Detection of Hohlraum Target Position for Laser Fusion Experiments (open access)

Detection of Hohlraum Target Position for Laser Fusion Experiments

None
Date: July 6, 2010
Creator: Awwal, A. A.
System: The UNT Digital Library
Image Processing and Control of a Programmable Spatial Light Modulator for Optic Damage Protection (open access)

Image Processing and Control of a Programmable Spatial Light Modulator for Optic Damage Protection

The heart of the National Ignition Facility is a megajoule-class laser system consisting of 192 beams used to drive inertial confinement fusion reactions. A recently installed system of programmable, liquid-crystal-based spatial light modulators adds the capability of arbitrarily shaping the spatial beam profiles in order to enhance operational flexibility. Its primary intended use is for introducing 'blocker' obscurations shadowing isolated flaws on downstream optical elements that would otherwise be damaged by high fluence laser illumination. Because an improperly shaped blocker pattern can lead to equipment damage, both the position and shape of the obscurations must be carefully verified prior to high-fluence operations. An automatic alignment algorithm is used to perform detection and estimation of the imposed blocker centroid positions compared to their intended locations. Furthermore, in order to minimize the spatially-varying nonlinear response of the device, a calibration of the local magnification is performed at multiple sub-image locations. In this paper, we describe the control and associated image processing of this device that helps to enhance the safety and longevity of the overall system.
Date: December 6, 2010
Creator: Awwal, A.; Leach, R.; Brunton, G.; Tse, E.; Matone, J. & Heebner, J.
System: The UNT Digital Library
Nondestructive depth-resolved spectroscopic investigation of the heavily intermixed In2S3/Cu(In,Ga)Se2 interface (open access)

Nondestructive depth-resolved spectroscopic investigation of the heavily intermixed In2S3/Cu(In,Ga)Se2 interface

The chemical structure of the interface between a nominal In2S3 buffer and a Cu(In,Ga)Se2 (CIGSe) thin-film solar cell absorber was investigated by soft x-ray photoelectron and emission spectroscopy. We find a heavily intermixed, complex interface structure, in which Cu diffuses into (and Na through) the buffer layer, while the CIGSe absorber surface/interface region is partially sulfurized. Based on our spectroscopic analysis, a comprehensive picture of the chemical interface structure is proposed.
Date: April 6, 2010
Creator: Bar, Marcus; Barreau, N.; Couzinie-Devy, F.; Pookpanratana, S.; Klaer, J.; Blum, M. et al.
System: The UNT Digital Library
Dynamical Layer Decoupling in a Stripe-ordered, High T_c Superconductor (open access)

Dynamical Layer Decoupling in a Stripe-ordered, High T_c Superconductor

In the stripe-ordered state of a strongly-correlated two-dimensional electronic system, under a set of special circumstances, the superconducting condensate, like the magnetic order, can occur at a non-zero wave-vector corresponding to a spatial period double that of the charge order. In this case, the Josephson coupling between near neighbor planes, especially in a crystal with the special structure of La{sub 2-x}Ba{sub x}CuO{sub 4}, vanishes identically. We propose that this is the underlying cause of the dynamical decoupling of the layers recently observed in transport measurements at x = 1/8.
Date: April 6, 2010
Creator: Berg, E.
System: The UNT Digital Library
Self-consistent solution for proximity effect and Josephson current in ballistic graphene SNS Josephson junctions (open access)

Self-consistent solution for proximity effect and Josephson current in ballistic graphene SNS Josephson junctions

We use a tight-binding Bogoliubov-de Gennes (BdG) formalism to self-consistently calculate the proximity effect, Josephson current, and local density of states in ballistic graphene SNS Josephson junctions. Both short and long junctions, with respect to the superconducting coherence length, are considered, as well as different doping levels of the graphene. We show that self-consistency does not notably change the current-phase relationship derived earlier for short junctions using the non-selfconsistent Dirac-BdG formalism but predict a significantly increased critical current with a stronger junction length dependence. In addition, we show that in junctions with no Fermi level mismatch between the N and S regions superconductivity persists even in the longest junctions we can investigate, indicating a diverging Ginzburg-Landau superconducting coherence length in the normal region.
Date: April 6, 2010
Creator: Black-Schaffer, Annica M.
System: The UNT Digital Library
Layed Perovskite PRBA0.5SR0.5CO205 as High Performance Cathode for Solid Oxide Fuels Using Photon Conducting Electrolyte (open access)

Layed Perovskite PRBA0.5SR0.5CO205 as High Performance Cathode for Solid Oxide Fuels Using Photon Conducting Electrolyte

This paper discusses solid oxide fuel cells, proton conductors, layered perovskite and Cathodes.
Date: May 6, 2010
Creator: Brinkman, K.
System: The UNT Digital Library
The Stability and Electrical Properties of High Temperature Proton Conductors (open access)

The Stability and Electrical Properties of High Temperature Proton Conductors

The morphological and electrical properties of Ba{sub 1-x}Sr{sub x}Ce{sub 0.8}Y{sub 0.2}O{sub 3-{delta}} with x varying from 0 to 1 prepared by a modified Pechini method were investigated as potential high temperature proton conductors. Dense microstructures were achieved for all the samples upon sintering at 1500 C for 5 h. The phase structure analysis indicated that perovskite phase was formed for 0 {le} x {le} 0.2, while for x larger than 0.5, impurity phases of Sr{sub 2}CeO{sub 4} and Y{sub 2}O{sub 3} appeared. The tolerance to H{sub 2}O for the samples improved with the increase in Sr content when exposed to boiling water, while the electrical conductivity decreased from x = 0 to 1. However, the resistance to CO{sub 2} attack at elevated temperatures was not improved within the whole x range studied.
Date: July 6, 2010
Creator: Brinkman, K.
System: The UNT Digital Library
Development of Sensors and Sensing Technology for Hydrogen Fuel Cell Vehicle Applications (open access)

Development of Sensors and Sensing Technology for Hydrogen Fuel Cell Vehicle Applications

One related area of hydrogen fuel cell vehicle (FCV) development that cannot be overlooked is the anticipated requirement for new sensors for both the monitoring and control of the fuel cell's systems and for those devices that will be required for safety. Present day automobiles have dozens of sensors on-board including those for IC engine management/control, sensors for state-of-health monitoring/control of emissions systems, sensors for control of active safety systems, sensors for triggering passive safety systems, and sensors for more mundane tasks such as fluids level monitoring to name the more obvious. The number of sensors continues to grow every few years as a result of safety mandates but also in response to consumer demands for new conveniences and safety features. Some of these devices (e.g. yaw sensors for dynamic stability control systems or tire presure warning RF-based devices) may be used on fuel cell vehicles without any modification. However the use of hydrogen as a fuel will dictate the development of completely new technologies for such requirements as the detection of hydrogen leaks, sensors and systems to continuously monitor hydrogen fuel purity and protect the fuel cell stack from poisoning, and for the important, yet often taken for granted, …
Date: January 6, 2010
Creator: Brosha, E. L.; Sekhar, P. K.; Mukundan, R.; Williamson, T.; Garzon, F. H.; Woo, L. Y. et al.
System: The UNT Digital Library
Erratum: Time-step Considerations in Particle Simulation Algorithms for Coulomb Collisions in Plasmas [B.I. Cohen, A. M. Dimits, A. Friedman, and R. E. Caflisch, IEEE Trans. Plasma Sci. 38, 2394 (2010)] (open access)
The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component of the GFDL global coupled model CM3 (open access)

The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component of the GFDL global coupled model CM3

None
Date: July 6, 2010
Creator: Donner, L. J.; Wyman, B. L.; Hemler, R. S.; Horowitz, L. W.; Ming, Y.; Zhao, M. et al.
System: The UNT Digital Library
Sources and transport systems for low energy extreme of ion implantation (open access)

Sources and transport systems for low energy extreme of ion implantation

For the past seven years a joint research and development effort focusing on the design of steady state, intense ion sources has been in progress with the ultimate goal being to meet the two, energy extreme range needs of mega-electron-volt and 100's of electron-volt ion implanters. However, since the last Fortier is low energy ion implantation, focus of the endeavor has shifted to low energy ion implantation. For boron cluster source development, we started with molecular ions of decaborane (B{sub 10}H{sub 14}), octadecaborane (B{sub 18}H{sub 22}), and presently our focus is on carborane (C{sub 2}B{sub 10}H{sub 12}) ions developing methods for mitigating graphite deposition. Simultaneously, we are developing a pure boron ion source (without a working gas) that can form the basis for a novel, more efficient, plasma immersion source. Our Calutron-Berna ion source was converted into a universal source capable of switching between generating molecular phosphorous P{sub 4}{sup +}, high charge state ions, as well as other types of ions. Additionally, we have developed transport systems capable of transporting a very large variety of ion species, and simulations of a novel gasless/plasmaless ion beam deceleration method were also performed.
Date: June 6, 2010
Creator: Hershcovitch, A.; Batalin, V. A.; Bugaev, A. S.; Gushenets, V. I.; Alexeyenko, O.; Gurkova, E. et al.
System: The UNT Digital Library
Structure of Oxide Nanoparticles in Fe-16Cr MA/ODS Ferritic Steel (open access)

Structure of Oxide Nanoparticles in Fe-16Cr MA/ODS Ferritic Steel

Oxide nanoparticles in Fe-16Cr ODS ferritic steel fabricated by mechanical alloying (MA) method have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. A partial crystallization of oxide nanoparticles was frequently observed in as-fabricated ODS steel. The crystal structure of crystalline oxide particles is identified to be mainly Y{sub 4}Al{sub 2}O{sub 9} (YAM) with a monoclinic structure. Large nanoparticles with a diameter larger than 20 nm tend to be incoherent and have a nearly spherical shape, whereas small nanoparticles with a diameter smaller than 10 nm tend to be coherent or semi-coherent and have faceted boundaries. The oxide nanoparticles become fully crystallized after prolonged annealing at 900 C. These results lead us to propose a three-stage formation mechanism of oxide nanoparticles in MA/ODS steels.
Date: April 6, 2010
Creator: Hsiung, L; Fluss, M & Kimura, A
System: The UNT Digital Library
Using Quasi-Monoenergetic Photon Sources to Probe Photo-Fission Resonances (open access)

Using Quasi-Monoenergetic Photon Sources to Probe Photo-Fission Resonances

None
Date: August 6, 2010
Creator: Johnson, M. S.; Hall, J. M.; McNabb, D. P.; Tuffley, M.; Ahmed, M.; Stave, S. et al.
System: The UNT Digital Library
Development of Characterization Technology for Fault Zone Hydrology (open access)

Development of Characterization Technology for Fault Zone Hydrology

Several deep trenches were cut, and a number of geophysical surveys were conducted across the Wildcat Fault in the hills east of Berkeley, California. The Wildcat Fault is believed to be a strike-slip fault and a member of the Hayward Fault System, with over 10 km of displacement. So far, three boreholes of ~;; 150m deep have been core-drilled and borehole geophysical logs were conducted. The rocks are extensively sheared and fractured; gouges were observed at several depths and a thick cataclasitic zone was also observed. While confirming some earlier, published conclusions from shallow observations about Wildcat, some unexpected findings were encountered. Preliminary analysis indicates that Wildcat near the field site consists of multiple faults. The hydraulic test data suggest the dual properties of the hydrologic structure of the fault zone. A fourth borehole is planned to penetrate the main fault believed to lie in-between the holes. The main philosophy behind our approach for the hydrologic characterization of such a complex fractured system is to let the system take its own average and monitor a long term behavior instead of collecting a multitude of data at small length and time scales, or at a discrete fracture scale and to ?up-scale,? …
Date: August 6, 2010
Creator: Karasaki, Kenzi; Onishi, Tiemi; Gasperikova, Erika; Goto, Junichi; Tsuchi, Hiroyuki; Miwa, Tadashi et al.
System: The UNT Digital Library
Recent Developments in High-Harmonic Fast Wave Physics in NSTX (open access)

Recent Developments in High-Harmonic Fast Wave Physics in NSTX

Understanding the interaction between ion cyclotron range of frequency (ICRF) fast waves and the fast-ions created by neutral beam injection (NBI) is critical for future devices such as ITER, which rely on a combination ICRF and NBI. Experiments in NSTX which use 30 MHz High-Harmonic Fast-Wave (HHFW) ICRF and NBI heating show a competition between electron heating via Landau damping and transit-time magnetic pumping, and radio-frequency wave acceleration of NBI generated fast ions. Understanding and mitigating some of the power loss mechanisms outside the last closed flux surface (LCFS) has resulted in improved HHFW heating inside the LCFS. Nevertheless a significant fraction of the HHFW power is diverted away from the enclosed plasma. Part of this power is observed locally on the divertor. Experimental observations point toward the radio-frequency (RF) excitation of surface waves, which disperse wave power outside the LCFS, as a leading loss mechanism. Lithium coatings lower the density at the antenna, thereby moving the critical density for perpendicular fast-wave propagation away from the antenna and surrounding material surfaces. Visible and infrared imaging reveal flows of RF power along open field lines into the divertor region. In L-mode -- low average NBI power -- conditions, the fast-ion D-alpha …
Date: October 6, 2010
Creator: LeBlanc, B. P.; Bell, R. E.; Bonoli, P.; Harvey, R.; Heidbrink, W. W.; Hosea, J. C. et al.
System: The UNT Digital Library
Water Induced Surface Reconstruction of the Oxygen (2x1) covered Ru(0001) (open access)

Water Induced Surface Reconstruction of the Oxygen (2x1) covered Ru(0001)

Low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the adsorption of water on a Ru(0001) surface covered with half monolayer of oxygen. The oxygen atoms occupy hcp sites in an ordered structure with (2x1) periodicity. DFT predicts that water is weakly bound to the unmodified surface, 86 meV compared to the ~;;200 meV water-water H-bond. Instead, we found that water adsorption causes a shift of half of the oxygen atoms from hcp sites to fcc sites, creating a honeycomb structure where water molecules bind strongly to the exposed Ru atoms. The energy cost of reconstructing the oxygen overlayer, around 230 meV per displaced oxygen atom, is more than compensated by the larger adsorption energy of water on the newly exposed Ru atoms. Water forms hydrogen bonds with the fcc O atoms in a (4x2) superstructure due to alternating orientations of the molecules. Heating to 185 K results in the complete desorption of the water layer, leaving behind the oxygen honeycomb structure, which is metastable relative to the original (2x1). This stable structure is not recovered until after heating to temperatures close to 260K.
Date: August 6, 2010
Creator: Maier, Sabine; Cabrera-Sanfelix, Pepa; Stass, Ingeborg; Sanchez-Portal, Daniel; Arnau, Andres & Salmeron, Miquel
System: The UNT Digital Library
Fish Tales (open access)

Fish Tales

This talk is about fishing and the friendships that have resulted in its pursuit. It is also about theoretical physics, and the relationship of imagination and fantasy to the establishment of ideas about nature. Fishermen, like theoretical physicists, are well known for their inventive imaginations. Perhaps neither are as clever as sailors, who conceived of the mermaid. If one doubts the power of this fantasy, one should remember the ghosts of the many sailors who drowned pursuing these young nymphs. An extraordinary painting by J. Waterhouse is shown as Fig. 1. The enchantment of a mermaid must reflect an extraordinary excess of imagination on the part of the sailor, perhaps together with an impractical turn of mind. A consummated relationship with a mermaid is after all, by its very nature a fantasy incapable of realization. To a theoretical physicist, she is symbolic of many ideas we develop. There are many truths known to fisherman in which one might also find parallels to the goals of scientists: (1) A fish is the only animal that keeps growing after its death; (2) Nothing makes a fish bigger than almost being caught; (3) ''...of all the liars among mankind, the fisherman is the …
Date: July 6, 2010
Creator: McLerran, L.
System: The UNT Digital Library
A Case for the Use of 3-D Attenuation Models in Ground Motion and Seismic Hazard Assessment (open access)

A Case for the Use of 3-D Attenuation Models in Ground Motion and Seismic Hazard Assessment

None
Date: December 6, 2010
Creator: Pasyanos, M E
System: The UNT Digital Library
2010 GRC VIBRATIONAL SPECTROSCOPY AUGUST 1 - AUGUST 6, 2010 (open access)

2010 GRC VIBRATIONAL SPECTROSCOPY AUGUST 1 - AUGUST 6, 2010

The Vibrational Spectroscopy conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and at interfaces. The conference explores the wide range of state-of-the-art techniques based on vibrational motion. These techniques span the fields of time-domain, high-resolution frequency-domain, spatially-resolved, nonlinear and multidimensional spectroscopies. The conference highlights the application of these techniques in chemistry, materials, biology, and medicine. The theory of molecular vibrational motion and its connection to spectroscopic signatures and chemical reaction dynamics is the third major theme of the meeting. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of molecular systems ranging from small polyatomic molecules to large biomolecules and nanomaterials.
Date: August 6, 2010
Creator: Pate, Brooks
System: The UNT Digital Library
Distinguishing Patterns of Charge Order: Stripes or Checkerboards (open access)

Distinguishing Patterns of Charge Order: Stripes or Checkerboards

In two dimensions, quenched disorder always rounds transitions involving the breaking of spatial symmetries so, in practice, it can often be difficult to infer what form the symmetry breaking would take in the 'ideal,' zero disorder limit. We discuss methods of data analysis which can be useful for making such inferences, and apply them to the problem of determining whether the preferred order in the cuprates is 'stripes' or 'checkerboards.' In many cases we show that the experiments clearly indicate stripe order, while in others (where the observed correlation length is short), the answer is presently uncertain.
Date: April 6, 2010
Creator: Robertson, J.A.
System: The UNT Digital Library
2010 ELECTRODEPOSITION GORDON RESEARCH CONFERENCE, AUGUST 1-6, 2010 (open access)

2010 ELECTRODEPOSITION GORDON RESEARCH CONFERENCE, AUGUST 1-6, 2010

The 2010 Gordon Conference on Electrodeposition will present cutting-edge research on electrodeposition with emphasis on (i) advances in basic science, (ii) developments in next-generation technologies, and (iii) new and emerging areas. The Conference will feature a wide range of topics, from atomic scale processes, nucleation and growth, thin film deposition, and electrocrystallization, to applications of electrodeposition in devices including microelectronics, solar energy, and power sources. The Conference will bring together investigators from a wide range of scientific disciplines, including chemical engineering, materials science and engineering, physics, and chemistry. The Conference will feature invited speakers at the forefront of the field, and a late-breaking news session that will provide the opportunity for graduate students, post-docs, and junior faculty to participate. The collegial atmosphere of this Conference, with scientific talks and poster sessions, as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to discuss current issues and promotes cross-disciplinary collaborations in the various research areas represented. The Conference will be held at Colby-Sawyer College, located in the Mt. Kearsarge-Lake Sunapee Region of New Hampshire. The surrounding mountains, forests, and lakes provide a beautiful setting for this conference. The attendance is limited …
Date: August 6, 2010
Creator: Searson, Peter
System: The UNT Digital Library
Theory of quantum metal to superconductor transitions in highly conducting systems (open access)

Theory of quantum metal to superconductor transitions in highly conducting systems

We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.
Date: April 6, 2010
Creator: Spivak, B.
System: The UNT Digital Library
Mesoscale Modeling of LX-17 Under Isentropic Compression (open access)

Mesoscale Modeling of LX-17 Under Isentropic Compression

Mesoscale simulations of LX-17 incorporating different equilibrium mixture models were used to investigate the unreacted equation-of-state (UEOS) of TATB. Candidate TATB UEOS were calculated using the equilibrium mixture models and benchmarked with mesoscale simulations of isentropic compression experiments (ICE). X-ray computed tomography (XRCT) data provided the basis for initializing the simulations with realistic microstructural details. Three equilibrium mixture models were used in this study. The single constituent with conservation equations (SCCE) model was based on a mass-fraction weighted specific volume and the conservation of mass, momentum, and energy. The single constituent equation-of-state (SCEOS) model was based on a mass-fraction weighted specific volume and the equation-of-state of the constituents. The kinetic energy averaging (KEA) model was based on a mass-fraction weighted particle velocity mixture rule and the conservation equations. The SCEOS model yielded the stiffest TATB EOS (0.121{micro} + 0.4958{micro}{sup 2} + 2.0473{micro}{sup 3}) and, when incorporated in mesoscale simulations of the ICE, demonstrated the best agreement with VISAR velocity data for both specimen thicknesses. The SCCE model yielded a relatively more compliant EOS (0.1999{micro}-0.6967{micro}{sup 2} + 4.9546{micro}{sup 3}) and the KEA model yielded the most compliant EOS (0.1999{micro}-0.6967{micro}{sup 2}+4.9546{micro}{sup 3}) of all the equilibrium mixture models. Mesoscale simulations with the …
Date: March 6, 2010
Creator: Springer, H K; Willey, T M; Friedman, G; Fried, L E; Vandersall, K S & Baer, M R
System: The UNT Digital Library
Satellite Collision Modeling with Physics-Based Hydrocodes: Debris Generation Predictions of the Iridium-Cosmos Collision Event and Other Impact Events (open access)

Satellite Collision Modeling with Physics-Based Hydrocodes: Debris Generation Predictions of the Iridium-Cosmos Collision Event and Other Impact Events

Satellite collision debris poses risks to existing space assets and future space missions. Predictive models of debris generated from these hypervelocity collisions are critical for developing accurate space situational awareness tools and effective mitigation strategies. Hypervelocity collisions involve complex phenomenon that spans several time- and length-scales. We have developed a satellite collision debris modeling approach consisting of a Lagrangian hydrocode enriched with smooth particle hydrodynamics (SPH), advanced material failure models, detailed satellite mesh models, and massively parallel computers. These computational studies enable us to investigate the influence of satellite center-of-mass (CM) overlap and orientation, relative velocity, and material composition on the size, velocity, and material type distributions of collision debris. We have applied our debris modeling capability to the recent Iridium 33-Cosmos 2251 collision event. While the relative velocity was well understood in this event, the degree of satellite CM overlap and orientation was ill-defined. In our simulations, we varied the collision CM overlap and orientation of the satellites from nearly maximum overlap to partial overlap on the outermost extents of the satellites (i.e, solar panels and gravity boom). As expected, we found that with increased satellite overlap, the overall debris cloud mass and momentum (transfer) increases, the average debris …
Date: September 6, 2010
Creator: Springer, H. K.; Miller, W. O.; Levatin, J. L.; Pertica, A. J. & Olivier, S. S.
System: The UNT Digital Library