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  • richardmitnick 8:49 pm on January 31, 2017 Permalink | Reply
    Tags: SLAC,   

    From SLAC: “Taking Down a Giant: 699 Tons of SLAC’s Accelerator Removed for Upgrade” 


    SLAC Lab

    January 31, 2017

    For the first time in more than 50 years, a door that is opened at the western end of the historic linear accelerator at the Department of Energy’s SLAC National Accelerator Laboratory casts light on four empty walls stretching as far as the eye can see.

    This end of the linac – a full kilometer of it – has been stripped of all its equipment both above and below ground. Over the next two years it will be re-equipped with new technology to power another wonder of modern science: an X-ray laser that will fire a million pulses per second.

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    Illustration of an electron beam traveling through a niobium cavity – a key component of SLAC’s future LCLS-II X-ray laser. Kept at minus 456 degrees Fahrenheit, a temperature at which niobium conducts electricity without losses, these cavities will power a highly energetic electron beam that will create up to 1 million X-ray flashes per second – more than any other current or planned X-ray laser. (SLAC National Accelerator Laboratory)

    “It was a tremendous effort by the project team and contractors,” Javier Sevilla, project manager for equipment removal, said. “From July to December, 50 workers a day were on site to disassemble and clear the gallery and tunnel.”

    “It was a tremendous effort by the project team and contractors,” Javier Sevilla, project manager for equipment removal, said. “From July to December, 50 workers a day were on site to disassemble and clear the gallery and tunnel.””It was a tremendous effort by the project team and contractors,” Javier Sevilla, project manager for equipment removal, said. “From July to December, 50 workers a day were on site to disassemble and clear the gallery and tunnel.”


    Access mp4 video here.

    The 2-mile linac is a familiar sight to motorists who pass over it on Interstate 280 near Sand Hill Road in Menlo Park. For decades, it accelerated electrons for experiments that explored the fundamental nature of matter and resulted in three Nobel prizes: two for the discovery of subatomic particles and one for confirming that protons and neutrons are made of quarks.

    Starting in 2006, the final kilometer was converted into the Linac Coherent Light Source, a DOE Office of Science User Facility that uses the original accelerator equipment to generate X-ray pulses for a free-electron laser.

    Starting in 2006, the final kilometer was converted into the Linac Coherent Light Source, a DOE Office of Science User Facility that uses the original accelerator equipment to generate X-ray pulses for a free-electron laser.

    Based on the extraordinary success of LCLS to date, the DOE recently approved a billion-dollar upgrade, LCLS-II, that will require the installation of a new, superconducting accelerator, to be built at the west end of the linac.

    699 Tons in 106 Truckloads

    The first one-third of the accelerator housing, located 25 feet below ground, has been stripped of aluminum alignment pipes, copper accelerator tubes and a complex maze of cables and electronics that turned a physicist’s dream into the first beams of accelerating electrons in 1965.

    Over the past several months, 699 tons of materials were removed from tunnel and gallery, amounting to 106 truckloads, according to Carole Fried, deputy project manager for the removal and disposition of the equipment.

    “More than half – about 59 percent – was recycled,” she said. “Over 400 tons of steel, scrap metal, wire, copper and aluminum, representing a value of more than $250,000.”

    The bulk of the equipment that was removed had been installed in the original 1960s linac construction. (For a detailed look at the accelerator fabrication, see this 1967 film.) The accelerator underwent numerous changes over the decades, however, including the addition of the SLAC Energy Doublers, which boosted the power to the accelerator in the 1970s, and the installation of upgraded klystrons – microwave tubes that power the accelerator – as part of the SLAC Linear Collider constructed in 1983.

    “Over the years many of the controls electronics have been replaced as well, so we removed components from every era of SLAC’s operation,” SLAC’s Scott DeBarger said.

    DeBarger oversaw the relocation of equipment before equipment removal began. Between April and July, more than 5,000 items were recovered– including klystrons, magnets, copper waveguides, vacuum pumps, control systems, position monitors and more – to be used in current and future projects at the lab.

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    LCLS-II. The Future is Supercool

    Later this year, the empty tunnel will be refurnished with state-of-the-art cryomodules that will form the superconducting portion of the upgrade to SLAC’s Linac Coherent Light Source, known as LCLS-II. The modules will be filled with liquid helium to cool the cavities to a chilly minus 456 degrees Fahrenheit. The ultracold technology will be used to create bursts of high-energy electrons 8,000 times faster than its predecessor and generate X-ray beams that are 10,000 times brighter.

    The cryomodules are being built at Fermi National Accelerator Laboratory [FNAL] and the Thomas Jefferson National Accelerator Facility [JLab].

    4
    Working on the string of the LCLS-II prototype cryomodule at FNAL.

    Before they are delivered to SLAC and installed, new infrastructure will go into the accelerator tunnel, including hookups to water and power. Above ground, solid-state microwave amplifiers will replace klystrons in the gallery.

    “LCLS-II is an impressive undertaking that relies on many teams, multiple successful phases and important collaborations with our partners – Argonne National Laboratory, Lawrence Berkeley National Lab, Fermilab and Jefferson Lab – and Cornell University,” said John Galayda, head of the LCLS-II project team. “We are making steady progress toward the start of operations in 2020.

    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.

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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.
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  • richardmitnick 3:21 pm on December 26, 2016 Permalink | Reply
    Tags: , , , , Researchers Use World's Smallest Diamonds to Make Wires Three Atoms Wide, SLAC   

    From SLAC: “Researchers Use World’s Smallest Diamonds to Make Wires Three Atoms Wide” 


    SLAC Lab

    December 26, 2016

    LEGO-style Building Method Has Potential for Making One-Dimensional Materials with Extraordinary Properties

    1
    Fuzzy white clusters of nanowires on a lab bench, with a penny for scale. Assembled with the help of diamondoids, the microscopic nanowires can be seen with the naked eye because the strong mutual attraction between their diamondoid shells makes them clump together, in this case by the millions. At top right, an image made with a scanning electron microscope shows nanowire clusters magnified 10,000 times. (SEM image by Hao Yan/SIMES; photo by SLAC National Accelerator Laboratory)

    Scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to use diamondoids – the smallest possible bits of diamond – to assemble atoms into the thinnest possible electrical wires, just three atoms wide.

    By grabbing various types of atoms and putting them together LEGO-style, the new technique could potentially be used to build tiny wires for a wide range of applications, including fabrics that generate electricity, optoelectronic devices that employ both electricity and light, and superconducting materials that conduct electricity without any loss. The scientists reported their results today in Nature Materials.

    “What we have shown here is that we can make tiny, conductive wires of the smallest possible size that essentially assemble themselves,” said Hao Yan, a Stanford postdoctoral researcher and lead author of the paper. “The process is a simple, one-pot synthesis. You dump the ingredients together and you can get results in half an hour. It’s almost as if the diamondoids know where they want to go.”

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    This animation shows molecular building blocks joining the tip of a growing nanowire. Each block consists of a diamondoid – the smallest possible bit of diamond – attached to sulfur and copper atoms (yellow and brown spheres). Like LEGO blocks, they only fit together in certain ways that are determined by their size and shape. The copper and sulfur atoms form a conductive wire in the middle, and the diamondoids form an insulating outer shell. (SLAC National Accelerator Laboratory)

    The Smaller the Better

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    Illustration of a cluster of nanowires assembled by diamondoids
    An illustration shows a hexagonal cluster of seven nanowires assembled by diamondoids. Each wire has an electrically conductive core made of copper and sulfur atoms (brown and yellow spheres) surrounded by an insulating diamondoid shell. The natural attraction between diamondoids drives the assembly process. (H. Yan et al., Nature Materials)

    Although there are other ways to get materials to self-assemble, this is the first one shown to make a nanowire with a solid, crystalline core that has good electronic properties, said study co-author Nicholas Melosh, an associate professor at SLAC and Stanford and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.

    The needle-like wires have a semiconducting core – a combination of copper and sulfur known as a chalcogenide – surrounded by the attached diamondoids, which form an insulating shell.

    Their minuscule size is important, Melosh said, because a material that exists in just one or two dimensions – as atomic-scale dots, wires or sheets – can have very different, extraordinary properties compared to the same material made in bulk. The new method allows researchers to assemble those materials with atom-by-atom precision and control.

    The diamondoids they used as assembly tools are tiny, interlocking cages of carbon and hydrogen. Found naturally in petroleum fluids, they are extracted and separated by size and geometry in a SLAC laboratory. Over the past decade, a SIMES research program led by Melosh and SLAC/Stanford Professor Zhi-Xun Shen has found a number of potential uses for the little diamonds, including improving electron microscope images and making tiny electronic gadgets.

    4
    Stanford graduate student Fei Hua Li, left, and postdoctoral researcher Hao Yan in one of the SIMES labs where diamondoids – the tiniest bits of diamond – were used to assemble the thinnest possible nanowires. (SLAC National Accelerator Laboratory)

    Constructive Attraction

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    Ball-and-stick models of diamondoid atomic structures in the SIMES lab at SLAC. SIMES researchers used the smallest possible diamondoid – adamantane, a tiny cage made of 10 carbon atoms – to assemble the smallest possible nanowires, with conductive cores just three atoms wide. (SLAC National Accelerator Laboratory)

    For this study, the research team took advantage of the fact that diamondoids are strongly attracted to each other, through what are known as van der Waals forces. (This attraction is what makes the microscopic diamondoids clump together into sugar-like crystals, which is the only reason you can see them with the naked eye.)

    They started with the smallest possible diamondoids – single cages that contain just 10 carbon atoms – and attached a sulfur atom to each. Floating in a solution, each sulfur atom bonded with a single copper ion. This created the basic nanowire building block.

    The building blocks then drifted toward each other, drawn by the van der Waals attraction between the diamondoids, and attached to the growing tip of the nanowire.

    “Much like LEGO blocks, they only fit together in certain ways that are determined by their size and shape,” said Stanford graduate student Fei Hua Li, who played a critical role in synthesizing the tiny wires and figuring out how they grew. “The copper and sulfur atoms of each building block wound up in the middle, forming the conductive core of the wire, and the bulkier diamondoids wound up on the outside, forming the insulating shell.”

    A Versatile Toolkit for Creating Novel Materials

    The team has already used diamondoids to make one-dimensional nanowires based on cadmium, zinc, iron and silver, including some that grew long enough to see without a microscope, and they have experimented with carrying out the reactions in different solvents and with other types of rigid, cage-like molecules, such as carboranes.

    The cadmium-based wires are similar to materials used in optoelectronics, such as light-emitting diodes (LEDs), and the zinc-based ones are like those used in solar applications and in piezoelectric energy generators, which convert motion into electricity.

    “You can imagine weaving those into fabrics to generate energy,” Melosh said. “This method gives us a versatile toolkit where we can tinker with a number of ingredients and experimental conditions to create new materials with finely tuned electronic properties and interesting physics.”

    Theorists led by SIMES Director Thomas Devereaux modeled and predicted the electronic properties of the nanowires, which were examined with X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource, a DOE Office of Science User Facility, to determine their structure and other characteristics.

    The team also included researchers from the Stanford Department of Materials Science and Engineering, Lawrence Berkeley National Laboratory, the National Autonomous University of Mexico (UNAM) and Justus-Liebig University in Germany. Parts of the research were carried out at Berkeley Lab’s Advanced Light Source (ALS)

    LBNL ALS interior
    LBNL ALS

    and National Energy Research Scientific Computing Center (NERSC),

    NERSC CRAY Cori supercomputer
    NERSC

    both DOE Office of Science User Facilities. The work was funded by the DOE Office of Science and the German Research Foundation.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 9:23 am on December 15, 2016 Permalink | Reply
    Tags: , , , , SLAC, , X-ray crystallography,   

    From Stanford: “Masters of Crystallization” 

    Stanford University Name
    Stanford University

    March 24, 2016 [Stanford just put this in social media 12.14.16.]
    Glennda Chui

    When molecules won’t crystallize and technology confounds, who you gonna call?

    1
    Macromolecular Structure Knowledge Center at Stanford’s Shriram Center. From left: Ted Li, T.J. Lane, MSKC Director Marc C. Deller, Nick Cox, Timothy Rhorer, Zachary Rosenthal.

    2
    Researcher Ted Li examines a sample tray full of protein crystals under a microscope. Photo: SLAC National Accelerator Laboratory.

    Biology isn’t just for biologists anymore. That’s nowhere more apparent than in the newly furnished lab in room 097 of the Shriram Center basement, where flasks of bacterial and animal cells, snug in their incubators, are churning out proteins destined for jobs they may not have done in nature.

    Researchers who use this lab span a broad range of backgrounds and interests: Chemists searching for novel antibiotics. Chemical engineers developing biofuels. Doctors seeking new treatments for diabetes.

    Most of these highly skilled researchers have one thing in common: They have no idea how to grow the proteins and other large biomolecules that are essential to their research or how to prepare those proteins for X-ray studies that will reveal their structure and function.

    That’s where Marc Deller comes in.

    “I’m the lab manager, scientist, lab cleaner — I do everything, and I help people who don’t know how to use the equipment,” says Deller, who arrived in August to establish and direct the Macromolecular Structure Knowledge Center (MSKC). “I’m pretty much unboxing things every day and trying to get things plugged in.”

    With a doctorate from Oxford and years of protein-wrangling experience, he’s here to help Stanford faculty and students grow, purify and crystallize proteins and other big biomolecules so they can be probed with the SSRL synchrotron or the LCLS X-ray laser at SLAC National Accelerator Laboratory, just up the hill.

    SLAC/SSRL
    SLAC SSRL Tunnel
    “SLAC/SSRL

    SLAC/LCLS
    SLAC/LCLS

    SLAC jointly funds the center with Stanford ChEM-H, an interdisciplinary institute aimed at understanding human biology at a chemical level, and the services offered at MSKC augment help available from the expert staff at the SLAC X-ray facilities.

    X-ray crystallography has been a revolutionary tool for understanding how living things work, revealing the structures of more than 100,000 proteins, nucleic acids and their complexes over the past few decades and fueling the development of numerous life-saving medications.

    But it’s not always easy, as chemistry graduate student Ted Li can attest. The protein he’s studying — a natural catalyst found in soil bacteria that scientists hope to turn into an antibiotic factory — “is very resistant to crystallization. It’s very floppy and doesn’t want to pack,” says Li, who works in the lab of Chaitan Khosla, professor of chemistry and of chemical engineering. “So I need to find a way to force them to do that. Most of the things I’m doing these days are completely new to me, and Marc is my main mentor. He’ll actually go with me to SLAC and guide me in how to collect my data.”

    In its first six months, MSKC has already helped scientists with two dozen research projects, and Deller is eager to round up more. “From my experience of doing this for 20 years,” he says, “making the protein is definitely a bottleneck.”

    See the full article here .

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 7:49 pm on November 8, 2016 Permalink | Reply
    Tags: , , , SLAC   

    From SLAC: World’s Largest Camera for Astronomy 


    SLAC Lab

    1


    Access mp4 video here .

    Large Synoptic Survey Telescope

    Ranked as the top ground-based national priority for the field for the current decade, LSST is currently under construction in Chile. The U.S. Department of Energy’s SLAC National Accelerator Laboratory is leading the construction of the LSST camera – the largest digital camera ever built for astronomy. SLAC Professor Steven M. Kahn is the overall Director of the LSST project, and SLAC personnel are also participating in the data management. The National Science Foundation is the lead agency for construction of the LSST. Additional financial support comes from the Department of Energy and private funding raised by the LSST Corporation.

    LSST Science Goals
    What Will LSST Look At?

    The LSST will survey the entire visible southern sky every few days for a decade. Its vast public archive of data will dramatically advance our knowledge of the dark energy and dark matter that make up 95 percent of the universe, as well as galaxy formation and potentially hazardous asteroids.

    3

    Dark Matter

    Gravitational lensing is our best tool for finding dark matter. LSST’s power and large field of view will enable us to see weaker lenses, which are more common.

    Read more.

    4

    Dark Energy

    6

    LSST’s 18,000-square-degree coverage of billions of galaxies has the power to test differences in fundamental properties of space and time itself in different directions.

    Read more.

    The Solar System

    7

    The LSST will undertake a thorough exploration of our solar system with two goals in mind: learning how it originally formed, and protecting Earth from hazardous, near-flying asteroids.

    Read more.

    The Milky Way

    8

    Individual stars in the Milky Way and the galaxies nearby can be resolved by the LSST. These stars then provide a fossil record—a Rosetta Stone—that can be decoded to determine how these galaxies formed.

    Read more.

    The Changing Sky

    8

    The LSST will scan the sky repeatedly to great depth, enabling it to both discover new, distant transient events and to study variable objects throughout our universe.

    Read more.

    Camera Design
    Nuts and Bolts

    10

    Camera Overview

    About the size of a small SUV, the LSST camera is the largest camera ever constructed for astronomy. It is a large-aperture, wide-field optical camera that is capable of viewing light from the near ultraviolet to near infrared wavelengths.

    Length 9.8 ft (3 m)
    Height 5.5 ft (1.65 m)
    Weight 6200 lbs (2800 kg)
    Pixel Count 3200 megapixel
    Wavelength Range 320–1050 nm

    Note: 1 nm (nanometer) = 10-9 m or one-billionth of a meter

    Focal Plane

    The focal plane is the heart of the camera, where light from billions of galaxies comes to a focus. It consists of 189 charge-coupled device (CCD) sensors, arranged in a total of 21 3-by-3 square arrays mounted on platforms called rafts. The system is cooled to about -100 °C to minimize noise.

    The 64-cm-wide focal plane corresponds to a 3.5-degree field of view, which means the camera can capture more than 40 times the area of the full moon in the sky with each exposure.

    11

    Filter Changer

    The camera also contains a carousel that holds five on-board filters. Each of the filters can be individually swapped out in under two minutes and up to four times a night with the double-rail auto changer. The system also integrates with a manual load-lock changer to allow for a swap-out of a sixth filter.

    The optimized wavelength range for the LSST camera is 320–1050 nm (near ultraviolet to near infrared). This range is divided into six spectral bands labeled u-g-r-i-z-y, each associated with one of the filters. For example, an infrared, or “i” filter might be used to observe sources obscured by dust, since infrared wavelengths can pass through the dust.

    12

    There is more material here that I could not translate into useful data for thi post.

    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.
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  • richardmitnick 8:18 pm on September 15, 2016 Permalink | Reply
    Tags: , SLAC,   

    From SLAC: “SLAC to Play Key Role in $30 Million DOE Effort to Improve Solar Module Materials” 


    SLAC Lab

    September 15, 2016

    1
    SLAC will lead the DuraMat consortium’s efforts to quickly discover, develop and evaluate new materials for making solar modules cheaper, more efficient and more durable, and to speed up their transfer to industry for commercialization. (iStock)

    2
    Vanessa L. Pool, a postdoctoral researcher at SLAC’s Stanford Synchrotron Radiation Lightsource, with an instrument used to observe how a solar cell’s silver contacts form during high-temperature manufacturing. (SLAC National Accelerator Laboratory)

    The U.S. Department of Energy today announced the launch of the Durable Module Materials National Lab Consortium, or DuraMat, which is designed to accelerate the development and deployment of new, high-performance materials for photovoltaic (PV) modules to lower the cost of electricity generated by solar power while increasing the lifetime of modules in the field. Led by the National Renewable Energy Laboratory (NREL), it includes SLAC National Accelerator Laboratory, Sandia National Laboratories and Lawrence Berkeley National Laboratory, as well as partners from academia and industry.

    SLAC will lead the consortium’s efforts to quickly discover, develop and evaluate new materials for making solar modules cheaper, more efficient and more durable. This effort will focus on accelerating the transfer of new materials and technologies that the consortium develops to industry for commercialization.

    “Our work for the consortium will take advantage of our unique capabilities for probing materials with X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource [SSRL],” a DOE Office of Science User Facility, said Michael Toney, a distinguished staff scientist at SLAC who will lead the consortium’s work in high-throughput materials discovery, characterization and forensics.

    SLAC SSRL Tunnel
    SLAC SSRL

    “These studies reveal how materials work, at an atom-by-atom level, while a solar cell is operating, and by working with theorists and computer scientists we can greatly accelerate the identification of promising new materials for evaluation,” he said. “We also plan to stress test materials used in today’s solar modules under conditions that simulate decades of wear and tear, so we can find out how and why they fail and learn how to make them last much longer.”

    SLAC Chief Technology Officer Mark Hartney, who will lead tech transfer for DuraMat, said, “The goal is to make solar modules last 50 years, so the cost of installing them can be amortized over a much longer time and the levelized cost of the electricity they generate goes down. We have a long history of collaborating with NREL on solar energy materials, including a recent study that looked at how the silver contacts that carry electricity out of the modules form during manufacturing. The aim of our DuraMat research is not only to validate these kinds of new materials and processes, but also to accelerate their acceptance by industry and their inclusion in products.”

    The DOE’s SunShot Initiative will provide DuraMat with an estimated $30 million over five years, subject to appropriations.

    DuraMat is the fourth consortium established as part of the Energy Materials Network (EMN), which was launched in February by the DOE Office of Energy Efficiency and Renewable Energy (EERE). Crafted to give American entrepreneurs and manufacturers a competitive edge in the global race for clean energy, EMN focuses on tackling one of the major barriers to widespread commercialization of clean energy technologies—the design, testing and production of advanced materials. By strengthening and facilitating industry access to unique scientific and technical resources available for developing advanced materials at the DOE national labs, the network will help industry bring these materials to market more quickly.

    Other EMN consortia already in progress are the Lightweight Materials Consortium (LightMat) on lightweight materials for various applications, Electrocatalysis Consortium (ElectroCat) on new catalysts for fuel cells, and Caloric Cooling Consortium (CaloriCool) on refrigerant materials for cooling applications. Three more consortia are anticipated to be announced in fiscal year 2017.

    EERE envisions that dramatically accelerating the development of new PV module materials will clear the way for significant reductions in the cost of solar power. It is expected that DuraMat will lead to dependable, high-performance, low-cost PV module materials and architectures by:

    Developing module technologies that will enable dramatic reductions in the levelized cost of energy from solar power.
    Building a network of active collaborations from within the national laboratories, academia and industry to design, develop and deploy advanced module materials.
    Moving highly promising module materials and technologies from early stages of research to successful deployment in the marketplace at an accelerated rate.

    Overall, the EMN consortia will form a network of advanced materials R&D capabilities and resources that will support the Administration’s commitment to revitalizing American manufacturing and maintaining a competitive edge in the clean energy economy. This effort supports the President’s Materials Genome Initiative, which has been engaged in work to discover, manufacture and deploy advanced materials twice as fast, at a fraction of the cost. EMN also supports the recommendations of the Advanced Manufacturing Partnership 2.0, a White House-convened working group of leaders from industry, academia and labor, which highlighted the importance of producing advanced materials for technologies critical to U.S. competitiveness in manufacturing.

    Developing module technologies that will enable dramatic reductions in the levelized cost of energy from solar power.
    Building a network of active collaborations from within the national laboratories, academia and industry to design, develop and deploy advanced module materials.
    Moving highly promising module materials and technologies from early stages of research to successful deployment in the marketplace at an accelerated rate.

    This article is based in part on a press release issued by EERE.

    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.
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  • richardmitnick 11:03 am on August 31, 2016 Permalink | Reply
    Tags: , , SLAC, SLAC’s High-speed ‘Electron Camera’ Films Atomic Nuclei in Vibrating Molecules   

    From SLAC: “SLAC’s High-speed ‘Electron Camera’ Films Atomic Nuclei in Vibrating Molecules” 


    SLAC Lab

    August 31, 2016

    Method Gives Scientists New Ways to Study Rapid Nuclear Motions in Nature’s Light-dependent Processes

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    Using SLAC’s instrument for ultrafast electron diffraction (UED), researchers were able to directly see the motions of atomic nuclei in vibrating molecules for the first time. (SLAC National Accelerator Laboratory)

    2
    In their UED experiment at SLAC, the researchers shone a laser beam (green) through a cloud of iodine gas (gray) and probed the resulting vibrations of the iodine molecules by taking ultrafast snapshots with an electron beam (blue). The electrons scatter off the atoms in the molecules, generating an intensity pattern (at right) that the team used to determine the distance between the iodine nuclei in iodine molecules. Rapid changes in the pattern revealed the speedy motions of the nuclei. (SLAC National Accelerator Laboratory)

    3
    An electron gun (left), initially designed for SLAC’s X-ray laser LCLS, generates electrons that researchers send through materials (right) to study their structures and motions on the atomic level. (SLAC National Accelerator Laboratory)

    4
    The electron diffraction pattern from iodine molecules depends on the distance between the two iodine nuclei, and changes as the molecule vibrates. (SLAC National Accelerator Laboratory)

    An ultrafast “electron camera” at the Department of Energy’s SLAC National Accelerator Laboratory has made the first direct snapshots of atomic nuclei in molecules that are vibrating within millionths of a billionth of a second after being hit by a laser pulse. The method, called ultrafast electron diffraction (UED), could help scientists better understand the role of nuclear motions in light-driven processes that naturally occur on extremely fast timescales.

    Researchers used the UED instrument’s electron beam to look at iodine molecules at different points in time after the laser pulse. By stitching the images together, they obtained a “molecular movie” that shows the molecule vibrating and the bond between the two iodine nuclei stretching almost 50 percent – from 0.27 to 0.39 millionths of a millimeter – before returning to its initial state. One vibrational cycle took about 400 femtoseconds; one femtosecond, or millionth of a billionth of a second, is the time it takes light to travel a small fraction of the width of a human hair.

    “We’ve pushed the speed limit of the technique so that we can now see nuclear motions in gases in real time,” said co-principal investigator Xijie Wang, SLAC’s lead scientist for UED. “This breakthrough creates new opportunities for precise studies of dynamic processes in biology, chemistry and materials science.”

    The UED method has been under development by a number of groups throughout the world since the 1980s. However, the quality of electron beams has only recently become good enough to enable femtosecond studies. SLAC’s instrument benefits from a high-energy, ultrabright electron source originally developed for the lab’s femtosecond X-ray laser, the Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility.

    The results will be published in Physical Review Letters.

    A Direct Way of Looking at Nuclear Motions

    Physicists have long known that chemical bonds between atoms are flexible – like springs connecting spheres. This flexibility allows molecules to change shape in ways that are crucial for biological and chemical functions, such as vision and photosynthesis. However, methods to study these motions on a femtosecond timescale have so far been indirect.

    Spectroscopy, for example, infers these changes from the way laser light interacts with electron clouds around atomic nuclei, and requires theoretical calculations to turn these data into a picture of the nuclear geometry. This can be done very precisely for small molecules – an accomplishment that earned the late Ahmed Zewail, a pioneer in the field of femtochemistry, the 1999 Nobel Prize in Chemistry – but quickly becomes very challenging for larger molecules.

    Researchers also use X-rays to study ultrafast molecular motions. Although X-rays deeply penetrate the electron clouds, interacting with the electrons closest to the nuclei, they don’t yet do so with high enough resolution to precisely determine the nuclear positions in current femtosecond X-ray studies.

    In contrast, UED uses a beam of very energetic electrons that interacts with both electrons and atomic nuclei in molecules. Therefore, it can directly probe the nuclear geometry with high resolution.

    “We previously used the method to look at the rotation of molecules – a motion that doesn’t change the nuclear structure,” said lead author Jie Yang from SLAC, who was at the University of Nebraska, Lincoln at the time of the study. “Now we have demonstrated that we can also see bond changes due to vibrations.”

    A Molecular Double-slit Experiment

    The concept behind the iodine UED experiment is similar to the classical double-slit experiment often demonstrated in physics classrooms. In that experiment, a laser beam passes through a pair of vertical slits, producing an interference pattern of bright and dark areas on a screen. The pattern depends on the distance between the two slits.

    In the case of UED, an electron beam shines through a gas of iodine molecules, with the distance between the two iodine nuclei in each molecule defining the double slit, and hits a detector instead of a screen. The resulting intensity pattern on the detector is called a diffraction pattern.

    “The characteristic pattern tells us immediately the distance between the nuclei,” said co-principal investigator Markus Guehr from Potsdam University in Germany and the Stanford PULSE Institute. “But we can learn even more. As the iodine molecules vibrate, the diffraction pattern changes, and we can follow the changes in nuclear separation in real time.”

    5
    Comparison of the interference pattern in the classical double-slit experiment (left) with the electron diffraction pattern in the iodine UED experiment at SLAC. For explanations, see text. (SLAC National Accelerator Laboratory)

    A Method with Perspectives

    Co-principal investigator Martin Centurion from the University of Nebraska, Lincoln, said, “What’s also great about our method is that it works for every molecule. Unlike other techniques that depend on the ability to calculate the nuclear structure from the original data, which works best for small molecules, we only need to know the properties of our electron beam and experimental setup.”

    Following their first steps using the relatively simple iodine molecule, the team is now planning to expand their studies to molecules with more than two atoms.

    “The development of UED into a technique that can probe changes in internuclear distances of a dilute gas sample in real time truly is a great achievement,” said Jianming Cao, a UED expert from Florida State University and a former member of the Zewail lab at the California Institute of Technology, who was not involved in the study. “This opens the door to studies of atomic-level motions in many systems – structural dynamics that are at the heart of the correlation between structure and function in matter.”

    The research was funded in part by the DOE Office of Science.


    This animation explains how researchers use high-energy electrons at SLAC to study faster-than-ever motions of atoms and molecules relevant to important material properties and chemical processes. (SLAC National Accelerator Laboratory)

    Press Office Contact:
    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 4:49 pm on August 18, 2016 Permalink | Reply
    Tags: , , Decoy drug could prevent cancer's spread, , SLAC,   

    From Stanford and SLAC: “Decoy drug could prevent cancer’s spread” 

    Stanford University Name
    Stanford University


    SLAC Lab

    March 31, 2016 [This just appeared or re-appeared in social media.]
    By Amy Adams

    1
    A representation of the Axl protein reconstructed from X-ray crystallography data. Illustration: SLAC National Accelerator Laboratory

    Creating a molecular snapshot of the way proteins interact could help development of new cancer drugs

    When new cancer cells break free of their original tumor, they travel the blood system and land in distant organs to kindle new tumors. It’s these new cancer settlements, through a process called metastasis, that are often deadly.

    One approach to preventing that spread has involved blocking the interaction of two proteins: one called Gas6 in the bloodstream and another called Axl that bristles along the outside of cancer cells. When these two interact, it signals the cell to pack up and go.

    Despite the promise, attempts at blocking that interaction haven’t worked.

    Jennifer Cochran, an associate professor of bioengineering, and Amato Giaccia, a professor of radiation oncology, thought they might try an alternate approach. Their idea was to create a decoy Axl protein that would latch onto Gas6 in the bloodstream, sopping up all the available Gas6 and preventing any from being available to bind to the real Axl.

    2
    Protein crystal mounted on the X-Ray beam line with raw data in the background. The data represents the organization of atoms in the crystal. Image: SLAC National Accelerator Laboratory

    To create that drug, the duo made more than 10 million mutations to the Axl protein, then tested those variants to find one that stuck most tightly to Gas6. One in particular stood out. It latched on to Gas6 much more tightly than the normal protein.

    In mice, this Axl decoy protein when injected into the bloodstream sequesters the Gas6 and prevents metastasis in both breast and ovarian cancers. The team is now working to translate that success to people.

    An additional question for Cochran was what changed in their mutated protein to make it so effective. “We wanted to understand the interaction on a deeper level,” she said. “That curiosity is part of being an engineer.”

    Satisfying that curiosity could also help the team understand how the two proteins interact and predict ways of mutating other proteins to create drugs. “The idea is that if you could study this interaction you could use it in a predictive way down the road,” she said.

    Working with Irimpan Mathews, a structural biology scientist at SLAC’s Stanford Synchotron Radiation Lightsource, Cochran and her team formed crystals of the mutant Axl interacting with Gas6.

    SLAC/SSRL
    SLAC/SSRL

    They then used a technique called X-ray crystallography, which essentially creates a molecular portrait of the proteins and their interactions.

    “The crystallography revealed unique features that couldn’t have been predicted,” says Cochran, who is also a member of Stanford Bio-X. The tightest binding variant of Axl had a little pocket that helped it bind even tighter to the Gas6.

    The Stanford-SLAC collaborators are now using similar methods to interfere with two proteins that help blood vessels infiltrate and support tumors, supported by a Stanford ChEM-H program to encourage Stanford faculty collaborations with SLAC.

    See the full article here .

    Please help promote STEM in your local schools.
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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 12:06 pm on August 15, 2016 Permalink | Reply
    Tags: , SLAC, SLAC and Stanford Gadget Grabs More Solar Energy to Disinfect Water Faster   

    From SLAC: “SLAC, Stanford Gadget Grabs More Solar Energy to Disinfect Water Faster” 


    SLAC Lab

    August 15, 2016

    1
    A researcher holds a small, nanostructured device that uses sunlight to disinfect water. By harnessing a broad spectrum of sunlight, it works faster than devices that use only ultraviolet rays. (Jin Xie/Stanford University)

    2
    This nanostructured device, about half the size of a postage stamp, uses sunlight to quickly disinfect water. It consists of thin flakes of molybdenum disulfide arranged like walls on a glass surface and topped with a thin layer of copper. Light falling on the walls triggers formation of hydrogen peroxide (H2O2) and other “reactive oxygen species” that kill bacteria. (C. Liu et al., Nature Nanotechnology)

    3
    An electron micrograph shows the pattern of nanostructured walls on the surface of the device. When the device was dropped into a sample of contaminated water and placed in sunlight, it killed more than 99.999 percent of bacteria in just 20 minutes. (C. Liu et al., Nature Nanotechnology)

    In many parts of the world, the only way to make germy water safe is by boiling, which consumes precious fuel, or by putting it out in the sun in a plastic bottle so ultraviolet rays will kill the microbes. But because UV rays carry only 4 percent of the sun’s total energy, the UV method takes six to 48 hours, limiting the amount of water people can disinfect this way.

    Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have created a nanostructured device, about half the size of a postage stamp, that disinfects water much faster than the UV method by also making use of the visible part of the solar spectrum, which contains 50 percent of the sun’s energy.

    In experiments reported today in Nature Nanotechnology, sunlight falling on the little device triggered the formation of hydrogen peroxide and other disinfecting chemicals that killed more than 99.999 percent of bacteria in just 20 minutes. When their work was done the killer chemicals quickly dissipated, leaving pure water behind.

    “Our device looks like a little rectangle of black glass. We just dropped it into the water and put everything under the sun, and the sun did all the work,” said Chong Liu, lead author of the report. She is a postdoctoral researcher in the laboratory of Yi Cui, a SLAC/Stanford associate professor and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.

    Nanoflake Walls and Eager Electrons

    Under an electron microscope the surface of the device looks like a fingerprint, with many closely spaced lines. Those lines are very thin films – the researchers call them “nanoflakes” – of molybdenum disulfide that are stacked on edge, like the walls of a labyrinth, atop a rectangle of glass.

    In ordinary life, molybdenum disulfide is an industrial lubricant. But like many materials, it takes on entirely different properties when made in layers just a few atoms thick. In this case it becomes a photocatalyst: When hit by incoming light, many of its electrons leave their usual places, and both the electrons and the “holes” they leave behind are eager to take part in chemical reactions.

    By making their molybdenum disulfide walls in just the right thickness, the scientists got them to absorb the full range of visible sunlight. And by topping each tiny wall with a thin layer of copper, which also acts as a catalyst, they were able to use that sunlight to trigger exactly the reactions they wanted – reactions that produce “reactive oxygen species” like hydrogen peroxide, a commonly used disinfectant, which kill bacteria in the surrounding water.

    Molybdenum disulfide is cheap and easy to make – an important consideration when making devices for widespread use in developing countries, Cui said. It also absorbs a much broader range of solar wavelengths than traditional photocatalysts.

    Solving Pollution Problems

    The method is not a cure-all; for instance, it doesn’t remove chemical pollutants from water. So far it’s been tested on only three strains of bacteria, although there’s no reason to think it would not kill other bacterial strains and other types of microbes, such as viruses. And it’s only been tested on specific concentrations of bacteria mixed with less than an ounce of water in the lab, not on the complex stews of contaminants found in the real world.

    Still, “It’s very exciting to see that by just designing a material you can achieve a good performance. It really works,” said Liu, who has gone on to work on a project in Cui’s lab that is developing air filters for combating smog. “Our intention is to solve environmental pollution problems so people can live better.”

    The work was funded by the Department of Energy Office of Science through SIMES, and carried out in collaboration with Professor Alexandria Boehm’s group in the Stanford department of civil and environmental engineering.

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 2:23 pm on August 12, 2016 Permalink | Reply
    Tags: , , Fermi Researchers Explore New Ways of Searching for Dark Matter, , SLAC, Three Studies Expand the Hunt for Unexplained Cosmic Gamma-ray Signals   

    From SLAC: “Fermi Researchers Explore New Ways of Searching for Dark Matter” 


    SLAC Lab

    August 12, 2016

    Three Studies Expand the Hunt for Unexplained Cosmic Gamma-ray Signals

    Researchers working with more than six years of data from NASA’s Fermi Gamma-ray Space Telescope have used novel approaches to search for cosmic signals that could reveal what mysterious dark matter is made of.

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    The scientists looked for hypothetical axion particles, studied the gamma-ray emissions from a large satellite galaxy of our Milky Way and analyzed the faint glow of gamma rays that covers the entire sky.

    Although none of these studies identified signals clearly attributable to dark matter, the results help scientists determine what dark matter cannot be by ruling out numerous theoretical dark matter models.

    “The new approaches have set tight limits on the properties of dark matter, complementing and extending previous results,” says Seth Digel, who leads the Fermi team at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory.

    2

    The nature of invisible dark matter remains one of the biggest mysteries of modern science. Because dark matter makes up 85 percent of all matter in the universe, it affects how galaxies rotate and how light passes through massive galaxy clusters. But what exactly is dark matter, and what are its constituents?

    Astrophysicists do not know the answers, but they believe that dark matter might be composed of hypothetical particles. Gamma rays as detected by the Fermi telescope can potentially help reveal their existence. Previously, Fermi has searched for telltale gamma-ray signals associated with dark matter in the center of our galaxy and in small dwarf galaxies orbiting our own. The new studies take this search to the next level.

    Gamma Rays Turning into Axions and Vice Versa

    The first study investigated the possibility that dark matter consists of hypothetical particles called axions or other contenders with similar properties. An intriguing aspect of axion-like particles is their ability to convert into gamma rays and back again when they interact with strong magnetic fields. These conversions would leave behind characteristic traces, like gaps or steps, in the spectrum of a bright gamma-ray source.

    A team led by Manuel Meyer at Stockholm University searched for these effects in the gamma rays from the central galaxy of the Perseus galaxy cluster, whose high-energy emissions are thought to be associated with a supermassive black hole at its center. Like all galaxy clusters, the Perseus cluster is filled with hot gas threaded with magnetic fields, potentially enabling the switch from gamma rays to axion-like particles and vice versa.

    3
    Top: Gamma rays (magenta) coming from a bright source such as the central galaxy (at left) of the Perseus galaxy cluster have a particular type of spectrum that is detected by the Fermi telescope (at right). Bottom: Gamma rays could potentially convert into hypothetical axion-like particles (green) and back again in the presence of the cluster’s magnetic field (gray lines). This would lead to steps and gaps in the spectrum (lower curve at right). (SLAC National Accelerator Laboratory). (T. Wistisen/Aarhus University)

    Meyer’s team collected observations from Fermi’s Large Area Telescope (LAT) but didn’t find any axion-related distortions in the gamma-ray signal.

    NASA/Fermi LAT
    NASA/Fermi LAT

    The findings, published April 20 in Physical Review Letters, exclude a small range of axion-like particles that could have comprised about 4 percent of dark matter.

    “While we don’t yet know what dark matter is, our results show we can probe axion-like models and provide the strongest constraints to date for certain masses,” Meyer says. “Remarkably, we reached a sensitivity we thought would only be possible in a dedicated laboratory experiment, which is quite a testament to Fermi.”

    WIMPs Decaying or Annihilating Each Other in Space

    Other dark matter candidates are so-called weakly interacting massive particles (WIMPs). In some theoretical models, colliding WIMPs either annihilate each other or decay in space; both scenarios should result in gamma rays that could be detected by the LAT.

    In the second study, scientists sought these signals from the Small Magellanic Cloud (SMC), the second-largest of the satellite galaxies orbiting our Milky Way. The SMC’s conventional sources of gamma rays, such as pulsars and processes related to the formation of massive stars, are well established, and its dark matter content is known from the galaxy’s well-measured rotation.

    “These properties make the SMC a great object for searches for any unexplained gamma-ray excess, which could potentially be a WIMP signature,” says KIPAC researcher Eric Charles, co-author of a paper published on March 22 in Physical Review D.

    4
    The Small Magellanic Cloud (SMC, at center) is the second-largest satellite galaxy orbiting our Milky Way. The image superimposes a photograph of the SMC with one-half of a model of its dark matter. Lighter colors indicate greater density and show a strong concentration of dark matter toward the SMC’s center. Ninety-five percent of the dark matter is contained within a circle tracing the outer edge of the model shown here. (R. Caputo; A. Mellinger/Central Michigan University)

    The researchers modeled the dark matter content of the satellite galaxy, showing it possesses enough dark matter to theoretically produce detectable signals for two WIMP types.

    However, “no signal from dark matter annihilation was found to be statistically significant,” says lead author Regina Caputo from the University of California, Santa Cruz. “The LAT definitely sees gamma rays from the SMC, but we can explain them all through conventional sources.”

    An Extragalactic Glow of Gamma Rays

    In the third study, a research team led by Clemson University’s Marco Ajello and KIPAC’s Mattia Di Mauro took the search in a different direction. Instead of looking at specific astronomical targets, the team analyzed the background glow of gamma rays seen all over the sky.

    The nature of this light, called the extragalactic gamma-ray background (EGB), has been debated since it was first measured by NASA’s Small Astronomy Satellite 2 in the early 1970s.

    5
    This view of the gamma-ray sky is constructed from one year of Fermi Large Area Telescope (LAT) observations. The blue color includes the extragalactic gamma-ray background. The map shows the rate at which the LAT detects gamma rays with energies above 300 million electron volts — about 120 million times the energy of visible light — from different sky directions. Brighter colors represent higher rates. Credit: NASA/DOE/Fermi LAT Collaboration

    Fermi has shown that much of this light arises from gamma-ray sources that cannot be identified as individual sources, particularly galaxies called blazars that are powered by material falling toward gigantic black holes.

    Some models predict that EGB gamma rays could also arise from distant interactions of dark matter particles, such as the annihilation or decay of WIMPs.

    “We performed a statistical analysis of the EGB, in which we looked at very dim objects and asked whether we can account for all detected gamma-ray photons with known astrophysical sources,” says Di Mauro.

    6
    This animation switches between two images of the gamma-ray sky: one using the first three months of data from Fermi’s Large Area Telescope (LAT), the other showing an exposure over seven years. The background glow of gamma rays seen all over the sky (blue contours) is mostly caused by blazars, galaxies that are powered by material falling toward gigantic black holes. With increasing exposure, Fermi reveals more and more of them. (NASA/SLAC National Accelerator Laboratory/Fermi-LAT collaboration)

    The detailed analysis, published April 14 in Physical Review Letters, shows that the researchers can in fact explain nearly all of this emission.

    “There is very little room left for signals from exotic sources in the EGB, which in turn means that any contribution from these sources must be quite small,” Ajello says. “This information may help us place limits on how often WIMP particles collide or decay.”

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States. A number of researchers from SLAC are members of the international Fermi-LAT collaboration. SLAC assembled the LAT and hosts the operations center that processes LAT data.

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 10:20 am on August 8, 2016 Permalink | Reply
    Tags: , Memory chips, SLAC,   

    From Stanford: “Memory chips 1,000 times faster than today’s” 

    Stanford University Name
    Stanford University

    August 8, 2016
    Tom Abate

    1
    This animation shows how data is stored using phase-change memory technology. Phase-change materials can exist in two atomic structures, disordered or ordered. An electric jolt flip-flops these structures back and forth to form the zeroes and ones of digital software. (Image credit: Tricia Seibold)

    Silicon memory chips come in two broad types: volatile memory, such as computer RAM that loses data when the power is turned off, and nonvolatile flash technologies that store information even after we shut off our smartphones.

    In general, volatile memory is much faster than nonvolatile storage, so engineers often balance speed and retention when picking the best memory for the task. That’s why slower flash is used for permanent storage. Speedy RAM, on the other hand, works with processors to store data during computations because it operates at speeds measured in nanoseconds, or billionths of a second.

    Now Stanford-led research shows that an emerging memory technology, based on a new class of semiconductor materials, could deliver the best of both worlds, storing data permanently while allowing certain operations to occur up to a thousand times faster than today’s memory devices. The new approach may also be more energy efficient.

    “This work is fundamental but promising,” said Aaron Lindenberg, an associate professor of materials science and engineering at Stanford and of photon science at the SLAC National Accelerator Laboratory. “A thousandfold increase in speed coupled with lower energy use suggests a path toward future memory technologies that could far outperform anything previously demonstrated.”

    Lindenberg led a 19-member team, including researchers at SLAC, who detailed their experiments in Physical Review Letters [See below for link.]

    Their findings provide new insights into the experimental technology of phase-change memory.

    Entering a new phase

    Today memory chips are commonly based on silicon technologies that efficiently switch electron flows on and off, representing the ones and zeroes that drive digital software. But researchers continue searching for new materials and processes that use less energy and require less space than silicon solutions.

    Phase-change memory is one possible next-generation technology. Scientists have known for some time that certain materials have flexible atomic structures that offer interesting electronic possibilities.

    For instance, phase-change materials can exist in two different atomic structures, each of which has a different electronic state. A crystalline, or ordered, atomic structure, permits the flow of electrons, while an amorphous, or disordered, structure inhibits electron flows.

    Researchers have developed ways to flip-flop the structural and electronic states of these materials – changing their phase from one to zero and back again – by applying short bursts of heat, supplied electrically or optically.

    Phase-change materials are attractive as a memory technology because they retain whichever electronic state conforms to their structure. Once their atoms flip or flop to form a one or a zero, the material stores that data until another energy jolt causes it to change. This ability to retain stored data makes phase-change memory nonvolatile just like the silicon-based flash memory in smartphones.

    But permanent storage is only one desired attribute. A next-generation memory technology also needs to perform certain operations faster than today’s chips. By using extremely precise measurements and instrumentation, the researchers sought to demonstrate the speed and energy potential of phase-change technology – and what they found was encouraging.

    “Nobody had ever been able to investigate these processes on such fast time-scales before,” Lindenberg said.

    A faster phase

    The new research focused on the unimaginably brief interval when an amorphous structure began to switch to crystalline, when a digital zero became a digital one. This intermediate phase – where the charge flows through the amorphous structure like in a crystal – is known as “amorphous on.”

    In the presence of a sophisticated detection system, the Stanford researchers jolted a small sample of amorphous material with an electrical field comparable in strength to a lightning strike. Their instrumentation detected that the amorphous-on state – initiating the flip from zero to one – occurred less than a picosecond after they applied the jolt.

    To comprehend the brevity of a picosecond, it’s roughly the time it would take for a beam of light, traveling at 186,000 miles per second, to pass through two pieces of paper.

    Showing that phase-change materials can be transformed from zero to one by a picosecond excitation suggests that this emerging technology could store data many times faster than silicon RAM for tasks that require memory and processors to work together to perform computations.

    Space is always a consideration in design, and previous experiments have shown that phase-change technology has the potential to pack more data in less space, giving it a favorable storage density.

    Taking energy into account, researchers say the electrical field that triggered the phase change was of such a brief duration that it points toward a storage process that could become more efficient than today’s silicon-based technologies.

    Finally, although this experiment did not establish precisely how much time would be required to completely flip an atomic arrangement from amorphous to crystalline or back, these results suggest that phase-change materials could perform superfast memory chores and permanent storage – depending on how long the thermal excitation is engineered to stay inside the material.

    Much work remains to turn this discovery into functioning memory systems. Nonetheless, attaining such speed using a low-energy switching technique on a material that can store more information in less space suggests that phase-change technology has the potential to revolutionize data storage.

    “A new technology which demonstrate a thousandfold advantage over incumbent technologies is compelling,” Lindenberg said. “I think we’ve shown that phase change deserves further attention.”

    The paper is titled “Picosecond electric-field-induced threshold switching in phase-change materials.” The first authors Peter Zalden and Michael J. Shu did the work while at the Stanford Institute for Materials and Energy Sciences and the PULSE Institute, both affiliated with SLAC. In addition to Stanford collaborators, the team involved researchers from Argonne National Laboratory in Illinois and RWTH Aachen University in Germany.

    See the full article here .

    Please help promote STEM in your local schools.
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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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