Blue and Green Light? Wavelength Scaling for NIF (open access)

Blue and Green Light? Wavelength Scaling for NIF

Use of the National Ignition Facility to also output frequency-doubled (.53{micro}m) laser light would allow significantly more energy to be delivered to targets as well as significantly greater bandwidth for beam smoothing. This green light option could provide access to new ICF target designs and a wider range of plasma conditions for other applications. The wavelength scaling of the interaction physics is a key issue in assessing this green light option. Wavelength scaling theory based on the collisionless plasma approximation is explored, and some limitations associated with plasma collisionality are examined. Important features of the wavelength scaling are tested using the current data base, which is growing. It appears that, with modest restrictions, .53{micro}m light couples with targets as well as .35{micro}m light does. A more quantitative understanding of the beneficial effects of SSD on the interaction physics is needed for both .53{micro}m and .35{micro}m light.
Date: August 21, 2003
Creator: Suter, L.; Miller, M.; Moody, J. & Kruer, W.
Object Type: Article
System: The UNT Digital Library
A Rule-Based Framework for Gene Regulation Pathways Discovery (open access)

A Rule-Based Framework for Gene Regulation Pathways Discovery

We present novel approach to discover the rules that govern gene regulation mechanisms. The method is based on supervised machine learning and is designed to reveal relationships between transcription factors and gene promoters. As the representation of the gene regulatory circuit we have chosen a special form of IF-THEN rules associating certain features (a generalized idea of a Transcription Factor Binding Site) in gene promoters with specific gene expression profiles.
Date: July 21, 2003
Creator: Wilczynski, B; Hvidsten, T; Kryshtafovych, A; Stubbs, L; Komorowski, J & Fidelis, K
Object Type: Article
System: The UNT Digital Library
The Factory Approach to Creating TSTT Meshes (open access)

The Factory Approach to Creating TSTT Meshes

The factory approach (a.k.a. virtual constructor) hides the details of the class implementing the TSTT from TSTT users. In version 0.5 of TSTT.sidl, the client hard codes the name of the implementing class into their code. The client is forced to choose from the small set of possible concrete classes defined in TSTT.sidl. This approach makes it impossible to support multiple implementations of the TSTT in a single process because each implementation has to implement the same class. The factory approach hides the details of mesh creation from the client. The client does not need to know the name of the implementing class, and the client can dynamically determine which interfaces are supported by the new mesh. A factory can support multiple TSTT implementation because each implementation defines its own concrete classes to implement. The factory approach does require the TSTT compliant mesh packages to implement a MeshFactory interface, and everyone needs to link against an implementation of the Registry. The Registry only has 7 methods that are fairly easy to implement, and everyone can share one implementation of the Registry.
Date: October 21, 2003
Creator: Epperly, T
Object Type: Report
System: The UNT Digital Library
Calibration of Regional Seismic Stations in the Middle East with Shots in Turkey (open access)

Calibration of Regional Seismic Stations in the Middle East with Shots in Turkey

The objective of this project is to calibrate regional travel-times and propagation characteristics of seismic waves in Turkey and surrounding areas in the Middle East in order to enhance detection and location capabilities in the region. Important data for the project will be obtained by large calibration shots in central and eastern Turkey. The first, a two-ton shot, was fired in boreholes near Keskin in central Anatolia on 23 November 2002. The explosives were placed in 14 holes, each 80 m deep, arranged in concentric circular arrays. Ninety temporary seismic stations were deployed within a 300 km radius around the shot. The permanent stations of the Turkish National Seismic Network provided a good azimuthal coverage as well as three radial traverses. Most stations within a radius of 200 km recorded the shot. Travel-time data have been analyzed to obtain a detailed crustal model under the shot and along the profiles. The model gives a 35 km thick crust, characterized by two layers with velocities of 5.0 and 6.4 km/s. The P{sub n} velocity was found to be 7.8 km/s. The crustal thickness decreases to the north where the profile crosses the North Anatolian fault. There is a slight increase in …
Date: July 21, 2003
Creator: Toksoz, M N; Kuleli, S; Gurbuz, C; Kalafat, D; Nekler, T; Zor, K et al.
Object Type: Article
System: The UNT Digital Library
Efficient Multi-keV X-ray Sources from Ti-doped Aerogel Targets (open access)

Efficient Multi-keV X-ray Sources from Ti-doped Aerogel Targets

We have measured the production of h{nu} {ge} 4.5 keV x-rays from low-density Ti-doped aerogel targets at the OMEGA laser facility (University of Rochester). The doped-foam density was {approx} 3 mg/cc. Forty beams of the OMEGA laser ({lambda}{sub L} = 0.351 {micro}m) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser interaction fully ionizes the target (n{sub e}/n{sub crit} {ge} 0.1), and allows the laser-bleaching wave to excite, supersonically, the high-Z emitter ions in the sample. Ti K-shell x-ray emission was spectrally resolved with a two-channel crystal spectrometer and also with a set of filtered aluminum x-ray diodes, both instruments provide absolute measurement of the multi-keV x-ray emission. Back-scattered laser energy is observed to be minimal. We find between 40 - 260 J of output with 4.67 {le} h{nu} {le} 5.0 keV.
Date: November 21, 2003
Creator: Satcher, J.; Fournier, K.; Suter, L.; Davis, J.; Back, C.; Grun, J. et al.
Object Type: Article
System: The UNT Digital Library
Ab initio calculations in a uniform magnetic field using periodic supercells (open access)

Ab initio calculations in a uniform magnetic field using periodic supercells

We present a formulation of ab initio electronic structure calculations in a finite magnetic field, which retains the simplicity and efficiency of techniques widely used in first principles molecular dynamics simulations, based on plane-wave basis sets and Fourier transforms. In addition we discuss results obtained with this method for the energy spectrum of interacting electrons in quantum wells, and for the electronic properties of dense fluid deuterium in a uniform magnetic field.
Date: October 21, 2003
Creator: Cai, W & Galli, G
Object Type: Article
System: The UNT Digital Library
Tests of the Contamination Analysis Unit, Phase 2 (open access)

Tests of the Contamination Analysis Unit, Phase 2

Results are reported for a project testing the capabilities of a mass spectrometer-based system for analyzing in-situ organic compounds on a variety of substrates. The system, which was built and operated at Lawrence Livermore National Laboratory (LLNL), is termed a Contamination Analysis Unit (CAU) and employs vacuum and thermal desorption of surface residues, followed by ionization and analysis with a Leybold Inficon Transpector mass spectrometer. The CAU was employed in this study to examine soils, cleaner residues, and substrates on Space Shuttle Reusable Solid Rocket Motor (RSRM) components. Project work was supported by ATK Thiokol Propulsion. Major project objectives include: (1) Determine residual propellant and liner components with the CAU after test coupons have been cleaned. (2) Determine if the CAU can detect solvent that has soaked into NBR insulation material, and if possible, determine the time following solvent application during which the cleaning agent is detectable. (3) Test CAU capabilities for analyzing non-flat surfaces on the inside and outside surfaces of the RSRM (12-foot diameter), and nozzle throat housing surfaces (5-foot diameter). (4) Determine if solvent extraction and gas chromatography (GC) approaches are able to enhance the surface analysis data available through use of the mass-spectrometer-based CAU. (5) Determine …
Date: January 21, 2003
Creator: Meltzer, M
Object Type: Report
System: The UNT Digital Library
Initial Experiences with Retrieving Similar Objects in Simulation Data (open access)

Initial Experiences with Retrieving Similar Objects in Simulation Data

Comparing the output of a physics simulation with an experiment, referred to as 'code validation,' is often done by visually comparing the two outputs. In order to determine which simulation is a closer match to the experiment, more quantitative measures are needed. In this paper, we describe our early experiences with this problem by considering the slightly simpler problem of finding objects in a image that are similar to a given query object. Focusing on a dataset from a fluid mixing problem, we report on our experiments with different features that are used to represent the objects of interest in the data. These early results indicate that the features must be chosen carefully to correctly represent the query object and the goal of the similarity search.
Date: February 21, 2003
Creator: Cheung, S-C S & Kamath, C
Object Type: Article
System: The UNT Digital Library
Hydrogeologic Unit Flow Characterization Using Transition Probability Geostatistics (open access)

Hydrogeologic Unit Flow Characterization Using Transition Probability Geostatistics

This paper describes a technique for applying the transition probability geostatistics method for stochastic simulation to a MODFLOW model. Transition probability geostatistics has several advantages over traditional indicator kriging methods including a simpler and more intuitive framework for interpreting geologic relationships and the ability to simulate juxtapositional tendencies such as fining upwards sequences. The indicator arrays generated by the transition probability simulation are converted to layer elevation and thickness arrays for use with the new Hydrogeologic Unit Flow (HUF) package in MODFLOW 2000. This makes it possible to preserve complex heterogeneity while using reasonably sized grids. An application of the technique involving probabilistic capture zone delineation for the Aberjona Aquifer in Woburn, Ma. is included.
Date: November 21, 2003
Creator: Jones, N L; Walker, J R & Carle, S F
Object Type: Article
System: The UNT Digital Library
Playing With Sandpiles. (open access)

Playing With Sandpiles.

The Bak-Tang-Wiesenfeld sandpile model provides a simple and elegant system with which to demonstrate self-organized criticality. This model has rather remarkable mathematical properties first elucidated by Dhar. I demonstrate some of these properties graphically with a simple computer simulation.
Date: January 21, 2003
Creator: Creutz, M.
Object Type: Article
System: The UNT Digital Library
Precision Manufacturing of Inertial Confinement Fusion Double Shell Laser Targets for OMEGA (open access)

Precision Manufacturing of Inertial Confinement Fusion Double Shell Laser Targets for OMEGA

Double shell targets have been built by Lawrence Livermore National Laboratory (LLNL) for inertial confinement fusion (ICF) experiments on the Omega laser at the University of Rochester and as a prelude to similar experiments on NIF. Of particular interest to ICF studies are high-precision double shell implosion targets for demonstrating thermonuclear ignition without the need for cryogenic preparation. Because the ignition tolerance to interface instabilities is rather low, the manufacturing requirements for smooth surface finishes and shell concentricity are particularly strict. This paper describes a deterministic approach to manufacturing and controlling error sources in each component. Included is the design philosophy of why certain manufacturing techniques were chosen to best reduce the errors within the target. The manufacturing plan developed for this effort created a deterministic process that, once proven, is repeatable. By taking this rigorous approach to controlling all error sources during the manufacture of each component and during assembly, we have achieved the overall 5 {micro}m dimensional requirement with sub-micron surface flaws. Strengths and weaknesses of the manufacturing process will be discussed.
Date: November 21, 2003
Creator: Amendt, P. A.; Bono, M. J.; Hibbard, R. L.; Castro, C. & Bennett, D. W.
Object Type: Article
System: The UNT Digital Library
Quarkonium at Finite Temperature. (open access)

Quarkonium at Finite Temperature.

The author discusses quarkonium spectral functions at finite temperature reconstructed using the Maximum Entropy Method. The author shows in particular that the J/{psi} survives in the deconfined phase up to 1.5T{sub c}.
Date: July 21, 2003
Creator: Petreczky, P.
Object Type: Article
System: The UNT Digital Library
Chemically Transformable Configurations of Mercaptohexadecanoic Acid Self-Assembled Monolayers Adsorbed on Au(111) (open access)

Chemically Transformable Configurations of Mercaptohexadecanoic Acid Self-Assembled Monolayers Adsorbed on Au(111)

Carboxyl terminated Self-Assembled Monolayers (SAMs) are commonly used in a variety of applications, with the assumption that the molecules form well ordered monolayers. In this work, NEXAFS verifies well ordered monolayers can be formed using acetic acid in the solvent. Disordered monolayers with unbound molecules present in the result using only ethanol. A stark reorientation occurs upon deprotonation of the endgroup by rinsing in a KOH solution. This reorientation of the endgroup is reversible with tilted over, hydrogen bound carboxyl groups while carboxylate-ion endgroups are upright. C1s photoemission shows that SAMs formed and rinsed with acetic acid in ethanol, the endgroups are protonated, while without, a large fraction of the molecules on the surface are carboxylate terminated.
Date: October 21, 2003
Creator: van Buuren, T; Bostedt, C; Nelson, A J; Terminello, L J; Vance, A L; Fadley, C S et al.
Object Type: Article
System: The UNT Digital Library
Hydrodynamic Instability of Ionization Fronts in HII Regions (open access)

Hydrodynamic Instability of Ionization Fronts in HII Regions

The authors investigate hydrodynamic instability of accelerating ionization fronts with two dimensional hydrodynamic simulations. When recombination in the ionized region is turned off, Rayleigh-Taylor instability is effective. Perturbation grows up with classical Rayleigh-Taylor growth rate. In the case with recombination, the local difference of absorption profile works to smooth the surface. The perturbation does not grow and the amplitude follows a damped oscillations with time.
Date: August 21, 2003
Creator: Mizuta, A.; Kane, J.; Ryutov, D.; Remington, B.; Takabe, H. & Pound, M.
Object Type: Article
System: The UNT Digital Library
NIF-0096141-OA Prop Simulations of NEL PBRS Measurements (open access)

NIF-0096141-OA Prop Simulations of NEL PBRS Measurements

Portable Back Reflection Sensor, PBRS, (NEL only) and Quad Back Reflection Sensor, QBRS, time delay reflectometer traces are among the most useful diagnostics of NIF laser status available. NEL PBRS measurements show several signals reaching the detector for each shot. The time delay between signals suggests that the largest of these is due to energy at the spatial filter pinhole planes leaking into adjacent pinholes and traveling back upstream to the PBRS. Prop simulations agree with current PBRS measurements to within 50%. This suggests that pinhole leakage is the dominant source of energy at the PBRS. However, the simulations predict that the energy leakage is proportional to beam output energy, while the PBRS measurements increase more slowly (''saturate''). Further refinement of the model or the measurement may be necessary to resolve this discrepancy.
Date: February 21, 2003
Creator: Widmayer, C. & Manes, K.
Object Type: Report
System: The UNT Digital Library
Instructions for Installation of the Whole-Building Diagnostician Software Release 2.10-162 (open access)

Instructions for Installation of the Whole-Building Diagnostician Software Release 2.10-162

The Whole Building Diagnostician (WBD) is modular diagnostic software that detects and diagnoses common problems associated with heating, ventilating, and air conditioning systems and equipment. This instruction document describes how to install the WBD and the Microsoft Data Access Object components, how to view the results in the demonstration database, and the new features of the Whole Building energy module (WBE).
Date: August 21, 2003
Creator: Carlon, Teresa A. & Bauman, Nathan N.
Object Type: Report
System: The UNT Digital Library
IR Extinction Coefficient Measurements of CH and CD GDP Shells (open access)

IR Extinction Coefficient Measurements of CH and CD GDP Shells

None
Date: March 21, 2003
Creator: Cook, R C & Nikroo, A
Object Type: Report
System: The UNT Digital Library
Towards An Ideal Slow Cookoff Model For PBXN-109 (open access)

Towards An Ideal Slow Cookoff Model For PBXN-109

We present an overview of computational techniques for simulating the thermal cookoff of high explosives using a multi-physics hydrodynamics code, ALE3D. Recent improvements to the code have aided our computational capability in modeling the response of energetic materials systems exposed to extreme thermal environments, such as fires. We consider an idealized model process for a confined explosive involving the transition from slow heating to rapid deflagration in which the time scale changes from days to hundreds of microseconds. The heating stage involves thermal expansion and decomposition according to an Arrhenius kinetics model while a pressure-dependent burn model is employed during the explosive phase. We describe and demonstrate the numerical strategies employed to make the transition from slow to fast dynamics. In addition, we investigate the sensitivity of wall expansion rates to numerical strategies and parameters. Results from a one-dimensional model show increased violence when the gap between the explosive and steel vessel is removed.
Date: November 21, 2003
Creator: Wardell, J. F.; Maienschein, J. L.; Yoh, J. J.; Nichols, A. L. & McClelland, M. A.
Object Type: Article
System: The UNT Digital Library
Freshwater Flow Charts - 1995 (open access)

Freshwater Flow Charts - 1995

This report covers the following: (1) Explanation of Charts Showing Freshwater Flow in 1995; (2) Estimated U.S. Freshwater Flow in 1995 (chart); (3) Estimated California Freshwater Flow in 1995 (chart); (4) Estimated New Mexico Freshwater Flow in 1995 (chart); and (5) Web locations and credits.
Date: November 21, 2003
Creator: Kaiper, G V
Object Type: Report
System: The UNT Digital Library
The effect of area size and predation on the time to extinction of prairie vole populations. simulation studies via SERDYCA: a Spatially-Explicit Individual-Based Model of Rodent Dynamics (open access)

The effect of area size and predation on the time to extinction of prairie vole populations. simulation studies via SERDYCA: a Spatially-Explicit Individual-Based Model of Rodent Dynamics

We present a spatially-explicit individual-based computational model of rodent dynamics, customized for the prairie vole species, M. Ochrogaster. The model is based on trophic relationships and represents important features such as territorial competition, mating behavior, density-dependent predation and dispersal out of the modeled spatial region. Vegetation growth and vole fecundity are dependent on climatic components. The results of simulations show that the model correctly predicts the overall temporal dynamics of the population density. Time-series analysis shows a very good match between the periods corresponding to the peak population density frequencies predicted by the model and the ones reported in the literature. The model is used to study the relation between persistence, landscape area and predation. We introduce the notions of average time to extinction (ATE) and persistence frequency to quantify persistence. While the ATE decreases with decrease of area, it is a bell-shaped function of the predation level: increasing for 'small' and decreasing for 'large' predation levels.
Date: November 21, 2003
Creator: Kostova, T & Carlsen, T
Object Type: Article
System: The UNT Digital Library
''6-Degrees of Freedom'' Single Crystal Plasticity Experiments (open access)

''6-Degrees of Freedom'' Single Crystal Plasticity Experiments

A deformation experiment has been developed specifically for the purpose of validation of dislocation dynamics simulations of plastic flow up to strains on the order of 1% [1]. The experiment has been designed so that a compressive uniaxial stress field is essentially super imposed on the test sample, and the crystal is free to deform with 3 orthogonal translation directions, and 3 rotation/tilt axes of freedom and has been given the name ''6-degrees of freedom'' (6DOF) experiment. The rotation, tilt and translation of the crystal are monitored by 5 laser displacement gages and 3 extensometers. Experiments are being performed on high purity Mo single crystals orientated for ''single slip''. All of the experiments are performed in pairs, with one test sample having highly polished surfaces for optical light and AFM slip-trace analyses, and the other having 4 strain gage rosettes mounted on the sides for measurement of the bi-axial surface strains during testing. All of the experimental data is used together to determine the slip activity of the orientated single crystal during deformation. Experimental results on high-purity Mo single crystals are presented. The results of these experiments show that slip behavior is in substantial deviation from the expected ''Schmid'' behavior. …
Date: May 21, 2003
Creator: Lassila, D. H.; Florando, J. N.; LeBlanc, M. M.; Arsenlis, T. & Rhee, M.
Object Type: Article
System: The UNT Digital Library
Mobility Laws in Dislocation Dynamics Simulations (open access)

Mobility Laws in Dislocation Dynamics Simulations

Prediction of the plastic deformation behavior of single crystals based on the collective dynamics of dislocations has been a challenge for computational materials science for a number of years. The difficulty lies in the inability of existing dislocation dynamics (DD) codes to handle a sufficiently large number of dislocation lines, to establish a statistically representative model of crystal plasticity. A new massively-parallel DD code is developed that is capable of modeling million-dislocation systems by employing thousands of processors. We discuss an important ingredient of this code--the mobility laws dictating the behavior of individual dislocations. They are materials input for DD simulations and are constructed based on the understanding of dislocation motion at the atomistic level.
Date: October 21, 2003
Creator: Cai, W & Bulatov, V V
Object Type: Article
System: The UNT Digital Library
Electrical Resistivity Modeling of a Permeable Reactive Barrier for Vista Engineering Technologies: Summary (open access)

Electrical Resistivity Modeling of a Permeable Reactive Barrier for Vista Engineering Technologies: Summary

We have performed a numerical modeling study that evaluated the capacity of electrical resistance tomography (ERT) to detect flaws in a passive reactive barrier (PRB). The model barrier is based on a real barrier described in the literature Slater and Binley (2003). It consists of highly conducting, granular iron emplaced within a trench. We assumed that the barrier was filled with a mixture of iron and sand, and that vertical electrode arrays were embedded within the barrier. We have considered (a) characterization and (b) monitoring scenarios. For (a), the objective is to use tomographs of absolute resistivity to detect construction flaws and inhomogeneities in iron distribution shortly after installation. For (b), the objective is to use resistivity change tomographs to detect iron oxidation and barrier plugging as a function of time. The study considered varying PRB hole sizes and locations. For any given model, a hole was located right next to and near the center of an electrode array (maximum sensitivity and resolution expected), at the center between two electrode arrays (moderate sensitivity and resolution), or near the bottom centered between the two arrays (minimum sensitivity and resolution). We also considered various hole sizes. The smallest hole considered had a …
Date: November 21, 2003
Creator: Ramirez, A L & Daily, W D
Object Type: Report
System: The UNT Digital Library
Radar Imaging of Spheres in 3D using MUSIC (open access)

Radar Imaging of Spheres in 3D using MUSIC

We have shown that multiple spheres can be imaged by linear and planar EM arrays using only one component of polarization. The imaging approach involves calculating the SVD of the scattering response matrix, selecting a subset of singular values that represents noise, and evaluating the MUSIC functional. The noise threshold applied to the spectrum of singular values for optimal performance is typically around 1%. The resulting signal subspace includes more than one singular value per sphere. The presence of reflections from the ground improves height localization, even for a linear array parallel to the ground. However, the interference between direct and reflected energy modulates the field, creating periodic nulls that can obscure targets in typical images. These nulls are largely eliminated by normalizing the MUSIC functional with the broadside beam pattern of the array. The resulting images show excellent localization for 1 and 2 spheres. The performance for the 3 sphere configurations are complicated by shadowing effects and the greater range of the 3rd sphere in case 2. Two of the three spheres are easily located by MUSIC but the third is difficult to distinguish from other local maxima of the complex imaging functional. Improvement is seen when the linear …
Date: January 21, 2003
Creator: Chambers, D H & Berryman, J G
Object Type: Report
System: The UNT Digital Library