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  • richardmitnick 11:38 am on July 6, 2020 Permalink | Reply
    Tags: "New insights into van der Waals materials found", Layered van der Waals materials are of high interest for electronic and photonic applications according to researchers at Penn State and SLAC National Accelerator Laboratory., , SLAC National Accelerator Laboratory, Two-dimensional van der Waals materials are composed of strongly bonded layers of molecules with weak bonding between the layers.   

    From Pennsylvania State University and SLAC National Accelerator Lab: “New insights into van der Waals materials found” 

    Penn State Bloc

    From Pennsylvania State University

    and

    SLAC National Accelerator Lab

    July 03, 2020
    Walt Mills

    1
    The lattice dynamics of monoclinic gallium telluride (GaTe) is studied by ultrafast electro diffraction (UED). This study provides a generalized understanding of Friedel’s law and a comprehensive explanation of the lattice dynamics. Image: Qingkai Qian, Penn State.

    Layered van der Waals materials are of high interest for electronic and photonic applications, according to researchers at Penn State and SLAC National Accelerator Laboratory, in California, who provide new insights into the interactions of layered materials with laser and electron beams.

    Two-dimensional van der Waals materials are composed of strongly bonded layers of molecules with weak bonding between the layers.

    The researchers used a combination of ultrafast pulses of laser light that excite the atoms in a material lattice of gallium telluride, followed by exposing the lattice to an ultrafast pulse of an electron beam. This shows the lattice vibrations in real time using electron diffraction and could lead to a better understanding of these materials.

    “This is a quite unique technique,” said Shengxi Huang, assistant professor of electrical engineering and corresponding author of a paper in ACS Nano that describes their work. “The purpose is to understand fully the lattice vibrations, including in-plane and out-of-plane.”

    One of the interesting observations in their work is the breaking of a law that applies to all material systems. Friedel’s Law posits that in the diffraction pattern, the pairs of centrosymmetric Bragg peaks should be symmetric, directly resulting from Fourier transformation. In this case, however, the pairs of Bragg peaks show opposite oscillating patterns. They call this phenomenon the dynamic breaking of Friedel’s Law. It is a very rare if not unprecedented observation in the interactions between the beams and these materials.

    “Why do we see the breaking of Friedel’s Law?” she said. “It is because of the lattice structure of this material. In layered 2D materials, the atoms in each layer typically align very well in the vertical direction. In gallium telluride, the atomic alignment is a little bit off.”

    When the laser beam shines onto the material, the heating generates the lowest-order longitudinal acoustic phonon mode, which creates a wobbling effect for the lattice. This can affect the way electrons diffract in the lattice, leading to the unique dynamic breaking of Friedel’s law.

    This technique is also useful for studying phase change materials, which absorb or radiate heat during phase change. Such materials can generate the electrocaloric effect in solid-state refrigerators. This technique will also be interesting to people who study oddly structured crystals and the general 2D materials community.

    The lead author on the article, titled “Coherent Lattice Wobbling and Out-of-Phase Intensity Oscillations of Friedel Pairs Observed by Ultrafast Electron Diffraction” is Huang’s postdoctoral scholar Qingkai Qian. Additional Penn State authors in her group are graduate students Kunyan Zhang and Lanxin Jia, and research scholar Yu Zhou. Xijie Wang led the ten-member SLAC team.

    The National Science Foundation supported this work. The Department of Energy supports SLAC.

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    Please help promote STEM in your local schools.

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    SLAC National Accelerator Lab


    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

    Penn State Campus

    About Penn State

    WHAT WE DO BEST

    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

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  • richardmitnick 1:09 pm on June 18, 2020 Permalink | Reply
    Tags: "A new way to study how elements mix deep inside giant planets", An international team has developed a new experimental setup to measure how chemical elements behave and mix deep inside icy giants., SLAC National Accelerator Laboratory, , There are giants among us – gas and ice giants to be specific., X-ray Thomson scattering   

    From Stanford University: “A new way to study how elements mix deep inside giant planets” 

    Stanford University Name
    From Stanford University

    June 16, 2020
    Ali Sundermier

    1
    In a new experiment, four optical laser beams (green) launched a shock wave in a plastic sample made up of carbon and hydrogen. As the shock wave moved through the material, researchers observed it by hitting the shocked regions with X-ray photons from LCLS (thin white beam) that scattered both backwards and forwards off electrons in the sample (thicker white beams). Credit: Greg Stewart/SLAC National Accelerator Laboratory.

    It could offer insights into the evolution of planetary systems and guide scientists hoping to harness nuclear fusion as a new source of energy.

    There are giants among us – gas and ice giants to be specific. They orbit the same star, but their environmental conditions and chemical makeup are wildly different from those of Earth. These enormous planets – Jupiter, Saturn, Neptune and Uranus – can be seen as natural laboratories for the physics of matter at extreme temperatures and pressures.

    Now, an international team that includes scientists from the Department of Energy’s SLAC National Accelerator Laboratory has developed a new experimental setup to measure how chemical elements behave and mix deep inside icy giants, which could offer insights into the formation and evolution of planetary systems. What they learn could also guide scientists hoping to harness nuclear fusion, which produces conditions similar to those in our sun, as a new source of energy. Their results were published last week in Nature Communications.

    Mixing it up

    In previous experiments, researchers used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser to get the first detailed look at the creation of “warm dense matter,” a superhot, supercompressed mixture believed to be at the heart of these enormous planets.

    SLAC/LCLS

    They were also able to collect evidence for “diamond rain,” an exotic precipitation predicted to form from mixtures of elements deep inside icy giants.

    Until now, researchers used a technique called X-ray diffraction to study this, taking a series of snapshots of how samples respond to laser-produced shock waves that mimic the extreme conditions found in other planets. This technique works well for crystal samples but is less effective for non-crystal samples whose molecules and atoms are arranged more randomly, which limits the depth of understanding scientists can reach. In this new paper, the team used a technique called X-ray Thomson scattering that precisely reproduces previous diffraction results while also allowing them to study how elements mix in non-crystal samples at extreme conditions.

    “This research provides data on a phenomenon that is very difficult to model computationally: the ‘miscibility’ of two elements, or how they combine when mixed,” says LCLS Director Mike Dunne. “Here they see how two elements separate, like getting mayonnaise to separate back into oil and vinegar. What they learn could offer insight into a key way fusion fails, in which the inert shell of a capsule mixes in with the fusion fuel and contaminates it so that it doesn’t burn.”

    10,000 kilometers deep

    In this most recent experiment, optical laser beams launched a shock wave in a plastic sample made up of carbon and hydrogen. As the shock wave moved through the material, the researchers observed it by hitting the shocked regions with X-ray photons from LCLS that scattered both backwards and forwards off electrons in the sample.

    1
    The two sets of scattered photons revealed how hydrogen (blue) and carbon (grey) atoms separated, or demixed, in response to the extreme pressure and temperature conditions reached in the experiment. (Greg Stewart/SLAC National Accelerator Laboratory)

    “One set of scattered photons revealed the extreme temperatures and pressures reached in the sample, which mimic those found 10,000 kilometers beneath the surface of Uranus and Neptune,” says SLAC scientist and co-author Eric Galtier. “The other revealed how the hydrogen and carbon atoms separated in response to these conditions.”

    Going deeper

    The researchers hope the technique will allow them to measure the microscopic mix of materials used in fusion experiments at large, high-energy lasers such as the National Ignition Facility at DOE’s Lawrence Livermore National Laboratory (LLNL).


    National Ignition Facility at LLNL

    “We want to understand if this process could occur in inertial confinement fusion implosions with plastic ablator capsules, as it would generate fluctuations that could grow and degrade the implosion performance,” said Tilo Doeppner, LLNL physicist and co-author on the paper.

    To follow up, the team plans to recreate even more extreme conditions found deeper inside icy giants, and to study samples that contain other elements to understand what happens in other planets.

    “This technique will allow us to measure interesting processes that are otherwise difficult to recreate,” says Dominik Kraus, a scientist at Helmholtz-Zentrum Dresden-Rossendorf who led the study. “For example, we’ll be able to see how hydrogen and helium, elements found in the interior of gas giants like Jupiter and Saturn, mix and separate under these extreme conditions. It’s a new way to study the evolutionary history of planets and planetary systems, as well as supporting experiments towards potential future forms of energy from fusion.”

    LCLS is a DOE Office of Science user facility. This research was funded in part by the Office of Science.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Stanford University campus. No image credit

    Stanford University

    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 12:49 pm on April 29, 2020 Permalink | Reply
    Tags: , , LCLS- "A new machine learning method streamlines particle accelerator operations", SLAC National Accelerator Laboratory,   

    From SLAC National Accelerator Lab: “A new machine learning method streamlines particle accelerator operations” 

    From SLAC National Accelerator Lab

    April 29, 2020
    Erika K. Carlson

    It combines human knowledge and expertise with the speed and efficiency of “smart” computer algorithms.

    1

    Each year, researchers from around the world visit the Department of Energy’s SLAC National Accelerator Laboratory to conduct hundreds of experiments in chemistry, materials science, biology and energy research at the Linac Coherent Light Source (LCLS) X-ray laser [below]. LCLS creates ultrabright X-rays from high-energy beams of electrons produced in a giant linear particle accelerator.

    Experiments at LCLS run around the clock, in two 12-hour shifts per day. At the start of each shift, operators must tweak the accelerator’s performance to prepare the X-ray beam for the next experiment. Sometimes, additional tweaking is needed during a shift as well. In the past, operators have spent hundreds of hours each year on this task, called accelerator tuning.

    Now, SLAC researchers have developed a new tool, using machine learning, that may make part of the tuning process five times faster compared to previous methods. They described the method in Physical Review Letters on March 25.

    Tuning the beam

    Producing LCLS’s powerful X-ray beam starts with the preparation of a high-quality electron beam. Some of the electrons’ energy then gets converted into X-ray light inside special magnets. The properties of the electron beam, which needs to be dense and tightly focused, are a critical factor in how good the X-ray beam will be.

    “Even a small difference in the density of the electron beam can have a huge difference in the amount of X-rays you get out at the end,” says Daniel Ratner, head of SLAC’s machine learning initiative and a member of the team that developed the new technique.

    The accelerator uses a series of 24 special magnets, called quadrupole magnets, to focus the electron beam similarly to how glass lenses focus light. Traditionally, human operators carefully turned knobs to adjust individual magnets between shifts to make sure the accelerator was producing the X-ray beam needed for a particular experiment. This process took up a lot of the operators’ time – time they could spend on other important tasks that improve the beam for experiments.

    A few years ago, LCLS operators adopted a computer algorithm that automated and sped up this magnet tuning. However, it came with its own disadvantages. It aimed at improving the X-ray beam by making random adjustments to the magnets’ strengths, and then picked the ones that made the best beam. But unlike human operators, this algorithm had no prior knowledge of the accelerator’s structure and couldn’t make educated guesses in its tuning that might have ultimately led to even better results.

    This is why SLAC researchers decided to develop a new algorithm that combines machine learning – “smart” computer programs that learn how to get better over time – with knowledge about the physics of the accelerator.

    “The machine learning approach is trying to tie this all together to give operators better tools so that they can focus on other important problems,” says Joseph Duris, a SLAC scientist who led the new study.

    A better beam, faster

    3
    Accelerator operator Jane Shtalenkova gives a tour of the Accelerator Control Room during SLAC’s 2019 Community Day. (Jacqueline Orrell/SLAC National Accelerator Laboratory)

    The new approach uses a technique called a Gaussian process, which predicts the effect a particular accelerator adjustment has on the quality of the X-ray beam. It also generates uncertainties for its predictions. The algorithm then decides which adjustments to try for the biggest improvements.

    For example, it may decide to try a dramatic adjustment whose outcome is very uncertain but could lead to a big payoff. That means this new, adventurous algorithm has a better chance than the previous algorithm of making the tweaks needed to create the best possible X-ray beam.

    The SLAC researchers also used data from previous LCLS operations to teach the algorithm which magnet strengths have typically led to brighter X-rays, giving the algorithm a way of making educated guesses about the adjustments it should try. This equips the algorithm with knowledge and expertise that human operators naturally have, and that the previous algorithm lacked.

    “We can rely on that physics knowledge, that institutional knowledge, in order to improve the predictions,” Duris says.

    Insights into the magnets’ relationships to each other also improved the technique. The quadrupole magnets work in pairs, and to increase their focusing power, the strength of one magnet in a pair must be increased while the other’s is decreased.

    With the new process, tuning the quadrupole magnets has become about three to five times faster, the researchers estimate. It also tends to produce higher-intensity beams than the previously used algorithm.

    “Our ability to increase our tuning efficiency is really, really critical to being able to deliver a beam faster and with better quality to people who are coming from all over the world to run experiments,” says Jane Shtalenkova, an accelerator operator at SLAC who worked with Duris, Ratner and others to develop the new tool.

    Beyond LCLS

    The same method can be extended to tune other electron or X-ray beam properties that scientists may want to optimize for their experiments. For example, researchers could apply the technique to maximize the signal they get out of their sample after it’s hit by LCLS’s X-ray beam.

    This flexibility also makes the new algorithm useful for other facilities.

    “The nice thing about this machine learning algorithm is that you can do tech transfer relatively easily,” says Adi Hanuka, a SLAC scientist who has been testing the technique at three other accelerators: SPEAR3, the accelerator ring powering SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL); PEGASUS at the University of California, Los Angeles; and the Advanced Photon Source (APS) at DOE’s Argonne National Laboratory.

    “This tool now exists in several labs,” Hanuka says. “Hopefully, we’ll be integrating it into even more labs soon.”

    LCLS, SSRL and APS are DOE Office of Science user facilities. The project was largely funded as part of SLAC’s Laboratory Directed Research and Development Program (LDRD).

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC National Accelerator Lab


    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 4:10 pm on April 10, 2020 Permalink | Reply
    Tags: "In a first researchers use ultrafast ‘electron camera’ to learn about molecules in liquid samples", , , , , SLAC Megaelectronvolt Ultrafast Electron Diffraction Instrument: MeV-UED, SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “In a first, researchers use ultrafast ‘electron camera’ to learn about molecules in liquid samples” 

    From SLAC National Accelerator Lab

    April 9, 2020
    Ali Sundermier

    1

    This new technology could enable future insights into chemical and biological processes that occur in solution, such as vision, catalysis and photosynthesis.

    High-speed “electron cameras” can detect tiny molecular movements in a material by scattering a powerful beam of electrons off a sample. Until recently, researchers had only used this technique to study gases and solids. But some of the most important biological and chemical processes, in particular the conversion of light into energy, happen in molecules in a solution.

    Now, researchers have applied this technique, ultrafast electron diffraction, to molecules in liquid samples. They developed a method to create 100-nanometer thick liquid jets–about 1,000 times thinner than the width of a human hair–that enable them to get clear diffraction patterns from electrons. In the future, this method could allow them to explore light-driven processes such as vision, catalysis, photosynthesis and DNA damage caused by UV rays.

    The team, which included researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and the University of Nebraska-Lincoln (UNL), published their results in Structural Dynamics in March.

    “This research is a huge breakthrough in the field of ultrafast electron diffraction,” says Xijie Wang, director of the MeV-UED instrument, who co-authored the paper. “Being able to study biological and chemical systems in their natural environment is a valuable tool that opens up a new window for the future.”

    Stop-motion movies

    Liquid jets have long been used to deliver samples at X-ray lasers such as SLAC’s Linac Coherent Light Source (LCLS) [below], providing valuable information about ultrafast processes as they occur in their natural environment.

    SLAC’s ultrafast “electron camera,” MeV-UED, uses high-energy electron beams to complement the range of structural information collected at LCLS.

    3
    SLAC Megaelectronvolt Ultrafast Electron Diffraction Instrument: MeV-UED

    Here, scientists begin by exciting a sample with laser light, kicking off the processes they hope to study. Next they blast the sample with a short pulse of electrons with high energy, measured in millions of electronvolts (MeV), to look inside, generating snapshots of its shifting atomic structure that can be strung together into a stop-motion movie of the light-induced structural changes in the sample.

    Looking into the kaleidoscope

    The tiny wavelengths of these high-energy electrons allow scientists to take high-resolution snapshots, offering insight into processes such as proton transfer and hydrogen-bond breaking that are difficult to study with other methods. But applying this technique to liquid samples has proven challenging.

    “Since electrons don’t penetrate samples as easily as X-rays,” says Kathryn Ledbetter, a graduate student at the Stanford PULSE Institute who coauthored the paper, “applying this technique to liquids has been a longstanding challenge in the field.”

    If the sample is too thick, the electrons can get stuck and scatter multiple times, producing a wild mix of patterns that’s difficult to glean information from, like looking through a kaleidoscope. In this new study, the team overcame those challenges through the use of MeV electrons and a gas-accelerated thin liquid sheet jet. As the electrons break through the jet, they scatter only once, producing a clean pattern that’s much easier to reconstruct. The team also designed a chamber that housed the liquid jet and monitored the interaction between the sample and the electron beam.

    ‘Another tool in the ultrafast toolbox’

    This paper sets the stage for upcoming research that investigates questions such as what happens when hydrogen bonds break or when molecules absorb UV radiation. As a next step, SLAC researchers are upgrading the MeV-UED facility and developing a new generation of direct electron detectors that will greatly expand the scientific reach of this technique.

    “We’d like this to be another tool in the toolbox of researchers trying to learn about liquids and light-driven reactions,” says Pedro Nunes, a postdoctoral researcher at UNL who led the research. “We want to show the community that what was once believed to be far-fetched is not only possible, but capable of running smoothly enough to watch structural changes unfold in real time.”

    UED-MeV and LCLS are DOE Office of Science user facilities. The project was funded by the Office of Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC National Accelerator Lab

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 1:52 pm on April 1, 2020 Permalink | Reply
    Tags: , , , SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “The Milky Way’s satellites help reveal link between Dark Matter halos and galaxy formation” 

    From SLAC National Accelerator Lab

    March 31, 2020
    Nathan Collins

    1
    SLAC and Stanford

    Just like we orbit the sun and the moon orbits us, the Milky Way has satellite galaxies with their own satellites. Drawing from data on those galactic neighbors, a new model suggests the Milky Way should have an additional 100 or so very faint satellite galaxies awaiting discovery.

    Just as the sun has planets and the planets have moons, our galaxy has satellite galaxies, and some of those might have smaller satellite galaxies of their own. To wit, the Large Magellanic Cloud (LMC), a relatively large satellite galaxy visible from the Southern Hemisphere, is thought to have brought at least six of its own satellite galaxies with it when it first approached the Milky Way, based on recent measurements from the European Space Agency’s Gaia mission.

    Large Magellanic Cloud. Adrian Pingstone December 2003

    ESA/GAIA satellite

    Astrophysicists believe that Dark Matter is responsible for much of that structure, and now researchers at the Department of Energy’s SLAC National Accelerator Laboratory and the Dark Energy Survey have drawn on observations of faint galaxies around the Milky Way to place tighter constraints on the connection between the size and structure of galaxies and the Dark Matter halos that surround them.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    At the same time, they have found more evidence for the existence of LMC satellite galaxies and made a new prediction: If the scientists’ models are correct, the Milky Way should have an additional 150 or more very faint satellite galaxies awaiting discovery by next-generation projects such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time.

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    The new study, forthcoming in The Astrophysical Journal and available as a preprint here, is part of a larger effort to understand how Dark Matter works on scales smaller than our galaxy, said Ethan Nadler, the study’s first author and a graduate student at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and Stanford University.

    “We know some things about Dark Matter very well – how much Dark Matter is there, how does it cluster – but all of these statements are qualified by saying, yes, that is how it behaves on scales larger than the size of our local group of galaxies,” Nadler said. “And then the question is, does that work on the smallest scales we can measure?”

    Shining galaxies’ light on Dark Matter

    Astronomers have long known the Milky Way has satellite galaxies, including the Large Magellanic Cloud, which can be seen by the naked eye from the Southern Hemisphere, but the number was thought to be around just a dozen or so until around the year 2000. Since then, the number of observed satellite galaxies has risen dramatically. Thanks to the Sloan Digital Sky Survey and more recent discoveries by projects including the Dark Energy Survey (DES), the number of known satellite galaxies has climbed to about 60.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    Such discoveries are always exciting, but what’s perhaps most exciting is what the data could tell us about the cosmos. “For the first time, we can look for these satellite galaxies across about three-quarters of the sky, and that’s really important to several different ways of learning about Dark Matter and galaxy formation,” said Risa Wechsler, director of KIPAC. Last year, for example, Wechsler, Nadler and colleagues used data on satellite galaxies in conjunction with computer simulations to place much tighter limits on Dark Matter’s interactions with ordinary matter.

    Now, Wechsler, Nadler and the DES team are using data from a comprehensive search over most of the sky to ask different questions, including how much Dark Matter it takes to form a galaxy, how many satellite galaxies we should expect to find around the Milky Way and whether galaxies can bring their own satellites into orbit around our own – a key prediction of the most popular model of Dark Matter.

    Hints of galactic hierarchy

    The answer to that last question appears to be a resounding “yes.”


    A slow starting simulation of the formation of Dark Matter structures from the early universe until today. Gravity makes Dark Matter clump into dense halos, indicated by bright patches, where galaxies form. At about 18 seconds into this simulation, a halo like the one that hosts the Milky Way begins to form near the center top of the frame. Shortly afterward, a smaller halo begins to take shape at the top center of the screen. This halo falls into the first, larger halo by about 35 seconds, mimicking the Large Magellanic Cloud’s fall into the Milky Way. SLAC and Stanford researchers, working with collaborators from the Dark Energy Survey, have used simulations like these to better understand the connection between Dark Matter and galaxy formation. (Ralf Kaehler/SLAC National Accelerator Laboratory)

    The possibility of detecting a hierarchy of satellite galaxies first arose some years back when DES detected more satellite galaxies in the vicinity of the Large Magellanic Cloud than they would have expected if those satellites were randomly distributed throughout the sky. Those observations are particularly interesting, Nadler said, in light of the Gaia measurements, which indicated that six of these satellite galaxies fell into the Milky Way with the LMC.

    To study the LMC’s satellites more thoroughly, Nadler and team analyzed computer simulations of millions of possible universes. Those simulations, originally run by Yao-Yuan Mao, a former graduate student of Wechsler’s who is now at Rutgers University, model the formation of Dark Matter structure that permeates the Milky Way, including details such as smaller Dark Matter clumps within the Milky Way that are expected to host satellite galaxies. To connect Dark Matter to galaxy formation, the researchers used a flexible model that allows them to account for uncertainties in the current understanding of galaxy formation, including the relationship between galaxies’ brightness and the mass of Dark Matter clumps within which they form.

    An effort led by the others in the DES team, including former KIPAC students Alex Drlica-Wagner, a Wilson Fellow at Fermilab and an assistant professor of astronomy and astrophysics at the University of Chicago, and Keith Bechtol, an assistant professor of physics at the University of Wisconsin-Madison, and their collaborators produced the crucial final step: a model of which satellite galaxies are most likely to be seen by current surveys, given where they are in the sky as well as their brightness, size and distance.

    Those components in hand, the team ran their model with a wide range of parameters and searched for simulations in which LMC-like objects fell into the gravitational pull of a Milky Way-like galaxy. By comparing those cases with galactic observations, they could infer a range of astrophysical parameters, including how many satellite galaxies should have tagged along with the LMC. The results, Nadler said, were consistent with Gaia observations: Six satellite galaxies should currently be detected in the vicinity of the LMC, moving with roughly the right velocities and in roughly the same places as astronomers had previously observed. The simulations also suggested that the LMC first approached the Milky Way about 2.2 billion years ago, consistent with high-precision measurements of the motion of the LMC from the Hubble Space Telescope.

    Galaxies yet unseen

    In addition to the LMC findings, the team also put limits on the connection between Dark Matter halos and galaxy structure. For example, in simulations that most closely matched the history of the Milky Way and the LMC, the smallest galaxies astronomers could currently observe should have stars with a combined mass of around a hundred suns, and about a million times as much Dark Matter. According to an extrapolation of the model, the faintest galaxies that could ever be observed could form in halos up to a hundred times less massive than that.

    And there could be more discoveries to come: If the simulations are correct, Nadler said, there are around 100 more satellite galaxies – more than double the number already discovered – hovering around the Milky Way. The discovery of those galaxies would help confirm the researchers’ model of the links between Dark Matter and galaxy formation, he said, and likely place tighter constraints on the nature of dark matter itself.

    The research was a collaborative effort within the Dark Energy Survey, led by the Milky Way Working Group, with substantial contributions from junior members including Sidney Mau, an undergraduate at the University of Chicago, and Mitch McNanna, a graduate student at UW-Madison. The research was supported by a National Science Foundation Graduate Fellowship, by the Department of Energy’s Office of Science through SLAC, and by Stanford University.

    _____________________________________________

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    _____________________________________________

    Dark Matter Background
    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 3:07 pm on March 7, 2020 Permalink | Reply
    Tags: "Radar and ice could help detect an elusive subatomic particle", , Neutrino cascades, , , , SLAC National Accelerator Laboratory, U Wisconsin ICECUBE neutrino detector at the South Pole   

    From Ohio State University: “Radar and ice could help detect an elusive subatomic particle” 

    From Ohio State University

    Mar 06, 2020
    Laura Arenschield
    Ohio State News
    arenschield.2@osu.edu
    614-292-9475

    Scientists create new experiment to find neutrinos.

    1
    An artist’s rendition of neutrino activity. Image via Shutterstock.

    2
    Credit: CC0 Public Domain

    One of the greatest mysteries in astrophysics these days is a tiny subatomic particle called a neutrino, so small that it passes through matter – the atmosphere, our bodies, the very Earth – without detection.

    Physicists around the world have for decades been trying to detect neutrinos, which are constantly bombarding our planet and which are lighter than any other known subatomic particles. Scientists hope that by capturing neutrinos, they can study them and, hopefully, understand where they come from and what they do.

    But existing attempts are often expensive, and miss an entire class of high-energy neutrinos from some of the furthest reaches of space.

    A new study published today in the journal Physical Review Letters shows, for the first time, an experiment that could detect that class of neutrinos using radar echoes.

    “These neutrinos are fundamental particles that we don’t understand,” said Steven Prohira, lead author of the study and a researcher at The Ohio State University Center for Cosmology and Astroparticle Physics. “And ultra-high-energy neutrinos can tell us about huge parts of the universe that we can’t really access in any other way. We need to figure out how to study them, and that’s what this experiment tries to do.”

    The study relies on a phenomenon known as a cascade. Scientists think neutrinos move through the Earth at almost the speed of light – billions of them are passing through you now, as you read this.

    Higher-energy neutrinos are more likely to collide with atoms. Those collisions cause a cascade of charged particles – “like a giant spray,” Prohira said. And the cascades are important: If researchers can detect the cascade, they can detect a neutrino. Ultra-high-energy neutrinos are so rare that scientists so far have not been able to detect them.

    Scientists have figured out that the best places to detect neutrinos are in large sheets of remote ice: The longest-running and most successful neutrino experiments are in Antarctica.

    U Wisconsin IceCube experiment at the South Pole


    U Wisconsin ICECUBE neutrino detector at the South Pole

    But those experiments so far have not been able to detect neutrinos with higher energies.

    That’s where Prohira’s research comes in: His team showed, in a laboratory, that it is possible to detect the cascade that happens when a neutrino hits an atom by bouncing radio waves off of the trail of charged particles left by the cascade.

    For this study, they went to the SLAC National Accelerator Laboratory in California, set up a 4-meter-long plastic target to simulate ice in Antarctica, and blasted the target with a billion electrons packed into a tiny bunch to simulate neutrinos.

    SLAC National Accelerator Lab

    (The total energy of that electron bunch, Prohira said, is similar to the total energy of a high-energy neutrino.) Then they transmitted radio waves at the plastic target to see if the waves would indeed detect a cascade. They did.

    Prohira said the next step is to take the experiment to Antarctica, to see if it can detect neutrinos over a wide volume of remote ice there.

    Radio waves are the cheapest known technology for detecting neutrinos, he said, “which is part of why this is so exciting.” Radio waves have been used in the search for the highest-energy neutrinos for about 20 years, Prohira said. This radar technique could be one more tool in the radio wave toolbox for scientists hoping to study ultra-high-energy neutrinos.

    And having a greater understanding of neutrinos could help us understand more about our galaxy and the rest of the universe.

    “Neutrinos are the only known particles that travel in straight lines — they go right through things,” he said. “There aren’t any other particles that do that: Light gets blocked. Other charged particles get deflected in magnetic fields.”

    When a neutrino is created somewhere in the universe, it travels in a straight line, unaltered.

    “It points straight back to the thing that produced it,” Prohira said. “So, it’s a way for us to identify and learn more about these extremely energetic processes in the universe.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Ohio State University (OSU, commonly referred to as Ohio State) is a public research university in Columbus, Ohio. Founded in 1870 as a land-grant university and the ninth university in Ohio with the Morrill Act of 1862,[4] the university was originally known as the Ohio Agricultural and Mechanical College. The college originally focused on various agricultural and mechanical disciplines but it developed into a comprehensive university under the direction of then-Governor (later, U.S. President) Rutherford B. Hayes, and in 1878 the Ohio General Assembly passed a law changing the name to “The Ohio State University”.[5] The main campus in Columbus, Ohio, has since grown into the third-largest university campus in the United States.[6] The university also operates regional campuses in Lima, Mansfield, Marion, Newark, and Wooster.

    The university has an extensive student life program, with over 1,000 student organizations; intercollegiate, club and recreational sports programs; student media organizations and publications, fraternities and sororities; and three student governments. Ohio State athletic teams compete in Division I of the NCAA and are known as the Ohio State Buckeyes. As of the 2016 Summer Olympics, athletes from Ohio State have won 104 Olympic medals (46 gold, 35 silver, and 23 bronze). The university is a member of the Big Ten Conference for the majority of sports.

     
  • richardmitnick 10:59 am on February 27, 2020 Permalink | Reply
    Tags: "A better way to build diamonds", SLAC National Accelerator Laboratory, , With the right amount of pressure and surprisingly little heat a substance found in fossil fuels can transform into pure diamond.   

    From Stanford University and SLAC: “A better way to build diamonds” 

    From SLAC National Accelerator Lab

    and

    Stanford University Name
    Stanford University

    February 25, 2020
    Josie Garthwaite

    With the right amount of pressure and surprisingly little heat, a substance found in fossil fuels can transform into pure diamond.

    It sounds like alchemy: take a clump of white dust, squeeze it in a diamond-studded pressure chamber, then blast it with a laser. Open the chamber and find a new microscopic speck of pure diamond inside.

    A new study from Stanford University and SLAC National Accelerator Laboratory reveals how, with careful tuning of heat and pressure, that recipe can produce diamonds from a type of hydrogen and carbon molecule found in crude oil and natural gas.

    “What’s exciting about this paper is it shows a way of cheating the thermodynamics of what’s typically required for diamond formation,” said Stanford geologist Rodney Ewing, a co-author on the paper, published Feb. 21 in the journal Science Advances.

    1
    A sample of diamond crystals synthesized from triamantane, a type of diamondoid. (Image credit: Sulgiye Park.)

    Scientists have synthesized diamonds from other materials for more than 60 years, but the transformation typically requires inordinate amounts of energy, time or the addition of a catalyst – often a metal – that tends to diminish the quality of the final product. “We wanted to see just a clean system, in which a single substance transforms into pure diamond – without a catalyst,” said the study’s lead author, Sulgiye Park, a postdoctoral research fellow at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

    Understanding the mechanisms for this transformation will be important for applications beyond jewelry. Diamond’s physical properties – extreme hardness, optical transparency, chemical stability, high thermal conductivity – make it a valuable material for medicine, industry, quantum computing technologies and biological sensing.

    “If you can make even small amounts of this pure diamond, then you can dope it in controlled ways for specific applications,” said study senior author Yu Lin, a staff scientist in the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC National Accelerator Laboratory.

    A natural recipe

    3
    Lead study author Sulgiye Park holds a sample of the diamondoid triamantane and a model showing its structure, which features three units or “cages” composed of hydrogen and carbon atoms bonded together. (Image credit: Andrew Brodhead)

    Natural diamonds crystallize from carbon hundreds of miles beneath Earth’s surface, where temperatures reach thousands of degrees Fahrenheit. Most natural diamonds unearthed to date rocketed upward in volcanic eruptions millions of years ago, carrying ancient minerals from Earth’s deep interior with them.

    As a result, diamonds can provide insight into the conditions and materials that exist in the planet’s interior. “Diamonds are vessels for bringing back samples from the deepest parts of the Earth,” said Stanford mineral physicist Wendy Mao, who leads the lab where Park performed most of the study’s experiments.

    To synthesize diamonds, the research team began with three types of powder refined from tankers full of petroleum. “It’s a tiny amount,” said Mao. “We use a needle to pick up a little bit to get it under a microscope for our experiments.”

    At a glance, the odorless, slightly sticky powders resemble rock salt. But a trained eye peering through a powerful microscope can distinguish atoms arranged in the same spatial pattern as the atoms that make up diamond crystal. It’s as if the intricate lattice of diamond had been chopped up into smaller units composed of one, two or three cages.

    Unlike diamond, which is pure carbon, the powders – known as diamondoids – also contain hydrogen. “Starting with these building blocks,” Mao said, “you can make diamond more quickly and easily, and you can also learn about the process in a more complete, thoughtful way than if you just mimic the high pressure and high temperature found in the part of the Earth where diamond forms naturally.”

    Diamondoids under pressure

    3
    After squeezing diamondoid samples and blasting them with a laser, the researchers used a second, cooler laser beam to help characterize the resulting diamond. (Image credit: Andrew Brodhead)

    The researchers loaded the diamondoid samples into a plum-sized pressure chamber called a diamond anvil cell, which presses the powder between two polished diamonds. With just a simple hand turn of a screw, the device can create the kind of pressure you might find at the center of the Earth.

    Next, they heated the samples with a laser, examined the results with a battery of tests, and ran computer models to help explain how the transformation had unfolded. “A fundamental question we tried to answer is whether the structure or number of cages affects how diamondoids transform into diamond,” Lin said. They found that the three-cage diamondoid, called triamantane, can reorganize itself into diamond with surprisingly little energy.

    At 900 Kelvin – which is roughly 1160 degrees Fahrenheit, or the temperature of red-hot lava – and 20 gigapascals, a pressure hundreds of thousands of times greater than Earth’s atmosphere, triamantane’s carbon atoms snap into alignment and its hydrogen scatters or falls away.

    The transformation unfolds in the slimmest fractions of a second. It’s also direct: the atoms do not pass through another form of carbon, such as graphite, on their way to making diamond.

    The minute sample size inside a diamond anvil cell makes this approach impractical for synthesizing much more than the specks of diamond that the Stanford team produced in the lab, Mao said. “But now we know a little bit more about the keys to making pure diamonds.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    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/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 11:32 pm on February 12, 2020 Permalink | Reply
    Tags: , , Biophysical chemistry, Chromophores, Macromolecular crystallography, , Photoisomerization, , , SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “Researchers show how electric fields affect a molecular twist within light-sensitive proteins” 

    From SLAC National Accelerator Lab

    February 12, 2020
    By Ali Sundermier

    A better understanding of this phenomenon, which is crucial to many processes that occur in biological systems and materials, could enable researchers to develop light-sensitive proteins for areas such as biological imaging and optogenetics.

    A team of scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University has gained insight into how electric fields affect the way energy from light drives molecular motion and transformation in a protein commonly used in biological imaging. A better understanding of this phenomenon, which is crucial to many processes that occur in biological systems and materials, could enable researchers to finely tune a system’s properties to harness these effects, for instance using light to control neurons in the brain. Their findings were published in Science in January.

    Twist and shout

    Human vision, photosynthesis and other natural processes harvest light with proteins that contain molecules known as chromophores, many of which twist when light hits them. The hallmark of this twisting motion, called photoisomerization, is that part of the molecule rotates around a particular chemical bond.

    2
    When light hits certain chromophores in proteins, it causes them to twist and change shape. This atomic reconfiguration, known as photoisomerization, changes the molecule’s chemical and physical properties. The hallmark of this process is a rotation that occurs around a chemical bond in the molecule. New research shows that the electric fields within a protein play a large role in determining which bond this rotation occurs around. (Chi-Yun Lin/Stanford University)

    “Something about the protein environment is steering this very specific and important process,” says Steven Boxer, a biophysical chemist and Stanford professor who oversaw the research. “One possibility is that the distribution of atoms in the molecular space blocks or allows rotation about each chemical bond, known as the steric effect. An alternative has to do with the idea that when molecules with double bonds are excited, there is a separation of charge, and so the surrounding electric fields might favor the rotation of one bond over another. This is called the electrostatic effect.”

    A different tune

    To find out more about this process, the researchers looked at green fluorescent protein, a protein frequently used in biological imaging whose chromophore can respond to light in a number of ways that are sensitive to its local environment within the protein, producing fluorescent light of various colors and intensities.

    Stanford graduate students Matt Romei and Chi-Yun Lin, who led the study, tuned the electronic properties of the chromophore within the protein by introducing chemical groups that systematically added or subtracted electrons from the chromophore to engineer an electric field effect. Then they measured how this affected the chromophore’s twisting motion.

    With the help of coauthor Irimpan Mathews, a scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), the researchers used an X-ray technique called macromolecular crystallography at SSRL beamlines 7-1, 12-2 and 14-1 to map the structures of these tuned proteins to show that these changes had little effect on the atomic structure of the chromophore and surrounding protein.

    SLAC/SSRL

    Then, using a combination of techniques, they were able to measure how changes to the chromophore’s electron distribution affected where rotation occurred when it was hit by light.

    “Until now, most of the research on photoisomerization in this particular protein has been either theoretical or focused on the steric effect,” Romei says. “This research is one of the first to investigate the phenomenon experimentally and show the importance of the electrostatic effect. Once we plotted the data, we saw these really nice trends that suggest that tuning the chromophore’s electronic properties has a huge impact on its bond isomerization properties.”

    Honing tools

    These results also suggest ways to design light-sensitive proteins by manipulating the environment around the chromophore. Lin adds that this same experimental approach could be used to study and control the electrostatic effect in many other systems.

    “We’re trying to figure out the principle that controls this process,” Lin says. “Using what we learn, we hope to apply these concepts to develop better tools in fields such as optogenetics, where you can selectively manipulate nerves to lead to certain functions in the brain.”

    Boxer adds that the idea that the organized electric fields within proteins are important for many biological functions is an emerging concept that could be of interest to a broad audience.

    “Much of the work in our lab focuses on developing methods to measure these fields and connect them with function such as enzymatic catalysis,” he says, “and we now see that photoisomerization fits into this framework.”

    This work was funded in part by the National Institutes of Health (NIH). SSRL is a DOE Office of Science user facility. The SSRL Structural Molecular Biology Program is supported by the NIH and the DOE Office of Biological and Environmental Research. Part of this work was performed at the Stanford Nano Shared Facilities and supported by the National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 12:14 pm on February 12, 2020 Permalink | Reply
    Tags: Atom or noise?, , , , , , SLAC National Accelerator Laboratory, Stanford’s Department of Bioengineering   

    From SLAC National Accelerator Lab: “Atom or noise? New method helps cryo-EM researchers tell the difference” 

    From SLAC National Accelerator Lab

    February 11, 2020
    Nathan Collins

    Cryogenic electron microscopy can in principle make out individual atoms in a molecule, but distinguishing the crisp from the blurry parts of an image can be a challenge. A new mathematical method may help.

    Cryogenic electron microscopy, or cryo-EM, has reached the point where researchers could in principle image individual atoms in a 3D reconstruction of a molecule – but just because they could see those details doesn’t always mean they do. Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have proposed a new way to quantify how accurate such reconstructions are and, in the process, how confident they can be in their molecular interpretations. The study was published February 10 in Nature Methods.

    Cryo-EM works by freezing biological molecules which can contain thousands of atoms so they can be imaged under an electron microscope. By aligning and combining many two-dimensional images, researchers can compute three-dimensional maps of an entire molecule, and this technique has been used to study everything from battery failure to the way viruses invade cells. However, an issue that has been hard to solve is how to accurately assess the true level of detail or resolution at every point in such maps and in turn determine what atomic features are truly visible or not.

    1
    A cryo-EM map of the molecule apoferritin (left) and a detail of the map showing the atomic model researchers use to construct Q-scores. (Image courtesy Greg Pintilie)

    Wah Chiu, a professor at SLAC and Stanford, Grigore Pintilie, a computational scientist in Chiu’s group, and colleagues devised the new measures, known as Q-scores, to address that issue. To compute Q-scores, scientists start by building and adjusting an atomic model until it best matches the corresponding cryo-EM derived 3D map. Then, they compare the map to an idealized version in which each atom is well-resolved, revealing to what degree the map truly resolves the atoms in the atomic model.

    The researchers validated their approach on large molecules, including a protein called apoferritin that they studied in the Stanford-SLAC Cryo-EM Facilities. Kaiming Zhang, another research scientist in Chiu’s group, produced 3D maps close to the highest resolution reached to date – up to 1.75 angstrom, less than a fifth of a nanometer. Using such maps, they showed how Q-scores varied in predictable ways based on overall resolution and on which parts of a molecule they were studying. Pintilie and Chiu say they hope Q-scores will help biologists and others using cryo-EM better understand and interpret the 3D maps and resulting atomic models.

    The study was performed in collaboration with researchers from Stanford’s Department of Bioengineering. Molecular graphics and analysis were performed using the University of California, San Francisco’s Chimera software package. The project was funded by the National Institutes of Health.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 9:54 am on February 6, 2020 Permalink | Reply
    Tags: "Could the next generation of particle accelerators come out of the 3D printer?", , , , Consortium on the Properties of Additive-Manufactured Copper, , , , SLAC National Accelerator Laboratory   

    From SLAC National Accelerator Lab: “Could the next generation of particle accelerators come out of the 3D printer?” 

    From SLAC National Accelerator Lab

    February 5, 2020
    Jennifer Huber

    SLAC scientists and collaborators are developing 3D copper printing techniques to build accelerator components.

    Imagine being able to manufacture complex devices whenever you want and wherever you are. It would create unforeseen possibilities even in the most remote locations, such as building spare parts or new components on board a spacecraft. 3D printing, or additive manufacturing, could be a way of doing just that. All you would need is the materials the device will be made of, a printer and a computer that controls the process.

    Diana Gamzina, a staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory; Timothy Horn, an assistant professor of mechanical and aerospace engineering at North Carolina State University; and researchers at RadiaBeam Technologies dream of developing the technique to print particle accelerators and vacuum electronic devices for applications in medical imaging and treatment, the electrical grid, satellite communications, defense systems and more.

    1
    Examples of 3D-printed copper components that could be used in a particle accelerator: X-band klystron output cavity with micro-cooling channels (at left) and a set of coupled accelerator cavities. (Christopher Ledford/North Carolina State University)

    In fact, the researchers are closer to making this a reality than you might think.

    “We’re trying to print a particle accelerator, which is really ambitious,” Gamzina said. “We’ve been developing the process over the past few years, and we can already print particle accelerator components today. The whole point of 3D printing is to make stuff no matter where you are without a lot of infrastructure. So you can print your particle accelerator on a naval ship, in a small university lab or somewhere very remote.”

    3D printing can be done with liquids and powders of numerous materials, but there aren’t any well-established processes for 3D printing ultra-high-purity copper and its alloys – the materials Gamzina, Horn and their colleagues want to use. Their research focuses on developing the method.

    Indispensable copper

    Accelerators boost the energy of particle beams, and vacuum electronic devices are used in amplifiers and generators. Both rely on components that can be easily shaped and conduct heat and electricity extremely well. Copper has all of these qualities and is therefore widely used.

    Traditionally, each copper component is machined individually and bonded with others using heat to form complex geometries. This manufacturing technique is incredibly common, but it has its disadvantages.

    “Brazing together multiple parts and components takes a great deal of time, precision and care,” Horn said. “And any time you have a joint between two materials, you add a potential failure point. So, there is a need to reduce or eliminate those assembly processes.”

    Potential of 3D copper printing

    3D printing of copper components could offer a solution.

    It works by layering thin sheets of materials on top of one another and slowly building up specific shapes and objects. In Gamzina’s and Horn’s work, the material used is extremely pure copper powder.

    The process starts with a 3D design, or “construction manual,” for the object. Controlled by a computer, the printer spreads a few-micron-thick layer of copper powder on a platform. It then moves the platform about 50 microns – half the thickness of a human hair – and spreads a second copper layer on top of the first, heats it with an electron beam to about 2,000 degrees Fahrenheit and welds it with the first layer. This process repeats over and over until the entire object has been built.


    3D printing of copper devices
    3D printing of a layer of a device known as a traveling wave tube using copper powder. (Christopher Ledford/North Carolina State University)

    The amazing part: no specific tooling, fixtures or molds are needed for the procedure. As a result, 3D printing eliminates design constraints inherent in traditional fabrication processes and allows the construction of objects that are uniquely complex.

    “The shape doesn’t really matter for 3D printing,” said SLAC staff scientist Chris Nantista, who designs and tests 3D-printed samples for Gamzina and Horn. “You just program it in, start your system and it can build up almost anything you want. It opens up a new space of potential shapes.”

    The team took advantage of that, for example, when building part of a klystron – a specialized vacuum tube that amplifies radiofrequency signals – with internal cooling channels at NCSU. Building it in one piece improved the device’s heat transfer and performance.

    Compared to traditional manufacturing, 3D printing is also less time consuming and could translate into cost savings of up to 70%, Gamzina said.

    A challenging technique

    But printing copper devices has its own challenges, as Horn, who began developing the technique with collaborators from RadiaBeam years ago, knows. One issue is finding the right balance between the thermal and electrical properties and strengths of the printed objects. But the biggest hurdle for manufacturing accelerators and vacuum electronics, though, is that these high-vacuum devices require extremely high quality and pure materials to avoid part failures, such as cracking or vacuum leaks.

    The research team tackled these challenges by first improving the material’s surface quality, using finer copper powder and varying the way they fused layers together. However, using finer copper powder led to the next challenge. It allowed more oxygen to attach to the copper powder, increasing the oxide in each layer and making the printed objects less pure.

    So, Gamzina and Horn had to find a way to reduce the oxygen content in their copper powders. The method they came up with, which they recently reported in Applied Sciences, relies on hydrogen gas to bind oxygen into water vapor and drive it out of the powder.

    Using this method is somewhat surprising, Horn said. In a traditionally manufactured copper object, the formation of water vapor would create high-pressure steam bubbles inside the material, and the material would blister and fail. In the additive process, on the other hand, the water vapor escapes layer by layer, which releases the water vapor more effectively.

    Although the technique has shown great promise, the scientists still have a ways to go to reduce the oxygen content enough to print an actual particle accelerator. But they have already succeeded in printing a few components, such as the klystron output cavity with internal cooling channels and a string of coupled cavities that could be used for particle acceleration.

    Planning to team up with industry partners

    The next phase of the project will be driven by the newly-formed Consortium on the Properties of Additive-Manufactured Copper, which is led by Horn. The consortium currently has four active industry members – Siemens, GE Additive, RadiaBeam and Calabazas Creek Research – with more on the way.

    “This would be a nice example of collaboration between an academic institution, a national lab and small and large businesses,” Gamzina said. “It would allow us to figure out this problem together. Our work has already allowed us to go from ‘just imagine, this is crazy’ to ‘we can do it’ in less than two years.”

    This work was primarily funded by the Naval Sea Systems Command, as a Small Business Technology Transfer Program with Radiabeam, SLAC, and NCSU. Other SLAC contributors include Chris Pearson, Andy Nguyen, Arianna Gleason, Apurva Mehta, Kevin Stone, Chris Tassone and Johanna Weker. Additional contributions came from Christopher Ledford and Christopher Rock at NCSU and Pedro Frigola, Paul Carriere, Alexander Laurich, James Penney and Matt Heintz at RadiaBeam.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    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.

    SSRL and LCLS are DOE Office of Science user facilities.

     
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