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  • richardmitnick 3:55 pm on April 17, 2017 Permalink | Reply
    Tags: , , , , , , , SLAC SSRL,   

    From SLAC: “SLAC’s X-ray Laser Glimpses How Electrons Dance with Atomic Nuclei in Materials” 


    SLAC Lab

    September 22, 2016

    Studies Could Help Design and Control Materials with Intriguing Properties, Including Novel Electronics, Solar Cells and Superconductors.

    From hard to malleable, from transparent to opaque, from channeling electricity to blocking it: Materials come in all types. A number of their intriguing properties originate in the way a material’s electrons “dance” with its lattice of atomic nuclei, which is also in constant motion due to vibrations known as phonons.

    This coupling between electrons and phonons determines how efficiently solar cells convert sunlight into electricity. It also plays key roles in superconductors that transfer electricity without losses, topological insulators that conduct electricity only on their surfaces, materials that drastically change their electrical resistance when exposed to a magnetic field, and more.

    At the Department of Energy’s SLAC National Accelerator Laboratory, scientists can study these coupled motions in unprecedented detail with the world’s most powerful X-ray laser, the Linac Coherent Light Source (LCLS). LCLS is a DOE Office of Science User Facility.

    SLAC/LCLS

    1
    An illustration shows how laser light excites electrons (white spheres) in a solid material, creating vibrations in its lattice of atomic nuclei (black and blue spheres). SLAC’s LCLS X-ray laser reveals the ultrafast “dance” between electrons and vibrations that accounts for many important properties of materials. (SLAC National Accelerator Laboratory)

    “It has been a long-standing goal to understand, initiate and control these unusual behaviors,” says LCLS Director Mike Dunne. “With LCLS we are now able to see what happens in these materials and to model complex electron-phonon interactions. This ability is central to the lab’s mission of developing new materials for next-generation electronics and energy solutions.”

    LCLS works like an extraordinary strobe light: Its ultrabright X-rays take snapshots of materials with atomic resolution and capture motions as fast as a few femtoseconds, or millionths of a billionth of a second. For comparison, one femtosecond is to a second what seven minutes is to the age of the universe.

    Two recent studies made use of these capabilities to study electron-phonon interactions in lead telluride, a material that excels at converting heat into electricity, and chromium, which at low temperatures has peculiar properties similar to those of high-temperature superconductors.

    Turning Heat into Electricity and Vice Versa

    Lead telluride, a compound of the chemical elements lead and tellurium, is of interest because it is a good thermoelectric: It generates an electrical voltage when two opposite sides of the material have different temperatures.

    “This property is used to power NASA space missions like the Mars rover Curiosity and to convert waste heat into electricity in high-end cars,” says Mariano Trigo, a staff scientist at the Stanford PULSE Institute and the Stanford Institute for Materials and Energy Sciences (SIMES), both joint institutes of Stanford University and SLAC. “The effect also works in the opposite direction: An electrical voltage applied across the material creates a temperature difference, which can be exploited in thermoelectric cooling devices.”

    Mason Jiang, a recent graduate student at Stanford, PULSE and SIMES, says, “Lead telluride is exceptionally good at this. It has two important qualities: It’s a bad thermal conductor, so it keeps heat from flowing from one side to the other, and it’s also a good electrical conductor, so it can turn the temperature difference into an electric current. The coupling between lattice vibrations, caused by heat, and electron motions is therefore very important in this system. With our study at LCLS, we wanted to understand what’s naturally going on in this material.”

    In their experiment, the researchers excited electrons in a lead telluride sample with a brief pulse of infrared laser light, and then used LCLS’s X-rays to determine how this burst of energy stimulated lattice vibrations.

    2
    This illustration shows the arrangement of lead and tellurium atoms in lead telluride, an excellent thermoelectric that efficiently converts heat into electricity and vice versa. In its normal state (left), lead telluride’s structure is distorted and has a relatively large degree of lattice vibrations (blurring). When scientists hit the sample with a laser pulse, the structure became more ordered (right). The results elucidate how electrons couple with these distortions – an interaction that is crucial for lead telluride’s thermoelectric properties. (SLAC National Accelerator Laboratory)

    “Lead telluride sits at the precipice of a coupled electronic and structural transformation,” says principal investigator David Reis from PULSE, SIMES and Stanford. “It has a tendency to distort without fully transforming – an instability that is thought to play an important role in its thermoelectric behavior. With our method we can study the forces involved and literally watch them change in response to the infrared laser pulse.”

    The scientists found that the light pulse excites particular electronic states that are responsible for this instability through electron-phonon coupling. The excited electrons stabilize the material by weakening certain long-range forces that were previously associated with the material’s low thermal conductivity.

    “The light pulse actually walks the material back from the brink of instability, making it a worse thermoelectric,” Reis says. “This implies that the reverse is also true – that stronger long-range forces lead to better thermoelectric behavior.”

    The researchers hope their results, published July 22 in Nature Communications, will help them find other thermoelectric materials that are more abundant and less toxic than lead telluride.

    Controlling Materials by Stimulating Charged Waves

    The second study looked at charge density waves – alternating areas of high and low electron density across the nuclear lattice – that occur in materials that abruptly change their behavior at a certain threshold. This includes transitions from insulator to conductor, normal conductor to superconductor, and from one magnetic state to another.

    These waves don’t actually travel through the material; they are stationary, like icy waves near the shoreline of a frozen lake.

    “Charge density waves have been observed in a number of interesting materials, and establishing their connection to material properties is a very hot research topic,” says Andrej Singer, a postdoctoral fellow in Oleg Shpyrko’s lab at the University of California, San Diego. “We’ve now shown that there is a way to enhance charge density waves in crystals of chromium using laser light, and this method could potentially also be used to tweak the properties of other materials.”

    This could mean, for example, that scientists might be able to switch a material from a normal conductor to a superconductor with a single flash of light. Singer and his colleagues reported their results on July 25 in Physical Review Letters.

    The research team used the chemical element chromium as a simple model system to study charge density waves, which form when the crystal is cooled to about minus 280 degrees Fahrenheit. They stimulated the chilled crystal with pulses of optical laser light and then used LCLS X-ray pulses to observe how this stimulation changed the amplitude, or height, of the charge density waves.

    “We found that the amplitude increased by up to 30 percent immediately after the laser pulse,” Singer says. “The amplitude then oscillated, becoming smaller and larger over a period of 450 femtoseconds, and it kept going when we kept hitting the sample with laser pulses. LCLS provides unique opportunities to study such process because it allows us to take ultrafast movies of the related structural changes in the lattice.”

    Based on their results, the researchers suggested a mechanism for the amplitude enhancement: The light pulse interrupts the electron-phonon interactions in the material, causing the lattice to vibrate. Shortly after the pulse, these interactions form again, which boosts the amplitude of the vibrations, like a pendulum that swings farther out when it receives an extra push.

    A Bright Future for Studies of the Electron-Phonon Dance

    Studies like these have a high priority in solid-state physics and materials science because they could pave the way for new materials and provide new ways to control material properties.

    With its 120 ultrabright X-ray pulses per second, LCLS reveals the electron-phonon dance with unprecedented detail. More breakthroughs in the field are on the horizon with LCLS-II – a next-generation X-ray laser under construction at SLAC that will fire up to a million X-ray flashes per second and will be 10,000 times brighter than LCLS.

    “LCLS-II will drastically increase our chances of capturing these processes,” Dunne says. “Since it will also reveal subtle electron-phonon signals with much higher resolution, we’ll be able to study these interactions in much greater detail than we can now.”

    Other research institutions involved in the studies were University College Cork, Ireland; Imperial College London, UK; Duke University; Oak Ridge National Laboratory; RIKEN Spring-8 Center, Japan; University of Tokyo, Japan; University of Michigan; and University of Kiel, Germany. Funding sources included DOE Office of Science; Science Foundation Ireland; Volkswagen Foundation, Germany; and Federal Ministry of Education and Research, Germany. Preliminary X-ray studies on lead telluride were performed at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility, and at the Spring-8 Angstrom Compact Free-electron Laser (SACLA), Japan.

    SLAC/SSRL

    SACLA Free-Electron Laser Riken Japan


    his movie introduces LCLS-II, a future light source at SLAC. It will generate over 8,000 times more light pulses per second than today’s most powerful X-ray laser, LCLS, and produce an almost continuous X-ray beam that on average will be 10,000 times brighter. (SLAC National Accelerator Laboratory)

    See the full article here .

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    SLAC Campus
    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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  • richardmitnick 2:45 pm on February 23, 2017 Permalink | Reply
    Tags: , , Instrument finds new earthly purpose, , , SLAC SSRL, Spectrometry, ,   

    From Symmetry: “Instrument finds new earthly purpose” 

    Symmetry Mag

    Symmetry

    02/23/17
    Amanda Solliday

    1
    Nordlund and his colleagues—Sangjun Lee, a SLAC postdoctoral research fellow, and Jamie Titus, a Stanford University doctoral student (pictured above at SSRL, from left: Lee, Titus and Nordlund)—have already used the transition-edge-sensor spectrometer at SSRL to probe for nitrogen impurities in nanodiamonds and graphene, as well as closely examine the metal centers of proteins and bioenzymes, such as hemoglobin and photosystem II. The project at SLAC was developed with 
support by the Department of Energy’s Laboratory Directed Research and Development.
    Andy Freeberg, SLAC National Accelerator Laboratory

    Detectors long used to look at the cosmos are now part of X-ray experiments here on Earth.

    Modern cosmology experiments—such as the BICEP instruments and the in Antarctica—rely on superconducting photon detectors to capture signals from the early universe.

    BICEP 3 at the South Pole
    BICEP 3 at the South Pole

    Keck Array
    Keck Array at the South Pole

    These detectors, called transition edge sensors, are kept at temperatures near absolute zero, at only tenths of a Kelvin. At this temperature, the “transition” between superconducting and normal states, the sensors function like an extremely sensitive thermometer. They are able to detect heat from cosmic microwave background radiation, the glow emitted after the Big Bang, which is only slightly warmer at around 3 Kelvin.

    Scientists also have been experimenting with these same detectors to catch a different form of light, says Dan Swetz, a scientist at the National Institute of Standards and Technology. These sensors also happen to work quite well as extremely sensitive X-ray detectors.

    NIST scientists, including Swetz, design and build the thin, superconducting sensors and turn them into pixelated arrays smaller than a penny. They construct an entire X-ray spectrometer system around those arrays, including a cryocooler, a refrigerator that can keep the detectors near absolute zero temperatures.

    2

    TES array and cover shown with penny coin for scale.
    Dan Schmidt, NIST

    Over the past several years, these X-ray spectrometers built at the NIST Boulder MicroFabrication Facility have been installed at three synchrotrons at US Department of Energy national laboratories: the National Synchrotron Light Source at Brookhaven National Laboratory, the Advanced Photon Source [APS] at Argonne National Laboratory and most recently at the Stanford Synchrotron Radiation Lightsource [SSRL] at SLAC National Accelerator Laboratory.

    BNL NSLS-II Interior
    BNL NSLS-II Interior

    ANL APS interior
    ANL APS interior

    SLAC/SSRL
    SLAC/SSRL

    Organizing the transition edge sensors into arrays made a more powerful detector. The prototype sensor—built in 1995—consisted of only one pixel.

    These early detectors had poor resolution, says physicist Kent Irwin of Stanford University and SLAC. He built the original single-pixel transition edge sensor as a postdoc. Like a camera, the detector can capture greater detail the more pixels it has.

    “It’s only now that we’re hitting hundreds of pixels that it’s really getting useful,” Irwin says. “As you keep increasing the pixel count, the science you can do just keeps multiplying. And you start to do things you didn’t even conceive of being possible before.”

    Each of the 240 pixels is designed to catch a single photon at a time. These detectors are efficient, says Irwin, collecting photons that may be missed with more conventional detectors.

    Spectroscopy experiments at synchrotrons examine subtle features of matter using X-rays. In these types of experiments, an X-ray beam is directed at a sample. Energy from the X-rays temporarily excites the electrons in the sample, and when the electrons return to their lower energy state, they release photons. The photons’ energy is distinctive for a given chemical element and contains detailed information about the electronic structure.

    As the transition edge sensor captures these photons, every individual pixel on the detector functions as a high-energy-resolution spectrometer, able to determine the energy of each photon collected.

    The researchers combine data from all the pixels and make note of the pattern of detected photons across the entire array and each of their energies. This energy spectrum reveals information about the molecule of interest.

    These spectrometers are 100 times more sensitive than standard spectrometers, says Dennis Nordlund, SLAC scientist and leader of the transition edge sensor project at SSRL. This allows a look at biological and chemical details at extremely low concentrations using soft (low-energy) X-rays.

    “These technology advances mean there are many things we can do now with spectroscopy that were previously out of reach,” Nordlund says. “With this type of sensitivity, this is when it gets really interesting for chemistry.”

    The early experiments at Brookhaven looked at bonding and the chemical structure of nitrogen-bearing explosives. With the spectrometer at Argonne, a research team recently took scattering measurements on high-temperature superconducting materials.

    “The instruments are very similar from a technical standpoint—same number of sensors, similar resolution and performance,” Swetz says. “But it’s interesting, the labs are all doing different science with the same basic equipment.”

    At NIST, Swetz says they’re working to pair these detectors with less intense light sources, which could enable researchers to do X-ray experiments in their personal labs.

    There are plans to build transition-edge-sensor spectrometers that will work in the higher energy hard X-ray region, which scientists at Argonne are working on for the next upgrade of Advanced Photon Source.

    To complement this, the SLAC and NIST collaboration is engineering spectrometers that will handle the high repetition rate of X-ray laser pulses such as LCLS-II, the next generation of the free-electron X-ray laser at SLAC. This will require faster readout systems. The goal is to create a transition-edge-sensor array with as many as 10,000 pixels that can capture more than 10,000 pulses per second.

    Irwin points out that the technology developed for synchrotrons, LCLS-II and future cosmic-microwave-background experiments provides shared benefit.

    “The information really keeps bouncing back and forth between X-ray science and cosmology,” Irwin says

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 7:06 am on September 2, 2016 Permalink | Reply
    Tags: , , , Linsey Seitz, SIMES, SLAC SSRL, ,   

    From SLAC: Women in STEM – “SLAC, Stanford Team Finds a Tough New Catalyst for Use in Renewable Fuels Production” Linsey Seitz 


    SLAC Lab

    September 1, 2016

    Discovery Could Make Water-splitting Reaction Cheaper, More Efficient

    Researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have developed a tough new catalyst that carries out a solar-powered reaction 100 times faster than ever before, works better as time goes on and stands up to acid.

    And because it requires less of the rare and costly metal iridium, it could bring down the cost of a process that mimics photosynthesis by using sunlight to split water molecules – a key step in a renewable, sustainable pathway to produce hydrogen or carbon-based fuels that can power a broad range of energy technologies.

    The team published their results today in the journal Science.

    1
    A simulation shows one possible way that a highly active iridium oxide layer could form on the surface of a strontium iridium oxide catalyst. Experiments by SLAC and Stanford researchers showed that strontium atoms (green spheres) left the top layer through a corrosion process during the catalyst’s first two hours of operation. The top layer then rearranged itself and became much better at accelerating chemical reactions. Follow-up X-ray studies at SLAC will examine these surface changes in more detail. (C.F. Dickens/Stanford University)

    A Multi-pronged Search

    The discovery of the catalyst – a very thin film of iridium oxide layered on top of strontium iridium oxide – was the result of an extensive search by three groups of experts for a more efficient way to accelerate the oxygen evolution reaction, or OER, which is half of a two-step process for splitting water with sunlight.

    “The OER has been a real bottleneck, particularly in acidic conditions,” said Thomas Jaramillo, an associate professor at SLAC and Stanford and deputy director of the SUNCAT Center for Interface Science and Catalysis. “The only reasonably active catalysts we know that can survive those harsh conditions are based on iridium, which is one of the rarest metals on Earth. If we want to bring down the cost of such a pathway for making fuels from renewable sources and carry it out on a much larger scale, we need to develop catalyst materials that are more active and that use little or no iridium.”

    The search started with SUNCAT theorists, who used computers to explore a database of materials and find the ones with the most potential to do exactly what was needed. Catalysts accelerate chemical reactions without being used up in the process, and databases like this one have become an important tool for designing catalysts to order, rather than testing thousands of materials in a time-consuming, trial-and-error approach.

    Based on the results, a team led by SLAC Staff Scientist Yasuyuki Hikita and SLAC/Stanford Professor Harold Hwang, both investigators with the Stanford Institute for Materials and Energy Sciences (SIMES), synthesized one of the catalyst candidates, strontium iridium oxide. Linsey Seitz, a PhD student in Jaramillo’s group and first author of the report, investigated the material’s properties.

    2
    Stanford PhD student Linsey Seitz investigated the properties of a tough new catalyst material that carries out a key water-splitting reaction in acid. She is now a Helmholtz postdoctoral fellow at the Karlsruhe Institute of Technology in Germany. (Jesse D. Benck/Stanford University)

    3
    Sample of a new catalyst material created by SLAC and Stanford researchers. It’s 100 times better than previous catalysts at accelerating the oxygen-evolving reaction in acid, a key step in a pathway for making sustainable fuels. (Linsey Seitz/Stanford University)

    4
    Images made with an atomic force microscope show variations in the height of the catalyst’s surface before (left) and after its first 30 hours of operation. The observed changes in surface texture reflect strontium atoms leaving the top layers of the material during operation, forming a very catalytically active thin film of iridium oxide. (L. Seitz et. al., Science)

    A Surprising Improvement

    To the team’s surprise, this catalyst worked even better than expected, and kept improving over the first two hours of operation. Experiments probing the surface of the material indicated that a corrosion process released strontium atoms into the surrounding fluid during this initial period. This left a film of iridium oxide just a few atomic layers thick that was much more active than the original material, and 100 times more efficient at promoting the OER than any other acid-stable catalyst known to date.

    “A lot of materials do this type of thing – surfaces can be very dynamic, changing during the course of a reaction – but in this case the catalyst changes in a way that gives you excellent performance in acid,” Jaramillo said. “This is unusual, because under these conditions most materials are either poor catalysts or they completely fall apart, or both.”

    The researchers still don’t know exactly why this surface layer is so active, although the theorists, including SUNCAT graduate students Colin Dickens and Charlotte Kirk, have provided some ideas. Jaramillo’s group will be taking a closer look at the catalyst with X-ray beams at SLAC’s Stanford Synchrotron Radiation Lightsource, a DOE Office of Science User Facility, to determine exactly how the atoms on the surface rearrange themselves and why this boosts the catalyst’s performance.

    SLAC SSRL Tunnel
    SLAC SSRL

    “To make a commercially viable catalyst we will need to reduce the amount of iridium in the material even more,” said Jens Nørskov, director of SUNCAT and a professor at SLAC and Stanford. “But there are many possibilities, and this gives us some very good leads.”

    SUNCAT and SIMES are joint institutes of Stanford and SLAC. Major funding for the project came from the DOE Office of Science.

    See the full article here .

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    SLAC Campus
    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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  • richardmitnick 12:28 pm on August 30, 2016 Permalink | Reply
    Tags: A Virtual Flight Through a Catalyst Particle Finds Evidence of Poisoning, , Fluid catalytic cracking (FCC), SLAC SSRL   

    From SLAC: “A Virtual Flight Through a Catalyst Particle Finds Evidence of Poisoning” 


    SLAC Lab

    August 30, 2016

    At SLAC Synchrotron, Two X-ray Techniques Give a 3-D View of Why Catalysts Used in Gasoline Production Go Bad
    August 30, 2016


    This visualization of the experimental data shows how scientists mapped the distribution of chemical elements in a single fluid catalytic cracking (FCC) particle and merged it with structural information about the pore networks. Because of the high resolution at which they mapped the catalyst, they were able to look deep into the pores and learn more about the metal poisoning reaction. The changing colors of the “fog” inside the pores reflect the changing chemistry. (SLAC National Accelerator Laboratory)

    Merging two powerful 3-D X-ray techniques, a team of researchers from the Department of Energy’s SLAC National Accelerator Laboratory and Utrecht University in the Netherlands revealed new details of a process known as metal poisoning that clogs the pores of catalyst particles used in gasoline production, causing them to lose effectiveness.

    The team combined their data to produce a video that shows the chemistry of this aging process and takes the viewer on a virtual flight through the pores of a catalyst particle. The results were published today in Nature Communications.

    1
    This illustration depicts concentrations of chemical elements at five different points in a catalyst pore channel. The zigzag represents the pore channel, which was reconstructed from X-ray microscopy imaging. The colors show the chemical composition, detected with X-ray fluorescence. This information was combined in a model that simulates the aging of the catalyst pore network. (SLAC National Accelerator Laboratory)

    The particles, known as fluid catalytic cracking or FCC particles, are used in oil refineries to “crack” large molecules that are left after distillation of crude oil into smaller molecules, such as gasoline. Those oil molecules flow through the catalyst particles in tiny pores and passageways, which ensure accessibility to the active domains where chemical reactions can take place. But while the catalyst material is not consumed in the reaction and in theory could be recycled indefinitely, the pores clog up and the particles slowly lose effectiveness. Worldwide, about 400 reactor systems refine oil into gasoline, accounting for about 40 to 50 percent of today’s gasoline production, and each system requires 10 to 40 tons of fresh FCC catalysts daily.

    Finding new clues about how FCCs age out could be key to improving gasoline production. But the new technique also has potential for understanding the workings of materials for powering cars of the future, according to Yijin Liu, a lead author on the paper and staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility.

    SLAC SSRL Tunnel
    SLAC SSRL

    “The model we created by combining these two imaging methods can readily be applied to studies of rapid changes in the pore networks of similarly structured materials, such as batteries, fuel cells and underground geological formations,” he said.

    Two Perspectives Complete the Picture

    To design materials for tomorrow’s energy solutions, scientists must understand how they work at multiple scales invisible to the human eye.

    In a previous study at SSRL, the team took a series of two-dimensional images of catalyst particles at various angles and used software they developed to combine them into three-dimensional images of whole particles showing the distribution of elements in catalysts at various ages.

    For the new study, the researchers examined an FCC particle recovered from a refinery using two different 3-D X-ray imaging techniques at two experimental stations, or beamlines, at SSRL.

    One technique, called X-ray fluorescence, provided a detailed profile of the particle’s chemical elements. The other, X-ray transmission microscopy, captured the nanoscale structure of the particle, including fine details about the porous network where metal poisoning can best be observed.

    “The high-resolution microscopy data provided a map of the pores, and the high sensitivity of X-ray fluorescence showed us where metals in the refining fluids were poisoning the catalyst, which appeared as a colored fog in our visualization,” Liu said.

    The results of the study highlight the importance of having multiple techniques to study a single sample at a facility like SSRL. “There was a lot of development on the beamlines to make it possible to register the data in 3-D at this very fine scale,” Liu said. He heads up one of the two beamlines used in the research, which allows him to understand the strength and the limitations of both imaging methods.

    “Understanding catalyst performance requires interrogating catalyst function from multiple perspectives,” SSRL Director Kelly Gaffney said. “The results of this exciting research effort highlight the value of integrating disparate X-ray imaging methods to build a deeper understanding of materials function.”

    A Model for Understanding Material Dynamics

    Going beyond the observation of the experimental data visualized in the video, the scientists developed a model explaining how the accumulation of metals poisons the efficiency of the catalyst.

    “We used an analogy between electrical resistance and the degree of pore blockage, between two points in the particle using the new combined data. We then applied formulas well-known in electrical engineering to explain accessibility through the pore network, but also how it changes when metals are blocking pores,” said the study’s co-lead researcher Florian Meirer, assistant professor of inorganic chemistry and catalysis at Utrecht University.

    The resulting model simulates the aging of the catalyst, allows scientists to quantify this virtual aging, and helps them predict the collapse of its transportation network.

    “The model explains for the first time how this happens in a connective manner, which is a big step toward improving the design of such catalysts. Furthermore, this novel approach can be applied to a broad range of other materials that involve the transport of fluids or gases, such as battery electrodes,” said Bert Weckhuysen, professor of inorganic chemistry and catalysis at Utrecht University.

    Other researchers who contributed to this work were SSRL’s Courtney Krest and Samuel Webb. This work was supported by the NWO Gravitation program, Netherlands Center for Multiscale Catalytic Energy Conversion, and a European Research Council Advanced Grant.

    See the full article here .

    Please help promote STEM in your local schools.

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    SLAC Campus
    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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  • richardmitnick 9:31 am on July 29, 2016 Permalink | Reply
    Tags: , Scientists Create Plasma-Printed Sensors to Monitor Astronaut Health on Long Space Trips, SLAC SSRL   

    From SLAC: “SLAC X-ray Studies Help NASA Develop Printable Electronics for Mars Mission” 


    SLAC Lab

    July 28, 2016

    Scientists Create Plasma-Printed Sensors to Monitor Astronaut Health on Long Space Trips.

    1
    The plasma jet printer consists of a glass nozzle with two copper electrodes connected to a power supply. (Universities Space Research Association at NASA Ames Research Center)

    Plans begin decades in advance for a tremendous effort such as the first manned mission to Mars. The details are as fine – and essential – as how astronauts will breathe and eat and track their health.

    “There’s no doubt that the transportation is taken care of. The spacecraft will be developed,” says Ram Gandhiraman, a scientist with Universities Space Research Association at NASA Ames Research Center. “But how are you going to sustain astronauts for one year or more? Equipment wears out, and supplies need replenished. This is work that also needs to be done.”

    To help prepare for the endeavor, Gandhiraman is creating a tool that will allow astronauts to craft materials in space using a jet of plasma – an energized gas of free electrons and ions. (Plasma is the fourth state of matter, joining the more familiar solid, liquid and gas.)

    The plasma jet can spray tiny semiconductor particles onto cheap, flexible surfaces, such as paper or cloth, and form wearable electronic circuits. Astronauts can use these sensors to track their health and also the environment. The sensors contain small semiconductors tailored to detect biomolecules, such as dopamine and serotonin, as well as gases like ammonia in the environment.

    The NASA team brings the sensors to SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility, to look at the fine details of the sensors’ surfaces.

    SLAC/SSRL
    SLAC/SSRL

    This characterization allows them to optimize the process for printing sensors with the same quality every time.

    Developing the Printer

    The scientists need to be able to tailor the materials traveling through the plasma and control how they deposit on a surface. Even small defects can make the sensors nonfunctional.

    “This is where X-ray spectroscopy is crucial,” Gandhiraman says.

    Every other month or so, Gandhiraman and his team would analyze sensors at SSRL. While developing the plasma printer, Ram worked closely with SLAC scientist Dennis Nordlund to characterize the newly printed sensors.

    Nordlund would examine the plasma-deposited sensors using X-ray absorption spectroscopy and X-ray photoelectron spectroscopy.

    “These techniques allow us to see what chemical groups are present at the surface of the fabricated sensors,” Nordlund says. “This allows us to extract information about the material on an element-by-element basis, including the part of the chemical structure responsible for reactivity and the content of graphitic carbon – an important form of carbon that conducts well – present in the samples.”

    This helped solve one of Gandhiraman’s major challenges – printing exact copies at such a fine scale.

    “Say we ramp up the voltage or the flow of the plasma jet, then you get different chemistries that result in loss of device performance or sensitivity. What causes the behavior was not clear,” Gandhiraman says. “We needed to go back and forth and do an analysis on materials that we print. We used that information about surface properties to optimize the process here.”

    The plasma-printed nanomaterial forms a dense network of sensor and signal amplification materials better than other printing methods, including screen or aerosol printing. Another advantage: Plasma printing can operate at low temperatures, which means the paper or cloth is not destroyed during the process.

    Plasma Printing in the Lab (and in Space)

    In-space fabrication technology would allow astronauts to create the sensors – which become worn out with use – when the need arises.

    “This printer should be able to use both Martian resources and waste or spent materials to fabricate devices on-demand in space,” Gandhiraman says.

    To make a printer that astronauts can use in space, the researchers needed to engineer the plasma jet with an easy-to-assemble, lightweight set-up. During a demonstration in Gandhiraman’s lab, his research assistant Arlene Lopez turns a valve and gas travels through a plastic tube.

    The gas meets a liquid containing carbon nanotubes, forming a mist that is zapped with electricity flowing between two electrodes. This creates charged plasma.

    The plasma’s excited electrons give off light, and the color depends on the composition of the gas. Today, it’s a blue helium glow.

    In the lab, gas comes from a canister. In space, the Martian atmosphere will provide the needed gas. And instead of plugging into an outlet, solar panels will provide electricity.

    The researchers also had to consider the differences in gravity on Earth and Mars.

    “For space applications, you need to be able to use the printer in micro gravity environment,” Gandhiraman says. “That’s one reason this plasma is very interesting – no matter what environment you have, the electric field will drive the jet through the nozzle.”

    The NASA team plans to collaborate with SLAC to develop even more applications for the versatile plasma jet. The researchers have already shown the jet can be used for sterilizing equipment. Next up – NASA is developing a way to use microbes to recycle metals needed for electronics during long-term missions.

    The plasma jet is being tested to see how well it can print electronics using the metal “bioink” produced by the microbes. SLAC’s X-ray spectroscopy tools will look at the purity of recycled materials and pinpoint any contaminants present. The researchers also plan to look at how the same recycling and printing process might be used here on Earth.

    Citation: R. Gandhiraman et al., Applied Physics Letters, 22 March 2016 DOI: 10.1063/1.4943792; R. Gandhiraman et al., ACS Applied Materials & Interfaces, 25 November 2014 DOI: 10.1021/am5069003

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  • richardmitnick 11:51 am on July 20, 2016 Permalink | Reply
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    From SLAC: “Stanford, SLAC X-ray Studies Could Help Make LIGO Gravitational Wave Detector 10 Times More Sensitive” 


    SLAC Lab

    July 19, 2016

    Scientists from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory are using powerful X-rays to study high-performance mirror coatings that could help make the LIGO gravitational wave observatory 10 times more sensitive to cosmic events that ripple space-time.

    LSC LIGO Scientific Collaboration

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    The current version of the Laser Interferometer Gravitational-Wave Observatory, called Advanced LIGO, was the first experiment to directly observe gravitational waves, which were predicted by Albert Einstein 100 years ago. In September 2015, it detected a signal coming from two black holes, each about 30 times heavier than the sun, which merged into a single black hole 1.3 billion years ago. The experiment picked up a similar second event in December 2015.

    “The detection of gravitational waves will fundamentally change our understanding of the universe in years to come,” says Riccardo Bassiri, a physical science research associate at Stanford’s interdisciplinary Ginzton Laboratory. ”Extremely precise mirrors are the heart of LIGO, and their coatings determine the experiment’s sensitivity, or ability to measure gravitational waves. So improving those coatings will make future generations of the experiment even more powerful.”

    Bassiri has teamed up with Apurva Mehta, a staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), to study the atomic structure of coating materials and develop ideas for better ones. SSRL is a DOE Office of Science User Facility.

    SLAC SSRL Tunnel
    SLAC SSRL

    Since LIGO consists of two nearly identical instruments, located 1,900 miles apart in Hanford, Washington, and Livingston, Louisiana, it can also roughly determine a gravitational wave’s cosmic origin.

    “The effects of gravitational waves on the LIGO detectors are incredibly small, with relative changes in arm length on the order of one thousandth of the diameter of an atomic nucleus,” Bassiri says. “On this scale, random atomic motions in the mirror coatings, known as thermal noise, can obscure signals from gravitational waves.”

    1
    An experimental setup at SSRL used to study mirror coating materials with the grazing-incidence X-ray pair distribution function (GI-XPDF) technique.

    Understanding Thermal Noise

    All materials exhibit thermal noise to some degree, but some are less noisy than others. LIGO’s mirrors, which are among the least noisy in the world, are coated with thin layers of silica and tantala, oxides of the chemical elements silicon and tantalum.

    Previous research has shown that heating tantala to hundreds of degrees Fahrenheit and adding titanium oxide, or titania, to its layers in a process called doping can lower the thermal noise. However, scientists do not know exactly why.

    “At the moment, we’re only beginning to understand how these treatments affect the atomic structure,” Mehta says. “If we were able to get a better grasp of how a material’s properties are linked to its structure, we might be able to design better materials in a more efficient, controlled way instead of searching for them with a trial-and-error approach.”


    In this video, Stanford’s Riccardo Bassiri explains his work at SSRL, which aims to better understand thermal noise in mirror coatings.

    Applications Beyond LIGO

    The researchers are in the process of testing a number of materials to see how various doping percentages and manufacturing procedures change the medium-range order. Their hope is that this will lead to detailed models of the atomic structures and to theories that can predict how tweaking these structures can yield better material properties.

    “Advanced LIGO and the desire to understand the fundamental physics of gravitational waves are the main drivers for this type of research,” Bassiri says. “But it also has the potential for influencing a whole industry that uses amorphous coating materials for a wide range of applications, from precise atomic clocks to high-performance electronics and computing to corrosion-resistant coatings.”

    The research team includes Stanford Professors Robert Byer and Martin Fejer as well as SLAC scientists Badri Shyam, Kevin Stone and Michael Toney. Other institutions involved in this research are the California Institute of Technology; the University of Glasgow, UK; the University of Oxford, UK; and members of the LIGO scientific collaboration. Funding sources include the National Science Foundation and the Science and Technology Facilities Council, UK.

    3
    SLAC’s Apurva Mehta (left) and Stanford’s Riccardo Bassiri discuss their X-ray experiments at SSRL.

    See the full article here .

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  • richardmitnick 7:28 pm on June 8, 2016 Permalink | Reply
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    From Caltech: “Solving Molecular Structures” 

    Caltech Logo

    Caltech

    06/08/2016
    Lori Dajose

    1
    The various steps of the atomic structure determination by X-ray crystallography are shown from left to right: crystals of the green fluorescent protein variant mPlum; a single mPlum crystal X-ray diffraction pattern obtained at Caltech’s Molecular Observatory; the calculated electron density map (blue) interpreted with the the positioning of all mPlum polypeptide chain atoms (shown in ball-and-stick representation); and the entire atomic structure of mPlum shown in ribbon representation. Credit: Hoelz Laboratory/Caltech

    Determining the chemical formula of a protein is fairly straightforward, because all proteins are essentially long chains of molecules called amino acids. Each chain, however, folds into a unique three-dimensional shape that helps produce the characteristic properties and function of the protein. These shapes are more difficult to determine (or “solve”); scientists traditionally do so using a technique called X-ray crystallography, in which X-rays are shot through a crystallized sample and scatter off the atoms in a distinctive pattern.

    This spring, Caltech students had the opportunity to use the technique to solve protein structures themselves in a new course taught by Professor of Chemistry André Hoelz.

    Although the Institute has a long history in the fields of structural biology and X-ray crystallography, the chance to get hands-on experience with the technique is rare at most universities, Caltech included. Indeed, the method is more commonly performed at specialized facilities with high-energy X-ray beam lines, including the Stanford Synchrotron Radiation Laboratory (SSRL).

    SLAC/SSRL
    SLAC/SSRL

    However, in 2007, thanks to a gift from the Gordon and Betty Moore Foundation, Caltech opened the Molecular Observatory—a dedicated, completely automated radiation beam line at SSRL.

    1
    Graeme Card examines the sample mount holder in SSRL’s Molecular Observatory for Structural Molecular Biology at Beamline 12. (Courtesy: SLAC)

    “The Molecular Observatory gives us lots of beam time,” notes Hoelz. “Recently, I also received a grant from the Innovation in Education Fund from the Provost’s Office that was matched by the Division of Chemistry and Chemical Engineering, and this allowed me the opportunity to develop this course and train students in a way not commonly found at universities.”

    In the new course, “Macromolecular Structure Determination with Modern X-ray Crystallography Methods” (BMB/Ch 230), Hoelz’s students have been using the Molecular Observatory and other on-campus crystallization resources to solve the structures of various proteins, in particular, variants of green fluorescent proteins (GFPs)—proteins that exhibit bright green fluorescence under certain wavelengths of light. “These proteins are crucial tools in biology because they can be visualized by fluorescence techniques. It’s important to know their physical structure, because it affects the intensity and wavelength at which the protein fluoresces,” says Anders Knight, a first-year graduate student studying protein engineering with Frances Arnold, the Dick and Barbara Dickinson Professor of Chemical Engineering, Bioengineering and Biochemistry, and one of nine students—including two undergraduates—in the inaugural class.

    During the first few weeks of the course, students determined the proper conditions—the pH levels and the mix of salts and buffer solutions—that are required to get a protein to crystallize. These conditions vary from protein to protein, making it tricky to “grow” perfect single crystals of the proteins. “Most of the ones we are working with have known 3-D structures, and they crystallize relatively easily, so they are a great place to start learning about the technique of X-ray crystallography,” Knight says. “But some of us were also given protein variants that had never been crystallized before.”

    Once the students crystallized their proteins, single crystals were mounted in tiny nylon loops that are attached to small metal bases, frozen in liquid nitrogen, and loaded into pucks that were shipped to SSRL. There, the pucks were loaded into a robotic machine—remotely controllable from Caltech and operated by the students—that placed them, one by one, into a powerful X-ray beam. X-rays are scattered at characteristic angles by the electrons within the crystallized samples, generating a diffraction pattern that can be converted into a so-called electron-density map, which is then used to determine the 3-D location of all of the atoms.

    “The electron density map doesn’t exactly show you what the protein’s structure is,” Knight says. “You do have to correctly interpret the electron density map to determine where the protein’s atoms will go. It’s difficult, but this class is designed to give us practice doing that. Collecting data at SSRL was a great learning experience. It was interesting to be able to accurately mount and position the crystals—each smaller than a millimeter—on the beamline from hundreds of miles away. The data collection went fairly quickly, taking around eight minutes.”

    For their final assignment, students will write a mock journal paper about their methods and the final protein structure. Most of the structures had been determined previously, but one student did solve a previously unknown GFP structure, a bright red fluorescent protein called dTomato.

    “dTomato is a product of directed evolution in protein engineering, created by subjecting its parent, DsRed, through several rounds of random genetic mutations,” says Phong Nguyen, a graduate student in the lab of Doug Rees, Roscoe Gilkey Dickinson Professor of Chemistry and Howard Hughes Medical Institute Investigator, and the student who solved the structure of dTomato in Hoelz’s class. “By solving its structure, we can see how directed evolution—a method developed by Frances Arnold to create new proteins using the principles of evolution—changed the protein from its parent. Specifically, we are able to explain how individual mutations contributed to the structural outcome of the protein and consequently to differing chemical and physical properties from the parent. We all are so excited to solve a new structure and contribute knowledge to the field of GFP protein engineering.”

    “Having the Molecular Observatory at Caltech allows us to train students with very sophisticated technology,” says Hoelz, who is now envisioning a second, related course. “Students would learn recombinant protein expression and purification, directly prior to this course, so they can purify the proteins themselves with cutting-edge technology and then go on to determine their 3D structure by X-ray crystallography,” he says.

    “In my opinion, learning by doing is the best way to master how to determine crystal structures and this new course will solidify the strong roots Caltech has in X-ray crystallography,” Hoelz adds. “Not only will this new course accelerate the otherwise slow learning process for this technique, but it will also allow non-structural biology laboratories on campus to determine crystal structures of their favorite proteins using Molecular Observatory, a unique and spectacular facility at Caltech.”

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 5:46 am on April 21, 2016 Permalink | Reply
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    From Stanford: “Peering deep into materials with ultrafast science” 

    Stanford University Name
    Stanford University

    March 31, 2016 [Just appeared in social media]
    Glenn Roberts Jr.

    1
    New techniques developed at SLAC and Stanford allow scientists to observe changes at the nanoscale that occur in fractions of a second in response to light. This artist’s conception depicts the first step in the photovoltaic response that light produces in lead titanate.

    Laser light exposes the properties of materials used in batteries and electronics

    Creating the batteries or electronics of the future requires understanding materials that are just a few atoms thick and that change their fundamental physical properties in fractions of a second. Cutting-edge facilities at SLAC National Accelerator Laboratory and Stanford University have allowed researchers like Aaron Lindenberg to visualize properties of these nanoscale materials at ultrafast time scales.

    In one experiment, a team led by Lindenberg showed atoms shifting in trillionths of a second to produce a wrinkle in a 3-atom-thick sample of a material that might someday be used in flexible electronics. Another study observed semiconductor crystals — called “quantum dots” because they defy classical physics at the nanoscale — expand and shrink in response to ultrafast pulses of laser light.

    2
    A three-atom-thick material wrinkles in response to a laser pulse. Understanding these dynamic ripples could provide crucial clues for the development of next-generation solar cells, electronics and catalysts.

    Revealing such intriguing properties at the nanoscale gives clues about the fundamental nature of materials and how they perform in applications we rely on for energy or information.

    “Even though some of these materials are completely embedded in everyday technologies, not a lot is understood about how they work,” says Lindenberg, who is an associate professor of materials science and engineering and of photon science. He is also a principal investigator for two SLAC/Stanford joint institutes — Stanford Institute for Materials and Energy Sciences and Stanford PULSE Institute.

    “Part of the reason some phenomena are not well understood is because they happen so fast – in billionths, trillionths or even quadrillionths of a second. For the first time, we have tools that allow us to see these things,” he says.

    Working at the intersection of materials science and engineering, Lindenberg and his team have a particular focus on finding promising materials for next-generation electronics, light-based data storage technologies and energy applications.

    “There are a broad range of new properties that emerge at the nanoscale,” Lindenberg says. “The tiniest samples, with just tens or hundreds of atoms, can have nearly flawless structures that make them ideal test tubes for very fundamental questions about what happens when a material transforms.”

    The team uses different types of laser light at SLAC and Stanford labs to learn how simple tweaks in the size, shape and design of materials can change their basic properties in unexpected ways, which could lead to new applications. Taking advantage of the powerful X-rays at SLAC facilities, including the Linac Coherent Light Source [LCLS] and the Stanford Synchrotron Radiation Lightsource [SSRL] , they explore ultrafast changes in nanoscale samples.

    SLAC/LCLS
    SLAC/LCLS

    SLAC/SSRL
    SLAC/SSRL

    “We are trying to understand how electrons or atoms move in materials, which in turn determines, for example, the efficiency of solar cells and other energy-related materials, and how materials switch between different forms,” he says. “Ultrafast techniques allow you to see these kinds of things in a completely new way.”

    See the full article here .

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    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

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  • richardmitnick 10:21 am on March 15, 2016 Permalink | Reply
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    From SLAC: “X-ray Studies at SLAC and Berkeley Lab Aid Search for Ebola Cure” 


    SLAC Lab

    March 14, 2016
    No writer credit

    Research Reveals Structures That Could Be Key to Preventing Infection

    q
    TPC1 channel that Ebola and related filoviruses use to infect cells.

    In experiments carried out partly at the Department of Energy’s SLAC National Accelerator Laboratory, scientists have determined in atomic detail how a potential drug molecule fits into and blocks a channel in cell membranes that Ebola and related filoviruses need to infect victims’ cells.

    The study by researchers at University of California, San Francisco marks an important step toward finding a cure for Ebola and other diseases that depend on the channel. The results were published March 9 in Nature.

    “There are no effective treatments for filovirus infections in humans,” said UCSF postdoctoral researcher Alex Kintzer, who performed the study with Professor Robert Stroud. “With these new structures, pharmaceutical chemists can now design new candidate drug molecules that would be more efficient and effective in blocking the channel and defeating these viruses.”

    To determine the structures, Kintzer first made crystals containing many copies of the target channel protein, called TPC1, bound to the potential drug molecule, Ned-19.

    The researchers then exposed the crystals to intense X-rays at two DOE Office of Science User Facilities – SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) and the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory.

    SLAC SSRL
    SSRL at SLAC

    LBL ALS interior
    ALS at LBL

    Analyzing the patterns and intensities of the X-rays that diffract from the crystals enables researchers to determine their atomic structures.

    Isolating TPC1 from its complex membrane structure is a difficult process that often results in loosely packed crystals that produce faint diffraction patterns, and finding crystals that diffracted well enough to determine the atomic structure of TPC1 required extensive analysis. SSRL’s Beam Line 12-2 was crucial to the successful analysis of these crystals, because its bright X-rays are particularly well-suited for biomedical diffraction studies, and its pixel-array detector is 1,000 times faster than conventional detectors in logging data.

    “These features of Beam Line 12-2 were especially important in enabling Alex to rapidly analyze the diffraction of his challenging crystals,” said Ana Gonzalez, SSRL’s Macromolecular Crystallography User Support Group leader, who helped Kintzer take full advantage of the beamline’s capabilities.

    Even so, the project involved testing about 6,900 crystals during more than 36 sessions at SSRL and ALS. It took nearly four years to complete, from planning to publication.

    One interesting aspect of this study is that the specific TPC1 sample the researchers used did not come from a human or lab animal. Rather, it was from the cells of a weedy Eurasian annual plant related to broccoli (called mouse-ear cress, or Arabidopsis thaliana) that researchers have used as a model species for studying cell activities and genetics since the mid-1940s. (In 2000, for example, A. thaliana’s genome was the very first plant genome to be sequenced.)

    “It’s common in this field to use well-studied non-human components that have similar genetic sequences, structures and functional properties,” Kintzer said.

    Future research plans include determining the structure of human TPC1 and investigating other molecules that may treat or cure other diseases that exploit that channel’s function.

    “For example, TPC1 function also plays important roles in the progression of diabetes, obesity, fatty liver disease, heart disease and such neurodegenerative disorders as Parkinson’s disease,” Kintzer said. “We hope our work will eventually lead to more effective medicines for treating these diseases as well.”

    The research was supported by the National Institutes of Health (NIH) and the Sandler Foundation. Funding for the SSRL Structural Molecular Biology Program is provided by the DOE Office of Science and the NIH National Institute of General Medical Sciences (NIGMS). The Berkeley Center for Structural Biology is supported by NIGMS and the Howard Hughes Medical Institute.

    Citation: A. Kintzer and R. Stroud, Nature, 9 March 2016 (10.1038/nature17194).

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  • richardmitnick 8:11 am on November 17, 2015 Permalink | Reply
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    From SLAC: “X-ray Microscope Reveals ‘Solitons,’ a Special Type of Magnetic Wave” 


    SLAC Lab

    November 16, 2015

    Scientists Hope to Control its Properties to Create a New Form of Electronics

    1
    X-rays at SSRL (purple) measure a special type of magnetic wave, called a spin wave soliton, that has the ability to hold its shape as it moves across a magnetic material. The arrows, like reorienting compass needles, represent localized changes in the material’s magnetic orientation. (SLAC National Accelerator Laboratory)

    Researchers used a powerful, custom-built X-ray microscope at the Department of Energy’s SLAC National Accelerator Laboratory to directly observe the magnetic version of a soliton, a type of wave that can travel without resistance. Scientists are exploring whether such magnetic waves can be used to carry and store information in a new, more efficient form of computer memory that requires less energy and generates less heat.

    Magnetic solitons are remarkably stable and hold their shape and strength as they travel across a magnetic material, just as tsunamis maintain their strength and form while traversing the ocean. This offers an advantage over materials used in modern electronics, which require more energy to move data due to resistance, which causes them to heat up.

    In experiments at SLAC’s Stanford Synchrotron Radiation Lightsource [SSRL] , a DOE Office of Science User Facility, researchers captured the first X-ray images of solitons and a mini-movie of solitons that were generated by hitting a magnetic material with electric current to excite rippling magnetic effects. Results from two independent experiments were published Nov. 16 in Nature Communications and Sept. 17 in Physical Review Letters.

    SLAC SSRL Tunnel
    SSRL

    “Magnetism has been used for navigation for thousands of years and more recently to build generators, motors and data storage devices,” said co-author Hendrik Ohldag, a scientist at SSRL. “However, magnetic elements were mostly viewed as static and uniform. To push the limits of energy efficiency in the future we need to understand better how magnetic devices behave on fast timescales at the nanoscale, which is why we are using this dedicated ultrafast X-ray microscope.”

    “This is an exciting observation because it shows that small magnetic waves – known as spin-waves – can add up to a large one in a magnet,” explains Andrew Kent, a professor of physics at New York University and a senior author for one of the studies.. “A specialized X-ray method that can focus on particular magnetic elements with very high resolution enabled this discovery and should enable many more insights into this behavior.”

    Solitons are a form of spin waves, which are disturbances that propagate in a magnetic material as a patterned, rippling response in the material’s electrons. This response is related to the spin of electrons, a fundamental particle property that can be thought of as either “up” or “down” – like the head or tail sides of a coin.

    2
    An ultrafast camera coupled to a custom-built X-ray microscope at SLAC’s Stanford Synchrotron Radiation Lightsource allowed researchers to produce a six-frame “movie” of the soliton’s motion. It took about 12 hours to record enough X-ray data to produce the movie. (Stefano Bonetti/Stockholm University)

    In 1834 John Scott Russell, a Scottish civil engineer and shipbuilder, first described his observation of the soliton phenomenon in a boat-produced wave that held a uniform shape for over a mile as it traveled down a canal. Solitons had for decades been theorized to occur in magnets, but it took a specialized X-ray microscope like the one at SLAC to directly observe the effect.

    “We built a microscope that allowed us to look at these magnetic waves in a new way,” said Stefano Bonetti, the leading author of the study published in Nature Communications. Bonetti is a Stanford University postdoctoral fellow now at Stockholm University. “With this new microscope, we can actually see them moving,” he said. “We can see things directly.”

    An ultrafast camera coupled to the microscope allowed researchers to record six images that were compiled in sequence to form a “movie” of the soliton’s motion. It took about 12 hours to record enough X-ray data to produce the movie.

    The high resolution of the X-ray microscope revealed an anomaly in the spin-wave effects: While researchers expected the soliton to fully flip the local magnetic alignment of the material, like a compass switching from north to south, they found that the soliton caused the material’s magnetic orientation to change only slightly.

    “We would expect to see this reverse, or flip,” Bonetti said. “But it didn’t reverse – it just tilted about 25 degrees. The situation is not as simple as people thought.”

    Also, in one of the experiments researchers saw the soliton split in two: it was expected to take a spherical or circular form, but instead appeared split down the middle, as if an approaching ocean wave had split into two separate waves that were mirror images of each other. “In the simulations we were using before, we were blind to this possibility,” Bonetti said.

    More experiments are needed to understand both the tilting effect and the way that the soliton can split into a mirrored form, Bonetti said. Simulations could help researchers learn how to convert the mirrored pattern of the soliton into a more uniformly symmetrical shape, he said, or to understand how to use the split form for data applications.

    Researchers from Stanford University; SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC; University of Barcelona in Spain; KTH Royal Institute of Technology in Sweden; New York University; HGST, a Western Digital Company; and Emory University in Georgia also contributed to the study. The work was supported by Everspin Technologies, the DOE Office of Science, the Knut and Alice Wallenberg Foundation, the Swedish Research Council, the Catalan Government, the National Science Foundation, the Forsk Foundation, the European Commission, the U.S. Army Research Office and Brookhaven National Laboratory.

    Citations: S. Bonetti, et al., Nature Communications, 16 November 2015 (10.1038/NCOMMS9889)

    D. Backes, et al., Physical Review Letters, 17 September 2015 (10.1103/PhysRevLett.115.127205)

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