, 2009
Creator: Choi, Charina L; Koski, Kristie J; Sivasankar, Sanjeevi & Alivisatos, A. Paul
System: The UNT Digital Library