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  • richardmitnick 5:46 pm on June 20, 2017 Permalink | Reply
    Tags: , , , SLAC LCLS-II, Superconducting undulators, ,   

    From LBNL: “R&D Effort Produces Magnetic Devices to Enable More Powerful X-ray Lasers” 

    Berkeley Logo

    Berkeley Lab

    June 20, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Berkeley Lab demonstrates a record-setting magnetic field for a prototype superconducting undulator.

    1
    This Berkeley Lab-developed device, a niobium tin superconducting undulator prototype, set a record in magnetic field strength for a device of its kind. This type of undulator could be used to wiggle electron beams to emit light for a next generation of X-ray lasers.
    (Credit: Marilyn Chung/Berkeley Lab)

    Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory have collaborated to design, build, and test two devices, called superconducting undulators, which could make X-ray free-electron lasers (FELs) more powerful, versatile, compact, and durable.

    X-ray FELs are powerful tools for studying the microscopic structure and other properties of samples, such as proteins that are key to drug design, exotic materials relevant to electronics and energy applications, and chemistry that is central to industrial processes like fuel production.

    The recent development effort was motivated by SLAC National Accelerator Laboratory’s upgrade of its Linac Coherent Light Source (LCLS), the nation’s only X-ray FEL.

    SLAC LCLS-II

    This upgrade, now underway, is known as LCLS-II. All existing X-ray FELS, including both LCLS and LCLS-II, use permanent magnet undulators to generate intense pulses of X-rays. These devices produce X-ray light by passing high-energy bunches of electrons through alternating magnetic fields produced by a series of permanent magnets.

    Superconducting undulators (SCUs) offer another technical solution and are considered among the most promising technologies to improve the performance of the next generation FELs, and of other types of light sources, such as Berkeley Lab’s Advanced Light Source (ALS) and Argonne’s Advanced Photon Source (APS).

    LBNL/ALS

    ANL APS

    SCUs replace the permanent magnets in the undulator with superconducting coils. The prototype SCUs have successfully produced stronger magnetic fields than conventional undulators of the same size. Higher fields, in turn, can produce higher-energy free-electron laser light to open up a broader range of experiments.

    Berkeley Lab’s 1.5-meter-long prototype undulator, which uses a superconducting material known as niobium-tin (Nb3Sn), set a record in magnetic field strength for a device of its design during testing at the Lab in September 2016.

    “This is a much-anticipated innovation,” agreed Wim Leemans, Director, Accelerator Technology and Applied Physics (ATAP) . “Higher performance in a smaller footprint is something that benefits everyone – the laboratories that host the facilities, the funding agencies, and above all, the user community.”

    Argonne’s test of another superconducting material, niobium-titanium, successfully reached its performance goal, and additionally passed a bevy of quality tests. Niobium-titanium has a lower maximum magnetic field strength than niobium-tin, but is further along in its development.

    3
    The superconducting undulator R&D project at Berkeley Lab was a team effort. Among the contributors: (from left) Heng Pan, Jordan Taylor, Soren Prestemon, Ross Schlueter, Diego Arbelaez, Jim Swanson, Ahmet Pekedis, Scott Myers, Tom Lipton, and Xiaorong Wang. (Credit: Marilyn Chung/Berkeley Lab)

    Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory have collaborated to design, build, and test two devices, called superconducting undulators, which could make X-ray free-electron lasers (FELs) more powerful, versatile, compact, and durable.

    X-ray FELs are powerful tools for studying the microscopic structure and other properties of samples, such as proteins that are key to drug design, exotic materials relevant to electronics and energy applications, and chemistry that is central to industrial processes like fuel production.

    The recent development effort was motivated by SLAC National Accelerator Laboratory’s upgrade of its Linac Coherent Light Source (LCLS), the nation’s only X-ray FEL. This upgrade, now underway, is known as LCLS-II. All existing X-ray FELS, including both LCLS and LCLS-II, use permanent magnet undulators to generate intense pulses of X-rays. These devices produce X-ray light by passing high-energy bunches of electrons through alternating magnetic fields produced by a series of permanent magnets.

    Superconducting undulators (SCUs) offer another technical solution and are considered among the most promising technologies to improve the performance of the next generation FELs, and of other types of light sources, such as Berkeley Lab’s Advanced Light Source (ALS) and Argonne’s Advanced Photon Source (APS).

    SCUs replace the permanent magnets in the undulator with superconducting coils. The prototype SCUs have successfully produced stronger magnetic fields than conventional undulators of the same size. Higher fields, in turn, can produce higher-energy free-electron laser light to open up a broader range of experiments.

    Berkeley Lab’s 1.5-meter-long prototype undulator, which uses a superconducting material known as niobium-tin (Nb3Sn), set a record in magnetic field strength for a device of its design during testing at the Lab in September 2016.

    “This is a much-anticipated innovation,” agreed Wim Leemans, Director, Accelerator Technology and Applied Physics (ATAP) . “Higher performance in a smaller footprint is something that benefits everyone – the laboratories that host the facilities, the funding agencies, and above all, the user community.”

    Argonne’s test of another superconducting material, niobium-titanium, successfully reached its performance goal, and additionally passed a bevy of quality tests. Niobium-titanium has a lower maximum magnetic field strength than niobium-tin, but is further along in its development.
    Photo – The superconducting undulator R&D project at Berkeley Lab was a team effort. Among the contributors: (from left) Heng Pan, Jordan Taylor, Soren Prestemon, Ross Schlueter, Diego Arbelaez, Jim Swanson, Ahmet Pekedis, Scott Myers, Tom Lipton, and Xiaorong Wang. (Credit: Marilyn Chung/Berkeley Lab)

    The superconducting undulator R&D project at Berkeley Lab was a team effort. Among the contributors: (from left) Heng Pan, Jordan Taylor, Soren Prestemon, Ross Schlueter, Diego Arbelaez, Jim Swanson, Ahmet Pekedis, Scott Myers, Tom Lipton, and Xiaorong Wang. (Credit: Marilyn Chung/Berkeley Lab)

    “The superconducting technology in general, and especially with the niobium tin, lived up to its promise of being the highest performer,” said Ross Schlueter, Head of the Magnetics Department in Berkeley Lab’s Engineering Division. “We’re very excited about this world record. This device allows you to get a much higher photon energy” from a given electron beam energy.

    “We have expertise here both in free-electron laser undulators, as demonstrated in our role in leading the construction of LCLS-II’s undulators, and in synchrotron undulator development at the ALS,” noted Soren Prestemon, Director of the Berkeley Center for Magnet Technology (BCMT), which brings together the Accelerator Technology and Applied Physics Division (ATAP) and Engineering Division, to design and build a range of magnetic devices for scientific, medical, and other applications.

    “The Engineering Division has a long history of forefront research on undulators, and this work continues that tradition,” states Henrik von der Lippe, Director, Engineering Division.

    Diego Arbelaez, the lead engineer in the development of Berkeley Lab’s device, said earlier work at the Lab in building superconducting undulator prototypes for a different project were useful in informing the latest design, though there were still plenty of challenges.

    Niobium-tin is a brittle material that cannot be drawn into a wire. For practical use, a pliable wire, which contains the components that will form niobium-tin when heat-treated, is used for winding the undulator coils. The full undulator coil is then heat-treated in a furnace at 1,200 degrees Fahrenheit.

    The niobium-tin wire is wound around a steel frame to form tightly wrapped coils in an alternating arrangement. The precision of the winding is critical for the performance of the device. Arbelaez said, “One of the questions was whether you can maintain precision in its winding even though you are going through these large temperature variations.”

    After the heat treatment, the coils are placed in a mold and impregnated with epoxy to hold the superconducting coils in place. To achieve a superconducting state and demonstrate its record-setting performance, the device was immersed in a bath of liquid helium to cool it down to about minus 450 degrees Fahrenheit.

    4
    Ahmet Pekedis, left, and Diego Arbelaez inspect the completed niobium tin undulator prototype. (Credit: Marilyn Chung/Berkeley Lab)

    Another challenge was in developing a fast shutoff to prevent catastrophic failure during an event known as “quenching.” During a quench, there is a sudden loss of superconductivity that can be caused by a small amount of heat generation. Uncontrolled quenching could lead to rapid heating that might damage the niobium-tin and surrounding copper and ruin the device.

    This is a critical issue for the niobium-tin undulators due to the extraordinary current densities they can support. Berkeley Lab’s Marcos Turqueti led the effort to engineer a quench-protection system that can detect the occurrence of quenching within a couple thousandths of a second and shut down its effects within 10 thousandths of a second.

    Arbelaez also helped devise a system to correct for magnetic-field errors while the undulator is in its superconducting state.

    SLAC’s Paul Emma, the accelerator physics lead for LCLS-II, coordinated the superconducting undulator development effort.

    Emma said that the niobium-tin superconducting undulator developed at Berkeley Lab shows potential but may require more extensive continuing R&D than Argonne’s niobium-titanium prototype. Argonne earlier developed superconducting undulators that are in use at its APS, and Berkeley Lab also hopes to add superconducting undulators at its ALS.

    “With superconducting undulators,” Emma said, “you don’t necessarily lower the cost but you get better performance for the same stretch of undulator.”

    5
    A close-up view of the superconducting undulator prototype developed at Berkeley Lab. To construct the undulator, researchers wound a pliable wire in alternating coils around a steel frame. The pliable wire was baked to form a niobium-tin compound that is very brittle but can achieve high magnetic fields when chilled to superconducting temperatures. (Credit: Marilyn Chung/Berkeley Lab)

    A superconducting undulator of an equivalent length to a permanent magnetic undulator could produce light that is at least two to three times – perhaps up to 10 times – more powerful, and could also access a wider range in X-ray wavelengths, Emma said, producing a more efficient FEL.

    Superconducting undulators also have no macroscopic moving parts, so they could conceivably be tuned more quickly with high precision. Superconductors also are far less prone to damage by high-intensity radiation than permanent-magnet materials, a significant issue in high-power accelerators such as those that will be installed for LCLS-II.

    There appears to be a clear path forward to developing superconducting undulators for upgrades of existing and new X-ray free-electron lasers, Emma said, and for other types of light sources.

    “Superconducting undulators will be the technology we go to eventually, whether it’s in the next 10 or 20 years,” he said. “They are powerful enough to produce the light we are going to need – I think it’s going to happen. People know it’s a big enough step, and we’ve got to get there.”

    James Symons, Berkeley Lab’s Associate Director for Physical Sciences, said, “We look forward to building on this effort by furthering our R&D on superconducting undulator systems.

    The Advanced Light Source, Advanced Photon Source, and Linac Coherent Light Source are DOE Office of Science User Facilities. The development of the superconducting undulator prototypes was supported by the DOE’s Office of Science.”

    See the full article here .

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  • richardmitnick 2:11 pm on April 27, 2017 Permalink | Reply
    Tags: Also involved in LCLS II are FNAL JLab and ANL, , LBNL contribution, , SLAC LCLS-II,   

    From LBNL: “Special Delivery: First Shipment of Magnetic Devices for Next-Gen X-Ray Laser” 

    Berkeley Logo

    Berkeley Lab

    April 27, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Berkeley Lab is overseeing development of specialized undulators that will produce X-ray light at LCLS-II by wiggling electrons

    1

    2
    The first two undulator segments—devices that will be used to produce X-ray laser beams for a project known as LCLS-II—arrived at SLAC National Accelerator Laboratory in Menlo Park, Calif., on Wednesday. (Credit: SLAC National Accelerator Laboratory)

    The first shipment of powerful magnetic devices for a next-generation laser project arrived at SLAC National Accelerator Laboratory on Wednesday after a nearly 3,000-mile journey from a factory in New York to California in a customized delivery truck.

    The Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is overseeing the development and delivery of these devices, known as soft X-ray undulators. They are a key part of LCLS-II, a free-electron laser being built for SLAC by a partnership of SLAC and four other DOE national laboratories: Berkeley Lab, Fermilab, Jefferson Lab, and Argonne.

    The two devices that arrived this week to LCLS-II are the first of what will ultimately be a chain of 21 segments making up the complete soft X-ray undulator. They are at the heart of the free-electron laser, as they will cause the high-energy electron beam from a linear accelerator to emit laserlike beams of X-rays.

    The soft X-ray undulator units present an impressive combination of brute strength and fine precision. Each weighs about 6.5 tons and is about 11 feet long, with sturdy steel frames that are designed to withstand nearly 7 tons of force to keep the two rows of magnets precisely positioned as they try to repel each other. The distance between the rows can be adjusted within millionths of an inch to tune the properties of the X-ray laser light.

    3
    Workers at KTC, a company in Buffalo, N.Y., prepare the first powerful magnetic devices known as soft X-ray undulator segments for the cross-country journey to SLAC National Accelerator Laboratory in Menlo Park, Calif. Berkeley Lab is overseeing the development and delivery of these segments for use in the LCLS-II project, an upgrade to SLAC’s X-ray laser. (Credit: Keller Technology Corp./KTC)

    LCLS-II is a major new facility and upgrade to the existing Linac Coherent Light Source [LCLS], a DOE Office of Science User Facility enabling higher performance, new capabilities, and higher capacity for new experiments.

    SLAC/LCLS

    In particular, LCLS-II will provide a continual stream of X-ray pulses that will enable studies at the atomic, molecular, and nano scales, with femtosecond (quadrillionths-of-a-second) time resolution. This knowledge is eagerly sought in fields ranging from biology to materials science.

    SLAC/LCLS II schematic

    “The delivery is ahead of schedule and below the baseline budget,” said John Corlett, a physicist who is Berkeley Lab’s senior team leader in the LCLS-II project collaboration.

    4
    A prototype LCLS-II soft X-ray undulator, which is designed to wiggle electrons, causing them to emit brilliant X-ray light, undergoes magnetic measurements at Berkeley Lab. (Credit: Roy Kaltschmidt/Berkeley Lab)

    Corlett added, “This is a major achievement—the culmination of years of work in designing the undulator, qualifying the design, and working with vendors.”

    Berkeley Lab is also overseeing the final design and mass production of a set of 32 hard X-ray undulator segments, The Lab collaborated with Argonne National Laboratory in the design and development of these segments. (“Hard” refers to higher-energy X-rays, and “soft” refers to lower-energy X-rays.) Undulators using permanent magnets were first used for storage ring light sources and are now in use for free-electron lasers. The late Klaus Halbach of Berkeley Lab was a pioneer in developing the permanent-magnet array used in these devices.

    Berkeley Lab is also fabricating a unique electron “gun” that kick-starts the rapid-fire electron bunches needed to produce intense electron beams for LCLS-II. The new gun is derived from the Advanced Photoinjector Experiment (APEX) gun, which was successfully developed at Berkeley Lab and is now being used for ultrafast electron experiments.

    6
    The APEX electron gun and test beamline at the Advanced Light Source’s Beam Test Facility.

    As the electron beams go through the undulators, the alternating magnetic fields inside will cause electrons to wiggle, giving off some of their energy in the form of light. As the beam goes through the long chain of undulator segments, each precisely spaced field adds to its intensity.

    The soft X-ray undulator will be capable of producing up to 1 million soft X-ray pulses per second, and the hard X-ray chain can produce X-ray laser pulses that are up to 10,000 times brighter, on average, than those of the existing LCLS.

    “Tremendous effort has gone into the design and development of these undulators at Berkeley Lab and across the project collaboration,” said James Symons, associate laboratory director of Physical Sciences at Berkeley Lab. He oversees both the Engineering and the Accelerator Technology and Applied Physics divisions, which worked together to design and prototype the undulators. “We, and the X-ray user community, are looking forward to their installation and to ‘first light’ at LCLS-II.”

    Wim Leemans, director of Berkeley Lab’s Accelerator Technology and Applied Physics Division, added, “It’s exciting to see the undulators move from the drawing board to the delivery truck after all those years of work. We are glad to contribute our expertise to this realization of a unique new tool for science.”

    Berkeley Lab engineer Matthaeus Leitner has key technical and budgetary responsibility for the undulators, while his colleague Steve Virostek plays the same role for the injector system. Other Berkeley Lab contributions to LCLS-II include accelerator physics and technology studies in beam dynamics, free-electron laser design, the low-level radiofrequency system, and the management and integration of cryogenics systems.

    John Galayda of SLAC, director of the LCLS-II project team, said, “The LBNL team’s performance has been crucial to the LCLS-II project’s good progress to date.”


    This movie introduces LCLS-II, a future X-ray light source. It will generate over 8,000 times more light pulses per second than today’s most powerful X-ray laser, LCLS, and produce an almost continuous X-ray beam. (Credit: SLAC National Accelerator Laboratory)

    The soft X-ray undulator shipments will continue every six weeks to SLAC from their assembly at a vendor in Buffalo, N.Y. The shipments will wrap up in spring 2018. To prevent damage and misalignment during their coast-to-coast journey, the undulator segments are being shipped in a climate-controlled truck that includes a special shock-absorbing frame.

    Once delivered to SLAC, the undulator segments must be fine-tuned. “The undulators have been specially designed to allow for very rapid tuning,” said Henrik von der Lippe, Berkeley Lab’s Engineering Division director. “The process will require as little as two days, compared to the two weeks or more needed by earlier undulators.”

    Now that the soft-X-ray undulator segments are in production, engineers are now conducting magnetic tests on a pre-production version of a hard X-ray undulator segment. These segments will be assembled by vendors in Buffalo, N.Y., and in Los Angeles, and then shipped to Berkeley Lab for tuning before final delivery to SLAC.

    Work on the LCLS-II undulators is supported by the DOE Office of Science.

    See the full article here .

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

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


    SLAC Lab

    1
    Gabriella Carini
    Staff Scientist
    Joined SLAC: 2011
    Specialty: Developing detectors that capture light from X-ray sources
    Interviewed by: Amanda Solliday

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

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

    SLAC/LCLS

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

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

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

    When did you begin working with detectors?

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

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

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

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

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

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

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

    What do you like most about your work?

    2

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

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

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

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

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

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

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

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

    4
    And often, you work in vacuum. With “soft” or low-energy X-rays, they are absorbed very quickly in air. Your entire system has to be vacuum-compatible. With many of our substantial electronics, this requires some care.

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

    Is there a new project you are really excited about?

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

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

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

    6

    SLAC LCLS-II

    See the full article here .

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    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 3:55 pm on April 17, 2017 Permalink | Reply
    Tags: , , , , , , SLAC LCLS-II, ,   

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


    SLAC Lab

    September 22, 2016

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

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

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

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

    SLAC/LCLS

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

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

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

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

    Turning Heat into Electricity and Vice Versa

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

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

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

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

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

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

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

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

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

    Controlling Materials by Stimulating Charged Waves

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

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

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

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

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

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

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

    A Bright Future for Studies of the Electron-Phonon Dance

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

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

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

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

    SLAC/SSRL

    SACLA Free-Electron Laser Riken Japan


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

    See the full article here .

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

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


    SLAC Lab

    April 11, 2017
    Glennda Chui

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

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

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

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

    Materials that Surprise

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

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

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

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

    Joining Forces With Light Sources

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

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

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

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

    SLAC/SSRL

    LBNL/ALS

    SLAC LCLS

    SLAC/LCLS II

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

    Basic Questions and Practical Answers

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

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

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

    Running Experiments in Supercomputers

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

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

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

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

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

    See the full article here .

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  • richardmitnick 12:11 pm on March 28, 2017 Permalink | Reply
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    From FNAL: “LCLS-II prototype cryomodule: a success story 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    March 22, 2017
    Rich Stanek

    1
    More than 150 people at Fermilab have contributed to the design and assembly of the prototype cryomodule for LCLS-II. Photo: Reidar Hahn


    SLAC LCLS-II

    A project is like a good book: As you complete one chapter you start the next, but sometimes you cannot wait and you read ahead.

    The LCLS-II project, a next-generation X-ray light source being built at SLAC, one that is based on a superconducting RF electron linac operating in continuous-wave mode, has completed Chapter One – the prototype cryomodule (pCM). And now we are already well into the assembly of the second, third and fourth cryomodules.

    As one of the partner labs, Fermilab is responsible for the design of LCLS-II’s 1.3-gigahertz cryomodules, as well as assembly and testing for 19 of them. (LCLS-II will have a total of 40 of these cryomodules, and Jefferson Lab is assembling the rest.) Additionally, Fermilab is designing and will assemble and test three 3.9-gigahertz cryomodules and has responsibility for the procurement of the cryogenic distribution system for the LCLS-II linear accelerator.

    The pCM assembly and testing have been very successful, due in large part to the technical skills and dedication to quality of our entire team. Still, it was a learning experience, which has made our SRF and cryogenic organizations in the Accelerator and Technical divisions stronger and more tightly connected.

    The pCM met most of its acceptance criteria, to the point where it could be used in the LCLS-II linac. The majority of the design has been verified; the energy gain exceeds the specification; the average quality factor exceeds the goal and sets a new world record (3.0 x 1010); the superconducting magnet meets specification; the new tuner design was verified; the modified fundamental power coupler (in continuous-wave operation) was shown to meet specification; instrumentation and controls worked as planned; and the implementation of magnetic hygiene (first time in a cryomodule) was very successful.

    The one issue that remains is to reduce the microphonics levels so as to allow better amplitude and phase control of the cryomodule’s eight accelerating cavities, which must operate in unison.

    I must stress again how this success was driven by our team effort. Particularly evident in the pCM testing was the ability of the Technical and Accelerator division personnel to work together to accomplish the task at hand.

    The challenge to design, build and test the prototype CM drew on the work of a wide range of team members across many organizations. From beginning to end, the team functioned well. Contributions were made by staff responsible for design, procurement, part inspection, component handling and transportation, cavity testing and qualification, machining and welding, string assembly, cryomodule assembly, leak checking, installation, RF power and controls, cryogenics, and testing.

    In all, more than 150 individuals at Fermilab are contributing to the LCLS-II effort, and each has reason to be proud of their work. I am very fortunate to be able to lead this team, and I’m thankful for their dedication and strong efforts.

    Just as with a good book, once you start reading you cannot put it down; the better the book, the more motivated you are to complete reading it. So it is with this project as we are now into the execution phase. We have gotten a taste of our first success and look forward to the next chapters of the story and to completing our work.

    Rich Stanek is the Fermilab LCLS-II senior team leader.

    See the full article here .

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 2:03 pm on March 14, 2017 Permalink | Reply
    Tags: , , SLAC LCLS-II,   

    From Symmetry: “The life of an accelerator” 

    Symmetry Mag

    Symmetry

    03/14/17
    Manuel Gnida


    SLAC

    Tens of thousands of accelerators exist around the world, producing powerful particle beams for the benefit of medical diagnostics, cancer therapy, industrial manufacturing, material analysis, national security, and nuclear as well as fundamental particle physics. Particle beams can also be used to produce powerful beams of X-rays.

    Many of these particle accelerators rely on artfully crafted components called cavities.

    The world’s longest linear accelerator (also known as a linac) sits at the Department of Energy’s SLAC National Accelerator Laboratory. It stretches two miles and accelerates bunches of electrons to very high energies.

    The SLAC linac has undergone changes in its 50 years of operation that illustrate the evolution of the science of accelerator cavities. That evolution continues and will determine what the linac does next.


    SLAC/LCLS II

    Robust copper

    An accelerator cavity is a mostly closed, hollow chamber with an opening on each side for particles to pass through. As a particle moves through the cavity, it picks up energy from an electromagnetic field stored inside. Many cavities can be lined up like beads on a string to generate higher and higher particle energies.

    When SLAC’s linac first started operations, each of its cavities was made exclusively from copper. Each tube-like cavity consisted of a 1-inch-long, 4-inch-wide cylinder with disks on either side. Technicians brazed together more than 80,000 cavities to form a straight particle racetrack.

    Scientists generate radiofrequency waves in an apparatus called a klystron that distributes them to the cavities. Each SLAC klystron serves a 10-foot section of the beam line. The arrival of the electron bunch inside the cavity is timed to match the peak in the accelerating electric field. When a particle arrives inside the cavity at the same time as the peak in the electric field, then that bunch is optimally accelerated.

    “Particles only gain energy if the variable electric field precisely matches the particle motion along the length of the accelerator,” says Sami Tantawi, an accelerator physicist at Stanford University and SLAC. “The copper must be very clean and the shape and size of each cavity must be machined very carefully for this to happen.”

    In its original form, SLAC’s linac boosted electrons and their antimatter siblings, positrons, to an energy of 50 billion electronvolts. Researchers used these beams of accelerated particles to study the inner structure of the proton, which led to the discovery of fundamental particles known as quarks.

    Today almost all accelerators in the world—including smaller systems for medical and industrial applications—are made of copper. Copper is a good electric conductor, which is important because the radiofrequency waves build up an accelerating field by creating electric currents in the cavity walls. Copper can be machined very smoothly and is cheaper than other options, such as silver.

    “Copper accelerators are very robust systems that produce high acceleration gradients of tens of millions of electronvolts per meter, which makes them very attractive for many applications,” says SLAC accelerator scientist Chris Adolphsen.

    Today, one-third of SLAC’s original copper linac is used to accelerate electrons for the Linac Coherent Light Source, a facility that turns energy from the electron beam into what is currently the world’s brightest X-ray laser light.

    Researchers continue to push the technology to higher and higher gradients—that is, larger and larger amounts of acceleration over a given distance.

    “Using sophisticated computer programs on powerful supercomputers, we were able to develop new cavity geometries that support almost 10 times larger gradients,” Tantawi says. “Mixing small amounts of silver into the copper further pushes the technology toward its natural limits.” Cooling the copper to very low temperatures helps as well. Tests at 45 Kelvin—negative 384 degrees Fahrenheit—have shown to increase acceleration gradients 20-fold compared to SLAC’s old linac.

    Copper accelerators have their limitations, though. SLAC’s historic linac produces 120 bunches of particles per second, and recent developments have led to copper structures capable of firing 80 times faster. But for applications that need much higher rates, Adolphsen says, “copper cavities don’t work because they would melt.”

    Chill niobium

    For this reason, crews at SLAC are in the process of replacing one-third of the original copper linac with cavities made of niobium.

    Niobium can support very large bunch rates, as long as it is cooled. At very low temperatures, it is what’s known as a superconductor.

    “Below the critical temperature of 9.2 Kelvin, the cavity walls conduct electricity without losses, and electromagnetic waves can travel up and down the cavity many, many times, like a pendulum that goes on swinging for a very long time,” says Anna Grassellino, an accelerator scientist at Fermi National Accelerator Laboratory. “That’s why niobium cavities can store electromagnetic energy very efficiently and can operate continuously.”

    You can find superconducting niobium cavities in modern particle accelerators such as the Large Hadron Collider at CERN and the CEBAF accelerator at Thomas Jefferson National Accelerator Facility. The European X-ray Free-Electron Laser in Germany, the European Spallation Source at CERN, and the Facility for Rare Isotope Beams at Michigan State University are all being built using niobium technology. Niobium cavities also appear in designs for the next-generation International Linear Collider.

    At SLAC, the niobium cavities will support LCLS-II, an X-ray laser that will produce up to a million ultrabright light flashes per second. The accelerator will have 280 cavities, each about three feet long with a 3-inch opening for the electron beam to fly through. Sets of eight cavities will be strung together into cryomodules that keep the cavities at a chilly 2 Kelvin, which is colder than interstellar space.

    Each niobium cavity is made by fusing together two halves stamped from a sheet of pure metal. The cavities are then cleaned very thoroughly because even the tiniest impurities would degrade their performance.

    The shape of the cavities is reminiscent of a stack of shiny donuts. This is to maximize the cavity volume for energy storage and to minimize its surface area to cut down on energy dissipation. The exact size and shape also depends on the type of accelerated particle.

    “We’ve come a long way since the first development of superconducting cavities decades ago,” Grassellino says. “Today’s niobium cavities produce acceleration gradients of up to about 50 million electronvolts per meter, and R&D work at Fermilab and elsewhere is further pushing the limits.”

    Hot plasma

    Over the past few years, SLAC accelerator scientists have been working on a way to push the limits of particle acceleration even further: accelerating particles using bubbles of ionized gas called plasma.

    Plasma wakefield acceleration is capable of creating acceleration gradients that are up to 1000 times larger than those of copper and niobium cavities, promising to drastically shrink the size of particle accelerators and make them much more powerful.

    “These plasma bubbles have certain properties that are very similar to conventional metal cavities,” says SLAC accelerator physicist Mark Hogan. “But because they don’t have a solid surface, they can support extremely high acceleration gradients without breaking down.”

    Hogan’s team at SLAC and collaborators from the University of California, Los Angeles, have been developing their plasma acceleration method at the Facility for Advanced Accelerator Experimental Tests, using an oven of hot lithium gas for the plasma and an electron beam from SLAC’s copper linac.

    Researchers create bubbles by sending either intense laser light or a high-energy beam of charged particles through plasma. They then send beams of particles through the bubbles to be accelerated.

    When, for example, an electron bunch enters a plasma, its negative charge expels plasma electrons from its flight path, creating a football-shaped cavity filled with positively charged lithium ions. The expelled electrons form a negatively charged sheath around the cavity.

    This plasma bubble, which is only a few hundred microns in size, travels at nearly the speed of light and is very short-lived. On the inside, it has an extremely strong electric field. A second electron bunch enters that field and experiences a tremendous energy gain. Recent data show possible energy boosts of billions of electronvolts in a plasma column of just a little over a meter.

    “In addition to much higher acceleration gradients, the plasma technique has another advantage,” says UCLA researcher Chris Clayton. “Copper and niobium cavities don’t keep particle beams tightly bundled and require the use of focusing magnets along the accelerator. Plasma cavities, on the other hand, also focus the beam.”

    Much more R&D work is needed before plasma wakefield accelerator technology can be turned into real applications. But it could represent the future of particle acceleration at SLAC and of accelerator science as a whole.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 8:49 pm on January 31, 2017 Permalink | Reply
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    From SLAC: “Taking Down a Giant: 699 Tons of SLAC’s Accelerator Removed for Upgrade” 


    SLAC Lab

    January 31, 2017

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

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

    2
    Illustration of an electron beam traveling through a niobium cavity – a key component of SLAC’s future LCLS-II X-ray laser. Kept at minus 456 degrees Fahrenheit, a temperature at which niobium conducts electricity without losses, these cavities will power a highly energetic electron beam that will create up to 1 million X-ray flashes per second – more than any other current or planned X-ray laser. (SLAC National Accelerator Laboratory)

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

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


    Access mp4 video here.

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

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

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

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

    699 Tons in 106 Truckloads

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

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

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

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

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

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

    3
    LCLS-II. The Future is Supercool

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

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

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

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

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

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

    See the full article here .

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  • richardmitnick 7:48 am on November 4, 2016 Permalink | Reply
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    From SLAC: SLAC, Berkeley Lab Researchers Prepare for Scientific Computing on the Exascale” 


    SLAC Lab

    November 3, 2016

    1
    NERSC CRAY Cori supercomputer
    Development and testing of future exascale computing tools for X-ray laser data analysis and the simulation of plasma wakefield accelerators will be done on the Cori supercomputer at NERSC, the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory. (NERSC)

    Researchers at the Department of Energy’s SLAC National Accelerator Laboratory are playing key roles in two recently funded computing projects with the goal of developing cutting-edge scientific applications for future exascale supercomputers that can perform at least a billion billion computing operations per second – 50 to 100 times more than the most powerful supercomputers in the world today.

    The first project, led by SLAC, will develop computational tools to quickly sift through enormous piles of data produced by powerful X-ray lasers. The second project, led by DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab), will reengineer simulation software for a potentially transformational new particle accelerator technology, called plasma wakefield acceleration.

    The projects, which will each receive $10 million over four years, are among 15 fully-funded application development proposals and seven proposals selected for seed funding by the DOE’s Exascale Computing Project (ECP). The ECP is part of President Obama’s National Strategic Computing Initiative and intends to maximize the benefits of high-performance computing for U.S. economic competiveness, national security and scientific discovery.

    “Many of our modern experiments generate enormous quantities of data,” says Alex Aiken, professor of computer science at Stanford University and director of the newly formed SLAC Computer Science division, who is involved in the X-ray laser project. “Exascale computing will create the capabilities to handle unprecedented data volumes and, at the same time, will allow us to solve new, more complex simulation problems.”

    Analyzing ‘Big Data’ from X-ray Lasers in Real Time

    X-ray lasers, such as SLAC’s Linac Coherent Light Source (LCLS) have been proven to be extremely powerful “microscopes” that are capable of glimpsing some of nature’s fastest and most fundamental processes on the atomic level.

    SLAC/LCLS
    SLAC/LCLS

    Researchers use LCLS, a DOE Office of Science User Facility, to create molecular movies, watch chemical bonds form and break, follow the path of electrons in materials and take 3-D snapshots of biological molecules that support the development of new drugs.

    At the same time X-ray lasers also generate giant amounts of data. A typical experiment at LCLS, which fires 120 flashes per second, fills up hundreds of thousands of gigabytes of disk space. Analyzing such a data volume in a short amount of time is already very challenging. And this situation is set to become dramatically harder: The next-generation LCLS-II X-ray laser will deliver 8,000 times more X-ray pulses per second, resulting in a similar increase in data volumes and data rates.

    SLAC/LCLS II schematic
    SLAC/LCLS II schematic

    Estimates are that the data flow will greatly exceed a trillion data ‘bits’ per second, and require hundreds of petabytes of online disk storage.

    As a result of the data flood even at today’s levels, researchers collecting data at X-ray lasers such as LCLS presently receive only very limited feedback regarding the quality of their data.

    “This is a real problem because you might only find out days or weeks after your experiment that you should have made certain changes,” says Berkeley Lab’s Peter Zwart, one of the collaborators on the exascale project, who will develop computer algorithms for X-ray imaging of single particles. “If we were able to look at our data on the fly, we could often do much better experiments.”

    Amedeo Perazzo, director of the LCLS Controls & Data Systems Division and principal investigator for this “ExaFEL” project, says, “We want to provide our users at LCLS, and in the future LCLS-II, with very fast feedback on their data so that can make important experimental decisions in almost real time. The idea is to send the data from LCLS via DOE’s broadband science network ESnet to NERSC, the National Energy Research Scientific Computing Center, where supercomputers will analyze the data and send the results back to us – all of that within just a few minutes.” NERSC and ESnet are DOE Office of Science User Facilities at Berkeley Lab.

    LBL NERSC Cray XC30 Edison supercomputer
    LBL NERSC Cray XC30 Edison supercomputer

    lcls-ii-image
    LCLS II

    X-ray data processing and analysis is quite an unusual task for supercomputers. “Traditionally these high-performance machines have mostly been used for complex simulations, such as climate modeling, rather than processing real-time data” Perazzo says. “So we’re breaking completely new ground with our project, and foresee a number of important future applications of the data processing techniques being developed.”

    This project is enabled by the investments underway at SLAC to prepare for LCLS-II, with the installation of new infrastructure capable of handling these enormous amounts of data.

    A number of partners will make additional crucial contributions.

    “At Berkeley Lab, we’ll be heavily involved in developing algorithms for specific use cases,” says James Sethian, a professor of mathematics at the University of California, Berkeley, and head of Berkeley Lab’s Mathematics Group and the Center for Advanced Mathematics for Energy Research Applications (CAMERA). “This includes work on two different sets of algorithms. The first set, developed by a team led by Nick Sauter, consists of well-established analysis programs that we’ll reconfigure for exascale computer architectures, whose larger computer power will allow us to do better, more complex physics. The other set is brand new software for emerging technologies such as single-particle imaging, which is being designed to allow scientists to study the atomic structure of single bacteria or viruses in their living state.”

    The “ExaFEL” project led by Perazzo will take advantage of Aiken’s newly formed Stanford/SLAC team, and will collaborate with researchers at Los Alamos National Laboratory to develop systems software that operates in a manner that optimizes its use of the architecture of the new exascale computers.

    “Supercomputers are very complicated, with millions of processors running in parallel,” Aiken says. “It’s a real computer science challenge to figure out how to use these new architectures most efficiently.”

    Finally, ESnet will provide the necessary networking capabilities to transfer data between the LCLS and supercomputing resources. Until exascale systems become available in the mid-2020s, the project will use NERSC’s Cori supercomputer for its developments and tests.

    esnet-map
    ESnet

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 9:21 pm on August 9, 2016 Permalink | Reply
    Tags: , , , SLAC LCLS-II,   

    From SLAC: “Perfection in Sight: SLAC Receives New Mirrors for X-ray Laser” 


    SLAC Lab

    August 1, 2016

    The Mirrors Only Differ by One Atom in Flatness From End to End

    1
    SLAC engineer Corey Hardin inspects one of the newly-arrived mirrors in a clean room facility. (SLAC National Accelerator Laboratory)

    2
    May Ling Ng, SLAC engineer, makes adjustments to the mirror restraints during a test of the holding system’s effect on mirror shape. These measurements are needed to maintain the flatness of the mirror within one atom over the entire one-meter length. (SLAC National Accelerator Laboratory)

    Scientists are installing new mirrors to improve the quality of the X-ray laser beam at the Department of Energy’s SLAC National Accelerator Laboratory.

    The meter-long mirrors are the ultimate in flatness, smooth to within the height of one atom or one-fifth of a nanometer.

    If Earth had the same surface, the hills and valleys would only vary by the width of a pencil, says Daniele Cocco, engineering physicist and head of the optics group at SLAC’s Linac Coherent Light Source (LCLS), a DOE Office of Science User Facility.

    SLAC LCLS Inside
    SLAC/LCLS

    Right now, the mirrors are stored in a clean room to avoid dust and prevent damage. Cocco and other engineers only handle the mirrors while wearing gowns, hairnets, masks and gloves. They’re testing the mirrors to see how they will respond to heat and mechanical stress while the beam is running. Both cause tiny deformations on the surface, and even changes as small as half a nanometer can cause big problems.

    Five of these mirrors will be installed in LCLS by the beginning of next year and available for experiments in summer 2017. The new arrivals will join the 12 flat and curved mirrors that currently steer and focus light at LCLS, which is almost one mile long. Eventually, the upgraded mirror system will have a total of 28 mirrors.

    This is the first time the mirrors have been replaced at LCLS. The original mirrors were installed in 2009, when the free-electron laser came online.

    As the laser strikes the mirrors, some degradation of the reflective surface occurs over time. Since the originals were built, there have been improvements in how the mirrors are made, and engineers also better understand how the mirrors can be tailored to the LCLS beam.

    When light hits the reflective surfaces, the photons slant toward a specific point. The X-rays are shaped to the need of the experiment, from a focal spot less than a micron in diameter to as wide as a few millimeters. The beam quality also must be preserved in order to reveal the state of molecules and atoms during a range of processes that occur in biology, chemistry, materials science, and energy.

    “Time is lost when a beam isn’t perfectly uniform, and you’re not able to find the perfect spot on the sample,” Cocco says. “With mirrors this precise, it’s much easier.”

    A Japanese optics company, JTEC Corporation, fabricates the mirrors for synchrotrons and other X-ray laser research facilities such as Japan’s Spring-8 Angstrom Compact Free-Electron Laser (SACLA) and the European X-ray Free-Electron Laser (EXFEL), located in Hamburg, Germany and due to come online in 2017.

    Each mirror is made from an individual silicon crystal, artificially grown in a lab. After the mirror is polished with conventional techniques, the company uses a process called elastic emission machining, where a jet of ultra-pure water containing fine particles removes any remaining imperfections atom by atom.

    Blemishes in the mirror can create imperfections in the X-ray beam.

    “These latest mirrors preserve the beam quality within 97 percent, and the manufacturing technology is continuing to get better,” Cocco says.

    With a coherent laser beam, such as the one at LCLS, photons traveling at fixed wavelengths have a specific relationship to each other.

    “It’s not random. The light propagates as a perfect wave,” Cocco says. “Even minimal bumps alter the properties of the beam, irreversibly destroying the perfection of the wavefront.”

    The light beam also travels over a long distance, which means any disruption can amplify.

    Two of the mirrors will be installed adjacent to the front end of the undulator hall at LCLS. The other three will be located 200 meters further down the beam line, in the X-ray transport tunnel between the near and far halls.

    The mirrors will also be able to handle the higher energy range of LCLS-II, the next generation of SLAC’s X-ray laser.

    SLAC LSLS II new
    SLAC/LCLS-II work at LBL

    1
    SLAC/LCLS-II work at FNAL

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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