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  • richardmitnick 3:40 pm on June 6, 2016 Permalink | Reply
    Tags: , , Scientists Use a Frozen Gas to Boost Laser Light to New Extremes,   

    From SLAC: “Scientists Use a Frozen Gas to Boost Laser Light to New Extremes” 


    SLAC Lab

    June 6, 2016

    1
    For the experiment, Stanford graduate student Georges Ndabashimiye had to figure out how to freeze argon gas into a thin layer inside a small vacuum chamber chilled to 20 kelvins – close to absolute zero. (SLAC National Accelerator Laboratory)

    SLAC/Stanford Study Opens a Path to Creating Attosecond Laser Pulses by Inducing ‘High Harmonic Generation’ in a Solid

    To observe something as small and fast as an electron rushing to form a chemical bond, you need a bright light with an incredibly small wavelength that comes in very fast pulses – just a few attoseconds, or billionths of a billionth of a second, long.

    Scientists figured out more than a decade ago how to make this specialized form of light through a process known as “high harmonic generation,” or HHG, which shifts laser light to much shorter wavelengths and shorter pulses by shining it through a cloud of gas.

    Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Louisiana State University have achieved an even more dramatic HHG shift by shining an infrared laser through argon gas that’s been frozen into a thin, fragile solid whose atoms barely cling to each other.

    The laser light that emerged from the frozen gas was in the extreme ultraviolet range, with wavelengths about 40 times shorter than the light that went in, they report today in the journal Nature.

    The results give researchers a potential new, solid-state tool for “attosecond science,” which explores processes like the motions of electrons in atoms and the natural vibrations of molecules.

    And in the longer term, they could lead to bright, ultrafast, short-wavelength lasers that are much more compact, and perhaps even electronic devices that operate millions of times faster than current technology, says David Reis, a co-author of the report and deputy director of the Stanford PULSE Institute, a joint institute of SLAC and Stanford.

    Making the First Key Comparisons

    “Now, for the first time, we are able to directly compare how high harmonic generation works in the solid and gaseous forms of a single element. We did this in both argon and krypton,” Reis said.

    “These comparisons should allow us to resolve a number of outstanding questions – for instance, what, exactly, is the effect of packing the atoms closer together? In our study it seemed to enhance the HHG process. We expect that these results, and follow-up studies that are already underway, will give us a much better understanding of the fundamental physics.”

    High harmonic generation is far from new. Discovered in the late 1980s, it offers a way to produce laser-like bursts of light at far higher frequencies and shorter wavelengths than a laser can generate directly. But only in the past decade has it been developed into a readily accessible tool for exploring the attosecond realm.

    Today scientists generally use argon gas as the medium for generating attosecond laser pulses with HHG. Laser light shining on the gas liberates electrons from all the argon atoms it hits. The electrons fly away, loop back and reconnect with their home atoms all at the same time. This reconnection generates attosecond bursts of light that combine to form an attosecond laser pulse.

    Tricky Work with Fragile Crystals

    In 2010, a PULSE team led by Reis and SLAC staff scientist Shambhu Ghimire reported the first observation of HHG in a crystal ­– zinc oxide, a semiconducting material that is probably most familiar as a white powder in sunscreens.

    But it was difficult to compare how HHG proceeds in this complex solid to what happens in a gas. So in 2011 they began a series of experiments to directly compare HHG in gaseous and solid argon.

    “This is a conceptually simple but technically very challenging experiment,” Ghimire says. “Argon crystals are extremely, extremely fragile, and the reason they’re fragile is that the interaction between the atoms is very weak. But this was just what we wanted – something that looked just like a gas, but at higher density.”

    The work of performing the experiment and analyzing the data fell to Georges Ndabashimiye, a graduate student at PULSE and the Stanford Department of Applied Physics, who had to figure out how to freeze argon gas into a thin layer inside a small vacuum chamber chilled to 20 kelvins – close to absolute zero.

    Ndabashimiye says he had to be patient with the challenging process. “I didn’t really know how it was going to turn out, but it kept working and I found I could do more and learn more. That was quite exciting,” he says.

    Looking Toward Potential Applications

    When used to perform HHG, the argon crystal reduced the wavelength of incoming laser light 40-fold, compared to 20-fold in argon gas hit with the same level of illumination. Consequently, it also produced a laser beam of much higher energy – 40 electronvolts, versus 25 electronvolts in argon gas.

    Packing the atoms closer together appears to produce higher harmonics than using single, widely spaced atoms, the researchers said, and working with these frozen gases should help them figure out why.

    There are also many commonalities between the behavior in gases and solids, which leads them to believe that techniques developed for working with gases can be applied to solids, too.

    “If a wide range of different types of solids can produce these attosecond pulses, we might be able to engineer the right solid with the right properties for things like inspecting semiconductor chips and masks, developing new types of microscopy and mapping out how electrons behave inside solids,” Reis said.

    Theorists at Louisiana State University also contributed to the research, which was funded by the DOE Office of Science and the National Science Foundation. The research team also used SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility, to measure the quality of the frozen argon crystals.

    Citation: G. Ndabashimiye et al., Nature, 6 June 2016 (10.1038/nature17660).

    See the full article here .

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

    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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  • richardmitnick 4:48 pm on June 1, 2016 Permalink | Reply
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    From SLAC: “Prototype of LUX-ZEPLIN Dark Matter Detector Tested at SLAC” 


    SLAC Lab

    June 1, 2016

    Researchers Prepare to Build an Ultrasensitive ‘Eye’ for Elusive Form of Matter

    Prototyping of a new, ultrasensitive “eye” for dark matter is making rapid progress at the Department of Energy’s SLAC National Accelerator Laboratory: Researchers and engineers have installed a small-scale version of the future LUX-ZEPLIN (LZ) detector to test, develop and troubleshoot various aspects of its technology.

    1
    Tomasz Biesiadzinski (left, SLAC) and Jeremy Mock (State University of New York/Berkeley Lab) install a miniversion of the future LUX-ZEPLIN (LZ) dark matter detector at a test stand at SLAC. The white container is a prototype of the detector’s core, also known as a time projection chamber (TPC). For the dark matter hunt, LZ’s TPC will be filled with liquid xenon. (SLAC National Accelerator Laboratory)

    2
    SLAC’s Thomas “TJ” Whitis at the test stand for the LZ experiment at SLAC. The TPC prototype is installed inside the cylinder on the left. (SLAC National Accelerator Laboratory)

    When LZ goes online in early 2020 at the Sanford Underground Research Facility in South Dakota, hopes are that it will detect so-called weakly interacting massive particles, or WIMPs.

    SURF logo

    Many researchers believe that these hypothetical particles could make up the dark matter, the invisible substance that accounts for 85 percent of all matter in the universe.

    The detector’s core will be a 5-foot-tall container filled with 10 tons of liquid xenon. When particles pass through it and collide with a xenon atom, the xenon atom emits a flash of light and also releases electrons, which generate a second flash of light. These two consecutive light flashes could represent a characteristic WIMP signal, if all other possible origins have been ruled out.

    3
    The heart of the LZ detector will be a 5-foot-tall time projection chamber (TPC) filled with 10 tons of liquid xenon. Hopes are that hypothetical dark matter particles will produce flashes of light as they traverse the detector. (SLAC National Accelerator Laboratory)

    One particular challenge is to create a strong, stable electric field across the vessel to quickly pull all electrons to the top, where they can be detected. This requires applying high voltages over short distances at the bottom and top of the xenon container. However, it also produces unwanted stray light and can cause damaging electric sparks if not done properly.

    So the SLAC team is now carefully testing the design of the high-voltage system on a 20-inch-tall miniversion of the xenon vessel whose parts were manufactured by Lawrence Berkeley National Laboratory, which manages the LZ project.

    Berkeley Logo

    “We began testing the bottom part last year and have now assembled the entire prototype,” says Kimberly Palladino, an LZ scientist at SLAC and assistant professor at the University of Wisconsin, Madison. “Our goal is to reach high voltages of 100 kilovolts without sparking, demonstrate that the system runs stably over time, and reduce the stray emissions we’ve been observing.”

    4
    Bottom part of the TPC prototype. A high voltage will be applied to the metal grid to generate a strong electric field across the LZ detector. SLAC’s team is carefully testing the design to make sure the high-voltage system is stable and operates properly. (SLAC National Accelerator Laboratory)

    SLAC research associate Tomasz Biesiadzinski says, “In addition, we use our test stand to test all kinds of aspects of LZ, including the cooling system, xenon purification and circulation, control systems and sensors. Researchers from various groups around the world come here, too, to test the equipment they are developing for the experiment.”

    In parallel, SLAC’s team is working on a system to remove an isotope of the chemical element krypton that would cause unwanted signals in the LZ detector from commercially available xenon. The goal: Reach a level of 15 krypton atoms or less per one million billion xenon atoms. Once the design goal has been reached, the researchers will build a large-scale system to purify all 10 tons of xenon needed for the experiment.

    5
    SLAC’s Christina Ignarra (left) and Wing To are working on a system to remove krypton from commercially available xenon. (SLAC National Accelerator Laboratory)

    To learn more about the project, visit the website of SLAC’s LZ team, which is part of the lab’s Particle Astrophysics and Cosmology Division and SLAC’s/Stanford University’s Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). The team works closely with a number of LZ collaborators, including Berkeley Lab, Fermi National Accelerator Laboratory, Texas A&M University, University of Maryland, Oxford University and University of Wisconsin.

    See the full article here .

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  • richardmitnick 4:24 pm on May 27, 2016 Permalink | Reply
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    From SLAC: “SLAC’s New Computer Science Division Teams with Stanford to Tackle Data Onslaught” 


    SLAC Lab

    1
    Alex Aiken, director of the new SLAC Computer Science Division, in the Stanford Research Computing Facility. Built by Stanford on the SLAC campus, this high-performance computing data center opened in 2013; it is used by more than 230 principal investigators and 1,100 students. (SLAC National Accelerator Laboratory)

    Alex Aiken, director of the new Computer Science Division at the Department of Energy’s SLAC National Accelerator Laboratory, has been thinking a great deal about the coming challenges of exascale computing, defined as a billion billion calculations per second. That’s a thousand times faster than any computer today. Reaching this milestone is such a big challenge that it’s expected to take until the mid-2020s and require entirely new approaches to programming, data management and analysis, and numerous other aspects of computing.

    SLAC and Stanford, Aiken believes, are in a great position to join forces and work toward these goals while advancing SLAC science.

    “The kinds of problems SLAC scientists have are at such an extreme scale that they really push the limits of all those systems,” he says. “We believe there is an opportunity here to build a world-class Department of Energy computer science group at SLAC, with an emphasis on large-scale data analysis.”

    Even before taking charge of the division on April 1, Aiken had his feet in both worlds, working on DOE-funded projects at Stanford. He’ll continue in his roles as professor and chair of the Stanford Computer Science Department while building the new SLAC division.

    Solving Problems at the Exascale

    SLAC has a lot of tough computational problems to solve, from simulating the behavior of complex materials, chemical reactions and the cosmos to analyzing vast torrents of data from the upcoming LCLS-II and LSST projects. SLAC’s Linac Coherent Light Source (LCLS), is a DOE Office of Science User Facility.

    SLAC LCLS-II line
    SLAC LCLS-II line

    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST Camera, built at SLAC; LSST telescope, currently under construction at Cerro Pachón Chile

    LSST, the Large Synoptic Survey Telescope, will survey the entire Southern Hemisphere sky every few days from a mountaintop in Chile starting in 2022. It will produce 6 million gigabytes of data per year – the equivalent of shooting roughly 800,000 images with a 8-megapixel digital camera every night. And the LCLS-II X-ray laser, which begins operations in 2020, will produce a thousand times more data than today’s LCLS.

    The DOE has led U.S. efforts to develop high-performance computing for decades, and computer science is increasingly central to the DOE mission, Aiken says. One of the big challenges across a number of fields is to find ways to process data on the fly, so researchers can obtain rapid feedback to make the best use of limited experimental time and determine which data are interesting enough to analyze in depth.

    The DOE recently launched the Exascale Computing Initiative (ECI), led by the Office of Science and National Nuclear Security Administration, as part of a broader National Strategic Computing Initiative. It aims to develop capable exascale computing systems for science, national security and energy technology development by the mid-2020s.

    Staffing up and Enhancing Collaborations

    On the Stanford side, the university has been performing world-class computer science – a field Aiken loosely describes as, “How do you make computers useful for a variety of things that people want to do with them?” – for more than half a century. But since faculty members mainly work through graduate student and postdoctoral researchers, projects tend to be limited to the 3- to 5-year lifespan of those positions.

    The new SLAC division will provide a more stable basis for the type of long-term collaboration needed to solve the most challenging scientific problems. Stanford computer scientists have already been involved with the LSST project, and Aiken himself is working on new exascale computing initiatives at SLAC: “That’s where I’m spending my own research time.”

    He is in the process of hiring four SLAC staff scientists, with plans to eventually expand to a group of 10 to 15 researchers and two initial joint faculty positions. The division will eventually be housed in the Photon Science Laboratory Building that’s now under construction, maximizing their interaction with researchers who use intensive computing for ultrafast science and biology. Stanford graduate students and postdocs will also be an important part of the mix.

    While initial funding is coming from SLAC and Stanford, Aiken says he will be applying for funding from the DOE’s Advanced Scientific Computing Research program, the Exascale Computing Initiative and other sources to make the division self-sustaining.

    Two Sets of Roots

    Aiken came to Stanford in 2003 from the University of California, Berkeley, where he was a professor of engineering and computer science. Before that he spent five years at IBM Almaden Research Center.

    He received a bachelor’s degree in computer science and music from Bowling Green State University in 1983 and a PhD from Cornell in 1988. Aiken met his wife, Jennifer Widom, in a music practice room when they were graduate students (he played trombone, she played trumpet). Widom is now a professor of computer science and electrical engineering at Stanford and senior associate dean for faculty and academic affairs for the School of Engineering. Avid and adventurous travelers, they have taken their son and daughter, both now grown, on trekking, backpacking, scuba diving and sailing trips all over the world.

    The roots of the new SLAC Computer Science Division go back to fall 2014, when Aiken began meeting with two key faculty members – Stanford Professor Pat Hanrahan, a computer graphics researcher who was a founding member of Pixar Animation Studios and has received three Academy Awards for rendering and computer graphics, and SLAC/Stanford Professor Tom Abel, director of the Kavli Institute for Particle Astrophysics and Cosmology, who specializes in computer simulations and visualizations of cosmic phenomena. The talks quickly drew in other faculty and staff, and led to a formal proposal late last year that outlined potential synergies between SLAC, Stanford and Silicon Valley firms that develop computer hardware and software.

    “Modern algorithms that exploit new computer architectures, combined with our unique data sets at SLAC, will allow us to do science that is greater than the sum of its parts,” Abel said. “I am so looking forward to having more colleagues at SLAC to discuss things like extreme data analytics and how to program exascale computers.”

    Aiken says he has identified eight Stanford computer science faculty members and a number of SLAC researchers with LCLS, LSST, the Particle Astrophysics and Cosmology Division, the Elementary Particle Physics Division and the Accelerator Directorate who want to get involved. “We keep hearing from more SLAC people who are interested,” he says. “We’re looking forward to working with everyone!”

    See the full article here .

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  • richardmitnick 12:36 pm on May 23, 2016 Permalink | Reply
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    From SLAC: “Caught on Camera: First Movies of Droplets Getting Blown Up by X-ray Laser” 


    SLAC Lab

    May 23, 2016

    Details Revealed in SLAC Footage Will Give Researchers More Control in X-ray Laser Experiments

    Researchers have made the first microscopic movies of liquids getting vaporized by the world’s brightest X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory. The new data could lead to better and novel experiments at X-ray lasers, whose extremely bright, fast flashes of light take atomic-level snapshots of some of nature’s speediest processes.

    “Understanding the dynamics of these explosions will allow us to avoid their unwanted effects on samples,” says Claudiu Stan of Stanford PULSE Institute, a joint institute of Stanford University and SLAC. “It could also help us find new ways of using explosions caused by X-rays to trigger changes in samples and study matter under extreme conditions. These studies could help us better understand a wide range of phenomena in X-ray science and other applications.”


    Researchers have recorded the first movies of liquids getting vaporized by SLAC’s Linac Coherent Light Source (LCLS), the world’s brightest X-ray laser. The movies reveal new details that could lead to better and novel experiments at X-ray lasers. (SLAC National Accelerator Laboratory)
    Access mp4 video here .

    Liquids are a common way of bringing samples into the path of the X-ray beam for analysis at SLAC’s Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility, and other X-ray lasers. At full power, ultrabright X-rays can blow up samples within a tiny fraction of a second. Fortunately, in most cases researchers can take the data they need before the damage sets in.


    Access the mp4 video here .

    The new study, published* today in Nature Physics, shows in microscopic detail how the explosive interaction unfolds and provides clues as to how it could affect X-ray laser experiments.

    Stan and his team looked at two ways of injecting liquid into the path of the X-ray laser: as a series of individual drops or as a continuous jet. For each X-ray pulse hitting the liquid, the team took one image, timed from five billionths of a second to one ten-thousandth of a second after the pulse. They strung hundreds of these snapshots together into movies.

    “Thanks to a special imaging system developed for this purpose, we were able to record these movies for the first time,” says co-author Sébastien Boutet from LCLS. “We used an ultrafast optical laser like a strobe light to illuminate the explosion, and made images with a high-resolution microscope that is suitable for use in the vacuum chamber where the X-rays hit the samples.”

    The footage shows how an X-ray pulse rips a drop of liquid apart. This generates a cloud of smaller particles and vapor that expands toward neighboring drops and damages them. These damaged drops then start moving toward the next-nearest drops and merge with them.


    This movie shows how a drop of liquid explodes after being struck by a powerful X-ray pulse from LCLS. The vertical white line at the center shows the position of the X-ray beam. The movie captures the first 9 millionths of a second after the explosion. (SLAC National Accelerator Laboratory)
    Access mp4 video here .

    In the case of jets, the movies show how the X-ray pulse initially punches a hole into the stream of liquid. This gap continues to grow, with the ends of the jet on either side of the gap beginning to form a thin liquid film. The film develops an umbrella-like shape, which eventually folds back and merges with the jet.


    Researchers studied the explosive interaction of X-ray pulses from LCLS with liquid jets, as shown in this movie of the first 9 millionths of a second after the explosion. (SLAC National Accelerator Laboratory)
    Access mp4 video here .

    Based on their data, the researchers were able to develop mathematical models that accurately describe the explosive behavior for a number of factors that researchers vary from one LCLS experiment to another, including pulse energy, drop size and jet diameter.

    They were also able to predict how gap formation in jets could pose a challenge in experiments at the future light sources European XFEL in Germany and LCLS-II, under construction at SLAC. Both are next-generation X-ray lasers that will fire thousands of times faster than current facilities.

    European XFEL Test module
    European XFEL Test module

    SLAC LCLS-II line
    SLAC LCLS-II line

    “The jets in our study took up to several millionths of a second to recover from each explosion, so if X-ray pulses come in faster than that, we may not be able to make use of every single pulse for an experiment,” Stan says. “Fortunately, our data show that we can already tune the most commonly used jets in a way that they recover quickly, and there are ways to make them recover even faster. This will allow us to make use of LCLS-II’s full potential.”

    The movies also show for the first time how an X-ray blast creates shock waves that rapidly travel through the liquid jet. The team is hopeful that these data could benefit novel experiments, in which shock waves from one X-ray pulse trigger changes in a sample that are probed by a subsequent X-ray pulse. This would open up new avenues for studies of changes in matter that occur at time scales shorter than currently accessible.

    Other institutions involved in the study were Max Planck Institute for Medical Research, Germany; Princeton University; and Paul Scherrer Institute, Switzerland. Funding was received from the DOE Office of Science; Max Planck Society; Human Frontiers Science Project; and SLAC’s Laboratory Directed Research & Development program.

    *Science paper:
    Liquid explosions induced by X-ray laser pulses

    See the full article here .

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  • richardmitnick 2:42 pm on April 15, 2016 Permalink | Reply
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    From SLAC: “SLAC Researchers Recreate the Extreme Universe in the Lab” 


    SLAC Lab

    April 15, 2016

    Three Recent Studies Reveal Details about Meteor Impacts, Giant Planets and Cosmic Particle Accelerators

    Conditions in the vast universe can be quite extreme: Violent collisions scar the surfaces of planets. Nuclear reactions in bright stars generate tremendous amounts of energy. Gigantic explosions catapult matter far out into space. But how exactly do processes like these unfold? What do they tell us about the universe? And could their power be harnessed for the benefit of humankind?

    To find out, researchers from the Department of Energy’s SLAC National Accelerator Laboratory perform sophisticated experiments and computer simulations that recreate violent cosmic conditions on a small scale in the lab.

    “The field of laboratory astrophysics is growing very rapidly, fueled by a number of technological breakthroughs,” says Siegfried Glenzer, head of SLAC’s High Energy Density Science Division. “We now have high-power lasers to create extreme states of matter, cutting-edge X-ray sources to analyze these states at the atomic level, and high-performance supercomputers to run complex simulations that guide and help explain our experiments. With its outstanding capabilities in these areas, SLAC is a particularly fertile ground for this type of research.”

    Three recent studies exemplify this approach, shining light on meteor impacts, the cores of giant planets and cosmic particle accelerators a million times more powerful than the Large Hadron Collider, the largest particle racetrack on Earth.

    1
    Artist representation of laboratory astrophysics experiments. By mimicking fundamental physics aspects in the lab, researchers hope to better understand violent cosmic phenomena. (SLAC National Accelerator Laboratory)

    Cosmic ‘Bling’ as Marker for Meteor Impacts

    High pressure can turn a soft form of carbon – graphite, used as pencil lead – into an extremely hard form of carbon, diamond. Could the same thing happen when a meteor hits graphite in the ground? Scientists have predicted that it could, and that these impacts, in fact, might be powerful enough to produce a form of diamond, called lonsdaleite, that is even harder than regular diamond.

    “The existence of lonsdaleite has been disputed, but we’ve now found compelling evidence for it,” says Glenzer, the co-principal investigator of a study* published March 14 in Nature Communications.

    The team heated the surface of graphite with a powerful optical laser pulse that set off a shock wave inside the sample and rapidly compressed it. By shining bright, ultrafast X-rays from SLAC’s X-ray laser Linac Coherent Light Source (LCLS) through the sample, the researchers were able to see how the shock changed the graphite’s atomic structure. LCLS is a DOE Office of Science User Facility.

    SLAC/LCLS
    SLAC/LCLS

    “We saw that lonsdaleite formed for certain graphite samples within a few billionths of a second and at a pressure of about 200 gigapascals – 2 million times the atmospheric pressure at sea level,” says lead author Dominik Kraus from the German Helmholtz Center Dresden-Rossendorf, who was a postdoctoral researcher at the University of California, Berkeley at the time of the study. “These results strongly support the idea that violent impacts can synthesize this form of diamond, and that traces of it in the ground could help identify meteor impact sites.”

    2
    Meteor impacts generate shock waves so powerful that they turn graphite into diamond. (NASA/D. Davis)

    Giant Planets Turn Hydrogen into Metal

    A second study**, published today in Nature Communications, looked at another peculiar transformation that might occur inside giant gas planets like Jupiter, whose interior is largely made of liquid hydrogen: At high pressure and temperature, this material is believed to switch from its “normal,” electrically insulating state into a metallic, conducting one.

    “Understanding this process provides new details about planet formation and the evolution of the solar system,” says Glenzer, who was also the co-principal investigator of this study. “Although the transition had already been predicted in the 1930s, we’ve never had a direct window into the atomic processes.”

    That is, not until Glenzer and his fellow scientists performed an experiment at Lawrence Livermore National Laboratory (LLNL), where they used the high-power Janus laser to rapidly compress and heat a sample of liquid deuterium, a heavy form of hydrogen, and to create a burst of X-rays that probed subsequent structural changes in the sample.

    The team saw that above a pressure of 250,000 atmospheres and a temperature of 7,000 degrees Fahrenheit, deuterium indeed changed from a neutral, insulating fluid to an ionized, metallic one.

    “Computer simulations suggest that the transition coincides with the separation of the two atoms normally bound together in deuterium molecules,” says lead author Paul Davis, who was a graduate student at the University of California, Berkeley and LLNL at the time of the study. ”It appears that as the pressure and temperature of the laser-induced shock wave rip the molecules apart, their electrons become unbound and are able to conduct electricity.”

    In addition to planetary science, the study could also inform energy research aimed at using deuterium as nuclear fuel for fusion reactions that replicate analogous processes inside the sun and other stars.

    3
    The interior of giant gas planets like Jupiter is so hot and dense that hydrogen turns into a metal. (NASA; ESA; A. Simon/Goddard Space Flight Center)

    How to Build a Cosmic Accelerator

    In a third example of the extreme universe, tremendously powerful cosmic particle accelerators – near supermassive black holes, for instance – propel streams of ionized gas, called plasma, hundreds of thousands of light-years into space. The energy stored in these streams and in their electromagnetic fields can convert into a few extremely energetic particles, which produce very brief but intense bursts of gamma rays that can be detected on Earth.

    Scientists want to know how these energy boosters work because it would help them better understand the universe. It could also give them fresh ideas for building better accelerators – particle racetracks that are at the heart of a large number of fundamental physics experiments and medical devices.

    Researchers believe one of the main driving forces behind cosmic accelerators could be “magnetic reconnection” – a process in which the magnetic field lines in plasmas break and reconnect in a different way, releasing magnetic energy.

    “Magnetic reconnection has been observed in the lab before, for instance in experiments with two colliding plasmas that were created with high-power lasers,” says Frederico Fiúza, a researcher from SLAC’s High Energy Density Science Division and the principal investigator of a theoretical study*** published March 3 in Physical Review Letters. “However, none of these laser experiments have seen non-thermal particle acceleration – an acceleration not just related to the heating of the plasma. But our work demonstrates that with the right design, current experiments should be able to see it.”

    His team ran a number of computer simulations that predicted how plasma particles would behave in such experiments. The most demanding calculations, with about 100 billion particles, took more than a million CPU hours and more than a terabyte of memory on Argonne National Laboratory’s Mira supercomputer.

    “We determined key parameters for the required detectors, including the energy range they should operate in, the energy resolution they should have, and where they must be located in the experiment,” says the study’s lead author, Samuel Totorica, a PhD student in Tom Abel’s group at Stanford University’s and SLAC’s Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). “Our results are a recipe for the design of future experiments that want to study how particles gain energy through magnetic reconnection.”

    4
    Cosmic particle accelerators, for instance near supermassive black holes, propel streams of ionized gas, called plasma, hundreds of thousands of light-years into space. (NASA/JPL-Caltech)

    Meteor impacts, planetary science and cosmic accelerators are just three of a large number of laboratory astrophysics topics that will be discussed at the 11th International Conference on High Energy Density Laboratory Astrophysics (HEDLA2016), to be held May 16-20 at SLAC.

    Other contributions to the projects described in this feature came from researchers at the GSI Helmholtz Center for Heavy Ion Research, Germany; the Max Planck Institute for the Physics of Complex Systems, Germany; Sandia National Laboratories, Albuquerque; the Technical University Darmstadt, Germany; the University of California, Los Angeles; the University of Oxford, UK; the University of Rostock, Germany; and the University of Warwick, UK. Funding was received from the DOE Office of Science and its Fusion Energy Sciences program. Other funding sources included the Department of Defense; the German Ministry for Education and Research (BMBF); the German Research Foundation (DFG); the National Center for Supercomputing Alliance (NCSA); the National Nuclear Security Administration (NNSA); and the National Science Foundation (NSF).

    *D. Kraus et al., Nature Communications, 14 March 2016 (10.1038/ncomms10970):
    Nanosecond formation of diamond and lonsdaleite by shock compression of graphite
    Science team and affiliations:

    Affiliations

    Department of Physics, University of California, Berkeley, California 94720, USA
    D. Kraus, B. Barbrel & R. W. Falcone
    SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
    A. Ravasio, M. Gauthier, L. B. Fletcher, B. Nagler, E. J. Gamboa, S. Göde, E. Granados, H. J. Lee, W. Schumaker & S. H. Glenzer
    Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
    D. O. Gericke
    Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany
    J. Vorberger
    Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
    J. Vorberger
    Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt, Germany
    S. Frydrych, J. Helfrich, G. Schaumann & M. Roth
    Lawrence Livermore National Laboratory, Livermore, California 94550, USA
    B. Bachmann & T. Döppner
    Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
    G. Gregori
    GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt, Germany
    P. Neumayer

    Contributions

    D.K., R.W.F., B.N., H.J.L., T.D., S.H.G., G.S., D.O.G., J.V., G.G., P.N. and M.R. were involved in the project planning. D.K., A.R., M.G., S.F., J.H., L.B.F., B.N., B. Barbrel, B. Bachmann, E.J.G., S.G., E.G., H.J.L., W.S. and T.D. carried out the experiment. G.S., J.H., S.F., M.R. and D.K. designed and built the samples. Experimental data were analysed and discussed by D.K., S.H.G., A.R., M.G., D.O.G., J.V. and T.D. The manuscript was written by D.K., S.H.G. and D.O.G.

    **P. Davis et al., Nature Communications, 15 April 2016 (10.1038/ncomms11189)
    X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

    Science team and affiliations:

    Affiliations

    University of California, Berkeley, California 94720, USA
    P. Davis & R. W. Falcone
    Lawrence Livermore National Laboratory, PO Box 808, Livermore, California 94551, USA
    P. Davis, T. Döppner, J. R. Rygg, C. Fortmann, L. Divol, A. Pak, P. Celliers, G. W. Collins & O. L. Landen
    University of California, Los Angeles, California 90095, USA
    C. Fortmann
    SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
    L. Fletcher & S. H. Glenzer
    Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
    A. Becker, B. Holst, P. Sperling & R. Redmer
    Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
    M. P. Desjarlais

    Contributions

    P.D., T.D., J.R.R., A.P. and L.F. performed the experiments. P.D., J.R.R. and S.H.G. analysed the data. C.F., A.B., B.H., P.S. and R.R. performed simulations of ionization, dissociation, reflectivity and conductivity; L.D. performed hydrodynamic simulations. P.C., G.W.C., M.P.D., O.L.L., R.W.F., R.R. and S.H.G. provided additional support for experiment design, analysis and interpretation. P.D. and S.H.G. wrote the paper.

    ***S. Totorica et al., Physical Review Letters, 3 March 2016 (10.1103/PhysRevLett.116.095003).
    Nonthermal Electron Energization from Magnetic Reconnection in Laser-Driven Plasmas

    Science team:
    Samuel R. Totorica1,2,3, Tom Abel1,2,4, and Frederico Fiuza3,*

    Affiliations:
    1Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305, USA
    2Department of Physics, Stanford University, Stanford, California 94305, USA
    3High Energy Density Science Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
    4SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

    *fiuza@slac.stanford.edu

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  • richardmitnick 7:20 pm on March 24, 2016 Permalink | Reply
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    From SLAC: “New Catalyst is Three Times Better at Splitting Water” 


    SLAC Lab

    March 24, 2016

    With a combination of theory and clever, meticulous gel-making, scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the University of Toronto have developed a new type of catalyst that’s three times better than the previous record-holder at splitting water into hydrogen and oxygen – the vital first step in making fuels from renewable solar and wind power.

    The research, published today in the journal Science, outlines a potential way to make a future generation of water-splitting catalysts from three abundant metals – iron, cobalt and tungsten – rather than the rare, costly metals that many of today’s catalysts rely on.

    1
    One way to store intermittent sun and wind energy is to use it to split water into oxygen and hydrogen, and then use the hydrogen as fuel. Now scientists at SLAC and the University of Toronto have invented a new type of catalyst that makes this process three times more efficient. In this water-splitting device on the Toronto campus, hydrogen is bubbling up from the left electrode and oxygen is bubbling up from the right one. (Marit Mitchell/University of Toronto)

    “The good things about this catalyst are that it’s easy to make, its production can be very easily scaled up without any super-advanced tools, it’s consistent, and it’s very robust,” said Aleksandra Vojvodic, a SLAC staff scientist with the SUNCAT Center for Interface Science and Catalysis who led the theoretical side of the work.
    Storing Sun and Wind Power

    Scientists have been searching for an efficient way to store electricity generated by solar and wind power so it can be used any time – not just when the sun shines and breezes blow. One way to do that is to use the electrical current to split water molecules into hydrogen and oxygen, and store the hydrogen to use later as fuel.

    This reaction takes place in several steps, each requiring a catalyst – a substance that promotes chemical reactions without being consumed itself – to move it briskly along. In this case the scientists focused on a step where oxygen atoms pair up to form a gas that bubbles away, which has been a bottleneck in the process.

    In previous work, Vojvodic and her SUNCAT colleagues had used theory and computation to look at water-splitting oxide catalysts that contain one or two metals and predict ways to make them more active. For this study, Edward H. Sargent, a professor of electrical and computer engineering at the University of Toronto, asked them to look at the effect of adding tungsten – a heavy, dense metal used in light bulb filaments and radiation shielding – to an iron-cobalt catalyst that worked, but not very efficiently.

    With the aid of powerful computers at SLAC and elsewhere and state-of-the-art computational tools, the SUNCAT team determined that adding tungsten should dramatically increase the catalyst’s activity – especially if the three metals could be mixed so thoroughly that their atoms were uniformly distributed near the active site of the catalyst, where the reaction takes place, rather than separating into individual clusters as they normally tend to do.

    “Tungsten is quite a large atom compared to the other two, and when you add a little bit of it, it expands the atomic lattice, and this affects the reaction not only geometrically but also electronically,” Vojvodic said. “We were able to understand, on the atomic scale, why it works, and then that was verified experimentally.”

    2
    Images of the tiny catalyst particles, made with electron energy loss spectroscopy, show how evenly metal atoms are distributed within the oxide material (Fe=iron, Co=cobalt, W=tungsten and O=oxygen). This extremely uniform distribution helps make the catalyst three times more efficient at splitting water than any previous one. Each frame here is about 4 nanometers wide, which is roughly the width of 40 hydrogen atoms. (B. Zhang et al./Science)

    Add Metal Atoms, Mix and Gel

    Based on that information, Sargent’s team developed a novel way to distribute the three metals uniformly within the catalyst: They dissolved the metals and other ingredients in a solution and then slowly turned the solution into a gel at room temperature, tweaking the process so the metal atoms did not clump together. The gel was then dried into a white powder whose particles were riddled with tiny pores, increasing the surface area where chemicals can attach and react with each other.

    In tests, the catalyst was able to generate oxygen gas three times faster, per unit weight, than the previous record-holder, Sargent said, and it also proved to be stable through hundreds of reaction cycles.

    “It’s a big advance, although there’s still more room to improve,” he said. “”And we will need to make catalysts and electrolysis systems even more efficient, cost effective and high intensity in their operation in order to drive down the cost of producing renewable hydrogen fuels to an even more competitive level.”

    Sargent said the researchers hope to use the same method to develop other three-metal catalysts for splitting water and also for splitting carbon dioxide, a greenhouse gas released by burning fossil fuels, to make renewable fuels and chemical feed stocks. He and five other members of the University of Toronto team have filed for a provisional patent on the technique for preparing the catalyst.

    Future Directions

    “There are a lot of things we further need to understand,” Vojvodic said. “Are there other abundant metals we can test as mixtures in oxides? What are the optimal mixtures of the components? How stable is the catalyst, and how can we scale up its production? It needs to be tested at the device level, really.”

    Jeffrey C. Grossman, a professor of materials science and engineering at MIT who was not involved in the study, said, “The work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage.”

    SLAC research associate Michal Bajdich and Stanford postdoctoral researcher Max García-Melchor also contributed to this work, along with researchers from the DOE’s Brookhaven National Laboratory; East China University of Science & Technology, Tianjin University and the Beijing Synchrotron Radiation Facility in China; and the Canadian Light Source. The research was funded by a number of sources, including the Ontario Research Fund – Research Excellence Program, Natural Sciences and Engineering Research Council of Canada and the CIFAR Bio-Inspired Solar Energy Program, as well as the DOE Office of Science, which funds SUNCAT, and the SLAC Laboratory Directed Research and Development program.

    Citation: B. Zhang et al., Homogeneously dispersed, multimetal oxygen-evolving catalysts,Science, 24 March 2016 (10.1126/science.aaf1525)

    See the full article here .

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  • richardmitnick 1:35 am on November 24, 2015 Permalink | Reply
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    From SLAC: “Atom-sized Craters Make a Catalyst Much More Active” 


    SLAC Lab

    November 23, 2015

    SLAC, Stanford Discovery Could Speed Important Chemical Reactions, Such As Making Hydrogen Fuel

    1
    Illustration of a catalyst being bombarded with argon atoms to create holes where chemical reactions can take place. The catalyst is molybdenum disulfide, or MoS2. The bombardment removed about one-tenth of the sulfur atoms (yellow) on its surface. Researchers then draped the holey catalyst over microscopic bumps to change the spacing of the atoms in a way that made the catalyst even more active. (Charlie Tsai/ Stanford University)

    2
    This electron microscope image of a molybdenum sulfide catalyst shows “holes” left by removing sulfur atoms. Creating these holes and stretching the catalyst to change the spacing of its atoms made the catalyst much more active in promoting chemical reactions. The bright dots are molybdenum atoms; the lighter ones are sulfur. The image measures 4 nanometers on a side. (Hong Li/Stanford Nanocharacterizaton Laboratory)

    Bombarding and stretching an important industrial catalyst opens up tiny holes on its surface where atoms can attach and react, greatly increasing its activity as a promoter of chemical reactions, according to a study by scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory.

    The method could offer a much cheaper way to rev up the production of clean hydrogen fuel from water, the researchers said, and should also apply to other catalysts that promote useful chemical reactions. The study was published Nov. 9 in Nature Materials.

    “This is just the first indication of a new effect, very much in the research stage,” said Xiaolin Zheng, an associate professor of mechanical engineering at Stanford who led the study. “But it opens up totally new possibilities yet to be explored.”

    Finding a Cheap, Abundant Substitute

    Catalysts are substances that promote chemical reactions without being consumed themselves, so they can be used over and over again. Natural catalysts are endlessly at work in plants, animals and our bodies. Industrial catalysts are used to make fuel, fertilizer and consumer products; they’re a multi-billion-dollar industry in their own right.

    The catalyst studied here, molybdenum disulfide or MoS2, helps remove sulfur from petroleum in refineries. But scientists think it might also be a good alternative to platinum as a catalyst for a reaction that joins hydrogen atoms together to make hydrogen gas for fuel.

    “We know platinum is very good at catalyzing this reaction,” said study co-author Jens Nørskov, director of the SUNCAT Center for Interface Science and Catalysis, a joint Stanford/SLAC institute. “But it’s a non-starter because of its rarity. There isn’t enough of it on Earth for large-scale hydrogen fuel production.”

    MoS2 is much cheaper and made of abundant ingredients, and it comes in flexible sheets just one molecule thick, which are stacked together to make catalyst particles, Zheng said. All the catalytic action takes place on the edges of those sheets, where dangling chemical bonds can grab passing atoms and hold them together until they react.

    Researchers have tried all sorts of schemes to increase the active area where this atomic matchmaking goes on. Most of them involve engineering the catalyst sheets to expose more edges, or adding chemicals to make the edges more active.

    A Holey, Stretchy Solution

    In the new approach, Stanford postdoctoral researcher Hong Li used an instrument in the Stanford Nanocharacterization Laboratory to bombard a sheet of MoS2 with argon atoms. This knocked about 1 out of 10 sulfur atoms out of the surface of the sheet, leaving holes surrounded by dangling bonds.

    Then he stretched the holey sheet over microscopic bumps made of silicon dioxide coated with gold. He wet the sheet with a solvent, and when it dried the sheet was permanently deformed: The spacing of the atoms had changed in a way that made the holes much more chemically reactive.

    “Before, the top surface of the sheet was not reactive. It was inert – zero, almost,” Zheng said. “Now the surface is more catalytically active than the edges. And we can tune this activity so the bonds that form on the catalyst are just right – strong enough to hold the reacting atoms in place, but weak enough so they’ll let go of the finished product once the atoms have joined together.”

    SUNCAT theorists, including graduate student Charlie Tsai, played an important role in predicting which combinations of bombarding and stretching would produce the best results, using calculations made with SLAC supercomputers. The researchers said a combination of computation and experiment will be important in finding completely new kinds of active catalytic sites in the future.

    Going forward, Zheng said, “We need to figure out how to do this in the layered catalytic particles that are used in industry, and whether we can apply the same idea to other catalytic materials.”

    They’ll also need to find a better way to make the atom-sized holes, Tsai said. “Bombarding with argon is not practical,” he said. “The procedure is expensive, and it can’t really be scaled up for things like fuel production. So we’ve been working on a follow-up study where we try to replicate the results using a simpler process.”

    Scientists from the Stanford Institute for Materials and Energy Research (SIMES) also played a key role in these experiments. The research was supported by the Samsung Advanced Institute of Technology (SAIT) and Samsung R&D Center America, Silicon Valley, and by SUNCAT and the Center on Nanostructuring for Efficient Energy Conversion at Stanford, both funded by the DOE Office of Science.

    Citation: H. Li et al., Nature Materials, 9 November 2015 (10.1038/nmat4465)

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  • richardmitnick 8:55 am on November 19, 2015 Permalink | Reply
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    From SLAC: “$13.5M Moore Grant to Develop Working ‘Accelerator on a Chip’ Prototype” 


    SLAC Lab

    November 19, 2015

    The Goal: Build a Shoebox-sized Particle Accelerator in 5 Years

    1
    Three “accelerators on a chip” made of silicon are mounted on a clear base. A shoebox-sized particle accelerator being developed under a $13.5 million Moore Foundation grant would use a series of these “accelerators on a chip” to boost the energy of electrons. (SLAC National Accelerator Laboratory)

    2
    A diagram shows one possible configuration for the shoebox-sized particle accelerator prototype. Designing the accelerating chips is just one of the challenges facing the project. The Stanford-led team will have to figure out the best way to distribute laser power among the chips, generate and steer the electrons, shrink the diameter of the electron beam 1,000-fold and a host of other technical details. SLAC and two other national labs will contribute expertise and make their facilities available for this effort. (SLAC National Accelerator Laboratory)

    3
    The accelerator-on-a-chip researchers are testing a variety of materials and structures to find the optimal components for a prototype accelerator. (SLAC National Accelerator Laboratory)

    4
    Much like the computer chips that made Gordon Moore famous, the accelerator on a chip could dramatically shrink the size of accelerator technology to benefit society. (SLAC National Accelerator Laboratory)

    5
    Members of the international scientific collaboration to build a working prototype of a particle accelerator based on “accelerator on a chip” technology gathered at the Moore Foundation in October for a kick-off meeting to discuss the endeavor. (SLAC National Accelerator Laboratory)

    The Gordon and Betty Moore Foundation has awarded $13.5 million to Stanford University for an international effort, including key contributions from the Department of Energy’s SLAC National Accelerator Laboratory, to build a working particle accelerator the size of a shoebox based on an innovative technology known as “accelerator on a chip.”

    This novel technique, which uses laser light to propel electrons through a series of artfully crafted chips, has the potential to revolutionize science, medicine and other fields by dramatically shrinking the size and cost of particle accelerators.

    “Can we do for particle accelerators what the microchip industry did for computers?” said SLAC physicist Joel England, an investigator with the 5-year project. “Making them much smaller and cheaper would democratize accelerators, potentially making them available to millions of people. We can’t even imagine the creative applications they would find for this technology.”

    Robert L. Byer, a Stanford professor of applied physics and co-principal investigator for the project who has been working on the idea for 40 years, said, “Based on our proposed revolutionary design, this prototype could set the stage for a new generation of ‘tabletop’ accelerators, with unanticipated discoveries in biology and materials science and potential applications in security scanning, medical therapy and X-ray imaging.”


    An international team of researchers has begun a 5-year effort to build a working particle accelerator the size of a shoebox based on an innovative technology known as “accelerator on a chip.”
    download mp4 video here.

    The Chip that Launched an International Quest

    The international effort to make a working prototype of the little accelerator was inspired by experiments led by scientists at SLAC and Stanford and, independently, at Friedrich-Alexander University Erlangen-Nuremberg (FAU) in Germany. Both teams demonstrated the potential for accelerating particles with lasers in papers published on the same day in 2013.

    In the SLAC/Stanford experiments, published in Nature, electrons were first accelerated to nearly light speed in a SLAC accelerator test facility. At this point they were going about as fast as they can go, and any additional acceleration would boost their energy, not their speed.

    The speeding electrons then entered a chip made of silica glass and traveled through a microscopic tunnel that had tiny ridges carved into its walls. Laser light shining on the chip interacted with those ridges and produced an electrical field that boosted the energy of the passing electrons.

    In the experiments, the chip achieved an acceleration gradient, or energy boost over a given distance, roughly 10 times higher than the SLAC linear accelerator can provide. At full potential, this means the 2-mile-long linac could be replaced with a series of accelerator chips 100 meters long ­– roughly the length of a football field.

    In a parallel approach, experiments led by Peter Hommelhoff of FAU and published in Physical Review Letters demonstrated that a laser could also be used to accelerate lower-energy electrons that had not first been boosted to nearly light speed. Both results taken together open the door to a compact particle accelerator.

    6
    These microscopic images show some of the accelerator-on-a-chip designs being explored by the international collaboration. In each case, laser light shining on the chip boosts the energy of electrons traveling through it. (Left and middle images: Andrew Ceballos, Stanford University. Right image: Chunghun Lee, SLAC)

    A Tough, High-payoff Challenge

    For the past 75 years, particle accelerators have been an essential tool for physics, chemistry, biology and medicine, leading to multiple Nobel prize-winning discoveries. They are used to collide particles at high energies for studies of fundamental physics, and also to generate intense X-ray beams for a wide range of experiments in materials, biology, chemistry and other fields. But without new technology to reduce the cost and size of high-energy accelerators, progress in particle physics and structural biology could stall.

    The challenges of building the prototype accelerator are substantial, the scientists said. Demonstrating that a single chip works was an important step; now they must work out the optimal chip design and the best way to generate and steer electrons, distribute laser power among multiple chips and make electron beams that are 1,000 times smaller in diameter to go through the microscopic chip tunnels, among a host of other technical details.

    “The chip is the most crucial ingredient, but a working accelerator is way more than just this component,” said Hommelhoff, a professor of physics and co-principal investigator of the project. “We know what the main challenges will be and we don’t know how to solve them yet. But as scientists we thrive on this type of challenge. It requires a very diverse set of expertise, and we have brought a great crowd of people together to tackle it.”

    The Stanford-led collaboration includes world-renowned experts in accelerator physics, laser physics, nanophotonics and nanofabrication. SLAC and two other national laboratories ­– Deutsches Elektronen-Synchrotron (DESY) in Germany and Paul Scherrer Institute in Switzerland – will contribute expertise and make their facilities available for experiments. In addition to FAU, five other universities are involved in the effort: University of California, Los Angeles, Purdue University, University of Hamburg, the Swiss Federal Institute of Technology in Lausanne (EPFL) and Technical University of Darmstadt.

    “The accelerator-on-a-chip project has terrific scientists pursuing a great idea. We’ll know they’ve succeeded when they advance from the proof of concept to a working prototype,” said Robert Kirshner, chief program officer of science at the Gordon and Betty Moore Foundation. “This research is risky, but the Moore Foundation is not afraid of risk when a novel approach holds the potential for a big advance in science. Making things small to produce immense returns is what Gordon Moore did for microelectronics.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 3:23 pm on October 5, 2015 Permalink | Reply
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    From SLAC: “200-terawatt Laser Brings New Extremes in Heat, Pressure to X-ray Experiments” 


    SLAC Lab

    October 5, 2015

    1
    An upgraded high-power laser is designed to synchronize with X-rays for high-temperature, high-pressure experiments in this large chamber, at left. The chamber is in the Matter in Extreme Conditions experimental station at SLAC’s Linac Coherent Light Source X-ray laser. (SLAC National Accelerator Laboratory)

    2
    A view of the large crystal that is integral to a high-power laser system at SLAC’s Matter in Extreme Conditions experimental station at the Linac Coherent Light Source X-ray laser. (SLAC National Accelerator Laboratory)

    3
    Eduardo Granados, a laser scientist at SLAC, inspects a large titanium-sapphire crystal, a key component in a newly upgraded high-power laser system. The laser system is designed to work in conjunction with pulses from SLAC’s Linac Coherent Light Source X-ray laser. (SLAC National Accelerator Laboratory)

    A newly upgraded high-power laser at the Department of Energy’s SLAC National Accelerator Laboratory will blaze new trails across many fields of science by recreating the universe’s most extreme conditions, such as those at the heart of stars and planets, in a lab.

    It is the first high-power laser system to be paired with SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS).

    SLAC LCLS
    LCLS
    SLAC LCLS Inside
    Inside the LCLS

    LCLS can precisely measure extreme forms of matter created by the high-power pulses – with temperatures reaching millions of degrees and pressures approaching 2 billion tons per square inch, about 300 billion times the pressure at sea level – as it rapidly transforms at the atomic scale. The upgraded laser will be useful for studying how materials transform under stress and for understanding the physics of nuclear fusion, which could one day serve as a revolutionary source of energy.

    Scientists can also use its pulses to drive a variety of particle beams that explore forms of matter, such as star-like dense plasmas, in new ways. Plasmas, which are considered a fourth state of matter because they are not like solids, liquids or gases, consist of a gassy soup of charged particles that includes free-floating electrons and the atoms the electrons were stripped away from.

    “This will give us more insight into the processes at work, from the atomic to electronic states,” said Eduardo Granados, a laser scientist at SLAC who oversaw the upgrade.

    The upgraded laser system is designed to reach a peak of 200 terawatts of power, seven times higher than its previous peak and equivalent to about 100 times the world’s total power consumption compressed into tens of femtoseconds, or quadrillionths of a second. Its peak power before the upgrade was 30 terawatts. The laser’s pulses are now far more powerful than the total combined pulse power of the more than 150 other laser systems in operation at SLAC.

    New Ways to Probe Materials

    Even though SLAC’s upgraded laser is not the most powerful in the world – a laser completed in Japan this year now holds the record, with roughly 10 times higher power, and many other laser systems around the globe are several times more powerful – what makes it unique is its ability to synchronize with the intense, ultrafast X-ray pulses produced at LCLS, a DOE Office of Science User Facility.

    The growth in these high-power laser systems around the globe opens new avenues for discovery and has excited interest among researchers working in astrophysics, materials research, planetary sciences, geology, and nuclear and energy sciences, among other fields. On Sept. 30, an international symposium organized by the Science Council of Japan met at SLAC to discuss the latest developments in using high-power lasers and X-ray lasers to study matter at extreme conditions, and similar discussions are planned during a two-day High-Power Laser Workshop this week at SLAC and during an upcoming lab-based astrophysics conference at SLAC.

    SLAC’s high-power laser emits light pulses at invisible, near-infrared frequencies that push samples to extreme conditions; the X-ray laser then probes their properties with incredible precision. Both laser systems can produce pulses measured in femtoseconds, and the timing delay between the high-power and X-ray pulses can be adjusted to study how materials rapidly transform after they are hit by the high-power laser pulse.

    The high-power laser can also be used to simultaneously generate beams of particles such as gamma rays, protons and a specialized form of X-rays called betatron radiation all of which can be used in concert with LCLS pulses to explore exotic states of matter in new ways.

    “We will now have a much more accurate picture of what’s happening in high-energy X-ray laser experiments,” Granados said.

    Opportunity for Future Upgrades

    At the core of SLAC’s upgraded laser system, which is housed at the Matter in Extreme Conditions experimental station at LCLS, is a large, high-quality titanium-sapphire crystal, measuring more than 3 inches in diameter. The crystal stimulates and amplifies light from another laser. That amplified light is focused down to a spot just millionths of an inch across, and timing systems help to synch the arrival of each laser pulse with an LCLS X-ray laser pulse with a precision measured in femtoseconds.

    The upgraded high-power laser at LCLS will be available to scientists during the next round of experiments at LCLS, which begins in October, at half of its designed peak power, 100 terawatts. The plan is to gradually ramp up its intensity over time toward regular operation at 200 terawatts, Granados said. The laser will initially be able to fire one pulse every 3.5 minutes at 100 terawatts, with a pulse length of about 40 femtoseconds. At its peak power of 200 terawatts, it will fire one shot every seven minutes.

    Granados said the laser system can eventually be upgraded further, up to 300 terawatts and perhaps as high as 400 terawatts, with additional equipment.

    Even before the upgrade the laser system was used for a first-of-a-kind LCLS experiment that used its pulse to produce a secondary surge of X-rays in the form of betatron X-rays. Those betatron X-rays, which cover a broader energy range than the LCLS pulses and were produced by accelerating high-energy electrons with laser light, were used to reveal more details about the samples.

    “These betatron X-rays are a promising source for future experiments that we now want to test at higher energies,” Granados said.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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