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  • 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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    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 .


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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.

     
  • 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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    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 1:18 pm on December 8, 2018 Permalink | Reply
    Tags: , , Both new instruments use so-called soft X-rays which have a longer wavelength than hard X-rays, , SCS instrument-new, SQS instrument-new, Two more experiment stations start user operation, X-ray Technology   

    From European XFEL: “Two more experiment stations start user operation” 

    XFEL bloc

    European XFEL

    From European XFEL

    2018/12/07

    Facility doubles experiment capacity.

    Two additional experiment stations—or instruments—have now started operation at European XFEL. The instruments for Small Quantum Systems (SQS) and Spectroscopy and Coherent Scattering (SCS) welcomed their first user groups for experiments last week and this week respectively. With the successful start of operation of the new instruments, European XFEL has now doubled its capacity to conduct research. With the first three groups coming to the new instruments in 2018, the total number of users who will have visited the facility in 2018 will reach over 500.

    1
    Scientists at the SQS instrument. Copyright European XFEL / Jan Hosan

    2
    The SCS instrument at European XFEL. Copyright European XFEL / Jan Hosan

    The two already operational instruments, SPB/SFX and FXE, have been used to examine biomolecules or biological processes and ultrafast reactions respectively since September 2017. In the future, two of the four now operational instruments will be run in parallel in twelve hour shifts. Two more instruments are scheduled to start user operation in the first half of 2019.

    3
    DESY’s Anton Barty (left) and Henry Chapman (right), seen at the SPB/SFX instrument.The SPB/SFX instrument will enable novel studies of structural biology. It is one of two instruments that has been available for users in fall 2017.

    4
    The FXE instrument will enable studies of ultrafast processes, such as the intermediate steps of chemical reactions. The instrument uses the ultrashort pulses of the European XFEL to create sequential images of reacting molecules, producing a slow-motion molecular movie of a previously invisible process. The FXE instrument is one of two instruments that has been available to users in fall 2017.

    “This important milestone gives even more researchers a chance to use the unique properties of our X-ray laser” says Prof. Serguei Molodtsov, Scientific Director at European XFEL. “We made a commitment to the scientific community that the two instruments SCS and SQS would be ready for operation by the end of the year. I am very pleased that we achieved this ambitious goal within time and budget. This has been made possible by the tremendous dedication of our staff and our colleagues from DESY, who operate the European XFEL’s accelerator. We now look forward to seeing the results that scientists from all over the world will achieve with the new instruments!”

    Both new instruments use so-called soft X-rays, which have a longer wavelength than hard X-rays.

    The SQS instrument is designed to study fundamental processes such as what happens when atoms or small molecules absorb many photons simultaneously as well as examining how and when molecular bonds break. SQS can also be used to investigate nanoparticles and biomolecules. The first experiment at SQS involved scientists from several institutes, who were interested in multi-photon processes triggered by the intense X-ray flashes of the European XFEL.

    The SCS instrument is designed to help scientists unravel the electronic and structural properties of a range of materials, including understanding what kind of nanoscale changes happen in magnetic and superconducting materials, and observing what happens during chemical reactions in real-time. The first experiment at the instrument also included scientists from many different institutes and was designed to explore how solid state samples respond to intense X-ray pulses and react under the high pulse rate of the X-ray beam.

    See the full article here .

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    XFEL Campus

    XFEL Tunnel

    XFEL Gun

    The Hamburg area will soon boast a research facility of superlatives: The European XFEL will generate ultrashort X-ray flashes—27 000 times per second and with a brilliance that is a billion times higher than that of the best conventional X-ray radiation sources.

    The outstanding characteristics of the facility are unique worldwide. Started in 2017, it will open up completely new research opportunities for scientists and industrial users.

     
  • richardmitnick 1:57 pm on December 3, 2018 Permalink | Reply
    Tags: , , , X-ray Technology   

    From The Conversation: “Scientist at work: To take atomic-scale pictures of tiny crystals, use a huge, kilometer-long synchrotron” 

    Conversation
    From The Conversation

    ANL Advanced Photon Source

    December 3, 2018
    Kerry Rippy

    It’s 4 a.m., and I’ve been up for about 20 hours straight. A loud alarm is blaring, accompanied by red strobe lights flashing. A stern voice announces, “Searching station B. Exit immediately.” It feels like an emergency, but it’s not. In fact, the alarm has already gone off 60 or 70 times today. It is a warning, letting everyone in the vicinity know I’m about to blast a high-powered X-ray beam into a small room full of electronic equipment and plumes of vaporizing liquid nitrogen.

    In the center of this room, which is called station B, I have placed a crystal no thicker than a human hair on the tip of a tiny glass fiber. I have prepared dozens of these crystals, and am attempting to analyze all of them.

    These crystals are made of organic semiconducting materials, which are used to make computer chips, LED lights, smartphone screens and solar panels. I want to find out precisely where each atom inside the crystals is located, how densely packed they are and how they interact with each other. This information will help me predict how well electricity will flow through them.

    To see these atoms and determine their structure, I need the help of a synchrotron, which is a massive scientific instrument containing a kilometer-long loop of electrons zooming around at near the speed of light. I also need a microscope, a gyroscope, liquid nitrogen, a bit of luck, a gifted colleague and a tricycle.

    Getting the crystal in place

    The first step of this experiment involves placing the super-tiny crystals on the tip of the glass fiber. I use a needle to scrape a pile of them together onto a glass slide and put them under a microscope. The crystals are beautiful – colorful and faceted like little gemstones. I often find myself transfixed, staring with sleep-deprived eyes into the microscope, and refocusing my gaze before painstakingly coaxing one onto the tip of a glass fiber.

    Once I’ve gotten the crystal attached to the fiber, I begin the often frustrating task of centering the crystal on the tip of a gyroscope inside station B. This device will spin the crystal around, slowly and continuously, allowing me to get X-ray images of it from all sides.

    1
    On the left is the gyroscope, designed to rotate the crystal through a series of different angles as the X-ray beam hits it. Behind it is the detector panel which records the diffraction spots. On the right is a zoomed in picture of a single crystal, mounted on a glass fiber attached to the tip of the gyroscope. Kerry Rippy, CC BY-ND

    As it spins, liquid nitrogen vapor is used to cool it down: Even at room temperature, atoms vibrate back and forth, making it hard to get clear images of them. Cooling the crystal to minus 196 degrees Celsius, the temperature of liquid nitrogen, makes the atoms stop moving so much.

    X-ray photography

    Once I have the crystal centered and cooled, I close off station B, and from a computer control hub outside of it, blast the sample with X-rays. The resulting image, called a diffraction pattern, is displayed as bright spots on an orange background.

    2
    This is a diffraction pattern that results when you shoot an X-ray beam at a single crystal. Kerry Rippy, CC BY-ND

    What I am doing is not very different from taking photographs with a camera and a flash. I’m about to send light rays at an object and record how the light bounces off it. But I can’t use visible light to photograph atoms – they’re too small, and the wavelengths of light in the visible part of the spectrum are too big. X-rays have shorter wavelengths, so they will diffract, or bounce off atoms.

    However, unlike with a camera, diffracted X-rays can’t be focused with a simple lens. Instead of a photograph-like image, the data I collect are an unfocused pattern of where the X-rays went after they bounced off the atoms in my crystal. A full set of data about one crystal is made up of these images taken from every angle all around the crystal as the gyroscope spins it.

    Advanced math

    My colleague, Nicholas DeWeerd, sits nearby, analyzing data sets I’ve already collected. He has managed to ignore the blaring alarms and flashing lights for hours, staring at diffraction images on his screen to, in effect, turn the X-ray images from all sides of the crystal into a picture of the atoms inside the crystal itself.

    In years past, this process might have taken years of careful calculations done by hand, but now he uses computer modeling to put all the pieces together. He is our research group’s unofficial expert at this part of the puzzle, and he loves it. “It’s like Christmas!” I hear him mutter, as he flips through twinkling images of diffraction patterns.

    3
    Solving a set of diffraction patterns produces an atomic-level picture of a crystal, showing individual molecules (left) and how they pack together to form a crystalline structure. Kerry Rippy, CC BY-ND

    I smile at the enthusiasm he’s managed to maintain so late into the night, as I fire up the synchotron to get my pictures of the crystal perched in station B. I hold my breath as diffraction patterns from the first few angles pop up on the screen. Not all crystals diffract, even if I’ve set everything up perfectly. Often that’s because each crystal is made up of lots of even smaller crystals stuck together, or crystals containing too many impurities to form a repeating crystalline pattern that we can mathematically solve.

    If this one doesn’t deliver clear images, I’ll have to start over and set up another. Luckily, in this case, the first few images that pop up show bright, clear diffraction spots. I smile and sit back to collect the rest of the data set. Now as the gyroscope whirls and the X-ray beam blasts the sample, I have a few minutes to relax.

    I would drink some coffee to stay alert, but my hands are already shaking from caffeine overload. Instead, I call over to Nick: “I’m gonna take a lap.” I walk over to a group of tricycles sitting nearby. Normally used just to get around the large building containing the synchrotron, I find them equally helpful for a desperate attempt to wake up with some exercise.

    As I ride, I think about the crystal mounted on the gyroscope. I’ve spent months synthesizing it, and soon I’ll have a picture of it. With the picture, I’ll gain understanding of whether the modifications that I have made to it, which make it slightly different than other materials I have made in the past, have improved it at all. If I see evidence of better packing or increased intermolecular interactions, that could mean the molecule is a good candidate for testing in electronic devices.

    Exhausted, but happy because I’m collecting useful data, I slowly pedal around the loop, noting that the synchrotron is in high demand. When the beamline is running, it is used 24/7, which is why I’m working through the night. I was lucky to get a time slot at all. At other stations, other researchers like me are working late into the night.

    See the full article here .

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    The Conversation US launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 2:13 pm on November 28, 2018 Permalink | Reply
    Tags: , , First image, X-ray Technology   

    From European XFEL: “Capturing the strongest X-ray beam on Earth” 

    XFEL bloc

    European XFEL

    From European XFEL

    European XFEL


    The European XFEL beam. Copyright European XFEL

    At European XFEL scientists use intense X-rays to take pictures of the smallest particles imaginable. The European XFEL X-ray beam is a billion times brighter than other traditional X-ray sources, but since X-rays are invisible to the naked eye, it is not usually possible to see the X-ray beam. Working together with a professional photographer, scientists at the largest X-ray laser in the world located in Schenefeld near Hamburg, have now managed to capture an image of the intense European XFEL X-ray beam. The pictures were taken as the X-ray beam entered the experiment area in the FXE instrument hutch at the end of a journey that started in a 3.4km long underground tunnel.

    On the images published today, the X-ray beam appears as a thin blue stripe. What we are actually seeing, however, is glowing nitrogen molecules which the X-ray beam has caused to light up as it travels through the air thereby interacting with the molecules.

    “It works much like a fluorescent or neon lamp, where the gas in the centre of the tube lights up when the electric current is turned on”, explains Prof. Christian Bressler, team leader at the FXE (Femtosecond X-ray Experiments) instrument where the new images were made. Even though the European XFEL X-ray beam is extremely intense, the induced glow of the nitrogen molecules is, however, still relatively weak and not so easy to see with the naked eye. Today’s images were only possible when taken in complete darkness and using an exposure time of 90 seconds. The beam as seen in the images comprised 800 pulses per second, and has a thickness of 1mm. While the camera equipment was set-up inside the experiment hutch, the photos were taken remotely from outside the hutch, in the neighbouring control room.

    The method used to make the photos does not only lead to pretty results, but also has a scientific use. “With our sensitive detectors, we can use the glowing of the molecules induced by the X-ray beam for monitoring purposes” said Harald Sinn, responsible for X-ray optics at European XFEL.

    See the full article here .

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    XFEL Campus

    XFEL Tunnel

    XFEL Gun

    The Hamburg area will soon boast a research facility of superlatives: The European XFEL will generate ultrashort X-ray flashes—27 000 times per second and with a brilliance that is a billion times higher than that of the best conventional X-ray radiation sources.

    The outstanding characteristics of the facility are unique worldwide. Started in 2017, it will open up completely new research opportunities for scientists and industrial users.

     
  • richardmitnick 5:53 pm on November 12, 2018 Permalink | Reply
    Tags: , , , MicroED-micro-electron diffraction, , NMR-nuclear magnetic resonance, , , , X-ray Technology   

    From Caltech: “From Beaker to Solved 3-D Structure in Minutes” 

    Caltech Logo

    From Caltech

    11/12/2018

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    Graduate student Tyler Fulton prepares samples of small molecules in a lab at Caltech. Credit: Caltech

    2
    Close-up of a powder containing small molecules like those that gave rise to 3-D structures in the new study. (The copper piece is a sample holder used with microscopes.) Credit: Caltech/Stoltz Lab

    3
    Brian Stoltz and Tyler Fulton. Credit: Caltech

    UCLA/Caltech team uncovers a new and simple way to learn the structures of small molecules.

    In a new study that one scientist called jaw-dropping, a joint UCLA/Caltech team has shown that it is possible to obtain the structures of small molecules, such as certain hormones and medications, in as little as 30 minutes. That’s hours and even days less than was possible before.

    The team used a technique called micro-electron diffraction (MicroED), which had been used in the past to learn the 3-D structures of larger molecules, specifically proteins. In this new study, the researchers show that the technique can be applied to small molecules, and that the process requires much less preparation time than expected. Unlike related techniques—some of which involve growing crystals the size of salt grains—this method, as the new study demonstrates, can work with run-of-the-mill starting samples, sometimes even powders scraped from the side of a beaker.

    “We took the lowest-brow samples you can get and obtained the highest-quality structures in barely any time,” says Caltech professor of chemistry Brian Stoltz, who is a co-author on the new study, published in the journal ACS Central Science. “When I first saw the results, my jaw hit the floor.” Initially released on the pre-print server Chemrxiv in mid-October, the article has been viewed more than 35,000 times.

    The reason the method works so well on small-molecule samples is that while the samples may appear to be simple powders, they actually contain tiny crystals, each roughly a billion times smaller than a speck of dust. Researchers knew about these hidden microcrystals before, but did not realize they could readily reveal the crystals’ molecular structures using MicroED. “I don’t think people realized how common these microcrystals are in the powdery samples,” says Stoltz. “This is like science fiction. I didn’t think this would happen in my lifetime—that you could see structures from powders.”

    4
    This movie [animated in the full article] is an example of electron diffraction (MicroED) data collection, in which electrons are fired at a nanocrystal while being continuously rotated. Data from the movie are ultimately converted to a 3-D chemical structure. Credit: UCLA/Caltech

    The results have implications for chemists wishing to determine the structures of small molecules, which are defined as those weighing less than about 900 daltons. (A dalton is about the weight of a hydrogen atom.) These tiny compounds include certain chemicals found in nature, some biological substances like hormones, and a number of therapeutic drugs. Possible applications of the MicroED structure-finding methodology include drug discovery, crime lab analysis, medical testing, and more. For instance, Stoltz says, the method might be of use in testing for the latest performance-enhancing drugs in athletes, where only trace amounts of a chemical may be present.

    “The slowest step in making new molecules is determining the structure of the product. That may no longer be the case, as this technique promises to revolutionize organic chemistry,” says Robert Grubbs, Caltech’s Victor and Elizabeth Atkins Professor of Chemistry and a winner of the 2005 Nobel Prize in Chemistry, who was not involved in the research. “The last big break in structure determination before this was nuclear magnetic resonance spectroscopy, which was introduced by Jack Roberts at Caltech in the late ’60s.”

    Like other synthetic chemists, Stoltz and his team spend their time trying to figure out how to assemble chemicals in the lab from basic starting materials. Their lab focuses on such natural small molecules as the fungus-derived beta-lactam family of compounds, which are related to penicillins. To build these chemicals, they need to determine the structures of the molecules in their reactions—both the intermediate molecules and the final products—to see if they are on the right track.

    One technique for doing so is X-ray crystallography, in which a chemical sample is hit with X-rays that diffract off its atoms; the pattern of those diffracting X-rays reveals the 3-D structure of the targeted chemical. Often, this method is used to solve the structures of really big molecules, such as complex membrane proteins, but it can also be applied to small molecules. The challenge is that to perform this method a chemist must create good-sized chunks of crystal from a sample, which isn’t always easy. “I spent months once trying to get the right crystals for one of my samples,” says Stoltz.

    Another reliable method is NMR (nuclear magnetic resonance), which doesn’t require crystals but does require a relatively large amount of a sample, which can be hard to amass. Also, NMR provides only indirect structural information.

    Before now, MicroED—which is similar to X-ray crystallography but uses electrons instead of X-rays—was mainly used on crystallized proteins and not on small molecules. Co-author Tamir Gonen, an electron crystallography expert at UCLA who began developing the MicroED technique for proteins while at the Howard Hughes Medical Institute in Virginia, said that he only started thinking about using the method on small molecules after moving to UCLA and teaming up with Caltech.

    “Tamir had been using this technique on proteins, and just happened to mention that they can sometimes get it to work using only powdery samples of proteins,” says Hosea Nelson (PhD ’13), an assistant professor of chemistry and biochemistry at UCLA. “My mind was blown by this, that you didn’t have to grow crystals, and that’s around the time that the team started to realize that we could apply this method to a whole new class of molecules with wide-reaching implications for all types of chemistry.”

    The team tested several samples of varying qualities, without ever attempting to crystallize them, and were able to determine their structures thanks to the samples’ ample microcrystals. They succeeded in getting structures for ground-up samples of the brand-name drugs Tylenol and Advil, and they were able to identify distinct structures from a powdered mixture of four chemicals.

    The UCLA/Caltech team says it hopes this method will become routine in chemistry labs in the future.

    “In our labs, we have students and postdocs making totally new and unique molecular entities every day,” says Stoltz. “Now we have the power to rapidly figure out what they are. This is going to change synthetic chemistry.”

    The study was funded by the National Science Foundation, the National Institutes of Health, the Department of Energy, a Beckman Young Investigators award, a Searle Scholars award, a Pew Scholars award, the Packard Foundation, the Sloan Foundation, the Pew Charitable Trusts, and the Howard Hughes Medical Institute. Other co-authors include Christopher Jones,Michael Martynowycz, Johan Hattne, and Jose Rodriguez of UCLA; and Tyler Fulton of 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 4:16 pm on November 9, 2018 Permalink | Reply
    Tags: , , NSLS-II’s Coherent Soft X-ray scattering (CSX) beamline, The metal-insulator transition in the correlated material magnetite is a two-step process, Unlocking the Secrets of Metal-Insulator Transitions, X-ray Technology, XPCS- x-ray photon correlation spectroscopy   

    From Brookhaven National Lab: “Unlocking the Secrets of Metal-Insulator Transitions” 

    From Brookhaven National Lab

    November 8, 2018

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

    Written by Allison Gasparini

    X-ray photon correlation spectroscopy at NSLS-II’s CSX beamline used to understand electrical conductivity transitions in magnetite.

    1
    Professor Roopali Kukreja from the University of California in Davis and the CSX team Wen Hu, Claudio Mazzoli, and Andi Barbour prepare the beamline for the next set of experiments.

    By using an x-ray technique available at the National Synchrotron Light Source II (NSLS-II), scientists found that the metal-insulator transition in the correlated material magnetite is a two-step process. The researchers from the University of California Davis published their paper in the journal Physical Review Letters. NSLS-II, a U.S. Department of Energy (DOE) Office of Science user facility located at Brookhaven National Laboratory, has unique features that allow the technique to be applied with stability and control over long periods of time.

    “Correlated materials have interesting electronic, magnetic, and structural properties, and we try to understand how those properties change when their temperature is changed or under the application of light pulses, or an electric field” said Roopali Kukreja, a UC Davis professor and the lead author of the paper. One such property is electrical conductivity, which determines whether a material is metallic or an insulator.

    If a material is a good conductor of electricity, it is usually metallic, and if it is not, it is then known as an insulator. In the case of magnetite, temperature can change whether the material is a conductor or insulator. For the published study, the researchers’ goal was to see how the magnetite changed from insulator to metallic at the atomic level as it got hotter.

    In any material, there is a specific arrangement of electrons within each of its billions of atoms. This ordering of electrons is important because it dictates a material’s properties, for example its conductivity. To understand the metal-insulator transition of magnetite, the researchers needed a way to watch how the arrangement of the electrons in the material changed with the alteration of temperature.

    “This electronic arrangement is related to why we believe magnetite becomes an insulator,” said Kukreja. However, studying this arrangement and how it changes under different conditions required the scientists to be able to look at the magnetite at a super-tiny scale.

    2
    Roopali Kukreja (L), the lead author of the paper with Andi Barbour (R), CSX beamline scientist, work closely together while setting up the next set of measurements.

    The technique, known as x-ray photon correlation spectroscopy (XPCS), available at NSLS-II’s Coherent Soft X-ray scattering (CSX) beamline, allowed the researchers to look at how the material changed at the nanoscale—on the order of billionths of a meter.

    “CSX is designed for soft x-ray coherent scattering. This means that the beamline exploits our ultrabright, stable and coherent source of x-rays to analyze how the electron’s arrangement changes over time,” explained Andi Barbour, a CSX scientist who is a coauthor on the paper. “The excellent stability allows researchers to investigate tiny variations over hours so that the intrinsic electron behavior in materials can be revealed.”

    However, this is not directly visible so XPCS uses a trick to reveal the information.

    “The XPCS technique is a coherent scattering method capable of probing dynamics in a condensed matter system. A speckle pattern is generated when a coherent x-ray beam is scattered from a sample, as a fingerprint of its inhomogeneity in real space,” said Wen Hu, a scientist at CSX and co-author of the paper.

    Scientists can then apply different conditions to their material and if the speckle pattern changes, it means the electron ordering in the sample is changing. “Essentially, XPCS measures how much time it takes for a speckle’s intensity to become very different from the average intensity, which is known as decorrelation,” said Claudio Mazzoli, the lead beamline scientist at the CSX beamline. “Considering many speckles at once, the ensemble decorrelation time is the signature of the dynamic timescale for a given sample condition.”

    The technique revealed that the metal-insulator transition is not a one step process, as was previously thought, but actually happens in two steps.

    “What we expected was that things would go faster and faster while warming up. What we saw was that things get faster and faster and then they slow down. So the fast phase is one step and the second step is the slowing down, and that needs to happen before the material becomes metallic,” said Kukreja. The scientists suspect that the slowing down occurs because, during the phase change, the metallic and insulating properties actually exist at the same time in the material.

    “This study shows that these nanometer length scales are really important for these materials,” said Kukreja. “We can’t access this information and these experimental parameters anywhere else than at the CSX beamline of NSLS-II.”

    This research was funded by the National Science Foundation, the Air Force Office of Scientific Research, and the University of California’s Multicampus Research Programs and Initiatives.

    See the full article here .


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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 10:11 am on November 2, 2018 Permalink | Reply
    Tags: "In materials hit with light, , , individual atoms and vibrations take disorderly paths", , , , , X-ray Technology   

    From SLAC Lab: “In materials hit with light, individual atoms and vibrations take disorderly paths” 


    From SLAC Lab

    November 1, 2018
    Glennda Chui

    1
    Two studies with a new X-ray laser technique reveal for the first time how individual atoms and vibrations respond when a material is hit with light. Their surprisingly unpredictable behavior has profound implications for designing and controlling materials. (Greg Stewart/SLAC National Accelerator Laboratory)

    Revealed for the first time by a new X-ray laser technique, their surprisingly unruly response has profound implications for designing and controlling materials.

    Hitting a material with laser light sends vibrations rippling through its latticework of atoms, and at the same time can nudge the lattice into a new configuration with potentially useful properties – turning an insulator into a metal, for instance.

    Until now, scientists assumed this all happened in a smooth, coordinated way. But two new studies show it doesn’t: When you look beyond the average response of atoms and vibrations to see what they do individually, the response, they found, is disorderly.

    Atoms don’t move smoothly into their new positions, like band members marching down a field; they stagger around like partiers leaving a bar at closing time.

    And laser-triggered vibrations don’t simply die out; they trigger smaller vibrations that trigger even smaller ones, spreading out their energy in the form of heat, like a river branching into a complex network of streams and rivulets.

    This unpredictable behavior at a tiny scale, measured for the first time with a new X-ray laser technique at the Department of Energy’s SLAC National Accelerator Laboratory, will have to be taken into account from now on when studying and designing new materials, the researchers said – especially quantum materials with potential applications in sensors, smart windows, energy storage and conversion and super-efficient electrical conductors.

    Two separate international teams, including researchers at SLAC and Stanford University who developed the technique, reported the results of their experiments Sept. 20 in Physical Review Letters and today in Science.

    “The disorder we found is very strong, which means we have to rethink how we study all of these materials that we thought were behaving in a uniform way,” said Simon Wall, an associate professor at the Institute of Photonic Sciences in Barcelona and one of three leaders of the study reported in Science. “If our ultimate goal is to control the behavior of these materials so we can switch them back and forth from one phase to another, it’s much harder to control the drunken choir than the marching band.”

    Lifting the haze

    The classic way to determine the atomic structure of a molecule, whether from a manmade material or a human cell, is to hit it with X-rays, which bounce off and scatter into a detector. This creates a pattern of bright dots, called Bragg peaks, that can be used to reconstruct how its atoms are arranged.

    SLAC’s Linac Coherent Light Source (LCLS), with its super-bright and ultrafast X-ray laser pulses, has allowed scientists to determine atomic structures in ever more detail.

    SLAC/LCLS

    They can even take rapid-fire snapshots of chemical bonds breaking, for instance, and string them together to make “molecular movies.”

    About a dozen years ago, David Reis, a professor at SLAC and Stanford and investigator at the Stanford Institute for Materials and Energy Sciences (SIMES), wondered if a faint haze between the bright spots in the detector – 10,000 times weaker than those bright spots, and considered just background noise – could also contain important information about rapid changes in materials induced by laser pulses.

    He and SIMES scientist Mariano Trigo went on to develop a technique called “ultrafast diffuse scattering” that extracts information from the haze to get a more complete picture of what’s going on and when.

    The two new studies represent the first time the technique has been used to observe details of how energy dissipates in materials and how light triggers a transition from one phase, or state, of a material to another, said Reis, who along with Trigo is a co-author of both papers. These responses are interesting both for understanding the basic physics of materials and for developing applications that use light to switch the properties of materials on and off or convert heat to electricity, for instance.

    “It’s sort of like astronomers studying the night sky,” said Olivier Delaire, an associate professor at Duke University who helped lead one of the studies. “Previous studies could only see the brightest stars visible to the naked eye. But with the ultrabright and ultrafast X-ray pulses, we were able to see the faint and diffuse signals of the Milky Way galaxy between them.”

    Tiny bells and piano strings

    In the study published in Physical Review Letters, Reis and Trigo led a team that investigated vibrations called phonons that rattle the atomic lattice and spread heat through a material.

    The researchers knew going in that phonons triggered by laser pulses decay, releasing their energy throughout the atomic lattice. But where does all that energy go? Theorists proposed that each phonon must trigger other, smaller phonons, which vibrate at higher frequencies and are harder to detect and measure, but these had never been seen in an experiment.

    To study this process at LCLS, the team hit a thin film of bismuth with a pulse of optical laser light to set off phonons, followed by an X-ray laser pulse about 50 quadrillionths of a second later to record how the phonons evolved. The experiments were led by graduate student Tom Henighan and postdoctoral researcher Samuel Teitelbaum of the Stanford PULSE Institute.

    For the first time, Trigo said, they were able to observe and measure how the initial phonons distributed their energy over a wider area by triggering smaller vibrations. Each of those small vibrations emanated from a distinct patch of atoms, and the size of the patch – whether it contained 7 atoms, or 9, or 20 – determined the frequency of the vibration. It was much like how ringing a big bell sets smaller bells tinkling nearby, or how plucking a piano string sets other strings humming.

    “This is something we’ve been waiting years to be able to do, so we were excited,” Reis said. “It’s a measurement of something absolutely fundamental to modern solid-state physics, for everything from how heat flows in materials to even, in principle, how light-induced superconductivity emerges, and it could not have been done without an X-ray free-electron laser like LCLS.”

    A disorderly march

    The paper in Science describes LCLS experiments with vanadium dioxide, a well-studied material that can flip from being an insulator to an electrical conductor in just 100 quadrillionths of a second.

    Researchers already knew how to trigger this switch with very short, ultrafast pulses of laser light. But until now they could only observe the average response of the atoms, which seemed to shuffle into their new positions in an orderly way, said Delaire, who led the study with Wall and Trigo.

    The new round of diffuse scattering experiments at LCLS showed otherwise. By hitting the vanadium dioxide with an optical laser of just the right energy, the researchers were able to trigger a substantial rearrangement of the vanadium atoms. They did this more than 100 times per second while recording the movements of individual atoms with the LCLS X-ray laser. They discovered that each atom followed an independent, seemingly random path to its new lattice position. Computer simulations by Duke graduate student Shan Yang backed up that conclusion.

    “Our findings suggest that disorder may play an important role in some materials,” the team wrote in the Science paper. While this may complicate efforts to control the way materials shift from one phase to another, they added, “it could ultimately provide a new perspective on how to control matter,” and even suggest a new way to induce superconductivity with light.

    In a commentary accompanying the report in Science, Andrea Cavalleri of Oxford University and the Max Planck Institute for the Structure and Dynamics of Matter said the results imply that molecular movies of atoms changing position over time don’t paint a complete picture of the microscopic physics involved.

    He added, “More generally, it is clear from this work that x-ray free electron lasers are opening up far more than what was envisaged when these machines were being planned, forcing us to reevaluate many old notions taken for granted up to now.”

    The study published in PRL also involved researchers from Imperial College London; Tyndall National Institute in Ireland; and the University of Michigan, Ann Arbor. Preliminary measurements were performed at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL). Major funding came from the DOE Office of Science.

    SLAC/SSRL

    The study published in Science also involved researchers at the Japan Synchrotron Radiation Research Institute and the DOE’s Oak Ridge National Laboratory. Calculations were performed using resources of the DOE’s National Energy Research Scientific Computing Center (NERSC), and computer simulations used resources of the Oak Ridge Leadership Computing Facility. Major funding came from the European Research Council under the European Union’s Horizon 2020 research and innovation program and from the DOE Office of Science.

    LCLS, SSRL and NERSC are DOE Office of Science user facilities.

    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.

     
  • richardmitnick 10:37 am on November 1, 2018 Permalink | Reply
    Tags: , , , , , , X-ray Technology   

    From SLAC National Accelerator Lab: “Scientists make first detailed measurements of key factors related to high-temperature superconductivity” 

    From SLAC National Accelerator Lab

    October 31, 2018
    Glennda Chui

    1
    A new study reveals how coordinated motions of copper (red) and oxygen (grey) atoms in a high-temperature superconductor boost the superconducting strength of pairs of electrons (white glow), allowing the material to conduct electricity without any loss at much higher temperatures. The discovery opens a new path to engineering higher-temperature superconductors. (Greg Stewart/SLAC National Accelerator Laboratory)

    2
    An illustration depicts the repulsive energy (yellow flashes) generated by electrons in one layer of a cuprate material repelling electrons in the next layer. Theorists think this energy could play a critical role in creating the superconducting state, leading electrons to form a distinctive form of “sound wave” that could boost superconducting temperatures. Scientists have now observed and measured those sound waves for the first time. (Greg Stewart/SLAC National Accelerator Laboratory)

    In superconducting materials, electrons pair up and condense into a quantum state that carries electrical current with no loss. This usually happens at very low temperatures. Scientists have mounted an all-out effort to develop new types of superconductors that work at close to room temperature, which would save huge amounts of energy and open a new route for designing quantum electronics. To get there, they need to figure out what triggers this high-temperature form of superconductivity and how to make it happen on demand.

    Now, in independent studies reported in Science and Nature, scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University report two important advances: They measured collective vibrations of electrons for the first time and showed how collective interactions of the electrons with other factors appear to boost superconductivity.

    Carried out with different copper-based materials and with different cutting-edge techniques, the experiments lay out new approaches for investigating how unconventional superconductors operate.

    “Basically, what we’re trying to do is understand what makes a good superconductor,” said co-author Thomas Devereaux, a professor at SLAC and Stanford and director of SIMES, the Stanford Institute for Materials and Energy Sciences, whose investigators led both studies.

    “What are the ingredients that could give rise to superconductivity at temperatures well above what they are today?” he said. “These and other recent studies indicate that the atomic lattice plays an important role, giving us hope that we are gaining ground in answering that question.”

    The high-temperature puzzle

    Conventional superconductors were discovered in 1911, and scientists know how they work: Free-floating electrons are attracted to a material’s lattice of atoms, which has a positive charge, in a way that lets them pair up and flow as electric current with 100 percent efficiency. Today, superconducting technology is used in MRI machines, maglev trains and particle accelerators.

    But these superconductors work only when chilled to temperatures as cold as outer space. So when scientists discovered in 1986 that a family of copper-based materials known as cuprates can superconduct at much higher, although still quite chilly, temperatures, they were elated.

    The operating temperature of cuprates has been inching up ever since – the current record is about 120 degrees Celsius below the freezing point of water – as scientists explore a number of factors that could either boost or interfere with their superconductivity. But there’s still no consensus about how the cuprates function.

    “The key question is how can we make all these electrons, which very much behave as individuals and do not want to cooperate with others, condense into a collective state where all the parties participate and give rise to this remarkable collective behavior?” said Zhi-Xun Shen, a SLAC/Stanford professor and SIMES investigator who participated in both studies.

    Behind-the-scenes boost

    One of the new studies, at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), took a systematic look at how “doping” – adding a chemical that changes the density of electrons in a material – affects the superconductivity and other properties of a cuprate called Bi2212.

    SLAC/SSRL


    SLAC/SSRL

    Collaborating researchers at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan prepared samples of the material with slightly different levels of doping. Then a team led by SIMES researcher Yu He and SSRL staff scientist Makoto Hashimoto examined the samples at SSRL with angle-resolved photoemission spectroscopy, or ARPES. It uses a powerful beam of X-ray light to kick individual electrons out of a sample material so their momentum and energy can be measured. This reveals what the electrons in the material are doing.

    In this case, as the level of doping increased, the maximum superconducting temperature of the material peaked and fell off again, He said.

    The team focused in on samples with particularly robust superconducting properties. They discovered that three interwoven effects – interactions of electrons with each other, with lattice vibrations and with superconductivity itself – reinforce each other in a positive feedback loop when conditions are right, boosting superconductivity and raising the superconducting temperature of the material.

    Small changes in doping produced big changes in superconductivity and in the electrons’ interaction with lattice vibrations, Devereaux said. The next step is to figure out why this particular level of doping is so important.

    “One popular theory has been that rather than the atomic lattice being the source of the electron pairing, as in conventional superconductors, the electrons in high-temperature superconductors form some kind of conspiracy by themselves. This is called electronic correlation,” Yu He said. “For instance, if you had a room full of electrons, they would spread out. But if some of them demand more individual space, others will have to squeeze closer to accommodate them.”

    In this study, He said, “What we find is that the lattice has a behind-the-scenes role after all, and we may have overlooked an important ingredient for high-temperature superconductivity for the past three decades,” a conclusion that ties into the results of earlier research by the SIMES group Science.

    Electron ‘Sound Waves’

    The other study, performed at the European Synchrotron Radiation Facility (ESRF) in France, used a technique called resonant inelastic X-ray scattering, or RIXS, to observe the collective behavior of electrons in layered cuprates known as LCCO and NCCO.


    ESRF. Grenoble, France

    RIXS excites electrons deep inside atoms with X-rays, and then measures the light they give off as they settle back down into their original spots.

    In the past, most studies have focused only on the behavior of electrons within a single layer of cuprate material, where electrons are known to be much more mobile than they are between layers, said SIMES staff scientist Wei-Sheng Lee. He led the study with Matthias Hepting, who is now at the Max Planck Institute for Solid State Research in Germany.

    But in this case, the team wanted to test an idea raised by theorists – that the energy generated by electrons in one layer repelling electrons in the next one plays a critical role in forming the superconducting state.

    When excited by light, this repulsion energy leads electrons to form a distinctive sound wave known as an acoustic plasmon, which theorists predict could account for as much as 20 percent of the increase in superconducting temperature seen in cuprates.

    With the latest in RIXS technology, the SIMES team was able to observe and measure those acoustic plasmons.

    “Here we see for the first time how acoustic plasmons propagate through the whole lattice,” Lee said. “While this doesn’t settle the question of where the energy needed to form the superconducting state comes from, it does tell us that the layered structure itself affects how the electrons behave in a very profound way.”

    This observation sets the stage for future studies that manipulate the sound waves with light, for instance, in a way that enhances superconductivity, Lee said. The results are also relevant for developing future plasmonic technology, he said, with a range of applications from sensors to photonic and electronic devices for communications.

    SSRL is a DOE Office of Science user facility, and SIMES is a joint institute of SLAC and Stanford.

    In addition to researchers from SLAC, Stanford and AIST, the study carried out at SSRL involved scientists from University of Tokyo; University of California, Berkeley; and Lorentz Institute for Theoretical Physics in the Netherlands.

    The study conducted at ESRF also involved researchers from SSRL; Polytechnic University of Milan in Italy; ESRF; Binghamton University in New York; and the University of Maryland.

    Both studies were funded by the DOE Office of Science.

    See the full article here .


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