These are a few of the Laboratory's achievements during 2016 in ST&E.
Updated May 16th, 2017
Six Laboratory researchers have been elected as Fellows in their professional societies. Four of the six scientists were selected 2016 fellows of the American Physical Society (APS). Adam Bernstein was cited by the Division of Nuclear Physics for “pioneering work at the intersection of nuclear science and nuclear nonproliferation, including the development of antineutrino-based methods for monitoring the production of fissile material and large volume detectors for rapid screening of cargo for the presence of fissile material.” The Division of Plasma Physics recognized Hui Chen for “pioneering experimental research on relativistic positron generation using ultra-intense short-pulse lasers.”
Omar Hurricane, chief scientist of the Inertial Confinement Fusion Program, was cited by the Division of Plasma Physics for “visionary leadership in experiments on the National Ignition Facility laser and innovative work in understanding instabilities in high-energy-density and inertial-confinement-fusion plasmas leading to the first laboratory demonstration of an alpha-heating-dominated, thermonuclear plasma producing a fusion energy exceeding its total stored energy.” The Forum on Physics and Society acknowledged James Trebes for “contributions in laser physics and the application of physics to other disciplines, for leadership in multiple national security areas, and for contributions to education in the sciences and engineering.”
The Optical Society elected Manyalibo (Ibo) Matthews as a fellow. He was recognized by the society for his “outstanding contributions and sustained leadership in the field of high-power laser-induced damage science, laser-material interactions and processing, and vibrational spectroscopy-based materials characterization.” Chris Barty was named a 2017 Fellow of the Institute of Electrical and Electronics Engineers for his contributions to ultrahigh intensity lasers and the advancement of x-ray and gamma ray science.
Livermore won three 2016 R&D 100 awards from R&D Magazine. The awards honor the year’s best technological innovations. “This recognition in the R&D 100 competition is a great tribute to the innovative spirit of our scientists and engineers,” says Laboratory Director Bill Goldstein. “Teaming with industrial collaborators is an important element in ensuring that technologies developed here will be of benefit to the nation.”
The GLO (Gadolinium Lutetium Oxide) Transparent Ceramic Scintillator sharpens the quality of 3D x-ray images by substantially reducing the data acquisition time and improves the spatial resolution of images from x-ray computerized tomography scans. With this capability, scientists and engineers can improve the assessment and quality control of high-density parts like those used in power plant turbines and jet engines. Polyelectrolyte Enabled Liftoff (PEEL) technology is a robust, scalable method of fabricating stronger and thinner freestanding polymer films that are larger than conventional methods can produce. Livermore uses PEEL at its National Ignition Facility to fabricate membranes as thin as 30 nanometers that serve as compliant, load-bearing elements for laser targets. The Carbon Capture Simulation Initiative (CCSI) toolkit consists of a suite of computational tools and models to accelerate the development of carbon capture technology for manufacturers and businesses. Four national laboratories including Livermore and five universities developed CCSI.
Livermore researchers have identified a mechanism that causes low clouds to respond differently to global warming, depending on their spatial pattern and location. The results imply that studies relying solely on recent observed trends underestimate how much Earth will warm from increased carbon dioxide. The research appears in the Oct. 31, 2016 edition of Nature Geoscience.
Clouds influence Earth’s climate by reflecting incoming solar, and reducing outgoing thermal radiation. As the Earth’s surface warms, clouds contribute a feedback to the climate system. If they increase the radiative cooling of the Earth, they provide a negative feedback, reducing warming. Otherwise, they act as a positive, amplifying warming. The magnitude of global warming depends on the sign and magnitude of the cloud feedback. Livermore researchers showed that the strength of the cloud feedback simulated by a climate model fluctuates tremendously depending on the time period. Over the long term, cloud feedback strengthens, but over the last 30 years, negative cloud feedback reduced global warming. Low-level clouds in the tropics caused this effect, strongly cooling the planet by reflecting solar radiation to space. “With a combination of climate model simulations and satellite observations, we found that the trend of low-level cloud cover over the last three decades differs substantially from that under long-term global warming,” says lead author Chen Zhou. The Office of Science at the U.S. Department of Energy supported this work.
Livermore researchers have improved the radiation drive environment of “high-foot” indirect-drive experiments at the National Ignition Facility (NIF), which is critical to achieving a symmetrical implosion of the target capsule, and eventually, to igniting nuclear fusion. In a Physical Review Letters paper published on November 25, 2016 they reported that the use of “LLL” hohlraums—longer hohlraums with a larger ratio between the diameter of the hohlraum and the capsule diameter (the “case-to-capsule” ratio), and lower gas-fill density—significantly improves the radiation drive environment and thus symmetry control of a high-foot implosion, resulting in enhanced implosion performance. For the first time, the LLL hohlraums also reduced the amount of energy-sapping hot electrons generated by laser-plasma interactions to below levels for concern. Laser energy coupling to the hohlraum notably increased, and discrepancies with simulated radiation production were markedly reduced.
“At fixed laser energy, high-foot implosions driven with this improved hohlraum have achieved a 1.4× increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50 percent as compared to a reference experiment with the same laser energy…we will be looking for ways to further exploit these results in future experiments,” the researchers report. The experiments have enhanced scientific understanding of high-foot and other x-ray-driven implosions. The U.S. Department of Energy funded this research.
Livermore’s Additive Manufacturing Initiative researchers are part of a group that has developed 3D printed materials with a unique property: instead of expanding when heated, they shrink. In a study published in the October 21, 2016 issue of Physical Review Letters, Livermore engineers, and others from the University of Southern California, MIT, and the University of California, Los Angeles, describe the 3D printing of lightweight metamaterials with negative thermal expansion that can be “tuned” to shrink over a large range of temperatures. “This is a new version of a printing method we have developed and used in the past. We used it to create a thermomechanical metamaterial that may enable applications not possible before,” says principal investigator Chris Spadaccini, director of Laboratory’s Center for Engineered Materials and Manufacturing. “It has thermomechanical properties not achievable in conventional bulk materials.”
The researchers demonstrated a bi-material microlattice structure printed from polymer and a polymer/copper composite material that can flex inward, causing the structure to contract when exposed to heat over a range of tens to hundreds of degrees. The study may be the first experimental demonstration showing high tunability of negative thermal expansion in three Cartesian directions of microlattice structures. Possible applications for the metamaterials could come in securing parts that tend to move out of alignment under varying heat loads, such as microchips and high-precision optical mounts. The U.S. Department of Energy funded Livermore’s participation in this work.
Livermore researchers have developed a new type of optical fiber amplifier that could potentially double the information-carrying capacity of fiber-optic cables. The fiber shows significant positive optical gain from 1,390 to 1,460 nm. It generates laser power and optical gain with relatively good efficiency. This discovery opens up the potential for installed optical fibers to operate in a transmission region known as E-band, in addition to the C and L bands where they currently operate, effectively doubling a single optical fiber’s information-carrying potential. Using this fiber, it is possible to build a set of optical fiber amplifiers that would look virtually identical in technology to the fiber amplifiers that already exist. Instead of having to lay another expensive cable, these new amplifiers could be installed in the same buildings as the current amplifiers, resulting in twice as much bandwidth on the current cables, increasing the telecom industry’s transmission capacity.
“The key missing component for operating a telecom network in this wavelength region has been the optical fiber amplifier,” says Jay Dawson, deputy program director for Department of Defense Technologies in the National Ignition Facility and Photon Science Directorate. Initially started as a Laboratory Directed Research and Development project (14-ERD-078), the research is now funded by the Industrial Partnerships Office’s Innovation Development Fund.
Livermore engineers have achieved unprecedented scalability in 3D-printed architectures of arbitrary geometry, opening the door to super-strong, ultra-lightweight, and flexible metallic materials for aerospace, the military, and the automotive industry. In a study published online July 18 in Nature Materials, Laboratory engineers report building multiple layers of fractal-like lattices with features ranging from the nanometer to centimeter scale, resulting in a nickel-plated metamaterial with a high elasticity not found in any previously built metal foams or lattices. Metamaterials are synthetic composites with engineered properties that generally do not exist in natural materials.
Prior to this achievement, no one had been able to scale up 3D features from the nanoscale to see how they behave. The lattices were initially printed out of polymers, using a one-of-a-kind Large Area Projection Micro-Stereolithography printer invented by Livermore engineer Bryan Moran, who won an R&D 100 award for the design. The lattice structure was then coated with a nickel-phosphorus alloy and then processed to remove the polymer core, leaving extremely lightweight, hollow tube structures of the alloy. 3D additively manufactured materials have direct application in the Laboratory’s stockpile stewardship mission, as well as in a broad array of applications requiring materials whose properties, such as compression, tension, and shear, can be tuned. The Laboratory Directed Research and Development program funded this research (15-LW-083), together with the Defense Advanced Research Projects Agency (DARPA) and a Virginia Tech startup.
Scientists have found that changes in cloud patterns during the last three decades match those predicted by climate model simulations. These cloud changes are likely to have had a warming effect on the planet. The research from Livermore, Scripps Institution of Oceanography, University of California, Riverside, and Colorado State University appears in the journal Nature.
Records of cloudiness from satellites originally designed to monitor weather are typically plagued by erroneous variability related to changes in satellite orbit, instrument calibration, and other factors. In order to combat these inconsistencies, the team used a new technique to remove the variability from the records. The corrected satellite records exhibited large-scale patterns of cloud change between the 1980s and 2000s that are consistent with climate model predictions, including retreat of mid-latitude storm tracks towards the poles, expansion of subtropical dry zones, and increasing height of the highest cloud tops. “After the spurious trends were removed, we saw consistent responses among several independent datasets and with model simulations,” says Mark Zelinka, a Livermore scientist and co-author of the paper. “That is a nice confirmation of the models’ predictions, at least for the types of cloud changes that models agree on.” The National Oceanic and Atmospheric Administration, the Department of Energy Office of Science, and NASA funded the research.
Researchers from Lawrence Livermore, the University of Melbourne, and the U.S. Geological Survey, have found a way to reveal potential microbially mediated mercury methylation (the formation of toxic methylmercury through anaerobic bacterial processes) in polar marine environments. To explore mercury methylation sources, they combined measurements of total and methylated mercury with metagenomic analysis (genomic analysis from environmental samples) of whole-community microbial DNA from Antarctic snow, brine, sea ice, and seawater. Their research paper appears in the journal Nature Microbiology.
Atmospheric deposition of mercury onto sea ice and seawater in the polar regions provides mercury for microbial methylation and contributes to the bioaccumulation of the neurotoxin methylmercury in the marine food web. Scientists are concerned that methylmercury stored in the fatty tissues of fish will accumulate enough mercury to pose a health hazard to humans. Little is known about the controls on microbial mercury methylation in polar marine systems, but mercury methylation is known to occur alongside photochemical and microbial mercury reduction. The scientists’ research identified the marine bacterium Nitrospina as a potential mercury methylator within sea ice.
The Department of Energy’s Office of Science funded this work.
A team of Livermore researchers has developed protective yet breathable membrane materials featuring small-diameter (less than 5 nanometers) carbon nanotubes (CNT) as moisture-conductive pores. The membranes provide water vapor transport at a rate 20 times faster than those predicted by conventional gas diffusion theories, surpassing commercial breathable fabrics such as Gore-Tex. Their findings are described in a paper featured on the back cover of the July printed issue of the journal Advanced Materials.
The team reported that these new CNT membranes can efficiently block biological threats such as Dengue virus because their size prevents them from passing through. Future work will aim to encode the membrane with a smart and dynamic response to chemical hazards, which could lead to a new paradigm of adaptive, breathable, and protective materials. The work was supported by the Defense Threat Reduction Agency’s “Dynamic Multifunctional Materials for a Second Skin” program and the Laboratory Directed Research and Development program.
Livermore researchers and their colleagues have used a new experimental technique to measure the total hydrodynamic instability growth near peak velocity (about 900,000 mph or 1,400,00 km/h) of a National Ignition Facility (NIF) implosion. Their research was published online in the journal Physical Review Letters. A NIF implosion has two distinct phases—an acceleration phase and a deceleration (rebound shock) phase, both of which are unstable. For the experiment, scientists used special target capsules with pre-imposed sinusoidal modulations, or “ripples,” on the capsule surface. They measured the growth of hydrodynamic instabilities as a function of the frequency, or “mode” of the ripples (the number of ripples inscribed on the capsule).
To view the state of the implosion at peak velocity, the researchers employed a novel technique designed by Livermore physicist Bruce Hammel. They added a small amount of argon to the gas in the plastic capsule to enhance the x-ray emissions from the central hot plasma created during the shock rebound phase, effectively resulting in self-radiography. This technique allowed the scientists to achieve the highest direct measurement of hydrodynamic growth in any inertial confinement fusion experiment to date—an areal density (mass per unit area) amplification of 7,000x. The purpose of the work is to help NIF researchers to better understand hydrodynamic instabilities that inhibit nuclear fusion ignition, and develop strategies to remove this obstacle to fusion.
Livermore researchers and partners have developed the first-ever biological identification method that exploits the information encoded in proteins of human hair. Scientists from Lawrence Livermore and a Utah startup company, Protein-Based Identification Technologies, LLC, have developed the groundbreaking technique. Their work, currently funded by the Department of Defense and the Laboratory Directed Research & Development program, is described in a paper in the online journal PLOS ONE.
The method will offer another tool to law enforcement authorities for crime scene investigations as well as to archaeologists, since the technique can detect protein in human hair more than 250 years old. In their study, the researchers examined male and female hair samples of 66 European-Americans, 5 African Americans, 5 Kenyans, and 6 skeletal remains from the 1750s and 1850s, finding a total of 185 protein markers. The protein markers used by the scientists are variants resulting from amino acid substitutions that stem from DNA mutations, also known as single amino acid polymorphisms. Each person’s number of hair protein markers combined with their pattern of protein markers is unique, so researchers are able to provide a distinct pattern for an individual that would distinguish that person among a population of one million. The researchers’ ultimate goal is to establish a set of 90–100 protein markers that would identify an individual among the world’s population using a single hair—providing law enforcement with the capability of identifying remains that no current technique allows.
A recent experiment conducted on the Janus laser at Livermore’s Jupiter Laser Facility has established the feasibility of plasma-based lasers. Such devices, based on the interaction of plasma—a medium consisting of freely moving ions and free electrons—and lasers, are ultrafast, more damage-resistant than conventional optics, and easily tunable. Developing high-power lasers with greater control over beam characteristics is essential to Livermore’s pursuit of inertial confinement fusion (ICF), and science-based stockpile stewardship to ensure the safety and reliability of the nuclear deterrent.
In a Physical Review Letters paper published online on May 18, 2016, Livermore researchers and colleagues report on the first experimental demonstration of a high-power plasma wave plate, a device used to modify the polarization, or electric-field orientation, of an independent probe laser beam. The experiment indicates that high-power, tunable laser–plasma photonic devices operating at intensities millions of times greater than those withstood by traditional (crystal-based) optics are possible. The work could have an impact on laboratory astrophysics and particle accelerators as well as on inertial confinement fusion experiments at Livermore’s National Ignition Facility—plasma-based optical components could be used to redirect, focus, and improve the contrast of laser beams, to tune the implosion symmetry of ICF targets by facilitating power transfer between intense lasers and other components. The Laboratory Directed Research and Development (LDRD) supported this research.
For the first time, Livermore researchers have shown that carbon nanotubes as small as 0.8 nanometers diameter can transport protons faster than bulk water, by an order of magnitude. The research validates a 200-year-old mechanism of proton transport. The transport rates in these nanotube pores, which form one-dimensional water wires, also exceed those of biological channels and man-made proton conductors, making carbon nanotubes the fastest known proton conductor. The research appears in the April 4, 2016, online edition of the journal Nature Nanotechnology.
When water is forced into the nanotube, protons move through that water even faster than through normal or bulk water. Livermore scientists used carbon nanotube pores to line up water molecules into perfect one-dimensional chains. The proton motive force is a major factor in many biological processes such as energy production and storage in bacteria, and respiration. Unfortunately, synthetic proton conductors have lagged behind their biological counterparts because of the difficulty of forming and maintaining the structured one-dimensional water chains that enable proton hopping. The Livermore research could advance the development of practical applications such as improved proton exchange membranes in fuel cells, proton-based signaling in biological systems, and the emerging field of proton bioelectronics (protonics). The U.S. Department of Energy’s Office of Basic Energy Sciences supported this work.
One of the key research goals at Livermore’s National Ignition Facility (NIF) is demonstrating inertial confinement fusion ignition for both stockpile stewardship and as a potential source of clean energy. A paper published in the April 11, 2016, online issue of the journal Nature Physics reviews recent progress towards this goal. In the paper, Livermore scientists and colleagues analyze the series of National Ignition Facility “high-foot” inertial confinement fusion (ICF) experiments conducted in 2013 and 2014 that reached the highest levels of alpha heating ever achieved on any laser facility. Alpha heating, or self-heating, is a key step on the path to ignition in which the deuterium–tritium fusion reaction products deposit their kinetic energy locally within the fusion reaction region, thus increasing the temperature there and continually reinforcing the reaction rate.
The alpha particle heating of the plasma dominated, with the produced fusion yield exceeding that of the work done by the compression of the fuel alone. Recent three-dimensional simulations of the fusion targets have shown reasonable agreement with the experimental results and suggest that an improved understanding of the implosions is emerging that can be used to guide future work. Current ICF experiments are working toward the goal of increasing implosion densities and temperatures by a factor of two to four, which researchers estimate is the threshold for ignition. The National Nuclear Security Administration funds NIF.
Livermore material scientists have found that 3D-printed foams have higher durability and better long-term mechanical performance than standard cellular materials. The research appears in the April 27, 2016, edition of Scientific Reports. Foams, also known as cellular solids, are an important class of materials with applications ranging from thermal insulation and shock-absorbing support cushions to lightweight structural and flotation components. Foams are essential in the automotive, aerospace, electronics, marine, biomedical, packaging, and defense industries. At Livermore, better foam materials through advanced materials and manufacturing research have applications to national security missions in such areas as stockpile stewardship science, and energy. Traditionally, foams are created by processes that lead to a highly non-uniform structure with significant variety in size, shape, thickness, connectedness, and topology of constituent cells.
To develop an improved alternative, Laboratory researchers demonstrated the feasibility of 3D-printing uniform foam structures through the direct-ink-write process. Their research examined the long-term mechanical stability of 3D-printed foams through accelerated aging experiments, subjecting samples of traditional foam and 3D-printed materials to elevated temperatures under constant compressive strain. They monitored the stress condition, mechanical response, and permanent structural deformation of each sample for one year or more, and quantitatively modeled the evolution of these properties over decades. The study convincingly demonstrated that 3D-printed materials age slowly—they better retain their mechanical and structural characteristics compared to their traditional counterparts.
In a paper published in the April 15, 2016, edition of Nature Communications, a multi-institutional team including nine Livermore researchers present spectrally resolved x-ray scattering measurements on dynamically compressed deuterium. Hydrogen, the most abundant element found in the universe, has applications to planetary science, inertial confinement fusion, and fundamental physics, and therefore, its high-pressure properties have been the subject of intense study. However, questions about hydrogen’s high-pressure phase diagram have remained unresolved.
The team determined deuterium’s ionization state as a function of pressure. The onset of ionization occurs at about three times compression, close in pressure to where density functional theory–molecular dynamics simulations predict molecular dissociation, suggesting that hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase. This work is important to understanding the physics of the interiors of giant planets such as Jupiter, where details of hydrogen’s dissociation under pressure and its transition to electrical conductivity influence the processes that result in planetary magnetic fields. The research also advances implosion modeling at Livermore’s National Ignition Facility, where designers must understand the high-pressure properties of hydrogen in order to produce targets that enable progress toward fusion ignition. Livermore’s Laboratory Directed Research and Development program supported this research.
In a paper appearing in the April 12, 2016, issue of Physical Review B, a team of researchers from Lawrence Livermore and Sandia national laboratories present an absolute pressure–density relationship for elemental copper up to 450 gigapascals (GPa), extending the previous 250-GPa calibration. Copper is an important material for the engineering and academic communities and is often used at Sandia’s Z pulsed-power facility as an electrode for materials dynamics experiments, at Livermore’s National Ignition Facility (NIF) as an ablator, and within the diamond-anvil-cell community as a high-pressure standard.
Using the Z facility, the team leveraged magnetically driven uniaxial compression waves to compress thick copper samples to more than 450 GPa (approximately 4.4 million times surface atmospheric pressure). They determined the stress-density compression path from sound velocity measurements. In this paper, the team presents a method for correcting for the effects of strength and heating caused by plastic deformation. They show that their technique is inherently more accurate at high pressures than current methods. These results should provide the community of static high-pressure researchers with an easy-to-use pressure standard at extreme conditions. The National Nuclear Security Administration (NNSA) funds Sandia’s Z machine and Livermore’s NIF, two of NNSA’s experimental capabilities that are essential components of assessing nuclear performance issues as part of the stockpile stewardship program.
The Presidential Early Career Award for Science and Engineering (PECASE) is the highest honor bestowed by the U.S. government on science and engineering professionals in the early stages of their independent research careers. Lawrence Livermore astrophysicist Tammy Ma was selected for a PECASE award, one of 106 recipients nationwide and one of 13 from the Department of Energy. Ma was recognized for her “innovation and leadership in quantifying hydrodynamic instability mix in the hot spot of inertial confinement fusion implosions on the National Ignition Facility (NIF); key contributions to experiments demonstrating fusion fuel gains exceeding unity; and broad educational outreach and service to the scientific community.” In addition, former LLNL engineering postdoc Jonathan Hopkins was awarded a PECASE, largely for work he did as an LLNL postdoc. Hopkins is currently an assistant professor of mechanical engineering at the University of California, Los Angeles. After earning her Ph.D. from the University of California, San Diego, Ma completed a postdoc at LLNL before becoming a staff scientist in 2012, where she currently heads the X-Ray Analysis Group for the inertial confinement fusion (ICF) program.
Fundamental to Lawrence Livermore’s primary mission of ensuring the safety, security, and reliability of the nation’s nuclear stockpile is obtaining a better understanding of the shape, structure, stability, and behavior of atoms, particularly under extreme conditions. In an effort to find evidence of rare octupole deformation—pear-shaped atomic nuclei—an international team including Livermore postdoc Brian Bucher and scientist Ching-Yen Wu performed experiments on the Argonne Tandem Linac Accelerator System at Argonne National Laboratory. The accelerator generates high-intensity, high-energy beams to shed light on the structure of atomic nuclei. The team found evidence that the neutron-rich nuclei of Barium–144 are “squashed” or pear-shaped. In a March 18, 2016, paper in Physical Review Letters, first-author Bucher and the research team described their experiments. The team’s experimental results show the barium nuclei appear to be considerably more deformed than predicted by theory. Confirmation of these observations may require scientists to revise their current understanding of octupole deformation. Postdoc Bucher’s research is focused on the structure of how nuclei evolve with the addition or subtraction of individual nucleons; he is particularly interested in how nuclear structure influences astrophysical processes. The primary funding for the octupole deformation research was provided by the Department of Energy’s Office of Science.
For more than two decades, LLNL researchers have worked to understand and mitigate climate change. Quantifying how much heat is accumulating in the ocean is critical to understanding climate change because the ocean absorbs more than 90 percent of Earth’s excess heat associated with global warming. Livermore scientists, together with colleagues from the National Oceanic and Atmospheric Administration, Princeton University, and Pennsylvania State University, have found that half of the global ocean heat content increase since 1865 has occurred during the past two decades and that the warming is reaching deeper into the ocean. Livermore researcher Peter Gleckler was lead author of a paper published in the January 18, 2016 online journal Nature Climate Change. The paper detailed a study that combined a diverse set of historical observations together with current climate models to identify changes in the ocean greater than 700 meters depth. The analysis suggests that nearly half of the industrial-era increases in global ocean heat content have occurred in recent decades, with over a third of the accumulated heat occurring below 700 meters. The estimates of ocean warming are consistent with results from the latest generation of climate models. Livermore’s contribution to the study was funded by the Department of Energy’s Office of Science.
Livermore scientists have been among the leaders in adopting, advancing, and demonstrating the capabilities of additive manufacturing, also called three-dimensional (3D) printing. In this revolutionary process, objects are built up one ultra-thin layer at a time. Researchers from LLNL and the University of California Santa Cruz achieved an important milestone when they used a 3D printer to manufacture grapheme aerogel supercapacitors that are extremely stable and capable of nearly fully retaining their energy capacity even after 10,000 consecutive charging and discharging cycles. The results were released online in the journal Nano Letters on January 28, 2016. The experimenters used a 3D-printing process called direct-ink writing and an extrudable graphene-oxide composite ink designed at LLNL. Graphene-based inks feature ultrahigh surface area, lightweight properties, elasticity, and superior electrical conductivity. The novel LLNL graphene composite ink has an engineered porous (aerogel) architecture. The researchers predict that future 3D-printed supercapacitors may make possible new products that are currently difficult or impossible to manufacture using other methods. Examples include efficient energy storage systems for smartphones, wearables, implantable devices, electric cars, and wireless sensors. Livermore’s Laboratory Directed Research and Development program funded this work.
A major security concern is the threat of nation-states or terrorists obtaining radiological or nuclear materials for illicit purposes. To help address this threat, Lawrence Livermore researchers have applied their expertise in nuclear weapons and isotopes to the discipline of nuclear forensics. In this field, investigators analyze nuclear or radioactive materials for clues to a material’s source to identify where legal control was likely lost. In an article appearing on the cover of the February 2, 2016, issue of Analytical Chemistry, LLNL researchers Mike Kristo and Ruth Kips, in collaboration with colleagues at the Australian Nuclear Science and Technology Organization, described the current science of nuclear forensics, including work performed at Lawrence Livermore under several sponsors. The team cited examples of nuclear forensic signatures that allowed investigators to identity unknown nuclear material. Signatures describe material characteristics such as isotopic abundances, elemental concentrations, physical and chemical forms, and physical dimensions that can link a material to individuals, locations, or processes. There is currently no single nuclear forensic signature capable of identifying all unknown nuclear materials. This fact reflects the diverse materials that make up the nuclear fuel cycle, from natural materials such as uranium ores to highly processed materials such as nuclear fuels. Therefore, scientists must apply analytical techniques from several disciplines, including analytical chemistry, radiochemistry, and materials science.
Additive manufacturing, or three-dimensional (3D) printing, holds great promise as a way to tailor material behavior. In research illustrated on the cover of the March 9, 2016, issue of Advanced Materials, a team of Livermore and Harvard researchers demonstrated that 3D printing can be used to tailor the dynamic behavior of reactive materials, which produce controlled releases of energy, as in airbag initiation. The team created two different reactive material architectures—channels and hurdles, both composed of silver nanoparticle ink. The team used 3D printing to create conductive electrodes from the ink, and then used electrophoretic deposition to coat them with aluminum/copper oxide thermite films. The channel and hurdle architectures offered different orientations of the multiphase expansion event relative to the flame propagation direction. Observations revealed that the precise spacing and orientation of these architectures played an important role in manipulating the resultant energy transport, offering a pathway for tailoring the energy release rate apart from the conventional method of changing the mixing scale or formulation. The researchers suggest that controlling reactivity using architected design will lead to new types of materials for initiation systems, propellants, and pyrotechnics. This work was funded by the Laboratory Directed Research and Development Strategic Initiative Program.