Tagged: SLAC LCLS Toggle Comment Threads | Keyboard Shortcuts

  • 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, SLAC LCLS,   

    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 .


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

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


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

     
  • richardmitnick 8:30 pm on February 21, 2019 Permalink | Reply
    Tags: , , , , Molecular ensemble, , , , PtPOP, , SLAC LCLS, ,   

    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 .


    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 11:19 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, , , , , SLAC LCLS,   

    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 10:11 am on November 2, 2018 Permalink | Reply
    Tags: "In materials hit with light, , , individual atoms and vibrations take disorderly paths", , SLAC LCLS, , ,   

    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 .

    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 10:42 pm on October 2, 2018 Permalink | Reply
    Tags: , , , , , , SLAC LCLS,   

    From SLAC National Accelerator Lab: “Peering into 36-million-degree plasma with SLAC’s X-ray laser” 

    From SLAC National Accelerator Lab

    October 2, 2018
    Ali Sundermier
    For commnication
    communications@slac.stanford.edu

    1
    At the Matter in Extreme Conditions (MEC) instrument at LCLS, the researchers zapped knuckle-shaped samples with a laser to create plasma, then used an X-ray scattering technique to watch it expand and collide. (Matt Beardsley/SLAC National Accelerator Laboratory)

    When you hit a piece of metal with a strong enough laser pulse you get a plasma – a hot, ionized gas found in everything from lightning to the sun. Studying it helps scientists understand what’s going on inside stars and could enable new types of particle accelerators for cancer treatment.

    Now a team of researchers has used an X-ray laser to measure, for the first time, how a plasma created by a laser blast expands in the hundreds of femtoseconds (quadrillionths of a second) after it’s created. Their technique could eventually reveal tiny instabilities in the plasma that swirl like cream in a cup of coffee.

    The experiments at the Department of Energy’s SLAC National Accelerator Laboratory involved scientists from SLAC, German research center Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and other institutions, and was reported in Physical Review X in September.

    Blasting cancer cells

    Led by scientist Thomas Kluge at HZDR, the researchers have been working to harness the behavior of plasma to create a new type of particle accelerator for proton therapy, an existing cancer treatment that involves blasting tumors with charged particles rather than X-rays. This approach is gentler on the surrounding healthy tissue than traditional radiation therapy.

    When solid matter is zapped with a laser the interaction forms a plasma, causing a steady stream of protons to burst out of the back side of the sample. The researchers hope to use the proton streams to storm tumors and obliterate cancer cells. But producing these fast protons in a reliable way requires a better understanding of how plasma changes as it expands.

    “Instabilities can arise from the complex streams of electrons and ions moving back and forth in the plasma,” Kluge says. “You probably know one of these instabilities from the mushroom-shaped clouds that form when you drip milk into your morning coffee.”

    Hotter than ever

    Until now, it was difficult to probe plasma changes directly because they’re so tiny and happen on extremely fast time scales. This work, says Josefine Metzkes-Ng, co-author and junior group leader at HZDR, could only be done at SLAC where the researchers used a high-power, short-pulse optical laser beam to create the plasma and the Linac Coherent Light Source X-ray free-electron laser to probe it.

    SLAC/LCLS

    At the Matter in Extreme Conditions (MEC) instrument at LCLS, researchers create incredibly hot and dense matter that mimics the extreme conditions in the hearts of stars and planets. Simulations show that the researchers achieved a new temperature record for matter studied with a free-electron laser: 36 million degrees Fahrenheit, almost 10 million degrees hotter than the sun’s core.

    The researchers fabricated solid samples that consisted of raised silicon bars, like knuckles sticking out from a fist. They found that in the quadrillionths of seconds after they zapped the sample with intense, short pulses from the optical laser, tiny amounts of plasma stacked up between the knuckles. A special form of scattering that uses X-ray pulses from LCLS allowed them to peer inside the plasma to follow its evolution.

    This technique will pave the way for better understanding plasma instabilities, allowing researchers to create proton sources for cancer therapy with relatively small footprints that, unlike conventional accelerators, can be operated within a hospital. It will also be useful in research relevant to fusion energy, other types of novel particle accelerators and laboratory astrophysics.

    Speedy cosmic particles

    Siegfried Glenzer, director of the High Energy Density Division at SLAC, who helped with the paper, is especially excited about the prospect of using this technique to better understand the astrophysical processes that give cosmic rays – subatomic space particles that plunge into Earth’s atmosphere at almost the speed of light – their extreme energies.

    The highest-energy cosmic rays can pack a force comparable to that of a major league fastball hurtling toward a batter at 100 mph, condensed into a single subatomic particle. To accelerate a proton to the same energies as these cosmic rays, scientists would have to build an accelerator that sends particles traveling from Earth to Saturn and back.

    Using LCLS, scientists are able to recreate some of the astrophysical processes that may produce these high-energy cosmic rays, such as energetic jets that shoot out from the turbulent hearts of active galaxies. Now the new technique will allow them to directly observe the plasma instabilities that might be responsible for accelerating cosmic rays.

    “Cosmic rays are the largest particle accelerators known to mankind,” Glenzer says. “They have a million times higher energy than particles accelerated in the Large Hadron Collider. Recently, astronomers traced a cosmic ray particle to an active galactic nucleus jet. Our goal is to produce these types of jets in the laboratory so we can study the formation of these instabilities and show whether they can accelerate particles to such high energies and, if so, how it happens.”

    Flipping the light switch

    According to Kluge, “This research has opened the black box of how short-pulse lasers interact with solids, allowing us to directly see a little of what’s going on, which previously could only be simulated with largely unverified atomic models.

    “It’s a little like switching on a light,” he says. “Although we have some ideas, we don’t know what we will find, but surely it will help us develop the next generation of laser-based ion accelerators and could shape new applications in astrophysics, medicine and plasma physics. For me as a theorist and simulation guy, the most exciting thing about this project is that I can now lay my simulations aside and look at the real thing.”

    The research team also included scientists from Technical University Dresden, European XFEL, University of Siegen, Friedrich Schiller University Jena and Leibniz Institute of Photonic Technology, all 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 .


    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 1:22 pm on August 7, 2018 Permalink | Reply
    Tags: Catching the dance of antibiotics and ribosomes at room temperature, , , , , , SLAC LCLS,   

    From SLAC National Accelerator Lab: “Catching the dance of antibiotics and ribosomes at room temperature” 

    From SLAC National Accelerator Lab

    August 6, 2018
    Ali Sundermier

    1
    Hasan DeMirci refers to ribosomes as the 3D printers of the human body because they synthesize proteins, which are essential to life. (Dawn Harmer/SLAC National Accelerator Laboratory)

    2
    Interns in DeMirci’s lab help grow ribosome crystals. Once grown and suspended in a special chemical solution called “mother liquor,” the crystals are imaged at the LCLS to uncover how they interact with antibiotics. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Antibiotics have been a pillar of modern medicine since the 1940s. Streptomycin, which belongs to a class of antibiotics called aminoglycosides, was the first hint of light in the millennia-long search for a treatment for tuberculosis, which remains one of the deadliest infectious diseases in human history.

    Today, aminoglycosides are the most commonly prescribed antibiotics in the world due to their low cost and high effectiveness in tackling a broad spectrum of bacterial infections. But they also bring along side effects that can have lifelong impacts. Depending on the dosage and the particular antibiotic, an estimated 10 to 20 percent of patients who take aminoglycosides suffer kidney damage and 20 to 60 percent end up with irreversible hearing loss.

    Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory have developed a new imaging technique to better understand the mechanisms that lead to hearing loss when aminoglycosides are introduced to the body. Using the lab’s Linac Coherent Light Source (LCLS) X-ray laser and Stanford Synchrotron Lightsource (SSRL), SLAC researchers, in collaboration with researchers at Stanford University, were able to observe interactions between the drugs and bacterial ribosomes at both extremely low and room temperatures, revealing never-before-seen details.

    SLAC LCLS

    SLAC/SSRL

    They also demonstrated how small modifications to the antibiotics can lead to dramatic changes in ribosome shape that eliminate hearing loss. The research could lead to a better understanding of which parts of a drug molecule cause unwanted reactions in the body, which will enable the development of more effective antibiotics with fewer side effects.

    The group was led by research associate and senior author Hasan DeMirci. Their results were published in Nucleic Acids Research.

    3D printing proteins

    Hasan DeMirci refers to ribosomes – tiny molecular machines made up of tangles of RNA and proteins clumped together and intricately wired like ramen noodles in soup – as “the 3D printers of the human body.” The ribosomes synthesize proteins using the genetic information contained in DNA, “building our bodies from the ground up.”

    3
    Ribosomes (shown here) are tiny molecular machines made up of tangles of RNA and proteins clumped together and intricately wired like ramen noodles in soup. (Hasan DeMirci/SLAC National Accelerator Laboratory)

    “While one subunit of the ribosome, its brain, deciphers and translates the genetic code, the other, its hands, links together amino acids to form proteins,” DeMirci said.

    Unlike viruses, which have to leech off hosts to survive, bacteria have their own ribosomes, which is where antibiotics come into play. Bacterial ribosomes are the targets of many antibiotics. So-called “cidal” antibiotics like aminoglycosides function by attacking the brains of bacterial ribosomes, causing them to make mistakes and fill the cells with protein-like garbage molecules.

    “It’s like a house with a lot of hoarded junk,” DeMirci says. “There’s no going back. From that point the bacteria just die.”

    The problem with this strategy is that human cells contain energy-producing factories called mitochondria that have their very own ribosomes – and since those ribosomes are dangerously similar to those found in bacteria, they’re also vulnerable to antibiotic attack.

    “We’re killing the bacteria, but the same drug gets into our mitochondria and destroys the ribosomes there,” DeMirci says. “Now we cannot produce those enzymes that power us. You take an antibiotic and you start losing your hearing, your kidney fails.”

    Insights into molecular machinery

    DeMirci has a strong interest in aminoglycosides because he can use them to gain insight into the molecular machinery of the ribosome.

    “What I really want to know is what those drugs can teach us about how ribosomes decipher the genetic code,” DeMirci said. “Drugs give us an opportunity to stop that process at different stages to understand how each and every step is catalyzed by the ribosome.”

    To better understand this process, he struck up a collaboration with Anthony Ricci, a biophysicist and professor of medicine at Stanford who focuses on the inner ear. In previous research, Ricci found that aminoglycosides infiltrate specialized channels to target the sensory cells essential to hearing.

    “You can think of it as a roach motel,” Ricci says. “The drugs can get in but they can’t get out. They start to build up, binding to the ribosomes and altering protein synthesis. This puts a huge metabolic load on the sensory cells, which eventually leads to their deaths.”

    A major goal of Ricci’s lab has been to design and develop new aminoglycosides that kill bacteria but cannot squeeze through the channel. In order to do this, the researchers need to understand exactly how the aminoglycosides interact with the ribosomes so they can modify parts of the drug without weakening its bacteria-killing properties.

    Defrosting interactions

    The best way to reach this understanding, researchers have found, is through a technique called X-ray crystallography. In X-ray crystallography, researchers use the patterns formed when a beam of X-rays scatters off a crystal sample to form a 3D model of how its atoms and molecules are arranged. This technique allows researchers to observe how a drug binds to a ribosome.

    While the key interactions in these processes happen at body temperature, around 37 degrees Celsius, X-ray crystallography usually has to be done at extremely low, or cryogenic, temperatures, around minus 180 degrees Celsius. This leads to gaps in the data, obscuring tiny details that could greatly inform future experiments.

    “Our bodies are warm, so the important biology is happening at body temperature,” DeMirci said, “but in crystallography everything is frozen. When you cool these processes down, you miss out on thermal fluctuations, tiny movements that could change your understanding of how the drugs and ribosomes are behaving.”

    In order to design better antibiotics, they need to get as close a view as they can of this interaction happening under physiological conditions. At the LCLS, using a technique called serial femtosecond crystallography, DeMirci is able to catch the intricate waltz of the drugs and ribosomes at room temperature. Rather than freeze the ribosome crystals, the researchers suspend them in ‘mother liquor,’ a special chemical solution they were grown in that keeps them stable, so they are “swimming happily, still wiggling and fluctuating,” he says.

    The crystals travel from a reservoir to the interaction region through a single capillary, like a garden hose. Once in the interaction region, the crystals are zapped with a beam of X-rays from the LCLS, which scatters off of them into a detector and provides the researchers with patterns they can use to build detailed 3D models of the ribosome before and after they’ve bound with the drugs. They then use these models to piece together a simulation of the interaction.

    4
    At LCLS, crystallized ribosomes travel through a capillary into the interaction region, where they are zapped with a beam of X-rays. The X-rays scatter off the crystals into a detector, providing the researchers with patterns they can use to build detailed 3D models of interactions between the drug and ribosome. (Greg Stewart/SLAC National Accelerator Laboratory)

    Uncovering hidden wiggles

    To demonstrate their technique, the researchers imaged modified and unmodified drugs binding to ribosomes at both cryogenic and room temperatures to see if they could catch any differences. They found that the drug molecules were less flexible at cryogenic temperatures: Tiny wiggles essential to a better understanding of their interactions with ribosomes were frozen in place.

    “Despite the fact that we’ve recorded hundreds of thousands of structures of ribosomal interactions, less than a handful of new-generation drugs have been designed based on these cryogenic structures,” DeMirci said. “That’s because every small interaction makes a huge difference, even a single hydrogen bond.”

    With the images taken at room temperature, Ricci’s group identified a site where the drug could be modified without altering its effectiveness.

    “We now have some idea that when the drug binds with the ribosome, a global change occurs in the ribosome that might actually be important for the function of the antibiotic and the sensitivity of the ribosome,” Ricci said.

    Refining the jigsaw pieces

    In the next phase of experiments, DeMirci hopes to design a setup in which the antibiotics aren’t introduced until the last second before the ribosome is imaged so that they can watch as it binds to the ribosome, rather than just taking images before and after.

    Up to this point, Ricci said, his group had been doing drug synthesis with very little information or insight into how the antibiotic interacts with the ribosome.

    “What this paper and overall collaboration allow is a direct investigation of the drug-ribosome interaction,” he said. “It’s like having more defined pieces to the jigsaw puzzle. You don’t have to guess about what’s happening.”

    Developing antibiotics that can fight off drug-resistant bacteria with minimal side effects is essential because the rise of antibiotic resistant strains is currently the biggest threat to modern medicine, DeMirci said.

    “Every year more than a million people die from tuberculosis and nearly half a million are HIV positive,” he said. “People don’t usually die from HIV or cancer, they die because their immune system is suppressed and they can’t fight off bacterial infections. That’s when you need antibiotics. But what if you don’t have one that’s effective against the resistant strains? That’s exactly what’s happening right now. This research can help us make informed decisions when designing the next generation of drugs.”

    The research team included scientists from LCLS; SSRL; SLAC’s Biosciences Division; the Stanford PULSE Institute; and the Stanford School of Medicine.

    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 1:56 pm on May 16, 2018 Permalink | Reply
    Tags: , , SLAC LCLS, Water is more complicated than it seems, X-ray Laser Reveals Ultrafast Dance of Liquid Water,   

    From SLAC Lab: “X-ray Laser Reveals Ultrafast Dance of Liquid Water” 


    From SLAC Lab

    May 16, 2018
    Water is more complicated than it seems. Now a study led by researchers at Stockholm University has probed the movements of its molecules on a timescale of millionths of a billionth of a second.

    1
    An illustration shows the “blurring” effect caused by water molecules moving during imaging with the X-ray laser. As the laser pulse gets longer, from left to right, the diffraction pattern produced by X-rays hitting the molecules changes (bottom row), reflecting the motion of the water molecules (top row). Experiments at SLAC’s LCLS X-ray laser were able to provide the timescale of the water dynamics by using pulses less than 100 millionths of a billionths of a second long. (Fivos Perakis/Stockholm University)

    Water’s lack of color, taste and smell make it seem simple – and on a molecular level, it is. However, when many water molecules come together they form a highly complex network of hydrogen bonds. This network is believed to be responsible for many of the peculiar properties of liquid water, but its behavior is not yet fully understood.

    Now researchers have probed the movements of molecules in liquid water that occur in less than 100 millionths of a billionth of a second, or femtoseconds. An international team led by researchers at Stockholm University carried out the experiments with the Linac Coherent Light Source (LCLS) X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory. They published their report this week in Nature Communications.

    SLAC/LCLS

    The study is the first to “photograph” water molecules on this timescale with a technique called ultrafast X-ray photon correlation spectroscopy, which bounces X-rays pulses off the molecules to produce a series of diffraction patterns. Varying the duration of the X-ray pulses essentially varies the exposure time, and any motion of the water molecules during an exposure will blur the resulting picture. By analyzing the blurring produced by different exposure times, the scientists were able to extract information about the molecular motion.

    On this timescale, it was assumed that water molecules move randomly due to heat, behaving more like a gas than a liquid. However, the experiments indicate that the network of hydrogen bonds plays a role even on this ultrafast timescale, coordinating the motions of water molecules in an intricate dance, which becomes even more pronounced when water is “supercooled” below its normal freezing point.

    “The key to understanding water on a molecular level is watching the changes of the hydrogen-bond network, which can play a major role in biological activity and life as we know it,” says Anders Nilsson, a professor at Stockholm University and former professor at SLAC.

    Adds Stockholm University researcher Fivos Perakis, “It is a brand-new capability to be able to use X-ray lasers to see the motion of molecules in real time. This can open up a whole new field of investigations on these timescales, combined with the unique structural sensitivity of X-rays.”

    The experimental results were reproduced by computer simulations, which indicate that the coordinated dance of water molecules is due to the formation of transient tetrahedral structures.

    “I have studied the dynamics of liquid and supercooled water for a long time using computer simulations, and it is very exciting to finally be able to directly compare with experiments,” says Gaia Camisasca, a postdoctoral researcher at Stockholm University who performed the computer simulations for this study. “I look forward to seeing the future results that can come out from this technique, which can help improve the current water computer models.”

    LCLS is a DOE Office of Science user facility. SLAC’s Thomas J. Lane, Sanghoon Song, Takahiro Sato, Marcin Sikorski, Andre Eilert, Trevor McQueen, Hirohito Ogasawara, Dennis Nordlund, Jake Koralek, Silke Nelson, Philip Hart, Roberto Alonso-Mori, Yiping Feng, Diling Zhu and Aymeric Robert contributed to this study, along with researchers from KTH Royal Institute of Technology in Stockholm and DESY in Hamburg.

    See the full article here .

    Please help promote STEM in your local schools.

    stem

    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 4:41 pm on May 10, 2018 Permalink | Reply
    Tags: , , , SLAC LCLS   

    From SLAC Labs: “SLAC’s X-ray Laser Opens New View on Proteins Related to Alzheimer’s Disease” 


    From SLAC Labs

    May 9, 2018
    Angela Anderson

    1
    Experiments at SLAC’s Linac Coherent Light Source show the promise of using X-ray free-electron lasers to better understand the structure and function of amyloid fibrils, tiny protein strands that play a role in diseases like Alzheimer’s and Parkinson’s. In this illustration, X-ray light penetrates a sample of amyloid fibrils placed on the honeycomb-like carbon lattice of graphene, a new method that produces cleaner data because the thin graphene virtually disappears from view. (Greg Stewart/SLAC)

    SLAC/LCLS

    To learn more about diseases such as Alzheimer’s and Parkinson’s, scientists have zeroed in on invisibly small protein filaments that bunch up to form fibrous clusters called amyloids in the brain: How do these fibrils form and how do they lead to disease?

    Until now, the best tools for studying them have generated limited views, largely because the fibrils strands are so complex and tiny, just a few nanometers thick.

    Now an international research team has come up with a new method with potential for revealing the structure of individual amyloid fibrils with powerful beams of X-ray laser light. They describe it in a report published today in Nature Communications.

    In experiments conducted at the Linac Coherent Light Source (LCLS) at the Department of Energy’s SLAC National Accelerator Laboratory, the scientists placed up to 50 fibrils at a time on a layer of graphene, whose carbon atoms are arranged in a honeycomb-like pattern, and hit them with bursts of X-ray laser light. The graphene, it turned out, was almost transparent to the X-rays, and this allowed them to probe the structures of the delicate fibrils without picking up significant extraneous signals from the graphene layer in individual snapshots.

    While the team did not uncover the complete fibril structure, they said the innovative method they developed at LCLS opens up a promising path for amyloid studies using X-ray free-electron lasers, or XFELs, such as LCLS.

    Carolin Seuring, a scientist at the Center for Free-Electron Laser Science (CFEL) at DESY in Germany and principal author of the paper, said the results suggest this technique could even be used to determine the structure of individual fibrils.

    “There is a common consensus that it is not the amyloid fiber alone, but rather the protofilaments composing the fiber and the process of fibril formation that are toxic to the cell,” she said. “XFEL-based experiments have the potential to overcome the challenges we’ve faced in better understanding amyloid fibrils.”

    The Problem with Amyloids

    While amyloid fibrils are believed to play a major role in the development of neurodegenerative diseases, scientists have recently discovered that they also have other functions, Seuring said.

    “The ‘feel-good hormone’ endorphin, for example, can form amyloid fibrils in the pituitary gland,” she said. “They dissolve into individual molecules when the acidity of their surroundings changes, after which these molecules can fullfil their purpose in the body. Other amyloid proteins, such as those found in post-mortem brains of patients suffering from Alzheimer’s, accumulate as amyloid fibrils in the brain, and cannot be broken down and therefore impair brain function in the long term.”

    Accurate information about the structure of amyloid fibrils can inform scientists about their function, she added.

    “Our aim is to understand the role of the formation and structure of amyloid fibrils in the body and in the development of neurodegenerative diseases,” Seuring said.

    One barrier to studying amyloid fibrils is that they cannot be grown as crystals, which are the conventional targets for structural studies using X-rays. And because individual amyloid fibrils are so small, they don’t produce a measurable signal when exposed to X-rays. Scientists typically line up millions of fibrils parallel to each other to amplify the signal, but information about their individual differences is lost in the process.

    “A major part of our understanding about amyloid fibrils is derived from nuclear magnetic resonance and cryo-electron microscopy data,” Seuring said. But these methods are also of limited value for seeing individual differences between amyloid fibrils or observing their formation. “The structural analysis of amyloids is complex and examining them using existing methods is hampered by differences between the fibrils within a single sample,’” she said “Being able to look at the individual components of the sample would make it possible to determine the 3D structure of one type of fibril at a time.”

    The New Approach

    Earlier attempts to study fibrils at X-ray lasers delivered them into the path of the beam in jets of fluid. Switching to a solid graphene carrier gave the team two advantages, according to CFEL’s Henry Chapman, a professor at the University of Hamburg and a lead scientist at DESY.

    Because graphene is just one layer of atoms thick, it leaves hardly a trace in the diffraction patterns formed by X-rays scattering off the fibrils, which are used to determine their structures, he said. And the regular structure of the graphene encourages the fibrils to all line up in the same direction.

    This allows diffraction patterns to be obtained from fewer than 50 amyloid fibrils. Based on the results, the team hopes to eventually get patterns from single fibrils. To get to that goal, new methods of exposing a single fibril to the XFEL beam will need to be developed, according to Seuring: “With enough snapshots, a full 3D data set of a single fibril should be possible.”

    The exceptionally bright and narrowly focused beam at LCLS’s Coherent X-ray Imaging instrument was also key to the team’s success in taking data from such a small number of fibrils, according to SLAC staff scientist Mengning Liang.

    Intense X-ray pulses at XFELs limit the exposure of delicate samples to damaging X-rays. In this study, the fibrils were exposed for only a few femtoseconds, or millionths of a billionth of a second. Before the molecules are destroyed, information about their structure can be read by detectors.

    “Fibrils are a third category of samples that can be studied with the ‘diffract before destroy’ method at XFELs, in addition to single particles and crystals,” Liang said. “In some regards, fibrils fit between the other two: they have regular, recurring variations in structure like crystals, but without the rigid crystal structure.”

    The scientists tested their method on samples of well-studied tobacco mosaic virus filaments and smaller amyloid fibrils, some of which are associated with certain types of cancer. The tests produced structural data with a high degree of accuracy: The resolution in the diffraction images was almost on the scale of a single atom.

    “It is amazing that we are essentially carrying out the same experiments as Rosalind Franklin did on DNA in 1952, which led to the discovery of the double helix, but now we are reaching the level of single molecules,” says Chapman.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 3:42 pm on May 5, 2018 Permalink | Reply
    Tags: , , , , , Freeze-framing nanosecond movements of nanoparticles, , SLAC LCLS,   

    From DESY: “Freeze-framing nanosecond movements of nanoparticles” 

    DESY
    From DESY

    2018/05/03
    No writer credit

    New method allows to monitor fast movements at hard X-ray lasers.

    A team of scientists from DESY, the Advanced Photon Source APS and National Accelerator Laboratory SLAC, both in the USA, have developed and integrated a new method for monitoring ultrafast movements of nanoscopic systems.

    Argonne APS

    SLAC LCLS

    With the light of the X-ray laser LCLS at the research center SLAC in California, they took images of the movements of nanoparticles taking only the billionth of a second (0,000 000 001 s).

    SLAC LCLS

    In their experiments now published in the journal Nature Communications they overcame the slowness of present-day two-dimensional X-ray detectors by splitting individual laser flashes of LCLS, delaying one half of it by a nanosecond and recording a single picture of the nanoparticle with these pairs of X-ray pulses. The tunable light splitter for hard X-rays which the scientists developed for these experiments enables this new technique to monitor movements of nanometer size fluctuations down to femtoseconds and at atomic resolution. For comparison: modern synchrotron radiation light sources like PETRA III at DESY can typically measure movements on millisecond timescales.

    DESY Petra III interior

    1
    Scheme of the experiment: An autocorrelator developed at DESY splits the ultrashort X-ray laser pulses into two equal intensity pulses which arrive with a tunable delay at the sample. The speckle pattern of the sample is collected in a single exposure of the 2-D detector (picture: W. Roseker/DESY).

    he intense light flashes of X-ray lasers are coherent which means that the waves of the monochromatic laser light propagate in phase to each other. Diffracting coherent light by a sample usually results in a so-called speckle diffraction pattern showing apparently randomly ordered light spots. However, this speckle is also a map of the sample arrangement, and movements of the sample constituents result in a different speckle pattern.

    For their experiments the researchers developed a special optical setup – a so-called optical autocorrelator – capable of splitting 100 femtosecond long XFEL pulses into two sub-pulses, deviate them into separated detours and recombining their paths with a tunable time delay between zero and a few nanoseconds. These pairs of XFEL pulses hit the sample with the tuned delay, spotting the sample´s structure at the two exposure times. The sum of both speckle pictures was recorded by a two-dimensional photon detector within one exposure time. The trick: If the constituents of the sample move during the two illuminations, the speckle pattern changes, resulting in an integrated picture of less contrast at the detector. The contrast is a measure on how strong the photon intensity varies on the detector. However, the intensity and especially the intensity difference measured at the detector are very weak. In their experiments the researchers had to work with only some 1000 detected photons on the one-million-pixels size detector.

    “Such type of experiments has been done for much slower movements of nanoparticles at storage ring light sources,” explains first author Wojciech Roseker from DESY. “But now, the high coherence and intensity of the X-ray laser light at XFELs open up the opportunity to get pictures bright enough to provide reasonable information about quick movements in the nanosecond to femtosecond regime.”

    In their work the researchers around Roseker used a suspension of two nanometers size gold particles undergoing Brownian motion. The experiment was in perfect agreement with the theoretical predictions thus proving not only the performance of the autocorrelator setup but also the validity of the data analysis procedure, demonstrating the first successful experiment of this kind. One of the challenges in this experiment, carried out at the XCS experimental station at LCLS, was to autocorrelate thousands of extremely weak double shot 2D images which was achieved with the help of a newly developed maximum likelihood analysis technique.

    “This experiment paves the way to dynamics experiments of materials on atomic length and femtosecond-nanosecond timescales,” explains Gerhard Grübel, head of the DESY FS-CXS group. “Split-pulse X-ray Photon Correlation Spectroscopy (XPCS) can potentially track atomic scale fluctuations in liquid metals, multi-scale dynamics in water, heterogeneous dynamics about the glass transition, and atomic scale surface fluctuations.” Additionally, time-domain XPCS at FEL sources, especially at the European XFEL, is well suited for studying fluctuations in non-equilibrium processes that go beyond time-averaged structural descriptions.


    DESY European XFEL


    European XFEL

    This will allow the elucidation of dynamics of ultrafast magnetization processes and can address open questions concerning photo-induced phonon dynamics and phase transitions.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

     
  • richardmitnick 7:45 pm on April 26, 2018 Permalink | Reply
    Tags: , DESY FLASH free-electron laser at Germany’s Deutsches Elektronen-Synchrotron, Flowing sheets of liquid just 100 water molecules thick that persist for days in a vacuum, Images of samples suspended in water with two types of light – infrared and ‘soft’, , , Researchers used X-ray pulses to heat the liquid sheets to thousands of degrees to simulate the extremely warm dense form of water present in giant planets like Jupiter, SLAC LCLS, The nozzle is a tiny glass chip with three microscopic channels, There are many mysteries in those big planets and they’re important for understanding the evolution of our planetary system as well as others, Thin free-flowing sheets 100 times thinner than any produced before, X-Ray Scientists Create Tiny Super-Thin Sheets of Flowing Water that Shimmer Like Soap Bubbles   

    From SLAC: “X-Ray Scientists Create Tiny, Super-Thin Sheets of Flowing Water that Shimmer Like Soap Bubbles” 


    SLAC Lab

    April 26, 2018
    Glennda Chui

    The liquid sheets – less than 100 water molecules thick – will let researchers probe chemical, physical and biological processes, and even the nature of water itself, in a way they could never do before.

    1
    This tiny glass chip creates super-thin sheets of flowing liquid for X-ray experiments at SLAC’s X-ray laser, LCLS. A stream of liquid flowing through the middle channel is shaped by flows of gas coming in from the channels on either side. (Dawn Harmer/SLAC National Accelerator Laboratory.)

    Water is an essential ingredient for life as we know it, making up more than half of the adult human body and up to 90 percent of some other living things. But scientists trying to examine tiny biological samples with certain wavelengths of light haven’t been able to observe them in their natural, watery environments because the water absorbs too much of the light.

    Now there’s a way around that problem: A team led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory turned tiny liquid jets that carry samples into the path of an X-ray beam into thin, free-flowing sheets, 100 times thinner than any produced before. They’re so thin that X-rays pass through them unhindered, so images of the samples they carry come out clear.

    The new method opens new windows on critical processes in chemistry, physics and biology, including the nature of water itself, the researchers said in an April 10 report in Nature Communications.

    The method was developed at SLAC’s X-ray free-electron laser, the Linac Coherent Light Source (LCLS), but they said it can also work in experiments with synchrotron light sources, tabletop lasers and electron beams.

    SLAC/LCLS

    3
    A series of movies shows how increasing flows of gas that shape a stream of liquid affects the formation of liquid sheets and their soap-bubble-like sheen.

    “This opens up possibilities in a lot of fields,” said SLAC staff scientist Jake Koralek, who led the research with Daniel DePonte, leader of the LCLS Sample Environment Department.

    “Until now, we haven’t been able to make images of samples suspended in water with two types of light – infrared and ‘soft’, lower-energy X-rays – that are important for studying basic processes in physics, chemistry and biology, including the physics of water,” Koralek said.

    “The new nozzle we developed, which can create flowing sheets of liquid just 100 water molecules thick that persist for days in a vacuum, solves that problem. The sheets can even be used to image samples with electron beams that resolve even smaller details.”

    Shaping Liquid with Gas

    The nozzle is a tiny glass chip with three microscopic channels. A stream of liquid flows through the middle channel, shaped by flows of gas coming in from the channels on either side. This particular nozzle was made with photolithography, a technique used to manufacture computer chips, but it could also be crafted with 3-D printing, the researchers noted.

    As the scientists turn up the speed of the gas flow, the liquid stream spreads into a series of sheets whose width and thickness can be precisely controlled. The sheet closest to the nozzle is the widest and thinnest; the farther they get from the nozzle, the narrower and thicker the sheets become until they finally merge into a cylindrical stream.

    53
    These images show the formation of tiny sheets of liquid shaped by jets of gas from a nozzle developed at SLAC. Top: As the gas flow increases, the liquid sheets become bigger. Bottom: The nozzle produces a series of liquid sheets; the one closest to the nozzle is the widest and thinnest. Each sheet is perpendicular to the previous one, so we are seeing the second and fourth sheets from the side.

    The sheets shimmer like soap bubbles in a variety of colors, the result of light reflecting off both the front and back surfaces of the sheet. And just as the contour lines on a topographic map mark differences in elevation, the hue and spacing of a sheet’s ever-changing bands of color indicate how thick it is and how much the thickness changes from one point to another.

    “It’s a very flexible and reliable design for creating both ultrathin and slightly thicker liquid sheets, which can be desirable for some applications” said Linda Young, a distinguished fellow at DOE’s Argonne National Laboratory and professor at the University of Chicago who was not involved in the study.

    She said she will be using the nozzle to make slightly thicker sheets of water for an LCLS study of how water molecules behave after one of their electrons has been ripped away. These ionized water molecules persist for only a few hundred femtoseconds, or millions of a billionth of a second, and “the X-rays provide a completely new and clean wayto monitor their electronic response in their natural environment, so that’s why we’re excited about it,” Young said.

    A New Way to Study Extreme Forms of Water

    The liquid sheets have already been used in experiments that explore the properties of water in extreme environments like those on giant planets, said co-author Siegfried Glenzer, a SLAC professor and head of the lab’s High Energy Density Science Division.

    Those experiments were performed with the FLASH free-electron laser at Germany’s Deutsches Elektronen-Synchrotron (DESY).

    7
    DESY FLASH free-electron laser at Germany’s Deutsches Elektronen-Synchrotron.

    Researchers used X-ray pulses to heat the liquid sheets to thousands of degrees to simulate the extremely warm, dense form of water present in giant planets like Jupiter. Then they measured the reflectivity and conductivity of the super-hot water with optical laser pulses in the instant before the water vaporized. These measurements could only be made on a flat sheet of water.

    “There are many mysteries in those big planets and they’re important for understanding the evolution of our planetary system as well as others,” Glenzer said. “This is a beautiful tool for studying water itself, and in the future we will also study other materials that we can mix into it.”

    8
    A SLAC research team at the LCLS experimental station where they carried out experiments with the sheet-forming nozzle this week. From left: Paper co-authors Zhijiang Chen, Stefan Moeller, Siegfried Glenzer, Jake Koralek and Chandra Curry and area manager Bob Sublett of the LCLS Sample Environment Department. (Dawn Harmer/SLAC National Accelerator Laboratory)

    The team measured the thickness of the sheets with a beam of infrared light at the Advanced Light Source at the DOE’s Lawrence Berkeley National Laboratory, and also demonstrated that the sheets could be used for infrared spectroscopy, where light absorbed by a material reveals its chemical makeup.

    LBNL/ALS

    LCLS and the Advanced Light Source are DOE Office of Science user facilities. In addition to researchers from SLAC, Berkeley Lab and DESY, scientists from the ELI Beamlines Institute of Physics of the Czech Academy of Sciences, Dartmouth College, the University of Alberta in Canada and the European X-ray Free-Electron Laser Facility (European XFEL) in Germany contributed to this work. Major funding came from the DOE Office of Science and the National Institutes of Health, National Institute of General Medical Sciences.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: