Commissioning of the LCLS Linac and Bunch Compressors (open access)

Commissioning of the LCLS Linac and Bunch Compressors

The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project under construction at SLAC [1]. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor, was commissioned in the spring and summer of 2007. The second phase of commissioning, including the second bunch compressor and various main linac modifications, was completed in January through August of 2008. We report here on experience gained during this second phase of machine commissioning, including the injector, the first and second bunch compressor stages, the linac up to 14 GeV, and beam stability measurements. The final commissioning phase, including the undulator and the long transport line from the linac, is set to begin in December 2008, with first light expected in July 2009.
Date: August 20, 2008
Creator: Akre, R.; Brachmann, A.; Decker, F.-J.; Ding, Y.; Dowell, D.; Emma#, P. et al.
System: The UNT Digital Library
Testing Short Samples of ITER Conductors and Projection of Their Performance in ITER Magnets (open access)

Testing Short Samples of ITER Conductors and Projection of Their Performance in ITER Magnets

Qualification of the ITER conductor is absolutely necessary. Testing large scale conductors is expensive and time consuming. To test straight 3-4m long samples in a bore of a split solenoid is a relatively economical way in comparison with fabrication of a coil to be tested in a bore of a background field solenoid. However, testing short sample may give ambiguous results due to different constraints in current redistribution in the cable or other end effects which are not present in the large magnet. This paper discusses processes taking place in the ITER conductor, conditions when conductor performance could be distorted and possible signal processing to deduce behavior of ITER conductors in ITER magnets from the test data.
Date: August 20, 2007
Creator: Martovetsky, N. N.
System: The UNT Digital Library
Measurement of Branching Fractions and CP and Isospin Asymmetries of B -> K* g (open access)

Measurement of Branching Fractions and CP and Isospin Asymmetries of B -> K* g

We present a preliminary analysis of the decays B{sup 0} {yields} K*{sup 0}{gamma} and B{sup +} {yields} K*{sup +}{gamma} using a sample of 383 million B{bar B} events collected with the BABAR detector at the PEP-II asymmetric energy B factory. We measure the branching fractions {Beta}(B{sup 0} {yields} K*{sup 0}{gamma}) = (4.58 {+-} 0.10 {+-} 0.16) x 10{sup -5} and {Beta}(B{sup +} {yields} K*{sup +}{gamma}) = (4.73 {+-} 0.15 {+-} 0.17) x 10{sup -5}. We measure the direct CP asymmetry to be -0.043 < {Alpha}(B {yields} K*{gamma}) < 0.025 and the isospin asymmetry to be -0.021 < {Delta}{sub 0-} < 0.079, where the limits are determined at the 90% confidence interval and include both the statistical and systematic uncertainties.
Date: August 20, 2008
Creator: Yarritu, A.
System: The UNT Digital Library
2007 Molecular & Cellular Bioenergetics (June 17-22, 2007) (open access)

2007 Molecular & Cellular Bioenergetics (June 17-22, 2007)

This Report describes Molecular & Cellular Bioenergetics.
Date: August 20, 2008
Creator: Fevzi Daldal, Nancy Ryan Gray
System: The UNT Digital Library
Update of Time-Dependent CP Asymmetry Measurements in b to c-cbar-s Decays (open access)

Update of Time-Dependent CP Asymmetry Measurements in b to c-cbar-s Decays

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465 {+-} 5) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II B factory. The time-dependent CP asymmetry parameters measured from J/{psi}K{sub S}{sup 0}, J/{psi}K{sub L}{sup 0}, {psi}(2S)K{sub S}{sup 0}, {chi}{sub c1}K{sub S}{sup 0}, {eta}{sub c}K{sub S}{sup 0}, and J/{psi}K*{sup 0} decays are: (1) C{sub f} = 0.026 {+-} 0.020(stat) {+-} 0.016(syst); and (2) S{sub f} = 0.691 {+-} 0.029(stat) {+-} 0.014(syst).
Date: August 20, 2008
Creator: Aubert, B.
System: The UNT Digital Library
A fourth order accurate adaptive mesh refinement method forpoisson's equation (open access)

A fourth order accurate adaptive mesh refinement method forpoisson's equation

We present a block-structured adaptive mesh refinement (AMR) method for computing solutions to Poisson's equation in two and three dimensions. It is based on a conservative, finite-volume formulation of the classical Mehrstellen methods. This is combined with finite volume AMR discretizations to obtain a method that is fourth-order accurate in solution error, and with easily verifiable solvability conditions for Neumann and periodic boundary conditions.
Date: August 20, 2004
Creator: Barad, Michael & Colella, Phillip
System: The UNT Digital Library
Comparative study of Ti and Ni clusters from first principles (open access)

Comparative study of Ti and Ni clusters from first principles

Icosahedral clusters in Ti and Ni are studied with first-principles density functional calculations. We find significant distortion on the Ti icosahedron caused by the strong interaction between surface atoms on the icosahedron but not between the center atom and surface atoms, whereas no such distortion is observed on Ni clusters. In addition, distortion becomes more severe when atoms are added to the Ti13 cluster resulting in short bonds. Such distorted icosahedra having short bonds are essentially to explain the structure factor of Ti liquid obtained in experiment.
Date: August 20, 2007
Creator: Lee, B & Lee, G W
System: The UNT Digital Library
A Comparison of Photoresist Resolution Metrics using 193 nm and EUV Lithography (open access)

A Comparison of Photoresist Resolution Metrics using 193 nm and EUV Lithography

Image blur due to chemical amplification represents a fundamental limit to photoresist performance and manifests itself in many aspects of lithographic performance. Substantial progress has been made in linking image blur with simple resolution metrics using EUV lithography. In this presentation, they examine performance of 193 nm resist and EUV resist systems using modulation transfer function, corner rounding, and other resolution metrics. In particular, they focus on cross-comparisons in which selected EUV and 193 nm resist are evaluated using both EUV and 193 nm lithography. Simulation methods linking 193 nm and EUV performance will be described as well. Results from simulation indicate that image blur in current generation 193 nm photoresists is comparable to that of many EUV resists, but that ultra-low diffusion materials designs used in very high resolution EUV resists can result in substantially lower blur. In addition to detailing correlations between EUV and 193 nm experimental methods, they discuss their utility in assessing performance needs of future generation photoresists.
Date: August 20, 2007
Creator: Jones, Juanita; Pathak, Piyush; Wallow, Thomas; LaFontaine, Bruno; Deng, Yunfei; Kim, Ryoung-han et al.
System: The UNT Digital Library
Optimization of the cooling profile to achieve crack-free Yb:S-FAP crystals (open access)

Optimization of the cooling profile to achieve crack-free Yb:S-FAP crystals

Yb:S-FAP [Yb{sup 3+}:Sr{sub 5}(PO{sub 4}){sub 3}F] crystals are an important gain medium for diode-pumped laser applications. Growth of 7.0 cm diameter Yb:S-FAP crystals utilizing the Czochralski (CZ) method from SrF{sub 2}-rich melts often encounter cracks during the post growth cool down stage. To suppress cracking during cool down, a numerical simulation of the growth system was used to understand the correlation between the furnace power during cool down and the radial temperature differences within the crystal. The critical radial temperature difference, above which the crystal cracks, has been determined by benchmarking the simulation results against experimental observations. Based on this comparison, an optimal three-stage ramp-down profile was implemented and produced high quality, crack-free Yb:S-FAP crystals.
Date: August 20, 2007
Creator: Fang, H; Qiu, S; Kheng, L; Schaffers, K; Tassano, J; Caird, J et al.
System: The UNT Digital Library
Evidence for CP violation in B0 to J/Psi pi0 Decays (open access)

Evidence for CP violation in B0 to J/Psi pi0 Decays

None
Date: August 20, 2008
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Modeling Leaking Gas Plume Migration (open access)

Modeling Leaking Gas Plume Migration

In this study, we obtain simple estimates of 1-D plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. Application of the Buckley-Leverett model to describe buoyancy-driven countercurrent flow of two immiscible phases leads to a transparent theory predicting the evolution of the plume. We obtain that the plume does not migrate upward like a gas bubble in bulk water. Rather, it stretches upward until it reaches a seal or until the fluids become immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration that does not lend itself to a simple analytical solution (Silin et al., 2006). The range of applicability of the simplified solution is assessed and provided. This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. One of the potential problems associated with the geologic method of sequestration is leakage of CO{sub 2} from the underground storage reservoir into sources of drinking water. Ideally, the injected green-house gases will stay in the injection …
Date: August 20, 2007
Creator: Silin, Dmitriy; Patzek, Tad & Benson, Sally M.
System: The UNT Digital Library
On Yang--Mills Theories with Chiral Matter at Strong Coupling (open access)

On Yang--Mills Theories with Chiral Matter at Strong Coupling

Strong coupling dynamics of Yang-Mills theories with chiral fermion content remained largely elusive despite much effort over the years. In this work, we propose a dynamical framework in which we can address non-perturbative properties of chiral, non-supersymmetric gauge theories, in particular, chiral quiver theories on S{sub 1} x R{sub 3}. Double-trace deformations are used to stabilize the center-symmetric vacuum. This allows one to smoothly connect smaller(S{sub 1}) to larger(S{sub 1}) physics (R{sub 4} is the limiting case) where the double-trace deformations are switched off. In particular, occurrence of the mass gap in the gauge sector and linear confinement due to bions are analytically demonstrated. We find the pattern of the chiral symmetry realization which depends on the structure of the ring operators, a novel class of topological excitations. The deformed chiral theory, unlike the undeformed one, satisfies volume independence down to arbitrarily small volumes (a working Eguchi-Kawai reduction) in the large N limit. This equivalence, may open new perspectives on strong coupling chiral gauge theories on R{sub 4}.
Date: August 20, 2008
Creator: Shifman, M.; /Minnesota U., Theor. Phys. Inst. /Saclay, SPhT; Unsal, Mithat & /SLAC /Stanford U., Phys. Dept.
System: The UNT Digital Library
Materials Science at the Extremes of Pressure and Strain Rate (open access)

Materials Science at the Extremes of Pressure and Strain Rate

Solid state experiments at very high pressures and strain rates are possible on high power laser facilities, albeit over brief intervals of time and spatial small scales. A new shockless drive has been developed on the Omega laser. VISAR measurements establish the high strain rates, 10{sup 7}-10{sup 8} s{sup -1}. Solid-state strength is inferred using the Rayleigh-Taylor instability as a ''diagnostic''. Temperature and compression in polycrystalline samples can be deduced from EXAFS measurements. Lattice response can be inferred from time-resolved x-ray diffraction. Deformation mechanisms can be identified by examining recovered samples. We will briefly review this new area of laser-based materials science research, then present a path forward for carrying these solid-state experiments to much higher pressures, P >> 1 Mbar, on the NIF laser facility.
Date: August 20, 2003
Creator: Remington, B. A.; Cavallo, R. M.; Edwards, M. J.; Lasinski, B. F.; Lorenz, K. T.; Lorenzana, H. E. et al.
System: The UNT Digital Library
NUCLEAR-OPTICAL CONVERTERS FOR NEUTRON DETECTION (open access)

NUCLEAR-OPTICAL CONVERTERS FOR NEUTRON DETECTION

Nuclear-optical converters (NOC) are fission chambers based upon fission fragment energy conversion to optical radiation in gas luminescent media. The All-Russia Scientific Research Institute of Experimental Physics (VNIIEF) has demonstrated that it is possible to construct nuclear-optical converters with characteristics appropriate for a wide-range of measuring applications including neutron detection in nuclear power plants. These detectors may be used a number of different modes: pulse count, luminescent (equivalent to current mode in ionization detectors), and lasing (essentially a neutron switch). NOCs offer a number of potential advantages over ionization detectors. The detectors require no power supply. Signals are transmitted via light-pipe or fiber optics rather than insulated electrical cable. The detectors are less sensitive to gamma radiation. NOC can produce large signals, obviating the need for pre-amplifiers near the detector. It is possible to construct a single detector which measures flux at many discrete points and at the same time provides total flux along a line containing these discrete points. This paper describes the construction and testing of NOC at VNIIEF; the range of characteristics thought to be reasonably attainable with nuclear-optical converters, and possible applications to nuclear power plant instrumentation.
Date: August 20, 2004
Creator: Sinyanskii, A A; Melnikov, S P; Dovbysh, L E & Johnson, G L
System: The UNT Digital Library
Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds (open access)

Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds

Spatially Resolved X-Ray Diffraction (SRXRD) has been used to identify a previously unobserved low temperature ferrite ({delta})/austenite({gamma}) phase transformation in the heat affected zone (HAZ) of 2205 Duplex Stainless Steel (DSS) welds. In this ''ferrite dip'' transformation, the ferrite transforms to austenite during heating to peak temperatures on the order of 750 C, and re-transforms to ferrite during cooling, resulting in a ferrite volume fraction equivalent to that in the base metal. Time Resolved X-Ray Diffraction (TRXRD) and laser dilatometry measurements during Gleeble{reg_sign} thermal simulations are performed in order to verify the existence of this low temperature phase transformation. Thermodynamic and kinetic models for phase transformations, including both local-equilibrium and para-equilibrium diffusion controlled growth, show that diffusion of substitutional alloying elements does not provide a reasonable explanation for the experimental observations. On the other hand, the diffusion of interstitial alloying elements may be rapid enough to explain this behavior. Based on both the experimental and modeling results, two mechanisms for the ''ferrite dip'' transformation, including the formation and decomposition of secondary austenite and an athermal martensitic-type transformation of ferrite to austenite, are considered.
Date: August 20, 2003
Creator: Palmer, T A; Elmer, J W; Babu, S S & Vitek, J M
System: The UNT Digital Library
Synthesis and Characterization of Novel Preceramic Polymer for SiC (open access)

Synthesis and Characterization of Novel Preceramic Polymer for SiC

Polyphenylcarbosilane as a novel preceramic polymer for SiC was synthesized from thermal rearrangement of polymethylphenylsilane around 350 C {approx} 430 C. Characterization of synthesized polyphenylcarbosilane was performed with {sup 29}Si, {sup 13}C, {sup 1}H NMR, FT-IR, TG, XRD, and GPC analysis. From FT-IR data, the band at 1035 cm{sup -1} was very strong and assigned to CH{sub 2} bending vibration in Si-CH{sub 2}-Si group, indicating the formation of the polyphenylcarbosilane. The average of the molecular weight (M{sub w}) of the polyphenylcarbosilane synthesized was 2,500 and easily dissolves in an organic solvent. TGA data indicates that polyphenylcarbosilane is thermally stable up to 400 C. However, the rapid weight loss occurs above 400 C due to the pyrolysis of polyphenylcarbosilane, and the diffraction peak of pyrolysis residue at 1200 C corresponds to the {beta}-SiC ceramic. The ceramic yield calculated from TGA is approximately 65%.
Date: August 20, 2009
Creator: Lee, Y. J.; Lee, J. H.; Kim, S. R.; Kwon, W. T.; Oh, H.; Klepeis, J. P. et al.
System: The UNT Digital Library
VPP ANNUAL SELF-EVALUATION BY THE NUMBERS (open access)

VPP ANNUAL SELF-EVALUATION BY THE NUMBERS

None
Date: August 20, 2009
Creator: JE, GRIFFITH
System: The UNT Digital Library
What Can DMIS 5.2 Do For You? (open access)

What Can DMIS 5.2 Do For You?

The Dimensional Measuring Interface Standard (DMIS) is the first data interoperability protocol standard created specifically for dimensional metrology. DMIS applications are multi-facetted. The standard can behave as a coordinate metrology language to execute measurement part programs, or it can be used as a neutral data exchange mechanism for part programs and measurement results. DMIS is full featured and has many successful implementations. It also has a strong reputation as a progressive standard, one that has been responsive to user needs and technology advances. It is maintained and improved upon by a volunteer committee, the DMIS Standards Committee (DSC), under the auspices of the Dimensional Metrology Standards Consortium (DMSC Inc.). DMIS has progressed as its eighth version and its sixth as a national and/or international standard. Some notable advances of DMIS have included: • support for thin-walled (i.e., sheet-metal) measurements • alignment with American and International tolerancing standards • complete suite of measure features • harmonization with complementary standards and specifications • extension of additional sensors and scanning processes • introduction of measurement uncertainty computations • tighter CAD associativity • enhancements for multi-axis scanning • provisioning for functional subsets (application profiles) • progression of conformance class validations • designation of key …
Date: August 20, 2009
Creator: Brown, Curtis W.
System: The UNT Digital Library
Thoughts on Incorporating HPRF in a Linear Cooling Channel (open access)

Thoughts on Incorporating HPRF in a Linear Cooling Channel

We discuss a possible implementation of high-pressure gas-filled RF (HPRF) cavities in a linear cooling channel for muons and some of the technical issues that must be dealt with. The approach we describe is a hybrid approach that uses high-pressure hydrogen gas to avoid cavity breakdown, along with discrete LiH absorbers to provide the majority of the energy loss. Initial simulations show that the channel performs as well as the original vacuum RF channel while potentially avoiding the degradation in RF gradient associated with the strong magnetic field in the cooling channel.
Date: August 20, 2009
Creator: Gallardo, Juan C. & Zisman, Michael S
System: The UNT Digital Library
Long-term Observations of the Convective Boundary Layer Using Insect Radar Returns at the SGP ARM Climate Research Facility (open access)

Long-term Observations of the Convective Boundary Layer Using Insect Radar Returns at the SGP ARM Climate Research Facility

A long-term study of the turbulent structure of the convective boundary layer (CBL) at the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Climate Research Facility is presented. Doppler velocity measurements from insects occupying the lowest 2 km of the boundary layer during summer months are used to map the vertical velocity component in the CBL. The observations cover four summer periods (2004-08) and are classified into cloudy and clear boundary layer conditions. Profiles of vertical velocity variance, skewness, and mass flux are estimated to study the daytime evolution of the convective boundary layer during these conditions. A conditional sampling method is applied to the original Doppler velocity dataset to extract coherent vertical velocity structures and to examine plume dimension and contribution to the turbulent transport. Overall, the derived turbulent statistics are consistent with previous aircraft and lidar observations. The observations provide unique insight into the daytime evolution of the convective boundary layer and the role of increased cloudiness in the turbulent budget of the subcloud layer. Coherent structures (plumes-thermals) are found to be responsible for more than 80% of the total turbulent transport resolved by the cloud radar system. The extended dataset is suitable …
Date: August 20, 2009
Creator: Chandra, A. S.; Kollias, P.; Giangrande, S. E. & Klein, S.. A.
System: The UNT Digital Library
ENERGY MODULATION OF THE ELECTRONS BY THE LASER FIELD IN THEWIGGLER MAGNET: ANALYSIS AND EXPERIMENT (open access)

ENERGY MODULATION OF THE ELECTRONS BY THE LASER FIELD IN THEWIGGLER MAGNET: ANALYSIS AND EXPERIMENT

Energy modulation of the electron beam after the interactionwith the laser field in the wiggler magnet can be calculated usinginterference of the laser field and the field of spontaneous emission inthe far field region of wiggler radiation. Quite often this approachgives a deeper insight on the process than traditional calculations wherethe effect of the laser field on the electron energy is integrated alongthe electron trajectory in the wiggler. We demonstrate it by showing theagreement between the analytical model and the experiment involvingwiggler scan measurements with large detuning from the FEL resonanceproducing more than one order of magnitude variations in the amplitude ofthe energy modulation. The high sensitivity was achieved using the THzradiation from a sub-mm dip in the electron density that energy modulatedelectrons leave behind while propagating along the storage ring lattice.All measurements were performed at the BESSY-II electron storagering.
Date: August 20, 2006
Creator: Zholents, A.A. & Holldack, K.
System: The UNT Digital Library
Hydrogen Safety Issues Compared to Safety Issues with Methane and Propane (open access)

Hydrogen Safety Issues Compared to Safety Issues with Methane and Propane

The hydrogen economy is not possible if the safety standards currently applied to liquid hydrogen and hydrogen gas by many laboratories are applied to devices that use either liquid or gaseous hydrogen. Methane and propane are commonly used by ordinary people without the special training. This report asks, 'How is hydrogen different from flammable gasses that are commonly being used all over the world?' This report compares the properties of hydrogen, methane and propane and how these properties may relate to safety when they are used in both the liquid and gaseous state. Through such an analysis, sensible safety standards for the large-scale (or even small-scale) use of liquid and gaseous hydrogen systems can be developed. This paper is meant to promote discussion of issues related to hydrogen safety so that engineers designing equipment can factor sensible safety standards into their designs.
Date: August 20, 2005
Creator: Green, Michael A.
System: The UNT Digital Library
EMPLOYEE-LED SAFETY COMMITTEES (open access)

EMPLOYEE-LED SAFETY COMMITTEES

None
Date: August 20, 2009
Creator: JE, GRIFFITH
System: The UNT Digital Library
The organizing principle: microenvironmental influences in the normal and malignant breast (open access)

The organizing principle: microenvironmental influences in the normal and malignant breast

The current paradigm for cancer initiation and progression rests on the groundbreaking discoveries of oncogenes and tumor suppressor genes. This framework has revealed much about the role of genetic alterations in the underlying signaling pathways central to normal cellular function and to tumor progression. However, it is clear that single gene theories or even sequential acquisition of mutations underestimate the nature of the genetic and epigenetic changes in tumors, and do not account for the observation that many cancer susceptibility genes (e.g. BRCA1, APC) show a high degree of tissue specificity in their association with neoplastic transformation. Therefore, the cellular and tissue context itself must confer additional and crucial information necessary for mutated genes to exert their influence. A considerable body of evidence now shows that cell - cell and cell - extracellular matrix (ECM) interactions are essential organizing principles that help define the nature of the tissue context, and play a crucial role in regulating homeostasis and tissue specificity. How this context determines functional integrity, and how its loss can lead to malignancy, appears to have much to do with tissue structure and polarity.
Date: August 20, 2002
Creator: Bissell, Mina; Radisky, Derek C.; Rizki, Aylin; Weaver, Valerie M. & Petersen, Ole W.
System: The UNT Digital Library