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  • richardmitnick 7:48 am on November 4, 2016 Permalink | Reply
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    From SLAC: SLAC, Berkeley Lab Researchers Prepare for Scientific Computing on the Exascale” 


    SLAC Lab

    November 3, 2016

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    NERSC CRAY Cori supercomputer
    Development and testing of future exascale computing tools for X-ray laser data analysis and the simulation of plasma wakefield accelerators will be done on the Cori supercomputer at NERSC, the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory. (NERSC)

    Researchers at the Department of Energy’s SLAC National Accelerator Laboratory are playing key roles in two recently funded computing projects with the goal of developing cutting-edge scientific applications for future exascale supercomputers that can perform at least a billion billion computing operations per second – 50 to 100 times more than the most powerful supercomputers in the world today.

    The first project, led by SLAC, will develop computational tools to quickly sift through enormous piles of data produced by powerful X-ray lasers. The second project, led by DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab), will reengineer simulation software for a potentially transformational new particle accelerator technology, called plasma wakefield acceleration.

    The projects, which will each receive $10 million over four years, are among 15 fully-funded application development proposals and seven proposals selected for seed funding by the DOE’s Exascale Computing Project (ECP). The ECP is part of President Obama’s National Strategic Computing Initiative and intends to maximize the benefits of high-performance computing for U.S. economic competiveness, national security and scientific discovery.

    “Many of our modern experiments generate enormous quantities of data,” says Alex Aiken, professor of computer science at Stanford University and director of the newly formed SLAC Computer Science division, who is involved in the X-ray laser project. “Exascale computing will create the capabilities to handle unprecedented data volumes and, at the same time, will allow us to solve new, more complex simulation problems.”

    Analyzing ‘Big Data’ from X-ray Lasers in Real Time

    X-ray lasers, such as SLAC’s Linac Coherent Light Source (LCLS) have been proven to be extremely powerful “microscopes” that are capable of glimpsing some of nature’s fastest and most fundamental processes on the atomic level.

    SLAC/LCLS
    SLAC/LCLS

    Researchers use LCLS, a DOE Office of Science User Facility, to create molecular movies, watch chemical bonds form and break, follow the path of electrons in materials and take 3-D snapshots of biological molecules that support the development of new drugs.

    At the same time X-ray lasers also generate giant amounts of data. A typical experiment at LCLS, which fires 120 flashes per second, fills up hundreds of thousands of gigabytes of disk space. Analyzing such a data volume in a short amount of time is already very challenging. And this situation is set to become dramatically harder: The next-generation LCLS-II X-ray laser will deliver 8,000 times more X-ray pulses per second, resulting in a similar increase in data volumes and data rates.

    SLAC/LCLS II schematic
    SLAC/LCLS II schematic

    Estimates are that the data flow will greatly exceed a trillion data ‘bits’ per second, and require hundreds of petabytes of online disk storage.

    As a result of the data flood even at today’s levels, researchers collecting data at X-ray lasers such as LCLS presently receive only very limited feedback regarding the quality of their data.

    “This is a real problem because you might only find out days or weeks after your experiment that you should have made certain changes,” says Berkeley Lab’s Peter Zwart, one of the collaborators on the exascale project, who will develop computer algorithms for X-ray imaging of single particles. “If we were able to look at our data on the fly, we could often do much better experiments.”

    Amedeo Perazzo, director of the LCLS Controls & Data Systems Division and principal investigator for this “ExaFEL” project, says, “We want to provide our users at LCLS, and in the future LCLS-II, with very fast feedback on their data so that can make important experimental decisions in almost real time. The idea is to send the data from LCLS via DOE’s broadband science network ESnet to NERSC, the National Energy Research Scientific Computing Center, where supercomputers will analyze the data and send the results back to us – all of that within just a few minutes.” NERSC and ESnet are DOE Office of Science User Facilities at Berkeley Lab.

    LBL NERSC Cray XC30 Edison supercomputer
    LBL NERSC Cray XC30 Edison supercomputer

    lcls-ii-image
    LCLS II

    X-ray data processing and analysis is quite an unusual task for supercomputers. “Traditionally these high-performance machines have mostly been used for complex simulations, such as climate modeling, rather than processing real-time data” Perazzo says. “So we’re breaking completely new ground with our project, and foresee a number of important future applications of the data processing techniques being developed.”

    This project is enabled by the investments underway at SLAC to prepare for LCLS-II, with the installation of new infrastructure capable of handling these enormous amounts of data.

    A number of partners will make additional crucial contributions.

    “At Berkeley Lab, we’ll be heavily involved in developing algorithms for specific use cases,” says James Sethian, a professor of mathematics at the University of California, Berkeley, and head of Berkeley Lab’s Mathematics Group and the Center for Advanced Mathematics for Energy Research Applications (CAMERA). “This includes work on two different sets of algorithms. The first set, developed by a team led by Nick Sauter, consists of well-established analysis programs that we’ll reconfigure for exascale computer architectures, whose larger computer power will allow us to do better, more complex physics. The other set is brand new software for emerging technologies such as single-particle imaging, which is being designed to allow scientists to study the atomic structure of single bacteria or viruses in their living state.”

    The “ExaFEL” project led by Perazzo will take advantage of Aiken’s newly formed Stanford/SLAC team, and will collaborate with researchers at Los Alamos National Laboratory to develop systems software that operates in a manner that optimizes its use of the architecture of the new exascale computers.

    “Supercomputers are very complicated, with millions of processors running in parallel,” Aiken says. “It’s a real computer science challenge to figure out how to use these new architectures most efficiently.”

    Finally, ESnet will provide the necessary networking capabilities to transfer data between the LCLS and supercomputing resources. Until exascale systems become available in the mid-2020s, the project will use NERSC’s Cori supercomputer for its developments and tests.

    esnet-map
    ESnet

    See the full article here .

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  • richardmitnick 7:40 am on October 12, 2016 Permalink | Reply
    Tags: , , , SLAC LCLS,   

    From SLAC: “X-rays Reveal New Path In Battle Against Mosquito-borne Illness” 


    SLAC Lab

    `
    The mosquito larvicide BinAB is composed of two proteins, BinA (yellow) and BinB (blue). Inside bacterial cells, BinAB naturally forms nanocrystals. Using these crystals and the intense X-ray pulses produced by SLAC’s Linac Coherent Light Source, scientists shed light on the three-dimensional structure of BinAB and its mode of action. (SLAC National Accelerator Laboratory)

    September 28, 2016

    SLAC’s X-ray Laser Provides Clues to Engineering a New Protein to Kill Mosquitos Carrying Dengue, Zika

    Structural biology research conducted at the U.S. Department of Energy’s SLAC National Accelerator Laboratory has uncovered how small insecticidal protein crystals that are naturally produced by bacteria might be tailored to combat dengue fever and the Zika virus.

    SLAC’s X-ray free-electron laser – the Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility – offered unprecedented views of the toxin BinAB, used as a larvicide in public health efforts against mosquito-borne diseases such as malaria, West Nile virus and viral encephalitis.

    SLAC/LCLS
    SLAC/LCLS

    The larvicide is currently ineffective against the Aedes mosquitos that transmit Zika and dengue fever, and therefore not used to combat these species of mosquitos at this time. The new information provides clues to how scientists could design a composite toxin that would work against a broader range of mosquito species, including Aedes.

    Today, Nature published the study.

    “A more detailed look at the proteins’ structure provides information fundamental to understanding how the crystals kill mosquito larvae,” said Jacques-Philippe Colletier, a scientist at the Institut de Biologie Structurale in Grenoble, France and lead author on the paper. “This is a prerequisite for modifying the toxin to adapt it to our needs.”

    Selective Mosquito Control, Courtesy of Bacteria

    The BinAB crystals are produced by Lysinibacillus sphaericus bacteria, which release the crystals along with spores at the end of their life cycle. Mosquito larvae eat the crystals along with the spores, and then die.

    BinAB is inactive in the crystalline state and does not work on contact. For the crystals to dissolve, they must be exposed to alkaline conditions, such as those in a mosquito larva’s gut. The binary protein is then activated, recognized by a specific receptor at the surface of cells and internalized.

    Because Aedes larvae can evade one of these steps of intoxication, they are resistant to BinAB. These larvae do not express the correct receptors at the surface of their intestinal cells. Many other insect species, small crustaceans and humans also lack these receptors, as well as alkaline digestive systems.

    “Part of the appeal is that the larvicide’s safe because it’s so specific, but that’s also part of its limitation,” said Michael Sawaya, a scientist at the University of California, Los Angeles-DOE Molecular Biology Institute and co-author on the paper.

    For public health officials who want to prevent mosquito-borne disease, BinAB could also offer an alternative for controlling certain species of mosquitos that have begun to show resistance to other forms of chemical control.

    Creating a Tailored Insecticide

    The research team already knew the larvicide is composed of a pair of proteins, BinA and BinB, that pair together in crystals and are later activated by larval digestive enzymes.

    In the LCLS experiments, they learned the molecular basis for how the two proteins paired with each other – each performing an important, unique function. Previous research had determined that BinA is the toxic part of the complex, while BinB is responsible for binding the toxin to the mosquito’s intestine. BinB ushers BinA into the cells; once inside, BinA kills the cell.

    The scientists also identified four “hot spots” on the proteins that are activated by the alkaline conditions in the larval gut. All together, they trigger a change from a nontoxic form of the protein to a version that is lethal to mosquito larvae.

    Using the information gathered during the crystallography study, the research team has already begun to engineer a form of the BinAB proteins that will work against more species of mosquitos. This is ongoing work at Institut de Biologie Structurale, UCLA, University of California, Riverside and SLAC.

    Solving the Structure

    Only coarse details were known about the unique three-dimensional structure and biological behavior of BinAB prior to the experiment at LCLS.

    “We chose to look at the BinAB larvicide because it is so widely used, yet the structural details were a mystery,” said Brian Federici, professor of entomology at UC Riverside.

    The small size of the crystals made them difficult to study at conventional X-ray sources. So the research team used genetic engineering techniques to increase the size of the crystals, and the bright, fast pulses of light at LCLS allowed the scientists to collect detailed structural data from the tiny crystals before X-rays damaged their samples.

    The researchers used a crystallography technique called de novo phasing. This involves tagging the crystals with heavy metal markers, collecting tens of thousands of X-ray diffraction patterns, and combining the information collected to obtain a three-dimensional map of the electron density of the protein.

    “This is the first time we’ve used de novo phasing on a crystal of great interest at an X-ray free-electron laser,” said Sebastien Boutet, SLAC scientist.

    The technique had so far only been used on test samples where the structure was already known, in order to prove that it would work.

    “The most immediate need is to now expand the spectrum of action of the BinAB toxin to counter the progression of Zika, in particular,” said Colletier. “BinAB is already effective against Culex [carrier of West Nile encephalitis] and Anopheles [carrier of malaria] mosquitos. With the results of the study, we now feel more confident that we can design the protein to target Aedes mosquitos.”

    Additional contributors to the research include scientists from the Howard Hughes Medical Institutes at UCLA, Lawrence Berkeley National Laboratory, and Stanford University. The Institut de Biologie Structurale is a research center for integrated structural biology funded by the Commissariat à l’Énergie Atomique, the Centre National de la Recherche Scientifique and the Université Grenoble Alpes. The Collaborative Innovation Award program of Howard Hughes Medical Institute (HCIA-HHMI), W.M Keck Foundation, National Institutes of Health, National Science Foundation, France Alzheimer Foundation, Agence Nationale de la Recherche, and DOE Office of Science supported the research.

    See the full article here .

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  • richardmitnick 11:13 am on September 22, 2016 Permalink | Reply
    Tags: , , SLAC LCLS, SLAC’s X-ray Laser Glimpses How Electrons Dance with Atomic Nuclei in Materials   

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


    SLAC Lab

    September 22, 2016

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

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

    SLAC/LCLS
    SLAC/LCLS

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

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

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

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

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

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

    Turning Heat into Electricity and Vice Versa

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

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

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

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

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

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

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

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

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

    Controlling Materials by Stimulating Charged Waves

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

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

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

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

    3
    This movie shows how a laser pulse hitting a chromium crystal causes charge density waves – alternating areas of high and low electron density within the crystal – to oscillate in height, or amplitude. The signal seen here is made by X-ray laser pulses scattering off the crystal. The timescale of the oscillations is shown in picoseconds, or trillionths of a second. (A. Singer/University of California, San Diego)

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

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

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

    A Bright Future for Studies of the Electron-Phonon Dance

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

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

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

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


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

    Citations: M.P. Jiang et al., Nature Communications, 22 July 2016 (10.1038/ncomms12291); A. Singer et al., Physical Review Letters, 25 July 2016 (10.1103/PhysRevLett.117.056401).

    See the full article here .

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  • richardmitnick 11:15 am on September 9, 2016 Permalink | Reply
    Tags: , SLAC LCLS, Snapshots of molecules,   

    From ANL: “Seeing energized light-active molecules proves quick work for Argonne scientists” 

    ANL Lab

    News from Argonne National Laboratory

    September 8, 2016
    Jared Sagoff

    For people who enjoy amusement parks, one of the most thrilling sensations comes at the top of a roller coaster, in the split second between the end of the climb and the rush of the descent. Trying to take a picture at exactly the moment that the roller coaster reaches its zenith can be difficult because the drop happens so suddenly.

    For chemists trying to take pictures of energized molecules, the dilemma is precisely the same, if not trickier. When certain molecules are excited – like a roller coaster poised at the very top of its run – they often stay in their new state for only an instant before “falling” into a lower energy state.

    1
    To understand how molecules undergo light-driven chemical transformations, scientists need to be able to follow the atoms and electrons within the energized molecule as it rides on the energy “roller coaster.”

    In a recent study, a team of researchers at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory, Northwestern University, the University of Washington and the Technical University of Denmark used the ultrafast high-intensity pulsed X-rays produced by the Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility at SLAC National Accelerator Laboratory, to take molecular snapshots of these molecules.

    SLAC/LCLS
    SLAC/LCLS

    By using the LCLS, the researchers were able to capture atomic and electronic arrangements within the molecule that had lifetimes as short as 50 femtoseconds – which is about the amount of time it takes light to travel the width of a human hair.

    “We can see changes in these energized molecules which happen incredibly quickly,” said Lin Chen, an Argonne senior chemist and professor of chemistry at Northwestern University who led the research.

    Chen and her team looked the structure of a metalloporphyrin, a molecule similar to important building blocks for natural and artificial photosynthesis. Metalloporphyrins are of interest to scientists who seek to convert solar energy into fuel by splitting water to generate hydrogen or converting carbon dioxide into sugars or other types of fuels.

    Specifically, the research team examined how the metalloporphyrin changes after it is excited with a laser. They discovered an extremely short-lived “transient state” that lasted only a few hundred femtoseconds before the molecule relaxed into a lower energy state.

    “Although we had previously captured the molecular structure of a longer-lived state, the structure of this transient state eluded our detection because its lifetime was too short,” Chen said.

    When the laser pulse hits the molecule, an electron from the outer ring moves into the nickel metal center. This creates a charge imbalance, which in turn creates an instability within the whole molecule. In short order, another electron from the nickel migrates back to the outer ring, and the excited electron falls back into the lower open orbital to take its place.

    “This first state appears and disappears so quickly, but it’s imperative for the development of things like solar fuels,” Chen said. “Ideally, we want to find ways to make this state last longer to enable the subsequent chemical processes that may lead to catalysis, but just being able to see that it is there in the first place is important.”

    The challenge, Chen said, is to prolong the lifetime of the excited state through the design of the metalloporphyrin molecule. “From this study, we gained knowledge of which molecular structural element, such as bond length and planarity of the ring, can influence the excited state property,” Chen said. “With these results we might be able to design a system to allow us to harvest much of the energy in the excited state.”

    A paper based on the research, “Ultrafast excited state relaxation of a metalloporphyrin revealed by femtosecond X-ray absorption spectroscopy,” was published in the June 10 online edition of the Journal of the American Chemical Society.

    The research was funded by the DOE’s Office of Science and by the National Institute of Health.

    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/.

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  • richardmitnick 7:39 pm on August 29, 2016 Permalink | Reply
    Tags: , SLAC LCLS,   

    From SLAC: “Poof! The Weird Case of the X-ray that Came Out Blank” 


    SLAC Lab

    August 29, 2016

    A ‘Nonlinear’ Effect that Seemingly Turns Materials Transparent is Seen for the First Time in X-rays at SLAC’s LCLS

    1
    An illustration shows what happens in a typical experiment with SLAC’s LCLS X-ray laser, top, versus what happened in this study with an especially intense X-ray pulse. Normally the X-ray pulses — which are shown coming in from the right — scatter off electrons in a sample and produce a pattern in a detector. But when researchers cranked up the intensity of the X-ray pulses, the pulses seemed to go straight through the sample, as if it were not there, and the pattern in the detector vanished. Two recent papers describe and explain this surprising result, which is due to a ‘nonlinear’ effect where particles of X-ray light team up to cause unexpected things to happen. (SLAC National Accelerator Laboratory)

    Imagine getting a medical X-ray that comes out blank – as if your bones had vanished. That’s what happened when scientists cranked up the intensity of the world’s first X-ray laser, at the Department of Energy’s SLAC National Accelerator Laboratory, to get a better look at a sample they were studying: The X-rays seemed to go right through it as if it were not there.

    This result was so weird that the leader of the experiment, SLAC Professor Joachim Stöhr, devoted the next three years to developing a theory that explains why it happened. Now his team has published a paper in Physical Review Letters describing the 2012 experiment for the first time.

    What they saw was a so-called nonlinear effect where more than one photon, or particle of X-ray light, enters a sample at the same time, and they team up to cause unexpected things to happen.

    “In this case, the X-rays wiggled electrons in the sample and made them emit a new beam of X-rays that was identical to the one that went in,” said Stöhr, who is an investigator with the Stanford Institute for Materials and Energy Sciences at SLAC. “It continued along the same path and hit a detector. So from the outside, it looked like a single beam went straight through and the sample was completely transparent.”

    This effect, called “stimulated scattering,” had never been seen in X-rays before. In fact, it took an extremely intense beam from SLAC’s Linac Coherent Light Source (LCLS), which is a billion times brighter than any X-ray source before it, to make this happen.

    SLAC/LCLS
    SLAC/LCLS

    A Milestone in Understanding How Light Interacts with Matter

    The observation is a milestone in the quest to understand how light interacts with matter, Stöhr said.

    “What will we do with it? I think we’re just starting to learn. This is a new phenomenon and I don’t want to speculate,” he said. “But it opens the door to controlling the electrons that are closest to the core of atoms ­– boosting them into higher orbitals, and driving them back down in a very controlled manner, and doing this over and over again.”

    Nonlinear optical effects are nothing new. They were discovered in the1960s with the invention of the laser – the first source of light so bright that it could send more than one photon into a sample at a time, triggering responses that seemed all out of proportion to the amount of light energy going in. Scientists use these effects to shift laser light to much higher energies and focus optical microscopes on much smaller objects than anyone had thought possible.

    The 2009 opening of LCLS as a DOE Office of Science User Facility introduced another fundamentally new tool, the X-ray free-electron laser, and scientists have spent a lot of time since then figuring out exactly what it can do. For instance, a SLAC-led team recently published [Nature Physics] the first report of nonlinear effects produced by its brilliant pulses.

    “The X-ray laser is really a quantum leap, the equivalent of going from a light bulb to an optical laser,” Stöhr said. “So it’s not just that you have more X-rays. The interaction of the X-rays with the sample is very different, and there are effects you could never see at other types of X-ray light sources.”

    “The X-ray laser is really a quantum leap, the equivalent of going from a light bulb to an optical laser,” Stöhr said. “So it’s not just that you have more X-rays. The interaction of the X-rays with the sample is very different, and there are effects you could never see at other types of X-ray light sources.”

    A Most Puzzling Result

    Stöhr stumbled on this latest discovery by accident. Then director of LCLS, he was working with Andreas Scherz, a SLAC staff scientist, who is now with the soon-to-open European XFEL in Hamburg, Germany, and Stanford graduate student Benny Wu to look at the fine structure of a common magnetic material used in data storage.

    To enhance the contrast of their image, they tuned the LCLS beam to a wavelength that would resonate with cobalt atoms in the sample and amplify the signal in their detector. The initial results looked great. So they turned up the intensity of the laser beam in the hope of making the images even sharper.

    That’s when the speckled pattern they’d been seeing in their detector went blank, as if the sample had disappeared.

    “We thought maybe we had missed the sample, so we checked the alignment and tried again,” Stöhr said. “But it kept happening. We knew this was strange – that there was something here that needed to be understood.”

    Stöhr is an experimentalist, not a theorist, but he was determined to find answers. He and Scherz dove deeply into the scientific literature. Meanwhile Wu finished his PhD thesis, which described the experiment and its unexpected result, and went on to a job in industry. But the team held off on publishing their experimental results in a scientific journal until they could explain what happened.

    Stöhr and Scherz published their explanation last fall in Physical Review Letters.

    “We are developing a whole new field of nonlinear X-ray science, and our study is just one building block in this field,” Stöhr said. “We are basically opening Pandora’s box, learning about all the different nonlinear effects, and eventually some of those will turn out to be more important than others.”

    The study included other collaborators from SLAC and Stanford, and was funded by the DOE Office of Science.

    See the full article here .

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  • richardmitnick 10:18 am on August 18, 2016 Permalink | Reply
    Tags: , New X-Ray Matter Interaction Observed at Ultra-High Intensity, SLAC LCLS,   

    From SLAC via DOE: “New X-Ray Matter Interaction Observed at Ultra-High Intensity” 


    SLAC Lab

    1

    Basic Energy Sciences

    Previously unobserved scattering shows unexpected sensitivity to bound electrons, providing new insights into x-ray interactions with matter and opening the door to new probes of matter.

    08.05.16
    David A. Reis
    Stanford PULSE Institute
    dreis@stanford.edu

    1
    Artistic rendering of an intense x-ray beam interacting with metallic beryllium. In the central part of the image, two photons (white lines) interact simultaneously with a single electron of one of the beryllium atoms (sphere), emitting the electron (red streak) and a single higher energy photon (wavy blue line), while leaving the atom in an excited state (purple-blue color). Researchers found that the spectrum of the emitted high-energy photon disagreed with theoretical predictions. Image courtesy of Joel Brehm.

    The Science

    For the first time, researchers explored an extremely rare, but fundamental, process, in which two packets of light called photons scatter simultaneously from a single electron—in this case, from individual atoms in a beryllium metal target. Using the extremely high intensity x-ray laser at the Linac Coherent Light Source, they found that the details of this process deviated dramatically from expectations based on the usual assumption that the electrons behaved as quasi-free in the x-ray interaction.

    SLAC/LCLS
    SLAC/LCLS

    The researchers explain this anomaly in terms of a new x-ray matter interaction that they predict to have unprecedented specificity for light elements, like beryllium.

    The Impact

    In addition to providing new fundamental insights about x-ray interactions, this discovery has broad implications for understanding and controlling the fastest processes in chemical reactivity and energy conversion. The work may lead to powerful new probe techniques at x-ray free electron laser facilities to provide fundamental understanding of ultrafast chemical processes.

    Summary

    The basis for atomic‐scale structure determination involves the scattering of single x‐ray photons, one at a time, from the electrons that make up all materials. Spatial resolution is achieved through a combination of the short wavelength of x-rays and the concentration of the electron density around the individual atoms. For x-ray interactions, these atomic electrons generally behave almost as if they were free. In special cases involving heavy atoms, researchers can achieve simultaneously a level of chemical specificity and spatial resolution, but this is not the case for the lighter atoms that are ubiquitous in most biological and energy-relevant materials. Thus, new methods to achieve chemical specificity for light atoms in structure determination would be revolutionary. In the current work, the researchers used the unprecedented x-ray intensity produced by the Linac Coherent Light Source x-ray laser to observe the concerted nonlinear Compton scattering of two identical hard x-ray photons from the light element beryllium to produce a single higher-energy photon. Not only did the researchers make the first observation of this fundamental process, they also observed an anomalously large shift toward longer wavelengths for the scattered photon. The large wavelength shift is indicative of an interaction that shows properties of scattering from bound (non-free) electrons, which implies that this process could be used as a chemically specific probe. Furthermore, because the nonlinear interaction requires the x-rays to coincide at precisely the same location in time and space, the mechanism is also applicable to studying the fastest processes involving electron motion in chemical reactivity and energy conversion.

    Funding

    This work was supported primarily by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (BES) and the Volkswagen Foundation. Portions of this research were carried out at the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory. Preparatory measurements were carried out at the Stanford Synchrotron Radiation Light Source (SSRL). Both LCLS and SSRL are Office of Science user facilities operated for the U.S. Department of Energy’s Office of Science by Stanford University.
    Publications

    M. Fuchs, et al., Anomalous nonlinear x-ray Compton scattering. Nature Physics 11, 964 (2015). [DOI: 10.1038/nphys3452]

    See the full article here .

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  • richardmitnick 9:21 pm on August 9, 2016 Permalink | Reply
    Tags: , , SLAC LCLS, ,   

    From SLAC: “Perfection in Sight: SLAC Receives New Mirrors for X-ray Laser” 


    SLAC Lab

    August 1, 2016

    The Mirrors Only Differ by One Atom in Flatness From End to End

    1
    SLAC engineer Corey Hardin inspects one of the newly-arrived mirrors in a clean room facility. (SLAC National Accelerator Laboratory)

    2
    May Ling Ng, SLAC engineer, makes adjustments to the mirror restraints during a test of the holding system’s effect on mirror shape. These measurements are needed to maintain the flatness of the mirror within one atom over the entire one-meter length. (SLAC National Accelerator Laboratory)

    Scientists are installing new mirrors to improve the quality of the X-ray laser beam at the Department of Energy’s SLAC National Accelerator Laboratory.

    The meter-long mirrors are the ultimate in flatness, smooth to within the height of one atom or one-fifth of a nanometer.

    If Earth had the same surface, the hills and valleys would only vary by the width of a pencil, says Daniele Cocco, engineering physicist and head of the optics group at SLAC’s Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility.

    SLAC LCLS Inside
    SLAC/LCLS

    Right now, the mirrors are stored in a clean room to avoid dust and prevent damage. Cocco and other engineers only handle the mirrors while wearing gowns, hairnets, masks and gloves. They’re testing the mirrors to see how they will respond to heat and mechanical stress while the beam is running. Both cause tiny deformations on the surface, and even changes as small as half a nanometer can cause big problems.

    Five of these mirrors will be installed in LCLS by the beginning of next year and available for experiments in summer 2017. The new arrivals will join the 12 flat and curved mirrors that currently steer and focus light at LCLS, which is almost one mile long. Eventually, the upgraded mirror system will have a total of 28 mirrors.

    This is the first time the mirrors have been replaced at LCLS. The original mirrors were installed in 2009, when the free-electron laser came online.

    As the laser strikes the mirrors, some degradation of the reflective surface occurs over time. Since the originals were built, there have been improvements in how the mirrors are made, and engineers also better understand how the mirrors can be tailored to the LCLS beam.

    When light hits the reflective surfaces, the photons slant toward a specific point. The X-rays are shaped to the need of the experiment, from a focal spot less than a micron in diameter to as wide as a few millimeters. The beam quality also must be preserved in order to reveal the state of molecules and atoms during a range of processes that occur in biology, chemistry, materials science, and energy.

    “Time is lost when a beam isn’t perfectly uniform, and you’re not able to find the perfect spot on the sample,” Cocco says. “With mirrors this precise, it’s much easier.”

    A Japanese optics company, JTEC Corporation, fabricates the mirrors for synchrotrons and other X-ray laser research facilities such as Japan’s Spring-8 Angstrom Compact Free-Electron Laser (SACLA) and the European X-ray Free-Electron Laser (EXFEL), located in Hamburg, Germany and due to come online in 2017.

    Each mirror is made from an individual silicon crystal, artificially grown in a lab. After the mirror is polished with conventional techniques, the company uses a process called elastic emission machining, where a jet of ultra-pure water containing fine particles removes any remaining imperfections atom by atom.

    Blemishes in the mirror can create imperfections in the X-ray beam.

    “These latest mirrors preserve the beam quality within 97 percent, and the manufacturing technology is continuing to get better,” Cocco says.

    With a coherent laser beam, such as the one at LCLS, photons traveling at fixed wavelengths have a specific relationship to each other.

    “It’s not random. The light propagates as a perfect wave,” Cocco says. “Even minimal bumps alter the properties of the beam, irreversibly destroying the perfection of the wavefront.”

    The light beam also travels over a long distance, which means any disruption can amplify.

    Two of the mirrors will be installed adjacent to the front end of the undulator hall at LCLS. The other three will be located 200 meters further down the beam line, in the X-ray transport tunnel between the near and far halls.

    The mirrors will also be able to handle the higher energy range of LCLS-II, the next generation of SLAC’s X-ray laser.

    SLAC LSLS II new
    SLAC/LCLS-II work at LBL

    1
    SLAC/LCLS-II work at FNAL

    See the full article here .

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  • richardmitnick 5:05 pm on July 15, 2016 Permalink | Reply
    Tags: , New Macromolecular Femtosecond Crystallography (MFX) station at LCLS, SLAC LCLS,   

    From SLAC: “Research Begins at SLAC’s Newest X-ray Laser Experimental Station” 


    SLAC Lab

    July 14, 2016

    In First Study, Berkeley Lab Scientists Use the New Station to Examine Hemoglobin

    1
    Berkeley Lab and SLAC scientists (from left) Jake Koralek, Franklin Fuller, Sheraz Gul, Ernest Pastor and Jan Kern set up their experiment at the Macromolecular Femtosecond Crystallography (MFX) station at LCLS. (SLAC National Accelerator Laboratory)

    2
    SLAC scientists Daniel Damiani and Jason Koglin in the control room of the Macromolecular Femtosecond Crystallography (MFX) station. (SLAC National Accelerator Laboratory)

    A new X-ray laser experimental station at the Department of Energy’s SLAC National Accelerator Laboratory recently welcomed its first research group, scientists from Lawrence Berkeley National Laboratory.

    Members of the Berkeley Lab’s Yachandra/Yano research team ran the inaugural experiment from July 1 to 4. They used the X-ray laser to develop new spectroscopic tools, with an initial focus on studying an enzyme in blood known as hemoglobin. Hemoglobin allows oxygen to be carried around our bodies and gives red blood cells their distinctive color.

    In contrast, Macromolecular Femtosecond Crystallography (MFX) is blaze orange, following the LCLS tradition of personalizing each instrument at SLAC’s Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility. LCLS is a hard X-ray free-electron laser that fires in pulses just a few millionths of a billionth of a second in length, offering a look at chemistry on the natural timescales of reactions.

    MFX is the seventh instrument at LCLS, and is designed to optimize the facility’s ability to investigate the innermost workings of the chemistry and biology that underpin the living world. MFX allows scientists to study complex molecules such as proteins with atomic resolution using a variety of experimental techniques.

    Scientists can take advantage of short X-ray pulses at MFX to limit sample damage during exposure. This can be particularly important, for example, when looking at metal-containing molecules that are more sensitive to damage by radiation.

    During the first experiment at MFX, the Berkeley Lab group studied the distribution of electrons and the bonds between iron and the surrounding atoms within hemoglobin. Many iron-containing enzymes transfer electrons from the iron to an oxygen molecule. This makes both the metal and the oxygen highly active, leading to other important biological reactions, said Franklin Fuller, a postdoctoral researcher at Berkeley Lab.

    “We want to know where these electrons travel throughout the course of the reactions,” said Fuller. “At MFX, we can use an experimental technique – called X-ray emission spectroscopy – that is sensitive to that.”

    Using the capabilities of the X-ray laser, they could look at the chemical changes as the reactions progress. The information collected from hemoglobin experiments can also be useful when examining other iron and metal-containing proteins that are important to both energy production and health.

    Fuller said it can be difficult to measure signals from these proteins, because they exist at very low concentrations. The signals tend to be weak.

    “The goal is to push our ability to examine low concentration samples that represent real-world situations, and that requires the high brilliance, high flux of LCLS,” Fuller said.

    The group was able to collect data with excellent quality, said Jan Kern, a scientist at Berkeley Lab and LCLS. They were able to examine the relationship between the many energies in the X-ray laser beam in each shot and the X-ray spectrum from the iron-containing hemoglobin, as well as some simpler iron compounds.

    “For a first experiment using a brand new beam line, instrument and hutch, data collection went remarkably smoothly,” said Kern. “Although we were nervous about being the first users, everything worked really well. We really appreciate the work done by the LCLS scientists and engineers.”

    The number of proposals for biology experiments at LCLS has rapidly increased during the past few years. MFX will help meet this growing demand by complementing the suite of LCLS instruments already in use for structural biology studies.

    The Berkeley Lab researchers will return to MFX later in July for another experiment, designed to look closely at water splitting during photosynthesis. Learning how water is ‘split’ into protons and oxygen in photosynthetic organisms by using light is critical for designing artificial systems that are important for solar-based renewable energy. The Berkeley Lab researchers are trying to understand the mechanism using simultaneous data collection for X-ray crystallography and X-ray emission spectroscopy. To do this, the researchers built a small conveyor belt to deliver droplets of the liquid samples into the beam line at MFX.

    The new experimental station is designed to handle challenging biological samples that are fundamentally important for medicine, chemistry and energy research. MFX aims to achieve higher throughput and user access with a versatile system that supports a few standard configurations compatible with a broad range of samples.

    Scientists from across SLAC (including LCLS, the Stanford Synchrotron Radiation Lightsource (SSRL) and the Bioscience Division) designed the MFX experimental station in close consultation with the user community. The project is supported by the DOE’s Office of Biological and Environmental Research and Office of Basic Energy Sciences, both part of the DOE Office of Science, in addition to Stanford University and the NIH National Institute of General Medical Sciences.

    See the full article here .

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  • richardmitnick 11:20 am on June 16, 2016 Permalink | Reply
    Tags: Circularly polarized light, Delta undulator, , SLAC LCLS   

    From SLAC: “With Spiraling Light, SLAC X-ray Laser Offers New Glimpses of Molecules” 


    SLAC Lab

    June 15, 2016

    1
    The side-to-side motion of electrons in a beam can be circular, elliptical, or linear, depending on the position of the Delta undulator’s magnet rows. These different motions then create circular, elliptical, or linear polarization in the light pulse. (SLAC National Accelerator Laboratory)

    A new device at the Department of Energy’s SLAC National Accelerator Laboratory allows researchers to explore the properties and dynamics of molecules with circularly polarized, or spiraling, light.

    The use of polarized light is important in the study of many molecules and processes that affect our everyday lives. It can be used to tell the difference between chiral molecules that have “left-handed” and “right-handed” variations, which affects everything from your sense of smell and taste – such as the difference between oranges and lemons, or spearmint and caraway seeds – to life-altering drugs such as thalidomide, in which one version helps ease nausea, but the other can cause abnormal limb growth in unborn children.

    2

    The new Delta undulator produces spiraling X-ray light. (SLAC National Accelerator Laboratory)

    3
    SLAC staff assemble the Delta undulator. (SLAC National Accelerator Laboratory)

    With the new Delta undulator, the Linac Coherent Light Source (LCLS) X-ray laser can now be tailored to look at changes in magnetic materials happening faster than a trillionth of a second, as well as fleeting processes that involve chiral compounds central to areas of biological and chemical research. LCLS is a DOE Office of Science User Facility.

    SLAC/LCLS
    SLAC/LCLS

    “We have already used these X-rays in a couple of studies, and the researchers seemed quite happy with the result,” said James MacArthur, a physics graduate student at Stanford University and part of the SLAC team that built the Delta undulator.

    How Spiraling Light Is Made

    LCLS generates extremely short, bright pulses of X-ray laser light by sending an electron beam through what’s called an undulator. The undulator contains pairs of magnets that force the electrons to wiggle. This motion gives off energy in the form of X-rays, which interact with the electron beam to form laser pulses that can be used for experiments.

    Before the addition of the Delta, the light delivered to experimental stations was always linearly polarized. Polarization refers to the way a light wave vibrates as it travels forward, and linearly polarized light is restricted to one direction. But circularly polarized light vibrates in two directions, producing a pattern like a corkscrew.

    With the Delta, four rows of strong magnets shift to polarize X-rays in a linear, elliptical, or circular fashion.

    3
    5
    Above: Electrons wiggle between two rows of magnets in a traditional undulator, creating X-rays. These X-rays, or light waves, are linearly polarized. Below: With four moving rows of magnets, the Delta undulator can create circularly polarized, or spiraling, light. (SLAC National Accelerator Laboratory)

    Scientists can use the spiraling light to reveal the orientation of molecules in certain materials, and even provide subatomic details as fine as electron distribution and spin.

    Over the past few decades, the ability to control the polarization of light has led to many breakthroughs using optical lasers. Researchers in Italy recently extended this ability into the extreme ultraviolet regime, using the FERMI Free Electron Laser. The beam at LCLS now opens doors to experiments using X-rays, which are able to probe matter in wholly new ways.

    Studies With Spiraling Light

    There are several types of experiments made possible by circularly polarized light. People who study magnetic storage for computing, for example, use spiraling light to watch magnetization changes to develop new methods and materials for faster and more compact storage devices.

    Now, with the power of the world’s strongest X-ray laser, the spiraling light can be delivered in extremely short and intense pulses over a wide range of energies.

    “We can now study the dynamics of ultrafast magnetization in a more substantive and specific way than was previously possible,” said Daniel Higley, an applied physics graduate student at Stanford. Higley is part of the Stanford Institute for Materials and Energy Sciences (SIMES), a joint institute between Stanford and SLAC.

    “One of the key things about using X-rays is that they’re quite specific, tuned to distinct energies. So we can study, in this case, what the magnetization dynamics are for individual chemical elements,” Higley said. “And the short pulses produced by an X-ray laser allow you to take a snapshot of things that happen very fast.”

    The researchers can also gather the needed data quickly. The spiraling light produced by the Delta is nearly 100 percent polarized and orders of magnitude brighter than light produced by any other type of X-ray source with such short pulses. This enables measurement of ultrafast magnetism with unprecedented accuracy and speed. The team described such measurements in a recent Review of Scientific Instruments paper.

    Scientists can also use spiraling light to probe chiral molecules, those with “right-handed” or “left-handed” structures. These subtle differences in arrangement are key to understanding the function of many substances in biological and chemical research, including certain amino acids and sugars, pharmaceuticals and pesticides.

    This light can be used to study how X-rays trigger precise, fleeting changes in chiral molecules like amino acids, and researchers can create snapshots of how radiation damages the molecular building blocks of our bodies.
    Building the Delta

    The first Delta undulator was built at Cornell nearly a decade ago. For the LCLS version, the SLAC team, led by Heinz-Dieter Nuhn, wanted to build a much bigger version of the Cornell prototype.

    But they could not copy the original exactly; it needed adjustments to work at LCLS.

    “We started with some ideas, and found they weren’t as good as we thought,” said Alberto Lutman, head of SLAC’s Delta operations team. “It took us about a year to refine the design and work out the kinks during commissioning. But as a result of all that effort, it’s gotten better and better.”

    Bringing the device up to working condition also required a large collaboration. A Cornell scientist who designed and built the first Delta undulator, Alexander Temnykh, gave input on the blueprint and initial tests. Colleagues at Germany’s DESY and the European X-ray Free-Electron Laser helped provide the measurements needed to calibrate the new equipment.

    One of the design challenges related to size. Researchers at LCLS typically use 30 to 50 meters of undulators to produce a high-quality X-ray beam.

    “The Delta undulator is only 3.2 meters long,” MacArthur said. “So we had to come up with a way to produce a lot of radiation and create a high degree of circular polarization from a short undulator.”

    In a Nature Photonics paper published in May, the Delta team reported that the undulator can produce high-intensity light at nearly 100 percent polarization.

    “It wasn’t known how well the undulator would work as we were developing it,” Lutman said. “It works, and it works nicely.”

    What’s Next for the Delta

    Research and development is underway for multiple Delta-II undulators that will produce spiraling light compatible with the beam of LCLS-II, the next generation of LCLS. LCLS-II will be 10,000 times brighter, on average, than LCLS, enabling high precision studies of even finer aspects of ultrafast magnetism and chirality.

    SLAC/LCLS-II line
    SLAC/LCLS-II line

    The Delta team will develop even more ways to manipulate polarized light. One scheme involves delivering X-rays of different energies and polarizations in a single experiment.

    “The entire Delta team has worked hard to develop a way we can produce circularly polarized light that’s custom-made for research needs,” said Mike Dunne, LCLS director. “We’re excited to be able to offer this new capability to the scientific community.”

    Citations: Lutman et al., Nature Photonics, 09 May 2016 (10.1038/nphoton.2016.79); Higley et al., Review of Scientific Instruments, 22 March 2016 (10.1063/1.4944410).

    See the full article here .

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  • richardmitnick 11:10 am on June 15, 2016 Permalink | Reply
    Tags: , , New X-ray method allows scientists to probe molecular explosions, SLAC LCLS,   

    From ANL: “New X-ray method allows scientists to probe molecular explosions” 

    Argonne Lab
    News from Argonne National Laboratory

    June 15, 2016
    Jared Sagoff

    Summer blockbuster season is upon us, which means plenty of fast-paced films with lots of action. However, these aren’t new releases from Hollywood studios; they’re one type of new “movies” of atomic-level explosions that can give scientists new information about how X-rays interact with molecules.

    A team led by researchers from the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory used the high-intensity, quick-burst X-rays provided by the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory to look at how the atoms in a molecule change when the molecule is bombarded with X-rays.

    SLAC/LCLS
    SLAC/LCLS

    “The LCLS gives us a unique perspective on molecular dynamics because of the extremely brief X-ray pulses that we can use,” said Antonio Picon, an Argonne X-ray scientist and lead author. “We’re able to see how charge and energy can flow through a system with amazing precision.”

    By using a new method called X-ray pump/X-ray probe, the researchers were able to excite a specifically targeted inner-shell electron in a xenon atom bonded to two fluorine atoms. After the electron was excited out of its shell, the unbalanced positive charge in the rest of the molecule caused the molecule to spontaneously dissociate in a process known as “Coulomb explosion.”

    1
    Dynamics of the Coulomb explosion of argon clusters induced by intense femtosecond laser pulses. Kyoto University Institute for Chemical Research

    “The new X-ray pump/X-ray probe technique is so powerful because it allows us to shake the molecule at one point, and look at how it changes at a second point,” said Argonne X-ray scientist and study author Christoph Bostedt.

    The xenon difluoride molecule is only a first step for the technique. In the future, the same X-ray pump/X-ray probe method could find a broad range of applications, such as following the ultrafast structural changes that occur in light-sensitive molecules or the flow of energy in molecules. By understanding intramolecular energy flow, researchers can better develop novel materials to harness the sun’s energy, such as photovoltaics and photocatalysts.

    The new technique could also help researchers address challenges relating to the protein structure determination. For pharmaceutical studies, X-rays are often used to figure out the structures of proteins, but during that process they can also damage parts of them.

    “This technique lets you see how neighboring atoms are affected when certain regions interact with X-rays,” said Stephen Southworth, an Argonne senior X-ray scientist.

    By using an X-ray pump to excite one of the innermost electrons in the molecule, the researchers were able to target one of the electrons that is most central to and characteristic of the molecule. “This technique gives us the ability to take a series of quick snapshots to see what happens when we change a fundamental part of a molecule, and what we learn from it can inform how we approach the interactions between light and molecules in the future,” said Picon.

    The research, which was funded by the DOE Office of Science, involved a collaboration between Argonne, SLAC, and Kansas State University. “For these kinds of studies, you really need a team that combines world leaders in X-ray sources, particle detection and sample manipulation,” Southworth said.

    An article based on the study, Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics, appeared in the May 23 online edition of Nature Communications.

    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/.

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