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  • richardmitnick 4:30 pm on December 19, 2017 Permalink | Reply
    Tags: , , CERN Large Hadron Collider, , , , , Large Electron-Positron Collider, , , , SLAC LCLS, ,   

    From Symmetry: “Machine evolution” 

    Symmetry Mag

    Amanda Solliday

    Courtesy of SLAC

    Planning the next big science machine requires consideration of both the current landscape and the distant future.

    Around the world, there’s an ecosystem of large particle accelerators where physicists gather to study the most intricate details of matter.

    These accelerators are engineering marvels. From planning to construction to operation to retirement, their lifespans stretch across decades.

    But to get the most out of their investments of talent and funding, laboratories planning such huge projects have to think even longer-term: What could these projects become in their next lives?

    The following examples show how some of the world’s big physics machines have evolved to stay at the forefront of science and technology.

    Same tunnel, new collisions

    Before CERN research center in Geneva, Switzerland, had its Large Hadron Collider, it had the Large Electron-Positron Collider. LEP was the largest electron-positron collider ever built, occupying a nearly 17-mile circular tunnel dug beneath the border of Switzerland and France. The tunnel took three years to completely excavate and build.

    The first particle beam traveled around the LEP circular collider in 1989. Long before then, the international group of CERN physicists and engineers were already thinking about what CERN’s next machine could be.

    “People were saying, ‘Well, if we do build LEP, then we should make it compatible with the [then-proposed] Large Hadron Collider,’” says James Gillies, a senior communications advisor and member of the strategic planning and evaluation unit at CERN. “If you want to have a future facility, you often have to engage the people who just finished designing one machine to start thinking about the next one.”

    LEP’s designers chose an energy for the collider that would mass-produce Z bosons, fundamental particles discovered by earlier experiments at CERN. The LHC would be a step up from LEP, reaching higher energies that scientists hoped could produce the Higgs boson. In the 1960s, theorists proposed the Higgs as a way to explain the origin of the mass of elementary particles. And the new machine to look for it could be built in the same 17-mile tunnel excavated for LEP.

    Engineers began working on the LHC while LEP was still running. The new machine required enlargements to underground areas—it needed bigger detectors and new experimental halls.

    “That was challenging because these caverns are huge. As they were being excavated, the pressure on the LEP tunnel was reduced and the LEP beamline needed realignment,” Gillies says. “So you constantly had to realign the collider for experiments as you were digging.”

    After LEP reached its highest energy in 2000, it was switched off. The tunnel remained the same, says Gillies, but there were many other changes. Only one of the LEP detectors, DELPHI, remains underground at CERN as a visitors’ point.

    In 2012, LHC scientists announced the discovery of the long-sought Higgs boson. The LHC is planned to continue running until at least 2035, gradually increasing the intensity of its particle collisions. The research and development into the accelerator’s successor is already happening. The possibilities include a higher energy LHC, a compact linear collider or an even larger circular collider.


    Large Electron-Positron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 1989
    Link to LEP Timeline: Timeline
    Courtesy of CERN


    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Large Hadron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 2008
    Link to LHC Timeline: Timeline
    Courtesy of CERN

    High-powered science
    Decades before the LHC came into existence, a suburb of Chicago was home to the most powerful collider in the world: the Tevatron. A series of accelerators at Fermi National Accelerator Laboratory boosted protons and antiprotons to nearly the speed of light. In the final, 4-mile Tevatron ring, the particles reached record energy levels, and more than 1000 superconducting magnets steered them into collisions. Physicists used the Tevatron to make the first direct measurement of the tau neutrino and to discover the top quark, the last observed lepton and quark, respectively, in the Standard Model.

    The Tevatron shut down in 2011 after the LHC came up to speed, but the rest of Fermilab’s accelerator infrastructure was still hard at work powering research in particle physics—particularly on the abundant, mysterious and difficult-to-detect neutrino.

    Starting in 1999, a brand-new, 2-mile circular accelerator called the Main Injector was added to the Fermilab complex to increase the number of Tevatron particle collisions tenfold. It was joined in its tunnel by the Recycler, a permanent magnet ring that stored and cooled antiprotons.

    But before the Main Injector was even completed, scientists had identified a second purpose: producing powerful beams of neutrinos for experiments in Illinois and 500 miles away in Minnesota.

    FNAL/NOvA experiment map

    By 2005, the proton beam circulating in the Main Injector was doing double duty: sending ever-more-intense beams to the Tevatron collider and smashing into a target to produce neutrinos. Following the shutdown of the Tevatron, the Recycler itself was recycled to increase the proton beam power for neutrino research.

    “I’m still amazed at how we are able to use the Recycler. It can be difficult to transition if a machine wasn’t originally built for that purpose,” says Ioanis Kourbanis, the head of the Main Injector department at Fermilab.

    Fermilab’s high-energy neutrino beam is already the most intense in the world, but the laboratory plans to enhance it with future improvements to the Main Injector and the Recycler, and to build a brand-new neutrino beamline.

    Neutrinos almost never interact with matter, so they can pass straight through the Earth on their way to detectors onsite and others several hundred miles away. Scientists hope to learn more about neutrinos and their possible role in shaping our early universe.

    The new beamline will be part of the Long-Baseline Neutrino Facility, which will send neutrinos 800 miles underground to the massive, mile-deep detectors of the Deep Underground Neutrino Experiment.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA

    Scientists from around the world will use the DUNE data to answer questions about neutrinos, thanks to the repurposed pieces of the Fermilab accelerator complex.


    FNAL Tevatron

    FNAL/Tevatron map

    FNAL/Tevatron DZero detector

    FNAL/Tevatron CDF detector

    Location: Fermilab—Batavia, Illinois
    First beam: 1983
    Link to Tevatron Timeline: Timeline
    Courtesy of Fermilab


    Neutrinos at the Main Injector (NuMI) beam
    Location: Fermilab—Batavia, Illinois
    First beam: 2004
    Link to Fermilab Timeline: Timeline
    Courtesy of Fermilab

    A monster accelerator

    When physicists first came up with the idea to build a two-mile linear accelerator at what is now called SLAC National Accelerator Laboratory, managed by Stanford University, they called it “Project M” for “Monster.” Engineers began building it from hand-drawn designs. Once completed, the machine was able to accelerate electrons to near the speed of light, producing its first particle beam in May 1966.

    SLAC Campus

    The accelerator’s scientific purpose has gone through several iterations of particle physics experiments over the decades, from fixed-target experiments to the Stanford Linear Collider (the only electron-positron linear collider ever built) to an injector for a circular collider, the Positron-Electron Project.

    These experiments led to the discovery that protons are made of quarks, the first evidence that the charm quark existed (through observations of the J/psi particle, co-discovered with researchers at MIT) and the discovery of the tau lepton.

    In 2009, the lab used the accelerator as the backbone for a different type of science machine—an X-ray free-electron laser, the Linac Coherent Light Source.

    “Looking around, SLAC was the only place in the world with a linear accelerator capable of driving a free-electron laser,” says Claudio Pellegrini, a distinguished professor emeritus of physics at the University of California, Los Angeles and a visiting scientist and consulting professor at SLAC. Pellegrini first proposed the idea to transform SLAC’s linear accelerator.

    The new machine, a DOE Office of Science user facility, would be the world’s first laser of its kind that could produce extremely bright hard X-rays, the high-energy X-rays that let scientists take snapshots of atoms and molecules.

    “Much of the physics and many of the tools learned and developed during the operation of the Stanford Linear Collider were directly applicable to the free electron laser,” says Lia Merminga, head of the accelerator directorate at SLAC. “This was a big factor in the LCLS being commissioned in record time. Without the Stanford Linear Collider experience, this significant body of work would have to be reinvented and reproduced almost from scratch.”

    Little about the accelerator itself needed to change. But to create a free-electron laser, scientists needed to design a new part: an electron gun, a device that generates electrons to be injected into the accelerator. A collaboration of several national labs and UCLA created a new type of electron gun for LCLS, while other national labs helped build undulators, a series of magnets that would wiggle the electrons to create X-rays.

    LCLS used only the last third of SLAC’s original linear accelerator. In part of the remaining section, scientists are developing plasma wakefield and other new particle acceleration techniques.

    For the X-ray laser’s next iteration, LCLS-II, scientists are aiming for an even brighter laser that will fire 1 million pulses per second, allowing them to observe rare and exceptionally transient events.


    To do this, they will need to replace the original copper structures with superconducting technology. The technology is derived from designs for a large International Linear Collider [ILC] proposed to be built in Japan.

    ILC schematic

    “I’m in awe of the foresight of the original builders of SLAC’s linear accelerator,” Merminga adds. “We’ve been able to do so much with this machine, and the end is not yet in sight.”


    Fixed target and collider experiments

    Location: SLAC—Menlo Park, California
    First beam: 1966
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC


    Linac Coherent Light Source
    Location: SLAC—Menlo Park, California
    First beam: 2009
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:40 pm on December 18, 2017 Permalink | Reply
    Tags: , , Major Technology Developments Boost LCLS X-Ray Laser’s Discovery Power, , SLAC LCLS,   

    From SLAC: “Major Technology Developments Boost LCLS X-Ray Laser’s Discovery Power” 

    SLAC Lab

    December 18, 2017
    Manuel Gnida

    Smart computer programs improve the efficiency of X-ray laser operations and optimizations, allowing increased experimental time and potentially leading to new types of experiments. (Terry Anderson/SLAC National Accelerator Laboratory)

    Innovations at SLAC, including the world’s shortest X-ray flashes, ultra-high-speed pulse trains and smart computer controls, promise to take ultrafast X-ray science to a whole new level.

    Accelerator experts at the Department of Energy’s SLAC National Accelerator Laboratory are developing ways to make the most powerful X-ray laser better than ever. They have created the world’s shortest X-ray pulses for capturing the motions of electrons, as well as ultra-high-speed trains of X-ray pulses for “filming” atomic motion, and have developed “smart” computer programs that maximize precious experimental time.

    With its X-rays a billion times brighter than those available before, SLAC’s Linac Coherent Light Source (LCLS) has already revolutionized the field of ultrafast science and has opened new avenues for research in chemistry, biology and materials science. The new developments enhance the X-ray laser’s capabilities even further.


    “Creating new capabilities for LCLS is a very important ongoing effort at SLAC,” said Axel Brachmann, head of the Linac and FEL Division of the lab’s Accelerator Directorate, at the 2017 SSRL/LCLS Users’ Meeting in September, where some of these developments were presented. “Our engineers and scientists are working hard to push the limits of what’s technologically possible and to make sure that SLAC stays a world leader in X-ray science.”

    Snapshots in Billionths of a Billionth of a Second

    Two methods independently invented by scientists in SLAC’s Accelerator Directorate have produced the world’s first attosecond hard X-ray laser pulses at the lab’s LCLS facility. In one method, the shapes of electron bunches used to generate X-rays were manipulated with a radiofrequency field so that part of each bunch (dense area on the left) emits X-ray pulses with shorter-than-ever pulse lengths. (Yuantao Ding/SLAC National Accelerator Laboratory)

    LCLS’s discovery power is packed into extremely bright flashes of X-ray light, each lasting only a few femtoseconds – millionths of a billionth of a second. Like a strobe light that freezes motions too fast to see with the naked eye, these flashes capture images of atomic nuclei rapidly jiggling around in molecules and materials. But researchers would like to go further and film the even faster motions of an atom’s electrons.

    “These ultrafast motions are very fundamental because they set the stage for all the slower processes,” says staff scientist Yuantao Ding. “However, they occur in less than a femtosecond, and we need a faster ‘camera’ to capture them.”

    Two SLAC teams, led by Ding and fellow accelerator physicist Agostino Marinelli, have now made an important step in that direction. They demonstrated two independent methods for the generation of X-ray pulses of a few hundred attoseconds, or billionths of a billionth of a second, setting a record for X-ray lasers.

    Both groups manipulated the tightly packed bunches of electrons that fly through a special set of magnets, called an undulator, to generate LCLS X-ray pulses. They tweaked the bunches so only part of each bunch emitted X-ray laser light – resulting in a much shorter pulse length.

    “This is a major step forward, and actually uses relatively simple methods of generating attosecond pulses of X-rays with relatively high energy,” Marinelli says. “To take this even further, LCLS users want to use softer X-rays to allow them to study an atom’s outer electrons, which are the ones involved in chemical reactions. It turns out creating soft X-ray attosecond pulses is a much more complex process.”

    That’s why Marinelli and others are working on a third method, called X-ray Laser-Enhanced Attosecond Pulses (XLEAP). In this approach the electron bunches interact with an infrared laser inside the undulator and are chopped up into thin slices. Simulations suggest that this method, which is currently being tested at LCLS, can produce soft X-ray pulses that are only 500 attoseconds long.

    New Ways of Filming Atoms with Multiple X-ray Flashes

    This illustration shows how three X-ray pulses with different energies, or colors, are generated with the fresh-slice technique from a single electron bunch traversing three separate sections of a special magnet, called an undulator. (Greg Stewart/SLAC National Accelerator Laboratory)

    To make movies of ultrafast processes at LCLS, researchers use the pump-probe technique, in which they hit a sample with a “pump” pulse from a conventional laser to trigger an atomic response and then examine the response with a “probe” pulse from the X-ray laser. By varying the amount of time between the two pulses, they can create a stop-action movie that shows how the sample’s atomic structure changes over time.

    This works well as long as the process, such as the breaking of a chemical bond in a molecule, can be initiated with a conventional laser emitting visible, infrared or ultraviolet light. However, some reactions can only be set off by the higher energies of X-ray light pulses.

    In principle, these experiments could be done at LCLS now, but the time between pulses would limit studies to processes slower than 8 milliseconds. Even with the future LCLS-II upgrade, which will “fire” up to a million pulses per second, this limit would still be a microsecond. Therefore, accelerator physicists are inventing methods that generate ultra-high-speed trains of X-ray flashes for the exploration of much faster processes.

    “SLAC is testing and implementing a number of multi-pulse techniques for X-ray pump-probe experiments with soft and hard X-rays, such as the split-undulator, twin-bunch, fresh-slice and two-bucket schemes,” says staff scientist Alberto Lutman. “Together they cover a broad range of very short pulse delays – from zero delay, meaning the pump and probe X-ray pulses hit the sample at the same time, to delays of just a few femtoseconds, and then all the way to more than 100 nanoseconds between pulses.”

    Lutman is spearheading the development of the fresh-slice technique, in which the head, tail and center of a single electron bunch can produce separate X-ray pulses in separate sections of the undulator. “This is an extremely flexible method,” he says. “It lets us finely vary the delay between the pulses, and it also allows us to tweak the color and polarization of each X-ray pulse individually.”

    Experiments with pulses of multiple colors, or X-ray energies, can, for example, enhance details in studies of the 3-D atomic structures and functions of molecules, such as medically important proteins. The fresh-slice method has also the potential to boost the power of extremely short X-ray pulses, and it has been used in seeding techniques that improve X-ray laser performance by making its light less noisy.

    Most of the multi-pulse methods have been demonstrated for rapid sequences of two or three X-ray flashes, but the use of even more pulses is on the horizon. A team led by accelerator physicist Franz-Josef Decker is currently working on a technique that uses multiple laser pulses for the generation of trains of up to eight X-ray pulses. This would allow researchers to follow the complex evolution of how a material responds to high-pressure shocks, for example in the study of meteorite collisions.

    ‘Smart’ Control of a Complex Discovery Machine

    Underpinning all of the above research is the need to find new ways of running LCLS in the most efficient way so more experiments can be accommodated. The facility is one of only five hard X-ray lasers operating in the world, and access to it is extremely competitive. One path to increasing the amount of experimental time is to minimize the time spent tuning the machine to meet the needs of specific experiments.

    “Each year we spend many hours optimizing the machine, which involves tedious adjustments of a large number of LCLS magnets,” says SLAC staff scientist Daniel Ratner. “We want to automate this procedure to free time for the activities that actually require human involvement.”

    Until about a year ago, he says, all fine-tuning was done manually. Now it’s done with the aid of computers, which has already cut the optimization time in half. But the lab’s accelerator experts want to take automation to the next level by using a type of artificial intelligence known as “machine learning” – an approach where “smart” computer programs learn from past X-ray laser optimizations instead of repeating the same routine every time.

    “This will lead to significant additional time savings,” says accelerator physicist Joseph Duris, who leads the machine learning initiative of SLAC’s Accelerator Directorate. “Smarter optimization algorithms will also help us explore completely new LCLS configurations to prepare for future experiments.”

    Last but not least, machine learning will help the lab efficiently operate two complex X-ray lasers side by side when the LCLS-II upgrade is complete.

    Financial support for this research was provided by the DOE Office of Science. Parts of these projects are supported by DOE’s Laboratory Directed Research and Development (LDRD) Program. To enhance LCLS performance and create new capabilities, SLAC’s Accelerator Directorate partners with X-ray instrument scientists of the LCLS Directorate and other groups across the lab, as well as with many members of the LCLS user community. LCLS is a DOE Office of Science user facility.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

  • richardmitnick 4:54 pm on December 10, 2017 Permalink | Reply
    Tags: , , , , Bridgmanite, , Could super-Earths host geology similar to Earth’s?, Exogeology, Institute of Laser Engineering Osaka University, Laboratoire d' Optique Appliquee Palaiseau France, National Ignition Facility at Lawrence Liver­more National Laboratory in California, , Sandia Z machine, SLAC LCLS   

    From SA: “The Labs That Forge Distant Planets Here on Earth” 

    Scientific American

    Scientific American

    December 10, 2017
    Shannon Hall

    Could super-Earths such as the one depicted here host geology similar to Earth’s? Credit: NASA Ames, JPL-Caltech, T. Pyle

    Yingwei Fei and his colleagues had spent a month carefully crafting the three slivers of dense silicate—shiny and round, each sample was less than a millimetre thick. But in early November, it was time to say goodbye. Fei carefully packed the samples, plus a few back-ups, in foam and shipped them from Washington DC to Albuquerque, New Mexico. There, the Z Pulsed Power Facility at Sandia National Laboratories will soon send 26 million amps surging towards the slivers, zapping them, one by one, into dust.

    Sandia Z machine

    The Z machine can replicate the extreme conditions inside detonating nuclear weapons. But Fei, a high-pressure experimental geologist at the Carnegie Institution for Science’s Geophysical Laboratory in Washington DC, has a more otherworldly goal in mind: he hopes to explore how bridgmanite, a mineral found deep beneath Earth’s surface, would behave at the higher temperatures and pressures found inside larger rocky planets beyond the Solar System.

    The experiment is one small contribution to exogeology: a research area that is bringing astronomers, planetary scientists and geologists together to explore what exoplanets might look like, geologically speaking. For many scientists, exogeology is a natural extension of the quest to identify worlds that could support life. Already, astronomers have discovered thousands of exoplanets and collected some of their vital statistics, including their masses and radii. Those that orbit in the habitable, or ‘Goldilocks’, zone—a region around the host star that is temperate enough for water to exist in liquid form—are thought to be particularly life-friendly.

    But Earth has a lot more going for it than its size, mass and favourable orbit, says Cayman Unterborn, an exogeologist at Arizona State University in Tempe. Its churning molten core, for example, creates and sustains a magnetic field that shields the planet’s fragile atmosphere from the solar wind. And the motion of tectonic plates helps regulate global temperatures, by cycling carbon dioxide between rocks and the atmosphere. Exoplanet discoveries keep pouring in. But astronomers are “just now realizing, ‘Well wait, we want to understand these systems a lot more than just stamp collecting’”, Unterborn says. “Bringing geology into the mix is a natural factor.”

    Researchers are using simulations and experiments, such as Fei’s at the Z machine, to learn what kinds of exoplanet might have Earth-like geology. The work could help researchers prioritize which exoplanets to study.

    But the field faces several challenges, not least that mystery still surrounds much of Earth’s geology—such as how and when tectonic activity first began. “It’s a fundamental discovery that changed geology,” says Richard Carlson, a geochemist at the Carnegie Institution. “But we still don’t know why it works the way it does.” What’s more, confirming that an exoplanet actually boasts Earth-like geology could be difficult; astronomers rarely observe these planets directly, and if they do, the planet might be the size of a single pixel in their image.

    Even indirect evidence—or the smallest suggestion—of geological activity could give researchers a more complete picture of these distant worlds, and which ones are the best candidates to search for indications of life. “It’s like if you came across a giant crime scene with very little evidence,” says Sara Seager, an astrophysicist at the Massachusetts Institute of Technology in Cambridge. “You work your hardest to take what little evidence there was and try to piece it together somehow.”

    Turning outwards

    One of the most exciting targets of exoplanetary science has been super-Earths. These rocky planets—with as many as ten times Earth’s mass—have no parallel in the Solar System. But they are now known to be quite common in the Galaxy and, because many are fairly big, they could make easier targets for detailed observation than Earth-sized planets.

    Early studies of super-Earth geology, published about ten years ago, examined what these planets would look like if they were simply scaled-up versions of Earth. But the scorching-hot planet 55 Cancri e, first spotted in 2004, underscored the idea that super-Earths could be quite different. Observations in 2011 revealed the planet to have roughly twice Earth’s radius and a little more than eight times its mass, yielding an average density only marginally higher than Earth’s—and that presented a conundrum.

    If 55 Cancri e had an iron core and silicate mantle, like Earth, it should be more massive given its size. An ocean wrapped around the whole planet would bring 55 Cancri e’s density down to Earth-like levels. But the planet is too hot for water to survive for long; it orbits so close to its host star that the day-side temperature is roughly 2,500 kelvin.

    A resolution came in 2012, when Nikku Madhusudhan, an astronomer then at Yale University in New Haven, Connecticut, and his colleagues decided to take a fresh approach. Previous research had suggested that the planet’s host star has a much higher ratio of carbon to oxygen than the Sun. Stars and their planets are built from the same swirling disk of dust and gas, so it seemed fair to assume that 55 Cancri e would also be carbon-rich. When Madhusudhan accounted for this carbon in his model of the planet’s interior, it produced a match with the mass and radius of the world. “That was a revelation,” says Madhusudhan, now at the University of Cambridge, UK. And such a world would be truly alien. Madhusudhan suspects that its crust could be dominated by graphite; inside the planet, the pressure would probably crush vast amounts of the element into diamond. “It would look pretty radical compared with what we see in the Solar System,” he says.

    A planet made of diamond would fire up the imagination, although 55 Cancri e’s host star might not actually contain as much carbon as thought. Even if it did, astronomers caution against assuming that a planet’s composition matches that of its host star. Seager notes that this idea wouldn’t account well for the variety of planets in the Solar System. “At this point, it’s a reasonable inference, but I think it’s important to realize that it’s not iron-clad,” says Gregory Laughlin, an astronomer at Yale.


    Exogeologists have embraced this uncertainty, and are trying their best to pin down how distant worlds form and evolve. To get from a list of starting elements to geology, scientists need to know what minerals form, when they melt and how their density changes with pressure and temperature. Those data can be used to simulate how a planet develops from an undifferentiated, molten ball into a layered structure, with minerals forming—and sinking or floating—as the planet cools. “We can build up a mineralogical, let’s say, onion-skin model of what the planet would look like initially,” says Wim van Westrenen, a geologist at the Free University of Amsterdam. Then, he says, researchers can use numerical models to predict how that planet will evolve and whether the migration of materials will be enough to drive plate tectonics.

    To gather information to feed these models, geologists are starting to subject synthetic rocks to high temperatures and pressures to replicate an exoplanet’s innards—as Fei and his colleagues are doing. Although the goal of these experiments is new, the approach is not. For decades, experimental petrologists have built instruments to simulate the conditions of Earth’s interior, anywhere from a few centimetres below the surface to Earth’s core. Many use a device called a diamond anvil cell. This apparatus squeezes materials by pushing the blunted tips of two gem-quality diamonds together. While a sample is under pressure, a laser can be used to heat it. At the same time, experimentalists can bombard the mat­erial with X-rays to investigate its crystalline structure and explore how the material changes as it is pushed to high temperatures and pressures.

    Groups including Sang-Heon Dan Shim, a mineral physicist at Arizona State University, and his colleagues have used this process to squeeze carbon-rich samples that might reflect the composition of 55 Cancri e. The work has revealed how planets dominated by carbon-containing compounds called carbides might transport heat, and how they might differ from planets that, like Earth, are dominated by silicates.

    Carbon is not the only element of interest. Unterborn points to magnesium, silicon and iron as “the big three” that will affect a planet’s bulk structure, influencing how heat flows in the mantle and the relative size of the planet’s core—and so the presence of plate tectonics and a global magnetic field, respectively. Ratios of these elements vary widely in stars. The Sun has one magnesium atom for every silicon atom; in other stars, that ratio ranges from 0.5 to 2. The difference might seem small, but if the same ratios are present in planets, they could drastically affect geology.

    Most textbooks argue that magnesium-rich rocks would be softer than those containing high concentrations of silicon—so much so that walking on a magnesium-rich world might feel like walking on mud. Shim’s diamond-anvil-cell work on rocks with various magnesium-to-silicon ratios suggests these worlds could also boast deeper reservoirs of magma than a silicon-rich planet and, as a result, more catastrophic volcanoes. But Shim notes that other parameters, such as the concentration of water in minerals, must also be taken into account.

    High pressure

    With two diamonds, Shim can apply no more than 400 gigapascals of pressure, a little higher than the pressure in Earth’s core. To probe the interiors of super-Earths, he has turned to the world’s brightest X-ray laser: the Linac Coherent Light Source at SLAC National Accelerator Laboratory in Menlo Park, California.


    The instrument can generate shocks inside the sample, producing pressures as high as 600 giga­pascals—enough to simulate the cores of planets twice as massive as Earth.

    Geologists are also using other large facilities to probe potential exoplanet formulations. The Z machine can reach 1,000 gigapascals—the condition expected inside planets nearly three times Earth’s mass. Laser facilities in Palaiseau, France, and Osaka, Japan, can reach a similar range.

    Laboratoire d’ Optique Appliquee, Palaiseau, France

    Institute of Laser Engineering, Osaka University

    And some researchers have turned to the National Ignition Facility at Lawrence Liver­more National Laboratory in California, which is used to study nuclear fusion and can subject samples to as much as 5,000 giga­pascals, the pressure of Jupiter’s deep interior.


    These experiments are still in their preliminary stages, as researchers compete for time at these facilities and slowly accumulate data on a variety of basic compounds.

    At the end of the day, exogeologists hope to find the right combination of elements to build exoplanets with Earth-like geologies. “I would like to identify the compositional Goldilocks zone,” says Wendy Panero, a geologist at the Ohio State University in Columbus. “What is the not-too-soft, not-too-stiff habitable zone for rock composition?”

    The answer might not be clear-cut. Even perfect knowledge of composition might not tell exogeologists much about the state of a planet. Earth, for example, did not host plate tectonics in its early history, and it is not expected to do so forever. And its neighbour Venus shows how widely planetary evolution can diverge. The planet’s mass, radius, composition and distance from the Sun are similar to those of Earth. But Earth supports life, whereas Venus, swaddled in a haze of carbon dioxide, is quite dead. Stephen Mojzsis, a geologist at the University of Colorado Boulder, suspects that the loss of plate tectonics on Earth will eventually cause it to resemble its super-heated sibling. “It’s inevitable,” he says. “We’re just not sure when that will happen.” So, although most early exoplanet models are focusing on composition, exogeologists might ultimately have to include additional factors such as billions of years of planetary evolution.

    Some expect that this work will help astronomers determine which planets to target in the search for life. If scientists know the conditions needed to sustain a magnetic field for billions of years, or the proportions of elements required to drive convection in the mantle, they could advise their colleagues to scrutinize the worlds that meet those criteria. Then astronomers could turn powerful telescopes, such as NASA’s James Webb Space Telescope, slated to launch in 2019, towards those planets to search their atmospheres for potential signatures of alien life.

    It might also be possible to spot geological activity from a distance. A transient spike in atmospheric sulfur, for example, might be indirect evidence of the presence of an active volcano. Changes in reflectivity as a planet rotates might hint at the presence of continents and oceans, which could also suggest tectonic activity.

    Already, there has been talk of a possible detection of volcanic activity—on 55 Cancri e.

    55 Cancri e

    In 2016, Brice-Olivier Demory, an astronomer at the University of Bern, and his colleagues published the first heat map of the planet, created using NASA’s infrared Spitzer Space Telescope.


    NASA/Spitzer Infrared Telescope

    The planet is tidally locked to its star, so one hemisphere is eternally bathed in sunlight and the other is dark. The planet should be hottest closest to the star, but Demory and his colleagues discovered that the hottest point seems to be offset. They posited that flowing lava is carrying heat away (although more recent work has argued that winds might be responsible instead).

    It’s clear that 55 Cancri e is no place for life. But other worlds may be much more inviting. Earlier this year, Unterborn completed a study that looked at more than 1,000 Sun-like stars. Using their compositions, he determined that one-third of those stars could host planets whose crust was dense enough to sink into the mantle—a process that might let plate tectonics thrive for billions of years.

    Although researchers are just the beginning to explore the geology of exoplanets, Carlson notes that the study of these worlds has already yielded a number of surprises, not least evidence of planets that seem to have undergone dramatic migrations from their original orbits. This discovery caused astronomers to rethink the Solar System’s evolution, and theorize that similar movements could have helped carry materials, such as water ice, to Earth. “I don’t think humans are anywhere near as imaginative and creative as nature is,” Carlson says. “So, understanding the diversity of what’s out there will just open our eyes to other possibilities. And it’s those other possibilities that will help us understand our situation better.”

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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

  • richardmitnick 10:55 pm on November 27, 2017 Permalink | Reply
    Tags: , , SLAC LCLS, SLAC-led Study Shows Potential for Efficiently Controlling 2-D Materials With Light,   

    From SLAC: “SLAC-led Study Shows Potential for Efficiently Controlling 2-D Materials With Light” 

    SLAC Lab

    November 27, 2017
    Manuel Gnida

    In experiments with the lab’s ultrafast ‘electron camera,’ laser light hitting a material is almost completely converted into nuclear vibrations, which are key to switching a material’s properties on and off for future electronics and other applications.

    Simulation of a laser pulse’s effect on two layers of molybdenum diselenide. (Hiroyuki Kumazoe/USC)

    Materials that are only a few atomic layers thick have generated a lot of excitement in recent years. These 2-D materials can have intriguing properties, such as extraordinary mechanical strength and superior electrical and heat conductivity, and could benefit a number of next-generation applications, including flexible electronics, data storage devices, solar cells, light-emitting diodes and chemical catalysts. Researchers also think they may be able to customize the properties of these materials by using light pulses to rapidly switch them from one state, or phase, to another, for example from an insulating to a conducting state.

    However, the ability to do this depends on how efficiently the light’s energy is transferred to the material’s atomic nuclei. Now, a team led by researchers from the Department of Energy’s SLAC National Accelerator Laboratory has demonstrated for the first time that the energy transfer is very fast and extremely efficient.

    “Our data show that essentially all of the light energy gets converted into vibrations of the material’s atomic nuclei within a trillionth of a second,” says SLAC’s Ming-Fu Lin, the lead author of a study published Nov. 23 in Nature Communications. “This efficient energy conversion is crucial, because those nuclear motions can initiate what we call a phase transition in the material – a change that alters its properties.”

    The researchers looked at a sample made of two layers of molybdenum diselenide – a model system for 2-D materials that can potentially be switched from a semiconducting state to a metal state and vice versa. They first hit the sample with a very brief laser pulse and then observed how its energy spread into the material over time with SLAC’s ultrafast “electron camera” – an apparatus for ultrafast electron diffraction (UED) that uses a highly energetic electron beam to probe a sample’s atomic structure and nuclear motions.

    “UED is a powerful tool for studies of these very thin 2-D materials,” says SLAC staff scientist Xiaozhe Shen, a co-author of the paper. “The technique yields relatively strong signals, high spatial resolution, and it nicely complements X-ray laser studies in making movies of a material’s atomic structure.”

    Although the researchers didn’t see a phase transition in molybdenum diselenide, their results help them better understand the energy transfer from the laser light to the material.

    “It’s an important first step toward designing 2-D materials that we can control with light,” Lin says. “The next steps will be to find out if we can see light-induced phase transitions in other materials and if we can make materials whose properties we can alter in a controlled way by steering phase transitions in particular directions.”

    The results are also used for the validation of novel software developed by the Materials Genome Innovation for Computational Software (MAGICS) center, led by the University of Southern California, Los Angeles. Another MAGICS partner involved in the study was Rice University, where the 2-D material was synthesized.

    “Similar to biological genome projects that want to find out everything about the genomes of organisms, our goal is to learn everything about materials and to develop computational tools that allow us to make accurate predictions of material properties,” says SLAC’s Uwe Bergmann, the center’s associate director for validation and the principal investigator of the study. “MAGICS brings together researchers who develop advanced computer code, who take on the challenging synthesis of 2-D materials, and who provide the experimental data needed for testing the computer models. At SLAC, we’re doing UED experiments and ultrafast X-ray studies, but without the center’s team effort, this work wouldn’t be possible.”

    Experiments for this study were carried out by researchers from SLAC’s Linac Coherent Light Source (LCLS),


    a DOE Office of Science User Facility; the Stanford PULSE Institute, which is jointly operated by SLAC and Stanford University; and the lab’s Accelerator Directorate. Samples came from Rice University, and computer simulations were done at USC. Additional MAGICS partners not involved in this study are DOE’s Lawrence Berkeley National Laboratory, the University of Missouri and the California Institute of Technology. The study was funded by the DOE Office of Science and the National Science Foundation.

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  • richardmitnick 10:04 am on November 22, 2017 Permalink | Reply
    Tags: , , Scientists Make First Observations of How a Meteor-Like Shock Turns Silica Into Glass, SLAC LCLS   

    From SLAC: “Scientists Make First Observations of How a Meteor-Like Shock Turns Silica Into Glass” 

    SLAC Lab

    November 16, 2017
    Julia Goldstein

    Research with SLAC’s X-ray laser simulates what happens when a meteor hits Earth’s crust. The results suggest that scientists studying impact sites have been overestimating the sizes of the meteors that made them.

    Meteor Crater in Arizona, formed by a meteor impact 50,000 years ago, contains bitsof a hard, compressed form of silica called stishovite. (Nikolas_jkd/iStock).

    Studies at the Department of Energy’s SLAC National Accelerator Laboratory have made the first real-time observations of how silica – an abundant material in the Earth’s crust – easily transforms into a dense glass when hit with a massive shock wave like one generated from a meteor impact.

    The results imply that meteors hitting Earth and other celestial objects are smaller than originally thought. This new information will be important for modeling planetary body formation and interpreting evidence of impacts on the ground.

    The experiments took place at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, a DOE Office of Science User Facility whose ultrafast pulses can reveal processes taking place in millionths of a billionth of a second with atomic resolution.


    “We were able for the first time to really visualize from start to finish what happens in a material that makes up a major portion of the Earth’s crust,” said Arianna Gleason of the DOE’s Los Alamos National Laboratory (LANL), the principal investigator for the study, which was published Nov. 14 in Nature Communications.

    How Does Shocked Glass Get That Way?

    Scientists have long known that impacts from meteors convert silicates into a dense, amorphous phase known as shocked glass. The question is how this shocked glass forms.

    In the past, scientists have tried to estimate the amount of pressure needed to cause this transformation by examining debris from meteor impacts and squeezing mineral samples in pressure cells in the lab, but they were unable to observe the process as it unfolded.

    At LCLS, researchers can use an intense laser beam to create a shock wave that compresses a silica sample, and then use the X-ray laser to examine its response on a timescale of nanoseconds, or billionths of a second.

    A previous SLAC study, published in 2015, demonstrated that silica forms stishovite, a crystalline phase, within 10 nanoseconds of being hit by the initial laser pulse. That research showed that the transformation occurred much more rapidly than was previously believed. But the existence of debris from meteor impacts that is composed entirely of shocked glass suggests that stishovite may be a short-lived phase that can convert permanently to shocked glass after impact.

    Overturning Assumptions

    In the latest study, the scientists took advantage of the Matter in Extreme Conditions instrument at LCLS to generate shock waves that induced various peak pressures in silica samples. After sending the laser pulse, “We just watch what the silica does naturally,” said Gleason, who is the LANL Fredrick Reines Postdoctoral Fellow.

    Analysis of X-ray diffraction data taken at various intervals after peak pressure was reached showed that when the pressure is high enough, stishovite forms, but it then reverts to shocked glass. The diffraction data from the LCLS samples matched data from impact debris collected in the field.

    This drawing depicts the process that turns silica into shocked glass after it’s hit with a shock wave like one from a meteor impact. At right, compression has transformed the silica into stishovite crystals. On the left, the compression has been released and the stishovite crystals have transformed into shocked glass. The LCLS X-ray laser beam recorded this process, which happens within 30 nanoseconds. (A.E. Gleason et al., Nature Communications)

    Scientists have previously assumed that peak pressures of roughly 40 gigapascals – equivalent to 400,000 times the atmospheric pressure around us – are required to create shocked glass from silica. But the results from this study suggest that the threshold is about 25 percent lower than that, and that stishovite then reverts to the shocked glass state due to thermal instability rather than higher pressure.

    “An impact event has a short timeline,” said Gleason, “making LCLS an ideal instrument for understanding the fundamental thermodynamics of glasses formed by impacts.” Gleason envisions using the MEC at LCLS to investigate other Earth-abundant minerals, such as feldspar, and to better understand the “rule book” for transformation processes.

    Gleason’s research is more broadly applicable to debris from other planets, such as meteorites from Mars that also contain shocked glass. Martian meteorites often contain trapped volatile compounds, such as water vapor and methane. No one understands how these compounds become locked inside meteorites or why they don’t escape, but continued work at LCLS could provide answers.

    In addition to LANL and SLAC, researchers contributing to this study came from the Stanford Institute for Materials and Energy Sciences (SIMES), the DOE’s Lawrence Livermore National Laboratory, the Center for High Pressure Science and Technology Advanced Research in Shanghai, the Carnegie Institution of Washington’s High Pressure Synergetic Consortium, Friedrich Schiller University Jena in Germany and Stanford University. Major funding came from the DOE Office of Science and the National Science Foundation. Part of the work was carried out at the Advanced Light Source, a DOE Office of Science User Facility at DOE’s Lawrence Berkeley National Laboratory.

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  • richardmitnick 5:10 pm on November 13, 2017 Permalink | Reply
    Tags: Elusive Atomic Deformations, , , Matter in Extreme Condition (MEC) experimental station at SLAC’s LCLS, SLAC LCLS, SLAC X-ray Laser Reveals How Extreme Shocks Deform a Metal’s Atomic Structure, The Tremendous Shock of a Tiny Recoil, , , When hit by a powerful shock wave materials can change their shape – a property known as plasticity – yet keep their lattice-like atomic structure   

    From SLAC: “SLAC X-ray Laser Reveals How Extreme Shocks Deform a Metal’s Atomic Structure” 

    SLAC Lab

    November 13, 2017
    Glennda Chui

    This image depicts an experimental setup at SLAC’s Linac Coherent Light Source, where a tantalum sample is shocked by a laser and probed by an X-ray beam. The resulting diffraction patterns, collected by an array of detectors, show the material undergoes a particular type of plastic deformation called twinning. The background illustration shows a lattice structure that has created twins. (Ryan Chen/LLNL)


    When hit by a powerful shock wave, materials can change their shape – a property known as plasticity – yet keep their lattice-like atomic structure. Now scientists have used the X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to see, for the first time, how a material’s atomic structure deforms when shocked by pressures nearly as extreme as the ones at the center of the Earth.

    The researchers said this new way of watching plastic deformation as it happens can help study a wide range of phenomena, such as meteor impacts, the effects of bullets and other penetrating projectiles and high-performance ceramics used in armor, as well as how to protect spacecraft from high-speed dust impacts and even how dust clouds form between the stars.

    The experiments took place at the Matter in Extreme Condition (MEC) experimental station at SLAC’s Linac Coherent Light Source (LCLS). They were led by Chris Wehrenberg, a physicist at the DOE’s Lawrence Livermore National Laboratory, and described in a recent paper in Nature.

    “People have been creating these really high-pressure states for decades, but what they didn’t know until MEC came online is exactly how these high pressures change materials – what drives the change and how the material deforms,” said SLAC staff scientist Bob Nagler, a co-author of the report.

    “LCLS is so powerful, with so many X-rays in such a short time, that it can interrogate how the material is changing while it is changing. The material changes in just one-tenth of a billionth of a second, and LCLS can deliver enough X-rays to capture information about those changes in a much shorter time that that.”

    Elusive Atomic Deformations

    The material they studied here was a thin foil made of tantalum, a blue-gray metallic element whose atoms are arranged in cubes. The team used a polycrystalline form of tantalum that is naturally textured so the orientation of these cubes varies little from place to place, making it easier to see certain types of disruptions from the shock.

    When this type of crystalline material is squeezed by a powerful shock, it can deform in two distinct ways: twinning, where small regions develop lattice structures that are the mirror images of the ones in surrounding areas, and slip deformation, where a section of the lattice shifts and the displacement spreads, like a propagating crack.

    But while these two mechanisms are fundamentally important in plasticity, it’s hard to observe them as a shock is happening. Previous research had studied shocked materials after the fact, as the material recovered, which introduced complications and led to conflicting interpretations.

    The Tremendous Shock of a Tiny Recoil

    In this experiment, the scientists shocked a piece of tantalum foil with a pulse from an optical laser. This vaporizes a small piece of the foil into a hot plasma that flies away from the surface. The recoil from this tiny plume creates tremendous pressures in the remaining foil – up to 300 gigapascals, which is three million times the atmospheric pressure around us and comparable to the 350-gigapascal pressure at the center of the Earth, Nagler said.

    While this was happening, researchers probed the state of the metal with X-ray laser pulses. The pulses are extremely short – only 50 femtoseconds, or millionths of a billionth of a second, long – and like a camera with a very fast shutter speed they can record the metal’s response in great detail.

    The X-rays bounce off the metal’s atoms and into a detector, where they create a “diffraction pattern” – a series of bright, concentric rings – that scientists analyze to determine the atomic structure of the sample. X-ray diffraction has been used for decades to discover the structures of materials, biomolecules and other samples and to observe how those structures change, but it’s only recently been used to study plasticity in shock-compressed materials, Wehrenberg said.

    And this time the researchers took the technique one step further: They analyzed not just the diffraction patterns, but also how the scattering signals were distributed inside individual diffraction rings and how their distribution changed over time. This deeper level of analysis revealed changes in the tantalum’s lattice orientation, or texture, taking place in about one-tenth of a billionth of a second. It also showed whether the lattice was undergoing twinning or slip over a wide range of shock pressures – right up to the point where the metal melts. The team discovered that as the pressure increased, the dominant type of deformation changed from twinning to slip deformation.

    Wehrenberg said the results of this study are directly applicable to Lawrence Livermore’s efforts to model both plasticity and tantalum at the molecular level.

    These experiments, he said, “are providing data that the models can be directly compared to for benchmarking or validation. In the future, we plan to coordinate these experimental efforts with related experiments on LLNL’s National Ignition Facility that study plasticity at even higher pressures.”

    In addition to LLNL and SLAC, researchers from the University of Oxford, the DOE’s Los Alamos National Laboratory and the University of York contributed to this study. Funding for the work at SLAC came from the DOE Office of Science. LCLS is a DOE Office of Science User Facility.

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  • richardmitnick 10:24 pm on September 20, 2017 Permalink | Reply
    Tags: , , , SLAC LCLS,   

    From SLAC: “High-Speed Movie Aids Scientists Who Design Glowing Molecules” 

    SLAC Lab

    September 20, 2017
    Amanda Solliday

    Aequorea victoria, also called the crystal jelly, is a bioluminescent jellyfish that lives near the Pacific coast of North America. (Gary Kavanagh/iStockphoto.com)

    The Coherent X-Ray Imaging (CXI) instrument makes use of the brilliant hard X-ray pulses from the Linac Coherent Light Source. The equipment is tailored for X-ray crystallography experiments. (SLAC National Accelerator Laboratory)


    With SLAC’s X-ray laser, a research team captured ultrafast changes in fluorescent proteins between “dark” and “light” states. The insights allowed the scientists to design improved markers for biological imaging.

    The crystal jellyfish swims off the coast of the Pacific Northwest and can illuminate the waters when disturbed. That glow comes from proteins that absorb energy and then release it as bright flashes.

    To track many of life’s activities, biologists took a cue from this same jellyfish.

    Scientists collected one of the proteins found in the sea creatures, green fluorescent protein (GFP), and engineered a molecular light switch that would glow or remain dark depending on specific experimental conditions. The glowing labels are attached to molecules in living cells so researchers can highlight them during imaging experiments. They use these fluorescent markers to understand how a cell responds to changes in its environment, identify which molecules interact within a cell and track the effects of genetic mutations.

    Researchers have studied GFP and other fluorescent proteins for decades to better understand their glowing action and improve their function in scientific studies, but they have never been able to observe the ultrafast changes that occur between “off” and “on” states until now.

    In a recent experiment conducted at the Department of Energy’s SLAC National Accelerator Laboratory, a research team used bright, ultrafast X-ray pulses from SLAC’s X-ray free-electron laser to create a high-speed movie of a fluorescent protein in action. With that information, the scientists began to design a marker that switches more easily, a quality that can improve resolution during biological imaging.

    “We think that this approach will open a world of possibilities to tailor fluorescent proteins,” says Martin Weik, scientist at the Institute of Structural Biology in Grenoble, France and one of the authors on the publication. “We not only have the structure of the fluorescent protein, but now we can see what is happening between one static state and the other.”

    Nature Chemistry published the study on Sept. 11.

    Filming a Molecular Light Switch

    To observe these intermediate states, the scientists initiated a photochemical reaction in the fluorescent protein with an optical laser at the Coherent X-ray Imaging instrument at the Linac Coherent Light Source, followed by X-ray snapshots at distinct time delays. The optical laser provides energy in the form of photons, mimicking what happens in nature.

    “Atoms move around in the photoactive site of the molecule as a result of absorption of a photon,” says Sebastien Boutet, SLAC scientist and a co-author of the paper. “This structural change turns the protein from a dark state to a light-emitting (fluorescent) state.”

    There’s a vast body of literature calculating what might happen between the two states, but no one studying the protein was able to see the structural changes in the switch as the photon is absorbed. The molecular switch was just too fast for traditional X-ray imaging techniques.

    In this study, the femtosecond X-ray pulses generated by LCLS—arriving in just millionths of a billionth of a second—allowed the team to create stop-action images of the process at an extremely close interval after the proteins were activated by the optical laser.

    A Door Half Open

    The high-speed snapshots were used to generate a movie starting from the dark state, and gave the researchers insights that they used to design more efficient switchable light-emitting proteins. They found a clue in the time the molecules spent between fluorescent and non-fluorescent states.

    “After a picosecond, and for a very short time, this molecular switch is stuck between on and off,” says Ilme Schlichting, scientist at the Max-Planck Institute in Heidelberg, Germany and one of the authors on the publication. “People have predicted this, but to actually visualize its structure is extremely exciting.”

    “It’s as if there’s a door and it’s neither closed nor completely open; it’s half open,” she says. “And now we are learning what can go through the door, what might be blocking it and how it works in real time.”

    In this study, the scientists found that an amino acid blocked the door and prevented the switch from flipping as easily as possible.

    The researchers shortened the amino acid in a mutated version of the fluorescent protein. This engineered version switched more easily and gave better contrast. These traits will allow scientists to observe cellular activity with greater precision.

    “Contrast is essential in imaging. It’s like on a TV screen, where to see the best picture, you want the dark to be extremely dark and the color to be super bright and colorful,” says Jacques-Philippe Colletier, a scientist at the Institute of Structural Biology who contributed to the research.

    This new molecular movie featuring the jellyfish-inspired proteins lights the way to capture more of life’s microscopic details. The team will continue to fine-tune the protein for other desired characteristics that make it ideal for “super-resolution microscopy,” a type of light microscopy where scientists are able to see illuminated details of cells not distinguishable with conventional light microscopy methods.

    The research collaboration included several French institutions, including the Institute of Structural Biology, University of Lille, University of Paris-Sud and the University of Rennes, as well as Max Planck Institutes in Germany and SLAC.

    LCLS is a DOE Office of Science User Facility.

    See the full article here .

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  • richardmitnick 7:35 am on September 1, 2017 Permalink | Reply
    Tags: , , , , MEC- Matter in Extreme Conditions, , SLAC LCLS, ,   

    From SLAC: “Newly Upgraded Laser Allows Scientists to Peer Further Into the Extreme Universe at SLAC’s LCLS” 

    SLAC Lab

    August 15, 2017
    Miyuki Dougherty

    Highly reflective mirrors and telescope lenses in the Matter in Extreme Conditions (MEC) optical laser system are carefully positioned to propagate the instrument’s high-quality laser beams. The laser beams create extreme pressure and temperature conditions in materials that are instantaneously probed using hard X-rays from SLAC’s Linac Coherent Light Source (LCLS). (Dawn Harmer/SLAC National Accelerator Laboratory)

    Tripling the energy and refining the shape of optical laser pulses at the Matter in Extreme Conditions instrument allows researchers to create higher-pressure conditions and explore unsolved fusion energy, plasma physics and materials science questions.

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory recently upgraded a powerful optical laser system used to create shockwaves that generate high-pressure conditions like those found within planetary interiors. The laser system now delivers three times more energy for experiments with SLAC’s ultrabright X-ray laser, providing a more powerful tool for probing extreme states of matter in our universe.

    Together, the optical and X-ray lasers form the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS).


    The high-power optical laser system creates extreme temperature and pressure conditions in materials, and the X-ray laser beam captures the material’s response.

    With this technology, researchers have already examined how meteor impacts shock minerals in the Earth’s crust and simulated conditions in Jupiter’s interior by turning aluminum foil into a warm, dense plasma.

    Higher Intensity and More Controlled Pulse Shapes

    The MEC instrument team received funding from the Office of Fusion Energy Sciences (FES) within the DOE’s Office of Science to double the amount of energy the optical beam can deliver in 10 nanoseconds, from 20 to 40 joules.

    But they went even further.

    “The team exceeded our expectations, an exciting accomplishment for the DOE High Energy Density program and future MEC instrument users,” says Kramer Akli, program manager for High Energy Density Laboratory Plasma at FES.

    The team tripled the amount of energy the laser can deliver in 10 nanoseconds to a spot on a target no bigger than the width of a few human hairs. When focused down to that small area, the laser provides users with intensities up to 75 terawatts per square centimeter.

    “In other terms, the upgraded laser has the same power as 17 Teslas discharging their 100 kilowatt-hour batteries in one second,” says Eric Galtier, a MEC instrument scientist.

    A portion of the energy upgrade can be attributed to the optical laser’s new, homemade diode pumped front-end, designed with the help of Marc Welch, a MEC laser engineer. The scientists also built and automated a system for shaping the laser pulses with extraordinary precision, allowing users substantially greater flexibility and control over the pulse shapes used in their experiments.

    A more powerful and reliable laser means that researchers can study higher pressure regimes and reach conditions relevant to fusion energy studies.

    Simulating the Core of Planets

    The MEC upgrade is promising for many researchers, including Shaughnessy Brennan Brown, a doctoral student in Mechanical Engineering, whose research focuses on high energy density science, which spans chemistry, materials science, and physics. Brennan Brown uses the MEC experimental hutch to drive shock waves through silicon and generate high-pressure conditions that occur in the Earth’s interior.

    “The MEC upgrade at LCLS enables researchers like me to generate exciting, previously-unexplored regimes of exotic matter – such as those found on Mars, our next planetary stepping stone – with crucial reliability and repeatability,” Brennan Brown says.

    Brennan Brown’s research examines the processes by which silicon in Earth’s core rearranges atomically under high temperature and pressure conditions. The thermodynamic properties of these high-pressure states affect our magnetic field, which protects us from the solar wind and allows us to survive on Earth. The laser upgrade will permit Brennan Brown to reach higher pressure and temperature conditions inside her samples, a long-standing goal.

    Inside the MEC vacuum target chamber where researchers create transient states of matter using high-power optical lasers, which are then examined with SLAC’s Linac Coherent Light Source (LCLS) X-rays. (Matt Beardsley/SLAC National Accelerator Laboratory)

    Intensity Plus Precision

    The optical laser amplifies a low-power beam in stages and reaches increasingly high energies. However, the quality of the laser beam and ability to control it diminish during amplification. A low-quality pulse may start and end with a significantly different shape, which is not useful for researchers trying to recreate specific conditions.

    “The initial low energy pulse must have a pristine spatial mode and the properly configured temporal shape – that is, a precise sculpting of the pulse’s power as a function of time – before amplification to produce the laser pulse characteristics needed to enable each users’ experiment,” says Michael Greenberg, the MEC Laser Area Manager.

    Each target is unique and requires a specific energy and pulse shape, making manual tests and adjustments time-consuming. Prior to the upgrade, the team optimized the pulse shape by hand, taking anywhere from a few hours to a few days to properly calibrate it.

    To resolve this issue, Eric Cunningham, a laser scientist at MEC, developed an automated control system to shape the low-powered beam before amplification.

    To demonstrate the MEC laser system’s enhanced ability to tailor the shape of laser pulses, scientists generated pulse shapes that spell out “M-E-C” in a plot of laser intensity vs. time. (Eric Cunningham and Michael Greenberg/SLAC National Accelerator Laboratory)

    “The new system allows for precise tailoring of the pulse shape using a computerized feedback loop system that analyzes the pulses and automatically re-calibrates the laser,” Cunningham said. The new optimizer is a promising system for generating many high-quality pulses in the most accurate and timely manner possible.

    In addition to the improved pulse shapes, the upgraded system deposits energy on samples more consistently from shot to shot, which allows researchers to very closely reproduce extreme states of matter in their samples. As a result, both the data quality and operational efficiency are improved.

    Brennan Brown says it’s the people and technology that make the instrument so successful: “The capability and competency of the laser scientists and engineers at the MEC experimental station offer researchers the technological resources they need to explore unanswered questions of the universe and bring their theories to life.”

    LCLS is a DOE Office of Science User Facility.

    See the full article here .

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  • richardmitnick 10:56 am on August 21, 2017 Permalink | Reply
    Tags: , Diamond rain, MEC-Matter in Extreme Conditions instrument, , SLAC LCLS,   

    From SLAC: “Scientists Create ‘Diamond Rain’ That Forms in the Interior of Icy Giant Planets” 

    SLAC Lab

    August 21, 2017
    Amanda Solliday
    (650) 926-4496

    A cutaway depicts the interior of Neptune (left). In an experiment conducted at the Linac Coherent Light Source, the team studied a plastic simulating compounds formed from methane—a molecule with just one carbon bound to four hydrogen atoms that causes the distinct blue cast of Neptune. Methane forms hydrocarbon (hydrogen and carbon) chains that respond to high pressure and temperature to form “diamond rain” in the interiors of icy giant planets like Neptune. The scientists were able to recreate similar conditions using high-powered optical lasers and watch the small diamonds form in real time with X-rays. (Greg Stewart/SLAC National Accelerator Laboratory)

    In an experiment designed to mimic the conditions deep inside the icy giant planets of our solar system, scientists were able to observe “diamond rain” for the first time as it formed in high-pressure conditions. Extremely high pressure squeezes hydrogen and carbon found in the interior of these planets to form solid diamonds that sink slowly down further into the interior.

    The glittering precipitation has long been hypothesized to arise more than 5,000 miles below the surface of Uranus and Neptune, created from commonly found mixtures of just hydrogen and carbon. The interiors of these planets are similar—both contain solid cores surrounded by a dense slush of different ices. With the icy planets in our solar system, “ice” refers to hydrogen molecules connected to lighter elements, such as carbon, oxygen and/or nitrogen.

    Researchers simulated the environment found inside these planets by creating shock waves in plastic with an intense optical laser at the Matter in Extreme Conditions (MEC) instrument at SLAC National Accelerator Laboratory’s X-ray free-electron laser, the Linac Coherent Light Source (LCLS).


    SLAC is one of 10 Department of Energy (DOE) Office of Science laboratories.

    In the experiment, the scientists were able to see that nearly every carbon atom of the original plastic was incorporated into small diamond structures up to a few nanometers wide. On Uranus and Neptune, the study authors predict that diamonds would become much larger, maybe millions of carats in weight. Researchers also think it’s possible that over thousands of years, the diamonds slowly sink through the planets’ ice layers and assemble into a thick layer around the core.

    The research published in Nature Astronomy on August 21.

    “Previously, researchers could only assume that the diamonds had formed,” said Dominik Kraus, scientist at Helmholtz Zentrum Dresden-Rossendorf and lead author on the publication. “When I saw the results of this latest experiment, it was one of the best moments of my scientific career.”

    Earlier experiments that attempted to recreate diamond rain in similar conditions were not able to capture measurements in real time, because we currently can create these extreme conditions under which tiny diamonds form only for very brief time in the laboratory. The high-energy optical lasers at MEC combined with LCLS’s X-ray pulses—which last just femtoseconds, or quadrillionths of a second—allowed the scientists to directly measure the chemical reaction.

    Other prior experiments also saw hints of carbon forming graphite or diamond at lower pressures than the ones created in this experiment, but with other materials introduced and altering the reactions.

    The results presented in this experiment is the first unambiguous observation of high-pressure diamond formation from mixtures and agrees with theoretical predictions about the conditions under which such precipitation can form and will provide scientists with better information to describe and classify other worlds.

    Turning Plastic Into Diamond

    In the experiment, plastic simulates compounds formed from methane—a molecule with just one carbon bound to four hydrogen atoms that causes the distinct blue cast of Neptune.

    The team studied a plastic material, polystyrene, that is made from a mixture of hydrogen and carbon, key components of these planets’ overall chemical makeup.

    In the intermediate layers of icy giant planets, methane forms hydrocarbon (hydrogen and carbon) chains that were long hypothesized to respond to high pressure and temperature in deeper layers and form diamond rain.

    The researchers used high-powered optical laser to create pairs of shock waves in the plastic with the correct combination of temperature and pressure. The first shock is smaller and slower and overtaken by the stronger second shock. When the shock waves overlap, that’s the moment the pressure peaks and when most of the diamonds form, Kraus said.

    During those moments, the team probed the reaction with pulses of X-rays from LCLS that last just 50 femtoseconds. This allowed them to see the small diamonds that form in fractions of a second with a technique called femtosecond X-ray diffraction. The X-ray snapshots provide information about the size of the diamonds and the details of the chemical reaction as it occurs.

    “For this experiment, we had LCLS, the brightest X-ray source in the world,” said Siegfried Glenzer, professor of photon science at SLAC and a co-author of the paper. “You need these intense, fast pulses of X-rays to unambiguously see the structure of these diamonds, because they are only formed in the laboratory for such a very short time.”

    The Matter in Extreme Conditions instrument at SLAC gives scientists the tools to investigate the extremely hot, dense matter at the centers of stars and giant planets. These experiments could help researchers design new materials with enhanced properties and recreate the nuclear fusion process that powers the sun. (SLAC National Accelerator Laboratory)

    Nanodiamonds at Work

    When astronomers observe exoplanets outside our solar system, they are able to measure two primary traits—the mass, which is measured by the wobble of stars, and radius, observed from the shadow when the planet passes in front of a star. The relationship between the two is used to classify a planet and help determine whether it may be composed of heavier or lighter elements.

    “With planets, the relationship between mass and radius can tell scientists quite a bit about the chemistry,” Kraus said. “And the chemistry that happens in the interior can provide additional information about some of the defining features of the planet.”

    Information from studies like this one about how elements mix and clump together under pressure in the interior of a given planet can change the way scientists calculate the relationship between mass and radius, allowing scientists to better model and classify individual planets. The falling diamond rain also could be an additional source of energy, generating heat while sinking towards the core.

    “We can’t go inside the planets and look at them, so these laboratory experiments complement satellite and telescope observations,” Kraus said.

    The researchers also plan to apply the same methods to look at other processes that occur in the interiors of planets.

    In addition to the insights they give into planetary science, nanodiamonds made on Earth could potentially be harvested for commercial purposes—uses that span medicine, scientific equipment and electronics. Currently, nanodiamonds are commercially produced from explosives; laser production may offer a cleaner and more easily controlled method.

    Research that compresses matter, like this study, also helps scientists understand and improve fusion experiments where forms of hydrogen combine to form helium to generate vast amounts of energy. This is the process that fuels the sun and other stars but has yet to be realized in a controlled way for power plants on Earth.

    In some fusion experiments, a fuel of two different forms of hydrogen is surrounded by a plastic layer that reaches conditions similar to the interior of planets during a short-lived compression stage. The LCLS experiment on plastic now suggests that chemistry may play an important role in this stage.

    “Simulations don’t really capture what we’re observing in this field,” Glenzer said. “Our study and others provide evidence that matter clumping in these types of high-pressure conditions is a force to be reckoned with.”

    The research collaboration includes scientists from Helmholtz Zentrum Dresden-Rossendorf in Germany, University of California-Berkeley, Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, GSI Helmholtz Center for Heavy Ion Research in Germany, Osaka University in Japan, Technical University of Darmstadt in Germany, European XFEL, University of Michigan, University of Warwick in the United Kingdom and SLAC.

    The research was supported by DOE’s Office of Science and the National Nuclear Security Administration. LCLS is a DOE Office of Science User Facility.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

  • richardmitnick 12:58 pm on July 19, 2017 Permalink | Reply
    Tags: , , New Droplet-on-Tape Method Assists Biochemical Research at X-Ray Lasers, , SLAC LCLS,   

    From SLAC: “New Droplet-on-Tape Method Assists Biochemical Research at X-Ray Lasers” 

    SLAC Lab

    February 27, 2017 [Never saw this one before]

    Acoustic droplet ejection allows scientists to deposit nanoliters of sample directly into the X-ray beam, considerably increasing the efficiency of sample consumption. A femtosecond pulse from an X-ray free-electron laser then intersects with a droplet that contains protein crystals. (SLAC National Accelerator Laboratory)


    As the drops move forward, they are hit with pulses of visible light or treated with oxygen gas, which triggers different chemical reactions depending on the sample studied. (SLAC National Accelerator Laboratory)

    Biological samples studied with intense X-rays at free-electron lasers are destroyed within nanoseconds after they are exposed. Because of this, the samples need to be continually refreshed to allow the many images needed for an experiment to be obtained. Conventional methods use jets that supply a continuous stream of samples, but this can be very wasteful as the X-rays only interact with a tiny fraction of the injected material.

    To help address this issue, scientists at the Department of Energy’s Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and other institutes designed a new assembly-line system that rapidly replaces exposed samples by moving droplets along a miniature conveyor belt, timed to coincide with the arrival of the X-ray pulses.

    The droplet-on-tape system now allows the team to study the biochemical reactions in real-time from microseconds to seconds, revealing the stages of these complex reactions.

    In their approach, protein solution or crystals are precisely deposited in tiny liquid drops, made as ultrasound waves push the liquid onto a moving tape. As the drops move forward, they are hit with pulses of visible light or treated with oxygen gas, which triggers different chemical reactions depending on the sample studied. This allows the study of processes such as photosynthesis, which determines how plants absorb light from the sun and convert it into useable energy.

    Finally, powerful X-ray pulses from SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS), probe the drops. In this study published in Nature Methods, the X-ray light scattered from the sample onto two different detectors simultaneously, one for X-ray crystallography and the other for X-ray emission spectroscopy. These are two complementary methods that provide information about the geometric and electronic structure of the catalytic sites of the proteins and allowed them to watch with atomic precision how the protein structures changed during the reaction.

    Below, see the conveyor belt in action at LCLS, a Department of Energy Office of Science User Facility.

    Droplet-on-tape conveyor belt system delivers samples at the Linac Coherent Light Source (LCLS). (SLAC National Accelerator Laboratory)

    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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