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  • richardmitnick 8:19 am on February 8, 2018 Permalink | Reply
    Tags: , , Laser Technology, , ,   

    From STFC: “UK laser experiment mimics black hole environment” 


    STFC

    7 February 2018

    1
    The Gemini laser at CLF. (Credit: STFC)

    UK physicists have for the first time used an extremely powerful laser beam to slow down electrons travelling at near-light speeds – a quantum mechanical phenomenon thought to occur only around objects like black holes. By producing this effect in a lab, scientists hope to provide valuable insight into subatomic processes in the universe’s most extreme environments.

    Fast electrons, especially when they travel at near light speeds, are very difficult to stop. Often you require highly dense materials – such as lead – to stop them or slow them down. But now, scientists have shown that they can slow these superfast electrons using a very thin sheet of light; they squeeze trillions of light particles – photons – into a sheet that is a fraction of human hair in thickness.

    When light hits an object some of the light bounces back from the surface, often changing its colour (to even X-rays and gamma rays if the object is moving fast) – however, if the object is moving extremely fast and if the light is incredibly intense, strange things can happen.

    Electrons, for example, can be shaken so violently that they actually slow down because they radiate so much energy. Quantum physics is required to fully explain this phenomenon. Physicists call this process ‘radiation reaction’, which is thought to occur around objects such as black holes and quasars.

    Now, a team of researchers have demonstrated radiation reaction for the first time using the Gemini laser at the Science and Technology Facilities Council’s Central Laser Facility in Oxfordshire.

    Gemini scientist Dr Dan Symes said: “Experiments like these are extremely complicated to set up and very difficult to perform. Essentially, you need to focus a laser beam as big as an A4 size paper sheet down to a few microns and hit it with a micron-sized electron bullet that’s travelling very close to the speed of light.”

    Gemini Group Leader, Dr Rajeev Pattathil added: “You need two extremely well-synchronised high power laser beams for this: one to produce the high energy electron beam and another to shoot it. Gemini’s dual-beam capability makes it an ideal facility for these types of experiments. Gemini is one of the very few places in the world where such cutting-edge experiments can be performed.”

    The research team, led by Imperial College academic Dr Stuart Mangles, were able to observe this radiation reaction by colliding a laser beam that is one quadrillion times brighter than light at the surface of the Sun with a high-energy beam of electrons. All this energy had to be delivered in a very short duration – just 40 femtoseconds long, or 40 quadrillionths of a second.

    Senior author of the study [Physical Review X] Dr Mangles said: “We knew we had been successful in colliding the two beams when we detected very bright high energy gamma-ray radiation.

    “The real result then came when we compared this detection with the energy in the electron beam after the collision. We found that these successful collisions had a lower than expected electron energy, which is clear evidence of radiation reaction.”

    Study co-author Professor Alec Thomas, from Lancaster University and the University of Michigan, added: “One thing I always find so fascinating about this is that the electrons are stopped as effectively by this sheet of light, a fraction of a hair’s breadth thick, as by something like a millimetre of lead. That is extraordinary.”

    However more experiments at even higher intensity or with even higher energy electron beams will be needed to confirm if this is true. The team will be carrying out these experiments in the coming year.

    See the full article here .

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    STFC Hartree Centre

    Helping build a globally competitive, knowledge-based UK economy

    We are a world-leading multi-disciplinary science organisation, and our goal is to deliver economic, societal, scientific and international benefits to the UK and its people – and more broadly to the world. Our strength comes from our distinct but interrelated functions:

    Universities: we support university-based research, innovation and skills development in astronomy, particle physics, nuclear physics, and space science
    Scientific Facilities: we provide access to world-leading, large-scale facilities across a range of physical and life sciences, enabling research, innovation and skills training in these areas
    National Campuses: we work with partners to build National Science and Innovation Campuses based around our National Laboratories to promote academic and industrial collaboration and translation of our research to market through direct interaction with industry
    Inspiring and Involving: we help ensure a future pipeline of skilled and enthusiastic young people by using the excitement of our sciences to encourage wider take-up of STEM subjects in school and future life (science, technology, engineering and mathematics)

    We support an academic community of around 1,700 in particle physics, nuclear physics, and astronomy including space science, who work at more than 50 universities and research institutes in the UK, Europe, Japan and the United States, including a rolling cohort of more than 900 PhD students.

    STFC-funded universities produce physics postgraduates with outstanding high-end scientific, analytic and technical skills who on graduation enjoy almost full employment. Roughly half of our PhD students continue in research, sustaining national capability and creating the bedrock of the UK’s scientific excellence. The remainder – much valued for their numerical, problem solving and project management skills – choose equally important industrial, commercial or government careers.

    Our large-scale scientific facilities in the UK and Europe are used by more than 3,500 users each year, carrying out more than 2,000 experiments and generating around 900 publications. The facilities provide a range of research techniques using neutrons, muons, lasers and x-rays, and high performance computing and complex analysis of large data sets.

    They are used by scientists across a huge variety of science disciplines ranging from the physical and heritage sciences to medicine, biosciences, the environment, energy, and more. These facilities provide a massive productivity boost for UK science, as well as unique capabilities for UK industry.

    Our two Campuses are based around our Rutherford Appleton Laboratory at Harwell in Oxfordshire, and our Daresbury Laboratory in Cheshire – each of which offers a different cluster of technological expertise that underpins and ties together diverse research fields.

    The combination of access to world-class research facilities and scientists, office and laboratory space, business support, and an environment which encourages innovation has proven a compelling combination, attracting start-ups, SMEs and large blue chips such as IBM and Unilever.

    We think our science is awesome – and we know students, teachers and parents think so too. That’s why we run an extensive Public Engagement and science communication programme, ranging from loans to schools of Moon Rocks, funding support for academics to inspire more young people, embedding public engagement in our funded grant programme, and running a series of lectures, travelling exhibitions and visits to our sites across the year.

    Ninety per cent of physics undergraduates say that they were attracted to the course by our sciences, and applications for physics courses are up – despite an overall decline in university enrolment.

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  • richardmitnick 11:45 am on February 6, 2018 Permalink | Reply
    Tags: , Laser Technology, ,   

    From Technion: “Future of Semiconductor Lasing: Topological Insulator Lasers” 

    Technion bloc

    Israel Institute of Technology

    February 1, 2018

    Israeli and US researchers have developed a new highly efficient coherent and robust semiconductor laser system: the topological insulator laser.

    The findings are presented in two new joint research papers, one describing theory and the other experiments, published online by the prestigious journal Science on Thursday, February 1.

    G. Harari et al. Topological insulator laser: Theory. Science. Published online February 1, 2018, http://science.sciencemag.org/content/early/2018/01/31/science.aar4003
    M. Bandres et al. Topological insulator laser: Experiments. Science Published online February 1, 2018 http://science.sciencemag.org/content/early/2018/01/31/science.aar4005

    1
    Group photo (L-R) : Dr. Miguel A. Bandres, Professor Mordechai Segev and Gal Harari
    Credit: Nitzan Zohar, Office of the Spokesperson, Technion

    Topological insulators are one of the most innovative and promising areas of physics in recent years, providing new insight into the basic understanding of protected transport. These are special materials that are insulators in their interior but conduct a “super-current” on their surface: the current on their surface is not affected by defects, sharp corners or disorder; it continues unidirectionally without being scattered.

    The studies were conducted by Moti Segev, who holds the Robert J. Shillman Distinguished Research Chair at the Technion – Israel Institute of Technology and his team: Dr. Miguel A. Bandres and Gal Harari; in collaboration with Professors Demetrios N. Christodoulides and Mercedeh Khajavikhan and their students Steffen Wittek, Midya Parto and Jinhan Ren at CREOL, College of Optics and Photonics, University of Central Florida, together with scientists from the US and Singapore.

    Several years ago, the same group from the Technion introduced these ideas in photonics, and demonstrated a Photonic Topological Insulator, where light travels around the edges of a two-dimensional array of waveguides without being affected by defects or disorder.

    Now, the researchers found a way to use the properties of photonic topological insulators to build a new type of laser which shows a unique fundamental behavior and greatly improves the robustness and the performance of lasers arrays, opening the door for a vast number of future applications.

    “This new laser system went against all common knowledge about topological insulators” said Prof. Segev of the Technion. “In a nut shell, the unique robustness properties of topological insulators were believed to fail when the system contains gain, as all lasers must have. But we have shown that this special robustness survives in laser systems that have a special (“topological”) design, and is able to make the lasers much more efficient, more coherent, and at the same time immune to all kinds of fabrication imperfections, defects and alike. This seems to be an exciting avenue to make arrays of miniature lasers work together as one: a single highly coherent high power laser.”

    In their research, the scientists built a special array of micro ring resonators whose lasing mode exhibits topologically-protected transport – light propagates in one direction along the edges of the laser array, immune to defects and disorder and unaffected by the shape of the edges. This in turn, as they experimentally demonstrated, leads to highly efficient single-mode lasing that lasts high above the laser threshold. “It is a great pleasure to see fundamental research pans out to have such profound yet tangible applications” said Prof. Christodouldies from UCF.

    The fabricated array used standard semiconductor materials, without the need for magnetic fields or exotic magneto-optic materials; hence it can be integrated in semiconductor devices. “In recent years, we have found new tricks to manipulate light in an unprecedented way. Here by using clever designs, we fooled photons to feel as if they are experiencing a magnetic field and they have spin,” said Prof. Khajavikhan, one of the lead scientists in the team.

    The researchers demonstrated that not only are topological insulator lasers theoretically possible and experimentally feasible but that integrating these properties create more highly efficient lasers. As such, the results of the study pave the way towards a novel class of active topological photonic devices that may be integrated with sensors, antennas and other photonic devices.

    2
    Fig. 2 Illustration of the topological insulator laser: the light goes around the perimeter unobstructed by sharp corner or disorder, and eventually exits through the output port.

    3
    Fig. 4 Top view photograph of the intensity lasing pattern of the topological insulator laser. Images Credit: S. Wittek (CREOL) & M.A. Bandres (Technion).

    4
    Optical Setup (CREOL- Technion collaboration).

    See the full article here .

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    Technion Campus

    A science and technology research university, among the world’s top ten,
    dedicated to the creation of knowledge and the development of human capital and leadership,
    for the advancement of the State of Israel and all humanity.

     
  • richardmitnick 1:29 pm on February 3, 2018 Permalink | Reply
    Tags: , , , Laser Technology,   

    From Ethan Siegel: “Ask Ethan: Can A Laser Really Rip Apart Empty Space?” 

    From Ethan Siegel

    Feb 3, 2018

    1
    Tabletop laser experiments might not have the highest energy output for lasers, but they can out-compete even the lasers used to ignite nuclear fusion in terms of power. Could the quantum vacuum finally yield? United States Air Force.

    Empty space, as it turns out, isn’t so empty. The fluctuations in the vacuum of space itself mean that even if you take all the matter and radiation out of a region of space, there’s still a finite amount of energy there, inherent to space itself. If you fire a powerful enough laser at it, can you, as a Science magazine story called it, break the vacuum and rip apart empty space? That’s what our Patreon supporter Malcolm Schongalla wants to know, as he asks:

    Science Magazine recently reported that Chinese physicists will start building a 100-petawatt(!!!) laser this year. Can you please explain how they plan to achieve this, and what unique phenomenon this will help physicists explore? Such as, what exactly is “breaking the vacuum?”

    The story is real, verified, and a little bit exaggerated in terms of claims that it can break the vacuum, as though such a thing were possible. Let’s dive into the real science to find out what’s really happening.

    2
    A set of Q-line laser pointers showcase the diverse colors and compact size that now are commonplace for lasers. The continuously-operating lasers shown here are very low power, measuring just watts or fractions of watts, while the record is in petawatts. Wikimedia Commons user Netweb01.

    The very idea of a laser itself is still relatively novel, despite how widespread they are. Originally an acronym standing for Light Amplification by Stimulated Emission of Radiation, lasers are a bit of a misnomer. In truth, nothing is really being amplified. You know that, in normal matter, you have an atomic nucleus and various energy levels for an electron; in molecules, crystals, and other bound structures, the particular separations between an electron’s energy levels dictate which transitions are allow. In a laser, the electrons oscillate between two allowable states, emitting a photon of a very particular energy when they drop from the higher-energy state to the lower one. These oscillations are what produce the light, but for some reason, no one wanted the acronym Light Oscillation by Stimulated Emission of Radiation.

    3
    By ‘pumping’ electrons into an excited state and stimulating them with a photon of the desired wavelength, you can cause the emission of another photon of exactly the same energy and wavelength. This action is how the light for a laser is first created. Wikimedia Commons user V1adis1av.

    If you can produce either multiple atoms-or-molecules in the same excited state and stimulate their spontaneous jump to the ground state, they’ll emit the same energy photon. These transitions are extremely fast (but not infinitely so), and so there is a theoretical limit to how quickly you can make a single atom-or-molecule hop up to the excited state and spontaneously emit a photon. Normally, some type of gas, molecular compound or crystal is used inside a resonant-or-reflective cavity to create a laser, but you can also make one out of free electrons, semiconductors, optical fibers, and, in theory, even positronium.

    4
    The ALICE free-electron laser is an example of an exotic laser that doesn’t rely on conventional atomic or molecular transitions, but still produces narrowly-focused, coherent light. STFC.

    The amount of energy that comes out of a laser is limited by the amount you put in, so the only way to achieve extremely high power in your laser is to shorten the timescale of the emitted laser pulse. You might hear the term petawatt, which is 1015 W, and think this is a tremendous amount of energy. But “petawatts” aren’t energy, but power, which is an energy over a time. A petawatt laser could either be a laser that emits 1015 J of energy (the amount released by about 200 kilotons of TNT) every second, or could just be a laser that emits one joule of energy (the amount released by burning 60 micrograms of sugar) over femtosecond (10-15 second) timescales. In terms of energy, these two scenarios are vastly different, even though their power is the same.

    5
    Amplifiers for the University of Rochester’s OMEGA-EP, lit up by flash lamps, could drive a U.S. high-power laser that works on very short timescales.
    University of Rochester, Laboratory for laser energetics / Eugene Kowaluk.

    The 100 petawatt laser in question hasn’t been built yet, but is rather the next enormous threshold that researchers plan to cross in the 2020s. The hypothesized project is known as the Station of Extreme Light, and is set to be constructed at the Shanghai Superintense Ultrafast Laser Facility in China. An external pump, which is usually light from a different wavelength, excites the electrons in the lasing material, causing the characteristic transition that creates the laser light. The photons then all emege in a tightly packed stream, or a pulse, at a very narrow set of wavelengths. To the surprise of many, the 1 petawatt threshold was crossed way back in 1996; it’s taken nearly two decades to cross the 10 petawatt mark.

    6
    The preamplifiers of the National Ignition Facility are the first step in increasing the energy of laser beams as they make their way toward the target chamber. In 2012, NIF achieved a 0.5 petawatt shot, reaching a peak of 1,000 times more power than the United States uses at any instant in time. Damien Jemison/LLNL.


    LLNL/NIF

    The National Ignition Facility in the United States may be what we first think of when we envision high-powered lasers, but this is a bit of a red herring. This array of 192 lasers, focusing on a single point to compress a hydrogen pellet and ignite nuclear fusion, hovers right around the 1 PW mark, but isn’t the most powerful one around. It has a high amount of energy at over a million joules, but its pulses are, comparatively, very long-duration. To set the power record, you need to deliver the greatest amount of energy in the shortest amount of time.

    The current record-holder, instead, uses a sapphire crystal doped with titanium, pumps hundreds of joules of energy into it, bounces the light back-and-forth until destructive interference cancels out most of the pulse length, and the output is compressed into a single pulse just tens of femtoseconds long. That’s how we can reach output powers in the ballpark of 10 PW.

    7
    Part of a Ti-sapphire laser; the bright red light on the left is the Ti:sapphire crystal; the bright green light is scattered pump light from a mirror.
    Wikimedia Commons user Hankwang.

    In order to go higher — to reach that next order-of-magnitude milestone — we’ll have to either increase the energy we input into the laser, from hundreds of joules to thousands, or decrease the pulse time. The first one is problematic for the materials we presently use. Small titanium-sapphire crystals won’t hold up to that kind of energy, while larger ones tend to emit light in the wrong direction: at right angles to the desired pathway. The three main approaches, therefore, that researchers are considering at the present time are:

    To take the original, 10 PW pulse, stretch it out over a grating, and combine it into an artificial crystal, where you can pump it again, raising its power.
    To combine multiple pulses from a series of different high-powered lasers to create the right level of overlap: a challenge for pulses just tens of femtoseconds (3-15 microns) long that move at the speed of light.
    Or, to add a second round of pulse compression, squeezing them to as little as a couple of femtoseconds.

    8
    Bending light and focusing it to a point, regardless of wavelength or where it’s incident on your surface, is one key step towards maximizing the intensity of your light at a single location in space. M. Khorasaninejad et al., Nano Lett., 2017, 17 (3), pp 1819–1824.

    The pulses must then be brought to a tight focus, raising not just the power, but the intensity, or the power concentrated at a single point. As the Science article states:

    If a 100-PW pulse can be focused to a spot measuring just 3 micrometers across […] the intensity in that tiny area will be an astonishing 1024 watts per square centimeter (W/cm2)—some 25 orders of magnitude, or 10 trillion trillion times, more intense than the sunlight striking Earth.

    This opens the door to a long-sought-after opportunity to create particle-antiparticle pairs where there were none before, but it’s hardly “breaking the quantum vacuum.”

    9
    Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. Even in empty space, this vacuum energy is non-zero.
    Derek Leinweber.

    According to the theory of quantum electrodynamics, the zero-point energy of empty space isn’t zero, but some positive, finite value. Although we visualize it as particles and antiparticles popping in-and-out of existence, a better depiction is to recognize that, with enough energy, you can — through physics — use these electromagnetic properties of empty space to generate real particle/antiparticle pairs [Matter and Radiation at Extremes]. This is based on the simple Einsteinian physics of E = mc2, but requires a strong enough electric field to build those particles: around 1016 volts per meter. Light, since it’s an electromagnetic wave, carries with it both electric and magnetic fields, and will reach that critical threshold with a laser intensity of 1029 W/cm2.

    10
    Zetawatt lasers, reaching an intensity of 10^29 W/cm^2, should be sufficient to create real electron/positron pairs from the quantum vacuum itself. This will require additional energy, shorter pulses, and/or increased focusing over what we even envision for the future. Wikimedia Commons user Slashme.

    You ought to notice, right away, that even the dream scenario of the science article gives intensities that are still 100,000 times too small to reach this threshold, and whenever you’re below that threshold, your ability to produce particle/antiparticle pairs is exponentially suppressed. The mechanism at play is quite different than simply the reverse of pair production, where instead of an electron and positron annihilating to create two photons, two photons interact to produce an electron/positron pair. (That process was first experimentally demonstrated way back in 1997.) In the laser setup, no individual photons have enough energy to produce new particles, but rather their combined effects on the vacuum of space causes particle/antiparticle pairs to pop into existence with a particular probability. Unless, however, those intensities approach that critical 1029 W/cm^2 threshold, that probability might as well be zero.

    11
    A laser in Shanghai, China, has set power records yet fits on tabletops. The most powerful lasers aren’t the most energetic, but are often the ones with the shortest laser pulses. Kan Zhan.

    The ability to generate matter/antimatter pairs of particles from empty space alone will be an important test of quantum electrodynamics, and will also be a remarkable demonstration of the power of lasers and our ability to control them. It may not take reaching that critical threshold to generate the first particle/antiparticle pairs from this mechanism, but you’ll have to either get close, get lucky, or have some sort of mechanism to enhance your production over what you naively expect. In any case, the quantum vacuum never breaks, but rather does exactly what you expect of it: responds to matter and energy in accordance with the laws of physics. It might not be intuitive, but it’s something even more powerful: it’s predictable. The art of doing that prediction and doing the experiments to verify or refute them is what science is all about! We may not be there yet, but every leap upwards in power and intensity is another step closer to this “holy grail” in laser physics.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 2:08 pm on February 1, 2018 Permalink | Reply
    Tags: Laser Technology, Magnetic Trick Triples the Power of SLAC’s X-Ray Laser, , ,   

    From SLAC: “Magnetic Trick Triples the Power of SLAC’s X-Ray Laser” 


    SLAC Lab

    January 31, 2018
    Mark Shwartz

    The new technique will allow researchers to observe ultrafast chemical processes previously undetectable at the atomic scale.

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to triple the amount of power generated by the world’s most powerful X-ray laser. The new technique, developed at SLAC’s Linac Coherent Light Source (LCLS), will enable researchers to observe the atomic structure of molecules and ultrafast chemical processes that were previously undetectable at the atomic scale.

    SLAC/LCLS

    1
    From left, SLAC’s Yauntao Ding and Marc Guetg discuss their work at the lab’s Accelerator Control Room where beams that feed the X-ray laser are monitored.(Dawn Harmer/SLAC)

    The results, published in a Jan. 3 study in Physical Review Letters (PRL), will help address long-standing mysteries about photosynthesis and other fundamental chemical processes in biology, medicine and materials science, according to the researchers.

    “LCLS produces the world’s most powerful X-ray pulses, which scientists use to create movies of atoms and molecules in action,” said Marc Guetg, a research associate at SLAC and lead author of the PRL study. “Our new technique triples the power of these short pulses, enabling higher contrast.”

    2
    The research team, from left: back row, Yuantao Ding, Matt Gibbs, Nora Norvell, Alex Saad, Uwe Bergmann, Zhirong Huang; front row, Marc Guetg and Timothy Maxwell. (Dawn Harmer/SLAC)

    Magnetic Wiggles

    The X-ray pulses at LCLS are generated by feeding beams of high-energy electrons through a long array of magnets. The electrons, which travel near the speed of light, wiggle back and forth as they pass along the magnets. This wiggling motion causes the electrons to emit powerful X-ray pulses that can be used for nanoscale imaging.

    “When you image an atomic structure, you have a race going on,” said study co-author Uwe Bergmann, a distinguished staff scientist at SLAC. “You need an X-ray pulse strong enough to get a good image, but that pulse will destroy the very structure that you’re trying to measure. However, if the pulse is short enough, about 10 femtoseconds, you can outrun the damage. You can take the snapshot before the patient feels the pain.”

    One femtosecond is one millionth of a billionth of a second. Generating high-power X-ray pulses that last only 10 femtoseconds has been a major challenge.

    “The trick is to have the electrons packed together as tightly as possible when they start wiggling around,” Guetg explained. “It’s difficult to do, because electrons don’t like each other. They’re all negatively charged, so they repel one another. It’s a battle. We’re constantly trying to force them to together, and they’re constantly trying to move apart.”

    To win the battle, Guetg and his SLAC colleagues used a special combination of magnets designed to bring the electrons closer together before they start emitting X-rays.

    “One problem when you compress electrons is that they start kicking each other,” Guetg said. “As a result, the electron beam gets tilted, which impairs the light production and therefore the power of the X-ray pulses.”

    In previous studies, Guetg had theorized that correcting the tilt would compress the electrons and produce shorter, more powerful bursts of X-rays.

    “The electron beam is shaped like a banana,” said co-author Zhirong Huang, an associate professor at SLAC and at Stanford University. “We corrected the curvature of the banana to make it a straight, pencil-like beam.”

    Dramatic Results

    The results were dramatic. Straightening the beam increased the power of the X-ray pulses by 300 percent, and each pulse lasted only 10 femtoseconds.

    “In an ingenious way, Marc and his colleagues were able to compress these electrons like a pancake before they drifted apart,” Bergmann said. “That allowed them to create very short X-ray pulses that are about 1,000 times more powerful than if you focused all the sunlight that hits the Earth onto one square centimeter. It’s an incredible power.”

    Bergmann has already used the new technique to create nanoscale images of transition metals such as manganese, which is essential for splitting water to form oxygen molecules (O2) during photosynthesis.

    “By pushing the frontier of laser science we can now see more and hopefully learn more about chemical reactions and molecular processes,” he said.

    The SLAC team hopes to build on their results in future experiments.

    “We want to make the new technique operational and robust so that anyone can use it,” Huang said. “We also want to keep improving the power with this technique and others. I would not call this the final limit.”

    The study is co-authored by SLAC staff scientists Alberto Lutman, Yuantao Ding, Timothy Maxwell and Franz-Josef Decker. Financial support was provided by the Department of Energy’s Office of Science. LCLS is a DOE Office of Science user facility.

    See the full article here .

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

     
  • richardmitnick 3:40 pm on January 24, 2018 Permalink | Reply
    Tags: , Laser Technology, , SULF-Shanghai Superintense Ultrafast Laser Facility   

    From Science: “Physicists are planning to build lasers so powerful they could rip apart empty space” 

    ScienceMag
    Science Magazine

    Jan. 24, 2018
    Edwin Cartlidge

    1
    A laser in Shanghai, China, has set power records yet fits on tabletops.

    Inside a cramped laboratory in Shanghai, China, physicist Ruxin Li and colleagues are breaking records with the most powerful pulses of light the world has ever seen. At the heart of their laser, called the Shanghai Superintense Ultrafast Laser Facility (SULF), is a single cylinder of titanium-doped sapphire about the width of a Frisbee. After kindling light in the crystal and shunting it through a system of lenses and mirrors, the SULF distills it into pulses of mind-boggling power. In 2016, it achieved an unprecedented 5.3 million billion watts, or petawatts (PW). The lights in Shanghai do not dim each time the laser fires, however. Although the pulses are extraordinarily powerful, they are also infinitesimally brief, lasting less than a trillionth of a second. The researchers are now upgrading their laser and hope to beat their own record by the end of this year with a 10-PW shot, which would pack more than 1000 times the power of all the world’s electrical grids combined.

    The group’s ambitions don’t end there. This year, Li and colleagues intend to start building a 100-PW laser known as the Station of Extreme Light (SEL). By 2023, it could be flinging pulses into a chamber 20 meters underground, subjecting targets to extremes of temperature and pressure not normally found on Earth, a boon to astrophysicists and materials scientists alike. The laser could also power demonstrations of a new way to accelerate particles for use in medicine and high-energy physics. But most alluring, Li says, would be showing that light could tear electrons and their antimatter counterparts, positrons, from empty space—a phenomenon known as “breaking the vacuum.” It would be a striking illustration that matter and energy are interchangeable, as Albert Einstein’s famous E=mc2 equation states. Although nuclear weapons attest to the conversion of matter into immense amounts of heat and light, doing the reverse is not so easy. But Li says the SEL is up to the task. “That would be very exciting,” he says. “It would mean you could generate something from nothing.”

    The Chinese group is “definitely leading the way” to 100 PW, says Philip Bucksbaum, an atomic physicist at Stanford University in Palo Alto, California. But there is plenty of competition. In the next few years, 10-PW devices should switch on in Romania and the Czech Republic as part of Europe’s Extreme Light Infrastructure, although the project recently put off its goal of building a 100-PW-scale device. Physicists in Russia have drawn up a design for a 180-PW laser known as the Exawatt Center for Extreme Light Studies (XCELS), while Japanese researchers have put forward proposals for a 30-PW device.

    Largely missing from the fray are U.S. scientists, who have fallen behind in the race to high powers, according to a study published last month by a National Academies of Sciences, Engineering, and Medicine group that was chaired by Bucksbaum. The study calls on the Department of Energy to plan for at least one high-power laser facility, and that gives hope to researchers at the University of Rochester in New York, who are developing plans for a 75-PW laser, the Optical Parametric Amplifier Line (OPAL). It would take advantage of beamlines at OMEGA-EP, one of the country’s most powerful lasers. “The [Academies] report is encouraging,” says Jonathan Zuegel, who heads the OPAL.

    Invented in 1960, lasers use an external “pump,” such as a flash lamp, to excite electrons within the atoms of a lasing material—usually a gas, crystal, or semiconductor. When one of these excited electrons falls back to its original state it emits a photon, which in turn stimulates another electron to emit a photon, and so on. Unlike the spreading beams of a flashlight, the photons in a laser emerge in a tightly packed stream at specific wavelengths.

    Because power equals energy divided by time, there are basically two ways to maximize it: Either boost the energy of your laser, or shorten the duration of its pulses. In the 1970s, researchers at Lawrence Livermore National Laboratory (LLNL) in California focused on the former, boosting laser energy by routing beams through additional lasing crystals made of glass doped with neodymium. Beams above a certain intensity, however, can damage the amplifiers. To avoid this, LLNL had to make the amplifiers ever larger, many tens of centimeters in diameter. But in 1983, Gerard Mourou, now at the École Polytechnique near Paris, and his colleagues made a breakthrough. He realized that a short laser pulse could be stretched in time—thereby making it less intense—by a diffraction grating that spreads the pulse into its component colors. After being safely amplified to higher energies, the light could be recompressed with a second grating. The end result: a more powerful pulse and an intact amplifier.

    This “chirped-pulse amplification” has become a staple of high-power lasers. In 1996, it enabled LLNL researchers to generate the world’s first petawatt pulse with the Nova laser.

    2
    LLNL Nova Laser

    Since then, LLNL has pushed to higher energies in pursuit of laser-driven fusion. The lab’s National Ignition Facility (NIF) creates pulses with a mammoth 1.8 megajoules of energy in an effort to heat tiny capsules of hydrogen to fusion temperatures.


    LLNL/NIF

    However, those pulses are comparatively long and they still generate only about 1 PW of power.

    To get to higher powers, scientists have turned to the time domain: packing the energy of a pulse into ever-shorter durations. One approach is to amplify the light in titanium-doped sapphire crystals, which produce light with a large spread of frequencies. In a mirrored laser chamber, those pulses bounce back and forth, and the individual frequency components can be made to cancel each other out over most of their pulse length, while reinforcing each other in a fleeting pulse just a few tens of femtoseconds long. Pump those pulses with a few hundred joules of energy and you get 10 PW of peak power. That’s how the SULF and other sapphire-based lasers can break power records with equipment that fits in a large room and costs just tens of millions of dollars, whereas NIF costs $3.5 billion and needs a building 10 stories high that covers the area of three U.S. football fields.

    Raising pulse power by another order of magnitude, from 10 PW to 100 PW, will require more wizardry. One approach is to boost the energy of the pulse from hundreds to thousands of joules. But titanium-sapphire lasers struggle to achieve those energies because the big crystals needed for damage-free amplification tend to lase at right angles to the beam—thereby sapping energy from the pulses. So scientists at the SEL, XCELS, and OPAL are pinning their hopes on what are known as optical parametric amplifiers. These take a pulse stretched out by an optical grating and send it into an artificial “nonlinear” crystal, in which the energy of a second, “pump” beam can be channeled into the pulse. Recompressing the resulting high-energy pulse raises its power.

    To approach 100 PW, one option is to combine several such pulses—four 30-PW pulses in the case of the SEL and a dozen 15-PW pulses at the XCELS. But precisely overlapping pulses just tens of femtoseconds long will be “very, very difficult,” says LLNL laser physicist Constantin Haefner. They could be thrown off course by even the smallest vibration or change in temperature, he argues. The OPAL, in contrast, will attempt to generate 75 PW using a single beam.

    Mourou envisions a different route to 100 PW: adding a second round of pulse compression. He proposes using thin plastic films to broaden the spectrum of 10-PW laser pulses, then squeezing the pulses to as little as a couple of femtoseconds to boost their power to about 100 PW.

    Once the laser builders summon the power, another challenge will loom: bringing the beams to a singularly tight focus. Many scientists care more about intensity—the power per unit area—than the total number of petawatts. Achieve a sharper focus, and the intensity goes up. If a 100-PW pulse can be focused to a spot measuring just 3 micrometers across, as Li is planning for the SEL, the intensity in that tiny area will be an astonishing 1024 watts per square centimeter (W/cm2)—some 25 orders of magnitude, or 10 trillion trillion times, more intense than the sunlight striking Earth.

    Those intensities will open the possibility of breaking the vacuum. According to the theory of quantum electrodynamics (QED), which describes how electromagnetic fields interact with matter, the vacuum is not as empty as classical physics would have us believe. Over extremely short time scales, pairs of electrons and positrons, their antimatter counterparts, flicker into existence, born of quantum mechanical uncertainty. Because of their mutual attraction, they annihilate each another almost as soon as they form.

    But a very intense laser could, in principle, separate the particles before they collide. Like any electromagnetic wave, a laser beam contains an electric field that whips back and forth. As the beam’s intensity rises, so, too, does the strength of its electric field. At intensities around 1024 W/cm2, the field would be strong enough to start to break the mutual attraction between some of the electron-positron pairs, says Alexander Sergeev, former director of the Russian Academy of Sciences’s (RAS’s) Institute of Applied Physics (IAP) in Nizhny Novgorod and now president of RAS. The laser field would then shake the particles, causing them to emit electromagnetic waves—in this case, gamma rays. The gamma rays would, in turn, generate new electron-positron pairs, and so on, resulting in an avalanche of particles and radiation that could be detected. “This will be completely new physics,” Sergeev says. He adds that the gamma ray photons would be energetic enough to push atomic nuclei into excited states, ushering in a new branch of physics known as “nuclear photonics”—the use of intense light to control nuclear processes.

    4
    Amplifiers for the University of Rochester’s OMEGA-EP, lit up by flash lamps, could drive a U.S. high-power laser. UNIVERSITY OF ROCHESTER LABORATORY FOR LASER ENERGETICS/EUGENE KOWALUK

    One way to break the vacuum would be to simply focus a single laser beam onto an empty spot inside a vacuum chamber. But colliding two beams makes it easier, because this jacks up the momentum needed to generate the mass for electrons and positrons. The SEL would collide photons indirectly. First, the pulses would eject electrons from a helium gas target. Other photons from the laser beam would ricochet off the electrons and be boosted into high-energy gamma rays. Some of these in turn would collide with optical photons from the beam.

    Documenting these head-on photon collisions would itself be a major scientific achievement. Whereas classical physics insists that two light beams will pass right through each other untouched, some of the earliest predictions of QED stipulate that converging photons occasionally scatter off one another. “The predictions go back to the early 1930s,” says Tom Heinzl, a theoretical physicist at Plymouth University in the United Kingdom. “It would be good if we could confirm them experimentally.”

    Besides making lasers more powerful, researchers also want to make them shoot faster. The flash lamps that pump the initial energy into many lasers must be cooled for minutes or hours between shots, making it hard to carry out research that relies on plenty of data, such as investigating whether, very occasionally, photons transform into particles of the mysterious dark matter thought to make up much of the universe’s mass. “Chances are you would need a lot of shots to see that,” says Manuel Hegelich, a physicist at the University of Texas in Austin.

    A higher repetition rate is also key to using a high-power laser to drive beams of particles. In one scheme, an intense beam would transform a metal target into a plasma, liberating electrons that, in turn, would eject protons from nuclei on the metal’s surface. Doctors could use those proton pulses to destroy cancers—and a higher firing rate would make it easier to administer the treatment in small, individual doses.

    Physicists, for their part, dream of particle accelerators powered by rapid-fire laser pulses. When an intense laser pulse strikes a plasma of electrons and positive ions, it shoves the lighter electrons forward, separating the charges and creating a secondary electric field that pulls the ions along behind the light like water in the wake of a speedboat. This “laser wakefield acceleration” can accelerate charged particles to high energies in the space of a millimeter or two, compared with many meters for conventional accelerators. Electrons thus accelerated could be wiggled by magnets to create a so-called free-electron laser (FEL), which generates exceptionally bright and brief flashes of x-rays that can illuminate short-lived chemical and biological phenomena. A laser-powered FEL could be far more compact and cheaper than those powered by conventional accelerators.

    In the long term, electrons accelerated by high-repetition PW pulses could slash the cost of particle physicists’ dream machine: a 30-kilometer-long electron-positron collider that would be a successor to the Large Hadron Collider at CERN, the European particle physics laboratory near Geneva, Switzerland. A device based on a 100-PW laser could be at least 10 times shorter and cheaper than the roughly $10 billion machine now envisaged, says Stuart Mangles, a plasma physicist at Imperial College London

    Both the linear collider and rapid-fire FELs would need thousands, if not millions, of shots per second, well beyond current technology. One possibility, being investigated by Mourou and colleagues, is to try to combine the output of thousands of quick-firing fiber amplifiers, which don’t need to be pumped with flash tubes. Another option is to replace the flash tubes with diode lasers, which are expensive, but could get cheaper with mass production.

    For the moment, however, Li’s group in China and its U.S. and Russian counterparts are concentrating on power. Efim Khazanov, a laser physicist at IAP, says the XCELS could be up and running by about 2026—assuming the government agrees to the cost: roughly 12 billion rubles (about $200 million). The OPAL, meanwhile, would be a relative bargain at between $50 million and $100 million, Zuegel says.

    But the first laser to rip open the vacuum is likely to be the SEL, in China. An international committee of scientists last July described the laser’s conceptual design as “unambiguous and convincing,” and Li hopes to get government approval for funding—about $100 million—early this year. Li says other countries need not feel left in the shadows as the world’s most powerful laser turns on, because the SEL will operate as an international user facility. Zuegel says he doesn’t “like being second,” but acknowledges that the Chinese group is in a strong position. “China has plenty of bucks,” he says. “And it has a lot of really smart people. It is still catching up on a lot of the technology, but it’s catching up fast.”

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  • richardmitnick 2:08 pm on January 12, 2018 Permalink | Reply
    Tags: Accelerating light beams in curved space, Acceleration, , , Laser Technology, ,   

    From Technion, Harvard and CfA via phys.org: “Accelerating light beams in curved space” 

    Technion bloc

    Technion

    Harvard University

    Harvard University

    Harvard Smithsonian Center for Astrophysics

    Center For Astrophysics

    phys.org

    January 12, 2018
    Lisa Zyga

    1
    The accelerating light beam propagates on a nongeodesic trajectory, rather than the geodesic trajectory taken by a non-accelerating beam. Credit: Patsyk et al. ©2018 American Physical Society

    By shining a laser along the inside shell of an incandescent light bulb, physicists have performed the first experimental demonstration of an accelerating light beam in curved space. Rather than moving along a geodesic trajectory (the shortest path on a curved surface), the accelerating beam bends away from the geodesic trajectory as a result of its acceleration.

    Previously, accelerating light beams have been demonstrated on flat surfaces, on which their acceleration causes them to follow curved trajectories rather than straight lines. Extending accelerating beams to curved surfaces opens the doors to additional possibilities, such as emulating general relativity phenomena (for example, gravitational lensing) with optical devices in the lab.

    The physicists, Anatoly Patsyk, Miguel A. Bandres, and Mordechai Segev at the Technion – Israel Institute of Technology, along with Rivka Bekenstein at Harvard University and the Harvard-Smithsonian Center for Astrophysics, have published a paper on the accelerating light beams in curved space in a recent issue of Physical Review X.

    “This work opens the doors to a new avenue of study in the field of accelerating beams,” Patsyk told Phys.org. “Thus far, accelerating beams were studied only in a medium with a flat geometry, such as flat free space or slab waveguides. In the current work, optical beams follow curved trajectories in a curved medium.”

    In their experiments, the researchers first transformed an ordinary laser beam into an accelerating one by reflecting the laser beam off of a spatial light modulator. As the scientists explain, this imprints a specific wavefront upon the beam. The resulting beam is both accelerating and shape-preserving, meaning it doesn’t spread out as it propagates in a curved medium, like ordinary light beams would do. The accelerating light beam is then launched into the shell of an incandescent light bulb, which was painted to scatter light and make the propagation of the beam visible.

    When moving along the inside of the light bulb, the accelerating beam follows a trajectory that deviates from the geodesic line. For comparison, the researchers also launched a nonaccelerating beam inside the light bulb shell, and observed that that beam follows the geodesic line. By measuring the difference between these two trajectories, the researchers could determine the acceleration of the accelerating beam.

    3
    (a) Experimental setup, (b) propagation of the green beam inside of the red shell of an incandescent light bulb, and (c) photograph of the lobes of the accelerating beam. Credit: Patsyk et al. ©2018 American Physical Society

    Whereas the trajectory of an accelerating beam on a flat surface is determined entirely by the beam width, the new study shows that the trajectory of an accelerating beam on a spherical surface is determined by both the beam width and the curvature of the surface. As a result, an accelerating beam may change its trajectory, as well as periodically focus and defocus, due to the curvature.

    The ability to accelerate light beams along curved surfaces has a variety of potential applications, one of which is emulating general relativity phenomena.

    “Einstein’s equations of general relativity determine, among other issues, the evolution of electromagnetic waves in curved space,” Patsyk said. “It turns out that the evolution of electromagnetic waves in curved space according to Einstein’s equations is equivalent to the propagation of electromagnetic waves in a material medium described by the electric and magnetic susceptibilities that are allowed to vary in space. This is the foundation of emulating numerous phenomena known from general relativity by the electromagnetic waves propagating in a material medium, giving rise to the emulating effects such as gravitational lensing and Einstein’s rings, gravitational blue shift or red shift, which we have studied in the past, and much more.”

    The results could also offer a new technique for controlling nanoparticles in blood vessels, microchannels, and other curved settings. Accelerating plasmonic beams (which are made of plasma oscillations instead of light) could potentially be used to transfer power from one area to another on a curved surface. The researchers plan to further explore these possibilities and others in the future.

    “We are now investigating the propagation of light within the thinnest curved membranes possible—soap bubbles of molecular thickness,” Patsyk said. “We are also studying linear and nonlinear wave phenomena, where the laser beam affects the thickness of the membrane and in return the membrane affects the light beam propagating within it.”

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 10:31 am on January 5, 2018 Permalink | Reply
    Tags: , , Computational astrophysics team uncloaks magnetic fields of cosmic events, Flash Center for Computational Science, Laser Technology, , OMEGA Laser Facility U Rochester, ,   

    From U Chicago: “Computational astrophysics team uncloaks magnetic fields of cosmic events” 

    U Chicago bloc

    University of Chicago

    January 4, 2018
    Rob Mitchum

    New method enhances study of stars, black holes in laboratory settings.

    1
    Computational astrophysicists describe a new method for acquiring information on experiments using laser beams to reproduce cosmic conditions. Courtesy of
    Lawrence Livermore National Laboratory

    The development of ultra-intense lasers delivering the same power as the entire U.S. power grid has enabled the study of cosmic phenomena such as supernovae and black holes in earthbound laboratories. Now, a new method developed by computational astrophysicists at the University of Chicago allows scientists to analyze a key characteristic of these events: their powerful and complex magnetic fields.

    In the field of high-energy density physics, or HEDP, scientists study a wide range of astrophysical objects—stars, supermassive black holes at the center of galaxies and galaxy clusters—with laboratory experiments as small as a penny and lasting only a few billionths of a second. By focusing powerful lasers on a carefully designed target, researchers can produce plasmas that reproduce conditions observed by astronomers in our sun and distant galaxies.

    Planning these complex and expensive experiments requires large-scale, high-fidelity computer simulation beforehand. Since 2012, the Flash Center for Computational Science of the Department of Astronomy & Astrophysics at UChicago has provided the leading open computer code, called FLASH, for these HEDP simulations, enabling researchers to fine-tune experiments and develop analysis methods before execution at sites such as the National Ignition Facility at Lawrence Livermore National Laboratory or the OMEGA Laser Facility in Rochester, N.Y.


    LLNL/NIF

    2
    OMEGA Laser Facility, U Rochester

    “As soon as FLASH became available, there was kind of a stampede to use it to design experiments,” said Petros Tzeferacos, research assistant professor of astronomy and astrophysics and associate director of the Flash Center.

    During these experiments, laser probe beams can provide researchers with information about the density and temperature of the plasma. But a key measurement, the magnetic field, has remained elusive. To try and tease out magnetic field measurements from extreme plasma conditions, scientists at MIT developed an experimental diagnostic technique that uses charged particles instead, called proton radiography.

    In a new paper for the journal Review of Scientific Instruments, Flash Center scientists Carlo Graziani, Donald Lamb and Tzeferacos, with MIT’s Chikang Li, describe a new method for acquiring quantitative, high-resolution information about these magnetic fields. Their discovery, refined using FLASH simulations and real experimental results, opens new doors for understanding cosmic phenomena.

    “We chose to go after experiments motivated by astrophysics where magnetic fields were important,” said Lamb, the Robert A. Millikan Distinguished Service Professor Emeritus in Astronomy & Astrophysics and director of the Flash Center. “The creation of the code plus the need to try to figure out how to understand what magnetic fields are created caused us to build this software, that can for the first time quantitatively reconstruct the shape and strength of the magnetic field.”

    Skyrocketing experiments

    In proton radiography, energetic protons are shot through the magnetized plasma towards a detector on the other side. As the protons pass through the magnetic field, they are deflected from their path, forming a complex pattern on the detector. These patterns were difficult to interpret, and previous methods could only make general statements about the field’s properties.

    “Magnetic fields play important roles in essentially almost every astrophysical phenomena. If you aren’t able to actually look at what’s happening, or study them, you’re missing a key part of almost every astrophysical object or process that you’re interested in,” said Tzeferacos.

    By conducting simulated experiments with known magnetic fields, the Flash Center team constructed an algorithm that can reconstruct the field from the proton radiograph pattern. Once calibrated computationally, the method was applied to experimental data collected at laser facilities, revealing new insights about astrophysical events.

    The combination of the FLASH code, the development of the proton radiography diagnostic, and the ability to reconstruct magnetic fields from the experimental data, are revolutionizing laboratory plasma astrophysics and HEDP. “The availability of these tools has caused the number of HEDP experiments that study magnetic fields to skyrocket,” said Lamb.

    The new software for magnetic field reconstruction, called PRaLine, will be shared with the community both as part of the next FLASH code release and as a separate component available on GitHub. Lamb and Tzeferacos said they expect it to be used for studying many astrophysics topics, such as the annihilation of magnetic fields in the solar corona; astrophysical jets produced by young stellar objects, the Crab Nebula pulsar, and the supermassive black holes at the center of galaxies; and the amplification of magnetic fields and acceleration of cosmic rays by shocks in supernova remnants.

    “The types of experiments HEDP scientists perform now are very diverse,” said Tzeferacos. “FLASH contributed to this diversity, because it enables you to think outside the box, try different simulations of different configurations, and see what plasma conditions you are able to achieve.”

    The work was funded by grants from the U.S. Department of Energy and the National Science Foundation.

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  • richardmitnick 2:51 pm on January 2, 2018 Permalink | Reply
    Tags: , England to be mapped with 3D LiDAR scanners to tackle flooding, , Israeli scientists develop world’s first formation flying nano satellites, Laser Technology, , Venus- the Israeli minisatellite   

    From Geospatial World: “Israeli scientists develop world’s first formation flying nano satellites and England to be mapped with 3D LiDAR and more” 

    Geospatial World

    2.2.18
    No writer credit found

    Israeli scientists develop world’s first formation flying nano satellites.

    1
    Venus, the Israeli minisatellite. Image Courtesy: Israeli Space Agency
    A cluster of three nano-satellites developed by scientists at Technion-Israel Institute of Technology, Haifa, will be the world’s first to be flown in formation.

    The project, developed with the collaboration of the French Adelis-Samson Foundation and the Israeli Space Agency (ISA), will be launched on the Indian launcher PSLV at the end of 2018 by the Dutch company Innovative Solutions In Space, which has a specialization in launching Nano-satellites.

    The project has been developed by a team of researchers lead by Prof. Pini Gurfil, who is the head of the Asher Institute for Space Research and a member of the aerospace engineering faculty at the Technion. It has been designed to demonstrate that a combination of satellites can hold together in a controlled formation for a year some 600 kilometers above Earth.

    “Israeli technology is breaking boundaries and proving its innovation again and again,” said Science and Technology Minister Ofir Akunis to The Jerusalem Post. “We are proud to be part of this flagship project, which is a significant contribution to the advancement of space in Israel and to the training of students in the field.”

    The satellites will be used to receive signals from Earth and compute the precise location of the source of the broadcast for rescue, detection, remote sensing and environmental monitoring.

    Each of the satellites is 10 cm. x 20 cm. x 30 cm. – approximately the size of a shoebox – and weighs about eight kg. They will be equipped with measuring devices, antennas, computer and control systems and navigation devices.

    The software and algorithms that will control the flight were developed in a laboratory for distributed space systems at the Technion.

    “Miniaturization in the field of satellites, together with advanced Israeli technology, allows us to take Israel an important step forward with mini-satellites,” added Gurfil. “The degree of innovation of nano-satellites can be compared to switching from a PC to a mobile phone, which offers far more capabilities than its predecessors.”

    “The field of nanosciences has been increasing significantly in recent years and the number of launches doubles every year,” said Israeli Space Agency director Avi Blasberger. “The development and launch costs of such satellites, capable of filling a variety of uses, are significantly lower than those of conventional satellites… In the near future, networks are expected to include thousands of nano-satellites that will cover the Earth and enable high-speed Internet communications at a significantly lower cost than today.”

    England to be mapped with 3D LiDAR scanners to tackle flooding

    Planning to tackle flooding, and track illegal waste dumps in England, LiDAR mapping will be conducted in all of England, announced Environment Agency. Aircraft equipped with laser scanners will map all 130,000 square kilometers (50,000 square miles) of the country in 3D, including rivers, fields and national parks, by 2020.

    Lidar (also called LIDAR, LiDAR, and LADAR) is a surveying method that measures distance to a target by illuminating that target with a pulsed laser light, and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3D-representations of the target. The name lidar, sometimes considered an acronym of Light Detection And Ranging[1] (sometimes Light Imaging, Detection, And Ranging), was originally a portmanteau of light and radar.[2][3]

    Lidar is commonly used to make high-resolution maps, with applications in geodesy, geomatics, archaeology, geography, geology, geomorphology, seismology, forestry, atmospheric physics,[4] laser guidance, airborne laser swath mapping (ALSM), and laser altimetry. The technology is also used for control and navigation for some autonomous cars. Lidar sometimes is called laser scanning and 3D scanning, with terrestrial, airborne, and mobile applications.

    The data gathered will be used to understand flooding risk and plan flood defenses, and will also be made available for free for the public and industry including archaeologists, urban planners and even gamers. Around 75% of the country is already mapped, but there is only sporadic coverage of upland areas and the new project, beginning over winter, will fill in the gaps.

    The new data will be better quality than ever before, the Environment Agency said, with the whole country mapped at a one meter resolution using the most up-to-date laser technology to reveal the terrain more clearly. The LiDAR will be used to detect sudden landscape changes which could indicate illegal tips.

    Other government agencies can use it to help improve the environment. For example, Natural England assesses wildlife habitat while the Forestry Commission can learn more about tree cover. And it can reveal hidden secrets of the country’s past, with archaeologists using it to uncover lost Roman roads in northern England.

    Environment Agency chief executive Sir James Bevan said: “This ambitious project will enhance our understanding of England’s unique natural features and landscape, helping us to better understand flood risk, plan effective defenses and fight waste crime.

    “I’m pleased we are able to gather, use and share such valuable data to contribute to environmental improvements and conservation. It’s just one of the many ways the Environment Agency is using technology to help people and wildlife.”

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  • richardmitnick 3:35 pm on December 28, 2017 Permalink | Reply
    Tags: Femtosecond X-ray lasers, Inelastic X-ray scattering, Laser Technology, , , , , ,   

    From Optics & Photonics: “X-Ray Studies Probe Water’s Elusive Properties” 

    Optics & Photonics

    28 December 2017
    Stewart Wills

    1
    Unlike most substances, liquid water is denser than its solid phase, ice. [Image: Stockholm University]

    In two different X-ray investigations, researchers have dug into some of the exotic properties of that most familiar of substances—water.

    In one study, researchers from Sweden, Japan and South Korea used a femtosecond X-ray laser to investigate the behavior of evaporatively supercooled liquid water, and to confirm the long-suspected view that water at low temperatures can exist in two different liquid phases (Science). In the other, a U.S.-Japanese team used high-resolution inelastic X-ray scattering to probe the dynamics of water molecules and how the liquid’s hydrogen bonds contribute to its unusual characteristics (Science Advances).

    Burst pipes and floating cubes

    Anyone who has confronted a burst water pipe on a frozen winter morning has firsthand knowledge of one of H20’s unusual characteristics. Whereas most substances increase in density as they go from a liquid to a solid state, water reaches its maximum density at 4°C, above its nominal freezing point of 0°C. That’s also the reason that the ice cubes float at the top of your water glass rather than sinking to the bottom.

    Grappling with this anomalous behavior, a research team at Boston University suggested around 25 years ago, based on computer simulations, that in a metastable, supercooled state, water might actually coexist in two liquid phases—a low-density liquid and a high-density liquid. Those two phases, the researchers proposed, merged into a single phase at a critical point in water phase diagram at around –44°C (analogous to the better-known critical point at a higher temperature between water’s liquid and gas phases).

    3
    Experiments using femtosecond X-ray free-electron lasers illuminated fluctuations between two different phases of liquid water—a high-density liquid (red) and a low-density liquid (blue)—as a function of temperature in the supercooled regime. [Image: Stockholm University]

    Actually getting liquid water to that frigid point has, however, seemed a bit of a pipe dream. While very pure liquid water can be rapidly supercooled to temperatures moderately below 0°C relatively easily, the proposed critical point lies far below that temperature range, in what researchers have dubbed a “no-man’s land” in which ice crystalizes much faster than the timescale of conventional lab measurements.

    Leveraging ultrafast lasers

    To move past that barrier, a research team led by Anders Nilsson of Stockholm University, Sweden, turned to the rapid timescales enabled by femtosecond X-ray free-electron lasers (XFELs). At XFEL facilities in Korea and Japan [un-named], the team sent a stream of tiny water droplets (approximately 14 microns in diameter) into a vacuum chamber, and fired the XFEL at the droplets at varying distances from the water-dispensing nozzle to obtain ultrafast X-ray scattering data.

    The tiny size of the droplets meant that as they traveled through the vacuum they rapidly evaporatively cooled—with the amount of cooling related to the time they spent in vacuum under a well-established formula. Thus, by taking X-ray measurements at varying distances from the nozzle, the researchers could examine the structural behavior of the liquid water at multiple temperatures in the deep-supercooling regime, near the hypothesized critical point. “We were able to X-ray unimaginably fast before the ice froze,” Nilsson said in a press release, “and could observe how it fluctuated” between the two hypothesized metastable phases of liquid water.

    The experiments allowed the team to flesh out the phase diagram of liquid water in a supercooled region previously thought to be inaccessible to experiment. And the researchers believe that the use of femtosecond XFELs to probe thermodynamic functions and structural changes at extreme states “can be generalized to many supercooled liquids.”

    Illuminating water’s dynamics

    4
    A team led by scientists at the U.S. Oak Ridge National Laboratory used inelastic X-ray scattering to visualize and quantify the movement of water molecules in space and time. [Image: Jason Richards/Oak Ridge National Laboratory, US Dept. of Energy]

    A second set of experiments, from researchers at the U.S. Oak Ridge National Laboratory, the University of Tennessee, and the SPring-8 synchrotron laboratory in Japan, looked at water’s dynamics at room temperature, using inelastic X-ray scattering (IXS).

    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    The researchers illuminated these dynamics through a series of experiments in which they trained radiation from the SPring-8 facility’s high-resolution IXS beamline, BL35XU, onto a 2-mm-thick sample of liquid water. Through multiple scattering measurements across a range of momentum and energy-transfer values, the team was able to build a detailed picture of the so-called Van Hove function, which describes the probability of interactions between a molecule and its nearest neighbors as a function of distance and time.

    The team found that water’s hydrogen bonds behave in a highly correlated fashion with respect to one another, which gives liquid water its high stability and explains its viscosity characteristics. And, in a press release, the researchers further speculated that the techniques used here could be extended to studying the dynamics and viscosity of a variety of other liquids. Some of those studies, they suggested, could prove useful in “the development of new types of semiconductor devices with liquid electrolyte insulating layers, better batteries and improved lubricants.”

    Here, the research team was interested in sussing out how water molecules interact in real time, and how the strongly directional hydrogen bonds of water molecules work together to determine properties such the liquid’s viscosity.

    See the full article here .

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    Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics. We welcome your submissions.

     
  • richardmitnick 6:29 pm on December 26, 2017 Permalink | Reply
    Tags: A shoe-box-sized chemical detector, , , Laser Technology,   

    From U Michigan: “A shoe-box-sized chemical detector” 

    U Michigan bloc

    University of Michigan

    December 21, 2017
    Nicole Casal Moore

    Powered by a broadband infrared laser, the device can zero in on the ‘spectral fingerprint region’.

    1
    Mohammed Islam, professor of Electrical Engineering and Computer Science and Biomedical Engineering, demonstrates use of a chemical sensor prototype. Photo: Joseph Xu

    A chemical sensor prototype developed at the University of Michigan will be able to detect “single-fingerprint quantities” of substances from a distance of more than 100 feet away, and its developers are working to shrink it to the size of a shoebox.

    It could potentially be used to identify traces of drugs and explosives, as well as speeding the analysis of certain medical samples. A portable infrared chemical sensor could be mounted on a drone or carried by users such as doctors, police, border officials and soldiers.

    The sensor is made possible by a new optical-fiber-based laser that combines high power with a beam that covers a broad band of infrared frequencies—from 1.6 to 12 microns, which covers the so-called mid-wave and long-wave infrared.

    __________________________________________________________
    We’ve shown we can make a $10,000 laser that can do everything a $60,000 laser can do.
    -Mohammed Islam
    __________________________________________________________

    “Most chemicals have fingerprint signatures between about 2 and 11 microns,” said Mohammed Islam, a professor of electrical and computer engineering at U-M who developed the laser. “Hence, this wavelength range is called the ‘spectral fingerprint region.’ So our device enables identification of solid, liquid and gas targets based on their chemical signature.”

    The project is a collaboration among the global technology company Leidos, fiber makers IRflex and CorActive, the University of Michigan and the U-M startup Omni Sciences, which was founded by Islam. The project is funded by the U.S. Intelligence Advanced Research Projects Activity (IARPA).

    3
    The sensor is able to detect a variety of qualities from a distance of more than 100 feet away and could be used to identify traces of drugs and explosives, as well as speeding the analysis of certain medical samples. Previously such a sensor was only able to be used in closed proximity. Photo: Joseph Xu

    Islam and his team built their device with off-the-shelf fiber optics and telecommunications components, save one custom-made optical fiber. This approach ensures that the laser will be reliable and practical to manufacture at a reasonable cost. “We’ve shown we can make a $10,000 laser that can do everything a $60,000 laser can do,” Islam said.

    Broadband infrared lasers are typically built up from a laser that produces very short pulses of light, and then a series of amplifiers ramps up the power, but this approach is limited to laboratories. In addition to their high costs, these components can’t yet shrink small enough to fit into a handheld device. Plus, the use of lenses and mirrors would make the device sensitive to jostling and changes in temperature.

    To craft their new laser, the team started with a standard laser diode, similar to those in laser pointers and barcode scanners. This pulse was then boosted in power with telecom amplifiers—similar to those used in the field to periodically ramp voice signals back up as they diminish over long travels through the fiber-optic lines. Then they ran this powerful, broadband signal through a 2-meter coil of optical fiber.

    “This where the magic comes in,” said Islam. “We put in these roughly one-nanosecond pulses, at this high power, and they break up into very narrow series of small short pulses, typically less than a picosecond in width. So basically for the price of 20 cents of fiber, we obtain the same kind of output as very expensive mode-locked lasers.”

    Then, in a process known as “super-continuum generation,” they expanded the wavelengths covered by that light by sending it through specialized softer glass fibers. Most lasers emit light of just one wavelength, or color. But super-continuum lasers give off a focused beam packed with light from a much broader range of wavelengths. Visible-wavelength super-continuum lasers, for example, discharge tight columns that appear white because they contain light from across the visible spectrum. Islam’s broadband infrared super-continuum laser does the equivalent, but in longer infrared wavelengths.

    4
    Fibers that are constructed together in order for a light to be shot through by a chemical sensor prototype developed by EECS Professor Mohammed Islam’s research group. Photo: Joseph Xu

    To use the device, the researchers shine the laser on an object and analyze the reflected light to identify what wavelengths did not bounce back. They can identify chemicals by the unique pattern of infrared wavelengths that they absorb.

    The team successfully demonstrated the laser for IARPA in August 2017, analyzing 70 mystery samples over two days of testing. Phase 2 of the project will entail shrinking the system toward the size of a shoebox, a process that will be led by Leidos and Omni Sciences.

    In addition to the applications in policing and defense, Islam sees a future for the technology in medicine. For instance, tissue samples are chemically analyzed in a laboratory—a process that takes time and materials. Islam thinks the laser could provide an assessment of the chemical content on the spot. It may even be possible to run the beam through a scope and analyze tissue right in the body.

    The laser is described in the journal Optics Letters, in an article titled, Mid-infrared supercontinuum generation from 1.6 to >11 micrometers using concatenated step-index fluoride and chalcogenide fibers. Islam is also a professor of biomedical engineering.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U MIchigan Campus

    The University of Michigan (U-M, UM, UMich, or U of M), frequently referred to simply as Michigan, is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities.

    Considered one of the foremost research universities in the United States,[7] the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

     
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