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

    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 .

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    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 5:34 pm on July 5, 2017 Permalink | Reply
    Tags: , , Getting ready for LCLS-II, SLAC,   

    From SLAC: “SLAC’s Electron Hub Gets New ‘Metro Map’ for World’s Most Powerful X-Ray Laser” 

    SLAC Lab

    July 5, 2017
    Manuel Gnida

    A reconfiguration of SLAC’s historic Beam Switch Yard will include electron transport lines needed for LCLS-II, a major upgrade to the Linac Coherent Light Source (LCLS) X-ray laser. (Greg Stewart/SLAC National Accelerator Laboratory)

    The central hub for powerful electron beams at the Department of Energy’s SLAC National Accelerator Laboratory is getting a makeover to prepare for the installation of LCLS-II – a major upgrade to the Linac Coherent Light Source (LCLS), the world’s first hard X-ray free-electron laser. LCLS-II will deliver the most powerful X-rays ever made in a lab, with beams that are 10,000 times brighter than before, opening up unprecedented research opportunities in chemistry, materials science, biology and energy research.

    Central portion of the BSY before (left) and after the Reconfiguration Project. (Scott DeBarger/SLAC National Accelerator Laboratory)

    A Monumental Clean-up Operation

    To clear the path for LCLS-II, crews first had to remove all unnecessary materials from the BSY – a monumental task considering SLAC’s rich history in accelerator science and the legacy material it created.

    “When experiments end, most of the old equipment is typically left in place,” says SLAC’s Mark Woodley, an optics designer involved in the BSY Reconfiguration Project. “Only the things that are in the way of new experiments are taken out.”

    In its early days in the 1960s, the linac delivered electron beams to three experimental stations. There was one line going straight into the lab’s research yard. Today this line continues to the LCLS undulator. Pulsed magnets in the BSY could divert the beam into End Stations A and B via two beamlines that branched off the central line.

    In 1980, two more branches were added to feed electrons and positrons, the antiparticle siblings of electrons, into the two storage rings of the PEP accelerator (PEP-II from 1999). In 1987, another two branches were needed to deliver beams to the two arms of the Stanford Linear Collider (SLC).

    Most of the old materials left behind in the BSY by these experiments have now been cleared – a job that took 300 employees and subcontractors almost 24,000 hours of work in the period from December 2016 to May 2017. They removed 325 cubic yards, or about 24 tons, of material – enough to fill eight sea-land shipping containers – and more than 300,000 feet of cables.

    “Considering the monumental task we had ahead of us, it’s truly impressive how well this project went,” DeBarger says. “It involved many people from inside and outside the lab, and every single one of them was absolutely needed.”

    Building the Future of X-ray Science

    After clearing out the BSY, members of the Reconfiguration Project installed a new beamline that runs from the copper linac to the current LCLS undulator. In parallel, the system to extract electrons for the End Station A line was put in place by another project team.

    “We also installed the very first LCLS-II beam pipe at the end of a ‘muon shield’ that is constructed of 5- and 10-ton steel blocks and shields the beam transport hall downstream of the BSY, allowing access while beams are tuned in the BSY,” says Dean Hanquist, control account manager on Chan’s team.

    “In the end, we had to make sure that everything works properly again for LCLS, which has now resumed its experimental program,” says BSY Area Physicist Tonee Smith. “For example, all of the magnets used in the beamline to focus the electron beam and make small corrections to it were refurbished, and we had to remeasure and test them.”

    The remaining beamlines and junctions will be installed during a yearlong LCLS downtime, which will start in the summer of 2018. Once completed, the new BSY “metro system” will be ready to transport electron trains to the new X-ray laser facility, where they will power groundbreaking X-ray science for years to come.

    Crew members gather at the conclusion of the BSY Reconfiguration Project. (Dawn Harmer/SLAC National Accelerator Laboratory)

    For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.

    The interior of the east portion of the Beam Switch Yard (BSY) showing three “tracks” that electrons accelerated in SLAC’s linear accelerator can be directed into. All of the beams for LCLS and LCLS-II are sent through the central tunnel. In early 2017, as part of the LCLS-II project, the steel Muon Shield was reconfigured to permit installation of a new beamline that will transport beams to a new Soft X-Ray Undulator. (Chris Smith/SLAC National Accelerator Laboratory)

    Workers install the shield pipe that will position and protect the LCLS-II vacuum chamber within the Muon Shield. (Chris Smith/SLAC National Accelerator Laboratory)

    Surveyors Bryan Rutledge and Francis Gaudreault measure the position of the LCLS beamline prior to its disassembly. (Chris Smith/SLAC National Accelerator Laboratory)

    Mechanical Engineer Alev Ibrahimov, left, and Transport Systems CAM Dean Hanquist inspect the LCLS-II installation location in Sector 30. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Rigger Scot Johnson positions a movable hoist. (Chris Smith/SLAC National Accelerator Laboratory)

    A crane removes the D-10 Tune-up Dump. This dump has five apertures, visible at the end of the device, which over the years allowed beams to head to various downstream experimental areas including LCLS, End Station A, End Station B and SPEAR. (Chris Smith/SLAC National Accelerator Laboratory)

    See the full article here .

    Please help promote STEM in your local schools.

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    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 12:35 pm on June 17, 2017 Permalink | Reply
    Tags: Axion theory, , , , , Helen Quinn and Roberto Peccei, Peccei-Quinn symmetry, , SLAC,   

    From Quanta: “Roberto Peccei and Helen Quinn, Driving Around Stanford in a Clunky Jeep” 

    Quanta Magazine
    Quanta Magazine

    June 15, 2017
    Thomas Lin
    Olena Shmahalo, Art Director
    Lucy Reading-Ikkanda, graphics

    Ryan Schude for Quanta Magazine
    Helen Quinn and Roberto Peccei walking toward Stanford University’s new science and engineering quad. Behind them is the main quad, the oldest part of the campus. “If you look at a campus map,” said Quinn, who along with Peccei proposed Peccei-Quinn symmetry, “you will see the axis that goes through the middle of both quadrangle areas. We are on that line between the two.”

    Four decades ago, Helen Quinn and Roberto Peccei took on one of the great problems in theoretical particle physics: the strong charge-parity (CP) problem. Why does the symmetry between matter and antimatter break in weak interactions, which are responsible for nuclear decay, but not in strong interactions, which hold matter together?

    “The academic year 1976-77 was particularly exciting for me because Helen Quinn and Steven Weinberg were visiting the Stanford department of physics,” Peccei told Quanta in an email. “Helen and I had similar interests and we soon started working together.”

    Encouraged by Weinberg, who would go on to win a Nobel Prize in physics in 1979 for his work on the unification of electroweak interactions, Quinn and Peccei zeroed in on a CP-violating interaction whose strength can be characterized by an angular variable, theta. They knew theta had to be small, but no one had an elegant mechanism for explaining its smallness.

    “Steve liked to discuss physics over lunch, and Helen and I often joined him,” Peccei said. “Steve invariably brought up the theta problem in our lunch discussions, urging us to find a natural solution for why it was so small.”

    Quinn said by email that she and Peccei knew two things: The problem goes away if any quarks have zero mass (which seems to make theta irrelevant), and “in the very early hot universe all the quarks have zero mass.” They wondered how it could be that “theta is irrelevant in the early universe but matters once it cools enough that the quarks get their masses?”

    They proceeded to draft a “completely wrong paper based on conclusions we drew from this set of facts,” Quinn said. They went to Weinberg, whose comments helped clarify their thinking and, she said, “put us on the right track.”

    They realized they could naturally arrive at a zero value for theta by requiring a new symmetry, now known as the Peccei-Quinn mechanism. Besides being one of the popular proposed solutions to the strong CP problem, Peccei-Quinn symmetry also predicts the existence of a hypothetical “axion” particle, which has become a mainstay in theories of supersymmetry and cosmic inflation and has been proposed as a candidate for dark matter.

    Peccei and Quinn discussing their proposed symmetry with the aid of a sombrero. Ryan Schude for Quanta Magazine

    That year at Stanford, Quinn and Peccei regularly interacted with the theory group at the Stanford Linear Accelerator Center (SLAC) as well as with another group from the University of California, Santa Cruz.

    “We formed a large and active group of theorists, which created a wonderful atmosphere of open discussion and collaboration,” Quinn said, adding that she recalls “riding with Roberto back and forth from Stanford to SLAC in his yellow and clunky Jeep, talking physics ideas as we went.”

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

  • richardmitnick 9:29 pm on June 7, 2017 Permalink | Reply
    Tags: , , , Belle, , , , , , SLAC, Vera Lüth,   

    From SLAC: Women in STEM – “Q&A: SLAC’s Vera Lüth Discusses the Search for New Physics” 

    SLAC Lab

    June 7, 2017
    Manuel Gnida

    Vera Lüth, professor emerita of experimental particle physics at SLAC. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Data from BABAR, Belle and LHCb experiments hint at phenomena beyond the Standard Model of particle physics.


    An electron-positron annihilation producing a pair of B mesons as recorded by the BABAR detector at the PEP-II storage rings. Among the reconstructed curved particle tracks is a muon (bottom left). The direction of the associated anti-neutrino (dashed arrow) is identified as missing momentum. Both particles originate from the same B-meson decay. (SLAC National Accelerator Laboratory)

    KEK Belle detector, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan

    CERN LHCb chamber, LHC

    The Standard Model of particle physics describes the properties and interactions of the constituents of matter.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    The development of this theory began in the early 1960s, and in 2012 the last piece of the puzzle was solved by the discovery of the Higgs boson at the Large Hadron Collider (LHC) at CERN in Switzerland.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event


    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Experiments have confirmed time and again the Standard Model’s very accurate predictions.

    Yet, researchers have reasons to believe that physics beyond the Standard Model exists and should be found. For instance, the Standard Model does not explain why matter dominates over antimatter in the universe. It also does not provide clues about the nature of dark matter – the invisible substance that is five times more prevalent than the regular matter we observe.

    In this Q&A, particle physicist Vera Lüth discusses scientific results that potentially hint at physics beyond the Standard Model. The professor emerita of experimental particle physics at the Department of Energy’s SLAC National Accelerator Laboratory is co-author of a review article published today in Nature that summarizes the findings of three experiments: BABAR at SLAC, Belle in Japan and LHCb at CERN.

    What are the hints of new physics that you describe in your article?

    The hints originate from studies of an elementary particle, known as the B meson – an unstable particle produced in the collision of powerful particle beams. More precisely, these studies looked at decays of the B meson that involve leptons – electrically charged elementary particles and their associated neutrinos. There are three charged leptons: the electron, a critical component of atoms discovered in 1897; the muon, first observed in cosmic rays in 1937; and the much heavier tau, discovered at the SPEAR electron-positron (e+e-) storage ring at SLAC in 1975 by Martin Perl.

    Due to their very different masses, the three leptons also have very different lifetimes. The electron is stable, whereas the muon and tau decay in a matter of microseconds and a fraction of a picosecond, respectively. A fundamental assumption of the Standard Model is that the interactions of the three charged leptons are the same if their different masses and lifetimes are taken into account.

    Over many years, different experiments have tested this assumption – referred to as “lepton universality” – and to date no definite violation of this rule has been observed. We now have indications that the rates for B meson decays involving tau leptons are larger than expected compared to the measured rates of decays involving electrons or muons, taking into account the differences in mass. This observation would violate lepton universality, a fundamental assumption of the Standard Model.

    What does a violation of the Standard Model actually mean?

    It means that there is evidence for phenomena that we cannot explain in the context of the Standard Model. If such a phenomenon is firmly established, the Standard Model needs to be extended – by introducing new fundamental particles and also new interactions related to these particles.

    In recent years, searches for fundamentally new phenomena have relied on high-precision measurements to detect deviations from Standard Model predictions or on searches for new particles or interactions with properties that differ from known ones.

    What exactly are the BABAR, Belle and LHCb experiments?

    They are three experiments that have challenged lepton universality.

    Belle and BABAR were two experiments specifically designed to study B mesons with unprecedented precision – particles that are five times heavier than the proton and contain a bottom or b quark. These studies were performed at e+e- storage rings that are commonly referred to as B factories and operate at colliding-beam energies just high enough to produce a pair of B mesons, and no other particle. BABAR operated at SLAC’s PEP-II from 1999 to 2008, Belle at KEKB in Japan from 1999 to 2010. The great advantage of these experiments is that the B mesons are produced pairwise, each decaying into lighter particles – on average five charged particles and a similar number of photons.

    The LHCb experiment is continuing to operate at the proton-proton collider LHC with energies that exceed the ones of B factories by more than a factor of 1,000. At this higher energy, B mesons are produced at a much larger rate than at B factories. However, at each crossing of the beams, hundreds of other particles are produced in addition to B mesons. This feature tremendously complicates the identification of B meson decays.

    To study lepton universality, all three experiments focus on B decays involving a charged lepton and an associated neutrino. A neutrino doesn’t leave a trace in the detector, but its presence is detected as missing energy and momentum in an individual B decay.

    What evidence do you have so far for a potential violation of lepton universality?

    All three experiments have identified specific B meson decays and have compared the rates of decays involving an electron or muon to those involving the higher mass tau lepton. All three experiments observe higher-than-expected decay rates for the decays with a tau. The average value of the reported results, taking into account the statistical and systematic uncertainties, exceeds the Standard Model expectation by four standard deviations.

    This enhancement is intriguing, but not considered sufficient to unambiguously establish a violation of lepton universality. To claim a discovery, particle physicists generally demand a significance of at least five standard deviations. However, the fact that this enhancement was detected by three experiments, operating in very different environments, deserves attention. Nevertheless, more data will be needed, and are expected in the not too distant future.

    What was your role in this research?

    As the technical coordinator of the BABAR collaboration during the construction of the detector, I was the liaison between the physicists and the engineering teams, supported by the BABAR project management team at SLAC. With more than 500 BABAR members from 11 countries, this was a challenging task, but with the combined expertise and dedication of the collaboration the detector was completed and ready to take data in four years.

    Once data became available, I rejoined SLAC’s Research Group C and took over its leadership from Jonathan Dorfan. As convener of the physics working group on B decays involving leptons, I coordinated various analyses by scientists from different external groups, among them SLAC postdocs and graduate students, and helped to develop the analysis tools needed for precision measurements.

    Almost 10 years ago, we started updating an earlier analysis performed under the leadership of Jeff Richman of the University of California, Santa Barbara on B decays involving tau leptons and extended it to the complete BABAR data set. This resulted in the surprisingly large decay rate. The analysis was the topic of the PhD thesis of my last graduate student, Manuel Franco Sevilla, who over the course of four years made a number of absolutely critical contributions that significantly improved the precision of this measurement, and thereby enhanced its significance.

    What keeps you excited about particle physics?

    Over the past 50 years that I have been working in particle physics, I have witnessed enormous progress in theory and experiments leading to our current understanding of matter’s constituents and their interactions at the most fundamental level. But there are still many unanswered questions, from very basic ones like “Why do particles have certain masses and not others?” to questions about the grand scale of things, such as “What is the origin of the universe, and is there more than one?”

    Lepton universality is one of the Standard Model’s fundamental assumptions. If it were violated, unexpected new physics processes must exist. This would be a major breakthrough – even more surprising than the discovery of the Higgs boson, which was predicted to exist many decades ago.

    What results do you expect in the near future?

    There is actually a lot going on in the field. LHCb researchers are collecting more data and will try to find out if the lepton universality is indeed violated. My guess is that we should know the answer by the end of this year. A confirmation will be a great event and will undoubtedly trigger intense experimental and theoretical research.

    At present we do not understand the origin of the observed enhancement. We first assumed that it could be related to a charged partner of the Higgs boson. Although the observed features did not match the expectations, an extension of the Higgs model could do so. Another possible explanation that can neither be confirmed nor excluded is the presence of so-called lepto-quarks. These open questions will remain a very exciting topic that need to be addressed by experiments and theoretical work.

    Recently, LHCb scientists have reported an interesting result indicating that certain B meson decays more often include an electron pair than a muon pair. However, the significance of this new finding is only about 2.6 standard deviations, so it’s too early to draw any conclusions. BABAR and Belle have not confirmed this observation.

    At the next-generation B factory, Super-KEKB in Japan, the new Belle II experiment is scheduled to begin its planned 10-year research program in 2018. The expected very large new data sets will open up many opportunities for searches for these and other indications of physics beyond the Standard Model.

    Super-KEKB in Japan

    Belle II at the SuperKEKB accelerator complex at KEK in Tsukuba, Ibaraki Prefecture, Japan

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    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 8:05 am on April 27, 2017 Permalink | Reply
    Tags: , , Paul Fuoss, SLAC,   

    From SLAC: “Where Scientist Meets Machine: A Fresh Approach to Experimental Design at SLAC X-Ray Laser” 

    SLAC Lab

    April 26, 2017
    Glennda Chui

    Paul Fuoss, the new head of experimental design at SLAC’s Linac Coherent Light Source X-ray laser. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Paul Fuoss’s Mission is to Make Experiments at LCLS and Other Light Sources More Productive and User-Friendly

    Big leaps in technology require big leaps in design ­– entirely new approaches that can take full advantage of everything the technology has to offer.

    That’s the thinking behind a new initiative at the Department of Energy’s SLAC National Accelerator Laboratory. To make sure experimenters can get the most out of a major X-ray laser upgrade that will produce beams that are 10,000 times brighter and pulses up to a million times per second, the lab has created a new position – head of experimental design at the Linac Coherent Light Source – and hired a world-renowned X-ray scientist to fill it.

    The first 21 of 33 undulators in place in the LCLS Undulator Hall. (Photo by Mike Zurawel.)

    Paul Fuoss (pronounced “foos”) will look at LCLS and the LCLS-II upgrade from a fresh perspective and work with scientists and engineers across the lab to design instruments, user-friendly control systems and experimental flows that take full advantage of this technological leap.


    Although the upgrade won’t be finished until the early 2020s, there’s really no time to lose, said LCLS Director Mike Dunne.

    “We’re on the verge of a transformation of our science capabilities that is simply unattainable today. When you take these big leaps you have to fundamentally rethink how you approach the science and the design of experiments,” Dunne said.

    “You can’t just do it the way you did before but a bit better. You have to approach it from a completely new thought process: What is the scientific knowledge you’re trying to get out, and what is the scientific data that might illuminate that new understanding, and how does that translate back into how you obtain that data, and how does that influence how you design the facility?”

    Taming Complexity to Make Science More Productive

    For Fuoss, the broader goal is to increase productivity and improve the experiences of scientists at X-ray light sources everywhere.

    “Experiments have gotten a lot more complex over the past 20 years, not just at LCLS but at synchrotron light sources, too,” he said. “We’ve gone from controlling experiments with a single computer and detecting a single pixel of data at a time to using multiple computers and detecting more like a million pixels at once. Our ability to integrate different tools and computers and visualize the data has often not kept up with the technology. And at LCLS, that complexity is going to increase dramatically in a few years when the LCLS-II upgrade becomes operational.”

    One way to make working with LCLS more streamlined and intuitive is to incorporate user-friendly features into the instruments that come on board as part of LCLS-II.

    “A lot of that will be working with the scientists and engineers who are designing those instruments to get the building blocks for user compatibility in there,” Fuoss said. “It’s not part of the core training of scientists and engineers, so we expect we will need to reach out to people who have that expertise and get them to help us.”

    Another way, he said, is to create tools that let scientists visualize their data as it’s being collected, so they can understand what is going on in real time.

    “There are a lot of different pieces that need to be coordinated,” Fuoss said. “All of them are currently being done, but we need to bring a unified focus and make sure there are no unnecessary barriers. Ultimately, you want to integrate this kind of thing into everyone’s day-to-day development activities.”

    X-Rays, Inventions and Human Interfaces

    Fuoss has deep roots at SLAC. Originally from South Dakota, where he grew up on a ranch, he earned a degree in physics at South Dakota School of Mines and Technology and came to Stanford University in 1975 for graduate school. He wound up doing his graduate research at SLAC, using X-rays from what later became the Stanford Synchrotron Radiation Lightsource (SSRL) to investigate materials.

    SSRL-Stanford Synchrotron Radiation Lightsource – Stanford University

    After earning a PhD, Fuoss went on to do research at Bell Laboratories, AT&T Laboratories and Argonne National Laboratory. He’s been an active user of SSRL and other light sources and has developed a number of new techniques for exploring materials with X-rays, many of which are now standard at light sources around the world; in 2015 he received SLAC’s Farrel W. Lytle Award for this work. Fuoss also played a role in designing LCLS.

    In the mid-1990s, while a researcher at AT&T Laboratories, Fuoss took a six-year detour into the world of human interface design and human factors research – the study of how people interact with technology, from airplane cockpits to your office copier. Back then, he focused on making telecommunications systems and web interfaces more user friendly. This experience can also be applied to LCLS experimental design.

    “Paul has an incredible background,” Dunne said. “He brings that deep understanding of the nature of X-ray science, an understanding of all the instruments and the technical pieces, and then an understanding of what we’re trying to achieve scientifically.”

    Getting the Most out of Beam Time

    Unlike synchrotron light sources, which may have dozens of X-ray beamlines and many experiments going on simultaneously, the current version of LCLS has just one powerful beam, a billion times brighter than any available before, whose pulses arrive up to 120 times per second. In theory this limits the facility to doing one experiment at a time.

    But in the seven years since it opened, scientists and engineers have come up with a number of ways to get around that limitation, such as splitting the beam so it can be delivered to two or more experiments at once. At the same time, they reduced the down time between experiments by scheduling similar experiments back to back, so they don’t have to change out equipment as often. These and other measures increased the number of experiments run per year by 72 percent from 2014 to 2016, and LCLS recently passed the milestone of hosting more than 1,000 users per year.

    LCLS-II will add a second X-ray laser beam, further increasing the facility’s capacity. By continuing to find ways to squeeze in more experiments while making the way people interact with LCLS more straightforward, Fuoss said, “We can improve productivity and allow the scientific users to have a more hands-on role in the actual data collection. That will both reduce the load on the LCLS staff and lead to a better experience for the scientists who are coming here to use it.“

    LCLS and SSRL are DOE Office of Science User Facilities.

    For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    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 8:08 am on April 25, 2017 Permalink | Reply
    Tags: , , SLAC   

    From SLAC: “Machine Learning Dramatically Streamlines Search for More Efficient Chemical Reactions” 

    SLAC Lab

    April 24, 2017
    Glennda Chui

    A diagram shows the many possible paths one simple catalytic reaction can theoretically take – in this case, conversion of syngas, which is a combination of carbon dioxide (CO2) and carbon monoxide (CO), to acetaldehyde. Machine learning allowed SUNCAT theorists to prune away the least likely paths and identify the most likely one (red) so scientists can focus on making it more efficient. (Zachary Ulissi/SUNCAT)

    Even a simple chemical reaction can be surprisingly complicated. That’s especially true for reactions involving catalysts, which speed up the chemistry that makes fuel, fertilizer and other industrial goods. In theory, a catalytic reaction may follow thousands of possible paths, and it can take years to identify which one it actually takes so scientists can tweak it and make it more efficient.

    Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have taken a big step toward cutting through this thicket of possibilities. They used machine learning – a form of artificial intelligence – to prune away the least likely reaction paths, so they can concentrate their analysis on the few that remain and save a lot of time and effort.

    The method will work for a wide variety of complex chemical reactions and should dramatically speed the development of new catalysts, the team reported in Nature Communications.

    ‘A Daunting Task’

    “Designing a novel catalyst to speed a chemical reaction is a very daunting task,” said Thomas Bligaard, a staff scientist at the SUNCAT Center for Interface Science and Catalysis, a joint SLAC/Stanford institute where the research took place. “There’s a huge amount of experimental work that normally goes into it.”

    For instance, he said, finding a catalyst that turns nitrogen from the air into ammonia – considered one of the most important developments of the 20th century because it made the large-scale production of fertilizer possible, helping to launch the Green Revolution – took decades of testing various reactions one by one.

    Even today, with the help of supercomputer simulations that predict the results of reactions by applying theoretical models to huge databases on the behavior of chemicals and catalysts, the search can take years, because until now it has relied largely on human intuition to pick possible winners out of the many available reaction paths.

    “We need to know what the reaction is, and what are the most difficult steps along the reaction path, in order to even think about making a better catalyst,” said Jens Nørskov, a professor at SLAC and Stanford and director of SUNCAT.

    “We also need to know whether the reaction makes only the product we want or if it also makes undesirable byproducts. We’ve basically been making reasonable assumptions about these things, and we really need a systematic theory to guide us.”

    Trading Human Intuition for Machine Learning

    For this study, the team looked at a reaction that turns syngas, a combination of carbon monoxide and hydrogen, into fuels and industrial chemicals. The syngas flows over the surface of a rhodium catalyst, which like all catalysts is not consumed in the process and can be used over and over. This triggers chemical reactions that can produce a number of possible end products, such as ethanol, methane or acetaldehyde.

    “In this case there are thousands of possible reaction pathways – an infinite number, really – with hundreds of intermediate steps,” said Zachary Ulissi, a postdoctoral researcher at SUNCAT. “Usually what would happen is that a graduate student or postdoctoral researcher would go through them one at a time, using their intuition to pick what they think are the most likely paths. This can take years.”

    The new method ditches intuition in favor of machine learning, where a computer uses a set of problem-solving rules to learn patterns from large amounts of data and then predict similar patterns in new data. It’s a behind-the-scenes tool in an increasing number of technologies, from self-driving cars to fraud detection and online purchase recommendations.

    Rapid Weeding

    The data used in this process came from past studies of chemicals and their properties, including calculations that predict the bond energies between atoms based on principles of quantum mechanics. The researchers were especially interested in two factors that determine how easily a catalytic reaction proceeds: How strongly the reacting chemicals bond to the surface of the catalyst and which steps in the reaction present the most significant barriers to going forward. These are known as rate-limiting steps.

    A reaction will seek out the path that takes the least energy, Ulissi explained, much like a highway designer will choose a route between mountains rather than waste time looking for an efficient way to go over the top of a peak. With machine learning the researchers were able to analyze the reaction pathways over and over, each time eliminating the least likely paths and fine-tuning the search strategy for the next round.

    Once everything was set up, Ulissi said, “It only took seconds or minutes to weed out the paths that were not interesting. In the end there were only about 10 reaction barriers that were important.” The new method, he said, has the potential to reduce the time needed to identify a reaction pathway from years to months.

    Andrew Medford, a former SUNCAT graduate student who is now an assistant professor at the Georgia Institute of Technology, also contributed to this research, which was funded by the DOE Office of Science.

    See the full article here .

    Please help promote STEM in your local schools.

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

  • richardmitnick 7:34 am on April 20, 2017 Permalink | Reply
    Tags: SLAC, Virtual tour of LCLS   

    From SLAC: “Virtual Tours of LCLS” 

    SLAC Lab

    The Linac Coherent Light Source (LCLS) at SLAC allows scientists to see the world in femtosecond resolution. Click on the images below to take virtual tours of the Undulator Hall and the Near Experimental Hall (NEH) at LCLS. Also check out our LCLS album on Flickr for photos of the facility.

    Undulator Hall View the video images. Click on the blue circle to navigate.

    Near Experimental Hall View the video images. Click on the blue circle to navigate.

    See the full article here .

    Please help promote STEM in your local schools.

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

  • richardmitnick 1:45 pm on April 18, 2017 Permalink | Reply
    Tags: , , , Gabriella Carini, How do you catch femtosecond light?, , , SLAC, , ,   

    From SLAC: “How do you catch femtosecond light?” 

    SLAC Lab

    Gabriella Carini
    Staff Scientist
    Joined SLAC: 2011
    Specialty: Developing detectors that capture light from X-ray sources
    Interviewed by: Amanda Solliday

    Gabriella Carini enjoys those little moments—after hours and hours of testing in clean rooms, labs and at X-ray beamlines—when she first sees an instrument work.

    She earned her PhD in electronic engineering at the University of Palermo in Italy and now heads the detectors department at the Linac Coherent Light Source (LCLS), the X-ray free-electron laser at SLAC.


    Scientists from around the world use the laser to probe natural processes that occur in tiny slivers of time. To see on this timescale, they need a way to collect the light and convert it into data that can be examined and interpreted.

    It’s Carini’s job to make sure LCLS has the right detector equipment at hand to catch the “precious”, very intense laser pulses, which may last only a few femtoseconds.

    When the research heads in new directions, as it constantly does, this requires her to look for fresh technology and turn these ideas into reality.

    When did you begin working with detectors?

    I moved to the United States as a doctoral student. My professor at the time suggested I join a collaboration at Brookhaven National Laboratory, where I started developing gamma ray detectors to catch radioactive materials.

    Radioactive materials give off gamma rays as they decay, and gamma rays are the most energetic photons, or particles of light. The detectors I worked on were made from cadmium zinc telluride, which has very good stopping power for highly energetic photons. These detectors can identify radioactive isotopes for security—such as the movement of nuclear materials—and contamination control, but also gamma rays for medical and astrophysical observations.

    We had some medical projects going on at the time, too, with detectors that scan for radioactive tracers used to map tissues and organs with positron emission tomography.

    From gamma ray detectors, I then moved to X-rays, and I began working on the earliest detectors for LCLS.

    How do you explain your job to someone outside the X-ray science community?

    I say, “There are three ingredients for an experiment—the source, the sample and the detector.”

    You need a source of light that illuminates your sample, which is the problem you want to solve or investigate. To understand what is happening, you have to be able to see the signal produced by the light as it interacts with the sample. That’s where the detector comes in. For us, the detector is like the “eyes” of the experimental set-up.

    What do you like most about your work?


    There’s always a way we can help researchers optimize their experiments, tweak some settings, do more analysis and correction.

    This is important because scientists are going to encounter a lot of different types of detectors if they work at various X-ray facilities.

    I like to have input from people who are running the experiments. Because I did experiments myself as a graduate student, I’m very sensitive to whether a system is user-friendly. If you don’t make something that researchers can take the best advantage of, then you didn’t do your job fully.

    And detectors are never perfect, no matter which one you buy or build.

    There are a lot of people who have to come together to make a detector system. It’s not one person’s work. It’s many, many people with lots of different expertise. You need to have lots of good interpersonal skills.

    What are some of the challenges of creating detectors for femtosecond science?

    In more traditional X-ray sources the photons arrive distributed over time, one after the other, but when you work with ultrafast laser pulses like the ones from LCLS, all your information about a sample arrives in a few femtoseconds. Your detector has to digest this entire signal at once, process the information and send it out before another pulse comes. This requires deep understanding of the detector physics and needs careful engineering. You need to optimize the whole signal chain from the sensor to the readout electronics to the data transmission.

    We also have mechanical challenges because we have to operate in very unusual conditions: intense optical lasers, injectors with gas and liquids, etc. In many cases we need to use special filters to protect the detectors from these sources of contamination.

    And often, you work in vacuum. With “soft” or low-energy X-rays, they are absorbed very quickly in air. Your entire system has to be vacuum-compatible. With many of our substantial electronics, this requires some care.

    So there are lots of things to take into account. Those are just a few examples. It’s very complicated and can vary quite a bit from experiment to experiment.

    Is there a new project you are really excited about?

    All of LCLS-II—this fills my life! We’re coming up with new ideas and new technologies for SLAC’s next X-ray laser, which will have a higher firing rate—up to a million pulses per second. For me, this is a multidimensional puzzle. Every science case and every instrument has its own needs and we have to find a route through the many options and often-competing parameters to achieve our goals.

    X-ray free-electron lasers are a big driver for detector development. Ten years ago, no one would have talked about X-ray cameras delivering 10,000 pictures per second. The new X-ray lasers are really a game-changer in developing detectors for photon science, because they require detectors that are just not readily available.

    LCLS-II will be challenging, but it’s exciting. For me, it’s thinking about what we can do now for the very first day of operation. And while doing that, we need to keep pushing the limits of what we have to do next to take full advantage of our new machine.



    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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

  • richardmitnick 3:55 pm on April 17, 2017 Permalink | Reply
    Tags: , , , , SLAC, , , ,   

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

    SLAC Lab

    September 22, 2016

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

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

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

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


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

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

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

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

    Turning Heat into Electricity and Vice Versa

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

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

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

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

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

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

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

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

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

    Controlling Materials by Stimulating Charged Waves

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

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

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

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

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

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

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

    A Bright Future for Studies of the Electron-Phonon Dance

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

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

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

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


    SACLA Free-Electron Laser Riken Japan

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

    See the full article here .

    Please help promote STEM in your local schools.

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

  • richardmitnick 9:23 pm on April 11, 2017 Permalink | Reply
    Tags: , , , , SLAC, , , Theory Institute for Materials and Energy Spectroscopies (TIMES), ,   

    From SLAC: “New SLAC Theory Institute Aims to Speed Research on Exotic Materials at Light Sources” 

    SLAC Lab

    April 11, 2017
    Glennda Chui

    A new institute at the Department of Energy’s SLAC National Accelerator Laboratory is using the power of theory to search for new types of materials that could revolutionize society – by making it possible, for instance, to transmit electricity over power lines with no loss.

    The Theory Institute for Materials and Energy Spectroscopies (TIMES) focuses on improving experimental techniques and speeding the pace of discovery at West Coast X-ray facilities operated by SLAC and by Lawrence Berkeley National Laboratory, its DOE sister lab across the bay.

    But the institute aims to have a much broader impact on studies aimed at developing new materials for energy and other technological applications by making the tools it develops available to scientists around the world.

    TIMES opened in August 2016 as part of the Stanford Institute for Materials and Energy Sciences (SIMES), a DOE-funded institute operated jointly with Stanford.

    Materials that Surprise

    “We’re interested in materials with remarkable properties that seem to emerge out of nowhere when you arrange them in particular ways or squeeze them down into a single, two-dimensional layer,” says Thomas Devereaux, a SLAC professor of photon science who directs both TIMES and SIMES.

    This general class of materials is known as “quantum materials.” Some of the best-known examples are high-temperature superconductors, which conduct electricity with no loss; topological insulators, which conduct electricity only along their surfaces; and graphene, a form of pure carbon whose superior strength, electrical conductivity and other surprising qualities derive from the fact that it’s just one layer of atoms thick.

    In another research focus, Devereaux says, “We want to see what happens when you push materials far beyond their resting state – out of equilibrium, is the way we put it – by exciting them in various ways with pulses of X-ray light at facilities known as light sources.

    “This tells you how materials will behave under realistic operating conditions, for instance in a lightweight airplane or a new type of battery. Understanding and controlling out-of-equilibrium behavior and learning how novel properties emerge in complex materials are two of the scientific grand challenges in our field, and light sources are ideal places to do this work.”

    Joining Forces With Light Sources

    A key part of the institute’s work is to use theory and computation to improve experimental techniques – especially X-ray spectroscopy, which probes the chemical composition and electronic structure of materials – in order to make research at light sources more productive.

    “We are in a golden age of X-ray spectroscopy, in which many billions of dollars have been invested worldwide to develop new X-ray and neutron sources that allow us to study very small details and very fast processes in materials,” Devereaux says. “In fact, we are on the threshold of being able to control matter at a much deeper level than ever possible before.

    “But while X-ray spectroscopy has a long history of collaboration between experimentalists and theorists, there has not been a companion theory institute anywhere. TIMES fills this gap. It aims to solidify collaboration and development of new methods and tools for theory relevant to this new landscape.”

    Devereaux, a theorist who uses computation to study quantum materials, came to SLAC 10 years ago from the University of Waterloo in Canada to work more closely with researchers at three light sources – SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), Berkeley Lab’s Advanced Light Source (ALS) and the Linac Coherent Light Source (LCLS), the world’s first X-ray free-electron laser, which at the time was under construction at SLAC. Opened for research in 2009, LCLS gives scientists access to pulses a billion times brighter than any available before and that arrive up to 120 times per second, opening whole new avenues for research.





    With LCLS, Devereaux says, “It became clear that we had an unprecedented opportunity to study materials that have been pushed farther away from equilibrium than was ever possible before.”

    Basic Questions and Practical Answers

    The DOE-funded theory institute has hired two staff scientists, Chunjing Jia and Das Pemmaraju, and works closely with SLAC staff scientists Brian Moritz and Hongchen Jiang and with a number of scientists at the three light sources.

    “We have two main goals,” Jia says. “One is to use X-ray spectroscopy and other techniques to look at practical materials, like the ones in batteries – to study the charging and discharging process and see how the structure of the battery changes, for instance. The second is to understand the fundamental underlying physics principles that govern the behavior of materials.”

    Eventually, she added, theorists want to understand those physics principles so well that they can predict the results of high-priority experiments at facilities that haven’t even been built yet – for instance at LCLS-II, a major upgrade to LCLS that will add a much brighter X-ray laser beam that fires up to a million pulses per second. These predictions have the potential to make experiments at new facilities much more productive and efficient.

    Running Experiments in Supercomputers

    Theoretical work can involve a lot of math and millions of hours of supercomputer time, as theorists struggle to clarify how the fundamental laws of quantum mechanics apply to the materials they are investigating, Pemmaraju says.

    “We use these laws in a form that can be simulated on a computer to make predictions about new materials and their properties,” he says. “The full richness and complexity of the theory are still being discovered, and its equations can only be solved approximately with the aid of supercomputers.”

    Jia adds that you can think of these computer simulations as numerical experiments – working “in silico,” rather than at a lab bench. By simulating what’s going on in a material, scientists can decide which of all the experimental options are the best ones, saving both time and money.

    The institute’s core research team includes theorists Joel Moore of the University of California, Berkeley and John Rehr of the University of Washington. Rehr is the developer of FEFF, an efficient and widely accessible software code that is used by the X-ray light source community worldwide. Devereaux says the plan is to establish a center for FEFF within the institute, which will serve as a home for its further development and for making those advances widely available to theorists and experimentalists at various levels of sophistication.

    TIMES and SIMES are funded by the DOE Office of Science, and the three light sources – ALS, SSRL and LCLS – are DOE Office of Science User Facilities.

    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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