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  • richardmitnick 12:20 pm on October 10, 2018 Permalink | Reply
    Tags: , , ORNL, Scientists forge ahead with electron microscopy to build quantum materials atom by atom,   

    From Oak Ridge National Laboratory: “Scientists forge ahead with electron microscopy to build quantum materials atom by atom” 

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    From Oak Ridge National Laboratory

    October 9, 2018
    Sara Shoemaker, Communications
    shoemakerms@ornl.gov
    865.576.9219

    A novel technique that nudges single atoms to switch places within an atomically thin material could bring scientists another step closer to realizing theoretical physicist Richard Feynman’s vision of building tiny machines from the atom up.

    A significant push to develop materials that harness the quantum nature of atoms is driving the need for methods to build atomically precise electronics and sensors. Fabricating nanoscale devices atom by atom requires delicacy and precision, which has been demonstrated by a microscopy team at the Department of Energy’s Oak Ridge National Laboratory.

    They used a scanning transmission electron microscope, or STEM, at the lab’s Center for Nanophase Materials Sciences to introduce silicon atoms into a single-atom-thick sheet of graphene. As the electron beam scans across the material, its energy slightly disrupts the graphene’s molecular structure and creates room for a nearby silicon atom to swap places with a carbon atom.

    Custom-designed scanning transmission electron microscope at Cornell University by David Muller/Cornell University

    “We observed an electron beam-assisted chemical reaction induced at a single atom and chemical bond level, and each step has been captured by the microscope, which is rare,” said ORNL’s Ondrej Dyck, co-author of a study published in the journal Small that details the STEM demonstration.

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    Ondrej Dyck of Oak Ridge National Laboratory used a scanning transmission electron microscope to move single atoms in a two-dimensional layer of graphene, an approach that could be used to build nanoscale devices from the atomic level up for quantum-based applications. Credit: Carlos Jones/Oak Ridge National Laboratory, U.S. Dept. of Energy.

    Using this process, the scientists were further able to bring two, three and four silicon atoms together to build clusters and make them rotate within the graphene layer. Graphene is a two-dimensional, or 2D, layer of carbon atoms that exhibits unprecedented strength and high electrical conductivity. Dyck said he selected graphene for this work, because “it is robust against a 60-kilovolt electron beam.”

    “We can look at graphene for long periods of time without hurting the sample, compared with other 2D materials such as transition metal dichalcogenide monolayers, which tend to fall apart more easily under the electron beam,” he added.

    STEM has emerged in recent years as a viable tool for manipulating atoms in materials while preserving the sample’s stability.

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    With a STEM microscope, ORNL’s Ondrej Dyck brought two, three and four silicon atoms together to build clusters and make them rotate within a layer of graphene, a two-dimensional layer of carbon atoms that exhibits unprecedented strength and high electrical conductivity. Credit: Ondrej Dyck/Oak Ridge National Laboratory, U.S. Dept. of Energy.

    Dyck and ORNL colleagues Sergei Kalinin, Albina Borisevich and Stephen Jesse are among few scientists learning to control the movement of single atoms in 2D materials using the STEM. Their work supports an ORNL-led initiative coined The Atomic Forge, which encourages the microscopy community to reimagine STEM as a method to build materials from scratch.

    The fields of nanoscience and nanotechnology have experienced explosive growth in recent years. One of the earlier steps toward Feynman’s idea of building tiny machines atom by atom—a follow-on from his original theory of atomic manipulation first presented during his famous 1959 lecture—was seeded by the work of IBM fellow Donald Eigler. He had shown the manipulation of atoms using a scanning tunneling microscope.

    “For decades, Eigler’s method was the only technology to manipulate atoms one by one. Now, we have demonstrated a second approach with an electron beam in the STEM,” said Kalinin, director of the ORNL Institute for Functional Imaging of Materials. He and Jesse initiated research with the electron beam about four years ago.

    Successfully moving atoms in the STEM could be a crucial step toward fabricating quantum devices one atom at a time. The scientists will next try introducing other atoms such as phosphorus into the graphene structure.

    “Phosphorus has potential because it contains one extra electron compared to carbon,” Dyck said. “This would be ideal for building a quantum bit, or qubit, which is the basis for quantum-based devices.”

    Their goal is to eventually build a device prototype in the STEM.

    Dyck cautioned that while building a qubit from phosphorus-doped graphene is on the horizon, how the material would behave at ambient temperatures—outside of the STEM or a cryogenic environment—remains unknown.

    “We have found that exposing the silicon-doped graphene to the outside world does impact the structures,” he said.

    They will continue to experiment with ways to keep the material stable in non-laboratory environments, which is important to the future success of STEM-built atomically precise structures.

    “By controlling matter at the atomic scale, we are going to bring the power and mystery of quantum physics to real-world devices,” Jesse said.

    Co-authors of the paper titled, Building Structures Atom by Atom via Electron Beam Manipulation
    are Ondrej Dyck, Sergei V. Kalinin and Stephen Jesse of ORNL; Songkil Kim of Pusan National University in South Korea; Elisa Jimenez-Izal of the University of California and UPV/EHU and DIPC in Spain; and Anastassia N. Alexandrova of UPV/EHU and DIPC in Spain and the California NanoSystems Institute.

    The research was funded by ORNL’s Laboratory-Directed Research and Development program. Microscopy experiments were performed at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 2:32 pm on October 5, 2018 Permalink | Reply
    Tags: , DOE Ofice of HIgh Energy Physics, ORNL, ORNL researchers advance quantum computing science through six DOE awards, ,   

    From Oak Ridge National Laboratory: “ORNL researchers advance quantum computing, science through six DOE awards” 

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    From Oak Ridge National Laboratory

    October 3, 2018
    Scott Jones, Communications
    jonesg@ornl.gov
    865.241.6491

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    Oak Ridge National Laboratory will be working on new projects aimed at accelerating quantum information science. Credit: Andy Sproles/Oak Ridge National Laboratory, U.S. Dept. of Energy.

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    ORNL researchers will leverage various microscopy platforms for quantum computing projects. Credit: Genevieve Martin/Oak Ridge National Laboratory, U.S. Dept. of Energy.

    The Department of Energy’s Oak Ridge National Laboratory is the recipient of six awards from DOE’s Office of Science aimed at accelerating quantum information science (QIS), a burgeoning field of research increasingly seen as vital to scientific innovation and national security.

    The awards, which were made in conjunction with the White House Summit on Advancing American Leadership in QIS, will leverage and strengthen ORNL’s established programs in quantum information processing and quantum computing.

    The application of quantum mechanics to computing and the processing of information has enormous potential for innovation across the scientific spectrum. Quantum technologies use units known as qubits to greatly increase the threshold at which information can be transmitted and processed. Whereas traditional “bits” have a value of either 0 or 1, qubits are encoded with values of both 0 and 1, or any combination thereof, at the same time, allowing for a vast number of possibilities for storing data.

    While in its infancy, the technology is being harnessed to develop computers that, when mature, will be exponentially more powerful than today’s leading systems. Beyond computing, however, quantum information science shows great promise to advance a vast array of research domains, from encryption to artificial intelligence to cosmology.

    The ORNL awards represent three Office of Science programs.

    “Software Stack and Algorithms for Automating Quantum-Classical Computing,” a new project supported by the Office of Advanced Scientific Computing Research, will develop methods for programming quantum computers. Led by ORNL’s Pavel Lougovski, the team of researchers from ORNL, Johns Hopkins University Applied Physics Lab, University of Southern California, University of Maryland, Georgetown University, and Microsoft, will tackle translating scientific applications into functional quantum programs that return accurate results when executed on real-world faulty quantum hardware. The team will develop an open-source algorithm and software stack that will automate the process of designing, executing, and analyzing the results of quantum algorithms, thus enabling new discovery across many scientific domains with an emphasis on applications in quantum field theory, nuclear physics, condensed matter, and quantum machine learning.

    ORNL’s Christopher M. Rouleau will lead the “Thin Film Platform for Rapid Prototyping Novel Materials with Entangled States for Quantum Information Science” project, funded by Basic Energy Sciences. The project aims to establish an agile AI-guided synthesis platform coupling reactive pulsed laser deposition with quick decision-making diagnostics to enable the rapid exploration of a wide spectrum of candidate thin-film materials for QIS; understand the dynamics of photonic states by combining a novel cathodoluminescence scanning electron microscopy platform with ultrafast laser spectroscopy; and enable understanding of entangled spin states for topological quantum computing by developing a novel scanning tunneling microscopy platform.

    ORNL’s Stephen Jesse will lead the “Understanding and Controlling Entangled and Correlated Quantum States in Confined Solid-State Systems Created via Atomic Scale Manipulation,” a new project supported by Basic Energy Sciences that includes collaborators from Harvard and MIT. The goal of the project is to use advanced electron microscopes to engineer novel materials on an atom-by-atom basis for use in QIS. These microscopes, along with other powerful instrumentation, will also be used to assess emerging quantum properties in-situ to aid the assembly process. Collaborators from Harvard will provide theoretical and computational effort to design quantum properties on demand using ORNL’s high-performance computing resources.

    ORNL is also partnering with Pacific Northwest National Laboratory, Berkeley Laboratory, and the University of Michigan on a project funded by the Office of Basic Energy Sciences titled “Embedding Quantum Computing into Many-Body Frameworks for Strongly-Correlated Molecular and Materials Systems.” The research team will develop methods for solving problems in computational chemistry for highly correlated electronic states. ORNL’s contribution, led by Travis Humble, will support this collaboration by translating applications of computational chemistry into the language needed for running on quantum computers and testing these ideas on experimental hardware.

    ORNL will support multiple projects awarded by the Office of High Energy Physics to develop methods for detecting high-energy particles using quantum information science. They include:

    “Quantum-Enhanced Detection of Dark Matter and Neutrinos,” in collaboration with the University of Wisconsin, Tufts, and San Diego State University. This project will use quantum simulation to calculate detector responses to dark matter particles and neutrinos. A new simulation technique under development will require extensive work in error mitigation strategies to correctly evaluate scattering cross sections and other physical quantities. ORNL’s effort, led by Raphael Pooser, will help develop these simulation techniques and error mitigation strategies for the new quantum simulator device, thus ensuring successful detector calculations.

    “Particle Track Pattern Recognition via Content Addressable Memory and Adiabatic Quantum Optimization: OLYMPUS Experiment Revisited,” a collaboration with John Hopkins Applied Physics Laboratory aimed at identifying rare events found in the data generated by experiments at particle colliders. ORNL principal investigator Travis Humble will apply new ideas for data analysis using experimental quantum computers that target faster response times and greater memory capacity for tracking signatures of high-energy particles.

    “HEP ML and Optimization Go Quantum,” in collaboration with Fermi National Accelerator Laboratory and Lockheed Martin Corporation, which will investigate how quantum machine learning methods may be applied to solving key challenges in optimization and data analysis. Advances in training machine learning networks using quantum computer promise greater accuracy and faster response times for data analysis. ORNL principal investigators Travis Humble and Alex McCaskey will help to develop these new methods for quantum machine learning for existing quantum computers by using the XACC programming tools, which offer a flexible framework by which to integrate quantum computing into scientific software.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 12:50 pm on September 14, 2018 Permalink | Reply
    Tags: , , , ORNL, Synthesis studies transform waste sugar for sustainable energy storage applications   

    From Oak Ridge National Laboratory: “Synthesis studies transform waste sugar for sustainable energy storage applications” 

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    From Oak Ridge National Laboratory

    September 6, 2018
    Scott Jones, Communications
    jonesg@ornl.gov
    865.241.6491

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    A molecular dynamics simulation depicts solid (black) and hollow (multicolored) carbon spheres derived from the waste sugar streams of biorefineries. The properties of the hollow spheres are ideal for developing energy storage devices called supercapacitors. Credit: Monojoy Goswami/ORNL

    Biorefinery facilities are critical to fueling the economy—converting wood chips, grass clippings, and other biological materials into fuels, heat, power, and chemicals.

    A research team at the US Department of Energy’s (DOE’s) Oak Ridge National Laboratory has now discovered a way to create functional materials from the impure waste sugars produced in the biorefining processes.

    Using hydrothermal carbonization, a synthesis technique that converts biomass into carbon under high temperature and pressure conditions, the team transformed waste sugar into spherical carbon materials. These carbon spheres could be used to form improved supercapacitors, which are energy storage devices that help power technologies including smartphones, hybrid vehicles, and security alarm systems. The team’s results are published in Scientific Reports, a Nature research journal.

    “The significant finding is that we found a way to take sugar from plants and other organic matter and use it to make different structures,” said Amit Naskar, a senior researcher in ORNL’s Materials Science and Technology Division. “Knowing the physics behind how those structures form can help us improve components of energy storage.”

    By modifying the synthesis process, the researchers created two varieties of the novel carbon spheres. Combining sugar and water under pressure resulted in solid spheres, whereas replacing water with an emulsion substance (a liquid that uses chemicals to combine oil and water) typically produced hollow spheres instead.

    “Just by substituting water for this other liquid, we can control the shape of the carbon, which could have huge implications for supercapacitor performance,” said Hoi Chun Ho, a PhD candidate working with Naskar at the Bredesen Center for Interdisciplinary Research and Graduate Education, a joint venture of ORNL and the University of Tennessee, Knoxville. The team also discovered that altering the duration of synthesis directly affected the size and shape of the spheres.

    To further explore the discrepancies between solid and hollow carbon structures, the team ran synthesis simulations on the Cray XK7 Titan supercomputer at the Oak Ridge Leadership Computing Facility (OLCF), a DOE Office of Science User Facility located at ORNL.

    ORNL Cray Titan XK7 Supercomputer

    They also used transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS) tools at the Center for Nanophase Materials Sciences (CNMS), another DOE Office of Science User Facility, to characterize the capabilities and structure of the carbon samples.

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    From left, Andrew Lupini and Juan Carlos Idrobo use ORNL’s new monochromated, aberration-corrected scanning transmission electron microscope, a Nion HERMES to take the temperatures of materials at the nanoscale. Image credit: Oak Ridge National Laboratory, U.S. Dept. of Energy; photographer Jason Richards

    “We wanted to determine what kind of surface area is good for energy storage applications, and we learned that the hollow spheres are more suitable,” said ORNL researcher Monojoy Goswami of CNMS and the Computer Science and Engineering Division. “Without these simulations and resources, we wouldn’t have been able to reach this fundamental understanding.”

    With this data the team tested a supercapacitor with electrodes made from hollow carbon spheres, which retained about 90 percent capacitance—the ability to store an electric charge—after 5,000 charge cycles. Although supercapacitors cannot store as much energy as batteries can store, they have many advantages over batteries, such as faster charging and exceptionally long lifetimes. Some technologies contain both batteries to provide everyday energy and supercapacitors to provide additional support during peak power demands.

    “Batteries often support smartphones and other electronic devices alone, but supercapacitors can be useful for many high-power applications,” Ho said. “For example, if a vehicle is driving up a steep hill with many passengers, the extra strain may cause the supercapacitor to kick in.”

    The pathway from waste sugar to hollow carbon spheres to supercapacitors demonstrates new potential for previously untapped byproducts from biorefineries. The researchers are planning projects to find and test other applications for carbon materials derived from waste sugar such as reinforcing polymer composites with carbon fibers.

    “Carbon can serve many useful purposes in addition to improving supercapacitors,” Ho said. “There is more work to be done to fully understand the structural evolution of carbon materials.”

    Making use of waste streams could also help scientists pursue forms of sustainable energy on a broader scale. According to the ORNL team, biorefineries can produce beneficial combinations of renewable energy and chemicals but are not yet profitable enough to compete with traditional energy sources. However, the researchers anticipate that developing useful materials from waste could help improve efficiency and reduce costs, making outputs from these facilities viable alternatives to oil and other fossil fuels.

    “Our goal is to use waste energy for green applications,” Goswami said. “That’s good for the environment, for the biorefinery industry, and for commerce.”

    Coauthors with Goswami, Ho, and Naskar are CNMS researchers Jihua Chen, who collected TEM data, and Jong Keum, who collected SAXS data. The research was supported by the Laboratory Directed Research and Development Program at ORNL with additional support from the DOE Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 10:49 am on August 8, 2018 Permalink | Reply
    Tags: ALCC Program Awards 14 Projects a Combined 729.5 Million Core Hours at the OLCF, , , OLCF-Oak Ridge Leadership Computing Facility, ORNL,   

    From Oak Ridge Leadership Computing Facility: “ALCC Program Awards 14 Projects a Combined 729.5 Million Core Hours at the OLCF” 

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    Oak Ridge National Laboratory

    From Oak Ridge Leadership Computing Facility

    Research teams receive computing time on the Titan supercomputer.

    Every year, the US Department of Energy’s (DOE’s) Office of Advanced Scientific Computing Research (ASCR) provides scientists with time on world-class computational resources across the country through the ASCR Leadership Computing Challenge (ALCC). The ALCC program grants 1-year awards to energy-related research efforts with an emphasis on high-risk, high-reward simulations in line with DOE’s mission.

    The ALCC program distributes time among multiple DOE Office of Science User Facilities, allocating up to 30 percent of the HPC resources at the Oak Ridge Leadership Computing Facility (OLCF) at DOE’s Oak Ridge National Laboratory (ORNL) and Argonne National Laboratory’s Argonne Leadership Computing Facility (ALCF), as well as up to 10 percent at the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

    ASCR manages all three user facilities, which each contain powerful supercomputers. Previous ALCC project recipients have leveraged these high-performance computing (HPC) systems to advance scientific and technological research in fields such as nuclear physics, energy efficiency, and materials science.

    In 2018, 14 projects have earned a combined 729.5 million core hours on Titan, the OLCF’s 27-petaflop supercomputer, to continue that tradition of innovation and discovery. Using Titan, teams of scientists will conduct experiments, collect data, and analyze results in support of various research topics, from studying biological processes in microbial ecosystems to developing new cosmological simulations for studying the history of the universe.

    Projects given time at the OLCF this year, which received awards ranging from 5 million to 100 million processor hours, are listed below. Some projects have additional computing time at the ALCF and/or NERSC.

    Brian Wirth from ORNL and the University of Tennessee received 60 million core hours on Titan for “Modeling Fusion Plasma Facing Components.”
    Todd Simons from Rolls-Royce Corporation received 10 million core hours on Titan for “Increasing the Scale of Implicit Finite Element Analyses.”
    Robert Edwards from Jefferson Lab received 96 million core hours on Titan for “The Real World of Real Glue.”
    Eric Lancon from Brookhaven National Laboratory received 80 million core hours on Titan for “Scaling LHC Proton–Proton Collision Simulations in the ATLAS Detector.”
    Robert Voigt from Leidos Inc. received 78.5 million core hours on Titan for “Demonstration of the Scalability of Programming Environments by Simulating Multi-Scale Applications.”
    Robert Patton from ORNL received 25 million core hours on Titan for “Advances in Machine Learning to Improve Scientific Discovery.”
    P. Straatsma from ORNL received 30 million core hours on Titan for “Portable Application Development for Next-Generation Supercomputer Architectures.”
    Katrin Heitmann from Argonne National Laboratory received 40 million core hours on Titan for “Emulating the Universe.”
    Chongle Pan from ORNL received 50 million core hours on Titan for “Petascale Analytics of Big Proteogenomics Data on Key Microbial Communities.”
    Peter Nugent from Lawrence Berkeley National Laboratory received 100 million core hours on Titan for “HPC4EnergyInnovation ALCC End-Station.”
    Mark Petersen from Los Alamos National Laboratory received 5 million core hours on Titan for “Investigating the Impact of Improved Southern Ocean Processes in Antarctic-Focused Global Climate Simulations.”
    Gary Grest from Sandia National Laboratories received 8 million core hours on Titan for “Large-Scale Numerical Simulations of Polymer Nanocomposites.”
    Swagato Mukherjee from Brookhaven National Laboratory received 85 million core hours on Titan for “Phase Boundary of Baryon-Rich QCD Matter.”
    Ronald Grover from General Motors received 12 million core hours on Titan for “Steady-State Engine Calibration in CFD Using a GPU-Based Chemistry Solver, Conjugate Heat Transfer, and Large Eddy Simulation (LES).”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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    The Oak Ridge Leadership Computing Facility (OLCF) was established at Oak Ridge National Laboratory in 2004 with the mission of accelerating scientific discovery and engineering progress by providing outstanding computing and data management resources to high-priority research and development projects.

    ORNL’s supercomputing program has grown from humble beginnings to deliver some of the most powerful systems in the world. On the way, it has helped researchers deliver practical breakthroughs and new scientific knowledge in climate, materials, nuclear science, and a wide range of other disciplines.

    The OLCF delivered on that original promise in 2008, when its Cray XT “Jaguar” system ran the first scientific applications to exceed 1,000 trillion calculations a second (1 petaflop). Since then, the OLCF has continued to expand the limits of computing power, unveiling Titan in 2013, which is capable of 27 petaflops.


    ORNL Cray XK7 Titan Supercomputer

    Titan is one of the first hybrid architecture systems—a combination of graphics processing units (GPUs), and the more conventional central processing units (CPUs) that have served as number crunchers in computers for decades. The parallel structure of GPUs makes them uniquely suited to process an enormous number of simple computations quickly, while CPUs are capable of tackling more sophisticated computational algorithms. The complimentary combination of CPUs and GPUs allow Titan to reach its peak performance.

    The OLCF gives the world’s most advanced computational researchers an opportunity to tackle problems that would be unthinkable on other systems. The facility welcomes investigators from universities, government agencies, and industry who are prepared to perform breakthrough research in climate, materials, alternative energy sources and energy storage, chemistry, nuclear physics, astrophysics, quantum mechanics, and the gamut of scientific inquiry. Because it is a unique resource, the OLCF focuses on the most ambitious research projects—projects that provide important new knowledge or enable important new technologies.

     
  • richardmitnick 8:02 pm on August 7, 2018 Permalink | Reply
    Tags: , Lauren Garrison, ORNL,   

    From Oak Ridge National Laboratory: Women in STEM: “Lauren Garrison: Testing materials for the future of fusion” 

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    From Oak Ridge National Laboratory

    August 7, 2018
    Sean Simoneau
    Communications
    simoneausm@ornl.gov
    865.241.0709


    Lauren Garrison

    The materials inside a fusion reactor must withstand one of the most extreme environments in science, with temperatures in the thousands of degrees Celsius and a constant bombardment of neutron radiation and deuterium and tritium, isotopes of hydrogen, from the volatile plasma at the heart of the device.

    Conventional materials cannot endure such punishing conditions, requiring tougher novel materials to be researched and designed before fusion reactors can move from basic science to potential future energy sources. One of the fusion materials researchers looking to find a possible candidate is Lauren Garrison, a Weinberg Fellow in the Nuclear Materials Science and Technology Group at the Department of Energy’s Oak Ridge National Laboratory.

    “I’m drawn to plasma facing materials because it is such a challenging environment, so unique and complex, trying to understand how we can have a material that can withstand all of these very difficult conditions,” Garrison said.

    Working with plasma-facing materials is especially tricky, as the environment inside a fusion reactor is like no place on Earth, so the long, arduous process of testing new materials can sometimes feel like assembling a puzzle with no edge pieces to provide a helpful framework.

    “Many of the structural and cooling components have some comparable materials that would be used in a fission reactor, so there is some sort of jumping-off point,” Garrison said. “But the plasma-facing region, which is extremely hot and fusing on one side and connected to structural materials on the other side, has nothing comparable in fission, so it is very specific to this application.”

    Garrison first studied nuclear engineering during her time as an undergrad at the University of Illinois and had several diverse research internship experiences before finding nuclear materials, which she found distinctly interesting and wished to pursue as a career.

    She interned at the university’s Center for Plasma-Materials Interaction, researching plasma processing and plasma modification of surfaces. It was the first research area that caught her attention and gave her experience with lab testing that she hadn’t previously seen in her other classes.

    She then interned at a chemistry lab at the National Polytechnic Institute of Lorraine in Nancy, France, which provided an incredible opportunity to branch out into other subjects and gain a perspective on science culture in another country.

    “As an engineering or science student, having internship experiences is crucial for both getting the hands-on work and getting a sense for the field, for the actual work environment and for different companies or labs,” Garrison said.

    She worked for a short time in the Cryogenic Dark Matter Search research group at Fermi National Accelerator Laboratory before being selected for the DOE Office of Science graduate fellowship program, where she first got to visit ORNL and learn how it supported many nuclear materials projects, especially in fusion materials, that were relevant to her interests.

    “No other national lab had the same range of capabilities as ORNL, matched with these amazing materials analysis techniques,” Garrison said. “Whereas smaller labs or universities might be experts in one specific technique, what we have here is the combined benefit of expert scientists in many subareas and the tools to perform all the tests together and compare everything.”

    Garrison had found a place that aligned with her interests and would allow her to push the boundaries of her knowledge. ORNL, as a leader in the field of neutron irradiated materials, enabled her to collaborate with other research groups from around the world to test new materials and processes on a wider scale than was possible at other facilities.

    Garrison is currently collaborating with Japanese researchers on Project PHENIX, an experiment designed to evaluate tungsten and tungsten-based materials for possible use in future fusion reactors.

    The team built a specially instrumented capsule with four different temperature zones to hold more than 1,100 material samples for irradiation in the High Flux Isotope Reactor, a DOE Office of Science User Facility.

    ORNL High Flux Isotope Reactor

    After exposing the capsule to several fuel cycles in HFIR and a cooldown period in a hot cell, Garrison and the project team are now examining the materials to gauge the effects of high heat flux and neutron damage on their microstructures and physical properties.

    The goal of her work is to use the results of these varied tests and create a more well-rounded database of potential fusion materials, connect new information together and fill in the knowledge gaps in the field.

    “At this point, we’re not going to find a magic material that’s perfect in every different condition it needs to withstand, so we are going to have to make a compromise or understand where the weaknesses are,” Garrison said. “The only way we can move towards building something successful is with the broad testing of materials on many different axes to be able to compare them to each other.”

    Garrison would love to see a working fusion reactor in her lifetime and hopes that her work will help contribute to its creation. For now, though, fusion research is still based in basic science, which allows her to pursue questions without specific constraints or a final product in mind.

    “It’s very rewarding for me to be able to think creatively and have some freedom to investigate different avenues,” she said.

    As time goes on and more of the big questions in plasma science are answered, Garrison hopes the public will come to recognize the potential of fusion energy and how the current investments will pay off in the future.

    “I love the big picture of fusion and I think it is easy to get people excited about how great it is for energy,” she said. “Every time I get to talk about it, I get inspired and remember why I’m writing these long reports and doing all this work, because it has really cool applications that it is going towards.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 3:41 pm on May 18, 2018 Permalink | Reply
    Tags: , ORNL, , , PROSPECT-Precision Reactor Oscillation and Spectrum Experiment,   

    From Yale University: “PROSPECTing for antineutrinos” 

    Yale University bloc

    From Yale University

    ORNL

    May 18, 2018
    Jim Shelton
    james.shelton@yale.edu
    203-361-8332

    1
    Assembly of the PROSPECT neutrino detector. (Image credit: PROSPECT collaboration/Mara Lavitt)

    The Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) has completed the installation of a novel antineutrino detector that will probe the possible existence of a new form of matter.

    PROSPECT, located at the High Flux Isotope Reactor (HFIR) at the Department of Energy’s Oak Ridge National Laboratory (ORNL), has begun taking data to study electron antineutrinos that are emitted from nuclear decays in the reactor to search for so-called sterile neutrinos and to learn about the underlying nuclear reactions that power fission reactors.

    Antineutrinos are elusive, elementary particles produced in nuclear beta decay. The antineutrino is an antimatter particle, the counterpart to the neutrino.

    “Neutrinos are among the most abundant particles in the universe,” said Yale University physicist Karsten Heeger, principal investigator and co-spokesperson for PROSPECT. “The discovery of neutrino oscillation has opened a window to physics beyond the Standard Model of Physics. The study of antineutrinos with PROSPECT allows us to search for a previously unobserved particle, the so-called sterile neutrino, while probing the nuclear processes inside a reactor.”

    Over the past few years several neutrino experiments at nuclear reactors have detected fewer antineutrinos than scientists had predicted, and the energy of the neutrinos did not match expectations. This, in combination with earlier anomalous results, led to the hypothesis that a fraction of electron antineutrinos may transform into sterile neutrinos that would have remained undetected in previous experiments.

    This hypothesized transformation would take place through a quantum mechanical process called neutrino oscillation. The first observation of neutrino oscillation amongst known types of neutrinos from the sun and the atmosphere led to the 2015 Nobel Prize in physics.

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    (Image credit: PROSPECT collaboration/Mara Lavitt)

    The installation of PROSPECT follows four years of intensive research and development by a collaboration of more than 60 participants from 10 universities and four national laboratories.

    “The development of PROSPECT is based on years of research in the detection of reactor antineutrinos with surface-based detectors, an extremely challenging task because of high backgrounds,” said PROSPECT co-spokesperson Pieter Mumm, a scientist at the National Institute of Standards and Technology (NIST).

    The experiment uses a novel antineutrino detector system based on a segmented liquid scintillator detector technology. The combination of segmentation and a unique, lithium-doped liquid scintillator formulation allows PROSPECT to identify particle types and interaction points. These design features, along with extensive, tailored shielding, will enable PROSPECT to make a precise measurement of neutrinos in the high-background environment of a nuclear reactor.

    PROSPECT’s detector technology also may have applications in the monitoring of nuclear reactors for non-proliferation purposes and the measurement of neutrons from nuclear processes.

    “The successful operation of PROSPECT will allow us to gain insight into one of the fundamental puzzles in neutrino physics and develop a better understanding of reactor fuel, while also providing a new tool for nuclear safeguards,” said co-spokesperson Nathaniel Bowden, a scientist at Lawrence Livermore National Laboratory and an expert in nuclear non-proliferation technology.

    After two years of construction and final assembly at the Yale Wright Laboratory, the PROSPECT detector was transported to HFIR in early 2018.

    “The development and construction of PROSPECT has been a significant team effort, making use of the complementary expertise at U.S. national laboratories and universities,” said Alfredo Galindo-Uribarri, leader of the Neutrino and Advanced Detectors group in ORNL’s Physics Division.

    PROSPECT is the latest in a series of fundamental science experiments located at HFIR. “We are excited to work with PROSPECT scientists to support their research,” said Chris Bryan, who manages experiments at HFIR for ORNL’s Research Reactors Division.

    The experiment is supported by the U.S. Department of Energy Office of Science, the Heising-Simons Foundation, and the National Science Foundation. Additional support comes from Yale University, the Illinois Institute of Technology, and the Lawrence Livermore National Laboratory LDRD program. The collaboration also benefits from the support and hospitality of the High Flux Isotope Reactor, a DOE Office of Science User Facility, and Oak Ridge National Laboratory, managed by UT-Battelle for the U.S. Department of Energy.

    See the full article here .

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    Yale University Campus

    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 5:42 pm on April 11, 2018 Permalink | Reply
    Tags: , , , , ORNL, ,   

    From Symmetry: “Right on target” 

    Symmetry Mag
    Symmetry

    04/11/18
    Sarah Lawhun

    1
    Patrick Hurh

    These hardy physics components live at the center of particle production.

    For some, a target is part of a game of darts. For others, it’s a retail chain. In particle physics, it’s the site of an intense, complex environment that plays a crucial role in generating the universe’s smallest components for scientists to study.

    The target is an unsung player in particle physics experiments, often taking a back seat to scene-stealing light-speed particle beams and giant particle detectors. Yet many experiments wouldn’t exist without a target. And, make no mistake, a target that holds its own is a valuable player.

    Scientists and engineers at Fermilab [FNAL] are currently investigating targets for the study of neutrinos—mysterious particles that could hold the key to the universe’s evolution.

    Intense interactions

    The typical particle physics experiment is set up in one of two ways. In the first, two energetic particle beams collide into each other, generating a shower of other particles for scientists to study.

    In the second, the particle beam strikes a stationary, solid material—the target. In this fixed-target setup, the powerful meeting produces the particle shower.

    As the crash pad for intense beams, a target requires a hardy constitution. It has to withstand repeated onslaughts of high-power beams and hold up under hot temperatures.

    You might think that, as stalwart players in the play of particle production, targets would look like a fortress wall (or maybe you imagined dartboard). But targets take different shapes—long and thin, bulky and wide. They’re also made of different materials, depending on the kind of particle one wants to make. They can be made of metal, water or even specially designed nanofibers.

    In a fixed-target experiment, the beam—say, a proton beam—races toward the target, striking it. Protons in the beam interact with the target material’s nuclei, and the resulting particles shoot away from the target in all directions. Magnets then funnel and corral some of these newly born particles to a detector, where scientists measure their fundamental properties.

    The particle birthplace

    The particles that emerge from the beam-target interaction depend in large part on the target material. Consider Fermilab neutrino experiments.

    In these experiments, after the protons strike the target, some of the particles in the subsequent particle shower decay—or transform—into neutrinos.

    The target has to be made of just the right stuff.

    “Targets are crucial for particle physics research,” says Fermilab scientist Bob Zwaska. “They allow us to create all of these new particles, such as neutrinos, that we want to study.”

    Graphite is a goldilocks material for neutrino targets. If kept at the right temperature while in the proton beam, the graphite generates particles of just the right energy to be able to decay into neutrinos.

    For neutron targets, such as that at the Spallation Neutron Source at Oak Ridge National Laboratory [ORNL], heavier metals such as mercury are used instead.

    ORNL Spallation Neutron Source


    ORNL Spallation Neutron Source

    Maximum interaction is the goal of a target’s design. The target for Fermilab’s NOvA neutrino experiment, for example, is a straight row—about the length of your leg—of graphite fins that resemble tall dominoes.

    FNAL NOvA Near Detector


    FNAL/NOvA experiment map

    The proton beam barrels down its axis, and every encounter with a fin produces an interaction. The thin shape of the target ensures that few of the particles shooting off after collision are reabsorbed back into the target.

    Robust targets

    “As long as the scientists have the particles they need to study, they’re happy. But down the line, sometimes the targets become damaged,” says Fermilab engineer Patrick Hurh. In such cases, engineers have to turn down—or occasionally turn off—the beam power. “If the beam isn’t at full capacity or is turned off, we’re not producing as many particles as we can for science.”

    The more protons that are packed into the beam, the more interactions they have with the target, and the more particles that are produced for research. So targets need to be in tip-top shape as much as possible. This usually means replacing targets as they wear down, but engineers are always exploring ways of improving target resistance, whether it’s through design or material.

    Consider what targets are up against. It isn’t only high-energy collisions—the kinds of interactions that produce particles for study—that targets endure.

    Lower-energy interactions can have long-term, negative impacts on a target, building up heat energy inside it. As the target material rises in temperature, it becomes more vulnerable to cracking. Expanding warm areas hammer against cool areas, creating waves of energy that destabilize its structure.

    Some of the collisions in a high-energy beam can also create lightweight elements such as hydrogen or helium. These gases build up over time, creating bubbles and making the target less resistant to damage.

    A proton from the beam can even knock off an entire atom, disrupting the target’s crystal structure and causing it to lose durability.

    Clearly, being a target is no picnic, so scientists and engineers are always improving targets to better roll with a punch.

    For example, graphite, used in Fermilab’s neutrino experiments, is resistant to thermal strain. And, since it is porous, built-up gases that might normally wedge themselves between atoms and disrupt their arrangement may instead migrate to open areas in the atomic structure. The graphite is able to remain stable and withstand the waves of energy from the proton beam.

    Engineers also find ways to maintain a constant target temperature. They design it so that it’s easy to keep cool, integrating additional cooling instruments into the target design. For example, external water tubes help cool the target for Fermilab’s NOvA neutrino experiment.

    Targets for intense neutrino beams

    At Fermilab, scientists and engineers are also testing new designs for what will be the lab’s most powerful proton beam—the beam for the laboratory’s flagship Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment, known as LBNF/DUNE.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


    FNAL DUNE Argon tank at SURF


    Surf-Dune/LBNF Caverns at Sanford



    SURF building in Lead SD USA

    LBNF/DUNE is scheduled to begin operation in the 2020s. The experiment requires an intense beam of high-energy neutrinos—the most intense in the world. Only the most powerful proton beam can give rise to the quantities of neutrinos LBNF/DUNE needs.

    Scientists are currently in the early testing stages for LBNF/DUNE targets, investigating materials that can withstand the high-power protons. Currently in the running are beryllium and graphite, which they’re stretching to their limits. Once they conclusively determine which material comes out on top, they’ll move to the design prototyping phase. So far, most of their tests are pointing to graphite as the best choice.

    Targets will continue to evolve and adapt. LBNF/DUNE provides just one example of next-generation targets.

    “Our research isn’t just guiding the design for LBNF/DUNE,” Hurh says. “It’s for the science itself. There will always be different and more powerful particle beams, and targets will evolve to meet the challenge.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:02 pm on February 16, 2018 Permalink | Reply
    Tags: , Improving quantum information processing, ORNL   

    From ORNL: “Researchers demonstrate promising method for improving quantum information processing” 

    i1

    Oak Ridge National Laboratory

    February 16, 2018
    Scott Jones, Communications
    jonesg@ornl.gov
    865.241.6491

    1
    Joseph Lukens, Pavel Lougovski and Nicholas Peters (from left), researchers with ORNL’s Quantum Information Science Group, are examining methods for encoding photons with quantum information that are compatible with the existing telecommunications infrastructure and that incorporate off-the-shelf components. Credit: Genevieve Martin/Oak Ridge National Laboratory, U.S. Department of Energy.

    A team of researchers led by the Department of Energy’s Oak Ridge National Laboratory has demonstrated a new method for splitting light beams into their frequency modes. The scientists can then choose the frequencies they want to work with and encode photons with quantum information. Their work could spur advancements in quantum information processing and distributed quantum computing.

    The team’s findings were published in Physical Review Letters.

    The frequency of light determines its color. When the frequencies are separated, as in a rainbow, each color photon can be encoded with quantum information, delivered in units known as qubits. Qubits are analogous to but different from classical bits, which have a value of either 0 or 1, because qubits are encoded with values of both 0 and 1 at the same time.

    The researchers liken quantum information processing to stepping into a hallway and being able to go both ways, whereas in classical computing just one path is possible.

    The team’s novel approach—featuring the first demonstration of a frequency tritter, an instrument that splits light into three frequencies—returned experimental results that matched their predictions and showed that many quantum information processing operations can be run simultaneously without increasing error. The quantum system performed as expected under increasingly complex conditions without degrading the encoded information.

    “Under our experimental conditions, we got a factor 10 better than typical error rates,” said Nicholas Peters, Quantum Communications team lead for ORNL’s Quantum Information Science Group. “This establishes our method as a frontrunner for high-dimensional frequency-based quantum information processing.”

    Photons can carry quantum information in superpositions—where photons simultaneously have multiple bit values—and the presence of two quantum systems in superposition can lead to entanglement, a key resource in quantum computing.

    Entanglement boosts the number of calculations a quantum computer could run, and the team’s focus on creating more complex frequency states aims to make quantum simulations more powerful and efficient. The researchers’ method is also notable because it demonstrates the Hadamard gate, one of the elemental circuits required for universal quantum computing.

    “We were able to demonstrate extremely high-fidelity results right off the bat, which is very impressive for the optics approach,” said Pavel Lougovski, the project’s principal investigator. “We are carving out a subfield here at ORNL with our frequency-based encoding work.”

    The method leverages widely available telecommunications technology with off-the-shelf components while yielding high-fidelity results. Efforts to develop quantum repeaters, which extend the distance quantum information can be transmitted between physically separated computers, will benefit from this work.

    “The fact that our method is telecom network-compatible is a big advantage,” Lougovski said. “We could perform quantum operations on telecom networks if needed.”

    Peters added that their project demonstrates that unused fiber-optic bandwidth could be harnessed to reduce computational time by running operations in parallel.

    “Our work uses frequency’s main advantage—stability—to get very high fidelity and then do controlled frequency jumping when we want it,” said Wigner Fellow Joseph Lukens, who led the ORNL experiment. The researchers have experimentally shown that quantum systems can be transformed to yield desired outputs.

    The researchers suggest their method could be paired with existing beam-splitting technology, taking advantage of the strengths of both and bringing the scientific community closer to full use of frequency-based photonic quantum information processing.

    Peters, Lougovski and Lukens, all physicists with ORNL’s Quantum Information Science Group, collaborated with graduate student Hsuan-Hao Lu, professor Andrew Weiner, and colleagues at Purdue University. The team published the theory for their experiments in Optica in January 2017.

    This research is supported by ORNL’s Laboratory Directed Research and Development program and the National Science Foundation.

    See the full article here .

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 4:40 pm on January 2, 2018 Permalink | Reply
    Tags: , , , Mallory Ladd, Mallory Ladd began trekking to the Arctic even before her time at the Department of Energy's Oak Ridge National Laboratory, NGEE-Arctic program, ORNL, Soil chemistry,   

    From ORNL: Women in STEM- “Mallory Ladd: A molecular-scale Arctic expedition” 

    i1

    Oak Ridge National Laboratory

    1
    Mallory Ladd gathers field samples on the coastal plain of northern Alaska. Photo courtesy, Mallory Ladd.

    2
    Mallory Ladd is a Bredesen Center student working with the NGEE-Arctic program at ORNL, seeking a better understanding of how soil water chemistry affects the aboveground environment. Photo courtesy, Jason Richards

    January 2, 2018

    Stephanie G. Seay, Communications
    seaysg@ornl.gov
    865.576.9894

    Mallory Ladd began trekking to the Arctic, even before her time at the Department of Energy’s Oak Ridge National Laboratory, in search of a better understanding of what’s going on belowground and how it links to changes in the larger landscape.

    The University of Tennessee, Knoxville (UTK) Bredesen Center student last year finished her third trip to Alaska to collect field data for the Next Generation Ecosystem Experiments-Arctic (NGEE-Arctic) program, supported by the U.S. Department of Energy’s Office of Biological and Environmental Research. The program harnesses the expertise of more than 140 scientists from national labs and universities studying how permafrost thaw may affect regional and global climate systems.

    Ladd is using her capabilities in analytical chemistry and mass spectrometry to examine how soil water chemistry is changing in the Arctic because of warming and thawing conditions, in order to better inform earth science models. She has been exploring those changes since her undergraduate days researching Arctic soil nitrogen at the University of Toledo.

    “Chemists usually spend a lot of time in the lab,” Ladd said. “But with this type of research I’m encouraged to get out and collect samples in the field. I feel closer to the science questions that way; working from sample collection to data analysis, from start to finish, has been enlightening.”

    Her path to the Arctic began at Toledo as the result of a chance encounter with Professor Mike Weintraub, who had just received funding from the National Science Foundation (NSF) to examine seasonality in the Arctic. Ladd was a senior at the university at the time, watching a screening of the documentary Dirt! with a friend. “We were talking about how interesting the movie was, how important the nutrient profile and soil chemistry are to so many things, when Mike joined in the conversation and told us he was looking for a lab technician with a chemistry background to join his team,” said Ladd. She worked with Weintraub for two years, visiting the Arctic twice for sampling as she studied soil nitrogen availability and impacts on plant life.

    Advancing science with cutting-edge instruments

    The work greatly influenced where Ladd would go for her doctoral studies. She was attracted to the Bredesen Center for Interdisciplinary Research & Graduate Education for its close ties to the national lab and the NGEE-Arctic program led by ORNL Environmental Sciences Division Director Stan Wullschleger—as well as by the offer of a personalized Ph.D. program that allows her to pursue science and a parallel track in policy. She began her time with ORNL and UTK in 2013, and is currently pursuing a doctorate in energy science and engineering. She is also an NSF Graduate Research Fellow.

    Wullschleger and UTK adviser Robert Hettich, a scientist in the Mass Spectrometry/Laser Spectroscopy Group at ORNL, helped Ladd design a program around Arctic metabolomics. In this focus area, she studies small molecules in the soil—how they are transported and break down over time, and how soil chemistry changes as temperatures rise.

    “Much of the success with this research is owed to being at ORNL with all the cutting-edge technologies it offers. The mass spectrometry resources here have been integral to getting high-resolution measurements in a short amount of time,” Ladd said.

    Her work for NGEE-Arctic started out in Barrow, Alaska, a coastal plain environment that has interesting microtopography where the soil physically moves as it freezes and thaws, creating rifts and valleys in the landscape. This summer, NGEE-Arctic conducted sampling in Nome, a sub-Arctic region that has undergone more warming and has markedly different, abundant plant life compared with Barrow.

    “My work at ORNL has allowed me to connect my fundamental scientific questions with DOE deliverables,” Mallory said. “It’s a great time to advocate for science, and to make sure we have strong, motivated young scientists doing excellent work.”

    Supporting the next generation of scientists

    Ladd has been very active in supporting her peers. She maintains a blog, “Think Like a Postdoc,” that chronicles her work and dispenses advice to other students.

    She also founded a student group at UTK called Pipeline: Vols for Women in STEM. A part of the university’s Commission for Women, the group works to enhance the status and representation of women in the 50-plus science, technology, engineering, and math fields at UTK through events such as an annual research symposium, interdisciplinary mentoring, monthly lectures, community outreach, and professional and social networking events.

    “The name ‘Pipeline’ refers to the analogy often used to describe the phenomenon that young girls and women are shown to be just as interested and scoring just as high as boys and men in STEM areas in K-12 and as college undergrads. But after graduating we see a divergence in the gender balance where men start to dominate these fields, often referred to as the leaky pipeline,” she said. Research in the past decade has discarded the notion that those changes happen because women start having children or are not “cut out” for long hours, she added.

    “Instead, studies are showing that the culprit is unconscious, or implicit, biases at the systemic level that are discouraging women from pursuing these careers as compared to their white male counterparts. The numbers are even worse for women of color, and especially at the leadership level,” she said. The Pipeline group tracks statistics on gender distribution in STEM areas at the university and aims to reverse that trend.

    Ladd’s curiosity and questioning nature began early. “I always questioned everything, and my parents were a huge part of that. They always encouraged me to not be afraid of standing out and to challenge the status quo. Science has been an outlet for that tendency,” she said. “I like the phrase that science turns ‘I don’t know’ into ‘I don’t know yet.’”

    Ladd grew up playing volleyball, with siblings who played rugby and soccer—meaning a lot of time on the road with various teams. “Our parents always told us it was okay to play in the dirt,” she said. Today away from the lab, she continues to spend time outdoors, kayaking, biking, and rock climbing, adding, “I’m a huge advocate for grad students making time for outside interests.”

    See the full article here .

    Please help promote STEM in your local schools.

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 3:35 pm on December 28, 2017 Permalink | Reply
    Tags: Femtosecond X-ray lasers, Inelastic X-ray scattering, , , ORNL, , , ,   

    From Optics & Photonics: “X-Ray Studies Probe Water’s Elusive Properties” 

    Optics & Photonics

    28 December 2017
    Stewart Wills

    1
    Unlike most substances, liquid water is denser than its solid phase, ice. [Image: Stockholm University]

    In two different X-ray investigations, researchers have dug into some of the exotic properties of that most familiar of substances—water.

    In one study, researchers from Sweden, Japan and South Korea used a femtosecond X-ray laser to investigate the behavior of evaporatively supercooled liquid water, and to confirm the long-suspected view that water at low temperatures can exist in two different liquid phases (Science). In the other, a U.S.-Japanese team used high-resolution inelastic X-ray scattering to probe the dynamics of water molecules and how the liquid’s hydrogen bonds contribute to its unusual characteristics (Science Advances).

    Burst pipes and floating cubes

    Anyone who has confronted a burst water pipe on a frozen winter morning has firsthand knowledge of one of H20’s unusual characteristics. Whereas most substances increase in density as they go from a liquid to a solid state, water reaches its maximum density at 4°C, above its nominal freezing point of 0°C. That’s also the reason that the ice cubes float at the top of your water glass rather than sinking to the bottom.

    Grappling with this anomalous behavior, a research team at Boston University suggested around 25 years ago, based on computer simulations, that in a metastable, supercooled state, water might actually coexist in two liquid phases—a low-density liquid and a high-density liquid. Those two phases, the researchers proposed, merged into a single phase at a critical point in water phase diagram at around –44°C (analogous to the better-known critical point at a higher temperature between water’s liquid and gas phases).

    3
    Experiments using femtosecond X-ray free-electron lasers illuminated fluctuations between two different phases of liquid water—a high-density liquid (red) and a low-density liquid (blue)—as a function of temperature in the supercooled regime. [Image: Stockholm University]

    Actually getting liquid water to that frigid point has, however, seemed a bit of a pipe dream. While very pure liquid water can be rapidly supercooled to temperatures moderately below 0°C relatively easily, the proposed critical point lies far below that temperature range, in what researchers have dubbed a “no-man’s land” in which ice crystalizes much faster than the timescale of conventional lab measurements.

    Leveraging ultrafast lasers

    To move past that barrier, a research team led by Anders Nilsson of Stockholm University, Sweden, turned to the rapid timescales enabled by femtosecond X-ray free-electron lasers (XFELs). At XFEL facilities in Korea and Japan [un-named], the team sent a stream of tiny water droplets (approximately 14 microns in diameter) into a vacuum chamber, and fired the XFEL at the droplets at varying distances from the water-dispensing nozzle to obtain ultrafast X-ray scattering data.

    The tiny size of the droplets meant that as they traveled through the vacuum they rapidly evaporatively cooled—with the amount of cooling related to the time they spent in vacuum under a well-established formula. Thus, by taking X-ray measurements at varying distances from the nozzle, the researchers could examine the structural behavior of the liquid water at multiple temperatures in the deep-supercooling regime, near the hypothesized critical point. “We were able to X-ray unimaginably fast before the ice froze,” Nilsson said in a press release, “and could observe how it fluctuated” between the two hypothesized metastable phases of liquid water.

    The experiments allowed the team to flesh out the phase diagram of liquid water in a supercooled region previously thought to be inaccessible to experiment. And the researchers believe that the use of femtosecond XFELs to probe thermodynamic functions and structural changes at extreme states “can be generalized to many supercooled liquids.”

    Illuminating water’s dynamics

    4
    A team led by scientists at the U.S. Oak Ridge National Laboratory used inelastic X-ray scattering to visualize and quantify the movement of water molecules in space and time. [Image: Jason Richards/Oak Ridge National Laboratory, US Dept. of Energy]

    A second set of experiments, from researchers at the U.S. Oak Ridge National Laboratory, the University of Tennessee, and the SPring-8 synchrotron laboratory in Japan, looked at water’s dynamics at room temperature, using inelastic X-ray scattering (IXS).

    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    The researchers illuminated these dynamics through a series of experiments in which they trained radiation from the SPring-8 facility’s high-resolution IXS beamline, BL35XU, onto a 2-mm-thick sample of liquid water. Through multiple scattering measurements across a range of momentum and energy-transfer values, the team was able to build a detailed picture of the so-called Van Hove function, which describes the probability of interactions between a molecule and its nearest neighbors as a function of distance and time.

    The team found that water’s hydrogen bonds behave in a highly correlated fashion with respect to one another, which gives liquid water its high stability and explains its viscosity characteristics. And, in a press release, the researchers further speculated that the techniques used here could be extended to studying the dynamics and viscosity of a variety of other liquids. Some of those studies, they suggested, could prove useful in “the development of new types of semiconductor devices with liquid electrolyte insulating layers, better batteries and improved lubricants.”

    Here, the research team was interested in sussing out how water molecules interact in real time, and how the strongly directional hydrogen bonds of water molecules work together to determine properties such the liquid’s viscosity.

    See the full article here .

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    Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics. We welcome your submissions.

     
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