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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, , X-ray Technology   

    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 12:00 pm on August 13, 2016 Permalink | Reply
    Tags: , , , Light sources, , , X-ray Technology   

    From CERN Courier: “MAX IV paves the way for ultimate X-ray microscope” 

    CERN Courier

    Sweden’s MAX IV facility is the first storage ring to employ a multi-bend achromat. Mikael Eriksson and Dieter Einfeld describe how this will produce smaller and more stable X-ray beams, taking synchrotron science closer to the X-ray diffraction limit.

    Aug 12, 2016

    Mikael Eriksson, Maxlab, Lund, Sweden,
    Dieter Einfeld, ESRF, Grenoble, France.

    1
    http://www.lightsources.org/facility/maxiv

    Since the discovery of X-rays by Wilhelm Röntgen more than a century ago, researchers have striven to produce smaller and more intense X-ray beams. With a wavelength similar to interatomic spacings, X-rays have proved to be an invaluable tool for probing the microstructure of materials. But a higher spectral power density (or brilliance) enables a deeper study of the structural, physical and chemical properties of materials, in addition to studies of their dynamics and atomic composition.

    For the first few decades following Röntgen’s discovery, the brilliance of X-rays remained fairly constant due to technical limitations of X-ray tubes. Significant improvements came with rotating-anode sources, in which the heat generated by electrons striking an anode could be distributed over a larger area. But it was the advent of particle accelerators in the mid-1900s that gave birth to modern X-ray science. A relativistic electron beam traversing a circular storage ring emits X-rays in a tangential direction. First observed in 1947 by researchers at General Electric in the US, such synchrotron radiation has taken X-ray science into new territory by providing smaller and more intense beams.

    Generation game

    First-generation synchrotron X-ray sources were accelerators built for high-energy physics experiments, which were used “parasitically” by the nascent synchrotron X-ray community. As this community started to grow, stimulated by the increased flux and brilliance at storage rings, the need for dedicated X-ray sources with different electron-beam characteristics resulted in several second-generation X-ray sources. As with previous machines, however, the source of the X-rays was the bending magnets of the storage ring.

    The advent of special “insertion devices” led to present-day third-generation storage rings – the first being the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, and the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory in Berkeley, California, which began operation in the early 1990s.

    ESRF. Grenoble, France
    ESRF. Grenoble, France

    2
    LBL/ALS

    Instead of using only the bending magnets as X-ray emitters, third-generation storage rings have straight sections that allow periodic magnet structures called undulators and wigglers to be introduced. These devices consist of rows of short magnets with alternating field directions so that the net beam deflection cancels out. Undulators can house 100 or so permanent short magnets, each emitting X-rays in the same direction, which boosts the intensity of the emitted X-rays by two orders of magnitude. Furthermore, interference effects between the emitting magnets can concentrate X-rays of a given energy by another two orders of magnitude.

    Third-generation light sources have been a major success story, thanks in part to the development of excellent modelling tools that allow accelerator physicists to produce precise lattice designs. Today, there are around 50 third-generation light sources worldwide, with a total number of users in the region of 50,000. Each offers a number of X-ray beamlines (up to 40 at the largest facilities) that fan out from the storage ring: X-rays pass through a series of focusing and other elements before being focused on a sample positioned at the end station, with the longest beamlines (measuring 150 m or more) at the largest light sources able to generate X-ray spot sizes a few tens of nanometres in diameter. Facilities typically operate around the clock, during which teams of users spend anywhere between a few hours to a few days undertaking experimental shifts, before returning to their home institutes with the data.

    Although the corresponding storage-ring technology for third-generation light sources has been regarded as mature, a revolutionary new lattice design has led to another step up in brightness. The MAX IV facility at Maxlab in Lund, Sweden, which was inaugurated in June, is the first such facility to demonstrate the new lattice. Six years in construction, the facility has demanded numerous cutting-edge technologies – including vacuum systems developed in conjunction with CERN – to become the most brilliant source of X-rays in the world.

    3
    Iron-block magnets

    Initial ideas for the MAX IV project started at the end of the 20th century. Although the flagship of the Maxlab laboratory, the low-budget MAX II storage ring, was one of the first third-generation synchrotron radiation sources, it was soon outcompeted by several larger and more powerful sources entering operation. Something had to be done to maintain Maxlab’s accelerator programme.

    The dominant magnetic lattice at third-generation light sources consists of double-bend achromats (DBAs), which have been around since the 1970s.

    DBAs
    4
    MAX IV undulator

    A typical storage ring contains 10–30 achromats, each consisting of two dipole magnets and a number of magnet lenses: quadrupoles for focusing and sextupoles for chromaticity correction (at MAX IV we also added octupoles to compensate for amplitude-dependent tune shifts). The achromats are flanked by straight sections housing the insertion devices, and the dimensions of the electron beam in these sections is minimised by adjusting the dispersion of the beam (which describes the dependence of an electron’s transverse position on its energy) to zero. Other storage-ring improvements, for example faster correction of the beam orbit, have also helped to boost the brightness of modern synchrotrons. The key quantity underpinning these advances is the electron-beam emittance, which is defined as the product of the electron-beam size and its divergence.

    Despite such improvements, however, today’s third-generation storage rings have a typical electron-beam emittance of between 2–5 nm rad, which is several hundred times larger than the diffraction limit of the X-ray beam itself. This is the point at which the size and spread of the electron beam approaches the diffraction properties of X-rays, similar to the Abbe diffraction limit for visible light. Models of machine lattices with even smaller electron-beam emittances predict instabilities and/or short beam lifetimes that make the goal of reaching the diffraction limit at hard X-ray energies very distant.

    Although it had been known for a long time that a larger number of bends decreases the emittance (and therefore increases the brilliance) of storage rings, in the early 1990s, one of the present authors (DE) and others recognised that this could be achieved by incorporating a higher number of bends into the achromats. Such a multi-bend achromat (MBA) guides electrons around corners more smoothly, therefore decreasing the degradation in horizontal emittance. A few synchrotrons already employ triple-bend achromats, and the design has also been used in several particle-physics machines, including PETRA at DESY, PEP at SLAC and LEP at CERN, proving that a storage ring with an energy of a few GeV produces a very low emittance.

    DESY Petra III interior
    DESY Petra III

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    PEP II at SLAC. http://www.sciencephoto.com/media/613/view

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    CERN LEP

    To avoid prohibitively large machines, however, the MBA demands much smaller magnets than are currently employed at third-generation synchrotrons.

    In 1995, our calculations showed that a seven-bend achromat could yield an emittance of 0.4 nm rad for a 400 m-circumference machine – 10 times lower than the ESRF’s value at the time. The accelerator community also considered a six-bend achromat for the Swiss Light Source and a five-bend achromat for a Canadian light source, but the small number of achromats in these lattices meant that it was difficult to make significant progress towards a diffraction-limited source. One of us (ME) took the seven-bend achromat idea and turned it into a real engineering proposal for the design of MAX IV. But the design then went through a number of evolutions. In 2002, the first layout of a potential new source was presented: a 277 m-circumference, seven-bend lattice that would reach an emittance of 1 nm rad for a 3 GeV electron beam. By 2008, we had settled on an improved design: a 520 m-circumference, seven-bend lattice with an emittance of 0.31 nm rad, which will be reduced by a factor of two once the storage ring is fully equipped with undulators. This is more or less the design of the final MAX IV storage ring.

    In total, the team at Maxlab spent almost a decade finding ways to keep the lattice circumference at a value that was financially realistic, and even constructed a 36 m-circumference storage ring called MAX III to develop the necessary compact magnet technology. There were tens of problems that we had to overcome. Also, because the electron density was so high, we had to elongate the electron bunches by a factor of four by using a second radio-frequency (RF) cavity system.

    Block concept

    MAX IV stands out in that it contains two storage rings operated at an energy of 1.5 and 3 GeV. Due to the different energies of each, and because the rings share an injector and other infrastructure, high-quality undulator radiation can be produced over a wide spectral range with a marginal additional cost. The storage rings are fed electrons by a 3 GeV S-band linac made up of 18 accelerator units, each comprising one SLAC Energy Doubler RF station. To optimise the economy over a potential three-decade-long operation lifetime, and also to favour redundancy, a low accelerating gradient is used.

    The 1.5 GeV ring at MAX IV consists of 12 DBAs, each comprising one solid-steel block that houses all the DBA magnets (bends and lenses). The idea of the magnet-block concept, which is also used in the 3 GeV ring, has several advantages. First, it enables the magnets to be machined with high precision and be aligned with a tolerance of less than 10 μm without having to invest in aligning laboratories. Second, blocks with a handful of individual magnets come wired and plumbed direct from the delivering company, and no special girders are needed because the magnet blocks are rigidly self-supporting. Last, the magnet-block concept is a low-cost solution.

    We also needed to build a different vacuum system, because the small vacuum tube dimensions (2 cm in diameter) yield a very poor vacuum conductance. Rather than try to implement closely spaced pumps in such a compact geometry, our solution was to build 100% NEG-coated vacuum systems in the achromats. NEG (non-evaporable getter) technology, which was pioneered at CERN and other laboratories, uses metallic surface sorption to achieve extreme vacuum conditions. The construction of the MAX IV vacuum system raised some interesting challenges, but fortunately CERN had already developed the NEG coating technology to perfection. We therefore entered a collaboration that saw CERN coat the most intricate parts of the system, and licences were granted to companies who manufactured the bulk of the vacuum system. Later, vacuum specialists from the Budker Institute in Novosibirsk, Russia, mounted the linac and 3 GeV-ring vacuum systems.

    Due to the small beam size and high beam current, intra beam scattering and “Touschek” lifetime effects must also be addressed. Both are due to a high electron density at small-emittance/high-current rings in which electrons are brought into collisions with themselves. Large energy changes among the electrons bring some of them outside of the energy acceptance of the ring, while smaller energy deviations cause the beam size to increase too much. For these reasons, a low-frequency (100 MHz) RF system with bunch-elongating harmonic cavities was introduced to decrease the electron density and stabilise the beam. This RF system also allows powerful commercial solid-state FM-transmitters to be used as RF sources.

    When we first presented the plans for the radical MAX IV storage ring in around 2005, people working at other light sources thought we were crazy. The new lattice promised a factor of 10–100 increase in brightness over existing facilities at the time, offering users unprecedented spatial resolutions and taking storage rings within reach of the diffraction limit. Construction of MAX IV began in 2010 and commissioning began in August 2014, with regular user operation scheduled for early 2017.

    On 25 August 2015, an amazed accelerator staff sat looking at the beam-position monitor read-outs at MAX IV’s 3 GeV ring. With just the calculated magnetic settings plugged in, and the precisely CNC-machined magnet blocks, each containing a handful of integrated magnets, the beam went around turn after turn with proper behaviour. For the 3 GeV ring, a number of problems remained to be solved. These included dynamic issues – such as betatron tunes, dispersion, chromaticity and emittance – in addition to more trivial technical problems such as sparking RF cavities and faulty power supplies.

    As of MAX IV’s inauguration on 21 June, the injector linac and the 3 GeV ring are operational, with the linac also delivering X-rays to the Short Pulse Facility. A circulating current of 180 mA can be stored in the 3 GeV ring with a lifetime of around 10 h, and we have verified the design emittance with a value in the region of 300 pm rad. Beamline commissioning is also well under way, with some 14 beamlines under construction and a goal to increase that number to more than 20.

    Sweden has a well-established synchrotron-radiation user community, although around half of MAX IV users will come from other countries. A variety of disciplines and techniques are represented nationally, which must be mirrored by MAX IV’s beamline portfolio. Detailed discussions between universities, industry and the MAX IV laboratory therefore take place prior to any major beamline decisions. The high brilliance of the MAX IV 3 GeV ring and the temporal characteristics of the Short Pulse Facility are a prerequisite for the most advanced beamlines, with imaging being one promising application.

    Towards the diffraction limit

    MAX IV could not have reached its goals without a dedicated staff and help from other institutes. As CERN has helped us with the intricate NEG-coated vacuum system, and the Budker Institute with the installation of the linac and ring vacuum systems, the brand new Solaris light source in Krakow, Poland (which is an exact copy of the MAX IV 1.5 GeV ring) has helped with operations, and many other labs have offered advice. The MAX IV facility has also been marked out for its environmental credentials: its energy consumption is reduced by the use of high-efficiency RF amplifiers and small magnets that have a low power consumption. Even the water-cooling system of MAX IV transfers heat energy to the nearby city of Lund to warm houses.

    The MAX IV ring is the first of the MBA kind, but several MBA rings are now in construction at other facilities, including the ESRF, Sirius in Brazil and the Advanced Photon Source (APS) at Argonne National Laboratory [ANL] in the US.

    ANL APS
    ANL/APS

    The ESRF is developing a hybrid MBA lattice that would enter operation in 2019 and achieve a horizontal emittance of 0.15 nm rad. The APS has decided to pursue a similar design that could enter operation by the end of the decade and, being larger than the ESRF, the APS can strive for an even lower emittance of around 0.07 nm rad. Meanwhile, the ALS in California is moving towards a conceptual design report, and Spring-8 in Japan is pursuing a hybrid MBA that will enter operation on a similar timescale.

    Indeed, a total of some 10 rings are currently in construction or planned. We can therefore look forward to a new generation of synchrotron storage rings with very high transverse-coherent X-rays. We will then have witnessed an increase of 13–14 orders of magnitude in the brightness of synchrotron X-ray sources in a period of seven decades, and put the diffraction limit at high X-ray energies firmly within reach.

    One proposal would see such a diffraction-limited X-ray source installed in the 6.3 km-circumference tunnel that once housed the Tevatron collider at Fermilab, Chicago. Perhaps a more plausible scenario is PETRA IV at DESY in Hamburg, Germany. Currently the PETRA III ring is one of the brightest in the world, but this upgrade (if it is funded) could result in a 0.007 nm rad (7 pm rad) emittance or even lower. Storage rings will then have reached the diffraction limit at an X-ray wavelength of 1 Å. This is the Holy Grail of X-ray science, providing the highest resolution and signal-to-noise ratio possible, in addition to the lowest-radiation damage and the fastest data collection. Such an X-ray microscope will allow the study of ultrafast chemical reactions and other processes, taking us to the next chapter in synchrotron X-ray science.

    Further reading

    E Al-Dmour et al. 2014 J. Synchrotron Rad. 21 878.
    D Einfeld et al. 1995 Proceedings: PAC p177.
    M Eriksson et al. 2008 NIM-A 587 221.
    M Eriksson et al. 2016 IPAC 2016, MOYAA01, Busan, Korea.
    MAX IV Detailed Design Report http://www.maxlab.lu.se/maxlab/max4/index.html.

    See the full article here .

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  • richardmitnick 2:40 pm on August 12, 2016 Permalink | Reply
    Tags: , , X-ray Technology   

    From BNL: “Slicing Through Materials with a New X-ray Imaging Technique” 

    Brookhaven Lab

    August 12, 2016
    Chelsea Whyte,
    cwhyte@bnl.gov
    (631) 344-8671

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

    Images reveal battery materials’ chemical reactions in five dimensions – 3D space plus time and energy

    1
    The chemical phase within the battery evolves as the charging time increases. The cut-away views reveal a change from anisotropic to isotropic phase boundary motion. No image credit

    Researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have created a new imaging technique that allows scientists to probe the internal makeup of a battery during charging and discharging using different x-ray energies while rotating the battery cell. The technique produces a three-dimensional chemical map and lets the scientists track chemical reactions in the battery over time in working conditions. Their work is published in the August 12 issue of Nature Communications.

    Getting an accurate image of the activity inside a battery as it charges and discharges is a difficult task. Often even x-ray images don’t provide researchers with enough information about the internal chemical changes in a battery material because two-dimensional images can’t separate out one layer from the next. Imagine taking an x-ray image of a multi-story office building from above. You’d see desks and chairs on top of one another, several floors of office spaces blending into one picture. But it would be difficult to know the exact layout of any one floor, let alone to track where one person moved throughout the day.

    Getting an accurate image of the activity inside a battery as it charges and discharges is a difficult task. Often even x-ray images don’t provide researchers with enough information about the internal chemical changes in a battery material because two-dimensional images can’t separate out one layer from the next. Imagine taking an x-ray image of a multi-story office building from above. You’d see desks and chairs on top of one another, several floors of office spaces blending into one picture. But it would be difficult to know the exact layout of any one floor, let alone to track where one person moved throughout the day.

    “It’s very challenging to carry out in-depth study of in situ energy materials, which requires accurately tracking chemical phase evolution in 3D and correlating it to electrochemical performance,” said Jun Wang, a physicist at the National Synchrotron Light Source II, who led the research.

    Using a working lithium-ion battery, Wang and her team tracked the phase evolution of the lithium iron phosphate within the electrode as the battery charged. They combined tomography (a kind of x-ray imaging technique that displays the 3D structure of an object) with X-ray Absorption Near Edge Structure (XANES) spectroscopy (which is sensitive to chemical and local electronic changes). The result was a “five dimensional” image of the battery operating: a full three-dimensional image over time and at different x-ray energies.

    To make this chemical map in 3D, they scanned the battery cell at a range of energies that included the “x-ray absorption edge” of the element of interest inside the electrode, rotating the sample a full 180 degrees at each x-ray energy, and repeating this procedure at different stages as the battery was charging. With this method, each three-dimensional pixel—called a voxel—produces a spectrum that is like a chemical-specific “fingerprint” that identifies the chemical and its oxidation state in the position represented by that voxel. Fitting together the fingerprints for all voxels generates a chemical map in 3D.

    The scientists found that, during charging, the lithium iron phosphate transforms into iron phosphate, but not at the same rate throughout the battery. When the battery is in the early stage of charging, this chemical evolution occurs in only certain directions. But as the battery becomes more highly charged, the evolution proceeds in all directions over the entire material.

    “Were these images to have been taken with a standard two-dimensional method, we wouldn’t have been able to see these changes,” Wang said.

    “Our unprecedented ability to directly observe how the phase transformation happens in 3D reveals accurately if there is a new or intermediate phase during the phase transformation process. This method gives us precise insight into what is happening inside the battery electrode and clarifies previous ambiguities about the mechanism of phase transformation,” Wang said.

    Wang said modeling will help the team explore the way the spread of the phase change occurs and how the strain on the materials affects this process.

    This work was completed at the now-closed National Synchrotron Light Source (NSLS), which housed a transmission x-ray microscope (TXM) developed by Wang using DOE funds made available through American Recovery and Reinvestment Act of 2009. This TXM instrument will be relocated to Brookhaven’s new light source, NSLS-II, which produces x-rays 10,000 times brighter than its predecessor. Both NSLS and NSLS-II are DOE Office of Science User Facilities.

    “At NSLS-II, this work can be done incredibly efficiently,” she said. “The stability of the beam lends itself to good tomography, and the flux is so high that we can take images more quickly and catch even faster reactions.”

    This work was supported by the DOE Office of Science.

    See the full article here .

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  • richardmitnick 9:21 pm on August 9, 2016 Permalink | Reply
    Tags: , , , , X-ray Technology   

    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

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

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    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 7:57 pm on August 4, 2016 Permalink | Reply
    Tags: , , , , X-ray Technology   

    From SLAC: “Stanford-led team reveals nanoscale secrets of rechargeable batteries” 


    SLAC Lab

    August 4, 2016
    Andrew Myers

    1
    Artist’s rendition shows lithium-ion battery particles under the illumination of a finely focused X-ray beam. (Image credit: Courtesy Chueh Lab)

    An interdisciplinary team has developed a way to track how particles charge and discharge at the nanoscale, an advance that will lead to better batteries for all sorts of mobile applications.

    Better batteries that charge quickly and last a long time are a brass ring for engineers. But despite decades of research and innovation, a fundamental understanding of exactly how batteries work at the smallest of scales has remained elusive.

    In a paper published this week in the journal Science, a team led by William Chueh, an assistant professor of materials science and engineering at Stanford and a faculty scientist at the Department of Energy’s SLAC National Accelerator Laboratory, has devised a way to peer as never before into the electrochemical reaction that fuels the most common rechargeable cell in use today: the lithium-ion battery.

    By visualizing the fundamental building blocks of batteries – small particles typically measuring less than 1/100th of a human hair in size – the team members have illuminated a process that is far more complex than once thought. Both the method they developed to observe the battery in real time and their improved understanding of the electrochemistry could have far-reaching implications for battery design, management and beyond.

    “It gives us fundamental insights into how batteries work,” said Jongwoo Lim, a co-lead author of the paper and post-doctoral researcher at the Stanford Institute for Materials & Energy Sciences at SLAC. “Previously, most studies investigated the average behavior of the whole battery. Now, we can see and understand how individual battery particles charge and discharge.”

    The heart of a battery

    At the heart of every lithium-ion battery is a simple chemical reaction in which positively charged lithium ions nestle in the lattice-like structure of a crystal electrode as the battery is discharging, receiving negatively charged electrons in the process. In reversing the reaction by removing electrons, the ions are freed and the battery is charged.

    2
    An interdisciplinary research team has developed a new way to track how battery particles charge and discharge. Greatly magnified nanoscale particles are shown here charging (red to green) and discharging (green to red). The animation shows regions of faster and slower charge. (Image credit: SLAC National Accelerator Laboratory)

    These basic processes – known as lithiation (discharge) and delithiation (charge) – are hampered by an electrochemical Achilles heel. Rarely do the ions insert uniformly across the surface of the particles. Instead, certain areas take on more ions, and others fewer. These inconsistencies eventually lead to mechanical stress as areas of the crystal lattice become overburdened with ions and develop tiny fractures, sapping battery performance and shortening battery life.

    “Lithiation and delithiation should be homogenous and uniform,” said Yiyang Li, a doctoral candidate in Chueh’s lab and co-lead author of the paper. “In reality, however, they’re very non-uniform. In our better understanding of the process, this paper lays out a path toward suppressing the phenomenon.”

    For researchers hoping to improve batteries, like Chueh and his team, counteracting these detrimental forces could lead to batteries that charge faster and more fully, lasting much longer than today’s models.

    This study visualizes the charge/discharge reaction in real-time – something scientists refer to as operando – at fine detail and scale. The team utilized brilliant X-rays and cutting-edge microscopes at Lawrence Berkeley National Laboratory’s Advanced Light Source.

    LBL ALS interior
    LBL ALS

    “The phenomenon revealed by this technique, I thought would never be visualized in my lifetime. It’s quite game-changing in the battery field,” said Martin Bazant, a professor of chemical engineering and of mathematics at MIT who led the theoretical aspect of the study.

    Chueh and his team fashioned a transparent battery using the same active materials as ones found in smartphones and electric vehicles. It was designed and fabricated in collaboration with Hummingbird Scientific. It consists of two very thin, transparent silicon nitride “windows.” The battery electrode, made of a single layer of lithium iron phosphate nanoparticles, sits on the membrane inside the gap between the two windows. A salty fluid, known as an electrolyte, flows in the gap to deliver the lithium ions to the nanoparticles.

    “This was a very, very small battery, holding ten billion times less charge than a smartphone battery,” Chueh said. “But it allows us a clear view of what’s happening at the nanoscale.”

    Significant advances

    In their study, the researchers discovered that the charging process (delithiation) is significantly less uniform than discharge (lithiation). Intriguingly, the researchers also found that faster charging improves uniformity, which could lead to new and better battery designs and power management strategies.

    “The improved uniformity lowers the damaging mechanical stress on the electrodes and improves battery cyclability,” Chueh said. “Beyond batteries, this work could have far-reaching impact on many other electrochemical materials.” He pointed to catalysts, memory devices, and so-called smart glass, which transitions from translucent to transparent when electrically charged.

    In addition to the scientific knowledge gained, the other significant advancement from the study is the X-ray microscopy technique itself, which was developed in collaboration with Berkeley Lab Advanced Light Source scientists Young-sang Yu, David Shapiro, and Tolek Tyliszczak. The microscope, which is housed at the Advanced Light Source, could affect energy research across the board by revealing never-before-seen dynamics at the nanoscale.

    “What we’ve learned here is not just how to make a better battery, but offers us a profound new window on the science of electrochemical reactions at the nanoscale,” Bazant said.

    Funding for this work was provided in part by the U.S. Department of Energy, Office of Basic Energy Sciences, and by the Ford-Stanford Alliance. Bazant was a visiting professor at Stanford and was supported by the Global Climate and Energy Project.

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 10:06 am on July 25, 2016 Permalink | Reply
    Tags: , , Electron injector for European XFEL exceeds expectations, , X-ray Technology   

    From XFEL: “Electron injector for European XFEL exceeds expectations” 

    XFEL bloc

    European XFEL

    25 July 2016
    No writer credit found

    First accelerator section successfully tested

    DESY has successfully concluded tests of the first section of the particle accelerator for the European XFEL. The so-called electron injector, which is 30 metres long, performed distinctly better than expected. The injector already completed a whole week under operating conditions. “Having gathered much valuable experience, we are now all set to start up the entire accelerator complex”, reports Winfried Decking, the machine coordinator at DESY. “This is a huge success for the entire accelerator team, together with our international partners.”

    1
    The diagnostic system produces elongated images of individual electron bunches and allows to analyse them in slices. DESY

    The bright X-ray light of the European XFEL is produced by small bunches of high-energy electrons which are brought to speed by a particle accelerator and then sent down an undulating magnetic path. At each magnetic bend in the path, the electron nunches emit X-rays which add up to a laser-like pulse in a self-amplifying manner.

    DESY is the main shareholder of the European XFEL GmbH and responsible, among other things, for building and operating the 2.1-kilometre particle accelerator. The injector is located at the very beginning of the accelerator to which it supplies tailor-made bunches of electrons. The quality of these electron bunches is crucial to the quality of the X-ray laser pulses at the experimental stations, 3.4 kilometres away. One important quality criterion is how narrowly the electron bunches can be focused. “This so-called emittance is some 40 percent better than specified”, reports Decking.

    2
    The injector is 30 metres long. Dirk Nölle / DESY

    Ten times every second, the injector produces a train of up to 2700 short bunches of electrons. To test the quality of the beam, a special diagnostic system picks out individual bunches. “We need only about four bunches per train to analyse the beam”, explains Decking. These bunches are tilted by a cavity before striking the diagnostic screen. The elongated image they leave behind as a result can be used to study the longitudinal structure of each bunch in detail. The analysis reveals the outstanding quality of the bunches.

    In the past seven months, the injector, which produced its first electron beam in December, has given the accelerator team an opportunity to get to know all major subsystems of the entire accelerator facility: “The injector includes all the subsystems that are used in the main accelerator too”, says Decking. “This meant we were able to test and familiarise ourselves with them.” All in all, he says, no major obstacles were encountered throughout the several months of its test operation. The injector went offline on Monday, so that it can be connected to the main accelerator, for which commissioning is planned to start in October 2016. The whole facility is expected to be available for experiments as from the summer of 2017.

    3
    View of DESY’s accelerator control centre, European XFEL section. Dirk Nölle / DESY

    Apart from DESY and European XFEL GmbH, the Centre national de la recherche scientifique CNRS in Orsay (France), the Commissariat à l’énergie atomique et aux énergies alternatives CEA in Saclay (France), the Istituto Nazionale di Fisica Nucleare INFN in Milan (Italy), the Narodowe Centrum Badań Jądrowych in Swierk (Poland), the Wrocław University of Technology WUT in Wrocław (Poland), the Instytut Fizyki Jądrowej IFJ-PAN in Krakow (Poland), the Institute for High-Energy Physics in Protvino (Russia), the Efremov Institute NIIEFA in St. Petersburg (Russia), the Budker Institute for Nuclear Physics BINP in Novosibirsk (Russia), the Institute for Nuclear Research INR in Moscow (Russia), the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas CIEMAT in Madrid (Spain), the Universidad Politécnica de Madrid UPM in Madrid (Spain), the University of Stockholm (Sweden), the University of Uppsala (Sweden), and the Paul Scherrer Institute in Villigen (Switzerland) are also involved in the injector.

    See the full article here .

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    XFEL Campus

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

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

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

    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 7:25 am on June 30, 2016 Permalink | Reply
    Tags: , , , Color, X-ray Technology   

    From Argonne: “X-rays reveal the photonic crystals in butterfly wings that create color” 

    ANL Lab
    News from Argonne National Laboratory

    June 10, 2016 [This just appeared in social media.]
    Louise Lerner


    Access mp4 video here .

    Scientists used X-rays to discover what creates one butterfly effect: how the microscopic structures on the insect’s wings reflect light to appear as brilliant colors to the eye.

    1
    Researchers used powerful X-rays to take a molecular look at how the Kaiser-i-Hind butterfly’s wings reflect in brilliant iridescent green. Image: Shutterstock/Butterfly Hunter.

    2
    When you look very close up at a butterfly wing, you can see this patchwork map of lattices with slightly different orientations (colors added to illustrate the domains). Scientists think this structure, and the irregularities along the edges where they meet, helps create the brilliant “sparkle” of the wings. Image courtesy Ian McNulty/Science

    The results, published today in Science Advances, could help researchers mimic the effect for reflective coatings, fiber optics or other applications.

    We’ve long known that butterflies, lizards and opals all use complex structures called photonic crystals to scatter light and create that distinctive iridescent look. But we knew less about the particulars of how these natural structures grow and what they look like at very, very small sizes—and how we might steal their secrets to make our own technology.

    A powerful X-ray microscope at the Advanced Photon Source, a U.S. Department of Energy Office of Science User Facility, provided just such a view to scientists from the University of California-San Diego, Yale University and the DOE’s Argonne National Laboratory.

    ANL APS
    ANL/APS

    They took a tiny piece of a wing scale from the vivid green Kaiser-i-Hind butterfly, Teinopalpus imperialis, and ran X-ray studies to study the organization of the photonic crystals in the scale.

    At sizes far too small to be seen by the human eye, the scales look like a flat patchwork map with sections of lattices, or “domains,” that are highly organized but have slightly different orientations.

    “This explains why the scales appear to have a single color,” said UC-San Diego’s Andrej Singer, who led the work. “We also found tiny crystal irregularities that may enhance light-scattering properties, making the butterfly wings appear brighter.”

    These occasional irregularities appear as defects where the edges of the domains met each other.

    “We think this may indicate the defects grow as a result of the chirality —the left or right-handedness—of the chitin molecules from which butterfly wings are formed,” said coauthor Ian McNulty, an X-ray physicist with the Center for Nanoscale Materials at Argonne, also a DOE Office of Science User Facility.

    These crystal defects had never been seen before, he said.

    Defects sound as though they’re a problem, but they can be very useful for determining how a material behaves—helping it to scatter more green light, for example, or to concentrate light energy in other useful ways.

    “It would be interesting to find out whether this is an intentional result of the biological template for these things, and whether we can engineer something similar,” he said.

    The observations, including that there are two distinct kinds of boundaries between domains, could shed more light on how these structures assemble themselves and how we could mimic such growth to give our own materials new properties, the authors said.

    The X-ray studies provided a unique look because they are non-destructive—other microscopy techniques often require slicing the sample into paper-thin layers and staining it with dyes for contrast, McNulty said.

    “We were able to map the entire three-micron thickness of the scale intact,” McNulty said. (Three microns is about the width of a strand of spider silk.)

    The wing scales were studied at the 2-ID-B beamline at the Advanced Photon Source. The results are published in an article, Domain morphology, boundaries, and topological defects in biophotonic gyroid nanostructures of butterfly wing scales, in Science Advances. Other researchers on the study were Oleg Shpyrko, Leandra Boucheron and Sebastian Dietze (UC-San Diego); David Vine (Argonne/Berkeley National Laboratory); and Katharine Jensen, Eric Dufresne, Richard Prum and Simon Mochrie (Yale).

    The research was supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences.

    See the full article here .

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

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

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

    Argonne Lab Campus

     
    • Bill 9:19 am on July 10, 2016 Permalink | Reply

      I enjoy what you guys are usually up too. Such clever work
      and reporting! Keep up the superb works guys I’ve included
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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, , X-ray Technology   

    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 .

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

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

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

    Argonne Lab Campus

     
  • richardmitnick 3:29 pm on June 6, 2016 Permalink | Reply
    Tags: , Echo Technique Developed at SLAC Could Make X-ray Lasers More Stable, , X-ray Technology   

    From SLAC: “Echo Technique Developed at SLAC Could Make X-ray Lasers More Stable” 


    SLAC Lab

    June 6, 2016

    1
    A SLAC-led research team manipulated a beam of electrons (from top left to bottom right) with conventional laser light (red) in a way that could produce purer, more stable pulses in X-ray lasers. (SLAC National Accelerator Laboratory)

    Researchers from the Department of Energy’s SLAC National Accelerator Laboratory and Shanghai Jiao Tong University in China have developed a method that could open up new scientific avenues by making the light from powerful X-ray lasers much more stable and its color more pure.

    The idea behind the technique is to “seed” X-ray lasers with regular lasers, whose light already has these qualities.

    “X-ray lasers have very bright, very short pulses that are useful for all sorts of groundbreaking studies,” says SLAC accelerator physicist Erik Hemsing, the lead author of a study published today in Nature Photonics. “But the process that generates those X-rays also makes them ‘noisy’ – each pulse is a little bit different and contains a range of X-ray wavelengths, or colors – so they can’t be used for certain experiments. We’ve now demonstrated a technique that will allow the use of conventional lasers to make stable, single-wavelength X-rays that are exactly the same from one pulse to the next.”

    The method, called echo-enabled harmonic generation (EEHG), could enable new types of experiments, such as more detailed studies of electron motions in molecules.

    2
    Members of the EEHG team. From left: Bryant Garcia, Erik Hemsing, Gennady Stupakov, Tor Raubenheimer and Dao Xiang. (SLAC National Accelerator Laboratory)

    “We need better control over X-ray pulses for such experiments,” says Jerome Hastings, a researcher at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, who was not involved in the study. “The new study demonstrates that EEHG is a very promising method to get us there, and it could become a driver for science that can’t be done today.” LCLS is a DOE Office of Science User Facility.

    SLAC LCLS Inside
    SLAC LCLS Inside

    Planting Seeds of Stability with Conventional Lasers

    The process of generating X-ray laser pulses starts with accelerating bunches of electrons to high energies in linear particle accelerators. The speedy electrons then slalom through a special magnet known as an undulator, where they send out X-rays at every turn.

    Those X-rays, in turn, interact with the electron bunches, rearranging them into thin slices, or microbunches. The electrons in each microbunch collectively emit light that gets further amplified to produce extremely bright pulses of X-ray laser light.

    However, each microbunch of electrons radiates a little bit differently, resulting in X-ray pulses that contain spikes of several wavelengths with different intensities that vary from pulse to pulse. This “noise” poses challenges for applications that require identical X-ray pulses.

    “Optical and other conventional lasers, on the other hand, generate single-color light in a highly reproducible way,” says co-author Bryant Garcia, a graduate student in SLAC’s Accelerator Directorate. “If we could use their regular pulses as ‘seeds’ to form more regular microbunches in the electron beam, the X-ray laser pulses would also be much more uniform and stable.”

    4
    X-ray lasers amplify X-ray pulses (shown within the blue ovals) from electron beams (depicted as arrows) inside magnets known as undulators (left). Top: Each pulse normally contains a spectrum of X-ray colors and intensities that changes from pulse to pulse. Bottom: A technique known as echo-enabled harmonic generation (EEHG) could produce stable pulses containing a single X-ray color that vary very little from shot to shot. (SLAC National Accelerator Laboratory)

    Imprinting Echoes of Laser Light onto X-ray Pulses

    The problem is that wavelengths of conventional laser light are too long to directly seed the electron bunches. To get around that, researchers must shorten the wavelength by creating “harmonics” – light whose wavelength is a fraction of the original laser light.

    “Our study shows for the first time that we can generate the harmonics needed to slice electron bunches finely enough for X-ray laser applications,” Hemsing says.

    In their demonstration experiment at SLAC’s Next Linear Collider Test Accelerator (NLCTA), the researchers shone pairs of laser pulses on electron bunches passing through two magnetic stages, each composed of an undulator and other magnets.

    SLAC Next Linear Collider Test Accelerator (NLCTA)
    SLAC’s Next Linear Collider Test Accelerator (NLCTA)

    The first, optical-wavelength pulse left its “fingerprint” on the electron bunch, while the second, infrared pulse created an “echo” of the first that also contained harmonics.

    Together the laser pulses shuffled the electrons in the bunch so they formed microbunches in a very controlled and reproducible way – stable seeds that could be amplified to produce stable X-rays in future experiments.

    A Technique with Perspective for X-ray Lasers around the World

    The idea for the method was developed in 2009 by SLAC accelerator physicist Gennady Stupakov, one of the study’s co-authors. As a powerful new way of seeding future X-ray lasers, the concept immediately sparked excitement in the global research community. Since then, researchers have been trying to generate higher and higher harmonics, with the goal of reaching X-ray wavelengths of 10 nanometers or less.

    Proof-of-principle experiments at the NLCTA began in 2009 with the demonstration of the 3rd harmonic in 2010, 7th harmonic in 2012 and 15th harmonic in 2014.

    “We’ve now reached the infrared laser’s 75th harmonic, which allows us to produce microbunches able to generate light with a wavelength of 32 nanometers,” Bryant says. “This brings us for the first time within reach of our goal.”

    Although the method has yet to be implemented at an X-ray laser – the team is planning first X-ray EEHG experiments at the FERMI free-electron laser in Trieste, Italy – its benefits for light sources around the world are foreseeable.

    “Since EEHG produces microbunches by using well-defined laser pulses, all electrons emit light of the same color,” Hemsing says. “This has the potential to produce X-ray pulses that are 10 times sharper and brighter, and stable over time.”

    Researchers would also gain more control over X-ray laser pulses. For example, by changing the harmonic in the experiment, scientists could easily tune the color of the X-ray light.

    Other researchers involved in the study were SLAC’s Michael Dunning, Carsten Hast and Tor Raubenheimer, the principal investigator for the EEHG project, as well as Dao Xiang from Shanghai Jiao Tong University in China. The study is the culmination of the six-year program “Accelerator R&D for a Soft X-ray Free-Electron Laser: Echo-Enabled Harmonic Generation,” which was funded by the DOE Office of Science, Basic Energy Sciences. Additional funding sources were the DOE Office of Science, High Energy Physics; the Major State Basic Research Development Program, China; and the National Natural Science Foundation, China.

    4
    From left: Erik Hemsing, Gennady Stupakov and Bryant Garcia at the EEHG demonstration experiment at SLAC’s Next Linear Collider Test Accelerator (NLCTA). (SLAC National Accelerator Laboratory)

    See the full article here .

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