Quantum efficiency characterization of LBNL CCD's Part 1: theQuantum Efficiency Machine (open access)

Quantum efficiency characterization of LBNL CCD's Part 1: theQuantum Efficiency Machine

Instrumentation was developed in 2004 and 2005 to measurethe quantum efficiency of the Lawrence Berkeley National Lab(LBNL)total-depletion CCD's, intended for astronomy and spaceapplications. This paper describes the basic instrument. Although it isconventional even to the parts list, there are important innovations. Axenon arc light source was chosen for its high blue/UV and low red/IRoutput as compared with a tungsten light. Intensity stabilization hasbeen difficult, but sinceonly flux ratios matter this is not critical.Between the light source andan Oriel MS257 monochromator are a shutterand two filter wheels. High-bandpass and low-bandpass filter pairsisolate the 150-nm wide bands appropriate to the wavelength, thusminimizing scattered light and providing order blocking. Light from theauxiliary port enters a 20-inch optical sphere, and the 4-inch outputport is at right angles to the input port. An 80 cm drift space producesnear-uniform illumination on the CCD. Next to the cold CCD inside thehorizontal dewar is a calibrated reference photodiode which is regulatedto the PD calibration temperature, 25$^\circ$ C. The ratio ofthe CCD andin-dewar reference PD signals provides the QE measurement. Additionalcross-calibration to a PD on the integrating spherepermitslower-intensity exposures.
Date: December 25, 2005
Creator: Groom, Donald E.; Bebek, Christopher J.; Fabricius, Maximilian; Karcher, Armin; Kolbe, William F.; Roe, Natalie A. et al.
Object Type: Article
System: The UNT Digital Library
Final Technical Report (open access)

Final Technical Report

This document comprises the final technical report for atomic collisions research supported by DOE grant No. DE-FG02-87ER13778 from September 1, 2001 through August 31, 2004. The research involved the experimental investigation of excitation and charge-changing processes occurring in ion-atom and ion-molecule collisions. Major emphases of the study were: (1) interference effects resulting from coherent electron emission in H2, (2) production of doubly vacant K-shell (hollow ion) states due to electron correlation, and (3) formation of long-lived metastable states in electron transfer processes. During the period of the grant, this research resulted in 23 publications, 12 invited presentations, and 39 contributed presentations at national and international meetings and other institutions. Brief summaries of the completed research are presented below.
Date: November 25, 2005
Creator: Tanis, John
Object Type: Report
System: The UNT Digital Library
Portable Hand-Held Electrochemical Sensor for the Transuranics (open access)

Portable Hand-Held Electrochemical Sensor for the Transuranics

During the four-year period of the grant all of the goals of the originally proposed work were achieved, and some additional accomplishments are here reported. Two types of sensors were designed and built in the lab, capable of detecting uranium, plutonium and thorium at the 10 part-per-trillion level. The basis of both sensor types is a specially designed polymer having selective binding sites for actinyl ions of the form MO{sub 2}{sup 2+}(aq), where M is any actinide in the +6 oxidation state. This binding site also traps ions of the form MO{sub 2}{sup +}(aq), where M is any actinide in the +4 oxidation state. In this way, the polymer is responsive to the two most common water-soluble ions of the actinide series. The chelating ring responsible for binding the actinyl ions was identified from the literature, calix[n]arene where n = 6. Several versions of this sensing polymer were coated on conductive substrates and demonstrated for actinide sensing. An optimized sensor was developed and is fully described in this report. It has a polymer bilayer, fabricated under the particular conditions given below. Two different operating modes were demonstrated having different capabilities. One is the chemFET mode (a FET is a field …
Date: November 25, 2005
Creator: Dale D. Russell, William B. Knowlton, Ph.D. & Russel Hertzog, Ph.D
Object Type: Report
System: The UNT Digital Library
April 25, 2003, FY2003 Progress Summary and FY2002 Program Plan, Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers,and Complementary Technologies, for Applications in Energy and Defense (open access)

April 25, 2003, FY2003 Progress Summary and FY2002 Program Plan, Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers,and Complementary Technologies, for Applications in Energy and Defense

The High Average Power Laser Program (HAPL) is a multi-institutional, synergistic effort to develop inertial fusion energy (IFE). This program is building a physics and technology base to complement the laser-fusion science being pursued by DOE Defense programs in support of Stockpile Stewardship. The primary institutions responsible for overseeing and coordinating the research activities are the Naval Research Laboratory (NRL) and Lawrence Livermore National Laboratory (LLNL). The current LLNL proposal is a companion document to the one submitted by NRL, for which the driver development element is focused on the krypton fluoride excimer laser option. The NRL and LLNL proposals also jointly pursue complementary activities with the associated rep-rated laser technologies relating to target fabrication, target injection, final optics, fusion chamber, target physics, materials and power plant economics. This proposal requests continued funding in FY03 to support LLNL in its program to build a 1 kW, 100 J, diode-pumped, crystalline laser, as well as research into high gain fusion target design, fusion chamber issues, and survivability of the final optic element. These technologies are crucial to the feasibility of inertial fusion energy power plants and also have relevance in rep-rated stewardship experiments. The HAPL Program pursues technologies needed for laser-driven …
Date: October 25, 2005
Creator: Meier, W & Bibeau, C
Object Type: Report
System: The UNT Digital Library
Atomic-Nuclear Coupling Experiments (open access)

Atomic-Nuclear Coupling Experiments

Atomic-nuclear coupling experiments are described, with an emphasis on recent experiments aimed at demonstrating the NEET mechanism in atomic nuclei. Upper limits for x-ray induced decay of the Hf-178 31-y isomer reported by Ahmad and his colleagues are presented, and these upper limits are contrasted with the positive reports of Collins and coworkers.
Date: October 25, 2005
Creator: Becker, J. A.
Object Type: Article
System: The UNT Digital Library
Best Practices Submittal for Digital Radiography (open access)

Best Practices Submittal for Digital Radiography

This report is about the non-destructive examination technique using a radioactive source generation either x or gamma rays to map the subject's features and density changes to a reusable phosphorous coated plate.
Date: October 25, 2005
Creator: Mcdanel, Jeffrey
Object Type: Report
System: The UNT Digital Library
Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197 (open access)

Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197

We report the first detection of radio emission from any anomalous X-ray pulsar (AXP). Data from the Very Large Array (VLA) MAGPIS survey with angular resolution 6'' reveals a point-source of flux density 4.5 {+-} 0.5 mJy at 1.4 GHz at the precise location of the 5.54 s pulsar XTE J1810-197. This is greater than upper limits from all other AXPs and from quiescent states of soft gamma-ray repeaters (SGRs). The detection was made in 2004 January, 1 year after the discovery of XTE J1810-197 during its only known outburst. Additional VLA observations both before and after the outburst yield only upper limits that are comparable to or larger than the single detection, neither supporting nor ruling out a decaying radio afterglow related to the X-ray turn-on. Another hypothesis is that, unlike the other AXPs and SGRs, XTE J1810-197 may power a radio synchrotron nebula by the interaction of its particle wind with a moderately dense environment that was not evacuated by previous activity from this least luminous, in X-rays, of the known magnetars.
Date: October 25, 2005
Creator: Halpern, J P; Gotthelf, E V; Becker, R H; Helfand, D J & White, R L
Object Type: Article
System: The UNT Digital Library
Echoes from Ancient Supernovae in the Large Magellanic Cloud (open access)

Echoes from Ancient Supernovae in the Large Magellanic Cloud

None
Date: October 25, 2005
Creator: Rest, A.; Suntzeff, N. B.; Olsen, K.; Prieto, J. L.; Smith, R. C.; Welch, D. L. et al.
Object Type: Article
System: The UNT Digital Library
Evolution of Intermediate and Low Mass Binary Systems (open access)

Evolution of Intermediate and Low Mass Binary Systems

There are a number of binaries, fairly wide and with one or even two evolved giant components, that do not agree very well with conventional stellar evolution: the secondaries are substantially larger (oversized) than they should be because their masses are quite low compared with the primaries. I discuss the possibility that these binaries are former triples, in which a merger has occurred fairly recently in a short-period binary sub-component. Some mergers are expected, and may follow a phase of contact evolution. I suggest that in contact there is substantial transfer of luminosity between the components due to differential rotation, of the character observed by helioseismology in the Sun's surface convection zone.
Date: October 25, 2005
Creator: Eggleton, P P
Object Type: Article
System: The UNT Digital Library
Fabrication and Characterization of Borosilicate Glasses Containing Alpha-Radionuclides and Silver From Conversion and Mixed-Oxide Facilities Proposed for Russia (open access)

Fabrication and Characterization of Borosilicate Glasses Containing Alpha-Radionuclides and Silver From Conversion and Mixed-Oxide Facilities Proposed for Russia

Liquid and solid radioactive wastes are formed during conversion of plutonium metal to oxide and during fabrication of weapons-grade plutonium into mixed-oxide (MOX) fuel. In Russia, these wastes are to be processed for disposition by immobilization in either borosilicate glass or cement matrices depending upon the waste stream-specific radionuclide contents. Vitrification is planned for the liquid high-level waste raffinate stream containing the bulk of the Am-241 produced from Pu-241 decay. Previous work on the Russian MOX Fuel Fabrication Facility (R-MFFF) by the Public Joint Stock Corporation (TVEL) [1] showed that this waste stream may contain significant amounts of silver derived from the electrochemical dissolution of PuO2 using a Ag(II) catalyst. The work reported here further investigated silver solubility limits, which, if exceeded in a production glass melter, allow discrete silver grains to form in the glass and also deposit over time on the bottom of a joule-heated ceramic melter. In melters with immersed electrodes, such as the Russian EP-100 for phosphate glasses or the US Duratek DP-100 type melters for borosilicate glasses that are being considered for use at the Siberian Chemical Combine (SCC) Tomsk site, the undissolved silver could cause a short circuit and an unacceptable production melter failure. …
Date: October 25, 2005
Creator: Aloy, Albert S.; Trofimenko, Alexander V.; Uspensky, Alexander I. & Jardine, Leslie J.
Object Type: Article
System: The UNT Digital Library

Hadronic Cross-Sections for Neutrino Production in MIPP

Hadronic Cross Sections for Neutrino Production in MIPP
Date: October 25, 2005
Creator: Paley, Jonathan
Object Type: Presentation
System: The UNT Digital Library
Improved Method for Laser Damage Testing Coated Optics (open access)

Improved Method for Laser Damage Testing Coated Optics

The damage test procedure for qualifying a coating run of anti-reflection coated optics consists of scanning a pulsed 1064 nm laser over a 1 cm x 1 cm area on a test sample to illuminate approximately 2400 sites. Scans are repeated at 3 J/cm{sup 2} increments until the fluence specification for the optic is reached. In the past, initiation of 1 or more damage sites was classified as a failed coating run, requiring the production optics in the corresponding coating lot be reworked and recoated. Recent laser damage growth tests of 300 repetitive pulses performed on numerous damage sites revealed that all were stable up to 20 J/cm{sup 2}. Therefore the acceptance criteria has been modified to allow a moderate number of damage sites, as long as they are smaller than the allowed dig size and are stable (do not grow). Consequently many coating runs that previously would have been rejected are now accepted, resulting in higher yield, lower cost, and improved delivery schedule. The new test also provides assurance that initiated damage sites are stable during long term operation.
Date: October 25, 2005
Creator: Borden, M. R.; Folta, J. A.; Stolz, C. J.; Taylor, J. R.; Wolfe, J. E.; Griffin, A. J. et al.
Object Type: Article
System: The UNT Digital Library
Modeling Interactions of Surface-Subsurface Flow Using a Free-Surface Overland Flow Boundary Condition in a Parallel Flow Simulator (open access)

Modeling Interactions of Surface-Subsurface Flow Using a Free-Surface Overland Flow Boundary Condition in a Parallel Flow Simulator

Models incorporating interactions between surface and subsurface flow are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. In these models the subsurface and surface domains are linked via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in the field, a more general coupled modeling approach would be preferable. We present a more general approach that incorporates a two-dimensional overland flow simulator into the parallel three-dimensional variably saturated subsurface flow code ParFlow developed at LLNL. This overland flow simulator takes the form of an upper, free-surface boundary condition and is, thus, fully integrated without relying on the conductance concept. Another advantage of this approach is the efficient parallelism of ParFlow, which is exploited by the overland flow simulator. Several verification and simulation examples are presented that focus on the two main processes of runoff production: excess infiltration and saturation. The usefulness of our approach is demonstrated in an application of the model to an urban watershed. The …
Date: October 25, 2005
Creator: Kollet, S J & Maxwell, R M
Object Type: Article
System: The UNT Digital Library
Prediction of Frictional Pressure Drop During Water Permeation Through Packed Beds of Granular Particulates (open access)

Prediction of Frictional Pressure Drop During Water Permeation Through Packed Beds of Granular Particulates

A methodology has been developed based on the Kozeny-Carman equation to predict frictional pressure drops during water permeation of packed columns containing essentially noncompressible, but highly irregular particles. The resulting model accurately predicts pressure drop as a function of liquid flow rate and resin particle size for this system. A total of five particle sieve cuts across the range -20 to +70 mesh were utilized for testing using deionized water as the mobile phase. The Rosin-Rammler equation was used to fit the raw particle size data (wet sieve analysis) for the as-received resin sample and generate a continuous cumulative distribution function based on weight percent passing through the sieve. Probability distribution functions were calculated from the cumulative distribution for each particle sieve cut tested. Nine particle diameter definitions (i.e., number mean, volume mean, etc.) were then selected from the distribution function for each sample to represent the average spherically-equivalent particle diameter as input to the Kozeny-Carman equation. Nonlinear least squares optimization of the normalized pressure drop residuals were performed by parameter estimation of particle shape factor and bed porosity for all samples simultaneously using a given average particle diameter definition. Good fits to the full experimental data set were obtained …
Date: October 25, 2005
Creator: King, William D.; Aleman, Sebastian E.; Hamm, L. Larry & Pettis, Myra A.
Object Type: Article
System: The UNT Digital Library
Preliminary Assessment of Existing Experimental Data for Validation of Reactor Physics Codes and Data for NGNP Design and Analysis. (open access)

Preliminary Assessment of Existing Experimental Data for Validation of Reactor Physics Codes and Data for NGNP Design and Analysis.

The Next Generation Nuclear Plant (NGNP), a demonstration reactor and hydrogen production facility proposed for construction at the INEEL, is expected to be a high-temperature gas-cooled reactor (HTGR). Computer codes used in design and safety analysis for the NGNP must be benchmarked against experimental data. The INEEL and ANL have examined information about several past and present experimental and prototypical facilities based on HTGR concepts to assess the potential of these facilities for use in this benchmarking effort. Both reactors and critical facilities applicable to pebble-bed and prismatic block-type cores have been considered. Four facilities--HTR-PROTEUS, HTR-10, ASTRA, and AVR--appear to have the greatest potential for use in benchmarking codes for pebble-bed reactors. Similarly, for the prismatic block-type reactor design, two experiments have been ranked as having the highest priority--HTTR and VHTRC.
Date: October 25, 2005
Creator: Terry, W. K.; Jewell, J. K.; Briggs, J. B.; Taiwo, T. A.; Park, W.S. & Khalil, H. S.
Object Type: Report
System: The UNT Digital Library
Proceedings of Riken Bnl Research Center Workshop Entitled "Can We Discover the Qcd Critical Point at Rhic?" (Volume 80). (open access)

Proceedings of Riken Bnl Research Center Workshop Entitled "Can We Discover the Qcd Critical Point at Rhic?" (Volume 80).

None
Date: October 25, 2005
Creator: Organizers: Ludlum, T.; Ritter, H.; Stephans, G.; Gazdzicki, M.; Friman, B.; Videbaek, F. et al.
Object Type: Report
System: The UNT Digital Library
PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED "ODDERON SEARCHES AT RHIC" (VOLUME 76) (open access)

PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED "ODDERON SEARCHES AT RHIC" (VOLUME 76)

The Odderon, a charge-conjugation-odd partner of the Pomeron, has been a puzzle ever since its introduction in 1973. The Pomeron describes a colorless exchange with vacuum quantum numbers in the t-channel of hadronic scattering at high energies. The concept was originally formulated for the non-perturbative regime of Quantum Chromodynamics (QCD). In perturbation theory, the simplest picture of the Poineron is that of a two-gluon exchange process, whereas an Odderon can be thought of as an exchange of three gluons. Both the Pomeron and the Odderon are expected in QCD. However, while there exists plenty of experimental data that could be successfully described by Pomeron exchanges (for example in electron-proton and hadron-hadron scattering at high energies), no experimental sign of the Odderon has been observed. One of the very few hints so far is the difference in the diffractive minima of elastic proton-proton and proton-antiproton scattering measured at the ISR. The Odderon has recently received renewed attention by QCD researchers, mainly for the following two reasons. First of all, RHIC has entered the scene, offering exciting unique new opportunities for Odderon searches. RHIC provides collisions of nuclei at center-of-mass energies far exceeding those at all previous experiments. RHIC also provides collisions …
Date: October 25, 2005
Creator: Guryn, Lodek; Kovchegov, Yuri; Vogelsang, Werner & Trueman, Larry
Object Type: Report
System: The UNT Digital Library
Reactivity of Resorcinol Formaldehyde Resin with Nitric Acid (open access)

Reactivity of Resorcinol Formaldehyde Resin with Nitric Acid

Solid-state infrared spectroscopy, differential scanning calorimetry, and elemental analysis have been used to evaluate the reactivity of resorcinol formaldehyde resin with nitric acid and characterize the solid product. Two distinct reactions were identified within the temperature range 25-55 C. The first reaction is primarily associated with resin nitration, while the second involves bulk oxidation and degradation of the polymer network leading to dissolution and off-gassing. The threshold conditions promoting reaction have been identified. Reaction was confirmed with nitric acid concentrations as low as 3 M at 25 C applied temperature and 0.625 M at 66 C. Although a nitrated resin product can be isolated under appropriate experimental conditions, calorimetry testing indicates no significant hazard associated with handling the dry material.
Date: October 25, 2005
Creator: King, William D.; Fondeur, Fernando F.; Wilmarth, William R. & Pettis, Myra E.
Object Type: Article
System: The UNT Digital Library
Sensitivity Quantification of Remote Detection NMR and MRI (open access)

Sensitivity Quantification of Remote Detection NMR and MRI

A sensitivity analysis of the remote detection NMR techniqueis presented. With remote detection, information about a sample isencoded onto a mobile sensor fluid, which facilitates a spatialseparation of encoding and detection of spin magnetization. This approachcan be interpreted as a two-dimensional NMR experiment, therefore thesame general formalism can be used for a sensitivity analysis. Eventhough remote detection is a point-by-point experiment, the sensitivitydoes not scale unfavorably with the number of detected points compared totransient detection. It is proportional to the relative sensitivitybetween the remote detector and the circuit that is used for encoding.The influence of the different signal decay times is analyzed, and thedistinction between spectroscopy and imaging experiments ismade.
Date: October 25, 2005
Creator: Granwehr, Josef & Seeley, Juliette A.
Object Type: Article
System: The UNT Digital Library
TECHNICAL PEER REVIEW REPORT - YUCCA MOUNTAIN: WASTE PACKAGE CLOSURE CONTROL SYSTEM (open access)

TECHNICAL PEER REVIEW REPORT - YUCCA MOUNTAIN: WASTE PACKAGE CLOSURE CONTROL SYSTEM

The objective of the Waste Package Closure System (WPCS) project is to assist in the disposal of spent nuclear fuel (SNF) and associated high-level wastes (HLW) at the Yucca Mountain site in Nevada. Materials will be transferred from the casks into a waste package (WP), sealed, and placed into the underground facility. The SNF/HLW transfer and closure operations will be performed in an aboveground facility. The objective of the Control System is to bring together major components of the entire WPCS ensuring that unit operations correctly receive, and respond to, commands and requests for data. Integrated control systems will be provided to ensure that all operations can be performed remotely. Maintenance on equipment may be done using hands-on or remote methods, depending on complexity, exposure, and ease of access. Operating parameters and nondestructive examination results will be collected and stored as permanent electronic records. Minor weld repairs must be performed within the closure cell if the welds do not meet the inspection acceptance requirements. Any WP with extensive weld defects that require lids to be removed will be moved to the remediation facility for repair.
Date: October 25, 2005
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Technical Report -- Essentials of which will be published as a journal paper (open access)

Technical Report -- Essentials of which will be published as a journal paper

Vertical Transport and Mixing in Complex Terrain Airsheds: Implementation of a Stable PBL Turbulence Parameterization for the Mesoscale Model MM5 The difficulties associated with parameterization of turbulence in the stable nocturnal atmospheric boundary layer have been a great challenge for the night-time predictions of mesoscale meteorological models such as MM5. As such, there is a general consensus on the need for better stable boundary-layer parameterizations. To this end, two new turbulence parameterizations based on the measurements of the Vertical Transport and Mixing (VTMX) field campaign were implemented and evaluated in MM5. A unique aspect of this parameterization is the use of a stability dependent turbulent Prandtl number that allows momentum to be transported by the internal waves, while heat diffusion is impeded by the stratification. This improvement alleviates the problem of over-prediction of heat diffusion under stable conditions, which is a characteristic of conventional PBL schemes, such as MRF and Blackadar schemes employed in MM5. The predictions made with the new PBL scheme for the complex terrain airshed of Salt Lake City were compared with those made with a default scheme of MM5 and with observations made during the VTMX campaign. The new schemes showed an improvement in predictions, particularly …
Date: October 25, 2005
Creator: Fernando, Harindra J. S.; Anderson, James & Boyer, Don
Object Type: Report
System: The UNT Digital Library
Utility Integrated Resource Planning: An Emerging Driver of NewRenewable Generation in the Western United States (open access)

Utility Integrated Resource Planning: An Emerging Driver of NewRenewable Generation in the Western United States

In the United States, markets for renewable generation--especially wind power--have grown substantially in recent years. This growth is typically attributed to technology improvements and resulting cost reductions, the availability of federal tax incentives, and aggressive state policy efforts. But another less widely recognized driver of new renewable generation is poised to play a major role in the coming years: utility integrated resource planning (IRP). Common in the late-1980s to mid-1990s, but relegated to lesser importance as many states took steps to restructure their electricity markets in the late-1990s, IRP has re-emerged in recent years as an important tool for utilities and regulators, particularly in regions such as the western United States, where retail competition has failed to take root. As practiced in the United States, IRP is a formal process by which utilities analyze the costs, benefits, and risks of all resources available to them--both supply- and demand-side--with the ultimate goal of identifying a portfolio of resources that meets their future needs at lowest cost and/or risk. Though the content of any specific utility IRP is unique, all are built on a common basic framework: (1) development of peak demand and load forecasts; (2) assessment of how these forecasts compare …
Date: September 25, 2005
Creator: Bolinger, Mark & Wiser, Ryan
Object Type: Article
System: The UNT Digital Library
Analysis of Heavy-Ion Beam Images and Comparison to RetardingPotential Analyzer Measurements (open access)

Analysis of Heavy-Ion Beam Images and Comparison to RetardingPotential Analyzer Measurements

It has been predicted that world energy demand will soon put enormous pressure on the currently available energy sources. Fusion energy is a potential solution to this problem if it can be controlled and converted into electricity in an economically feasible manner. One type of potential fusion energy plant uses heavy-ion beam drivers for inertial fusion energy. As part of the High Current Experiment (HCX), we seek to understand the injection, transport and focusing of high-current ion beams, by investigating the interactions of background gas and electrons (which can deteriorate the beam quality) with the primary K{sup +} beam. We present here a method of analyzing the electrostatic potential distribution due to the beam space charge within the grounded conducting vacuum pipe. This method enables tracking of ions arising from the ionization of background gas atoms by the incident K{sup +} beam. The beam intensity distribution is obtained from images gathered using a scintillator placed in the beam path. These data are used to calculate the expelled ion energy distribution, which is then compared to data collected from a Retarding Potential Analyzer (RPA). The comparison of the image analysis with RPA measurements is in fair agreement, given model and experimental …
Date: August 25, 2005
Creator: Rosenberg, Beth E.
Object Type: Report
System: The UNT Digital Library
ASC Supercomputers Predict Effects of Aging on Materials (open access)

ASC Supercomputers Predict Effects of Aging on Materials

In an extensive molecular dynamics (MD) study of shock compression of aluminum containing such microscopic defects as found in aged plutonium, LLNL scientists have demonstrated that ASC supercomputers live up to their promise as powerful tools to predict aging phenomena in the nuclear stockpile. Although these MD investigations are carried out on material samples containing only about 10 to 40 million atoms, and being not much bigger than a virus particle, they have shown that reliable materials properties and relationships between them can be extracted for density, temperature, pressure, and dynamic strength. This was proven by comparing their predictions with experimental data of the Hugoniot, with dynamic strength inferred from gas-gun experiments, and with the temperatures behind the shock front as calculated with hydro-codes. The effects of microscopic helium bubbles and of radiation-induced dislocation loops and voids on the equation of state were also determined and found to be small and in agreement with earlier theoretical predictions and recent diamond-anvil-cell experiments. However, these microscopic defects play an essential role in correctly predicting the dynamic strength for these nano-crystalline samples. These simulations also prove that the physics involved in shock compression experiments remains the same for macroscopic specimens used in gas-gun …
Date: August 25, 2005
Creator: Kubota, A; Reisman, D B & Wolfer, W G
Object Type: Report
System: The UNT Digital Library