Highlights of 2007 LDRD Accomplishments

In FY07, the LDRD Program at LLNL continued to be extremely successful in achieving its goals of scientific discovery, providing new concepts for core missions, and creating an exciting research environment that attracts outstanding young talent to the Laboratory. Below are five FY07 highlights that exemplify LDRD’s noteworthy research results, timely support for the Laboratory’s science and technology plan as well as critical national needs, and external recognition of Laboratory personnel.

Transformational Materials Initiative. This project is developing science and technology to help make the U.S. nuclear weapons complex smaller, safer, and more agile. It will also help ensure the continued success of the Stockpile Stewardship Program—one of the Laboratory’s key missions. To this end, the project team is creating new materials, processes, and diagnostics to reduce cost and time required to produce and maintain the stockpile, enhance weapon safety, ensure future stockpile longevity, and optimize stockpile performance. The multidisciplinary team combines capabilities in materials synthesis, characterization, theory, and modeling to deliver cutting-edge advances in high explosives, multifunctional materials, metals, and sensing.

Livermore’s Transformational Materials Initiative team combines expertise in materials synthesis, characterization, theory, and modeling to advance the technology of high explosives, multifunctional materials, metals, and sensing. Their goal is to ensure the continued success of the Stockpile Stewardship Program by enabling a smaller, safer, and more agile U.S. nuclear weapons complex.

Achievements made in FY07 include preparing a new explosive composite with improved quality, completing new simulations of shocked high explosives, preparing test specimens of advanced metals, developing three sensing technologies, and conducting preliminary testing of a capability to monitor criteria of interest. High-explosive loading results showed novel and promising results in material ductility.

The team’s ambitious plans for FY08 include scaling up the manufacture of the new high explosives to the kilogram level to test detonation and low-temperature mechanical properties, extending first-principles studies on the detonation of nitromethane to triamino-trinitro-benzene, demonstrating communication to a microelectromechanical systems-based load sensor for realistic materials, refining simulations and understanding of the effects of processing parameters on high-explosives loading response, and synthesizing a unified, catalytically active polymer nanocomposite.

Nonequilibrium Phase Transitions. The study of phase transitions in an extreme, nonequilibrium regime is a scientific frontier that holds promise for discovering new phases, metastable states, chemical reaction pathways, and biological functioning processes. The team is examining lattice disordering and melting, quantifying the role of electronic excitation on phase-transition kinetics, and developing approaches in finite-temperature condensed matter for constructing an equation of state. In collaboration with the University of Toronto, the project is using measurements to correlate optical and structural properties under ultrafast laser excitation to help develop density functional theory approaches.

For the first systematic study of phase transitions in an extreme, nonequilibrium regime, researchers have demonstrated a 30-nm-thick freestanding gold nanofoil that is heated with a femtosecond, 400-nm laser beam (blue) to produce a nonequilibrium, high-energy-density state. It is then probed by a frequency-chirped, broadband (450- to 800-nm) laser beam (blue to red) in reflection and transmission measurements.

Deliverables include time-correlated data on materials’ optical and structural properties. The data will be generated by tracking solid–liquid to liquid–plasma transitions under ultrafast excitation conditions and will be used to benchmark quantum simulations. This will lead to a new understanding of the connection between electronic (optical) and atomistic (structural) behavior, opening up possibilities of manipulating phase stability and boundary. Success in this area also will help elucidate the convergence of condensed matter and plasma physics, a critically missing link in basic scientific understanding. This work supports the Laboratory’s mission in stockpile stewardship.

In FY07 the team completed a 600-femptosecond, 30-kiloelectronvolt electron gun and demonstrated the viability of single-shot, ultrafast electron diffraction measurement with gold nanofoils heated by a 400-nm laser beam. In addition, new findings elucidated ionization dynamics and nonequilibrium effects on phonon modes. Overall, the project’s most notable achievement is the discovery of quasi-steady states of superheated lattice with highly excited nonequilibrium electrons. This fundamentally changes the existing understanding of warm dense matter produced by ultrafast excitation of a solid using laser x-ray-charged particles. The team also discovered the persistence of band structure in athermally melted metals, which was prominently featured in journals such as Nature of Materials News. These achievements played a large part in the project’s principal investigator receiving an LLNL Science and Technology Award.

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Finding and Characterizing Rare Events in Two Next-Generation Particle Astrophysics Experiments. This project team is collaborating on a larger effort to resolve one of the most important scientific issues of the 21st century—direct detection of dark matter. Another goal is measurement of the neutrino-oscillation parameter theta 13, which has nearly the same level of scientific significance. To this end, the team is building detectors with unprecedented levels of sensitivity and with record low levels of systematic error. The skills being developed in this project have direct relevance to Laboratory global nuclear-security missions. In particular, the advanced simulation capabilities, event-selection algorithms, and advanced detection concepts being pursued have immediate relevance to ongoing reactor monitoring and special nuclear material detection efforts by the DOE and the Department of Homeland Security. In addition, this project increases LLNL’s already significant competency in the detection of antineutrinos—which are a potentially valuable signature for reactor monitoring and treaty verification—and will be concurrently applied to nonproliferation efforts.

At the San Onofre Nuclear Generating Station, the team is working to measure an as-yet undetected antineutrino interaction process, known as coherent neutrino–nucleus scattering. To this end, the team has deployed a radiation detector with unprecedented sensitivity to low-energy nuclear recoils. The detector contains a noble liquid target and is being used to measure the faint but high-probability coherent scatter that induces these recoils. The high rate per unit volume of this weak signal allows a ten- to hundred-fold reduction in the size of the detector, making tabletop antineutrino detection a realizable goal in the coming years.

Louisiana State University collaborator William Coleman, LLNL principal investigator Adam Bernstein, and LLNL co-investigator Steve Dazeley (left to right) with a prototype gadolinium-doped water Cerenkov antineutrino detector developed to explore rare events in next-generation particle astrophysics. The device detected antineutrinos emitted from the San Onofre Nuclear Generating Station. Antineutrinos interacting in the water generate a unique pattern of faint blue flashes of Cerenkov light, which the detector records.

In FY07, the team achieved a world-record limit on the detection of supersymmetric dark matter in a liquid-xenon detector, beating the previous record by nearly an order of magnitude. The limit was set with a 10-kg dual-phase xenon detector and the results published in Physical Review Letters. In collaborating with other organizations, the team also began planning a 300-kg xenon detector for the Homestake Deep Underground Science and Engineering Laboratory in South Dakota. This includes designing the electronics and simulating the performance of the 300-kg detector. A custom detector Monte Carlo capability was also developed for detailed calibration studies with the Double Chooz detector in France.

In FY08, the team will simulate, assemble, and deploy a prototype of the 300-kg dark-matter detector and perform simulation and design work for a 2-m-diameter gadolinium-doped water shield to screen backgrounds from this highly sensitive detector. Simulation capability for the Double Chooz antineutrino detector will also be expanded.

Biological Imaging with Fourth-Generation Light Sources. Groundbreaking experiments have been proposed to test key concepts of single-molecule x-ray free-electron laser (XFEL) imaging, including measurement of the Coulomb explosion of particles in intense ultrashort x-ray beams, lensless x-ray imaging beyond the radiation-damage limit, and manipulation and orientation of single particles in space and time to interact with XFEL pulses. The experimental results will be compared with high-fidelity modeling to understand how to use XFEL to determine the atomic structure of biological macromolecules, protein complexes, viruses, and spores. Specific goals are to determine the duration and fluence of XFEL pulses required for single-molecule imaging, demonstrate image-reconstruction methods, and perform ultrahigh-resolution three-dimensional imaging of container-free particles.

Single-molecule imaging will further LLNL’s missions in both biodefense and bioscience to improve human health. In addition, improved tomography algorithms developed will benefit stockpile stewardship, such as diffraction imaging techniques applicable to the study of warm dense matter. This research will also enhance the capabilities of the Linac Coherent Light Source (LCLS) beyond the baseline design, a high-priority project of the DOE Office of Science, in support of LLNL’s mission in breakthrough science and technology.

A technique was demonstrated for reconstructing the image of an experimental sample using scattered x-rays at the beginning of a single 25-femtosecond soft x-ray pulse generated by a free-electron laser, as featured on the December 2006 cover of Nature Physics. The 1-μm stick figures were patterned onto a silicon nitride film, and their images were captured just moments before evaporating at a temperature of 60,000 K. The biological imaging project is working to determine the atomic structure of biological macromolecules, protein complexes, viruses, and spores.

In FY07, the project team achieved a major milestone—the first-ever demonstration of the ultrafast diffractive x-ray imaging of free injected particles. They also characterized their injection system at the FLASH free-electron laser facility in Germany and found it capable of carrying out experiments at higher resolution at the upcoming LCLS. Images of injected living hydrated biological cells and test particles were reconstructed. The method of time-delay holography was also improved; these results were featured on the cover of Nature Physics.

In FY08, the team will take advantage of the increased x-ray penetration of FLASH to image biological cells beyond radiation-damage limits. They will also increase the efficiency of the particle injection system and diagnostics for use in the three-dimensional imaging of reproducible structures, which will be done with gold rod nanoparticles and asymmetric virus particles; further develop time-resolved imaging methods (including the tomographic time-resolved imaging of ablation); measure the effect of a tamper on XFEL-induced particle explosion; and develop a plan for the first experiments at the LCLS based on FLASH experiments and modeling.

Separation of Carbon Dioxide from Flue Gas Using Ion Pumping. Reducing carbon dioxide emissions is a crucial, high-profile aspect of the Laboratory’s mission in environmental management. The main barrier to lowering carbon emissions generated during energy production is the lack of a cost-effective means of separating carbon dioxide from combustion sources. This project is investigating the possibilities of separating carbon dioxide from flue gas by ionic pumping of carbonate ions dissolved in water. The ion pump dramatically increases dissolved carbonate ion in solution and hence the overlying vapor pressure of carbon dioxide gas, allowing its removal as a pure gas. This novel approach to increasing the concentration of extracted gas permits new approaches to treating flue gas, because the slightly basic water used as the extraction medium is impervious to the trace acid gases that destroy existing solvents used in conventional methods, and no pre-separation is necessary. Modeling and laboratory experiments will demonstrate the chemistry of the method, which is expected to offer a dramatically improved solution for removing carbon from hydrocarbon combustion at power plants.

In FY07 the team successfully demonstrated that their method works at flue-gas concentrations—a significant milestone. They also addressed another significant hurdle for large-scale implementation by demonstrating that the method can be implemented with any of the three most widely used water desalinization technique’s: reverse osmosis, electrodialysis, or thermal distillation. These two accomplishments represent a major step forward in validating this method’s economic utility.

Work in FY08 will focus on using the ion pump as a carbon dioxide concentrating mechanism. Gas and fluid flow will be tested in multiple-plate ion pumps to determine whether the plate materials can be optimized for the carbon separation method. A major goal is to determine the parameters necessary for a pilot-scale test of the technology. The team will also investigate the feasibility of producing drinking water during the carbon-separation process, which would further enhance the method’s economic viability.

A proposed method for lowering carbon emissions generated during energy production. Flue gas is first dissolved in slightly alkaline water, which passes into the ion pump to produce a concentrate from which carbon dioxide is released. Phosphate is added to buffer pH and increase carbon dioxide carrying capacity. The concentrate is recycled to the water wash, and nitrate and sulfate will be concentrated with the bicarbonate and either removed separately as solids or evolved in gas form.

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