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  • richardmitnick 1:29 pm on September 17, 2020 Permalink | Reply
    Tags: "Stanford researchers devise way to see through clouds and fog", A highly efficient algorithm that can reconstruct three-dimensional hidden scenes based on the movement of individual particles of light or photons., , Laser Technology, , ,   

    From Stanford University: “Stanford researchers devise way to see through clouds and fog” 

    Stanford University Name
    From Stanford University

    September 9, 2020
    Taylor Kubota
    (650) 724-7707
    tkubota@stanford.edu

    Like a comic book come to life, researchers at Stanford University have developed a kind of X-ray vision – only without the X-rays. Working with hardware similar to what enables autonomous cars to “see” the world around them, the researchers enhanced their system with a highly efficient algorithm that can reconstruct three-dimensional hidden scenes based on the movement of individual particles of light, or photons. In tests, detailed in a paper published Sept. 9 in Nature Communications, their system successfully reconstructed shapes obscured by 1-inch-thick foam. To the human eye, it’s like seeing through walls.

    Imaging through scattering media
    1
    Schematic of 3D Imaging through scattering media. a A pulsed laser and time resolved single-photon detector raster-scan the surface of the scattering medium. b Light diffuses through the medium, is back-reflected by the hidden object, and diffuses back through the medium to the detector. c Returning photons from the hidden object are captured by the detector over time, with earlier arriving photons being gated out (dashed line). SG, scanning galvanometer; BS, beam splitter; OL, objective lens; SPAD, single-photon avalanche diode; TCSPC, time-correlated single-photon counter.


    Abstract
    Optical imaging techniques, such as light detection and ranging (LiDAR), are essential tools in remote sensing, robotic vision, and autonomous driving. However, the presence of scattering places fundamental limits on our ability to image through fog, rain, dust, or the atmosphere. Conventional approaches for imaging through scattering media operate at microscopic scales or require a priori knowledge of the target location for 3D imaging. We introduce a technique that co-designs single-photon avalanche diodes, ultra-fast pulsed lasers, and a new inverse method to capture 3D shape through scattering media. We demonstrate acquisition of shape and position for objects hidden behind a thick diffuser (≈6 transport mean free paths) at macroscopic scales. Our technique, confocal diffuse tomography, may be of considerable value to the aforementioned applications.

    “A lot of imaging techniques make images look a little bit better, a little bit less noisy, but this is really something where we make the invisible visible,” said Gordon Wetzstein, assistant professor of electrical engineering at Stanford and senior author of the paper. “This is really pushing the frontier of what may be possible with any kind of sensing system. It’s like superhuman vision.”

    This technique complements other vision systems that can see through barriers on the microscopic scale – for applications in medicine – because it’s more focused on large-scale situations, such as navigating self-driving cars in fog or heavy rain and satellite imaging of the surface of Earth and other planets through hazy atmosphere.

    Supersight from scattered light

    In order to see through environments that scatter light every-which-way, the system pairs a laser with a super-sensitive photon detector that records every bit of laser light that hits it. As the laser scans an obstruction like a wall of foam, an occasional photon will manage to pass through the foam, hit the objects hidden behind it and pass back through the foam to reach the detector. The algorithm-supported software then uses those few photons – and information about where and when they hit the detector – to reconstruct the hidden objects in 3D.

    4
    The laser scanning process in action. Single photons that travel through the foam, bounce off the “S,” and back through the foam to the detector provide information for the algorithm’s reconstruction of the hidden object. (Image credit: Stanford Computational Imaging Lab)

    This is not the first system with the ability to reveal hidden objects through scattering environments, but it circumvents limitations associated with other techniques. For example, some require knowledge about how far away the object of interest is. It is also common that these systems only use information from ballistic photons, which are photons that travel to and from the hidden object through the scattering field but without actually scattering along the way.

    “We were interested in being able to image through scattering media without these assumptions and to collect all the photons that have been scattered to reconstruct the image,” said David Lindell, a graduate student in electrical engineering and lead author of the paper. “This makes our system especially useful for large-scale applications, where there would be very few ballistic photons.”

    In order to make their algorithm amenable to the complexities of scattering, the researchers had to closely co-design their hardware and software, although the hardware components they used are only slightly more advanced than what is currently found in autonomous cars. Depending on the brightness of the hidden objects, scanning in their tests took anywhere from one minute to one hour, but the algorithm reconstructed the obscured scene in real-time and could be run on a laptop.

    “You couldn’t see through the foam with your own eyes, and even just looking at the photon measurements from the detector, you really don’t see anything,” said Lindell. “But, with just a handful of photons, the reconstruction algorithm can expose these objects – and you can see not only what they look like, but where they are in 3D space.”

    Space and fog

    5
    A three-dimensional reconstruction of the reflective letter “S,” as seen through the 1-inch-thick foam. (Image credit: Stanford Computational Imaging Lab)

    Someday, a descendant of this system could be sent through space to other planets and moons to help see through icy clouds to deeper layers and surfaces. In the nearer term, the researchers would like to experiment with different scattering environments to simulate other circumstances where this technology could be useful.

    “We’re excited to push this further with other types of scattering geometries,” said Lindell. “So, not just objects hidden behind a thick slab of material but objects that are embedded in densely scattering material, which would be like seeing an object that’s surrounded by fog.”

    Lindell and Wetzstein are also enthusiastic about how this work represents a deeply interdisciplinary intersection of science and engineering.

    “These sensing systems are devices with lasers, detectors and advanced algorithms, which puts them in an interdisciplinary research area between hardware and physics and applied math,” said Wetzstein. “All of those are critical, core fields in this work and that’s what’s the most exciting for me.”

    See the full article here .


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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 9:05 am on September 14, 2020 Permalink | Reply
    Tags: "A cool first for Harvard", , , Laser Technology,   

    From Harvard Gazette: “A cool first for Harvard” 

    Harvard University

    From Harvard Gazette

    September 11, 2020
    Juan Siliezar

    1
    Working with lasers in the Doyle Lab. Credit: Kris Snibbe/Harvard file photo.

    By slowing polyatomic molecule, scientists open new paths of quantum study.

    After firing the lasers and bombarding the ultracold molecule with light, the scientists gathered around the camera to check the results. By seeing how far the molecule expanded they would know almost instantly whether they were on the right track to chart new paths in quantum science by being the first to cool — aka, slow down — a particularly complex, six-atom molecule using nothing but light.

    “When we started out on the project we were optimistic but were not sure that we would see something that would show a very dramatic effect,” said Debayan Mitra, a postdoctoral researcher in Harvard’s Doyle Research Group. “We thought that we would need more evidence to prove that we were actually cooling the molecule, but then when we saw the signal, it was like, ‘Yeah, nobody will doubt that.’ It was big and it was right there.”

    The study led by Mitra and graduate student Nathaniel B. Vilas is the focus of a new paper published in Science. In it, the group describes using a novel method combining cryogenic technology and direct laser light to cool the nonlinear polyatomic molecule calcium monomethoxide (CaOCH3) to just above absolute zero.

    The scientists believe their experiment marks the first time such a large complex molecule has been cooled using laser light, and say it opens new avenues of study in quantum simulation and computation, particle physics, and quantum chemistry.

    “These kinds of molecules have structure that is ubiquitous in chemical and biological systems,” said John M. Doyle, the Henry B. Silsbee Professor of Physics and senior author on the paper. “Controlling perfectly their quantum states is basic research that could shed light on fundamental quantum processes in these building blocks of nature.”

    2
    Inside the lab of John Doyle (pictured), Harvard researchers were the first to cool a polyatomic molecule using light. Credit: Kris Snibbe/Harvard file photo.

    The use of lasers to control and atoms and molecules — the eventual building blocks of quantum computers — has been practiced since the 1960s and has since revolutionized atomic, molecular, and optical physics.

    The technique essentially works by firing a laser at the atoms and molecules, causing them to absorb the photons from the light and recoil in the opposite direction. This eventually slows them down and even stops them in their tracks. When this happens, quantum mechanics becomes the dominant way to describe and study their motions.

    “The idea is that on one end of the spectrum there are atoms that have very few quantum states,” Doyle said. Because of this, these atoms are easy to control with light, since they often remain in the same quantum state after absorbing and emitting light, he said. “With molecules, they have motion that does not occur in atoms — vibrations and rotations. When the molecule absorbs and emits light this process can sometimes make the molecule spin around or vibrate internally. When this happens, it is now in a different quantum state and absorbing and emitting light no longer works [to cool it]. We have to ‘calm the molecule down,’ get rid of its extra vibration before it can interact with the light the way we want.”

    Scientists — including those from the Doyle Group which is part of the Harvard Department of Physics and a member of the Harvard-MIT Center for Ultracold Atoms — have been able to cool a number of molecules using light, including diatomic and triatomic molecules, which each have two or three atoms.

    Polyatomic molecules, on the other hand, are much more complex and have proven much harder to manipulate because of all the vibrations and rotations.

    Scientists — including those from the Doyle Group which is part of the Harvard Department of Physics and a member of the Harvard-MIT Center for Ultracold Atoms — have been able to cool a number of molecules using light, including diatomic and triatomic molecules, which each have two or three atoms.

    Polyatomic molecules, on the other hand, are much more complex and have proven much harder to manipulate because of all the vibrations and rotations.

    To get around this, the group used a method they pioneered to cool diatomic and triatomic molecules. Researchers set up a sealed cryogenic chamber where they cooled helium to below four Kelvin (nearly 450 degrees below zero Fahrenheit). This chamber essentially acts as a refrigerator, in which the scientists created the molecule CaOCH3. Right off the bat, it began moving at a much slower velocity than it would normally, making it ideal for further cooling.

    Next came the lasers. They turned on two beams of light on the molecule, coming from opposing directions. The counterpropagating lasers prompted a reaction known as Sisyphus cooling. The reaction takes its name from the myth of Sisyphus, a Greek king who angered Zeus and was doomed to roll a giant boulder up a hill for eternity, only for it to roll back down when he nears the top.

    Essentially the same thing happens here with the molecule, Mitra said. When two identical laser beams are firing in opposite directions, they form a standing wave of light, stronger in some places and less intense in others. This wave forms a metaphorical hill for the molecule.

    The molecule “starts at the bottom of a hill formed by the counter-propagating laser beams, and it starts climbing that hill just because it has some kinetic energy in it and as it climbs that hill, slowly, the kinetic energy that was its velocity gets converted into potential energy and it slows down and slows down and slows down until it gets to the top of the hill where it’s the slowest,” Mitra said.

    At that point, the molecule moves closer to a region where the light intensity is high and the molecule is more likely absorb a photon that causes it to roll back down to the opposite side. “All [it] can do is keep doing this again and again and again,” Mitra said.

    By looking at images from cameras placed outside the sealed chamber, the scientists inspect how much a cloud of these molecules expands as it travels through the system. The narrower the cloud, the less kinetic energy it has — and therefore the colder it is.

    Analyzing the data further, the researchers saw just how cold. They took it from 22 millikelvin to about 1 millikelvin — just a few thousandths of a decimal point above absolute zero.

    The paper lays out ways to get the molecule even colder, and discusses some of the pathways that opens in a range of physical and chemical research frontiers. The scientists said the study is proof of concept that their method could be used to cool other carefully chosen complex molecules to advance quantum science.

    “What we did here is sort of extending the state of the art,” Mitra said. “It’s always been debated whether we would ever have technology that will be good enough to control complex molecules at the quantum level. This particular experiment is just a stepping stone.”

    This research was supported with funding from the National Science Foundation.

    See the full article here.

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    Harvard University campus
    Harvard University is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

     
  • richardmitnick 9:03 am on September 4, 2020 Permalink | Reply
    Tags: "A step towards a better understanding of molecular dynamics", , Attosecond scale-1×10^18 of a second (one quintillionth of a second), , , , Femtosecond 1x10^15 or 1⁄1 000 000 000 000 000 of a second; that is one quadrillionth- or one millionth of one billionth- of a second., Laser Technology, Polyatomic molecules – molecules made up of several atoms.,   

    From École Polytechnique Fédérale de Lausanne: “A step towards a better understanding of molecular dynamics” 


    From École Polytechnique Fédérale de Lausanne

    04.09.20 [9.4.20]
    Sarah Perrin

    1
    EPFL researchers, working at the boundary between classical and quantum physics, have developed a method for quickly spotting molecules with particularly interesting electron properties.

    Laser technology is giving scientists an ever-closer look into molecular structures, and this sometimes leads to very interesting surprises. At EPFL’s Laboratory of Theoretical Physical Chemistry (LCPT), a research team studying the dynamics of polyatomic molecules – molecules made up of several atoms – came across one such surprise. They found that electrons in these molecules move quite differently from what would be expected in isolated atoms.

    In isolated atoms, the oscillations of electron density are regular, but in most polyatomic molecules, the oscillations quickly become damped. This process is known as decoherence. However, in some molecules the oscillations last longer before decoherence sets in. The EPFL researchers developed a method which captures the physical mechanism behind decoherence, which consequently enables them to identify molecules with long-lasting coherences. Their method could prove interesting in the development of new electron-based technology or studying quantum effects in biomolecules. The findings were recently published in Physical Review Letters.

    “Electron movement takes place extremely rapidly – on an attosecond scale [1×10^18 of a second (one quintillionth of a second)] – so it’s very difficult to observe,” says Nikolay Golubev, a post-doc at LCPT and the study’s lead author. Furthermore, electron motion is strongly coupled to other processes in a molecule. This is why the research team incorporated additional piece of information into their study: the slower dynamics of the atomic nuclei and its influence on that of electrons. It was found that in most molecular structures the slow nuclear rearrangement damps the initially coherent oscillations of electrons and makes them disappear in a few femtoseconds [10^15 or ​1⁄1 000 000 000 000 000 of a second; that is, one quadrillionth, or one millionth of one billionth, of a second].

    A semiclassical approach

    To determine whether this phenomenon is actually taking place, the researchers developed a theoretical technique for an accurate and efficient description of the dynamics of electrons and nuclei after the molecules are ionized by ultrashort laser pulses. They used what’s considered a semiclassical approach in that it combines quantum features, like the simultaneous existence of several states, and classical features, namely classical trajectories guiding the molecular wavefunctions. This method allows scientists to detect the decoherence process much faster, making it easier to analyze many molecules and therefore spot ones that could potentially have long-lasting coherences.

    “Solving the Schrödinger equation for the quantum evolution of a polyatomic molecule’s wavefunction exactly is impossible, even with the world’s largest supercomputers,” says Jiri Vanicek, head of the LCPT. “The semiclassical approach makes it possible to replace the untreatable quantum problem with a still difficult, but solvable, problem, and provides a simple interpretation in which the molecule can be viewed as a ball rolling on a high-dimensional landscape.”

    To illustrate their method, the researchers applied it to two compounds: propiolic acid, whose molecules present long lasting coherence, and propiolamide (a propiolic acid derivative), in which the decoherence is fast. The team hopes to soon be able to test their method on hundreds of other compounds as well.

    Their discovery marks an important step towards a deeper understanding of molecular structures and dynamics, and stands to be a useful tool for observing long-lived electronic coherence in molecules. Backed with a better understanding of the decoherence process, scientists could one day be able to observe exactly how molecules act in biological tissue, for example, or create new kinds of electronic circuits.

    See the full article here .

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    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 9:02 am on September 1, 2020 Permalink | Reply
    Tags: "Record EOS measurement pressures shed light on stellar evolution", , Laser Technology, , Measuring the basic properties of matter such as the equation of state (EOS)., The EOS research is an outgrowth of the NIF Discovery Science “Gbar (gigabar or one billion atmospheres) Campaign.",   

    From Lawrence Livermore National Laboratory: “Record EOS measurement pressures shed light on stellar evolution” 

    From Lawrence Livermore National Laboratory

    8.5.20

    Breanna Bishop
    bishop33@llnl.gov
    925-423-9802

    Charlie Osolin

    1
    Composite image of a white dwarf star inside a NIF hohlraum. A white dwarf with the mass of the sun would be about the size of planet Earth, making it one of densest objects in space after neutron stars and black holes. Credit: Mark Meamber and Clayton Dahlen/LLNL.

    2
    White dwarfs are among the most ancient stellar objects, so their temperatures and predictable lifecycles enable them to work as “cosmic clocks” that can help determine the age of the universe and nearby stars and galaxies. (Greg Stewart/SLAC National Accelerator Laboratory).

    Using the power of the National Ignition Facility (NIF) [below], the world’s highest-energy laser system, researchers at Lawrence Livermore National Laboratory (LLNL) and an international team of collaborators have developed an experimental capability for measuring the basic properties of matter, such as the equation of state (EOS), at the highest pressures thus far achieved in a controlled laboratory experiment.

    The results are relevant to the conditions at the cores of giant planets, the interiors of brown dwarfs (failed stars), the carbon envelopes of white dwarf stars and many applied science programs at LLNL.

    The studies were published today in Nature.

    According to the authors, the overlap with white dwarf envelopes is particularly significant — this new research enables experimental benchmarks of the basic properties of matter in this regime. The results should ultimately lead to improved models of white dwarfs, which represent the final stage of evolution for most stars in the universe.

    After billions of years, the sun and other medium- and low-mass stars will undergo a sequence of expansions and contractions that results in the formation of white dwarfs — the fate of stars that have exhausted their nuclear fuel and collapsed into hot, super-dense mixtures of carbon and oxygen.

    In an effort to resolve disagreements in EOS models at extreme pressures that are relevant to white dwarf stars and various laboratory research projects, scientists conducted the first laboratory studies of matter at the conditions in the outer carbon layer of an unusual class of white dwarf called a “hot DQ.”

    The research subjected solid hydrocarbon samples to pressures ranging from 100 to 450 megabars (100 to 450 million times Earth’s atmospheric pressure) to determine the EOS — the relationship between pressure and compression — in the convection layer of a hot DQ. These were the highest pressures ever achieved in laboratory EOS measurements.

    “White dwarf stars provide important tests of stellar physics models, but EOS models at these extreme conditions are largely untested,” said LLNL physicist Annie Kritcher, the paper’s lead author.

    “NIF can duplicate conditions ranging from the cores of planets and brown dwarfs to those in the center of the sun,” Kritcher added. “We’re also able in NIF experiments to deduce the opacity along the shock Hugoniot (the Hugoniot curve is a plot of the increase in a material’s pressure and density under strong shock compression). This is a necessary component in studies of stellar structure and evolution.”

    Hot DQs have atmospheres primarily composed of carbon — instead of hydrogen and helium as in most white dwarfs — and are unusually hot and bright. Some also pulsate as they rotate because of magnetic spots on their surface, providing observable variations in brightness. Analyzing these variations “provides stringent tests of white dwarf models and a detailed picture of the outcome of the late stages of stellar evolution,” the researchers said.

    They added, however, that current EOS models relevant to white dwarf envelopes at pressures in the hundreds of millions of atmospheres can vary by nearly 10 percent, “a significant uncertainty for stellar evolution models.” Previous researchers have called this the “weakest link in the constitutive physics” that inform white dwarf modeling, Kritcher said.

    The NIF research could help resolve the differences by providing the first EOS data that reach conditions deep in the convection zone of a hot DQ — the region where models show the greatest variability. Results of the experiments agree with EOS models that recognize the extent to which extreme pressures can strip inner-shell electrons from their carbon atoms, decreasing the opacity and increasing the compressibility of the resulting ionized plasma.

    The EOS research is an outgrowth of the NIF Discovery Science “Gbar (gigabar, or one billion atmospheres) Campaign,” initiated by Roger Falcone and his students and postdocs at University of California, Berkeley and other NIF academic users and early career scientists from LLNL. It was supported by the LLNL Laboratory Directed Research and Development Program, the University of California Office of the President, the National Nuclear Security Administration and the Department of Energy Office of Science.

    “The NIF Discovery Science Program enabled our diverse team of researchers — from universities, national labs and industry — to work together on a long-term effort to fundamentally understand the behavior of matter under the most extreme pressures and temperatures,” Falcone said. “NIF is the only facility in the world capable of creating and probing those conditions, and its expert support teams were key to our success. This paper highlights the strength of that collaboration and is evidence for how basic research can find applications in many fields, including astrophysics.”

    In the EOS experiments, NIF’s lasers delivered 1.1 million joules of ultraviolet light to the inside of a pencil-eraser-size hollow gold cylinder called a hohlraum, creating a uniform X-ray “bath” with a peak radiation temperature of nearly 3.5 million degrees. The X-rays were absorbed by a solid plastic sphere mounted in the center of the hohlraum.

    The plastic was heated and ablated, or blown off like rocket exhaust, by the X-rays, creating ablation pressure that launched converging shock waves at 150 to 220 kilometers a second toward the center of the target capsule. The shocks coalesced into a single stronger shock that reached pressures approaching a billion times Earth’s atmosphere.

    Researchers determined the Hugoniot — the density and pressure at the shock front — using temporally and spatially resolved streaked X-ray radiography. The studies showed consistent results for experiments fielded at both cryogenic and ambient temperatures – which produced different initial starting densities – and with varying laser pulse shapes. They also measured the bulk shocked material’s electron temperature and degree of ionization with X-ray Thomson scattering.

    “We measured a reduction in opacity at high pressures, which is associated with a significant ionization of the carbon inner shell,” Kritcher said. “This pressure range along the Hugoniot corresponds to the conditions in the carbon envelope of white dwarf stars. Our data agree with equation-of-state models that include the detailed electronic shell structure.”

    Those models “show a sharper bend in the Hugoniot and higher maximum compression than models that lack electronic shells,” she said, suggesting a “softening” of the EOS. This leads to increased compression resulting from this “pressure ionization.”

    The experimental data can contribute to better models of pulsating hot DQ stars and a more accurate determination of their internal structures, pulsation properties, spectral evolution and complex origin, the researchers concluded.

    Kritcher and Falcone were joined on the paper by LLNL researchers Damian Swift, Tilo Döppner, Benjamin Bachmann, Lorin Benedict, Jonathan DuBois, Jim Gaffney, Sebastien Hamel, Amy Jenei, Natalie Kostinski, Mike MacDonald, Brian Maddox, Madison Martin, Abbas Nikroo, Joe Nilsen, Bruce Remington, Phillip Sterne, Alfredo Correa Tedesco and Heather Whitley; Rip Collins, Laboratory for Laser Energetics at the University of Rochester; Wendi Sweet and Fred Elsner, General Atomics; Gilles Fontaine, University of Montreal; Walter Johnson, University of Notre Dame; Dominik Kraus, Helmholtz-Zentrum Dresden-Rossendorf and Institute of Solid State and Materials Physics at the Technische Universität Dresden in Dresden, Germany; Paul Neumayer, GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany; Didier Saumon, Los Alamos National Laboratory; and Siegfried Glenzer, SLAC National Accelerator Laboratory.

    See the full article here .


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    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security Administration
    Lawrence Livermore National Laboratory (LLNL) is an American federal research facility in Livermore, California, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center (FFRDC), it is primarily funded by the U.S. Department of Energy (DOE) and managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it.
    LLNL is self-described as “a premier research and development institution for science and technology applied to national security.” Its principal responsibility is ensuring the safety, security and reliability of the nation’s nuclear weapons through the application of advanced science, engineering and technology. The Laboratory also applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.

    The Laboratory is located on a one-square-mile (2.6 km2) site at the eastern edge of Livermore. It also operates a 7,000 acres (28 km2) remote experimental test site, called Site 300, situated about 15 miles (24 km) southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of roughly 5,800 employees.

    LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley. It was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence,[2] director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility.

    The new laboratory was sited at a former naval air station of World War II. It was already home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions (i.e. fusion). About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus.

    Lawrence tapped 32-year-old Herbert York, a former graduate student of his, to run Livermore. Under York, the Lab had four main programs: Project Sherwood (the magnetic-fusion program), Project Whitney (the weapons-design program), diagnostic weapon experiments (both for the Los Alamos and Livermore laboratories), and a basic physics program. York and the new lab embraced the Lawrence “big science” approach, tackling challenging projects with physicists, chemists, engineers, and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university’s board of regents named both laboratories for him, as the Lawrence Radiation Laboratory.

    Historically, the Berkeley and Livermore laboratories have had very close relationships on research projects, business operations, and staff. The Livermore Lab was established initially as a branch of the Berkeley laboratory. The Livermore lab was not officially severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, and LLNL’s remote test location as Site 300.[3]

    The laboratory was renamed Lawrence Livermore Laboratory (LLL) in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had exclusively managed and operated the Laboratory since its inception 55 years before. The laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008.[4] The jury found that LLNS breached a contractual obligation to terminate the employees only for “reasonable cause.”[5] The five plaintiffs also have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial.[6] There are 125 co-plaintiffs awaiting trial on similar claims against LLNS.[7] The May 2008 layoff was the first layoff at the laboratory in nearly 40 years.[6]

    On March 14, 2011, the City of Livermore officially expanded the city’s boundaries to annex LLNL and move it within the city limits. The unanimous vote by the Livermore city council expanded Livermore’s southeastern boundaries to cover 15 land parcels covering 1,057 acres (4.28 km2) that comprise the LLNL site. The site was formerly an unincorporated area of Alameda County. The LLNL campus continues to be owned by the federal government.

    LLNL/NIF


    DOE Seal
    NNSA

     
  • richardmitnick 7:34 am on August 25, 2020 Permalink | Reply
    Tags: "A measurement of positronium’s energy levels confounds scientists", , Its simplicity means it can be used to precisely test the theory of quantum electrodynamics., Laser Technology, , Positronium is composed of an electron with a negative charge circling in orbit with a positron with a positive charge — making what’s effectively an atom without a nucleus., Positronium is positively puzzling., ,   

    From University College London via Science News: “A measurement of positronium’s energy levels confounds scientists” 

    UCL bloc

    From University College London

    via

    Science News

    August 24, 2020
    Emily Conover

    The departure from theoretical calculations eludes explanation.

    1
    A negatively charged electron (blue) and a positively charged positron (red) form positronium. A new study of this exotic variety of atom disagrees with predictions, and scientists don’t understand why. Credit T. Tibbitts.

    Positronium is positively puzzling.

    A new measurement of the exotic “atom” — consisting of an electron and its antiparticle, a positron — disagrees with theoretical calculations, scientists report in the Aug. 14 Physical Review Letters. And physicists are at a loss to explain it.

    A flaw in either the calculations or the experiment seems unlikely, researchers say. And new phenomena, such as undiscovered particles, also don’t provide an easy answer, adds theoretical physicist Jesús Pérez Ríos of the Fritz Haber Institute of the Max Planck Society in Berlin. “Right now, the best I can tell you is, we don’t know,” says Pérez Ríos, who was not involved with the new research.

    Positronium is composed of an electron, with a negative charge, circling in orbit with a positron, with a positive charge — making what’s effectively an atom without a nucleus (SN: 9/12/07). With just two particles and free from the complexities of a nucleus, positronium is appealingly simple. Its simplicity means it can be used to precisely test the theory of quantum electrodynamics, which explains how electrically charged particles interact.

    A team of physicists from University College London measured the separation between two specific energy levels of positronium, what’s known as its fine structure. The researchers formed positronium by colliding a beam of positrons with a target, where they met up with electrons. After manipulating the positronium atoms with a laser to put them in the appropriate energy level, the team hit them with microwave radiation to induce some of them to jump to another energy level.

    The researchers pinpointed the frequency of radiation needed to make the atoms take the leap, which is equivalent to finding the size of the gap between the energy levels. While the frequency predicted from calculations was about 18,498 megahertz, the researchers measured about 18,501 megahertz, a difference of about 0.02 percent. Given that the estimated experimental error was only about 0.003 percent, that’s a wide gap.

    The team searched for experimental issues that could explain the result, but came up empty. Additional experiments are now needed to help investigate the mismatch, says physicist Akira Ishida of the University of Tokyo, who was not involved with the study. “If there is still significant discrepancy after further precise measurements, the situation becomes much more exciting.”

    The theoretical prediction also seems solid. In quantum electrodynamics, making predictions involves calculating to a certain level of precision, leaving out terms that are less significant and more difficult to calculate. Those additional terms are expected to be too small to account for the discrepancy. But, “it’s conceivable that you could be surprised,” says theoretical physicist Greg Adkins of Franklin & Marshall College in Lancaster, Pa., also not involved with the research.

    If the experiments and the theoretical calculations check out, the discrepancy might be due to a new particle, but that explanation also seems unlikely. A new particle’s effects probably would have shown up in earlier experiments. For example, says Pérez Ríos, positronium’s energy levels could be affected by a hypothetical axion-like particle. That’s a lightweight particle that has the potential to explain dark matter, an invisible type of matter thought to permeate the universe. But if that type of particle was causing this mismatch, researchers would also have seen its effects in measurements of the magnetic properties of the electron and its heavier cousin, the muon.

    That leaves scientists still searching for an answer, says physicist David Cassidy, a coauthor of the study. “It’s going to be something surprising. I just don’t know what.­”

    See the full article here .

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    Please help promote STEM in your local schools.

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    UCL campus

    UCL was founded in 1826 to open up higher education in England to those who had been excluded from it – becoming the first university in England to admit women students on equal terms with men in 1878.

    Academic excellence and research that addresses real-world problems inform our ethos to this day and are central to our 20-year strategy.

     
  • richardmitnick 11:11 am on August 22, 2020 Permalink | Reply
    Tags: "Scientists See Train of Photons in a New Light", Individual units of light—photons—generally don’t interact with each other., , Laser Technology, Rydberg atoms, The researchers examined how photons in a laser beam interact through atomic intermediaries where photons are dissipated-scattered -and only a single photon is transmitted at a time., The researchers used Rydberg atoms and a pair of lasers to orchestrate a quantum mechanical balancing act.   

    From Joint Quantum Institute: “Scientists See Train of Photons in a New Light” 

    JQI bloc

    From Joint Quantum Institute

    August 4, 2020

    Research Contact
    Przemyslaw Bienias
    bienias@umd.edu

    Media Contact
    Bailey Bedford
    bedfordb@umd.edu

    1
    A cloud of Rydberg atoms can scatter most light to whittle a laser down to train of individual photons. But photons can get re-absorbed within the larger control beam making things more complicated. (Credit: Przemyslaw Bienias, University of Maryland)

    Flashlight beams don’t clash together like lightsabers because individual units of light—photons—generally don’t interact with each other. Two beams don’t even flicker when they cross paths.

    But by using matter as an intermediary, scientists have unlocked a rich world of photon interactions. In these early days of exploring the resulting possibilities, researchers are tackling topics like producing indistinguishable single photons and investigating how even just three photons form into basic molecules of light. The ability to harness these exotic behaviors of light is expected to lead to advances in areas such as quantum computing and precision measurement.

    In a paper recently published in Physical Review Research, JQI Fellow Alexey Gorshkov, JQI postdoctoral researcher Przemyslaw Bienias, and their colleagues describe an experiment that investigates how to extract a train of single photons from a laser packed with many photons.

    In the experiment, the researchers examined how photons in a laser beam can interact through atomic intermediaries so that most photons are dissipated—scattered out of the beam—and only a single photon is transmitted at a time. They also developed an improved model that makes better predictions for more intense levels of light than previous research focused on (greater intensity is expected to be required for practical applications). The new results reveal details about the work to be done to conquer the complexities of interacting photons.

    “Until recently, it was basically too difficult to study anything other than a few of these interacting photons because even when we have two or three things get extremely complicated,” says Gorshkov, whi is also a physicist at the National Institute of Standards and Technology and Fellow of the Joint Center for Quantum Information and Computer Science. “The hope with this experiment was that dissipation would somehow simplify the problem, and it sort of did.”

    Trains, Blockades and Water Slides

    To create the interactions, the researchers needed atoms that are sensitive to the electromagnetic influence of individual photons. Counterintuitively, the right tool for the job is a cloud of electrically neutral atoms. But not just any neutral atoms; these specific atoms—known as Rydberg atoms—have an electron with so much energy that it stays far from the center of the atom.

    The atoms become photon intermediaries when these electrons are pushed to their extreme, remaining just barely tethered to the atom. With the lone, negatively charged electron so far out, the central electrons and protons are left contributing a counterbalancing positive charge. And when stretched out, these opposite charges make the atom sensitive to the influence of passing photons and other atoms. In the experiment, the interactions between these sensitive atoms and photons is tailored to turn a laser beam that is packed with photons into a well-spaced train.

    The cloud of Rydberg atoms is kind of like a lifeguard at a water park. Instead of children rushing down a slide dangerously close together, only one is allowed to pass at a time. The lifeguard ensures the kids go down the slide as a steady, evenly spaced train and not in a crowded rush.

    Unlike a lifeguard, the Rydberg atoms can’t keep the photons waiting in line. Instead they let one through and turn away the rest for a while. The interactions in the cloud of atoms form a blockade around each transmitted photon that scatters other photons aside, ensuring its solitary journey.

    To achieve the effect, the researchers used Rydberg atoms and a pair of lasers to orchestrate a quantum mechanical balancing act. They selected the frequency of the first laser so that its photons would be absorbed by the atoms and scattered in a new direction. But this is the laser that is whittled down into the photon train, and they needed a way to let individual photons through.

    That’s were the second laser comes in. It creates another possible photon absorption that quantum mechanically interferes with the first and allows a single photon to pass unabsorbed. When that single photon gets through, it disturbs the state of the nearby atoms, upsetting the delicate balance achieved with the two lasers and blocking the passage of any photons crowding too closely behind.

    Ideally, if this process is efficient and the stream of photons is steady enough, it should produce a stream of individual photons each following just behind the blockade of the previous. But if the laser is not intense enough, it is like a slow day at the waterpark, when there is not always a kid eagerly awaiting their turn. In the new experiment, the researchers focused on what happens when they crowed many photons into the beam.

    Model (Photon) Trains

    Gorshkov and Bienias’s colleagues performed the experiment, and the team compared their results to two previous models of the blockade effect. Their measurements of the transmitted light matched the models when the number of photons was low, but as the researchers pushed the intensity to higher levels, the results and the models’ predictions started looking very different. It looked like something was building up over time and interfering with the predicted, desired formation of well-defined photon trains.

    The team determined that the models failed to account for an important detail: the knock-on effects of the scattered photons. Just because those photons weren’t transmitted, doesn’t mean they could be ignored. The team suspected the models were being thrown off by some of the scattered light interacting with Rydberg atoms outside of the laser beam. These additional interactions would put the atoms into new states, which the scientists call pollutants, that would interfere with the efficient creation of a single photon train.

    The researchers modified one of their models to capture the important effects of the pollutants without keeping track of every interaction in the larger cloud of atoms. While this simplified model is called a “toy model,” it is really a practical tool that will help researchers push the technique to greater heights in their larger effort to understand photon interactions. The model helped the researchers explain the behavior of the transmitted light that the older models failed to capture. It also provides a useful way to think about the physics that is preventing an ideal single photon train and might be useful in judging how effectively future experiments prevent the undesirable affects—perhaps by using cloud of atoms with different shapes.

    “We are quite optimistic when it comes to removing the pollutants or trying to create less of them,” says Bienias. “It will be more experimentally challenging, but we believe it is possible.”

    See the full article here .


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    Please help promote STEM in your local schools.

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    JQI supported by Gordon and Betty Moore Foundation

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 8:54 am on August 21, 2020 Permalink | Reply
    Tags: "In a Lab on Earth Scientists Just Replicated Pressures Found on White Dwarf Stars", , , Laser Technology, Lawrence Livermore National Laboratory, , ,   

    From Lawrence Livermore National Laboratory via Science Alert: “In a Lab on Earth, Scientists Just Replicated Pressures Found on White Dwarf Stars” 

    From Lawrence Livermore National Laboratory

    via

    ScienceAlert

    Science Alert

    21 AUGUST 2020
    MICHELLE STARR

    1
    (Mark Meamber/Clayton Dahlen/Lawrence Livermore National Laboratory)

    For the first time, pressure over 100 times that found in Earth’s core has been generated in a lab, setting a new record.

    Using the highest-energy laser system in the world, physicists briefly subjected solid hydrocarbon samples to pressures up to 450 megabars, meaning 450 million times Earth’s atmospheric pressure at sea level.

    That’s equivalent to the pressures found in the carbon-dominated envelopes of a rare type of white dwarf star – some of the densest objects in the known Universe. It could help us to better understand the effect those pressures have on changes in the stars’ brightness.

    Most of the stars in the Universe will end their lives as a white dwarf, including our Sun. As they reach the end of their main-sequence, hydrogen-fusing days, they’ll puff out into red giants, eventually ejecting most of their material out into space as the core collapses into a white dwarf – a ‘dead’ star no longer able to support fusion.

    White dwarfs are dense. They can be up to around 1.5 times the mass of the Sun, packed into a sphere the size of Earth. Only something called electron degeneracy pressure keeps the star from collapsing under its own gravity.

    At around 100 megabars of pressure, electrons are stripped from their atomic nuclei – and, because identical electrons can’t occupy the same space, these electrons supply the outward pressure that keeps the star from collapsing.

    This pressure doesn’t just influence how compressible the material is, it also decreases the opacity of the plasma ionised by the loss of electrons. And the links between these properties are described by the material’s equations of state, which also can be used to calculate such properties as the temperature profile and rate of cooling.

    There are, however, some disagreements in equation of state (EOS) models for extreme pressures; for white dwarf stars, the EOS models along what is known as the shock Hugoniot – the curve that plots the increase in pressure and density under compression – can vary by 10 percent.

    This can be a problem when trying to understand the fundamental properties of the Universe, because white dwarf stars should be quite predictable. Although they shine, the light is only from residual heat, not fusion, and their cooling rate can therefore be used as a sort of clock to confirm the age of the Universe, for instance, and the ages of the stars around them.

    So this is what the research team is trying to resolve, using the laser system at the Lawrence Livermore National Laboratory’s National Ignition Facility (NIF).


    National Ignition Facility at LLNL

    “White dwarf stars provide important tests of stellar physics models, but EOS models at these extreme conditions are largely untested,” said physicist Annie Kritcher of the Lawrence Livermore National Laboratory.

    “NIF can duplicate conditions ranging from the cores of planets and brown dwarfs to those in the centre of the Sun. We’re also able in NIF experiments to deduce the opacity along the shock Hugoniot. This is a necessary component in studies of stellar structure and evolution.”

    The experimental set-up consisted of a small, solid, one-millimetre hydrocarbon (plastic) bead inside a hollow gold cylinder about the size of a pencil eraser called a hohlraum. This was then irradiated with 1.1 million joules of ultraviolet light delivered by the lasers, which created a uniform X-ray bath heating the plastic sphere to nearly 3.5 million Kelvin.

    The outer layer of the bead was destroyed through ablation, which created a spherical ablation shockwave travelling up to 220 kilometres per second that converged spherically, resulting in increasing pressure as it propagated through the bead.

    By the way, all this happened extraordinarily quickly – the shockwave took just 9 nanoseconds to traverse the entire sample – but, using X-ray radiography, the research team was able to record the shock Hugoniot, measuring pressures of 100 megabars on the outside of the bead to 450 megabars by the time it reached the middle.

    The pressure inside Earth’s core is 3.6 megabars. And, previously, the highest pressure achieved in this kind of controlled experiment was 60 megabars.

    The pressure generated in their experiment, the team said, is consistent with the carbon envelope – the convection region surrounding the core – seen in what are known as “hot DQ” white dwarfs. These are relatively rare; unlike ordinary white dwarfs, whose atmospheres are composed primarily of hydrogen and helium, hot DQs have primarily carbon atmospheres, and they’re unusually hot and bright.

    Some of them also pulsate as they spin, resulting in brightness variations. To understand these pulsations and model them, we need an accurate understanding of how the matter in the star behaves under pressure.

    In addition to X-ray radiography, the physicists used X-ray Thomson scattering to measure the electron temperature and degree of ionisation in the sample. It, too, turned up hot DQ.

    “We measured a reduction in opacity at high pressures, which is associated with a significant ionisation of the carbon inner shell,” Kritcher said.

    “This pressure range along the Hugoniot corresponds to the conditions in the carbon envelope of white dwarf stars. Our data agree with equation-of-state models that include the detailed electronic shell structure.”

    What this means is that the ionisation ultimately makes the material more compressible than models that don’t have electronic shells. This places new constraints on the compressibility and opacity of the carbon envelope in hot DQs, which in turn can contribute to a better understanding of their properties and evolution. All this, from a lab experiment on our own planet.

    The research has been published in Nature.

    See the full article here .


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    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security Administration
    Lawrence Livermore National Laboratory (LLNL) is an American federal research facility in Livermore, California, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center (FFRDC), it is primarily funded by the U.S. Department of Energy (DOE) and managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it.
    LLNL is self-described as “a premier research and development institution for science and technology applied to national security.” Its principal responsibility is ensuring the safety, security and reliability of the nation’s nuclear weapons through the application of advanced science, engineering and technology. The Laboratory also applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.

    The Laboratory is located on a one-square-mile (2.6 km2) site at the eastern edge of Livermore. It also operates a 7,000 acres (28 km2) remote experimental test site, called Site 300, situated about 15 miles (24 km) southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of roughly 5,800 employees.

    LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley. It was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence,[2] director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility.

    The new laboratory was sited at a former naval air station of World War II. It was already home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions (i.e. fusion). About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus.

    Lawrence tapped 32-year-old Herbert York, a former graduate student of his, to run Livermore. Under York, the Lab had four main programs: Project Sherwood (the magnetic-fusion program), Project Whitney (the weapons-design program), diagnostic weapon experiments (both for the Los Alamos and Livermore laboratories), and a basic physics program. York and the new lab embraced the Lawrence “big science” approach, tackling challenging projects with physicists, chemists, engineers, and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university’s board of regents named both laboratories for him, as the Lawrence Radiation Laboratory.

    Historically, the Berkeley and Livermore laboratories have had very close relationships on research projects, business operations, and staff. The Livermore Lab was established initially as a branch of the Berkeley laboratory. The Livermore lab was not officially severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, and LLNL’s remote test location as Site 300.[3]

    The laboratory was renamed Lawrence Livermore Laboratory (LLL) in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had exclusively managed and operated the Laboratory since its inception 55 years before. The laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008.[4] The jury found that LLNS breached a contractual obligation to terminate the employees only for “reasonable cause.”[5] The five plaintiffs also have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial.[6] There are 125 co-plaintiffs awaiting trial on similar claims against LLNS.[7] The May 2008 layoff was the first layoff at the laboratory in nearly 40 years.[6]

    On March 14, 2011, the City of Livermore officially expanded the city’s boundaries to annex LLNL and move it within the city limits. The unanimous vote by the Livermore city council expanded Livermore’s southeastern boundaries to cover 15 land parcels covering 1,057 acres (4.28 km2) that comprise the LLNL site. The site was formerly an unincorporated area of Alameda County. The LLNL campus continues to be owned by the federal government.

    LLNL/NIF


    DOE Seal
    NNSA

     
  • richardmitnick 8:18 am on August 15, 2020 Permalink | Reply
    Tags: Advanced Photon Source (APS) synchrotron at Argonne, , , , Laser Technology, Linda Young, , , ,   

    From University of Chicago and Argonne National Laboratory: Women in STEM- “UChicago physicist leaves mark on X-ray sciences as leader, mentor” Linda Young 

    U Chicago bloc

    From University of Chicago

    and

    Argonne Lab
    Argonne National Laboratory

    Aug 10, 2020
    Maggie Hudson

    1
    For decades, Prof. Linda Young has made an impact both as a researcher and a mentor. She is pictured here with (left to right) Argonne colleagues Anthony DiChiara, Maria Chan and Anirudha Sumant. Photo courtesy of Argonne National Laboratory.

    Argonne’s Linda Young searches for new X-ray laser uses and ways to support junior scientists.

    Like many of us, University of Chicago physicist Linda Young is working from home these days, though her home is more unique than most.

    “We live in Enrico Fermi’s old house,” she said. “I always hope that I’ll breathe some inspiration from being in this house, but I’m not sure if I have.”

    Whether through Fermi’s inspiration or her own scientific prowess, Young—a part-time professor in UChicago’s Department of Physics—has built an impressive research career studying the interactions of X-rays with matter. She leads the atomic, molecular and optical (AMO) physics group at Argonne National Laboratory, where she previously served as the head of the X-ray Science Division—overseeing experiments at one of the world’s top X-ray sources.

    Developing X-ray lasers

    X-ray interactions with matter have a long and storied history, beginning with the discovery of X-rays in 1895. Scientists harnessed this very high energy form of light to reveal unseen secrets of our world, allowing us to glimpse the bones beneath our skin and to decode the unique arrangement of atoms that make up different molecules.

    Over the past century, scientists have continuously improved the strength of X-ray light sources and used them in new ways to understand the makeup of materials. Ten years ago, Young said, these experiments took a huge leap forward with the development of a new type of X-ray source: the X-ray free-electron laser [XFEL].

    “Now, because we have X-ray free-electron lasers, new life has been injected into the topic of X-ray interactions with matter,” Young said. “We suddenly can have X-ray pulses that are of very short duration, very short wavelength, and very high intensity.”

    At Argonne, Young plays an instrumental role in understanding how these X-ray lasers work and what they can be used for. “In our group, we work together to figure out how we can really utilize these super strong, coherent X-ray pulses to divine the secrets of matter,” she said.

    Though Young has risen through the ranks to become an expert in X-ray physics, she began her career at Argonne with a background in optical laser spectroscopy. She integrated this knowledge into the AMO physics group’s studies of atomic structure; in 1994, as the youngest scientist in the group, Young was promoted to group leader.

    Young’s tenure as group leader coincided with the opening of the Advanced Photon Source (APS) synchrotron at Argonne [below], a kilometer-long electron storage ring used as a source of bright X-ray beams. To utilize the convenience and capabilities of this world-class laboratory, the group shifted its focus to X-ray science. Young hired new team members with expertise in X-ray physics and led the design of two beamlines—X-ray laboratories within APS with unique instruments and capabilities.

    The AMO physics group pushed the boundaries of the study of X-rays’ interactions with matter, using facilities at the APS as well as other X-ray sources. The group’s success in the field and interest in powerful X-ray techniques led to their involvement with the­­­ first X-ray free-electron laser (XFEL).

    Young travels to international laboratories to do groundbreaking research with the world’s best scientists, but she notes that these experiences have more than just a scientific impact. “I think doing experiments at light sources around the world is very enriching,” she said. “You get to have insight into different international perspectives and make friends around the globe.”

    X-ray scientists compete for funding and acclaim, but when they come together at international laboratories, they work as a team to tackle big problems. Their dream, Young explained, is to use XFELs to look at complex molecules in a new way. The ultra-strong, ultra-short pulses of X-ray light should allow them to take snapshots of the locations of all the atoms in a molecule as it moves around in a solution. Putting these snapshots together could create a 3D image of a huge, complicated molecule like a protein.

    Mentoring the next generation

    Young brings these ideas back to the UChicago, where she teaches a graduate course on X-ray physics and applications. She enjoys sharing her passion for these complex experiments with students who would not typically work with advanced X-ray techniques. As she interacts with students, she adapts her course in response to their feedback and encourages students to pursue their interests through the lens of X-ray sciences.

    3
    Prof. Linda Young (center) at SLAC National Accelerator Laboratory with (left to right) Christoph Bostedt, Steve Southworth, John Bozek, Steve Pratt and Yuelin Li. (Photo by Brad Plummer/SLAC.)

    “I think it’s really invigorating to teach students because they’re so eager to learn, and you learn a lot of things from them,” said Young.

    Her willingness to learn and adapt has served her well as a mentor at both Argonne and UChicago. Young has mentored a number of junior scientists at Argonne, helping them make decisions about their career path and even assisting with connections for future job placements.

    At UChicago, she works to make the physics department supportive of all students and serves as chair of the department’s equity, diversity and inclusion committee. She coordinates seminars with speakers from underrepresented groups in the sciences and hosted the 2020 American Physical Society Conference for Undergraduate Women in Physics at UChicago.

    Young notes that amidst the growing movement against systemic racism, she has realized that these previous activities to promote diversity in the department were not enough. The committee has reached out through student-led town hall meetings and seeking feedback on how they can better support minorities in physics. In the first meeting, students requested more opportunities for mentorship, and Young is excited to help them achieve their goals.

    As more student feedback comes in, Young is listening and ready to work for lasting change in the physics department. “I think that this is a really important time for committees to step up and really do something concrete. I am looking forward to doing whatever I can in my own way.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    About the Advanced Photon Source

    The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

    This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

    We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

    The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
  • richardmitnick 11:20 am on July 28, 2020 Permalink | Reply
    Tags: "Shining a light on the quantum world", , In the quantum world light is two things: both a wave and a small particle called a photon., Laser Technology, , , , , Quantum light   

    From MIT News: “Shining a light on the quantum world” 

    MIT News

    From MIT News

    July 27, 2020
    Fernanda Ferreira | School of Science

    1
    MIT graduate student Nicholas Rivera (middle) and two students from Professor Ido Kaminer’s lab visit Masada National Park near the Dead Sea in Israel. Photo courtesy of the researchers.

    2
    Researchers at MIT and Israel’s Technion used a thin-film material composed of layers of gallium-arsenide and indium-gallium-arsenide, overlaid with a layer of graphene, as shown in this diagram, to produce strong interactions between light and particles that could someday enable highly tunable lasers orL EDs. Image courtesy of the researchers.

    3
    Front row, left to right: Ido Kaminer, Nicholas Rivera, and Bo Zhen. Back row, left to right: professors John Joannopoulos and Marin Soljačić. Photo courtesy of the researchers.

    With funding from MISTI, physicists at MIT and in Israel collaborate to improve understanding and use of quantum light.

    In the universe, there is the world we can see with the naked eye: trees, planes in the sky, dishes in the sink. But there are other worlds that reveal themselves with the help of a magnifying glass, telescope, or microscope. With these, we can see up into the universe or down into the smallest particles that make it up. The smallest of these is a world populated by particles smaller than an atom: the quantum world.

    Physicists who probe this world study how these subatomic particles interact with one another, often in ways not predicted by behavior at the atomic or molecular level. One such physicist is Nicholas Rivera, who studies light-matter interactions at the quantum level.

    Unfinished business

    In the quantum world, light is two things: both a wave and a small particle called a photon. “I was always fascinated with light, especially the quantum nature of light,” says Rivera, a Department of Physics graduate student in Professor Marin Soljačić’s group.

    According to Rivera, there is still a lot we don’t know about quantum light, and uncovering these unknowns may prove useful for a number of applications. “It’s connected to a lot of interesting problems,” says Rivera, such as how to make better quantum computers and lasers at new frequencies like ultraviolet and X-ray. It’s this dual nature of the work — with fundamental questions coupled with practical solutions — that attracted Rivera to his current area of research.

    Rivera joined Soljačić’s group in 2013, when he was an undergraduate at MIT. Since then his research has focused on how light and matter interact at the most elementary level, between quanta of light, also called photons, and electrons of matter. These interactions are governed by the laws of quantum electrodynamics and involve the emission of photons by electrons that hop up and down energy levels. This may sound simple, but it is surprisingly difficult because light and matter are operating on two different size scales, which often means these interactions are inefficient. One specific goal of Rivera’s work is to improve that efficiency.

    “The atom is this tiny thing, a 10th of a nanometer large,” says Rivera. But when light takes the form of a wave, its wavelengths are much larger than an atom. “The idea is that, because of this mismatch, many of the possible ways that an electron could release a photon are just too slow to be observable.” Rivera uses theory to figure out how light and matter could be manipulated to allow for new types of interactions and ways to intentionally change the quantum state of light.

    Inefficient interactions are often thought of as “forbidden” because, in normal circumstances, they would take billions of years to happen. “The forbidden light-matter interactions project is something we have been thinking about for many years, but we didn’t have a suitable material-system platform for it,” says Soljačić. In 2015, graphene plasmons arrived on the scene, and forbidden interactions could be explored.

    Graphene is an ultra-thin 2D material, and plasmons are another quantum-scale particle related to the oscillation of electrons. In these ultra-thin materials, light can be “shrunk” so that the wavelengths are closer to the scale of the electrons, making forbidden interactions possible.

    Rivera’s first paper on this topic [Science], published the summer after he graduated with his bachelor’s degree in 2016, was the start of his longstanding collaboration with Ido Kaminer, an assistant professor at the Technion-Israel Institute of Technology. But Rivera wasn’t done with light-matter interactions. “There were so many other directions that one could go with that work, and I really wanted the ability to probe all of them,” Rivera says, and he decided to stay in Soljačić’s group for his PhD.

    A natural match

    That first collaboration with Kaminer, who was then a postdoc in Soljačić’s group, was a pivotal moment in Rivera’s career as a physicist. “I was working on a different project with Marin, but then he invited me to his office with Ido and told me about the project that would become the 2016 paper,” says Rivera. According to Soljačić, putting Kaminer and Rivera together “was a natural match.”

    Kaminer moved to the Technion in 2018, which was when Rivera took his first trip to Haifa, Israel, with funds provided by MISTI-Israel, a program within the MIT International Science and Technology Initiatives (MISTI). There, he gave a seminar and met with students and professors. “That visit seeded some projects that we’re still working on today,” says Rivera, such as a project where vacuum forces were used to generate X-ray photons. [physicsworld].

    With the help of lasers and optical materials, it’s relatively easy to generate photons of visible light, but making X-ray photons is much harder. “We don’t have lasers the same way we do for visible light, and we don’t have as many materials to manipulate X-rays,” says Rivera. The search for new strategies for generating X-ray photons is important, Rivera says, because these photons can help scientists explore physics at the atomic scale.

    This past January, Rivera visited Israel for the third time. On these trips, “[we make] progress on the collaborations we have with the students, and also brainstorm new projects,” says Rivera. According to Kaminer, the in-person brainstorming is vital when coming up with new ideas. “Such creative ideas are, in the end, the most important part of our work as scientists,” Kaminer explains. During each visit, Rivera and Kaminer sketch out a research plan for the next six months to year, such as continuing to investigate new ways to control and generate quantum sources of X-ray photons.

    When investigating the theory of light-matter interactions, the potential applications are never far from Rivera’s mind. “We’re trying to think about applications that could potentially be realized next year and in the next five years, but even potentially further down the line.”

    For Rivera, being able to be in the same place as his collaborators is a major boon, and he doubts the continued collaboration with Kaminer would be as active if he hadn’t taken that first trip to Haifa in 2018. “And the hummus isn’t bad,” he jokes.

    When Soljačić introduced Rivera and Kaminer five years ago, neither expected that the collaboration would still be going strong. “It’s hard to anticipate what collaborations will be successful in the long term,” says Kaminer. “But more important than the collaboration is the friendship,” he adds.

    The deeper Rivera explores the quantum aspects of light-matter interactions, the more potential avenues of exploration open up. “It just keeps branching,” says Rivera. And he envisions himself continuing to visit Kaminer in Israel, no matter where his research takes him next. “It’s a lifelong collaboration at this point.”

    See the full article here .


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  • richardmitnick 10:28 am on July 3, 2020 Permalink | Reply
    Tags: "Towards Lasers Powerful Enough to Investigate a New Kind of Physics", , Institut national de la recherche scientifique INRS Quebec, Laser Technology,   

    From Institut national de la recherche scientifique INRS Quebec: “Towards Lasers Powerful Enough to Investigate a New Kind of Physics” 

    1

    From Institut national de la recherche scientifique INRS Quebec

    July 2, 2020
    Audrey-Maude Vézina

    In a paper that made the cover of the journal Applied Physics Letters, an international team of researchers has demonstrated an innovative technique for increasing the intensity of lasers. This approach, based on the compression of light pulses, would make it possible to reach a threshold intensity for a new type of physics that has never been explored before: quantum electrodynamics phenomena.

    1

    Since the invention of frequency drift amplification in 1985 by Donna Strickland and Gérard Mourou, laser power has increased phenomenally, to finally reach a limit in the last years. Many research groups are amplifying the energy of the laser to increase its power, but this approach is expensive and requires beams and optics that are very large, more than a metre in size.

    Researchers Jean-Claude Kieffer of the Institut national de la recherche scientifique (INRS), E. A. Khazanov of the Institute of Applied Physics of the Russian Academy of Sciences and Gérard Mourou, Professor Emeritus of the Ecole Polytechnique in France, who was awarded the Nobel Prize in Physics in 2018, have chosen another direction to achieve a power of around 10^23 Watts (W). Rather than increasing the energy of the laser, they decrease the pulse duration to only a few femtoseconds. This would keep the system within a reasonable size and keep operating costs down.

    To generate the shortest possible pulse, the researchers are exploiting the effects of non-linear optics. “A laser beam is sent through an extremely thin and perfectly homogeneous glass plate. The particular behaviour of the wave inside this solid medium broadens the spectrum and allows for a shorter pulse when it is recompressed at the exit of the plate,” explains Jean-Claude Kieffer, co-author of the study published online on 15 June 2020 in the journal Applied Physics Letters.

    Installed in the Advanced Laser Light Source (ALLS) facility at INRS, the researchers limited themselves to an energy of 3 joules for a 10-femtosecond pulse, or 300 terawatts (1012W).

    2
    Advanced Laser Light Source (ALLS) Université du Québec – Institut national de la recherche scientifique (INRS), Varennes, Québec

    They plan to repeat the experiment with an energy of 13 joules over 5 femtoseconds, or an intensity of 3 petawatts (1015 W). “We would be among the first in the world to achieve this level of power with a laser that has such short pulses,” says Professor Kieffer.

    “If we achieve very short pulses, we enter relativistic problem classes. This is an extremely interesting direction that has the potential to take the scientific community to new horizons,” says Professor Kieffer. “It was a very nice piece of work solidifying the paramount potential of this technique,” concludes Gérard Mourou.

    See the full article here.

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