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ATOMIC BEAM POLARIZATION MEASUREMENT OF THE RHIC POLARIZED H-JET TARGET. (open access)

ATOMIC BEAM POLARIZATION MEASUREMENT OF THE RHIC POLARIZED H-JET TARGET.

The RHIC polarized H-Jet measures the polarization of the RHIC proton beam via elastic scattering off a nuclear polarized atomic hydrogen beam. The atomic beam is produced by a dissociator, a beam forming system and sextupole magnets. Nuclear polarization is achieved by exchanging occupation numbers of hyperfine states using high frequency transitions. The polarization was measured using a modified form of a Breit-Rabi polarimeter including focusing magnets and another set of high frequency transitions. The sampling of a large part of the beam and low noise electronics made it possible to measure the polarization to a high degree of accuracy in a very short time period (1 min). Using this system, we measured no depolarization of the atomic beam due to the RF fields of the bunched proton beam. Time-of-Flight measurements were done using a fast chopper and a QMA at the position of the RHIC interaction point to determine the areal density of the atomic beam seen by the RHIC beam.
Date: January 28, 2005
Creator: Makdisi, Y.; Nass, A.; Graham, D.; Kponou, A.; Mahler, G.; Meng, W. et al.
System: The UNT Digital Library
ATOMIC BEAM STUDIES IN THE RHIC H-JET POLARIMETER. (open access)

ATOMIC BEAM STUDIES IN THE RHIC H-JET POLARIMETER.

The results of atomic beam production studies are presented. Improved cooling of the atoms before jet formation in the dissociator cold nozzle apparently reduces the atomic beam velocity spread and improves beam focusing conditions. A carefully designed sextupole separating (and focusing) magnet system takes advantage of the high brightness source. As a result a record beam intensity of a 12.4 {center_dot} 10{sup 16} atoms/s was obtained within 10 mm acceptance at the collision point. The results of the polarization dilution factor measurements (by the hydrogen molecules at the collision point) are also presented.
Date: January 28, 2005
Creator: Makdisi, Y.; Zelenski, A.; Graham, D.; Kokhanovski, S.; Mahler, G.; Nass, A. et al.
System: The UNT Digital Library
Black Holes, q-Deformed 2d Yang-Mills, and Non-perturbative Topological Strings (open access)

Black Holes, q-Deformed 2d Yang-Mills, and Non-perturbative Topological Strings

We count the number of bound states of BPS black holes on local Calabi-Yau three-folds involving a Riemann surface of genus g. We show that the corresponding gauge theory on the brane reduces to a q-deformed Yang-Mills theory on the Riemann surface. Following the recent connection between the black hole entropy and the topological string partition function, we find that for a large black hole charge N, up to corrections of O(e^-N), Z_BH is given as a sum of a square of chiral blocks, each of which corresponds to a specific D-brane amplitude. The leading chiral block, the vacuum block, corresponds to the closed topological string amplitudes. The sub-leading chiral blocks involve topological string amplitudes with D-brane insertions at 2g-2 points on the Riemann surface analogous to the Omega points in the large N 2d Yang-Mills theory. The finite N amplitude provides a non-perturbative definition of topological strings in these backgrounds. This also leads to a novel non-perturbative formulation of c=1 non-critical string at the self-dual radius.
Date: January 28, 2005
Creator: Aganagic, Mina; Ooguri, Hirosi; Saulina, Natalia & Vafa, Cumrun
System: The UNT Digital Library
Laboratory simulations of supernova shockwaves: Formation of a second shock ahead of a radiative shock (open access)

Laboratory simulations of supernova shockwaves: Formation of a second shock ahead of a radiative shock

Supernovae launch spherical shocks into the circumstellar medium (CSM). These shocks may interact with both the intergalactic magnetic field (IGM) and local mass accumulations (possibly with their own local magnetic fields). The latter interaction may trigger star formation. The shocks have high Mach numbers and may be radiative. We have created similar shocks in the laboratory by focusing laser pulses onto the tip of a solid pin surrounded by ambient gas; ablated material from the pin rapidly expands and launches a shock through the surrounding gas. The shock may then be allowed to interact with (a) mass accumulations, (b) magnetic fields, or (c) allowed to expand freely. We will present examples of each type of experiment, but mainly discuss a new phenomena observed first in (c); at the edge of the radiatively heated gas ahead of the shock, a second shock forms. The two expanding shocks are simultaneously visible for a time, until the original shock stalls from running into the heated gas. The second shock remains visible and continues to expand. A minimum condition for the formation of the second shock is that the original shock is super-critical, i.e., the temperature distribution ahead of the original shock has an …
Date: January 28, 2005
Creator: Hansen, J. F.; Edwards, M. J.; Froula, D.; Gregori, G.; Edens, A. & Ditmire, T.
System: The UNT Digital Library
Measurement of the Analyzing Power in PP Elastic Scattering in the Peak CNI Region at RHIC (open access)

Measurement of the Analyzing Power in PP Elastic Scattering in the Peak CNI Region at RHIC

The analyzing power A{sub N} for pp elastic scattering is expected to reach a peak value of 0.045 in the Coulomb Nuclear Interference (CNI) region at a momentum transfer -t of 0.003 (GeV/c){sup 2}. During the 2004 RHIC Run, we completed a measurement of A{sub N} in the CNI region by detecting the recoil protons from pp elastic scattering using a polarized atomic hydrogen gas jet target and the 100 GeV RHIC proton beam. We report the first measurements of the A{sub N} absolute value and shape in the -t range from 0.0015 to 0.010 (GeV/c){sup 2} with a precision better than 0.005 for each A{sub N} data point. The recoil protons were detected with two arrays of Si detectors. The absolute target polarization as monitored by a Breit-Rabi polarimeter was stable at 0.924 {+-} 0.018. This result allows us to further investigate the spin dependence of elastic pp scattering in the very low -t region.
Date: January 28, 2005
Creator: Makdisi, Y.; Okada, H.; Alekseev, I. G.; Bravar, A.; Bunce, G. & AL, ET
System: The UNT Digital Library
Monte Carlo Simulation for the Majorana Neutrinoless Double-betaDecay Experiment (open access)

Monte Carlo Simulation for the Majorana Neutrinoless Double-betaDecay Experiment

The Majorana experiment is a proposed HPGe detector array that will primarily search for neutrinoless double-beta decay and dark matter. It will rely on pulse-shape discrimination and crystal segmentation to suppress backgrounds following careful materials selection. A critical aspect of the design phase of Majorana is a reliable simulation of the detector response, pulse formation, and its radioactive backgrounds. We are developing an adaptable and complete simulation based on GEANT 4 to address these requirements and the requirements of a modern, large collaboration experiment. The salient aspects of the simulation are presented. The Majorana experiment is presented in a parallel poster by Kareem Kazkaz.
Date: January 28, 2005
Creator: Henning, Reyco & Collaboration, Majorana
System: The UNT Digital Library
POLARIZED HYDROGEN JET TARGET FOR MEASUREMENT OF RHIC PROTON BEAM POLARIZATION. (open access)

POLARIZED HYDROGEN JET TARGET FOR MEASUREMENT OF RHIC PROTON BEAM POLARIZATION.

The performance and unique features of the RHIC polarized jet target and our solutions to the important design constraints imposed on the jet by the RHIC environment are described. The target polarization and thickness were measured to be 0.924 {+-} 2% and 1.3 {+-} 0.2 x 10{sup 12} atoms/cm{sup 2} respectively.
Date: January 28, 2005
Creator: Makdisi, Y.; Wise, T.; Chapman, M.; Graham, D.; Kponou, A.; Mahler, G. et al.
System: The UNT Digital Library
Second interlaboratory comparison study for the analysis of 239Pu in synthetic urine at the microBq (-100 aCi) level by mass spectrometry (open access)

Second interlaboratory comparison study for the analysis of 239Pu in synthetic urine at the microBq (-100 aCi) level by mass spectrometry

As a follow up to the initial 1998 intercomparison study, a second study was initiated in 2001 as part of the ongoing evaluation of the capabilities of various ultra-sensitive methods to analyze {sup 239}Pu in urine samples. The initial study was sponsored by the Department of Energy, Office of International Health Programs to evaluate and validate new technologies that may supersede the existing fission tract analysis (FTA) method for the analysis of {sup 239}Pu in urine at the {micro}Bq/l level. The ultra-sensitive techniques evaluated in the second study included accelerator mass spectrometry (AMS) by LLNL, thermal ionization mass spectrometry (TIMS) by LANL and FTA by the University of Utah. Only the results for the mass spectrometric methods will be presented. For the second study, the testing levels were approximately 4, 9, 29 and 56 {micro}Bq of {sup 239}Pu per liter of synthetic urine. Each test sample also contained {sup 240}Pu at a {sup 240}Pu/{sup 239}Pu atom ratio of {approx}0.15 and natural uranium at a concentration of 50 {micro}Bq/ml. From the results of the two studies, it can be inferred that the best performance at the {micro}Bq level is more laboratory specific than method specific. The second study demonstrated that LANL-TIMS …
Date: January 28, 2005
Creator: McCurdy, D.; Lin, Z.; Inn, K. W.; Bell, R., III; Wagner, S.; Efurd, D. W. et al.
System: The UNT Digital Library
Stable, free-standing Ge nanocrystals (open access)

Stable, free-standing Ge nanocrystals

Free-standing Ge nanocrystals that are stable under ambient conditions have been synthesized in a two-step process. First, nanocrystals with a mean diameter of 5 nm are grown in amorphous SiO{sub 2} by ion implantation followed by thermal annealing. The oxide matrix is then removed by selective etching in diluted HF to obtain free-standing nanocrystals on a Si wafer. After etching, nanocrystals are retained on the surface and the size distribution is not significantly altered. Free-standing nanocrystals are stable under ambient atmospheric conditions, suggesting formation of a self-limiting native oxide layer. For free-standing as opposed to embedded Ge nanocrystals, an additional amorphous-like contribution to the Raman spectrum is observed and is assigned to surface reconstruction-induced disordering of near-surface atoms.
Date: January 28, 2005
Creator: Sharp, I. D.; Xu, Q.; Liao, C. Y.; Yi, D. O.; Beeman, J. W.; Liliental-Weber, Z. et al.
System: The UNT Digital Library
Three-dimensional numerical simulations of Rayleigh-Taylorunstable flames in type Ia supernovae (open access)

Three-dimensional numerical simulations of Rayleigh-Taylorunstable flames in type Ia supernovae

Flame instabilities play a dominant role in accelerating the burning front to a large fraction of the speed of sound in a Type Ia supernova. We present a three-dimensional numerical simulation of a Rayleigh-Taylor unstable carbon flame, following its evolution through the transition to turbulence. A low Mach number hydrodynamics method is used, freeing us from the harsh time step restrictions imposed by sound waves. We fully resolve the thermal structure of the flame and its reaction zone, eliminating the need for a flame model. A single density is considered, 1.5x107 gm/cc, and half carbon/half oxygen fuel--conditions under which the flame propagated in the flamelet regime in our related two-dimensional study. We compare to a corresponding two-dimensional simulation, and show that while fire-polishing keeps the small features suppressed in two dimensions, turbulence wrinkles the flame on far smaller scales in the three-dimensional case, suggesting that the transition to the distributed burning regime occurs at higher densities in three dimensions. Detailed turbulence diagnostics are provided. We show that the turbulence follows a Kolmogorov spectrum and is highly anisotropic on the large scales, with a much larger integral scale in the direction of gravity. Furthermore, we demonstrate that it becomes more isotropic …
Date: January 28, 2005
Creator: Zingale, M.; Woosley, S.E.; Rendleman, C.A.; Day, M.S. & Bell, J.B.
System: The UNT Digital Library
Towards SiC Surface Functionalization: An Ab Initio Study (open access)

Towards SiC Surface Functionalization: An Ab Initio Study

We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for bio-compatible devices.
Date: January 28, 2005
Creator: Cicero, G & Catellani, A
System: The UNT Digital Library
TRANSVERSE SPIN AT PHENIX AND FUTURE PLANS. (open access)

TRANSVERSE SPIN AT PHENIX AND FUTURE PLANS.

The PHENIX experiment took data with transversely polarized proton beams in 2001-2002 and measured the transverse single spin asymmetries in inclusive neutral pion and non-identified charge hadrons at midrapidity and {radical} s = 200 GeV. The data near X{sub F} {approx} 0 cover a transverse momentum range from 0.5 to 5.0 GeV/c. The observed asymmetries are consistent with zero with good statistical accuracy. This paper presents the current work in light of earlier measurements at lower energies in this kinematic region and the future plans of the PHENIX detector.
Date: January 28, 2005
Creator: MAKDISI,Y. (FOR THE PHENIX COLLABORATION)
System: The UNT Digital Library
Wairakite: A Potential Indicator of Fluid Mixing (open access)

Wairakite: A Potential Indicator of Fluid Mixing

Wairakite is a common geothermal mineral. Detailed paragenetic studies indicate that wairakite typically forms after the deposition of epidote {plus_minus} prehnite and later anhydrite + calcite. Epidote and prehnite are interpreted as products of early, high temperature alteration associated with upswelling reservoir fluids whereas calcite and anhydrite are related to descending acidic condensates. Calculated stability relationships among the calc silicate minerals indicates that cooling and/or decreasing pH will lead to the deposition of wairakite instead of epidote, whereas decreasing pH favors wairakite over prehnite. We infer, from the petrographic relationships, that these changes occur when descending condensate mixes with the in-situ reservoir fluids during the waning stages of geothermal activity. Fluid inclusion measurements indicate wairakite is commonly deposited between temperatures of {approx}235 and 300 C.
Date: January 28, 2005
Creator: Moore, J; Bruton, C & Powell, T
System: The UNT Digital Library
Water at a hydrophilic solid surface probed by ab-initio molecular dynamics: inhomogeneous thin layers of dense fluid (open access)

Water at a hydrophilic solid surface probed by ab-initio molecular dynamics: inhomogeneous thin layers of dense fluid

We present a microscopic model of the interface between liquid water and a hydrophilic, solid surface, as obtained from ab-initio molecular dynamics simulations. In particular, we focused on the (100)surface of cubic SiC, a leading candidate semiconductor for bio-compatible devices. Our results show that, in the liquid in contact with the clean substrate, molecular dissociation occurs in a manner unexpectedly similar to that observed in the gas phase. After full hydroxylation takes place, the formation of a thin ({approx}3 {angstrom})interfacial layer is observed, which has higher density than bulk water and forms stable hydrogen bonds with the substrate. The liquid does not uniformly wet the surface, rather molecules preferably bind along directions parallel to the Si dimer rows. Our calculations also predict that one dimensional confinement between two hydrophilic surfaces at about 1.3 nm distance does not affect the structural and electronic properties of the whole water sample.
Date: January 28, 2005
Creator: Cicero, G; Grossman, J; Galli, G & Catellani, A
System: The UNT Digital Library
Anodic polymerization of vinyl ethylene carbonate in Li-Ion battery electrolyte (open access)

Anodic polymerization of vinyl ethylene carbonate in Li-Ion battery electrolyte

A study of the anodic oxidation of vinyl ethylene carbonate (VEC) was conducted with post-mortem analysis of reaction products by ATR-FTIR and gel permeation chromatography (GPC). The half-wave potential (E1/2) for oxidation of VEC is ca. 3.6 V producing a resistive film on the electrode surface. GPC analysis of the film on a gold electrode produced by anodization of a commercial Li-ion battery electrolyte containing 2 percent VEC at 4.1 V showed the presence of a high molecular weight polymer. IR analysis indicated polycarbonate with alkyl carbonate rings linked by aliphatic methylene and methyl branches.
Date: February 28, 2005
Creator: Chen, Guoying; Zhuang, Guorong V.; Richardson, Thomas J.; Gao, Liu & Ross Jr., Philip N.
System: The UNT Digital Library
Distributed Breadth-First Search with 2-D Partitioning (open access)

Distributed Breadth-First Search with 2-D Partitioning

None
Date: February 28, 2005
Creator: Chow, Edmond; Henderson, Keith & Yoo, Andy
System: The UNT Digital Library
Front Surface Tandem Filters using Sapphire (Al2O3) Substrates for Spectral Control in thermophotovoltaic Energy Conversion Systems (open access)

Front Surface Tandem Filters using Sapphire (Al2O3) Substrates for Spectral Control in thermophotovoltaic Energy Conversion Systems

None
Date: February 28, 2005
Creator: Rahmlow, T. D., Jr.; Lazo-Wasem, J.; Gratrix, E.; Fourspring, P. & DePoy, D.
System: The UNT Digital Library
NMR Detection Using Laser-Polarized Xenon as a DipolarSensor (open access)

NMR Detection Using Laser-Polarized Xenon as a DipolarSensor

Hyperpolarized Xe-129 can be used as a sensor to indirectly detect NMR spectra of heteronuclei that are neither covalently bound nor necessarily in direct contact with the Xe atoms, but coupled through long-range intermolecular dipolar couplings. In order to reintroduce long-range dipolar couplings the sample symmetry has to be broken. This can be done either by an asymmetric sample arrangement, or by breaking the symmetry of the spin magnetization with field gradient pulses. Experiments are performed where only a small fraction of the available Xe-129 magnetization is used for each point, so that a single batch of xenon suffices for the point-by-point acquisition of a heteronuclear NMR spectrum. Examples with H-1 as analyte nucleus show that these methods have the potential to obtain spectra with a resolution that is high enough to determine homonuclear J couplings. The applicability of this technique with remote detection is discussed.
Date: February 28, 2005
Creator: Granwehr, Josef; Urban, Jeffry T.; Trabesinger, Andreas H. & Pines, Alexander
System: The UNT Digital Library
Plasma and Ion Sources in Large Area Coatings: A Review (open access)

Plasma and Ion Sources in Large Area Coatings: A Review

Efficient deposition of high-quality coatings often requires controlled application of excited or ionized particles. These particles are either condensing (film-forming) or assisting by providing energy and momentum to the film growth process, resulting in densification, sputtering/etching, modification of stress, roughness, texture, etc. In this review, the technical means are surveyed enabling large area application of ions and plasmas, with ion energies ranging from a few eV to a few keV. Both semiconductortype large area (single wafer or batch processing with {approx} 1000 cm{sup 2}) and in-line web and glass-coating-type large area (> 10{sup 7} m{sup 2} annually) are considered. Characteristics and differences between plasma and ion sources are explained. The latter include gridded and gridless sources. Many examples are given, including sources based on DC, RF, and microwave discharges, some with special geometries like hollow cathodes and E x B configurations.
Date: February 28, 2005
Creator: Anders, Andre
System: The UNT Digital Library
AFM Morphology Study of Si1-Y GeY:H Films Deposited by LF PE CVD from Silane-Germane with Different (open access)

AFM Morphology Study of Si1-Y GeY:H Films Deposited by LF PE CVD from Silane-Germane with Different

The morphology of Si{sub 1-Y} Ge{sub Y}:H films in the range of Y=0.23 to 0.9 has been studied by AFM. The films were deposited by Low Frequency (LF) PE CVD at substrate temperature T{sub s}=300 C and discharge frequency f=110 kHz from silane+germane mixture with and without, Ar and H{sub 2} dilution. The films were deposited on silicon and glass substrates. AFM images were taken and analyzed for 2 x 2 mm{sup 2} area. All the images demonstrated ''grain'' like structure, which was characterized by the height distribution function F(H) average roughness <H>, standard height deviation Rq, lateral correlation length L{sub c} area distribution function F(s), mean grain area <s>, diameter distribution function F(d), and mean grain diameter <d>. The roughness <H> of the films monotonically increases with Y for all dilutions, but more significantly in the films deposited without dilution. L{sub c} continuously grows with Y in the films deposited without dilution, while more complex behavior L{sub c}(Y) is observed in the films deposited with H- or Ar dilution. The sharpness of F(H) characterized by curtosis {gamma} depends on dilution and the sharpest F(H) are for the films deposited with Ar ({gamma}=5.30,Y=0.23) and without dilution ({gamma}=4.3, Y=0.45). Isothermal annealing …
Date: March 28, 2005
Creator: Sanchez, L & Kosarev, A
System: The UNT Digital Library
Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey (open access)

Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey

Matrix diffusion is an important mechanism for solutetransport in fractured rock. We recently conducted a literature survey onthe effective matrix diffusion coefficient, Dem, a key parameter fordescribing matrix diffusion processes at the field scale. Forty fieldtracer tests at 15 fractured geologic sites were surveyed and selectedfor study, based on data availability and quality. Field-scale Dem valueswere calculated, either directly using data reported in the literature orby reanalyzing the corresponding field tracer tests. Surveyed dataindicate that the effective-matrix-diffusion-coefficient factor FD(defined as the ratio of Dem to the lab-scale matrix diffusioncoefficient [Dem]of the same tracer) is generally larger than one,indicating that the effective matrix diffusion coefficient in the fieldis comparatively larger than the matrix diffusion coefficient at therock-core scale. This larger value could be attributed to the manymass-transfer processes at different scales in naturally heterogeneous,fractured rock systems. Furthermore, we observed a moderate trend towardsystematic increase in the emDFmDDF value with observation scale,indicating that the effective matrix diffusion coefficient is likely tobe statistically scale dependent. The FD value ranges from 1 to 10,000for observation scales from 5 to 2,000 m. At a given scale, the FD valuevaries by two orders of magnitude, reflecting the influence of differingdegrees of fractured rock heterogeneity at different …
Date: March 28, 2005
Creator: Zhou, Quanlin; Liu, Hui Hai; Molz, Fred J.; Zhang, Yingqi & Bodvarsson, Gudmundur S.
System: The UNT Digital Library
Specific Heat Measurements of TiB(2)[subscript] and (6)[superscript]LiF from 0.5 to 30K (open access)

Specific Heat Measurements of TiB(2)[subscript] and (6)[superscript]LiF from 0.5 to 30K

The specific heats of TiB{sub 2} and {sup 6}LiF have been measured from 0.5 to 30 K as part of a larger project in the construction of a neutron spectrometer. For this application, the measured specific heats were used to extrapolate the specific heats down to 0.1 K with lattice, electronic, and Schottky equations for the respective samples. The resultant specific heat values at 0.1 K for TiB{sub 2} and {sup 6}LiF are 4.08 x 10{sup -4} {+-} 0.27 x 10{sup -4} J/K/mol and 9.19 x 10{sup -9} {+-} 0.15 x 10{sup -9} J/K/mol, respectively.
Date: March 28, 2005
Creator: Lang, B. E.; Marcus, H. D.; Woodfield, B. F.; Burger, A.; Utupal, N. R.; Lamberti, V. et al.
System: The UNT Digital Library
E10 Orbifolds (open access)

E10 Orbifolds

We study Z2 orbifolds of M-theory in terms of E10. We find a simple relation between the Z2 action on E10 and the imaginary root that corresponds [hep-th/0401053]to the"twisted sector" branes. We discuss the connection between the Kac-Moody algebra DE10 and the"untwisted" sector, and we demonstrate how DE18 can describe both the untwisted and twisted sectors simultaneously.
Date: April 28, 2005
Creator: Brown, Jeffrey; Ganguli, Surya; Ganor, Ori J. & Helfgott, Craig
System: The UNT Digital Library
Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler (open access)

Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler

A data acquisition technique and relevant program for suppression of one of the systematic effects, namely the ''ghost'' effect, of a second generation long trace profiler (LTP) is described. The ''ghost'' effect arises when there is an unavoidable cross-contamination of the LTP sample and reference signals into one another, leading to a systematic perturbation in the recorded interference patterns and, therefore, a systematic variation of the measured slope trace. Perturbations of about 1-2 {micro}rad have been observed with a cylindrically shaped X-ray mirror. Even stronger ''ghost'' effects show up in an LTP measurement with a mirror having a toroidal surface figure. The developed technique employs separate measurement of the ''ghost''-effect-related interference patterns in the sample and the reference arms and then subtraction of the ''ghost'' patterns from the sample and the reference interference patterns. The procedure preserves the advantage of simultaneously measuring the sample and reference signals. The effectiveness of the technique is illustrated with LTP metrology of a variety of X-ray mirrors.
Date: April 28, 2005
Creator: Yashchuk, Valeriy V.; Irick, Steve C. & MacDowell, Alastair A.
System: The UNT Digital Library