Publications

Abstract not provided.

Abstract not provided.

The use of Ion Mobility Spectrometry (IMS) in the Detection of Contraband Sandia researchers use ion mobility spectrometers for trace chemical detection and analysis in a variety of projects and applications. Products developed in recent years based on IMS-technology include explosives detection personnel portals, the Material Area Access (MAA) checkpoint of the future, an explosives detection vehicle portal, hand-held detection systems such as the Hound and Hound II (all 6400), micro-IMS sensors (1700), ordnance detection (2500), and Fourier Transform IMS technology (8700). The emphasis to date has been on explosives detection, but the detection of chemical agents has also been pursued (8100 and 6400). Combining Ion Mobility Spectrometry (IMS) with Mass Spectrometry (MS) is described. The IMS-MS combination overcomes several limitations present in simple IMS systems. Ion mobility alone is insufficient to identify an unknown chemical agent. Collision cross section, upon which mobility is based, is not sufficiently unique or predictable a priori to be able to make a confident peak assignment unless the compounds present are already identified. Molecular mass, on the other hand, is much more readily interpreted and related to compounds. For a given compound, the molecular mass can be determined using a pocket calculator (or in one's head) while a reasonable value of the cross-section might require hours of computation time. Thus a mass spectrum provides chemical specificity and identity not accessible in the mobility spectrum alone. In addition, several advanced mass spectrometric methods, such as tandem MS, have been extensively developed for the purpose of molecular identification. With an appropriate mass spectrometer connected to an ion mobility spectrometer, these advanced identification methods become available, providing greater characterization capability.

Sedimentary basins can increase the magnitude and extend the duration of seismic shaking. This potential for seismic amplification is investigated for Pahrump Valley, Nevada-California. The Pahrump Valley is located approximately 50 km northwest of Las Vegas and 75 km south of the Nevada Test Site. Gravity data suggest that the city of Pahrump sits atop a narrow, approximately 5 km deep sub-basin within the valley. The seismic amplification, or ''site effect'', was investigated using a combination of in situ velocity modeling and comparison of the waveforms and spectra of weak ground motion recorded in the city of Pahrump, Nevada, and those recorded in the nearby mountains. Resulting spectral ratios indicate seismic amplification factors of 3-6 over the deepest portion of Pahrump Valley. This amplification predominantly occurs at 2-2.5 Hz. Amplification over the deep sub-basin is lower than amplification at the sub-basin edge, location of the John Blume and Associates PAHA seismic station, which recorded many underground nuclear tests at the Nevada Test Site. A comprehensive analysis of basin amplification for the city of Pahrump should include 3-D basin modeling, due to the extreme basement topography of the Pahrump Valley.

This report describes results of tests using a laser system designed by Coherent Technologies, Inc., in conjunction with Sandia developed nonlinear optics technology. Test results are described for three different optical parametric oscillators built at Sandia. The report concludes with recommendations for future work.

We report low-dimensional transport and tunneling in an independently contacted vertically coupled quantum wire system, with a 7.5 nm barrier between the wires. The derivative of the linear conductance shows evidence for both single wire occupation and coupling between the wires. This provides a map of the subband occupation that illustrates the control that we have over the vertically coupled double quantum wires. Preliminary tunneling results indicate a sharp 1D-1D peak in conjunction with a broad 2D-2D background signal. This 1D-1D peak is sensitively dependent on the top and bottom split gate voltage. © 2005 American Institute of Physics.

The temperature dependence of the resistivity and magnetoresistance of dilute 2D electrons are reported. The temperature dependence of the resistivity can be qualitatively described through phonon and ionized impurity scattering. While the temperature dependence indicates no ln(T) increase in the resistance, a sharp negative magnetoresistance feature is observed at small magnetic fields. This is shown to arise from weak localization. At very low density, we believe weak localization is still present, but cannot separate it from other effects that cause magnetoresistance in the semi-classical regime. © 2005 American Institute of Physics.

Collective impact ionization has been used to explain lock-on, an optically-triggered electrical breakdown occurring in some photoconductive semiconductor switches (PCSS's). Lock-on is observed in GaAs and InP but not in Si or GaP. Here, a rate equation implementation of collective impact ionization is discussed, and it leads to new insights both about intrinsic electrical breakdown in insulating materials in general and about lock-on specifically. In this approach, lock-on and electrical breakdown are steady state processes controlled by competition between carrier generation and recombination. This leads to theoretical definitions for both the lock-on field and the breakdown field. Our results show that lock-on is a carrier-density dependent form of electrical breakdown which exists in principle in all semiconductors. Results for GaAs, InP, Si, and GaP are discussed. © 2005 American Institute of Physics.

We report a study on the uniformity of long quantum wires in the crossover from ballistic to diffuse transport with lengths ranging from 1 μm to 20 μm. For the 1 μm wire we measure 15 plateaus quantized at integer values of 2e2/h. With increasing length we observe plateaus at conductance values suppressed below the quantized values. With nonlinear fitting to the magnetoresistances we obtain an effective width for the quantum wires. As we find no systematic variation of the effective width as a function of sublevel index for the various length wires, we conclude that we have uniform long single quantum wires up to 20 μm. © 2005 American Institute of Physics.

During the past several years Sandia National Laboratories has carried out proof-of-concept experiments to demonstrate tunable, efficient, high-energy ultraviolet nanosecond light sources for satellite-based ozone DIAL. We designed our UV sources to generate pulse energies ≳ 200 mJ at 10 Hz in the range of 308-320 nm with optical-to-optical efficiency approaching 25%. We use sum-frequency generation to mix the 532 nm second harmonic of Nd:YAG with near-IR light derived from a self-injection-seeded image-rotating nonplanar-ring optical parametric oscillator. Laboratory configurations using extra- and intra-cavity sum-frequency generation were designed and tested, yielding 1064 nm to 320 nm conversion efficiencies of 21% and 23% respectively, with pulse energies of 190 mJ and 70 mJ. These energies and efficiencies require pump depletion in the parametric oscillator of at least 80% and SFG efficiency approaching 60%. While the results reported here fall slightly short of our original goals, we believe UV pulse energies exceeding 250 mJ are possible with additional refinements to our technology. Although the sources tested to date are laboratory prototypes with extensive diagnostics, the core components are compact and mechanically robust and can easily be packaged for satellite deployment.

Unstabilized polypropylene (PP) films having selective 13C isotopic labeling were subjected to thermal aging at 50, 80, and 109 °C and to γ-irradiation at 24 and 80°C. The oxidized films were examined using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Dramatic differences were found in the type and distribution of oxidation products originating from the three carbon atom sites within the PP macromolecule (tertiary carbon, secondary carbon, and methyl side group). Most of the oxidation products that formed on the polymer chain originated through chemical reactions at the PP tertiary carbons. Under all of the aging conditions examined, tertiary peroxides (from the PP tertiary site) were the most abundant functional group produced. Also originating from the PP tertiary carbon were significant amounts of tertiary alcohols, together with several more minor products that included "chain-end" methyl ketones. No significant amount of peroxides or alcohols associated with the PP secondary carbon sites was detected. A substantial yield of carboxylate groups was identified (acids, esters, etc.). The majority of these originated from the PP secondary carbon site, from which other minor products also formed, including in-chain ketones. We found no measurable yield of oxidation products originating from reaction at the PP methyl group. Remarkably similar distributions of the major oxidation products were obtained for thermal aging at different temperatures, whereas the product distributions obtained for irradiation at the different temperatures exhibited significant differences. Time-dependent concentration plots have been obtained, which show the amounts of the various oxidation products originating at the different PP sites, as a function of the extent of material oxidation. © 2005 American Chemical Society.

We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2 THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8 THz as local oscillator. We measure a double sideband receiver noise temperature of 1400 K at 2.8 THz and 4.2 K, and find that the free-running QCL has sufficient power stability for a practical receiver, demonstrating an unprecedented combination of sensitivity and stability. © 2005 American Institute of Physics.

In this work, the BAC-MP4 method is extended for the first time to compounds in the fourth row of the periodic table, resulting in a self-consistent set of thermochemical data for 56 tin-containing molecules in the Sn-H-C-Cl system. The BAC-MP4 method combines ab initio electronic structure calculations with empirical corrections to obtain accurate heats of formation. To obtain electronic energies for tin-containing species, the standard 6-31G(d,p) basis set used in BAC-MP4 calculations is augmented with a relativistic effective core potential to describe the electronic structure of the tin atom. Both stable compounds and radical species are included in this study. Trends within homologous series and calculated bond dissociation energies are consistent with previous BAC-MP4 predictions for group 14 compounds and the limited data available from the literature, indicating that the method is performing well for these compounds. © 2005 American Chemical Society.

We have studied the vinyl + NO reaction using time-resolved Fourier transform emission spectroscopy, complemented by electronic structure and microcanonical RRKM rate coefficient calculations. To unambiguously determine the reaction products, three precursors are used to produce the vinyl radical by laser photolysis: vinyl bromide, methyl vinyl ketone, and vinyl iodide. The emission spectra and theoretical calculations indicate that HCN + CH 2O is the only significant product channel for the C 2H 3 + NO reaction near room temperature, in contradiction to several reports in the literature. Although CO emission is observed when vinyl bromide is used as the precursor, it arises from the reaction of NO with photofragments other than vinyl. This conclusion is supported by the absence of CO emission when vinyl iodide or methyl vinyl ketone is used. Prompt emission from vibrationally excited NO is evidence of the competition between back dissociation and isomerization of the initially formed nitrosoethylene adduct, consistent with previous work on the pressure dependence of this reaction. Our calculations indicate that production of products is dominated by the low energy portion of the energy distribution. The calculation also predicts an upper bound of 0.19% for the branching ratio of the H 2CNH + CO channel, which is consistent with our experimental results. © 2005 American Chemical Society.

Reactive wetting in the eutectic AgCu system is studied with molecular dynamics simulations. As Ag(l) spreads on the Cu surface, Cu dissolves into the liquid. The results for reactive wetting are compared to simulations in which no mixing is permitted, demonstrating that wetting kinetics are enhanced by dissolution reactions. The time dependent radius of the droplet R(t) is used to quantify kinetics for the wetting geometry of an infinitely long cylinder spreading on a substrate. Data show that, when dissolution is dominant, spreading is well described by R(t) ∼ (R0t)1/2, where R0 is the starting cylinder radius. Contact angle θ(t) data were calculated via a method that accounts for structure near the contact region and compared to data obtained using circular fits to the droplet profile. Significant differences were observed due to molecular scale structure that rapidly evolves near the contact line. This structure exhibits markedly lower θ than what is predicted from droplet profile data and it is proposed to exist throughout most stages of dissolutive wetting. Simulations of AgCu binary liquids spreading on Cu demonstrate that wetting kinetics decrease with increasing Cu in the liquid, further emphasizing that wetting kinetics are intrinsically linked to dissolution kinetics. After dissolution is complete, a Ag-rich monolayer of atoms advances diffusively across the Cu surface. © 2005 Published by Elsevier Ltd on behalf of Acta Materialia Inc.

Laser-extinction diagnostics can provide spatially and temporally resolved measurements of attenuation from combustion-generated soot within the path of the beam. When laser-extinction techniques are utilized in high-pressure combustion environments, however, a number of complications may be encountered that are not present in low-pressure environments. Several of these experimental difficulties were investigated in diesel engine environments, and solutions that facilitated acquisition of reliable laser-extinction data were demonstrated. Beam steering due to refractive index gradients within the combusting gases was observed, and a full-angle beam divergence of over 100 mrad was measured. A spatial-filtering scheme was employed to reduce the collection of forward-scattered light and background combustion luminosity while ensuring full collection of the steered beam. To further reject combustion luminosity, a narrow-bandpass laser-line filter was employed, after diffusing the transmitted light sufficiently to avoid the effects of significant spatial non-uniformities of the filter. As the windows were subjected to thermal and mechanical stresses, dynamic etaloning effects due to the photoelastic properties of synthetic fused silica were observed. Dynamic changes in the polarization of the exit beam were also observed, as stress-induced birefringence in the windows caused dynamic phase retardation of the transmitted beam. Although these photoelastic effects could not be eliminated, they were mitigated by introducing curvature to the wavefronts in the laser-extinction beam and using polarization-insensitive elements in the detection optics. Soot deposits on window surfaces were removed ablatively using a coaxial, high-energy, pulsed Nd:YAG laser beam.

Accelerated aging of Nylon 6.6 fibers used in parachutes has been conducted by following the tensile strength loss under both thermal-oxidative and 100% relative humidity conditions. Thermal-oxidative studies (air circulating ovens) were performed for time periods of weeks to years at temperatures ranging from 37 °C to 138 °C. Accelerated aging humidity experiments (100% RH) were performed under both an argon atmosphere to examine the 'pure' hydrolysis pathway, and under an oxygen atmosphere (oxygen partial pressure close to that occurring in air) to mimic true aging conditions. As expected the results indicated that degradation caused by humidity is much more important than thermal-oxidative degradation. Surprisingly when both oxygen and humidity were present the rate of degradation was dramatically enhanced relative to humidity aging in the absence of oxygen. This significant and previously unknown phenomena underscores the importance of careful accelerated aging that truly mimics real world storage conditions. Published by Elsevier Ltd.

The field history and current status of internal dosimetry is reviewed in this article. Elements of the field that are reviewed include standards and models, derivation of dose coefficients and intake retention fractions, bioassay measurements, and intake and dose calculations. In addition, guidance is developed and provided as to the necessity of internal dosimetry for a particular facility or operation and methodology for implementing a program. A discussion of the purposes of internal dosimetry is included as well as recommendations for future development and direction. Copyright © 2005 Health Physics Society.

This study compares two techniques for uncertainty quantification in chemistry computations, one based on sensitivity analysis and error propagation, and the other on stochastic analysis using polynomial chaos techniques. The two constructions are studied in the context of H 2-O 2 ignition under supercritical-water conditions. They are compared in terms of their prediction of uncertainty in species concentrations and the sensitivity of selected species concentrations to given parameters. The formulation is extended to one-dimensional reacting-flow simulations. The computations are used to study sensitivities to both reaction rate pre-exponentials and enthalpies, and to examine how this information must be evaluated in light of known, inherent parametric uncertainties in simulation parameters. The results indicate that polynomial chaos methods provide similar first-order information to conventional sensitivity analysis, while preserving higher-order information that is needed for accurate uncertainty quantification and for assigning confidence intervals on sensitivity coefficients. These higher-order effects can be significant, as the analysis reveals substantial uncertainties in the sensitivity coefficients themselves. © 2005 Wiley Periodicals, Inc.

This report is a review of open literature concerning threats including sabotage and theft related to fissile material transport in Japan. It is intended to aid Japanese officials in the development of a design basis threat. This threat includes the external threats of the terrorist, criminal, and extremist, and the insider threats of the disgruntled employee, the employee forced into cooperation via coercion, the psychotic employee, and the criminal employee. Examination of the external terrorist threat considers Japanese demographics, known terrorist groups in Japan, and the international relations of Japan. Demographically, Japan has a relatively homogenous population, both ethnically and religiously. Japan is a relatively peaceful nation, but its history illustrates that it is not immune to terrorism. It has a history of domestic terrorism and the open literature points to the Red Army, Aum Shinrikyo, Chukaku-Ha, and Seikijuku. Japan supports the United States in its war on terrorism and in Iraq, which may make Japan a target for both international and domestic terrorists. Crime appears to remain low in Japan; however sources note that the foreign crime rate is increasing as the number of foreign nationals in the country increases. Antinuclear groups' recent foci have been nuclear reprocessing technology, transportation of MOX fuel, and possible related nuclear proliferation issues. The insider threat is first defined by the threat of the disgruntled employee. This threat can be determined by studying the history of Japan's employment system, where Keiretsu have provided company stability and lifetime employment. Recent economic difficulties and an increase of corporate crime, due to sole reliability on the honor code, have begun to erode employee loyalty.

In this paper, we report the results of an experimental campaign to study the initiation, implosion dynamics and radiation yield of tungsten wire arrays as a function of the wire number. An optimization study of the X-ray emitted peak power, rise time and FWHM was effectuated by varying the wire number while keeping the total array mass constant at ∼5.8mg. The driver used was the ∼20MA Z-accelerator, in its usual short pulse mode of 100ns. We studied single arrays of diameter 20mm and height 10mm. The smaller wire number studied was 30 and the largest 600. It appears that 600 is the highest wire number achievable with present-day technology. Radial and axial diagnostics were used, including a crystal monochromatic X-ray backlighter. An optimum wire number of ∼370 was observed, which is very close to the number (300) routinely used for the ICF program in Sandia. © 2005 Taylor & Francis Group Ltd.

Oil caverns at the U.S. Strategic Petroleum Reserve (SPR) are subjected to geothermal heating from the surrounding domal salt. This process raises the temperature of the crude oil from around 75 F upon delivery to SPR to as high as 130 F after decades of storage. While this temperature regime is adequate for long-term storage, it poses challenges for offsite delivery, with warm oil evolving gases that pose handling and safety problems. SPR installed high-capacity oil coolers in the mid-1990's to mitigate the emissions problem by lowering the oil delivery temperature. These heat exchanger units use incoming raw water as the cooling fluid, and operate only during a drawdown event where incoming water displaces the outgoing oil. The design criteria for the heat exchangers are to deliver oil at 100 F or less under all drawdown conditions. Increasing crude oil vapor pressures due in part to methane intrusion in the caverns is threatening to produce sufficient emissions at or near 100 F to cause the cooled oil to violate delivery requirements. This impending problem has initiated discussion and analysis of alternative cooling methods to bring the oil temperature even lower than the original design basis of 100 F. For the study described in this report, two alternative cooling methods were explored: (1) cooling during a limited drawdown, and (2) cooling during a degas operation. Both methods employ the heat exchangers currently in place, and do not require extra equipment. An analysis was run using two heat transfer models, HEATEX, and CaveMan, both developed at Sandia National Laboratories. For cooling during a limited drawdown, the cooling water flowrate through the coolers was varied from 1:1 water:oil to about 3:1, with an increased cooling capacity of about 3-7 F for the test cavern Bryan Mound 108 depending upon seasonal temperature effects. For cooling in conjunction with a degas operation in the winter, cavern oil temperatures for the test cavern Big Hill 102 were cooled sufficiently that the cavern required about 9 years to return to the temperature prior to degas. Upon reviewing these results, the authors recommended to the U.S. Department of Energy that a broader study of the cooling during degas be pursued in order to examine the potential benefits of cooling on all caverns in the current degasification schedule.

Abstract not provided.

In October of 2003 experts involved in various aspects of homeland security from the Pacific region met to engage in a free-wheeling discussion and brainstorming (a 'fest') on the role that technology could play in winning the war on terrorism in the Pacific region. The result was a concise and relatively thorough definition of the terrorism problem in the Pacific region, emphasizing the issues unique to Island nations in the Pacific setting, along with an action plan for developing working demonstrations of advanced technological solutions to these issues. Since PacFest 2003, the maritime dimensions of the international security environment have garnered increased attention and interest. To this end, PacFest 2004 sought to identify gaps and enabling technologies for maritime domain awareness and responsive decision-making in the Asia-Pacific region. The PacFest 2004 participants concluded that the technologies and basic information building blocks exist to create a system that would enable the Pacific region government and private organizations to effectively collaborate and share their capabilities and information concerning maritime security. The proposed solution summarized in this report integrates national environments in real time, thereby enabling effective prevention and first response to natural and terrorist induced disasters through better use of national and regional investments in people, infrastructure, systems, processes and standards.

The report presented below is to appear in ''Electrochemistry at the Nanoscale'', Patrik Schmuki, Ed. Springer-Verlag, (ca. 2005). The history of the LIGA process, used for fabricating dimensional precise structures for microsystem applications, is briefly reviewed, as are the basic elements of the technology. The principal focus however, is on the unique aspects of the electrochemistry of LIGA through-mask metal deposition and the generation of the fine and uniform microstructures necessary to ensure proper functionality of LIGA components. We draw from both previously published work by external researchers in the field as well as from published and unpublished studies from within Sandia.