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A HAMILTONIAN FORMULATION FOR SPIRAL-SECTOR ACCELERATORS. (open access)

A HAMILTONIAN FORMULATION FOR SPIRAL-SECTOR ACCELERATORS.

I develop a formulation for Hamiltonian dynamics in an accelerator with magnets whose edges follow a spiral. I demonstrate using this Hamiltonian that a spiral FFAG can be made perfectly 'scaling'. I examine the effect of tilting an RF cavity with respect a radial line from the center of the machine, potentially with a different angle than the spiral of the magnets.
Date: November 5, 2007
Creator: Berg, J. S.
System: The UNT Digital Library
Energetics of Multiple-Ion Species Hohlraum Plasmas (open access)

Energetics of Multiple-Ion Species Hohlraum Plasmas

A study of the laser-plasma interaction processes in multiple-ion species plasmas has been performed in plasmas that are created to emulate the plasma conditions in indirect drive inertial confinement fusion targets. Gas-filled hohlraums with densities of xe22/cc are heated to Te=3keV and backscattered laser light is measured by a suite of absolutely calibrated backscatter diagnostics. Ion Landau damping is increased by adding hydrogen to the CO2/CF4 gas fill. We find that the backscatter from stimulated Brillouin scattering is reduced is monotonically reduced with increasing damping, demonstrating that Landau damping is the controlling damping mechanism in ICF relevant high-electron temperature plasmas. The reduction in backscatter is accompanied by a comparable increase in both transmission of a probe beam and an increased hohlraum radiation temperature, showing that multiple-ion species plasmas improve the overall hohlraum energetics/performance. Comparison of the experimental data to linear gain calculations as well as detailed full-scale 3D laser-plasma interaction simulations show quantitative agreement. Our findings confirm the importance of Landau damping in controlling backscatter from high-electron temperature hohlraum plasmas and have lead to the inclusion of multi-ion species plasmas in the hohlraum point design for upcoming ignition campaigns at the National Ignition Facility.
Date: November 5, 2007
Creator: Neumayer, P; Berger, R; Callahan, D; Divol, L; Froula, D; London, R et al.
System: The UNT Digital Library
Search for Invisible Decays of a Light Scalar in Radiative Transitions Y(3S)->gamma A0 (open access)

Search for Invisible Decays of a Light Scalar in Radiative Transitions Y(3S)->gamma A0

We search for a light scalar particle produced in single-photon decays of the {Upsilon}(3S) resonance through the process {Upsilon}(3S) {yields} {gamma} + A{sup 0}, A{sup 0} {yields} invisible. Such an object appears in Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. If, in addition, there exists a light, stable neutralino, decays of A{sup 0} could be preferentially to an invisible final state. We search for events with a single high-energy photon and a large missing mass, consistent with a 2-body decay of {Upsilon}(3S). We find no evidence for such processes in a sample of 122 x 10{sup 6} {Upsilon}(3S) decays collected by the BABAR collaboration at the PEP-II B-factory, and set 90% C.L. upper limits on the branching fraction {Beta}({Upsilon}(3S) {yields} {gamma}A{sup 0}) x {Beta}(A{sup 0} {yields} invisible) at (0.7-31) x 10{sup -6} in the mass range m{sub A{sup 0}} {le} 7.8 GeV. The results are preliminary.
Date: November 5, 2008
Creator: Aubert, B.
System: The UNT Digital Library
Holographic Systematics of D-brane Inflation (open access)

Holographic Systematics of D-brane Inflation

We provide a systematic treatment of possible corrections to the inflaton potential for D-brane inflation in the warped deformed conifold. We consider the D3-brane potential in the presence of the most general possible corrections to the throat geometry sourced by coupling to the bulk of a compact Calabi-Yau space. This corresponds to the potential on the Coulomb branch of the dual gauge theory, in the presence of arbitrary perturbations of the Lagrangian. The leading contributions arise from perturbations by the most relevant operators that do not destroy the throat geometry. We find a generic contribution from a non-chiral operator of dimension {Delta} = 2 associated with a global symmetry current, resulting in a negative contribution to the inflaton mass-squared. If the Calabi-Yau preserves certain discrete symmetries, this is the dominant correction to the inflaton potential, and fine-tuning of the inflaton mass is possible. In the absence of such discrete symmetries, the dominant contribution comes from a chiral operator with {Delta} = 3/2, corresponding to a {phi}{sup 3/2} term in the inflaton potential. The resulting inflationary models are phenomenologically identical to the inflection point scenarios arising from specific D7-brane embeddings, but occur under far more general circumstances. Our strategy extends immediately …
Date: November 5, 2008
Creator: Baumann, Daniel; /Harvard U., Phys. Dept. /Princeton U.; Dymarsky, Anatoly; /Stanford U., Phys. Dept.; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC et al.
System: The UNT Digital Library
Interface Structure and Transport of Complex Oxide Junctions (open access)

Interface Structure and Transport of Complex Oxide Junctions

The interface structure and magnetism of hybrid magnetic tunnel junction-spin filter devices have been investigated and correlated with their transport properties. Magnetic tunnel junctions made of a spinel NiMn2O4 tunnel barrier sandwiched by theoretically predicted half-metallic electrodes, perovskite La0.7Sr0.3MnO3 and spinel Fe3O4, exhibit very high crystalline quality as observed by transmission electron microscopy. Structurally abrupt interfaces allow for the distinct magnetic switching of the electrodes as well as large junction magnetoresistance. The change in the magnetic anisotropy observed at the spinel-spinel interface is indicative of a thin interdiffused magnetically soft interfacial layer. The strong exchange coupling at this interface allows for low background magnetoresistance, and a spin-filter effect with when the barrier is ferrimagnetic.
Date: November 5, 2008
Creator: Nelson-Cheeseman, B.B.; Wong, F.; Chopdekar, R.V.; Chi, M.; Arenholz, E.; Browning, N.D et al.
System: The UNT Digital Library
Measurement of the Branching Fractions of Bbar -> D** l^- nubar_l Decays in Events Tagged by a Fully Reconstructed B Meson (open access)

Measurement of the Branching Fractions of Bbar -> D** l^- nubar_l Decays in Events Tagged by a Fully Reconstructed B Meson

We report a measurement of the branching fractions of {bar B} {yields} D** {ell}{sup -}{bar {nu}}{sub {ell}} decays based on 417 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D{sup (*)})-m(D{sup (*)}) is performed to extract the signal yields of the different D** states. We observe the {bar B} {yields} D**{ell}{sup -}{bar {nu}}{sub {ell}} decay modes corresponding to the four D** states predicted by Heavy Quark Symmetry with a significance greater than six standard deviations including systematic uncertainties.
Date: November 5, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Magnetic Detachment and Plume Control in Escaping Magnetized Plasma (open access)

Magnetic Detachment and Plume Control in Escaping Magnetized Plasma

The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment.
Date: November 5, 2008
Creator: Fisch, P. F. Schmit and N. J.
System: The UNT Digital Library
Tracking of Acceleration With Hnj Method. (open access)

Tracking of Acceleration With Hnj Method.

After reviewing the principle of operation of acceleration with the method of Harmonic Number Jump (HNJ) in a Fixed-Field Alternating-Gradient (FFAG) accelerator for protons and heavy ions, we report in this talk the results of computer simulations performed to assess the capability and the limits of the method in a variety of practical situations. Though the study is not yet completed, and there still remain other cases to be investigated, nonetheless the tracking results so far obtained are very encouraging, and confirm the validity of the method.
Date: November 5, 2007
Creator: Ruggiero, A. G.
System: The UNT Digital Library
Gravity Duals of Lifshitz-Like Fixed Points (open access)

Gravity Duals of Lifshitz-Like Fixed Points

We find candidate macroscopic gravity duals for scale-invariant but non-Lorentz invariant fixed points, which do not have particle number as a conserved quantity. We compute two-point correlation functions which exhibit novel behavior relative to their AdS counterparts, and find holographic renormalization group flows to conformal field theories. Our theories are characterized by a dynamical critical exponent z, which governs the anisotropy between spatial and temporal scaling t {yields} {lambda}{sup z}t, x {yields} {lambda}x; we focus on the case with z = 2. Such theories describe multicritical points in certain magnetic materials and liquid crystals, and have been shown to arise at quantum critical points in toy models of the cuprate superconductors. This work can be considered a small step towards making useful dual descriptions of such critical points.
Date: November 5, 2008
Creator: Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC; Liu, Xiao; Phys., /Perimeter Inst. Theor.; Mulligan, Michael & /Stanford U., Phys. Dept. /SLAC
System: The UNT Digital Library
Measurement of the Color-Suppressed B0->D(*)0 pi0 /omega/eta/eta Prime Branching Fractions (open access)

Measurement of the Color-Suppressed B0->D(*)0 pi0 /omega/eta/eta Prime Branching Fractions

The authors report results on the branching fraction (BF) measurement of the color-suppressed decays {bar B}{sup 0} {yields} D{sup 0}{pi}{sup 0}, D*{sup 0}{pi}{sup 0}, D{sup 0}{eta}, D*{sup 0}{eta}, D{sup 0}{omega}, D*{sup 0}{omega}, D{sup 0}{eta}{prime}, and D*{sup 0}{eta}{prime}. They measure the branching fractions BF(D{sup 0}{pi}{sup 0}) = (2.78 {+-} 0.08 {+-} 0.20) x 10{sup -4}, BF(D*{sup 0}{pi}{sup 0}) = (1.78 {+-} 0.13 {+-} 0.23) x 10{sup -4}, BF(D{sup 0}{eta}) = (2.41 {+-} 0.09 {+-} 0.17) x 10{sup -4}, BF(D*{sup 0}{eta}) = (2.32 {+-} 0.13 {+-} 0.22) x 10{sup -4}, BF(D{sup 0}{omega}) = (2.77 {+-} 0.13 {+-} 0.22) x 10{sup -4}, BF(D*{sup 0}{omega}) = (4.44 {+-} 0.23 {+-} 0.61) x 10{sup -4}, BF(D{sup 0}{eta}{prime}) = (1.38 {+-} 0.12 {+-} 0.22) x 10{sup -4} and BF(D*{sup 0}{eta}{prime}) = (1.29 {+-} 0.23 {+-} 0.23) x 10{sup -4}, where the first uncertainty is statistical and the second is systematic. The result is based on a sample of (454 {+-} 5) x 10{sup 6} B{bar B} pairs collected at the {Upsilon}(4S) resonance from 1999 to 2007, with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The measurements are compared to theoretical predictions by factorization, SCET and pQCD. The presence of …
Date: November 5, 2008
Creator: Prudent, X
System: The UNT Digital Library
Far-from-equilibrium measurements of thermodynamic length (open access)

Far-from-equilibrium measurements of thermodynamic length

Thermodynamic length is a path function that generalizes the notion of length to the surface of thermodynamic states. Here, we show how to measure thermodynamic length in far-from-equilibrium experiments using the work fluctuation relations. For these microscopic systems, it proves necessary to define the thermodynamic length in terms of the Fisher information. Consequently, the thermodynamic length can be directly related to the magnitude of fluctuations about equilibrium. The work fluctuation relations link the work and the free energy change during an external perturbation on a system. We use this result to determine equilibrium averages at intermediate points of the protocol in which the system is out-of-equilibrium. This allows us to extend Bennett's method to determine the potential of mean force, as well as the thermodynamic length, in single molecule experiments.
Date: November 5, 2008
Creator: Feng, Edward H. & Crooks, Gavin E.
System: The UNT Digital Library
Rbrc Scientific Review Committee Meeting - Volume 87 (open access)

Rbrc Scientific Review Committee Meeting - Volume 87

None
Date: November 5, 2007
Creator: Samios, N. P.
System: The UNT Digital Library
AIR PERMIT COMPLIANCE FOR WASTE RETRIEVAL OEPRATIONS INVOLVING MULTI-UNIT OPERATIONS (open access)

AIR PERMIT COMPLIANCE FOR WASTE RETRIEVAL OEPRATIONS INVOLVING MULTI-UNIT OPERATIONS

Since 1970, approximately 38,000 suspect-transuranic and transuranic waste containers have been placed in retrievable storage on the Hanford Site in the 200 Areas burial grounds. Hanford's Waste Retrieval Project is retrieving these buried containers and processing them for safe storage and disposition. Container retrieval activities require an air emissions permit to account for potential emissions of radionuclides. The air permit covers the excavation activities as well as activities associated with assaying containers and installing filters in the retrieved transuranic containers lacking proper venting devices. Fluor Hanford, Inc. is required to track radioactive emissions resulting from the retrieval activities. Air, soil, and debris media contribute to the emissions and enabling assumptions allow for calculation of emissions. Each of these activities is limited to an allowed annual emission (per calendar year) and .contributes to the overall total emissions allowed for waste retrieval operations. Tracking these emissions is required to ensure a permit exceedance does not occur. A tracking tool was developed to calculate potential emissions in real time sense. Logic evaluations are established within the tracking system to compare real time data against license limits to ensure values are not exceeded for either an individual activity or the total limit. Data input …
Date: November 5, 2007
Creator: FM, SIMMONS
System: The UNT Digital Library
On the Relation Between Mechanisms for Single-Transverse-SpinAsymmetries (open access)

On the Relation Between Mechanisms for Single-Transverse-SpinAsymmetries

Recent studies have shown that two widely-used mechanismsfor single-transverse-spin asymmetries based on either twist-threecontributions or on transverse-momentum-dependent (Sivers) partondistributions become identical in a kinematical regime of overlap. Thiswas demonstrated for the so-called soft-gluon-pole and hard-polecontributions to the asymmetry associated with a particular quark-gluoncorrelation function in the nucleon. In this paper, using semi-inclusivedeep inelastic scattering as an example, we extend the study to thecontributions by soft-fermion poles and by another independenttwist-three correlation function. We find that these additional termsorganize themselves in such a way as to maintain the mutual consistencyof the two mechanisms for single-spin asymmetries.
Date: November 5, 2007
Creator: Koike, Yuji; Vogelsang, Werner & Yuan, Feng
System: The UNT Digital Library
Geometric transitions and D-term SUSY breaking (open access)

Geometric transitions and D-term SUSY breaking

We propose a new way of using geometric transitions to study metastable vacua in string theory and certain confining gauge theories. The gauge theories in question are N=2 supersymmetric theories deformed to N=1 by superpotential terms. We first geometrically engineer supersymmetry-breaking vacua by wrapping D5 branes on rigid 2-cycles in noncompact Calabi-Yau geometries, such that the central charges of the branes are misaligned. In a limit of slightly misaligned charges, this has a gauge theory description, where supersymmetry is broken by Fayet-Iliopoulos D-terms. Geometric transitions relate these configurations to dual Calabi-Yaus with fluxes, where H_RR, H_NS and dJ are all nonvanishing. We argue that the dual geometry can be effectively used to study the resulting non-supersymmetric, confining vacua
Date: November 5, 2007
Creator: Aganagic, Mina; Aganagic, Mina & Beem, Christopher
System: The UNT Digital Library
Contraints on New Physics in MFV models: a model-independent analysis of \DeltaF=1 processes (open access)

Contraints on New Physics in MFV models: a model-independent analysis of \DeltaF=1 processes

We analyze the constraints on dimension-six {Delta}F = 1 effective operators in models respecting the MFV hypothesis, both in the one-Higgs doublet case and in the two-Higgs doublet scenario with large tan {beta}. The constraints are derived mainly from the b {yields} s inclusive observables measured at the B factories. The implications of these bounds in view of improved measurements in exclusive and inclusive observables in b {yields} s{ell}{sup +}{ell}{sup -} and s {yields} d{nu}{bar {nu}} transitions are discussed.
Date: November 5, 2008
Creator: Hurth, Tobias; /SLAC, /CERN; Isidori, Gino; /Pisa, Scuola Normale Superiore /INFN, Pisa /Frascati; Kamenik, Jernej F.; /Frascati /Stefan Inst., Ljubljana et al.
System: The UNT Digital Library
Evidence for B Semileptonic Decays into the Lambda_c Charm Baryon (open access)

Evidence for B Semileptonic Decays into the Lambda_c Charm Baryon

We present the first evidence for B semileptonic decays into the charmed baryon {Lambda}{sub c}{sup +} based on 420 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We measure the relative branching fraction {Beta}({bar B} {yields} {Lambda}{sub c}{sup +} X{ell}{sup -}{bar {nu}}{sub {ell}})/{Beta}({bar B} {yields} {Lambda}{sub c}{sup +}/{bar {Lambda}}{sub c}{sup -}X) = (3.2 {+-} 0.9{sub stat.} {+-} 0.9{sub syst.})%. The significance of the signal including the systematic uncertainty is 4.9 standard deviations.
Date: November 5, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Catalytic epoxidation of propene with H2O-O2 reactants on Au/TiO2 (open access)

Catalytic epoxidation of propene with H2O-O2 reactants on Au/TiO2

Au/TiO{sub 2} catalysts form hydroperoxy species from H{sub 2}O-O{sub 2} mixtures at near-ambient temperatures. These species can be used in the selective epoxidation of propene to propylene oxide.
Date: November 5, 2008
Creator: Ojeda, Manuel & Iglesia, Enrique
System: The UNT Digital Library
Determination of Dark Matter Properties at High-Energy Colliders (open access)

Determination of Dark Matter Properties at High-Energy Colliders

If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the nextgeneration of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From this, we can predict the cosmic density, the annihilation cross sections, and the cross sections relevant to direct detection. In this paper, we present studies in supersymmetry models with neutralino dark matter that give quantitative estimates of the accuracy that can be expected. We show that these are well matched to the requirements of anticipated astrophysical observations of dark matter. The capabilities of the proposed International Linear Collider (ILC) are expected to play a particularly important role in this study.
Date: November 5, 2006
Creator: Baltz, Edward A.; Battaglia, Marco; Peskin, Michael E. & Wizansky, Tommer
System: The UNT Digital Library
ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY (open access)

ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY

Highly industrialized areas pose significant challenges for surface based electrical resistivity characterization and monitoring due to the high degree of metallic infrastructure. The infrastructure is typically several orders of magnitude more conductive than the desired targets, preventing the geophysicist from obtaining a clear picture of the subsurface. These challenges may be minimized if steel-cased wells are used as long electrodes. We demonstrate a method of using long electrodes in a complex nuclear waste facility to monitor a simulated leak from an underground storage tank. The leak was simulated by injecting high conductivity fluid in a perforated well and the resistivity measurements were made before and after the leak test. The data were processed in four dimensions, where a regularization procedure was applied in both the time and space domains. The results showed a lowered resistivity feature develop south of the injection site. The time lapsed regularization parameter had a strong influence on the differences in inverted resistivity between the pre and post datasets, potentially making calibration of the results to specific hydrogeologic parameters difficult.
Date: November 5, 2009
Creator: Rucker, D. F.; Fink, J. B.; Loke, M. H. & Myers, D. A.
System: The UNT Digital Library
Antiferromagnetic exchange bias of a ferromagnetic semiconductor by a ferromagnetic metal (open access)

Antiferromagnetic exchange bias of a ferromagnetic semiconductor by a ferromagnetic metal

We demonstrate an exchange bias in (Ga,Mn)As induced by antiferromagnetic coupling to a thin overlayer of Fe. Bias fields of up to 240 Oe are observed. Using element-specific x-ray magnetic circular dichroism measurements, we distinguish an interface layer that is strongly pinned antiferromagnetically to the Fe. The interface layer remains polarized at room temperature.
Date: November 5, 2009
Creator: Olejnik, K.; Wadley, P.; Haigh, J.; Edmonds, K. W.; Campion, R. P.; Rushforth, A. W. et al.
System: The UNT Digital Library
Engineering design of a 40 kV neutral-beam source (open access)

Engineering design of a 40 kV neutral-beam source

Sections of the 40-kV, 40-A, TMX source are shown. This module is comprised of the arc chamber and accelerator sections. The source accelerator section uses a single rectangular insulator to perform three functions: providing voltage standoff, forming the supporting structure, and acting as the vacuum wall. Both machinable glass ceramic (Corning Macor/sup TM/) and F.R.P. (Nema G-10) have been used for this insulater. In either case, the insulator is joined to the titanium base plate and extractor electrode by thermal-setting-epoxy adhesive. The parts are self jigging; the bonding is done at 120 to 130 /sup 0/C under a load of .34 MPa (50 psi).
Date: November 5, 1979
Creator: Duffy, T. J.; Molvik, A. W.; Baird, E. D.; Correll, D. L.; Munger, R. H.; Gillespie, K. et al.
System: The UNT Digital Library
Software for the Local Control and Instrumentation System for MFTF (open access)

Software for the Local Control and Instrumentation System for MFTF

There are nine different systems requiring over fifty computers in the Local Control and Instrumentation System for the Mirror Fusion Test Facility. Each computer system consists of an LSI-11/2 processor with 32,000 words of memory, a serial driver that implements the CAMAC serial highway protocol. With this large number of systems it is important that as much software as possible be common to all systems. A serial communications system has been developed for data transfers between the LSI-11/2's and the supervisory computers. This system is based on the RS 232 C interface with modem control lines. Six modem control lines are used for hardware handshaking, which allows totally independent full duplex communications to occur. Odd parity on each byte and a 16-bit checksum are used to detect errors in transmission.
Date: November 5, 1979
Creator: Labiak, W. G.
System: The UNT Digital Library
Water-cooled U-tube grids for continuously operated neutral-beam injectors (open access)

Water-cooled U-tube grids for continuously operated neutral-beam injectors

A design for water-cooled extractor grids for long-pulse and continuously operated ion sources for neutral-beam injectors is described. The most serious design problem encountered is that of minimizing the thermal deformation (bowing) of these slender grid rails, which have typical overall spans of 150 mm and diameters on the order of 1 mm. A unique U-tube design is proposed that offers the possibility of keeping the thermal bowing down to about 0.05 mm (about 2.0 mils). However, the design requires high-velocity cooling water at a Reynolds number of about 3 x 10/sup 4/ and an inlet pressure on the order of 4.67 x 10/sup 6/ Pa (677 psia) in order to keep the axial and circumferential temperature differences small enough to achieve the desired small thermal bowing. It appears possible to fabricate and assemble these U-tube grids out of molybdenum with high precision and with a reasonably small number of brazes.
Date: November 5, 1979
Creator: Hoffman, M. A. & Duffy, T. J.
System: The UNT Digital Library