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GLUON POLARIZATION IN THE NUCLEON. (open access)

GLUON POLARIZATION IN THE NUCLEON.

We give a brief overview of the physics related to the spin-dependent gluon distribution of the nucleon.
Date: October 24, 2005
Creator: VOGELSANG, W.
System: The UNT Digital Library
Efficient Coupling of 527 nm Laser Beam Power to a Long Scalelength Plasma (open access)

Efficient Coupling of 527 nm Laser Beam Power to a Long Scalelength Plasma

We experimentally demonstrate that application of laser smoothing schemes including smoothing by spectral dispersion (SSD) and polarization smoothing (PS) increases the intensity range for efficient coupling of frequency doubled (527 nm) laser light to a long scalelength plasma with n{sub e}/n{sub cr} = 0.14 and T{sub e} = 2 keV.
Date: August 24, 2005
Creator: Moody, J. D.; Divol, L.; Glenzer, S. H.; MacKinnon, A. J.; Froula, D. H.; Gregori, G. et al.
System: The UNT Digital Library
IFE Thick Liquid Wall Chamber Dynamics: Governing Mechanisms and Modeling and Experimental Capabilities (open access)

IFE Thick Liquid Wall Chamber Dynamics: Governing Mechanisms and Modeling and Experimental Capabilities

For thick liquid wall concepts, it is important to understand the different mechanisms affecting the chamber dynamics and the state of the chamber prior to each shot a compared with requirements from the driver and target. These include ablation mechanisms, vapor transport and control, possible aerosol formation, as well as protective jet behavior. This paper was motivated by a town meeting on this subject which helped identify the major issues, assess the latest results, review the capabilities of existing modeling and experimental facilities with respect to addressing remaining issues, and helping guide future analysis and R&D efforts; the paper covers these exact points.
Date: January 24, 2005
Creator: Raffray, A. R.; Meier, W.; Abdel-Khalik, S.; Bonazza, R.; Calderoni, P.; Debonnel, C. S. et al.
System: The UNT Digital Library
Rhic Upgrades for Heavy Ions and Polarized Protons. (open access)

Rhic Upgrades for Heavy Ions and Polarized Protons.

The Relativistic Heavy Ion Collider (RHIC), in operation since 2000, has exceeded its design parameters. The Enhanced Design parameters, expected to be reached in 2009, call for a 4-fold increase over the heavy ion design luminosity, and a 15-fold increase over the proton design luminosity, the latter with an average polarization of 70%. Also in 2009, it is planned to commission a new Electron Beam Ion Source, offering increased reliability and ion species that cannot be supplied currently. The upgrade to RHIC 11, based on electron cooling of the beams, aims to increase the average heavy ion luminosity by an order of magnitude, and the polarized proton luminosity by a factor 2-5. Plans for an electron-ion collider eRHIC is covered in another article in these proceedings.
Date: October 24, 2005
Creator: Fischer, W.; Alessi, J.; Ben-Zvi, Ilan; Litvinenko, V. & Roser, T.
System: The UNT Digital Library
An Anelastic Allspeed Projection Method for GravitationallyStratified Flows (open access)

An Anelastic Allspeed Projection Method for GravitationallyStratified Flows

This paper looks at gravitationally-stratified atmospheric flows at low Mach and Froude numbers and proposes a new algorithm to solve the compressible Euler equations, in which the asymptotic limits are recovered numerically and the boundary conditions for block-structured local refinement methods are well-posed. The model is non-hydrostatic and the numerical algorithm uses a splitting to separate the fast acoustic dynamics from the slower anelastic dynamics. The acoustic waves are treated implicitly while the anelastic dynamics is treated semi-implicitly and an embedded-boundary method is used to represent mountain ranges. We present an example that verifies our asymptotic analysis and a set of results that compares very well with the classical gravity wave results presented by Durran.
Date: February 24, 2005
Creator: Gatti-Bono, Caroline & Colella, Phillip
System: The UNT Digital Library
QUARKONIA IN A DECONFINED GLUONIC PLASMA. (open access)

QUARKONIA IN A DECONFINED GLUONIC PLASMA.

We discuss lattice results on the properties of finite momentum cliarmonium states in a gluonic plasma. We also present preliminary results for bottomonium correlators and spectral functions in the plasma. Significant modifications of {chi}{sub b{sub 0.1}} states are seen at temperatures of 1.5 T{sub c}.
Date: October 24, 2005
Creator: Datta, S.; Jakovac, A.; Karsch, F. & Petreczky, P.
System: The UNT Digital Library
Measurements of Lamba and Anti-Lambda Polarization in Longitudinally Polarized Proton-Proton Collisions at Sqrt S(Nn) = 200 Gev at STAR (open access)

Measurements of Lamba and Anti-Lambda Polarization in Longitudinally Polarized Proton-Proton Collisions at Sqrt S(Nn) = 200 Gev at STAR

Preliminary results for the longitudinal polarization of A and hyperons in longitudinally polarized proton-proton collisions at {radical}s = 200 GeV are presented. The {Lambda}({bar {Lambda}}) candidates are reconstructed at mid-rapidity (|{eta}| < 1) with the time projection chamber of the STAR experiment at RHIC, using 0.5 pb{sup -1} collected in 2003 and 2004 with beam polarizations of up to 45%. Their mean longitudinal momentum fraction x{sub F} is about 8 x 10{sup -3} and their mean transverse momentum p{sub T} is about 1.5 GeV. The analysis uses asymmetries of counts for different spin states of the colliding proton beams and does not require detailed knowledge of the detector acceptance. The preliminary {Lambda}({Lambda}) polarization values are consistent with zero within their statistical uncertainties of 0.05.
Date: October 24, 2005
Creator: Xu, Q.
System: The UNT Digital Library
Discrete Particle Noise in Particle-in-Cell Simulations of Plasma Microturbulence (open access)

Discrete Particle Noise in Particle-in-Cell Simulations of Plasma Microturbulence

Recent gyrokinetic simulations of electron temperature gradient (ETG) turbulence with flux-tube continuum codes vs. the global particle-in-cell (PIC) code GTC yielded different results despite similar plasma parameters. Differences between the simulations results were attributed to insufficient phase-space resolution and novel physics associated with toroidicity and/or global simulations. We have reproduced the results of the global PIC code using the flux-tube PIC code PG3EQ, thereby eliminating global effects as the cause of the discrepancy. We show that the late-time decay of ETG turbulence and the steady-state heat transport observed in these PIC simulations results from discrete particle noise. Discrete particle noise is a numerical artifact, so both these PG3EQ simulations and the previous GTC simulations have nothing to say about steady-state ETG turbulence and the associated anomalous heat transport. In the course of this work we develop three diagnostics which can help to determine if a particular PIC simulation has become dominated by discrete particle noise.
Date: May 24, 2005
Creator: Nevins, W M; Dimits, A & Hammett, G
System: The UNT Digital Library
Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D (open access)

Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D

Plasma boundary modeling of low density, low confinement plasmas in DIII-D has been benchmarked against a comprehensive set of measurements and indicates that recycling of deuterium ions at the divertor targets, and chemical sputtering at the divertor target plates and walls, can explain the poloidal core fueling profile and core carbon density. Key measurements included the 2-D intensity distribution of deuterium neutral and low-charge state carbon emission in the divertor and around the midplane of the high-field scrape-off layer (SOL). Chemical sputtering plays an important role in producing carbon at the divertor targets and walls, and was found to be a prerequisite to reproduce the measured emission distribution.
Date: June 24, 2005
Creator: Groth, M.; Porter, G.; Bray, B.; Brooks, N.; Fenstermacher, M.; Groebner, R. et al.
System: The UNT Digital Library
Radiation induced crosslinking in a silica-filled silicone elastomer as investigated by multiple quantum H NMR (open access)

Radiation induced crosslinking in a silica-filled silicone elastomer as investigated by multiple quantum H NMR

DC745 is a commercially available silicone elastomer consisting of dimethyl, methylphenyl, and vinyl-methyl siloxane monomers crosslinked with a peroxide vinyl specific curing agent. It is generally considered to age gracefully and to be resistant to chemical and thermally harsh environments. However, little data exists on the radiation resistance of this commonly used silicone elastomer. We report static {sup 1}H NMR studies of residual dipolar couplings in DC745 solid elastomers subject to exposure to ionizing gamma radiation. {sup 1}H spin-echo NMR data shows that with increasing dose, the segmental dynamics decrease is consistent with radiatively induced crosslinking. {sup 1}H multiple quantum NMR was used to assess changes in the network structure and observed the presence of a bimodal distribution of residual dipolar couplings, <{Omega}{sub d}>, that were dose dependent. The domain with the lower <{Omega}{sub d}> has been assigned to the polymer network while the domain with the higher <{Omega}{sub d}> has been assigned to polymer chains interacting with the inorganic filler surfaces. In samples exposed to radiation, the residual dipolar couplings in both reservoirs were observed to increase and the populations were observed to be dose dependent. The NMR results are compared to Differential Scanning Calorimetry (DSC) and a two-step …
Date: May 24, 2005
Creator: Maxwell, R S; Chinn, S C; Solyom, D & Cohenour, R
System: The UNT Digital Library
Temperature Determination Using K(alpha) Spectra from M-shell Ti Ions (open access)

Temperature Determination Using K(alpha) Spectra from M-shell Ti Ions

The Compact Multipulse Terawatt (COMET) laser facility at LLNL was used to irradiate Al-coated 2 - 50 {micro}m Ti foils with {approx} 4 x 10{sup 18} W cm{sup -2}, 500 fs, 3-6 J laser pulses. Laser-plasma interactions on the front side of the target generate hot electrons with sufficient energy to excite inner-shell electrons in Ti, creating K{sub {alpha}} emission which has been measured using a focusing spectrometer with spatial resolution (FSSR-1D) aimed at the back surface of the targets. The spatial extent of the emission varies with target thickness, and the high spectral resolution ({lambda}/{Delta}{lambda} {approx} 3800) is sufficient to measure blue shifts in K{sub {alpha}} arising from ionization of near-solid Ti into the 3p subshell. A self-consistent-field model is used to spectroscopically diagnose thermal electron temperatures up to 40 eV in the strongly coupled Ti plasmas.
Date: March 24, 2005
Creator: Hansen, S. B.; Faenov, A. Y.; Pikuz, T. A.; Fournier, K. B.; Shepherd, R.; Chen, H. et al.
System: The UNT Digital Library
Quasi-Static Analysis for Subsidence of Stacked B-25 Boxes (open access)

Quasi-Static Analysis for Subsidence of Stacked B-25 Boxes

This paper presents a quasi-static technique to evaluate the structural deformation of the four stacked B-25 boxes subjected to the static loads of overlaying soil and to determine the effect of corrosion on the deformation. Although the boxes are subjected to a static load, the structural responses of the boxes vary with time. The analytical results indeed show that the deflection, buckling and post buckling of the components of the stacked boxes occur in sequence rather than simultaneously. Therefore, it is more appropriate to treat the problems considered as quasistatic rather than static; namely, the structural response of the stacked boxes are dynamic but with very long duration. Furthermore, the finite-element model has complex contact and slide conditions between the interfaces of the adjoining components, and thus its numerical solution is more tractable by using explicit time integration schemes. The analysis covers the three corrosion scenarios following various time lengths of initial burial under an interim soil cover. The results qualitatively agree with expected differences in deformation for different degrees of corrosion subsidence potential reduction that can be achieved.
Date: May 24, 2005
Creator: Wu, Tsu-te; Jones, William E. & Phifer, Mark A.
System: The UNT Digital Library
Identified Particle Transverse Momentum Spectra in P+P and D+Au Collisions at Snn=200 Gev. (open access)

Identified Particle Transverse Momentum Spectra in P+P and D+Au Collisions at Snn=200 Gev.

The transverse momentum (pT) spectra for identified charged pions, protons and anti-protons from p+p and d+Au collisions are measured around midrapidity (|y| < 0.5) over the range of 0.3 < p{sub T} < 10 GeV/c at {radical}s{sub NN} = 200 GeV. The charged pion and proton+anti-proton spectra at high p{sub T} in p+p collisions have been compared with the next-to-leading order perturbative quantum chromodynamic (NLO pQCD) calculations with a specific fragmentation scheme. The p/{pi}{sup +} and {bar p}/{pi}{sup -} has been studied at high p{sub T}. The nuclear modification factor (R{sub dAu}) shows that the identified particle Cronin effects around midrapidity are significantly non-zero for charged pions and to be even larger for protons at intermediate p{sub T} (2 < p{sub T} < 5 GeV/c).
Date: October 24, 2005
Creator: Netrakanti, P. K.
System: The UNT Digital Library
Measurement of CP Asymmetries in B0->Ks Pi0 Pi0 Decays (open access)

Measurement of CP Asymmetries in B0->Ks Pi0 Pi0 Decays

The authors present a preliminary measurement of the time-dependent CP asymmetry for the neutral B-meson decay into the CP = +1 final state K{sub S}{sup 0}{pi}{sup 0}{pi}{sup 0}, with K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -} and {pi}{sup 0} {yields} {gamma}{gamma}. They use a sample of approximately 227 million B-meson pairs recorded at the {Upsilon}(4S) resonance by the BABAR detector at the PEP-II B-Factory at SLAC. From a maximum likelihood fit they extract the mixing-induced CP-violation parameter S{sub K{sub S}{sup 0}{pi}{sup 0}{pi}{sup 0}} = 0.84 {+-} 0.71(stat) {+-} 0.08(syst) and the direct CP-violation parameter C{sub K{sub S}{sup 0}}{pi}{sup 0}{pi}{sup 0} = 0.27 {+-} 0.52(stat) {+-} 0.13(syst), where the first uncertainty is statistical and the second systematic.
Date: August 24, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Compatibility of the Radiating Divertor with High Performance Plasmas in DIII-D (open access)

Compatibility of the Radiating Divertor with High Performance Plasmas in DIII-D

Excessive thermal power loading on the divertor structures presents a design difficulty for future-generation, high powered tokamaks. This difficulty may be mitigated by ''seeding'' the divertor with impurities which radiate a significant fraction of the power upstream of the divertor targets. For this ''radiating divertor'' concept to be practical, however, the confinement and stability of the plasma cannot be compromised by excessive leakage of the seeded impurities into the core plasma. One proposed way of reducing impurity influx is to enhance the directed scrape-off layer (SOL) flow of deuterium ions toward the divertor [1-5]. We report here on the successful application of the radiating divertor scenario to high performance plasma operation in a DIII-D ''hybrid'' H-mode regime. The ''hybrid'' regime [6,7] has many features in common with conventional ELMing H-mode regimes, such as high confinement, e.g., H{sub ITER89P} > 2, where H{sub ITER89P} is the energy confinement normalized to the 1989 ITER L-mode scaling [8]. The main difference is the absence of sawtooth activity in the hybrid. Argon was selected as the seeded impurity for this experiment because argon radiates effectively at both the divertor and pedestal temperatures found in DIII-D hybrid H-mode operation and has a relatively short ionization …
Date: June 24, 2005
Creator: Petrie, T; Wade, M; Allen, S; Brooks, N; Fenstermacher, M; Ferron, J et al.
System: The UNT Digital Library
Total Risk Approach in Applying PRA to Criticality Safety (open access)

Total Risk Approach in Applying PRA to Criticality Safety

As nuclear industry continues marching from an expert-base support to more procedure-base support, it is important to revisit the total risk concept to criticality safety. A key objective of criticality safety is to minimize total criticality accident risk. The purpose of this paper is to assess key constituents of total risk concept pertaining to criticality safety from an operations support perspective and to suggest a risk-informed means of utilizing criticality safety resources for minimizing total risk. A PRA methodology was used to assist this assessment. The criticality accident history was assessed to provide a framework for our evaluation. In supporting operations, the work of criticality safety engineers ranges from knowing the scope and configurations of a proposed operation, performing criticality hazards assessment to derive effective controls, assisting in training operators, response to floor questions, surveillance to ensure implementation of criticality controls, and response to criticality mishaps. In a compliance environment, the resource of criticality safety engineers is increasingly being directed towards tedious documentation effort to meet some regulatory requirements to the effect of weakening the floor support for criticality safety. By applying a fault tree model to identify the major contributors of criticality accidents, a total risk picture is obtained …
Date: March 24, 2005
Creator: Huang, S T
System: The UNT Digital Library
QCD THERMODYNAMICS WITH AN ALMOST REALISTIC QUARK MASS SPECTRUM. (open access)

QCD THERMODYNAMICS WITH AN ALMOST REALISTIC QUARK MASS SPECTRUM.

We will report on the status of a new large scale calculation of thermodynamic quantities in QCD with light up and down quarks corresponding to an almost physical light quark mass value and a heavier strange quark mass. These calculations are currently being performed on the QCDOC Teraflops computers at BNL. We will present new lattice calculations of the transition temperature and various susceptibilities reflecting properties of the chiral transition. All these quantities are of immediate interest for heavy ion phenomenology.
Date: October 24, 2005
Creator: SCHMIDT, C.
System: The UNT Digital Library
Measurement of the Double Longitudinal Spin Asymmetry in Inclusive Jet Production in Polarized P+P Collisions at S**(1/2) = 200 Gev. (open access)

Measurement of the Double Longitudinal Spin Asymmetry in Inclusive Jet Production in Polarized P+P Collisions at S**(1/2) = 200 Gev.

We present preliminary results for the first measurements of the double longitudinal spin asymmetry A{sub LL} in inclusive jet production at mid-rapidity in polarized proton-proton collisions at {radical}s = 200 GeV. The data amount to {approx} 0.5 pb{sup -1} collected at RHIC in 2003 and 2004 with beam polarizations up to 45%. The jet transverse energies are in the range of 5 < p{sub T} < 17 GeV/c. The data are consistent with theoretical evaluations using deep-inelastic scattering parametrizations for gluon polarization in the nucleon, and tend to disfavor large positive values of gluon polarization.
Date: October 24, 2005
Creator: Kiryluk, J.
System: The UNT Digital Library
Nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface (open access)

Nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface

This article discusses nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface.
Date: May 24, 2005
Creator: Brady, Ryan P.; Sharma, A. S.; Giblet, R. L.; Cottier, Ryan J.; Golding, Terry D. & Pérez, José M.
System: The UNT Digital Library
Experimental measurement of Au M-band flux in indirectly-driven double-shell implosions (open access)

Experimental measurement of Au M-band flux in indirectly-driven double-shell implosions

Indirectly-driven double-shell implosions are being investigated as a possible noncryogenic path to ignition on the National Ignition Facility (NIF). In recent double-shell experiments, the inner shell trajectory was shown to exhibit a strong sensitivity to the temporal history of the M-band (2-5 keV) radiation emitted from the Au hohlraum wall. A large time-dependent discrepancy was observed between measurement and simulation of the x-ray flux in this range. In order to better characterize the radiation environment seen in these implosions, an experimental campaign was conducted on the Omega Laser. A number of diagnostics were used to measure both the temporal and spectral nature of the M-band flux. Results were obtained from an absolutely calibrated 12 channel filtered x-ray diode array (Dante) as well as two streaked crystal spectrometers and an absolutely calibrated time-integrated spectrometer (Henway). X-ray backlighting was also used to directly measure the effect of M-band radiation on the trajectory of the inner shell. The data from all diagnostics are shown to be in excellent agreement and provide a consistent picture of the M-band flux. These results are being used to constrain and improve the simulation of hohlraum-generated M-band radiation that will be necessary for the design of future double-shell …
Date: March 24, 2005
Creator: Robey, H. F.; Perry, T. S.; Park, H. S.; Amendt, P.; Sorce, C. M.; Compton, S. M. et al.
System: The UNT Digital Library
Predicting cancer outcome (open access)

Predicting cancer outcome

We read with interest the paper by Michiels et al on the prediction of cancer with microarrays and the commentary by Ioannidis listing the potential as well as the limitations of this approach (February 5, p 488 and 454). Cancer is a disease characterized by complex, heterogeneous mechanisms and studies to define factors that can direct new drug discovery and use should be encouraged. However, this is easier said than done. Casti teaches that a better understanding does not necessarily extrapolate to better prediction, and that useful prediction is possible without complete understanding (1). To attempt both, explanation and prediction, in a single nonmathematical construct, is a tall order (Figure 1).
Date: March 24, 2005
Creator: Gardner, S N & Fernandes, M
System: The UNT Digital Library
SCALING OF THE SUPERFLUID DENSITY IN HIGH-TEMPERATURE SUPERCONDUCTORS. (open access)

SCALING OF THE SUPERFLUID DENSITY IN HIGH-TEMPERATURE SUPERCONDUCTORS.

A scaling relation N{sub c} {approx} 4.4{sigma}{sub dc}T{sub c} has been observed parallel and perpendicular to the copper-oxygen planes in the high-temperature superconductors; N{sub c} is the spectral weight and {sigma}{sub dc} is the dc conductivity just above the critical temperature T{sub c}. In addition, Nb and Pb also fall close to the this scaling line. The application of the Ferrell-Glover-Tinkham sum rule to the BCS optical properties of Nb above and below T{sub c} yields N{sub c} {approx} 8.1{sigma}{sub dc}T{sub c} when the normal-state scattering rate is much greater than the superconducting energy gap (1/{tau} > 2{Delta}, the ''dirty'' limit). This result implies that the high-temperature superconductors may be in the dirty limit. The superconductivity perpendicular to the planes is explained by the Josephson effect, which again yields N{sub c} {approx} 8.1{sigma}{sub dc}T{sub c} in the BCS formalism. The similar forms for the scaling relation in these two directions suggests that in some regime the dirty limit and the Josephson effect may be viewed as equivalent.
Date: October 24, 2005
Creator: HOMES, C.C.
System: The UNT Digital Library
A Graph Search Heuristic for Shortest Distance Paths (open access)

A Graph Search Heuristic for Shortest Distance Paths

This paper presents a heuristic for guiding A* search for finding the shortest distance path between two vertices in a connected, undirected, and explicitly stored graph. The heuristic requires a small amount of data to be stored at each vertex. The heuristic has application to quickly detecting relationships between two vertices in a large information or knowledge network. We compare the performance of this heuristic with breadth-first search on graphs with various topological properties. The results show that one or more orders of magnitude improvement in the number of vertices expanded is possible for large graphs, including Poisson random graphs.
Date: March 24, 2005
Creator: Chow, E
System: The UNT Digital Library
Super symmetry Parameter Analysis with Fittino (open access)

Super symmetry Parameter Analysis with Fittino

We present the results of a realistic global fit of the Lagrangian parameters of the Minimal Supersymmetric Standard Model to simulated data from ILC and LHC with realistic estimates of the observable uncertainties. Higher order radiative corrections are accounted for where ever possible to date. Results are obtained for a modified SPS1a MSSM benchmark scenario but they were checked not to depend critically on this assumption. Exploiting a simulated annealing algorithm, a stable result is obtained without any a priori assumptions on the fit parameters. Most of the Lagrangian parameters can be extracted at the percent level or better if theoretical uncertainties are neglected. Neither LHC nor ILC measurements alone will be sufficient to obtain a stable result. The effects of theoretical uncertainties arising from unknown higher-order corrections and parametric uncertainties are examined qualitatively. They appear to be relevant and the result motivates further precision calculations.
Date: June 24, 2005
Creator: Bechtle, Philip; Desch, Klaus & Wienemann, Peter
System: The UNT Digital Library