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  • richardmitnick 9:50 am on April 24, 2019 Permalink | Reply
    Tags: "Capturing the behavior of single-atom catalysts on the move", , , , , X-ray Technology   

    From SLAC National Accelerator Lab: “Capturing the behavior of single-atom catalysts on the move” 

    From SLAC National Accelerator Lab

    April 23, 2019
    Glennda Chui

    1
    A new study precisely controlled the attachment of platinum atoms (white balls) to a titanium dioxide surface (latticework of red and blue balls). It found that their positions varied from being deeply embedded in the surface (lower left) to standing almost free of the surface (upper right). This change in position affected the atoms’ ability to catalyze a chemical reaction that converts carbon monoxide to carbon dioxide (upper right). (Greg Stewart, SLAC National Accelerator Laboratory)

    Scientists are excited by the prospect of stripping catalysts down to single atoms. Attached by the millions to a supporting surface, they could offer the ultimate in speed and specificity.

    Now researchers have taken an important step toward understanding single-atom catalysts by deliberately tweaking how they’re attached to the surfaces that support them – in this case the surfaces of nanoparticles. They attached one platinum atom to each nanoparticle and observed how changing the chemistry of the particle’s surface and the nature of the attachment affected how keen the atom was to catalyze reactions.

    Key experiments for the study took place at the Department of Energy’s SLAC National Accelerator Laboratory, and the results were reported in Nature Materials yesterday.

    “We believe this is the first time the reactivity of a metallic single-atom catalyst has been traced to a specific way of attaching it to a particular supporting structure. This study is also unique in systematically controlling that attachment,” said Simon R. Bare, a distinguished staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) and a co-author of the study.

    SLAC/SSRL

    “This is an important scientific breakthrough, and understanding on a fundamental level how the structure relates to the reactivity will ultimately allow us to design catalysts to be much more efficient. There is a huge number of people working on this problem.”

    Harsh treatment, good results

    Bare and other SLAC scientists were part of a previous study at SSRL [Nature Catalysis] that found that individual iridium atoms could catalyze a particular reaction up to 25 times more efficiently than the iridium nanoparticles used today, which contain 50 to 100 atoms.

    This latest study was led by Associate Professor Phillip Christopher of the University of California, Santa Barbara. It looked at individual atoms of platinum that were attached to separate nanoparticles of titanium dioxide in his lab. While this approach would probably not be practical in a chemical plant or in your car’s catalytic converter, it did give the research team exquisitely fine control of where the atoms were placed and of the environment immediately around them, Bare said.

    Researchers gave the nanoparticles chemical treatments – either harsh or mild – and used SSRL’s X-rays to observe how those treatments changed where and how the platinum atoms attached to the surface.

    Meanwhile, scientists at the University of California, Irvine directly observed the attachments and positions of the platinum atoms with electron microscopes, and researchers at UC-Santa Barbara measured how active the platinum atoms were in catalyzing reactions.

    Breaking through the surface

    A platinum atom has six binding sites where it can hook up with other atoms. In untreated nanoparticles, the atoms were buried in the surface and firmly bound to six oxygen atoms each; they had no free binding sites that could grab other atoms and start a catalytic reaction.

    In mildly treated particles, the platinum atoms emerged from the surface and were bound to just four oxygen atoms apiece, leaving them two free binding sites and the potential for more catalytic activity.

    And in harshly treated particles, the atoms clung to the surface by only two bonds, leaving four binding sites free. When the researchers tested the ability of the variously treated nanoparticles to catalyze a reaction where carbon monoxide combines with oxygen to form carbon dioxide – the same reaction that takes place in a car’s catalytic converter – this one came out on top, Bare said, with five times greater activity than the others.

    “While this study shows the importance of understanding the dynamic nature of catalysts,” Christopher said, “the next challenge will be to translate the findings to industrially relevant systems.”

    SSRL is a DOE Office of Science user facility. The changing positions of the platinum atoms on the particle surfaces were imaged and observed with transmission electron microscopy using state-of-the-art facilities recently established at the Irvine Materials Research Institute (IMRI) at UC-Irvine. Detailed experimental insights obtained in the study were correlated with predictions made by theorists at the University of Milano-Bicocca in Italy.

    See the full article here .


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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 8:29 am on April 23, 2019 Permalink | Reply
    Tags: "A day in the life of a midnight beam master", , , Ben Ripman- operations engineer at the SLAC accelerator control room, , , SLAC SPEAR3, , X-ray Technology   

    From SLAC National Accelerator Lab: “A day in the life of a midnight beam master” 

    From SLAC National Accelerator Lab

    April 16, 2019 [Just today 4.23.19 in social media]
    Angela Anderson

    In SLAC’s accelerator control room, shift lead Ben Ripman and a team of operators fine-tune X-ray beams for science experiments around the clock.

    When is a day not a day? When you work in the central nervous system of the world’s longest linear accelerator, open 24-7.

    “There’s a constant cycle of people coming and going,” says Ben Ripman, an operations engineer at the Department of Energy’s SLAC National Accelerator Laboratory.

    1
    Ben Ripman, operations engineer at the SLAC accelerator control room (Angela Anderson/SLAC National Accelerator Laboratory)

    He might start at 8 a.m., at 4 p.m. or at midnight. But the shift rotations are no barrier to his passion for the job – leading a team of control room operators who deliver brilliant X-ray beams for scientific experiments.

    Control room operators spend most of their workdays (or nights) in a room filled with monitors, three deep and crowded with numbers, charts and graphs. Those displays track the status of thousands of devices and systems in the linear accelerator that runs through a tunnel below Highway 280 and feeds SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS).

    SLAC/LCLS

    The accelerator boosts electrons to almost the speed of light and then wiggles them between magnets to generate X-rays. That X-ray light is formed into pulses and optimized for materials science, biology, chemistry, and physics experiments.

    The entire operation is monitored in the control room, which also serves SPEAR3, the accelerator that produces X-rays for the Stanford Synchrotron Radiation Lightsource (SSRL).

    2
    SLAC SPEAR3

    SLAC/SSRL

    Another set of monitors, staffed by SLAC Facilities, tracks water, compressed air and electricity systems that serve the lab campus.

    Ripman and his fellow operators are experts in reading these digital vital signs. But they are also some of the most knowledgeable people at the lab when it comes to the entire physical machine.

    “We know the accelerator from beginning to end,” he says. “When an operator adjusts something from the control room, they can picture that machine part and what it is doing.”

    For LCLS, they measure the amount of energy in individual X-ray pulses being fed to experimental hutches and often spend hours improving the pulses: tweaking magnets, adjusting the undulators, tuning the shape and length of the electron bunches.

    Some days the control room is quiet, and the operators focus on training and individual projects. On other, more challenging days when the machine is running in exotic modes, they work elbow to elbow with physicists.

    “We love this machine, but the accelerator was built decades ago and can be cantankerous,” Ripman explains. “When things do go wrong, it’s like a game of pickup sticks – one problem triggers another and you need to know how it all fits together.”

    An important part of the job is knowing who to call for help. “We wake up a lot of people in the middle of the night,” Ripman says with a smile.

    Control room operators also make sure everyone who goes into the accelerator tunnel stays safe.

    There are two ways to get into the accelerator. For minor repairs and inspections, people take keys from special key banks that block the accelerator from turning on until all the keys have been returned. On official maintenance days, the doors are thrown open.

    “On those days, maintenance crews, engineers and physicists descend into the tunnel and swarm the machine to resolve as many issues as possible before we have to summon them out again,” Ripman says. “We search the machine to make sure everyone is out before it’s turned back on.”

    Almost all of the displays in the control room were designed by the operators, he says. “We are known to hide ‘Easter eggs’ in them, but you have to get in our good graces to find out about them.”

    New operators take more than a year to get trained and proficient, Ripman says. “People come with a physics degree, but there is not a lot of formal coursework you can take on accelerator operations – it’s a lot of on-the-job training.”

    It was that hands-on learning that drew him to the job in 2010.

    “I was a nerd in high school,” Ripman admits proudly, “Stephen Hawking was my hero.” After studying physics and astronomy in college, Ripman worked as a contractor for NASA before joining SLAC. On his off hours, he plays board games and travels several times a year for card tournaments. He also loves hiking, skiing and snowboarding, and is a member of the Stanford University Singers.

    His favorite thing about the job? “My coworkers,” he says. “I have the privilege of working with smart, fun, quirky people. We all get along quite well, and there’s a great camaraderie.”

    Operators leave sticky notes with jokes or short messages for the next shift and share stories about their days and nights in the accelerator’s brain.

    Like the one about a ghost calling from an abandoned tunnel. But that’s a tale for another night…

    LCLS and SSRL are DOE Office of Science user facilities.

    See the full article here .


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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 7:29 am on March 14, 2019 Permalink | Reply
    Tags: "A new lens on materials under extreme conditions allows researchers to watch shock waves travel through silicon", , Elasticity in silicon shock wave, , X-ray Technology   

    From SLAC National Accelerator Lab: “A new lens on materials under extreme conditions allows researchers to watch shock waves travel through silicon” 

    From SLAC National Accelerator Lab

    March 13, 2019
    Ali Sundermier

    1
    After blasting silicon with intense laser pulses at SLAC’s Linac Coherent Light Source, researchers saw an unexpected shock wave appear in the material before its structure was irreversibly changed. (Gregory Stewart/SLAC National Accelerator Laboratory)

    Elasticity, the ability of an object to bounce back to its original shape, is a universal property in solid materials. But when pushed too far, materials change in unrecoverable ways: Rubber bands snap in half, metal frames bend or melt and phone screens shatter.

    For instance, when silicon, an element abundant in the Earth’s crust, is subjected to extreme heat and pressure, an initial “elastic” shock wave travels through the material, leaving it unchanged, followed by an “inelastic” shock wave that irreversibly transforms the structure of the material.

    Using a new technique, researchers were able to directly watch and image this process. To their surprise, they discovered that it included an extra step that had not been seen before: After the first elastic shock wave traveled through the silicon, a second elastic wave appeared before the final inelastic wave changed the material’s properties.

    Their results were published in Science Advances last week.

    “We discovered that this transformation is more nuanced than previously thought,” says Shaughnessy Brennan Brown, a postdoctoral candidate at Stanford University and graduate research associate at the Department of Energy’s SLAC National Accelerator Laboratory who led the analysis. “We illuminated an entirely new feature potentially observable in other materials.”

    Seeing through a new lens

    In addition to contributing to a deeper understanding of silicon, a material that is important in fields like engineering, geophysics and plasma physics, this new technique lights the path for solving problems in other fields.

    “The platform Shaughnessy developed is also useful in areas like meteoritics,” says co-author Arianna Gleason-Holbrook, a staff scientist at the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC. “Let’s say a large metal impactor, like the remnant core of some planet, hits a terrestrial planet. This technique will allow us to zoom in and spatially walk through the history of that type of shock to answer a number of important questions, like how life gets delivered to a new planet or what happens during asteroid collisions.”

    “It’s almost like you’ve had blurry vision for a while,” she said, “but then you put on glasses and the world opens up. What we’ve done in this paper is provide a new lens on materials properties.”

    Catching the wave

    At SLAC, researchers can see what’s happening deep in the belly of samples by hitting them with ultrafast X-ray laser pulses from the Linac Coherent Light Source (LCLS), and then using the patterns formed by the scattered X-rays to reconstruct images.

    At the Matter in Extreme Conditions (MEC) instrument, researchers blast the samples with intense pulses from a second high-power laser before hitting them with X-rays to watch how materials respond to extreme heat and pressure. In many experiments, researchers position these two lasers nearly parallel to each other. This helps them understand how the material is changing over time but doesn’t give them a clear picture of what these structural transformations actually look like.

    A key feature of the technique used in this paper is that the researchers took advantage of a new laser placement that had been used in previous papers, shooting the pulses from the second laser perpendicular to the X-ray pulses from LCLS. This different vantage point allowed them to watch elusive structural changes to the silicon as they occurred, which is how they imaged the second wave moving through the silicon.

    Wide range of scales

    This new experimental setup also allowed the researchers to magnify what they saw, boosting the resolution of their images and allowing them to get a holistic picture of what was happening to the silicon on a wide range of scales, from the microscopic to the macroscopic.

    To follow up, the researchers will repeat the experiment in much more extreme conditions and apply it to a much broader class of materials to find out if they still see this extra step, which will lead to a better understanding of how materials transform.

    “We’ve been attempting to understand fundamental processes of material transformation without always seeing the whole picture,” Brennan Brown says. “Many scientists use clever techniques to approach the problem from different angles. The beauty of this new platform is its clarity, directness and scope.”

    The team also included researchers from the University of York in England; the University of California, Berkeley; the Deutsches Elektronen-Synchrotron and the University of Hamburg, both in Germany.

    LCLS is a DOE Office of Science user facility. Funding was provided by the DOE Office of Science.

    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 9:27 am on March 12, 2019 Permalink | Reply
    Tags: , , , , SLAC​’s Linac Coherent Light Source X-ray free-electron laser, Ultrafast surface X-ray scattering, X-ray Technology,   

    From Argonne National Laboratory via SLAC: “Ultrathin and ultrafast: scientists pioneer new technique for two-dimensional material analysis” 

    SLAC National Accelerator Lab

    Argonne Lab
    News from From Argonne National Laboratory

    March 11, 2019
    Jared Sagoff

    Discovery allows scientists to look at how 2D materials move with ultrafast precision.

    1
    This image shows the experimental setup for a newly developed technique: ultrafast surface X-ray scattering. This technique couples an optical pump with an X-ray free-electron laser probe to investigate molecular dynamics on the femtosecond time scale. (Image by Haidan Wen.)

    Using a never-before-seen technique, scientists have found a new way to use some of the world’s most powerful X-rays to uncover how atoms move in a single atomic sheet at ultrafast speeds.

    The study, led by researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and in collaboration with other institutions, including the University of Washington and DOE’s SLAC National Accelerator Laboratory, developed a new technique called ultrafast surface X-ray scattering. This technique revealed the changing structure of an atomically thin two-dimensional crystal after it was excited with an optical laser pulse.

    Unlike previous surface X-ray scattering techniques, this new method goes beyond providing a static picture of the atoms on a material’s surface to capture the motions of atoms on timescales as short as trillionths of a second after laser excitation.

    Static surface X-ray scattering and some time-dependent surface X-ray scattering can be performed at a synchrotron X-ray source, but to do ultrafast surface X-ray scattering the researchers needed to use the Linac Coherent Light Source (LCLS) X-ray free-electron laser at SLAC.

    2
    An experimental station at SLAC​’s Linac Coherent Light Source X-ray free-electron laser, where scientists used a new tool they developed to watch atoms move within a single atomic sheet. (Image courtesy of SLAC National Accelerator Laboratory.)

    This light source provides very bright X-rays with extremely short exposures of 50 femtoseconds. By delivering large quantities of photons to the sample quickly, the researchers were able to generate a sufficiently strong time-resolved scattering signal, thus visualizing the motion of atoms in 2D materials.

    “Surface X-ray scattering is challenging enough on its own,” said Argonne X-ray physicist Hua Zhou, an author of the study. ​“Extending it to do ultrafast science in single-layer materials represents a major technological advance that can show us a great deal about how atoms behave at surfaces and at the interfaces between materials.”

    In two-dimensional materials, atoms typically vibrate slightly along all three dimensions under static conditions. However, on ultrafast time scales, a different picture of atomic behavior emerges, said Argonne physicist and study author Haidan Wen.

    Using ultrafast surface X-ray scattering, Wen and postdoctoral researcher I-Cheng Tung led an investigation of a two-dimensional material called tungsten diselenide (WSe2). In this material, each tungsten atom connects to two selenium atoms in a ​“V” shape. When the single-layer material is hit with an optical laser pulse, the energy from the laser causes the atoms to move within the plane of the material, creating a counterintuitive effect.

    “You normally would expect the atoms to move out of the plane, since that’s where the available space is,” Wen said. ​“But here we see them mostly vibrate within the plane right after excitation.”

    These observations were supported by first-principle calculations led by Aiichiro Nakano at University of Southern California and scientist Pierre Darancet of Argonne’s Center for Nanoscale Materials (CNM), a DOE Office of Science User Facility.

    The team obtained preliminary surface X-ray scattering measurements at Argonne’s Advanced Photon Source (APS- below), also a DOE Office of Science User Facility. These measurements, although they were not taken at ultrafast speeds, allowed the researchers to calibrate their approach for the LCLS free-electron laser, Wen said.

    The direction of atomic shifts and the ways in which the lattice changes have important effects on the properties of two-dimensional materials like WSe2, according to University of Washington professor Xiaodong Xu. ​“Because these 2-D materials have rich physical properties, scientists are interested in using them to explore fundamental phenomena as well as potential applications in electronics and photonics,” he said. ​“Visualizing the motion of atoms in single atomic crystals is a true breakthrough and will allow us to understand and tailor material properties for energy relevant technologies.”

    “This study gives us a new way to probe structural distortions in 2-D materials as they evolve, and to understand how they are related to unique properties of these materials that we hope to harness for electronic devices that use, emit or control light,” added Aaron Lindenberg, a professor at SLAC and Stanford University and collaborator on the study. ​“These approaches are also applicable to a broad class of other interesting and poorly understood phenomena that occur at the interfaces between materials.”

    A paper based on the study, ​Anisotropic structural dynamics of monolayer crystals revealed by femtosecond surface X-ray scattering, appeared in the March 11 online edition of Nature Photonics.

    Other authors on the study included researchers from the University of Washington, University of Southern California, Stanford University, SLAC and Kumamoto University (Japan). The APS, CNM, and LCLS are DOE Office of Science User Facilities.

    The research was funded by the DOE’s Office of Science.

    See the full article here .

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit http://science.energy.gov/user-facilities/basic-energy-sciences/.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

     
  • richardmitnick 12:27 pm on March 8, 2019 Permalink | Reply
    Tags: "Scientists Take a Deep Dive Into the Imperfect World of 2D Materials", (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales was used, A form of AFM (atomic force microscopy) was used to view structural details approaching the atomic scale, Adam Schwartzberg: “Now that we know what defects we have and what effect they have on the properties of the material we can use this information to reduce or eliminate defects, , “It’s a very big advance to get this electronic structure on small length scales” said Eli Rotenberg, Because research of WS2 and related 2D materials is still in its infancy there are many unknowns about the roles specific types of defects play in these materials, For this study the defects were due to the sample-growth process, , , Most of the experiments focused on a single flake of tungsten disulfide, NanoARPES which researchers enlisted to probe the 2D samples with X-rays was used in this work, , Researchers from the Berkeley Lab Chemical Sciences Division Aarhus University in Denmark and Montana State University also participated in this study., Researchers hope to control the amount and kinds of atoms that are affected and the locations where these defects are concentrated in the flakes., The defects were largely concentrated around the edges of the flakes a signature of the growth process, The sample used in the study contained microscopic roughly triangular flakes each measuring about 1 to 5 microns (millionths of a meter) across, The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales, The various techniques were applied at the Molecular Foundry where the material was synthesized and at the ALS, The X-rays knocked out electrons in the sample allowing researchers to measure their direction and energy, These 2D materials could also be incorporated in new forms of memory storage and data transfer such as spintronics and valleytronics, They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, This revealed nanoscale defects and how the electrons interact with each other., X-ray Technology   

    From Lawrence Berkeley National Lab: “Scientists Take a Deep Dive Into the Imperfect World of 2D Materials” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 8, 2019

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Berkeley Lab-led team combines several nanoscale techniques to gain new insights on the effects of defects in a well-studied monolayer material.

    1
    This animation displays a scan of arrow-shaped flakes of a 2D material. Samples were scanned across their electron energy, momentum, and horizontal and vertical coordinates using an X-ray-based technique known as nanoARPES at Berkeley Lab’s Advanced Light Source. Red represents the highest intensity measured, followed by orange, yellow, green, and blue, and purple (least intense). (Credit: Roland Koch/Berkeley Lab)

    Nothing is perfect, or so the saying goes, and that’s not always a bad thing. In a study at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), scientists learned how nanoscale defects can enhance the properties of an ultrathin, so-called 2D material.

    They combined a toolbox of techniques to home in on natural, nanoscale defects formed in the manufacture of tiny flakes of a monolayer material known as tungsten disulfide (WS2) and measured their electronic effects in detail not possible before.

    “Usually we say that defects are bad for a material,” said Christoph Kastl, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry and the lead author of the study, published in the journal ACS Nano. “Here they provide functionality.”

    Tungsten disulfide is a well-studied 2D material that, like other 2D materials of its kind, exhibits special properties because of its atomic thinness. It is particularly well-known for its efficiency in absorbing and emitting light, and it is a semiconductor.

    Members of this family of 2D materials could serve as high-efficiency computer transistors and as other electronics components, and they also are prime candidates for use in ultrathin, high-efficiency solar cells and LED lighting, as well as in quantum computers.

    These 2D materials could also be incorporated in new forms of memory storage and data transfer, such as spintronics and valleytronics, that would revolutionize electronics by making use of materials in new ways to make smaller and more efficient devices.

    The latest result marks the first comprehensive study at the Lab’s Advanced Light Source (ALS) involving a technique called nanoARPES, which researchers enlisted to probe the 2D samples with X-rays.

    LBL ALS

    The X-rays knocked out electrons in the sample, allowing researchers to measure their direction and energy. This revealed nanoscale defects and how the electrons interact with each other.

    The nanoARPES capability is housed in an X-ray beamline, launched in 2016, known as MAESTRO (Microscopic and Electronic Structure Observatory). It is one of dozens of specialized beamlines at the ALS, which produces light in different forms – from infrared to X-rays – for a variety of simultaneous experiments.

    “It’s a very big advance to get this electronic structure on small length scales,” said Eli Rotenberg, a senior staff scientist at the ALS who was a driving force in developing MAESTRO and served as one of the study’s leaders. “That matters for real devices.”

    The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales; a form of AFM (atomic force microscopy) to view structural details approaching the atomic scale; and a combined form of optical spectroscopy (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales.

    The various techniques were applied at the Molecular Foundry, where the material was synthesized, and at the ALS.

    LBNL Molecular Foundry

    The sample used in the study contained microscopic, roughly triangular flakes, each measuring about 1 to 5 microns (millionths of a meter) across. They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, and the defects were largely concentrated around the edges of the flakes, a signature of the growth process. Most of the experiments focused on a single flake of tungsten disulfide.

    2
    This image shows an illustration of the atomic structure of a 2D material called tungsten disulfide. Tungsten atoms are shown in blue and sulfur atoms are shown in yellow. The background image, taken by an electron microscope at Berkeley Lab’s Molecular Foundry, shows groupings of flakes of the material (dark gray) grown by a process called chemical vapor deposition on a titanium dioxide layer (light gray). (Credit: Katherine Cochrane/Berkeley Lab)

    Adam Schwartzberg, a staff scientist at the Molecular Foundry who served as a co-lead in the study, said, “It took a combination of multiple types of techniques to pin down what’s really going on.”

    He added, “Now that we know what defects we have and what effect they have on the properties of the material, we can use this information to reduce or eliminate defects – or if you want the defect, it gives us a way of knowing where the defects are,” and provides fresh insight about how to propagate and amplify the defects in the sample-production process.

    While the concentration of edge defects in the WS2 flakes was generally known before the latest study, Schwartzberg said that their effects on materials performance hadn’t previously been studied in such a comprehensive and detailed way.

    Researchers learned that a 10 percent deficiency in sulfur atoms was associated with the defective edge regions of the samples compared to other regions, and they identified a slighter, 3 percent sulfur deficiency toward the center of the flakes. Researchers also noted a change in the electronic structure and higher abundance of freely moving electrical charge-carriers associated with the high-defect edge areas.

    4
    This sequence of images shows a variety of energy intensities (white and yellow) at the edges of a 2D material known as tungsten disulfide, as measured via different techniques: photoluminescense intensity (far left); contact potential difference map (second from left); exciton emission intensity (third from left) – excitons are pairs consistent of an electrons and their quasiparticle counterpart, called a hole; trion emission intensity (far right) – trions are gropus of three charged quasiparticles consistening of either two electrons and a hole or two holes and an electron). (Credit: Christoph Kastl/Berkeley Lab)

    For this study, the defects were due to the sample-growth process. Future nanoARPES studies will focus on samples with defects that are induced through chemical processing or other treatments. Researchers hope to control the amount and kinds of atoms that are affected, and the locations where these defects are concentrated in the flakes.

    Such tiny tweaks could be important for processes like catalysis, which is used to enhance and accelerate many important industrial chemical production processes, and to explore quantum processes that rely on the production of individual particles that serve as information carriers in electronics.

    Because research of WS2 and related 2D materials is still in its infancy, there are many unknowns about the roles specific types of defects play in these materials, and Rotenberg noted that there is a world of possibilities for so-called “defect engineering” in these materials.

    In addition, MAESTRO’s nanoARPES has the ability to study the electronic structures of stacks of different types of 2D material layers. This can help researchers understand how their properties depend on their physical arrangement, and to explore working devices that incorporate 2D materials.

    “The unprecedented small scale of the measurements – currently approaching 50 nanometers – makes nanoARPES a great discovery tool that will be particularly useful to understand new materials as they are invented,” Rotenberg said.

    MAESTRO is one of the priority beamlines to be upgraded as part of the Lab’s ALS Upgrade (ALS-U) project, a major undertaking that will produce even brighter, more focused beams of light for experiments. “The ALS-U project will further improve the performance of the nanoARPES technique,” Rotenberg said, “making its measurements 10 to 30 times more efficient and significantly improving our ability to reach even shorter length scales.”

    NanoARPES could play an important role in the development of new solar technologies, because it allows researchers to see how nanoscale variations in chemical makeup, number of defects, and other structural features affect the electrons that ultimately govern their performance. These same issues are important for many other complex materials, such as superconductors, magnets, and thermoelectrics – which convert temperature to current and vice versa – so nanoARPES will also be very useful for these as well.

    The Molecular Foundry and ALS are both DOE Office of Science User Facilities.

    Researchers from the Berkeley Lab Chemical Sciences Division, Aarhus University in Denmark, and Montana State University also participated in this study. The work was supported by the U.S. Department of Energy’s Office of Basic Energy Sciences, the DOE Early Career Grant program, Berkeley Lab’s Laboratory Directed Research and Development program, the Villum Foundation, and the German Academic Exchange Service.

    See the full article here .

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    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

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    DOE Seal

     
  • richardmitnick 8:30 pm on February 21, 2019 Permalink | Reply
    Tags: , , , , Molecular ensemble, , , , PtPOP, , , , X-ray Technology   

    From SLAC National Accelerator Lab: “Researchers watch molecules in a light-triggered catalyst ring ‘like an ensemble of bells’’ 

    From SLAC National Accelerator Lab

    February 21, 2019
    Ali Sundermier

    1
    Synchronized molecules
    When photocatalyst molecules absorb light, they start vibrating in a coordinated way, like an ensemble of bells. Capturing this response is a critical step towards understanding how to design molecules for the efficient transformation of light energy to high-value chemicals. (Gregory Stewart/SLAC National Accelerator Laboratory)

    A better understanding of these systems will aid in developing next-generation energy technologies.

    Photocatalysts ­– materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.

    Now an international team has used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.

    The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing “like an ensemble of bells,” says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.

    “If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency,” Haldrup says.

    The results published last week in Physical Review Letters.

    Molecular ensemble

    The platinum-based photocatalyst they studied, called PtPOP, is one of a class of molecules that scissors hydrogen atoms off various hydrocarbon molecules when hit by light, Haldrup says: “It’s a testbed – a playground, if you will – for studying photocatalysis as it happens.”

    At SLAC’S X-ray laser, the Linac Coherent Light Source (LCLS), the researchers used an optical laser to excite the platinum-containing molecules and then used X-rays to see how these molecules changed their structure after absorbing the visible photons.

    SLAC/LCLS

    The extremely short X-ray laser pulses allowed them to watch the structure change, Haldrup says.

    The researchers used a trick to selectively “freeze” some of the molecules in their vibrational motion, and then used the ultrashort X-ray pulses to capture how the entire ensemble of molecules evolved in time after being hit with light. By taking these images at different times they can stitch together the individual frames like a stop-motion movie. This provided them with detailed information about molecules that were not hit by the laser light, offering insight into the ultrafast changes occurring in the molecules when they are at their lowest energy.

    Swimming in harmony

    Even before the light hits the molecules, they are all vibrating but out of sync with one another. Kelly Gaffney, co-author on this paper and director of SLAC’s Stanford Synchrotron Radiation Lightsource, likens this motion to swimmers in a pool, furiously treading water.

    SLAC SSRL Campus


    SLAC/SSRL


    SLAC/SSRL

    When the optical laser hits them, some of the molecules affected by the light begin moving in unison and with greater intensity, switching from that discordant tread to synchronized strokes. Although this phenomenon has been seen before, until now it was difficult to quantify.

    “This research clearly demonstrates the ability of X-rays to quantify how excitation changes the molecules,” Gaffney says. “We can not only say that it’s excited vibrationally, but we can also quantify it and say which atoms are moving and by how much.”

    Predictive chemistry

    To follow up on this study, the researchers are investigating how the structures of PtPOP molecules change when they take part in chemical reactions. They also hope to use the information they gained in this study to directly study how chemical bonds are made and broken in similar molecular systems.

    “We get to investigate the very basics of photochemistry, namely how exciting the electrons in the system leads to some very specific changes in the overall molecular structure,” says Tim Brandt van Driel, a co-author from DTU who is now a scientist at LCLS. “This allows us to study how energy is being stored and released, which is important for understanding processes that are also at the heart of photosynthesis and the visual system.”

    A better understanding of these processes could be key to designing better materials and systems with useful functions.

    “A lot of chemical understanding is rationalized after the fact. It’s not predictive at all,” Gaffney says. “You see it and then you explain why it happened. We’re trying to move the design of useful chemical materials into a more predictive space, and that requires accurate detailed knowledge of what happens in the materials that already work.”

    LCLS and SSRL are DOE Office of Science user facilities. This research was supported by DANSCATT; the Independent Research Fund Denmark; the Icelandic Research Fund; the Villum Foundation; and the AMOS program within the Chemical Sciences, Geosciences and Biosciences Division of the DOE Office of Basic Energy Sciences.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    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.

     
  • richardmitnick 11:26 am on February 20, 2019 Permalink | Reply
    Tags: , , , , MSX-NASA Modulated X-ray Source, NASA NavCube, NASA Set to Demonstrate X-ray Communications in Space, NASA XCOM, , X-ray Technology   

    From NASA Goddard Space Flight Center: “NASA Set to Demonstrate X-ray Communications in Space” 

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    Feb. 19, 2019
    Lori Keesey
    NASA’s Goddard Spaceflight Center

    NASA Modulated X-ray Source, a key component in NASA’s first-ever demonstration of X-ray communication in space

    A new experimental type of deep space communications technology is scheduled to be demonstrated on the International Space Station this spring.

    Currently, NASA relies on radio waves to send information between spacecraft and Earth. Emerging laser communications technology offers higher data rates that let spacecraft transmit more data at a time. This demonstration involves X-ray communications, or XCOM, which offers even more advantages.

    X-rays have much shorter wavelengths than both infrared and radio. This means that, in principle, XCOM can send more data for the same amount of transmission power. The X-rays can broadcast in tighter beams, thus using less energy when communicating over vast distances.

    NASA XCOM

    If successful, the experiment could increase interest in the communications technology, which could permit more efficient gigabits-per-second data rates for deep space missions. Gigabits per second is a data transfer rate equivalent to one billion bits, or simple binary units, per second. These extremely high-speed rates of data transfer are not currently common, but new research projects have pushed computing capability toward this range for some technologies.

    “We’ve waited a long time to demonstrate this capability,” said Jason Mitchell, an engineer at NASA’s Goddard Spaceflight Center in Greenbelt, Maryland, who helped develop the technology demonstration, which relies on a device called the Modulated X-ray Source, or MXS.

    “For some missions, XCOM may be an enabling technology due to the extreme distances where they must operate,” Mitchell said.

    Perhaps more dramatically, at least as far as human spaceflight is concerned, X-rays can pierce the hot plasma sheath that builds up as spacecraft hurdle through Earth’s atmosphere at hypersonic speeds. The plasma acts as a shield, cutting off radio frequency communications with anything outside the vehicle for several seconds — a nail-biting period of time dramatically portrayed in the movie, Apollo 13. No one has ever used X-rays in a communications system, though, so other applications not yet conceived could emerge, Mitchell said.

    “Our goal for the immediate future is finding interested partners to help further develop this technology,” Mitchell said.

    Encoding Digital Bits

    To demonstrate this new communications technology, NASA will use the MXS to generate rapid-fire X-ray pulses. Operated by another Goddard-developed computing and navigation technology called NavCube, MXS will turn on and off many times per second while encoding digital bits for transmission.

    NASA’s NavCube

    From the experimental payload, the MXS device will then send the encoded data via the modulated X-rays to detectors on the Neutron-star Interior Composition Explorer, or NICER, which is located 165 feet away — about the width of a football field — on the space station. In this way, NICER becomes the receiver of a one-way X-ray signal.

    NASA NICER on the ISS


    NASA/NICER on the ISS

    3
    NASA’s first-ever demonstration of X-ray communication will occur on the International Space Station. This image shows the locations of the Modulated X-ray Source and the Neutron star Interior Composition Explorer, or NICER, which are critical to the demonstration. Credits: NASA

    Although the first XCOM test will involve the transmission of GPS-like signals, Mitchell said the team may attempt to transmit something more complicated after the initial attempt.

    “It’s important is that we transmit a known code we can identify to make sure NICER receives the signal precisely the way we sent it,” Mitchell said.

    Although primarily built to gather data about the densest objects in the universe — neutron stars and their pulsating next-of-kin, known as pulsars — NICER was also designed to demonstrate advanced technology. In addition to the XCOM demonstration, the mission proved the effectiveness of X-ray navigation in space, showing in 2017 that pulsars could be used as timing sources for navigational purposes.

    During that two-day demonstration, which the NICER team carried out with an experiment called Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, the mission gathered 78 measurements from four millisecond pulsars. The team fed that data into onboard algorithms to autonomously stitch together a navigational solution that revealed the location of NICER in its orbit around Earth as a space station payload. Within eight hours of starting the experiment, the system converged on a location within the targeted 6.2 miles and remained well below that threshold for the rest of the experiment.

    NICER’s ability to carry out science and demonstrate emerging, revolutionary technologies has captured the attention of those planning NASA’s next era of human spaceflight. Missions that perform multiple functions are now considered a model, said Jake Bleacher, lead exploration scientist responsible for identifying areas where Goddard scientists can support human exploration of the Moon and Mars.

    Technology Heritage

    The idea to use X-rays to communicate and navigate originated more than a decade ago when NICER Principal Investigator Keith Gendreau began work on enabling technologies for a proposed black hole imager aimed at directly imaging the event horizon of a supermassive black hole or the point of no return where nothing — neither particles nor photons — can escape.

    The idea was to establish a constellation of precisely aligned spacecraft that would in essence create an X-ray interferometer, an instrument used to measure displacements in objects. He conceived the idea of using X-ray sources as beacons to enable highly precise relative navigation. Using research and development funding, he developed the MXS.

    Gendreau then reasoned that if he could modulate X-rays through a modulator, he could also communicate, thus giving birth to the NICER three-in-one mission concept.

    The XCOM demonstration is managed by NASA’s Space Communications and Navigation program within the Human Exploration and Operations Mission Directorate. NICER is an Astrophysics Mission of Opportunity within the Explorers program. The Space Technology Mission Directorate supports the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.

    For more Goddard technology news, go to: https://www.nasa.gov/sites/default/files/atoms/files/winter_2019_final_web_version.pdf

    For more on SCaN’s advanced communications and navigation technology program, go to: http://nasa.gov/scan

    See the full article here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 10:01 am on February 7, 2019 Permalink | Reply
    Tags: , , , , , , , Silicon pore optics, X-ray Technology   

    From European Space Agency: “X-ray eye of Athena” 

    ESA Space For Europe Banner

    From European Space Agency

    ESA Athena mirror module


    ESA/cosine Research

    This ‘mirror module’ – formed of 140 industrial silicon mirror plates, stacked together by a sophisticated robotic system – is destined to form part of the optical system of ESA’s Athena X-ray observatory.

    ESA/Athena spacecraft depiction

    Due to launch in 2031, Athena will probe 10 to 100 times deeper into the cosmos than previous X-ray missions, to observe the very hottest, high-energy celestial objects. To achieve this the mission requires entirely new X-ray optics technology.

    Energetic X-rays don’t behave like typical light waves: they don’t reflect in a standard mirror. Instead they can only be reflected at shallow angles, like stones skimming along water. So multiple mirrors must be stacked together to focus them: ESA’s 1999-launched XMM-Newton has three sets of 58 gold-plated nickel mirrors, each nestled inside one another. But to see further, Athena needs tens of thousands of densely-packed mirror plates.

    ESA/XMM Newton

    A new technology had to be invented: ‘silicon pore optics’, based on stacking together mirror plates made from industrial silicon wafers, which are normally used to manufacture silicon chips.

    It was developed at ESA’s ESTEC technical centre in the Netherlands, and patented by ESA, invented by an ESA staff member with the founder of cosine Research, the Dutch company leading an European consortium developing Athena’s optics.

    ESA Estec

    The technology was refined through a series of ESA R&D projects, and all process steps have been demonstrated to be suitable for industrial production. The wafers have grooves cut into them, leaving stiffening ribs to form the ‘pores’ the X-rays will pass through. They are given a slight curvature, tapering towards a desired point so the complete flight mirror can focus X-ray images.

    “We’ve produced hundreds of stacks using a trio of automated stacking robot,” explains ESA optics engineer Eric Wille. “Stacking the mirror plates is a crucial step, taking place in a cleanroom environment to avoid any dust contamination, targeting thousandth of a millimetre scale precision. Our angular resolution is continuously improving.”

    “Ongoing shock and other environmental testing ensures the modules will meet Athena’s requirements, and the modules are regularly tested using different X-ray facilities.”

    Athena’s flight mirror – comprising hundreds of these mirror modules – is due for completion three to four years before launch, to allow for its testing and integration.

    Each new ESA Science mission observes the Universe in a different way from the one before it, requiring a steady stream of new technologies years in advance of launch. That’s where ESA’s research and development activities come in, to early anticipate such needs, to make sure the right technology is available at the right time for missions to come.

    Long-term planning is crucial to realise the missions that investigate fundamental science questions, and to ensure the continued development of innovative technology, inspiring new generations of European scientists and engineers.

    See the full article here .


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    Please help promote STEM in your local schools.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 11:19 am on January 15, 2019 Permalink | Reply
    Tags: An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon, , , , , , X-ray Technology   

    From SLAC National Accelerator Lab: “An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon” 

    From SLAC National Accelerator Lab

    January 14, 2019
    Ali Sundermier

    1
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

    2
    Researchers from ETH Zürich in Switzerland used LCLS to show a link between ultrafast demagnetization and an effect that Einstein helped discover 100 years ago. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Using an X-ray laser, researchers watched atoms rotate on the surface of a material that was demagnetized in millionths of a billionth of a second.

    More than 100 years ago, Albert Einstein and Wander Johannes de Haas discovered that when they used a magnetic field to flip the magnetic state of an iron bar dangling from a thread, the bar began to rotate.

    Now experiments at the Department of Energy’s SLAC National Accelerator Laboratory have seen for the first time what happens when magnetic materials are demagnetized at ultrafast speeds of millionths of a billionth of a second: The atoms on the surface of the material move, much like the iron bar did. The work, done at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, was published in Nature earlier this month.

    SLAC/LCLS

    Christian Dornes, a scientist at ETH Zürich in Switzerland and one of the lead authors of the report, says this experiment shows how ultrafast demagnetization goes hand in hand with what’s known as the Einstein-de Haas effect, solving a longstanding mystery in the field.

    “I learned about these phenomena in my classes, but to actually see firsthand that the transfer of angular momentum actually makes something move mechanically is really cool,” Dornes says. “Being able to work on the atomic scale like this and see relatively directly what happens would have been a total dream for the great physicists of a hundred years ago.”

    Spinning sea of skaters

    At the atomic scale, a material owes its magnetism to its electrons. In strong magnets, the magnetism comes from a quantum property of electrons called spin. Although electron spin does not involve a literal rotation of the electron, the electron acts in some ways like a tiny spinning ball of charge. When most of the spins point in the same direction, like a sea of ice skaters pirouetting in unison, the material becomes magnetic.

    When the magnetization of the material is reversed with an external magnetic field, the synchronized dance of the skaters turns into a hectic frenzy, with dancers spinning in every direction. Their net angular momentum, which is a measure of their rotational motion, falls to zero as their spins cancel each other out. Since the material’s angular momentum must be conserved, it’s converted into mechanical rotation, as the Einstein-de Haas experiment demonstrated.

    Twist and shout

    In 1996, researchers discovered that zapping a magnetic material with an intense, super-fast laser pulse demagnetizes it nearly instantaneously, on a femtosecond time scale. It has been a challenge to understand what happens to angular momentum when this occurs.

    In this paper, the researchers used a new technique at LCLS combined with measurements done at ETH Zürich to link these two phenomena. They demonstrated that when a laser pulse initiates ultrafast demagnetization in a thin iron film, the change in angular momentum is quickly converted into an initial kick that leads to mechanical rotation of the atoms on the surface of the sample.

    3
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

    According to Dornes, one important takeaway from this experiment is that even though the effect is only apparent on the surface, it happens throughout the whole sample. As angular momentum is transferred through the material, the atoms in the bulk of the material try to twist but cancel each other out. It’s as if a crowd of people packed onto a train all tried to turn at the same time. Just as only the people on the fringe would have the freedom to move, only the atoms at the surface of the material are able to rotate.

    Scraping the surface

    In their experiment, the researchers blasted the iron film with laser pulses to initiate ultrafast demagnetization, then grazed it with intense X-rays at an angle so shallow that it was nearly parallel to the surface. They used the patterns formed when the X-rays scattered off the film to learn more about where angular momentum goes during this process.

    “Due to the shallow angle of the X-rays, our experiment was incredibly sensitive to movements along the surface of the material,” says Sanghoon Song, one of three SLAC scientists who were involved with the research. “This was key to seeing the mechanical motion.”

    To follow up on these results, the researchers will do further experiments at LCLS with more complicated samples to find out more precisely how quickly and directly the angular momentum escapes into the structure. What they learn will lead to better models of ultrafast demagnetization, which could help in the development of optically controlled devices for data storage.

    Steven Johnson, a scientist and professor at ETH Zürich and the Paul Scherrer Institute in Switzerland who co-led the study, says the group’s expertise in areas outside of magnetism allowed them to approach the problem from a different angle, better positioning them for success.

    “There have been numerous previous attempts by other groups to understand this, but they failed because they didn’t optimize their experiments to look for these tiny effects,” Johnson says. “They were swamped by other much larger effects, such as atomic movement due to laser heat. Our experiment was much more sensitive to the kind of motion that results from the angular momentum transfer.”

    LCLS is a DOE Office of Science user facility. This work was supported by NCCR Molecular Ultrafast Science and Technology, a research instrument of the Swiss National Science Foundation.

    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 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.

     
  • richardmitnick 11:50 am on December 21, 2018 Permalink | Reply
    Tags: , , , , , U.S. Department of Energy (DOE) has approved the technical scope cost estimate and plan of work for an upgrade of the Advanced Photon Source (APS), X-ray Technology   

    From Argonne National Laboratory: “DOE approves technical plan and cost estimate to upgrade Argonne facility; Project will create X-rays that illuminate the atomic scale, in 3D” 

    Argonne Lab
    News from From Argonne National Laboratory

    December 14, 2018

    Upgrade to Advanced Photon Source will open new frontiers in science and help solve pressing problems across industries.

    1
    APS employees work to adjust a magnet that will be used in the APS Upgrade. (Image by Argonne National Laboratory.)

    The U.S. Department of Energy (DOE) has approved the technical scope, cost estimate and plan of work for an upgrade of the Advanced Photon Source (APS), a major storage-ring X-ray source at DOE’s Argonne National Laboratory, Argonne announced on December 14, 2018.

    The resulting facility will allow researchers to view matter at the atomic scale, in three dimensions, opening new frontiers in discovery science, from advances in pharmaceuticals to new materials for better rechargeable batteries.

    The APS, a DOE Office of Science User Facility, produces extremely bright, extremely focused X-rays that can peer through dense materials and illuminate matter at the molecular level. By way of comparison, the X-rays produced at today’s APS are up to one billion times brighter than the X-rays produced in a typical dentist’s office.

    The APS Upgrade project (APS-U) will increase the brightness of these super-bright X-rays another 100 to 1,000 times, depending on the technique used, which will allow scientists to map any atom’s position, identity and dynamics.

    “The APS-U will lead to game-changing research across scientific disciplines,” said Robert Hettel, Director of the APS Upgrade project. ​“The scientific advances from the APS have already made life better for countless Americans and have benefited businesses with new techniques and products. The APS-U will build on this foundation and drive even greater advances.”

    The goal of the $815 million project is to replace the APS accelerator and develop or update X-ray beamlines and other equipment to create a much more powerful X-ray facility. The APS-U will have a new design, a ​“multi-bend achromat” lattice, with many more bending magnets and magnet-focusing cells than the present machine, resulting in much brighter X-ray production.

    “The APS is already one of the crown jewels at Argonne, and the APS Upgrade ensures that this resource will keep its important place in the national laboratory system,” said Paul Kearns, Argonne Laboratory Director. ​“The APS-U is a tremendous example of how cross-disciplinary teams, from Argonne and across the scientific community, come together to solve problems and drive future opportunities.”

    X-rays at the APS are produced by electrons that are accelerated to very high energies, moving at nearly the speed of light as they pass though magnet arrays around a 1.1-kilometer circular storage ring. X-rays are extracted from the storage ring into beamlines, which are equipped with experimental endstations. There, researchers use varying instrumentation to investigate the structure and chemistry of matter in a wide variety of systems across a broad spectrum of time and energy scales.

    Every year, more than 5,500 researchers from across the world conduct experiments at the APS. Studies at the APS have led to two Nobel Prizes, numerous pharmaceutical drugs (including the first drug to treat HIV), improved processes for oil extraction from shale and new insights into additive manufacturing. Scientists at the APS have also studied the composition of an ancient Egyptian mummy and the arms of SUE, the Tyrannosaurus rex specimen at The Field Museum of Chicago.

    The Advanced Photon Source is one of the most powerful X-ray facilities in the world, and the APS-U will ensure that the U.S. keeps this leadership position. New or upgraded facilities similar to the APS are being planned or are under construction in France, Brazil, China, Japan and other countries.

    The APS was commissioned in 1996, at Argonne’s campus, and the APS-U builds on the $1.5 billion of infrastructure that is already in place.

    “We’re grateful to the Department of Energy for moving this important project forward,” said Stephen Streiffer, Director of the APS and Associate Laboratory Director for Photon Sciences at Argonne. ​“This ambitious effort will ensure that the U.S. remains at the forefront of hard X-ray sciences for decades to come.”

    The approval from DOE is formally called Critical Decision 2, or CD-2, and indicates that the project has received baseline approval for its design and implementation. Another critical decision, CD-3, is needed in the future in order for the project to receive full spending authority for the baseline funding approved by CD-2.

    Depending on the Congressional appropriation process, removal of the old storage ring and installation of the new one could begin in 2022. This installation ​“dark time” and subsequent ring commissioning period will last for about one year, after which the APS-U X-ray beamlines will be brought online for researchers.

    See the full article here .

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    Please help promote STEM in your local schools.

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit http://science.energy.gov/user-facilities/basic-energy-sciences/.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

     
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