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  • richardmitnick 6:55 am on September 10, 2019 Permalink | Reply
    Tags: , , , Electrochemical conversion, SLAC National Accelerator Laboratory,   

    From SLAC National Accelerator Lab: “Plastics, fuels and chemical feedstocks from CO2? They’re working on it.” 

    From SLAC National Accelerator Lab

    September 9, 2019
    Glennda Chui

    1
    Researchers at Stanford and SLAC are working on ways to convert waste carbon dioxide (CO2) into chemical feedstocks and fuels, turning a potent greenhouse gas into valuable products. The process is called electrochemical conversion. When powered by renewable energy sources (far left), it could reduce levels of carbon dioxide in the air and store energy from these intermittent sources in a form that can be used any time. (Greg Stewart/SLAC National Accelerator Laboratory)

    One way to reduce the level of carbon dioxide in the atmosphere, which is now at its highest point in 800,000 years, would be to capture the potent greenhouse gas from the smokestacks of factories and power plants and use renewable energy to turn it into things we need, says Thomas Jaramillo.

    As director of SUNCAT Center for Interface Science and Catalysis, a joint institute of Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, he’s in a position to help make that happen.

    A major focus of SUNCAT research is finding ways to transform CO2 into chemicals, fuels, and other products, from methanol to plastics, detergents and synthetic natural gas. The production of these chemicals and materials from fossil fuel ingredients now accounts for 10% of global carbon emissions; the production of gasoline, diesel, and jet fuel accounts for much, much more.

    “We have already emitted too much CO2, and we’re on track to continue emitting it for years, since 80% of the energy consumed worldwide today comes from fossil fuels,” says Stephanie Nitopi, whose SUNCAT research is the basis of her newly acquired Stanford PhD.

    “You could capture CO2 from smokestacks and store it underground,” she says. “That’s one technology currently in play. An alternative is to use it as a feedstock to make fuels, plastics, and specialty chemicals, which shifts the financial paradigm. Waste CO2 emissions now become something you can recycle into valuable products, providing a new incentive to reduce the amount of CO2 released into the atmosphere. That’s a win-win.”

    We asked Nitopi, Jaramillo, SUNCAT staff scientist Christopher Hahn and postdoctoral researcher Lei Wang to tell us what they’re working on and why it matters.

    Q. First the basics: How do you convert CO2 into these other products?

    Tom: It’s essentially a form of artificial photosynthesis, which is why DOE’s Joint Center for Artificial Photosynthesis funds our work. Plants use solar energy to convert CO2 from the air into carbon in their tissues. Similarly, we want to develop technologies that use renewable energy, like solar or wind, to convert CO2 from industrial emissions into carbon-based products.

    Chris: One way to do this is called electrochemical CO2 reduction, where you bubble CO2 gas up through water and it reacts with the water on the surface of a copper-based electrode. The copper acts as a catalyst, bringing the chemical ingredients together in a way that encourages them to react. Put very simply, the initial reaction strips an oxygen atom from CO2 to form carbon monoxide, or CO, which is an important industrial chemical in its own right. Then other electrochemical reactions turn CO into important molecules such as alcohols, fuels and other things.

    Today this process requires a copper-based catalyst. It’s the only one known to do the job. But these reactions can produce numerous products, and separating out the one you want is costly, so we need to identify new catalysts that are able to guide the reaction toward making only the desired product.

    How so?

    Lei: When it comes to improving a catalyst’s performance, one of the key things we look at is how to make them more selective, so they generate just one product and nothing else. About 90 percent of fuel and chemical manufacturing depends on catalysts, and getting rid of unwanted byproducts is a big part of the cost.

    We also look at how to make catalysts more efficient by increasing their surface area, so there are a lot more places in a given volume of material where reactions can occur simultaneously. This increases the production rate.

    Recently we discovered something surprising [Nature Catalysis]: When we increased the surface area of a copper-based catalyst by forming it into a flaky “nanoflower” shape, it made the reaction both more efficient and more selective. In fact, it produced virtually no byproduct hydrogen gas that we could measure. So this could offer a way to tune reactions to make them more selective and cost-competitive.

    Stephanie: This was so surprising that we decided to revisit all the research we could find [Chem. Rev.] on catalyzing electrochemical CO2 conversion with copper, and the many ways people have tried to understand and fine-tune the process, using both theory and experiments, going back four decades. There’s been an explosion of research on this – about 60 papers had been published as of 2006, versus more than 430 out there today – and analyzing all the studies with our collaborators at the Technical University of Denmark took two years.

    We were trying to figure out what makes copper special, why it’s the only catalyst that can make some of these interesting products, and how we can make it even more efficient and selective – what techniques have actually pushed the needle forward? We also offered our perspectives on promising research directions.

    One of our conclusions confirms the results of the earlier study: The copper catalyst’s surface area can be used to improve both the selectivity and overall efficiency of reactions. So this is well worth considering as a chemical production strategy.

    Does this approach have other benefits?

    Tom: Absolutely. If we use clean, renewable energy, like wind or solar, to power the controlled conversion of waste CO2 to a wide range of other products, this could actually draw down levels of CO2 in the atmosphere, which we will need to do to stave off the worst effects of global climate change.

    Chris: And when we use renewable energy to convert CO2 to fuels, we’re storing the variable energy from those renewables in a form that can be used any time. In addition, with the right catalyst, these reactions could take place at close to room temperature, instead of the high temperatures and pressures often needed today, making them much more energy efficient.

    How close are we to making it happen?

    Tom: Chris and I explored this question in a recent Perspective article in Science, written with researchers from the University of Toronto and TOTAL American Services, which is an oil and gas exploration and production services firm.

    We concluded that renewable energy prices would have to fall below 4 cents per kilowatt hour, and systems would need to convert incoming electricity to chemical products with at least 60% efficiency, to make the approach economically competitive with today’s methods.

    Chris: This switch couldn’t happen all at once; the chemical industry is too big and complex for that. So one approach would be to start with making high-value, high-volume products like ethylene, which is used to make alcohols, polyester, antifreeze, plastics and synthetic rubber. It’s a $230 billion global market today. Switching from fossil fuels to CO2 as a starting ingredient for ethylene in a process powered by renewables could potentially save the equivalent of about 860 million metric tons of CO2 emissions per year.

    The same step-by-step approach applies to sources of CO2. Industry could initially use relatively pure CO2 emissions from cement plants, breweries or distilleries, for instance, and this would have the side benefit of decentralizing manufacturing. Every country could provide for itself, develop the technology it needs, and give its people a better quality of life.

    Tom: Once you enter certain markets and start scaling up the technology, you can attack other products that are tougher to make competitively today. What this paper concludes is that these new processes have a chance to change the world.

    See the full article here .


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    Please help promote STEM in your local schools.

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    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 8:23 am on September 6, 2019 Permalink | Reply
    Tags: , Rechargeable lithium metal batteries, SLAC National Accelerator Laboratory,   

    From Stanford University and SLAC: “New coating developed by Stanford researchers brings lithium metal battery closer to reality” 

    Stanford University Name
    From Stanford University

    August 26, 2019
    Mark Golden

    1
    A new coating could make lightweight lithium metal batteries safe and long lasting, a boon for development of next-generation electric vehicles. (Image credit: Shutterstock)

    Hope has been restored for the rechargeable lithium metal battery – a potential battery powerhouse relegated for decades to the laboratory by its short life expectancy and occasional fiery demise while its rechargeable sibling, the lithium-ion battery, now rakes in more than $30 billion a year.

    A team of researchers at Stanford University and SLAC National Accelerator Laboratory has invented a coating that overcomes some of the battery’s defects, described in a paper published Aug. 26 in Joule.

    In laboratory tests, the coating significantly extended the battery’s life. It also dealt with the combustion issue by greatly limiting the tiny needlelike structures – or dendrites – that pierce the separator between the battery’s positive and negative sides. In addition to ruining the battery, dendrites can create a short circuit within the battery’s flammable liquid. Lithium-ion batteries occasionally have the same problem, but dendrites have been a non-starter for lithium metal rechargeable batteries to date.

    “We’re addressing the holy grail of lithium metal batteries,” said Zhenan Bao, a professor of chemical engineering, who is senior author of the paper along with Yi Cui, professor of materials science and engineering and of photon science at SLAC. Bao added that dendrites had prevented lithium metal batteries from being used in what may be the next generation of electric vehicles.

    The promise

    Lithium metal batteries can hold at least a third more power per pound as lithium-ion batteries do and are significantly lighter because they use lightweight lithium for the positively charged end rather than heavier graphite. If they were more reliable, these batteries could benefit portable electronics from notebook computers to cell phones, but the real pay dirt, Cui said, would be for cars. The biggest drag on electric vehicles is that their batteries spend about a fourth of their energy carrying themselves around. That gets to the heart of EV range and cost.

    2
    Lead authors and PhD students David Mackanic, left, and Zhiao Yu in front of their battery tester. Yu is holding a dish of already tested cells that they call the “battery graveyard.” (Image credit: Mark Golden)

    “The capacity of conventional lithium-ion batteries has been developed almost as far as it can go,” said Stanford PhD student David Mackanic, co-lead author of the study. “So, it’s crucial to develop new kinds of batteries to fulfill the aggressive energy density requirements of modern electronic devices.”

    The team from Stanford and SLAC tested their coating on the positively charged end – called the anode – of a standard lithium metal battery, which is where dendrites typically form. Ultimately, they combined their specially coated anodes with other commercially available components to create a fully operational battery. After 160 cycles, their lithium metal cells still delivered 85 percent of the power that they did in their first cycle. Regular lithium metal cells deliver about 30 percent after that many cycles, rendering them nearly useless even if they don’t explode.

    The new coating prevents dendrites from forming by creating a network of molecules that deliver charged lithium ions to the electrode uniformly. It prevents unwanted chemical reactions typical for these batteries and also reduces a chemical buildup on the anode, which quickly devastates the battery’s ability to deliver power.

    “Our new coating design makes lithium metal batteries stable and promising for further development,” said the other co-lead author, Stanford PhD student Zhiao Yu.

    The group is now refining their coating design to increase capacity retention and testing cells over more cycles.

    “While use in electric vehicles may be the ultimate goal,” said Cui, “commercialization would likely start with consumer electronics to demonstrate the battery’s safety first.”

    Zhenan Bao and Yi Cui are also senior fellows at Stanford’s Precourt Institute for Energy. Other Stanford researchers include Jian Qin, assistant professor of chemical engineering; postdoctoral scholars Dawei Feng, Jiheong James Kang, Minah Lee, Chibueze Amanchukwu, Xuzhou Yan, Hansen Wang and Kai Liu; students Wesley Michaels, Allen Pei, Shucheng Chen and Yuchi Tsao; and visiting scholar Qiuhong Zhang from Nanjing University.

    This work was supported by the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy. The facility used at Stanford is supported by the National Science Foundation.

    See the full article here .


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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 10:45 am on August 29, 2019 Permalink | Reply
    Tags: , Jenga chemistry, , , SLAC National Accelerator Laboratory,   

    From SLAC National Accelerator Lab: “First report of superconductivity in a nickel oxide material” 

    August 28, 2019
    Glennda Chui
    glennda@slac.stanford.edu
    (650) 926-4897

    Made with ‘Jenga chemistry,’ the discovery could help crack the mystery of how high-temperature superconductors work.

    1
    An illustration depicts a key step in creating a new type of superconducting material: Much like pulling blocks from a tower in a Jenga game, scientists used chemistry to neatly remove a layer of oxygen atoms. This flipped the material into a new atomic structure – a nickelate – that can conduct electricity with 100 percent efficiency. (Greg Stewart/SLAC National Accelerator Laboratory)

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have made the first nickel oxide material that shows clear signs of superconductivity – the ability to transmit electrical current with no loss.

    Also known as a nickelate, it’s the first in a potential new family of unconventional superconductors that’s very similar to the copper oxides, or cuprates, whose discovery in 1986 raised hopes that superconductors could someday operate at close to room temperature and revolutionize electronic devices, power transmission and other technologies. Those similarities have scientists wondering if nickelates could also superconduct at relatively high temperatures.

    At the same time, the new material seems different from the cuprates in fundamental ways – for instance, it may not contain a type of magnetism that all the superconducting cuprates have – and this could overturn leading theories of how these unconventional superconductors work. After more than three decades of research, no one has pinned that down.

    The experiments were led by Danfeng Li, a postdoctoral researcher with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC, and described today in Nature.

    2

    “This is a very important discovery that requires us to rethink the details of the electronic structure and possible mechanisms of superconductivity in these materials,” said George Sawatzky, a professor of physics and chemistry at the University of British Columbia who was not involved in the study but wrote a commentary that accompanied the paper in Nature. “This is going to cause an awful lot of people to jump into investigating this new class of materials, and all sorts of experimental and theoretical work will be done.”

    3
    To create a new type of superconducting material, scientists at SLAC and Stanford first made a thin film of a common material known as perovskite, left; “doped” it with strontium; and then exposed it to a chemical that yanked out a layer of oxygen atoms, much like removing a stick from a tower of Jenga blocks. This made the film flip into a different atomic structure known as a nickelate, right. Tests showed that this nickelate can conduct electricity with no resistance. (Danfeng Li/SLAC National Accelerator Laboratory and Stanford University)

    A difficult path

    Ever since the cuprate superconductors were discovered, scientists have dreamed of making similar oxide materials based on nickel, which is right next to copper on the periodic table of the elements.

    But making nickelates with an atomic structure that’s conducive to superconductivity turned out to be unexpectedly hard.

    “As far as we know, the nickelate we were trying to make is not stable at the very high temperatures – about 600 degrees Celsius – where these materials are normally grown,” Li said. “So we needed to start out with something we can stably grow at high temperatures and then transform it at lower temperatures into the form we wanted.”

    He started with a perovskite – a material defined by its unique, double-pyramid atomic structure – that contained neodymium, nickel and oxygen. Then he doped the perovskite by adding strontium; this is a common process that adds chemicals to a material to make more of its electrons flow freely.

    This stole electrons away from nickel atoms, leaving vacant “holes,” and the nickel atoms were not happy about it, Li said. The material was now unstable, making the next step – growing a thin film of it on a surface – really challenging; it took him half a year to get it to work.

    ‘Jenga chemistry’

    Once that was done, Li cut the film into tiny pieces, loosely wrapped it in aluminum foil and sealed it in a test tube with a chemical that neatly snatched away a layer of its oxygen atoms – much like removing a stick from a wobbly tower of Jenga blocks. This flipped the film into an entirely new atomic structure – a strontium-doped nickelate.


    SIMES researcher Danfeng Li explains the delicate ‘Jenga chemistry’ behind making a new nickel oxide material, the first in a potential new family of unconventional superconductors. (Linda McCulloch, SLAC National Accelerator Laboratory)

    “Each of these steps had been demonstrated before,” Li said, “but not in this combination.”

    He remembers the exact moment in the laboratory, around 2 a.m., when tests indicated that the doped nickelate might be superconducting. Li was so excited that he stayed up all night, and in the morning co-opted the regular meeting of his research group to show them what he’d found. Soon, many of the group members joined him in a round-the-clock effort to improve and study this material.

    Further testing would reveal that the nickelate was indeed superconducting in a temperature range from 9-15 kelvins – incredibly cold, but a first start, with possibilities of higher temperatures ahead.

    More work ahead

    Research on the new material is in a “very, very early stage, and there’s a lot of work ahead,” cautioned Harold Hwang, a SIMES investigator, professor at SLAC and Stanford and senior author of the report. “We have just seen the first basic experiments, and now we need to do the whole battery of investigations that are still going on with cuprates.”

    Among other things, he said, scientists will want to dope the nickelate material in various ways to see how this affects its superconductivity across a range of temperatures, and determine whether other nickelates can become superconducting. Other studies will explore the material’s magnetic structure and its relationship to superconductivity.

    SIMES researchers from the Stanford departments of Physics, Applied Physics and Materials Science and Engineering also contributed to the study, which was funded by the DOE Office of Science and the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative.

    See the full article here .


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    Please help promote STEM in your local schools.

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    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 9:15 am on August 19, 2019 Permalink | Reply
    Tags: "Brookhaven Completes LSST's Digital Sensor Array", , , , , , , , SLAC National Accelerator Laboratory   

    From Brookhaven National Lab: “Brookhaven Completes LSST’s Digital Sensor Array” 

    From Brookhaven National Lab

    August 19, 2019

    Stephanie Kossman
    skossman@bnl.gov
    (631) 344-8671

    Peter Genzer,
    genzer@bnl.gov
    (631) 344-3174

    Brookhaven National Lab has finished constructing the 3.2 gigapixel “digital film” for the world’s largest camera for cosmology, physics, and astronomy.

    1
    SLAC National Accelerator Laboratory installs the first of Brookhaven’s 21 rafts that make up LSST’s digital sensor array. Photo courtesy SLAC National Accelerator Laboratory.

    After 16 years of dedicated planning and engineering, scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have completed a 3.2 gigapixel sensor array for the camera that will be used in the Large Synoptic Survey Telescope (LSST), a massive telescope that will observe the universe like never before.

    LSST

    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    “This is the biggest charge-coupled device (CCD) array that has ever been built,” said Paul O’Connor, senior scientist at Brookhaven Lab’s instrumentation division. “It’s three billion pixels. No telescope has ever put this many sensors into one camera.”

    The digital sensor array is composed of about 200 16-megapixel sensors, divided into 21 modules called “rafts.” Each raft can function on its own, but when combined, they will view an area of sky that can fit more than 40 full moons in a single image. Researchers will stitch these images together to create a time-lapse movie of the complete visible universe accessible from Chile.

    Currently under construction on a mountaintop in Chile, LSST is designed to capture the most complete images of our universe that have ever been achieved. The project to build the telescope facility and camera is a collaborative effort among more than 30 institutions from around the world, and it is primarily funded by DOE’s Office of Science and the National Science Foundation. DOE’s SLAC National Accelerator Laboratory is leading the overall effort to construct the camera—the world’s largest camera for astronomy—while Brookhaven led the design, construction, and qualification of the digital sensor array—the “digital film” for the camera.

    “It’s the heart of the camera,” said Bill Wahl, science raft subsystem manager of the LSST project at Brookhaven Lab. “What we’ve done here at Brookhaven represents years of great work by many talented scientists, engineers, and technicians. Their work will lead to a collection of images that has never been seen before by anyone. It’s an exciting time for the project and for the Lab.”

    2
    Members of the LSST project team at Brookhaven Lab are shown with a prototype raft cryostat. In addition to the rafts, Brookhaven scientists designed and built the cryostats that hold and cool the rafts to -100° Celsius.

    Brookhaven began its LSST research and development program in 2003, with construction of the digital sensor array starting in 2014. In the time leading up to construction, Brookhaven designed and fabricated the assembly and test equipment for the science rafts used both at Brookhaven and SLAC. The Laboratory also created an entire automated production facility and cleanroom, along with production and tracking software.

    “We made sure to automate as much of the production facility as possible,” O’Connor said. “Testing a single raft could take up to three days. We were working on a tight schedule, so we had our automated facility running 24/7. Of course, out of a concern for safety, we always had someone monitoring the facility throughout the day and night.”

    Constructing the complex sensor array, which operates in a vacuum and must be cooled to -100° Celsius, is a challenge on its own. But the Brookhaven team was also tasked with testing each fully assembled raft, as well as individual sensors and electronics. Once each raft was complete, it needed to be carefully packaged in a protective environment to be safely shipped across the country to SLAC.

    The LSST team at Brookhaven completed the first raft in 2017. But soon after, they were presented with a new challenge.

    “We later discovered that design features inadvertently led to the possibility that electrical wires in the rafts could get shorted out,” O’Connor said. “The rate at which this effect was impacting the rafts was only on the order of 0.2%, but to avoid any possibility of degradation, we went through the trouble of refitting almost every raft.”

    Now, just two years after the start of raft production, the team has successfully built and shipped the final raft to SLAC for integration into the camera. This marks the end of a 16-year project at Brookhaven, which will be followed by many years of astronomical observation.

    Many of the talented team members recruited to Brookhaven for the LSST project were young engineers and technicians hired right out of graduate school. Now, they’ve all been assigned to ongoing physics projects at the Lab, such as upgrading the PHENIX detector at the Relativistic Heavy Ion Collider—a DOE Office of Science User Facility for nuclear physics research—to sPHENIX [see RHIC components below], as well as ongoing work with the ATLAS detector at CERN’s Large Hadron Collider. Brookhaven is the U.S. host laboratory for the ATLAS collaboration.

    CERN ATLAS Image Claudia Marcelloni

    “Brookhaven’s role in the LSST camera project afforded new and exciting opportunities for engineers, technicians, and scientists in electro-optics, where very demanding specifications must be met,” Wahl said. “The multi-disciplined team we assembled did an excellent job achieving design objectives and I am proud of our time together. Watching junior engineers and scientists grow into very capable team members was extremely rewarding.”

    Brookhaven Lab will continue to play a strong role in LSST going forward. As the telescope undergoes its commissioning phase, Brookhaven scientists will serve as experts on the digital sensor array in the camera. They will also provide support during LSST’s operations, which are projected to begin in 2022.

    3
    SLAC National Accelerator Laboratory installs the first of Brookhaven’s 21 rafts that make up LSST’s digital sensor array. Photo courtesy SLAC National Accelerator Laboratory.

    “The commissioning of such a complex camera will be an exciting and challenging endeavor,” said Brookhaven physicist Andrei Nomerotski, who is leading Brookhaven’s contributions to the commissioning and operation phases of the LSST project. “After years of using artificial signal sources for the sensor characterization, we are looking forward to seeing real stars and galaxies in the LSST CCDs.”

    Once operational in the Andes Mountains, LSST will serve nearly every subset of the astrophysics community. Perhaps most importantly, LSST will enable scientists to investigate dark energy and dark matter—two puzzles that have baffled physicists for decades. It is also estimated that LSST will find millions of asteroids in our solar system, in addition to offering new information about the creation of our galaxy. The images captured by LSST will be made available to physicists and astronomers in the U.S. and Chile immediately, making LSST one of the most advanced and accessible cosmology experiments ever created. Over time, the data will be made available to the public worldwide.

    See the full article here .


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    BNL Campus


    BNL Center for Functional Nanomaterials

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 8:28 am on August 18, 2019 Permalink | Reply
    Tags: , , LCLS, , , , SLAC National Accelerator Laboratory, SSRL-Stanford Synchrotron Light Source, ,   

    From SLAC National Accelerator Lab: “Scientists report two advances in understanding the role of ‘charge stripes’ in superconducting materials” 

    From SLAC National Accelerator Lab

    Ali Sundermier
    Glennda Chui

    The studies could lead to a new understanding of how high-temperature superconductors operate.

    High-temperature superconductors, which carry electricity with zero resistance at much higher temperatures than conventional superconducting materials, have generated a lot of excitement since their discovery more than 30 years ago because of their potential for revolutionizing technologies such as maglev trains and long-distance power lines. But scientists still don’t understand how they work.

    One piece of the puzzle is the fact that charge density waves – static stripes of higher and lower electron density running through a material – have been found in one of the major families of high-temperature superconductors, the copper-based cuprates. But do these charge stripes enhance superconductivity, suppress it or play some other role?

    In independent studies, two research teams report important advances in understanding how charge stripes might interact with superconductivity. Both studies were carried out with X-rays at the Department of Energy’s SLAC National Accelerator Laboratory.

    Exquisite detail

    In a paper published today in Science Advances, researchers from the University of Illinois at Urbana-Champaign (UIUC) used SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser [below] to observe fluctuations in charge density waves in a cuprate superconductor.

    1
    This cutaway view shows stripes of higher and lower electron density – “charge stripes” – within a copper-based superconducting material. Experiments with SLAC’s X-ray laser directly observed how those stripes fluctuate when hit with a pulse of light, a step toward understanding how they interact with high-temperature superconductivity. (Greg Stewart/SLAC National Accelerator Laboratory)

    They disturbed the charge density waves with pulses from a conventional laser and then used RIXS, or resonant inelastic X-ray scattering, to watch the waves recover over a period of a few trillionths of a second. This recovery process behaved according to a universal dynamical scaling law: It was the same at all scales, much as a fractal pattern looks the same whether you zoom in or zoom out.

    With LCLS, the scientists were able to measure, for the first time and in exquisite detail, exactly how far and how fast the charge density waves fluctuated. To their surprise, the team discovered that the fluctuations were not like the ringing of a bell or the bouncing of a trampoline; instead, they were more like the slow diffusion of a syrup – a quantum analog of liquid crystal behavior, which had never been seen before in a solid.

    “Our experiments at LCLS establish a new way to study fluctuations in charge density waves, which could lead to a new understanding of how high-temperature superconductors operate,” says Matteo Mitrano, a postdoctoral researcher in professor Peter Abbamonte’s group at UIUC.

    This team also included researchers from Stanford University, the National Institute of Standards and Technology and Brookhaven National Laboratory.

    Hidden arrangements

    Another study, reported last month in Nature Communications, used X-rays from SLAC’S Stanford Synchrotron Radiation Lightsource (SSRL) to discover two types of charge density wave arrangements, making a new link between these waves and high-temperature superconductivity.

    SLAC/SSRL

    Led by SLAC scientist Jun-Sik Lee, the research team used RSXS, or resonant soft X-ray scattering, to watch how temperature affected the charge density waves in a cuprate superconductor.

    “This resolves a mismatch in data from previous experiments and charts a new course for fully mapping the behaviors of electrons in these exotic superconducting materials,” Lee says.

    “I believe that exploring new or hidden arrangements, as well as their intertwining phenomena, will contribute to our understanding of high-temperature superconductivity in cuprates, which will inform researchers in their quest to design and develop new superconductors that work at warmer temperatures.”

    The team also included researchers from Stanford, Pohang Accelerator Laboratory in South Korea and Tohoku University in Japan.

    SSRL and LCLS are DOE Office of Science user facilities. Both studies were supported by the Office of Science.

    See the full article here .


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

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:03 am on August 12, 2019 Permalink | Reply
    Tags: "Atomic ‘Trojan horse’ could inspire new generation of X-ray lasers and particle colliders", 'Sneaking’ electrons into plasma., A potentially much brighter electron source based on plasma that could be used in more compact more powerful particle accelerators., , “Supermicroscopes” that can resolve atomic and subatomic details., , Plasma wake, Plasma Wakefield Acceleration, Referred to as the Trojan horse technique because it’s reminiscent of the way the ancient Greeks are said to have invaded the city of Troy., , , SLAC National Accelerator Laboratory, Trailing electrons can “surf” the wake and gain tremendous amounts of energy.   

    From SLAC National Accelerator Lab: “Atomic ‘Trojan horse’ could inspire new generation of X-ray lasers and particle colliders” 

    From SLAC National Accelerator Lab

    August 12, 2019
    Manuel Gnida

    1
    Illustration, based on simulations, of the Trojan horse technique for the production of high-energy electron beams. A laser beam (red, at left) strips electrons (blue dots) off of helium atoms. Some of the freed electrons (red dots) get accelerated inside a plasma bubble (white elliptical shape) created by an electron beam (green). (Thomas Heinemann/University of Strathclyde)

    5

    At SLAC’s FACET facility, researchers have produced an intense electron beam by ‘sneaking’ electrons into plasma, demonstrating a method that could be used in future compact discovery machines that explore the subatomic world.


    SLAC FACET

    How do researchers explore nature on its most fundamental level? They build “supermicroscopes” that can resolve atomic and subatomic details. This won’t work with visible light, but they can probe the tiniest dimensions of matter with beams of electrons, either by using them directly in particle colliders or by converting their energy into bright X-rays in X-ray lasers. At the heart of such scientific discovery machines are particle accelerators that first generate electrons at a source and then boost their energy in a series of accelerator cavities.

    Now, an international team of researchers, including scientists from the Department of Energy’s SLAC National Accelerator Laboratory, has demonstrated a potentially much brighter electron source based on plasma that could be used in more compact, more powerful particle accelerators.

    The method, in which the electrons for the beam are released from neutral atoms inside the plasma, is referred to as the Trojan horse technique because it’s reminiscent of the way the ancient Greeks are said to have invaded the city of Troy by hiding their forceful soldiers (electrons) inside a wooden horse (plasma), which was then pulled into the city (accelerator).

    “Our experiment shows for the first time that the Trojan horse method actually works,” says Bernhard Hidding from the University of Strathclyde in Glasgow, Scotland, the principal investigator of a study published today in Nature Physics. “It’s one of the most promising methods for future electron sources and could push the boundaries of today’s technology.”

    Replacing metal with plasma

    In current state-of-the-art accelerators, electrons are generated by shining laser light onto a metallic photocathode, which kicks electrons out of the metal. These electrons are then accelerated inside metal cavities, where they draw more and more energy from a radiofrequency field, resulting in a high-energy electron beam. In X-ray lasers, such as SLAC’s Linac Coherent Light Source (LCLS), the beam drives the production of extremely bright X-ray light.

    But metal cavities can only support a limited energy gain over a given distance, or acceleration gradient, before breaking down, and therefore accelerators for high-energy beams become very large and expensive. In recent years, scientists at SLAC and elsewhere have looked into ways to make accelerators more compact. They demonstrated, for example, that they can replace metal cavities with plasma that allows much higher acceleration gradients, potentially shrinking the length of future accelerators 100 to 1,000 times.

    The new paper expands the plasma concept to the electron source of an accelerator.

    “We’ve previously shown that plasma acceleration can be extremely powerful and efficient, but we haven’t been able yet to produce beams with high enough quality for future applications,” says co-author Mark Hogan from SLAC. “Improving beam quality is a top priority for the next years, and developing new types of electron sources is an important part of that.”

    According to previous calculations [Nature Communications] by Hidding and colleagues, the Trojan horse technique could make electron beams 100 to 10,000 times brighter than today’s most powerful beams. Brighter electron beams would also make future X-ray lasers brighter and further enhance their scientific capabilities.

    “If we’re able to marry the two major thrusts – high acceleration gradients in plasma and beam creation in plasma – we could be able to build X-ray lasers that unfold the same power over a distance of a few meters rather than kilometers,” says co-author James Rosenzweig, the principal investigator for the Trojan horse project at the University of California, Los Angeles.

    3
    Animation illustrating the concept of the Trojan horse method. An electron bunch from SLAC’s FACET facility (bright spot at right) passes through hydrogen plasma (purple), which creates a plasma bubble (blue). As the bubble moves through the plasma at nearly the speed of light, a laser pulse strips electrons (white dots) off of neutral helium atoms inside the plasma. The released electrons are trapped in the tail of the bubble where they gain energy (bright spot at left). (Greg Stewart/SLAC National Accelerator Laboratory)

    Producing superior electron beams

    The researchers carried out their experiment at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET). The facility, which is currently undergoing a major upgrade, generates pulses of highly energetic electrons for research on next-generation accelerator technologies, including plasma acceleration.

    First, the team flashed laser light into a mixture of hydrogen and helium gas. The light had just enough energy to strip electrons off hydrogen, turning neutral hydrogen into plasma. It wasn’t energetic enough to do the same with helium, though, whose electrons are more tightly bound than those for hydrogen, so it stayed neutral inside the plasma.

    Then, the scientists sent one of FACET’s electron bunches through the plasma, where it produced a plasma wake, much like a motorboat creates a wake when it glides through the water. Trailing electrons can “surf” the wake and gain tremendous amounts of energy.

    In this study, the trailing electrons came from within the plasma (see animation above and movie below). Just when the electron bunch and its wake passed by, the researchers zapped the helium in the plasma with a second, tightly focused laser flash. This time the light pulse had enough energy to kick electrons out of the helium atoms, and the electrons were then accelerated in the wake.

    The synchronization between the electron bunch, rushing through the plasma with nearly the speed of light, and the laser flash, lasting merely a few millionths of a billionth of a second, was particularly important and challenging, says UCLA’s Aihua Deng, one of the study’s lead authors: “If the flash comes too early, the electrons it produces will disturb the formation of the plasma wake. If it comes too late, the plasma wake has moved on and the electrons won’t get accelerated.”

    The researchers estimate that the brightness of the electron beam obtained with the Trojan horse method can already compete with the brightness of existing state-of-the-art electron sources.

    “What makes our technique transformative is the way the electrons are produced,” says Oliver Karger, the other lead author, who was at the University of Hamburg, Germany, at the time of the study. When the electrons are stripped off the helium, they get rapidly accelerated in the forward direction, which keeps the beam narrowly bundled and is a prerequisite for brighter beams.


    Computer simulation of the Trojan horse method. An electron bunch from SLAC’s FACET facility passed through hydrogen plasma and created a plasma bubble. A laser flash (dark red circular area) strips electrons off of neutral helium atoms (not shown) drifting inside the plasma. The released electrons are sucked into the tail of the bubble (trajectories shown in green), where they gain energy (color change from black to orange dots). The plasma bubble, shown stationary here, travels through the plasma with nearly the speed of light. (Daniel Ullmann and Andrew Beaton/University of Strathclyde)

    More R&D work ahead

    But before applications like compact X-ray lasers could become a reality, much more research needs to be done.

    Next, the researchers want to improve the quality and stability of their beam and work on better diagnostics that will allow them to measure the actual beam brightness, instead of estimating it.

    These developments will be done once the FACET upgrade, FACET-II, is completed. “The experiment relies on the ability to use a strong electron beam to produce the plasma wake,” says Vitaly Yakimenko, director of SLAC’s FACET Division. “FACET-II will be the only place in the world that will produce such beams with high enough intensity and energy.”


    Animation, based on simulations, of the Trojan horse technique for the production of high-energy electron beams in perpendicular geometry (90 degrees between laser and electron beams) as realized at SLAC. A laser beam (red, from right to left) strips electrons (blue dots) off of helium atoms. Some of the freed electrons (purplish to yellowish dots) get accelerated inside a plasma bubble (white elliptical shape) created by an electron beam (green). (Thomas Heinemann/University of Strathclyde)


    Animation, based on simulations, of the Trojan horse technique for the production of high-energy electron beams in collinear geometry (laser and electron beams aligned). A focused laser beam (orange-red) strips electrons (initially blue dots) off of helium atoms. All these freed electrons get accelerated (visualized by increasingly green color) inside a plasma bubble (white elliptical shape) created by an electron beam (green). (Thomas Heinemann, Andrew Beaton/University of Strathclyde)

    Other partners involved in the project were Sci-Tech Daresbury, UK; the German research center DESY; the University of Colorado Boulder; the University of Oslo, Norway; the University of Texas at Austin; RadiaBeam Technologies; RadiaSoft LLC; and Tech-X Corporation. Large parts of this work were funded by the DOE Office of Science. LCLS and FACET are DOE Office of Science user facilities.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 7:31 am on July 12, 2019 Permalink | Reply
    Tags: , , , , , SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “Light dark matter is a thousand times less likely to bump into regular matter than previous astrophysical analyses allowed” 

    From SLAC National Accelerator Lab

    July 11, 2019
    Manuel Gnida

    1
    Simulation of the dark matter structure surrounding the Milky Way. Driven by gravity, dark matter forms dense structures, referred to as halos (bright areas), in which galaxies are born. The number and distribution of halos, and therefore also of galaxies, depends on the properties of dark matter, such as its mass and its likelihood to interact with normal matter. (Ethan Nadler/Risa Wechsler/Ralf Kaehler/SLAC National Accelerator Laboratory/Stanford University)

    A team led by scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University has narrowed down how strongly dark matter particles might interact with normal matter. Based on the number and distribution of small satellite galaxies seen orbiting our Milky Way, the team found this interaction to be at least a thousand times weaker than the strongest interaction allowed by previous astrophysical analyses.

    “Improving our understanding of these interactions is important because it’s one of the factors that helps us determine what dark matter can and cannot be,” said Risa Wechsler, director of the SLAC/Stanford Kavli Institute for Particle Astrophysics and Cosmology and the study’s senior author. The study can also help researchers refine their models for the evolution of the universe because dark matter and its interactions with gravity play such a fundamental role in how galaxies form, she said.

    Study lead author Ethan Nadler, a graduate student working with Wechsler, said, “Our results exclude dark matter properties in a mass range that has been largely unexplored before, nicely complementing the outcomes of other experiments that set tight limits for heavier dark matter particles.”

    The researchers recently published their results in The Astrophysical Journal Letters.

    The ‘missing satellites conundrum

    Most of the structure in today’s universe can be explained with a quite simple dark matter model. It assumes that dark matter is relatively “cold,” meaning it moved very slowly compared to the speed of light, and “collisionless,” meaning it doesn’t interact with itself or regular matter. As the universe expands, gravity causes dark matter to clump together and form dense dark matter halos. Dark matter also pulls in regular matter around it, concentrating regular matter and initiating galaxy formation inside dark matter halos.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation


    Simulation of the formation of the dark matter structure surrounding the Milky Way, from the early universe to today. Gravity makes dark matter clump together and form dense structures, referred to as halos (bright areas). The number and distribution of halos depends on the properties of dark matter, such as its mass and its likelihood to interact with normal matter. Galaxies are thought to form inside these halos. In a new study, SLAC and Stanford researchers have used measurements of faint satellite galaxies orbiting the Milky Way to derive limits on how often dark matter particles can possibly collide with regular matter particles. (Ethan Nadler/Risa Wechsler/R. Kaehler/SLAC National Accelerator Laboratory/Stanford University)

    This “cold dark matter” model works well on very large scales, including clusters of galaxies, and describes how typical galaxies are clustered in the universe. But on much smaller scales – for galaxies smaller than our Milky Way, for example – the simple model seemed to cause problems.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    It predicts that the Milky Way’s halo is surrounded by thousands of smaller subhalos, so there should be also thousands of smaller satellite galaxies orbiting our galaxy. Yet, by the early 2000s, researchers only knew of about 10 of them.

    “The apparent discrepancy between observations and predictions made people think there is a serious issue with the model, but recently this has become less of a problem,” Nadler said.

    “Increasingly sensitive astrophysical surveys have discovered many more faint satellite galaxies, and we expect next-generation instruments like the Large Synoptic Survey Telescope to find hundreds more if the simplest cold dark matter model is correct.

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Thus, if fewer galaxies are observed, this could indicate that the simplest model is not exactly correct,” he said. “At the same time, we don’t expect the smallest halos to host galaxies, so understanding the connection between galaxies and halos is crucial to make conclusions about the nature of dark matter.”

    Limiting what dark matter can be

    One way the dark matter model can be modified is by assuming that dark matter was produced in a “warmer” state in the early universe, meaning it moved faster than in the simple model and was less likely to clump. This would result in a smaller number of dark matter halos and cut down the number of observable satellite galaxies. Because the mass of dark matter controls its velocity when it was produced in the early universe, the abundance of satellites can be used to determine the minimum mass of warm dark matter particles.

    Here, the researchers looked at a different property of dark matter in other non-standard models: its interaction with normal matter. They showed that collisions between dark matter particles and regular matter particles like protons and neutrons would also reduce the observable satellite population.

    “If the interaction is very strong, it erases small dark matter halos and suppresses a lot of the small structure,” Wechsler said. “But we can actually see some smaller structures based on the tiny galaxies they host, so the interaction can’t be too strong either.” In other words, the number of observable satellite galaxies provides a path to learning about these fundamental interactions.

    In their study, the team varied the strength of the collision interaction in their dark matter model and ran simulations to predict how that affected the distribution of dark matter halos. Then, they tried to fit known satellite galaxies into the halos.

    “What’s really exciting is that our study nicely bridges experimental observations of faint galaxies today with theories of dark matter and its behavior in the early universe. It connects a lot of pieces, and by doing so it tells us something very profound about dark matter,” Nadler said.

    The researchers found that in order to make everything fit together, dark matter particles with relatively low mass must interact at least a thousand times more weakly with normal matter than the previous limit. Before this work, the leading constraint in this mass range were set by astrophysical studies based on the cosmic microwave background, the earliest light in the universe. Meanwhile, direct detection experiments, which search for signs of dark matter with sensitive underground detectors, set stringent limits on the interaction strength for heavier dark matter particles, making studies of satellite galaxies highly complementary to those experiments.

    “Although we still don’t know what dark matter is made of, our results are a step forward that sets tighter limits on what it actually can be,” Nadler said.

    Other researchers involved in the study were Vera Gluscevic at the University of Southern California and Kimberly Boddy at Johns Hopkins University. Financial support came from the National Science Foundation and the Department of Energy.

    See the full article here .


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

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:11 am on June 26, 2019 Permalink | Reply
    Tags: , , Cryo-EM imaging, First snapshots of trapped CO2 molecules shed new light on carbon capture, , SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “First snapshots of trapped CO2 molecules shed new light on carbon capture” 

    From SLAC National Accelerator Lab

    June 26, 2019
    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    A new twist on cryo-EM imaging reveals what’s going on inside MOFs, highly porous nanoparticles with big potential for storing fuel, separating gases and removing carbon dioxide from the atmosphere.

    1
    Scientists used instruments at the Stanford-SLAC Cryo-EM Facilities (left) to make the first images of carbon dioxide molecules trapped in molecular cages (right) within a porous nanoparticle. The results will aid efforts to develop nanoparticles for capturing and storing liquids and gases, including carbon dioxide. (SLAC National Accelerator Laboratory/Li et al., Matter, 26 June 2019)

    Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have taken the first images of carbon dioxide molecules within a molecular cage ­­– part of a highly porous nanoparticle known as a MOF, or metal-organic framework, with great potential for separating and storing gases and liquids.

    The images, made at the Stanford-SLAC Cryo-EM Facilities, show two configurations of the CO2 molecule in its cage, in what scientists call a guest-host relationship; reveal that the cage expands slightly as the CO2 enters; and zoom in on jagged edges where MOF particles may grow by adding more cages.

    “This is a groundbreaking achievement that is sure to bring unprecedented insights into how these highly porous structures carry out their exceptional functions, and it demonstrates the power of cryo-EM for solving a particularly difficult problem in MOF chemistry,” said Omar Yaghi, a professor at the University of California, Berkeley and a pioneer in this area of chemistry, who was not involved in the study.

    The research team, led by SLAC/Stanford professors Yi Cui and Wah Chiu, described the study today in the journal Matter.

    2
    Cryo-EM images show a slice through a single MOF particle in atomic detail (left), revealing cage-like molecules (center) that can trap other molecules inside. The image at right shows carbon dioxide molecules trapped in one of the cages – the first time this has ever been observed. Bottom right, a drawing of the molecular structure of the cage and the trapped carbon dioxide. (Li et al., Matter, 26 June 2019)

    Tiny specks with enormous surfaces

    MOFs have the largest surface areas of any known material. A single gram, or three hundredths of an ounce, can have a surface area nearly the size of two football fields, offering plenty of space for guest molecules to enter millions of host cages.

    Despite their enormous commercial potential and two decades of intense, accelerating research, MOFs are just now starting to reach the market. Scientists across the globe engineer more than 6,000 new types of MOF particles per year, looking for the right combinations of structure and chemistry for particular tasks, such as increasing the storage capacity of gas tanks or capturing and burying CO2 from smokestacks to combat climate change.

    “According to the Intergovernmental Panel on Climate Change, limiting global temperature increases to 1.5 degrees Celsius will require some form of carbon capture technology,” said Yuzhang Li, a Stanford postdoctoral researcher and lead author of the report. “These materials have the potential to capture large quantities of CO2, and understanding where the CO2 is bound inside these porous frameworks is really important in designing materials that do that more cheaply and efficiently.”

    One of the most powerful methods for observing materials is transmission electron microscopy, or TEM, which can make images in atom-by-atom detail. But many MOFs, and the bonds that hold guest molecules inside them, melt into blobs when exposed to the intense electron beams needed for this type of imaging.

    A few years ago, Cui and Li adopted a method that’s been used for many years to study biological samples: Freeze samples so they hold up better under electron bombardment. They used an advanced TEM instrument at the Stanford Nano Shared Facilities to examine flash-frozen samples containing dendrites – finger-like growths of lithium metal that can pierce and damage lithium-ion batteries – in atomic detail for the first time.

    Atomic images, one electron at a time

    For this latest study, Cui and Li used instruments at the Stanford-SLAC Cryo-EM Facilities, which have much more sensitive detectors that can pick up signals from individual electrons passing through a sample. This allowed the scientists to make images in atomic detail while minimizing the electron beam exposure.

    3
    In a new study, researchers trapped carbon dioxide molecules in highly porous nanoparticles called MOFs, flash-froze the particles in liquid nitrogen and examined them with cryo-EM at a Stanford-SLAC facility. The process allowed them to obtain the first atomic-scale images of individual carbon dioxide molecules within the particle’s cage-like pores. (Li et al., Matter, 26 June 2019)

    The MOF they studied is called ZIF-8. It came in particles just 100 billionths of a meter in diameter; you’d need to line about 900 of them up to match the width of a human hair. “It has high commercial potential because it’s very cheap and easy to synthesize,” said Stanford postdoctoral researcher Kecheng Wang, who played a key role in the experiments. “It’s already being used to capture and store toxic gases.”

    Cryo-EM not only let them make super-sharp images with minimal damage to the particles, but it also kept the CO2 gas from escaping while its picture was being taken. By imaging the sample from two angles, the investigators were able to confirm the positions of two of the four sites where CO2 is thought to be weakly held in place inside its cage.

    “I was really excited when I saw the pictures. It’s a brilliant piece of work,” said Stanford Professor Robert Sinclair, an expert in using TEM to study materials who helped interpret the team’s results. “Taking pictures of the gas molecules inside the MOFs is an incredible step forward.”

    4
    The new cryo-EM images also reveal step-like features at the edges of MOF particles (upper right) where scientists think new cages may form as the particle grows (bottom right). (Li et al., Matter, 26 June 2019)

    Major funding for this study came from the National Institutes of Health and the Department of Energy.

    See the full article here .


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

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 10:17 am on June 22, 2019 Permalink | Reply
    Tags: "Scientists make first high-res movies of proteins forming crystals in a living cell", , “The protein molecules are self-assembling building blocks and they will spontaneously form themselves into crystals No enzyme is required.”, , Microbial cell division, , Single-molecule tracking, SLAC National Accelerator Laboratory, Stimulated emission depletion, Super-resolution fluorescence microscopy   

    From SLAC National Accelerator Lab: “Scientists make first high-res movies of proteins forming crystals in a living cell” 

    From SLAC National Accelerator Lab

    June 21, 2019
    Glennda Chui

    A close-up look at how microbes build their crystalline shells has implications for understanding how cell structures form, preventing disease and developing nanotechnology.

    Scientists have made the first observations of proteins assembling themselves into crystals, one molecule at a time, in a living cell. The method they used to watch this happen – an extremely high-res form of molecular moviemaking ­– could shed light on other important biological processes and help develop nanoscale technologies inspired by nature.

    Led by researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, the study was published in Nature Communications today.

    “I’ve been super-excited to watch and track the movements of single molecules as they form this fascinating crystalline shell on the surface of a microbe,” said Stanford professor and study co-author W.E. Moerner, who shared the 2014 Nobel Prize in chemistry for stunning advances in pushing the boundaries of what optical microscopes can see. “We can look on a very fine scale and see the molecules arranging themselves in the shell. It’s the first time we’ve been able to do this.”

    The study focused on a bacterium called Caulobacter crescentus that lives in lakes and streams. It’s one of many microbes that sport a very thin crystalline shell, known as a surface layer or S-layer, made of identical protein building blocks.

    2
    An Illustration shows the cylindrical stalk of the microbe covered in a crystalline protein shell known as an S-layer. (Greg Stewart/SLAC National Accelerator Laboratory)

    3
    This illustration zooms in to show six-sided protein crystal “tiles” forming at top left and far right. (Greg Stewart/SLAC National Accelerator Laboratory)

    Scientists have been trying to figure out what roles these brittle shells play in the lives of their owners and how they come together to smoothly cover a microbe’s curvy surfaces. The research is driven not just by a desire to understand how nature works, but also by the possibility of applying that knowledge to create new types of nanotechnology – for instance, by using the protein shells as scaffolds for building “engineered living materials.” The shells also offer a potential target for drugs aimed at disarming infectious bacteria.

    In this study, the research team used two established techniques that transcend the previous resolution limitations of optical microscopy – super-resolution fluorescence microscopy and single-molecule tracking – to watch individual building blocks move around the surfaces of living bacteria and assemble themselves into a shell. The resulting images and movies revealed how protein building blocks crystallize to form the bacterium’s S-layer coat.

    “It’s like watching a pile of bricks self-assemble into a two-story house,” said Jonathan Herrmann, a PhD student at Stanford and SLAC who along with fellow Stanford PhD students Colin Comerci and Josh Yoon carried out the bulk of the work.

    4
    A still image shows the tracks (red, white and blue lines) of individual protein molecules moving around the surface of a microbe over a period of 60 seconds. One of the molecules has just bound to an existing patch of the shell (bottom), which is labeled with a green fluorescent tag. The microbe is outlined in orange. (Josh Yoon, Colin Comerci, Jonathan Herrmann/Stanford University)


    This high-res movie represents the first observation ever made of protein crystallization by a living cell. It shows single protein molecules (red) roving over the surface of a microbe over the course of two minutes; when they join an existing patch of the microbe’s shell (green) they crystallize like rock candy around a string. The molecules are tagged with fluorescent chemicals to make them visible. (Josh Yoon, Colin Comerci, Jonathan Herrmann/Stanford University)

    Following the glow

    Protein crystals are widespread in nature: in shells that surround many bacteria and almost all of the ancient microbes called Archaea, in the outer shells of viruses and even in the human eye. The bacteria that cause anthrax and salmonella infections have these crystalline shells; so does Clostridium difficile, which causes serious infections of the colon and intestines. A lot of research has been aimed at disrupting these shells to head off infection.

    The bacteria in this study don’t infect healthy people and are well-studied and understood, so they make good research subjects. Scientists know, among other things, that these bacteria can’t thrive without their shells, which are made from protein building blocks called RsaA. But shell assembly takes place at such a tiny scale that it had never been observed before.

    To watch it happen, the researchers stripped microbes of their S-layers and supplied them with synthetic RsaA building blocks labeled with chemicals that fluoresce in bright colors when stimulated with a particular wavelength of light.

    5
    These images show how a super-resolution fluorescence microscopy technique called STED produces much sharper images of microbial shell assembly (right) than a previous technique, confocal microscopy (left). Areas in red are places where the shell is growing: at the ends of the microbial cell, in the pinched middle section where it is preparing to divide and at cracks and defects in the shell. (Colin Comerci, Jonathan Herrmann/Stanford University)

    Then they tracked the glowing building blocks with single-molecule microscopy as they formed a shell that covered the microbe in a hexagonal, tile-like pattern in less than two hours. A technique called stimulated emission depletion (STED) microscopy allowed them to see structural details of the layer as small as 60 to 70 nanometers, or billionths of a meter, across – about one-thousandth the width of a human hair.

    The team discovered that the shell-building didn’t happen the way they thought: The RsaA blocks were not guided into position and joined to the shell by enzymes, which promote most biological reactions. Instead they randomly moved around, found a patch of existing shell and joined it, like rock candy crystallizing around a string dipped in sugar water.

    “The protein molecules are self-assembling building blocks, and they will spontaneously form themselves into crystals,” Herrmann said. “No enzyme is required.”

    6
    An illustration shows how protein building blocks secreted by a microbe (at arrows) travel over its surface until they encounter its growing crystalline shell. There they join one of the six-sided units that tile the microbe’s surface, crystallizing like rock candy around a string. (Greg Stewart/SLAC National Accelerator Laboratory)

    A new way of seeing

    Since the flat crystalline shell can never perfectly fit the constantly changing 3-D shape of the microbe – “It’s not a huge leap to say that if you try to bend the sheet to fit the microbe, you have to break it,” Comerci said – there are always small defects and gaps in coverage, and those places, he said, are where they saw the shell grow.

    “For the first time,” he said, “we were able to watch the S-layer proteins do things on their own.”

    7
    Sketch showing where the microbe’s crystalline shell would be expected to crack, based on the curvature of its surface as it grows and prepares to divide. The predicted cracks and defects are shown here in white. These are places where the crystalline shell tends to grow. (Colin Comerci/Stanford University)

    8
    A closer look at areas where shell growth is occurring. Green areas are existing patches of shell; red areas are new growth at cracks, the ends (poles) of the microbial cell and in the middle, where the microbe is growing and preparing to divide. (Colin Comerci, Jonathan Herrmann/Stanford University)

    This new way of observing shell formation “is opening up a new way to understand and eventually manipulate surface layer structures, both in living organisms and in isolation,” said co-author Soichi Wakatsuki, a professor at SLAC and Stanford who leads the Biological Sciences Division at the lab’s Stanford Synchrotron Radiation Lightsource.

    SLAC/SSRL

    “Now that we know how they assemble, we can modify their properties so they can do specific types of work, like forming new types of hybrid materials or attacking biomedical problems.”

    The next step, researchers said, is to find out how the crystallization process starts using higher resolution X-ray and electron imaging available at SLAC: How do the very first bits of the shell crystallize without the equivalent of the rock candy string?

    Optical microscopy for this study was carried out at the Moerner lab at Stanford. Researchers from the University of British Columbia and from Professor Lucy Shapiro’s laboratory at Stanford also contributed to this work, which was funded in part by the National Institute of General Medical Sciences and the Chan Zuckerberg Biohub. Work in Wakatsuki’s labs at SLAC and Stanford was partly funded by a Laboratory Directed Research and Development grant from SLAC and by the DOE Office of Biological and Environmental Research. The Stanford Synchrotron Radiation Lightsource is a DOE Office of Science user facility.

    See the full article here .


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    Please help promote STEM in your local schools.

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    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 5:11 pm on June 20, 2019 Permalink | Reply
    Tags: , , LZ experiment at SURF, , , Search for WIMPS, SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “SLAC sends off woven grids for LUX-ZEPLIN dark matter detector” 

    From SLAC National Accelerator Lab

    June 20, 2019
    Manuel Gnida

    Four large meshes made from 2 miles of metal wire will extract potential signals of dark matter particles.

    The ultra-sensitive LUX-ZEPLIN (LZ) detector is scheduled to begin its search for elusive dark matter next year.

    LBNL LZ project at SURF, Lead, SD, USA

    At its core: a large tank filled with 10 metric tons of liquid xenon whose atoms would produce telltale signals when struck by dark matter particles. Inside the tank, four high-voltage grids – fine circular metal meshes, each 5 feet in diameter – are needed to extract these signals.

    Over the past few months, the LZ team at the Department of Energy’s SLAC National Accelerator Laboratory, which is part of the international LZ collaboration of 250 scientists from 37 institutions, has carefully woven the grids from 2 miles of thin stainless steel wire, and yesterday they sent the last one on its way to the Sanford Underground Research Facility (SURF) in South Dakota, where the LZ detector is being assembled.


    Weaving the high-voltage grids of the LUX-ZEPLIN dark matter experiment. (Farrin Abbott/SLAC National Accelerator Laboratory)

    “Completion of the delivery of the grids from SLAC is one of the most critical project milestones,” said LZ Project Director Murdoch “Gil” Gilchriese of DOE’s Lawrence Berkeley National Laboratory, which leads the project.

    “Congratulations to the grids team.”

    The quality of the grids is critical to LZ’s performance, and making them was a major challenge, said Tom Shutt, one of the directors of SLAC’s LZ team: “It took us about four years to develop the design and to manufacture and test them. It’s exciting that we’re now integrating them into the detector.” The team’s efforts included inventing a clever way of weaving the grids from metal wires.

    Rare collisions with dark matter

    Scientists have overwhelming evidence that the matter we can see makes up only a small fraction of the universe. About 85 percent of matter is invisible and interacts with everything else almost entirely through gravity. This mysterious substance is called “dark matter,” and researchers believe it’s composed of particles, just like ordinary matter is made of fundamental particles. Yet, dark matter’s building blocks have yet to show up in experiments.

    Scientists have been trying to detect dark matter particles by putting tanks of liquefied noble gases, like xenon, deep underground. Most dark matter particles rush through these tanks unhindered while traveling through our planet as if it were made of air. But from time to time, scientists theorize, a particle might collide with a noble gas atom and produce a signal that reveals dark matter’s presence and nature.

    As the newest generation of this type of “direct detection” dark matter experiment, LZ will be hundreds of times more sensitive to a particular type of dark matter candidate, called weakly interacting massive particles (WIMPs), than its predecessor.


    Dark matter hunt with the LZ experiment. (Greg Stewart/SLAC National Accelerator Laboratory)

    From collisions to flashes of light

    If and when a WIMP particle hits a xenon atom in LZ’s tank, two things will happen: The atom will emit a flash of light that is recorded by nearly 500 light-sensitive detectors, called photomultiplier tubes (PMTs), at the top and bottom of the tank. The atom will also release electrons, and that’s where the high-voltage grids come in.

    Two of the grids – the cathode at the bottom and the gate at the top – will help create an electric field that pushes electrons through the liquid xenon toward the top of the tank. There, they’ll be extracted from the liquid by a field between the gate and anode, which sits just below the top PMT array within a tightly controlled layer of xenon gas. In the gas, the electrons create another flash of light. A characteristic combination of two light flashes signals the arrival of a WIMP.

    “Establishing the electric field is critical to be able to distinguish between potential dark matter signals and background signals,” said Ryan Linehan, a Stanford University graduate student on SLAC’s LZ team.

    2
    Four high-voltage grids inside LZ’s tank of liquid xenon. The cathode and gate grids create an electric field that pushes electrons through the liquid xenon toward the top of the tank. There, a field between the gate and anode grids extracts the electrons. They enter a thin layer of xenon gas that floats atop the liquid, where they create a flash of light. A fourth grid at the bottom of the xenon tank shields the bottom PMT array from the high fields above. (Greg Stewart/SLAC National Accelerator Laboratory)

    A fourth grid at the bottom of the xenon tank will shield the bottom PMT array from the high electric fields above.

    Weaving a ‘metal fabric’

    To build the grids, LZ engineers and scientists had to solve a number of technical challenges. For instance, the grids can produce the required uniform electric field only if they stay very flat when mounted horizontally inside the xenon tank. They must also be transparent enough so that they don’t stop light from reaching the PMTs. To further complicate things, there are no commercially available grids in the size the LZ team needed, so they had to find a way to build their own.

    The crucial idea came from SLAC mechanical engineer Knut Skarpaas. He designed a loom similar to those used for weaving fabric. But instead of thread, LZ’s loom wove metal wires about the size of a human hair into fine meshes with wires only millimeters apart (see video at the top of this article). And instead of weaving the “fabric” on an ordinary production floor, the loom operated in a clean room to avoid contamination.

    3
    Members of SLAC’s LZ team with the loom they used to weave high-voltage grids for the next-gen dark matter experiment. (Farrin Abbott/SLAC National Accelerator Laboratory)

    Ramping up the voltage

    Once a metal mesh was woven, LZ folks sandwiched it between two metal rings and cut out a circular piece of the right size. Then, they carefully transferred the circular grids one by one to a customized test vessel and checked their performance.

    “Nobody had studied the behavior of such large grids under high fields and in this particular xenon environment before, so there was a lot we had to test and learn,” said Rachel Mannino, a postdoctoral researcher at the University of Wisconsin-Madison working with SLAC’s LZ team. “We were particularly worried about electron emissions from the wires, which can occur under high fields and would generate false signals in the detector.”

    The tests were done in xenon gas under high pressure. While slowly ramping up the voltage on the grids, the researchers used PMTs to search for potential hotspots where electrons leave the metal mesh. The results allowed the team to define grid operating conditions that minimize unwanted electron emissions.

    In addition, the gate grid was chemically treated to further reduce those nuisance emissions and improve the experiment’s ability to search for WIMPs with lower masses.

    4
    A SLAC team sets up a specialized vessel to test the performance of LZ’s high-voltage grids under high voltage and in a high-pressure xenon atmosphere. (Farrin Abbott/SLAC National Accelerator Laboratory)

    Getting ready for the dark matter hunt

    With the last grid on its way to SURF, the LZ team is now ready to put everything together.

    “We’ve recently begun building the detector core from the bottom up,” said SLAC’s Tomasz Biesiadzinski, one of the scientists in charge of detector integration, who splits his time between SLAC and SURF. “In the fall, we’ll move everything underground, where LZ’s outer layers are already being assembled, and integrate and connect all the parts. After all the years of preparation we’re finally getting close to collecting data.”

    LZ’s dark matter hunt is set to begin sometime next year. Then, it’ll be up to the WIMPs to show up.

    5
    LZ’s high-voltage grids are about 5 feet in diameter. Each of the four grids is woven from hundreds of metal wires thinner than a human hair – a total of two miles of wire for all four. (Farrin Abbott/SLAC National Accelerator Laboratory)

    Major support for LZ comes from the DOE Office of Science; South Dakota Science and Technology Authority; the U.K.’s Science & Technology Facilities Council; and from collaboration members in South Korea and Portugal.

    See the full article here .


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

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
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