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  • richardmitnick 2:03 pm on March 14, 2017 Permalink | Reply
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    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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    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 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 .

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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 9:21 pm on August 9, 2016 Permalink | Reply
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    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 .

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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 1:46 pm on April 4, 2016 Permalink | Reply
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    From LBL: “Construction Begins on Major Upgrade to World’s Brightest X-ray Laser” 

    Berkeley Logo

    Berkeley Lab

    April 4, 2016
    Glenn Roberts Jr.
    510-486-5582
    geroberts@lbl.gov

    1
    An electron beam travels through a niobium cavity, a key component of a future LCLS-II X-ray laser, in this illustration. Kept at minus 456 degrees Fahrenheit, these cavities will power a highly energetic electron beam that will create up to 1 million X-ray flashes per second. (Credit: SLAC National Accelerator Laboratory)

    Construction begins today on a major upgrade to a unique X-ray laser that will add a second X-ray laser beam that’s 10,000 times brighter, on average, than the first one and fires 8,000 times faster—up to a million pulses per second.

    Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) are contributing key components for the project, known as LCLS-II, that will greatly increase the power and capacity of the Linac Coherent Light Source (LCLS), a free-electron X-ray laser at the DOE’s SLAC National Accelerator Laboratory in Menlo Park, Calif.

    2
    A prototype LCLS-II 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)

    3
    The powerful, toothlike rows of magnets (center) in this prototype device, called an undulator, can produce up to 7 tons of force. This undulator, designed for LCLS-II, an X-ray laser project, is needed to magnetically wiggle electrons, causing them to emit X-ray light. (Credit: Roy Kaltschmidt/Berkeley Lab)

    4
    Berkeley Lab’s Fernando Sannibale inspects the APEX (Advanced Photoinjector Experiment) that has served as a test electron gun and injector system for LCLS-II. (Credit: Roy Kaltschmidt/Berkeley Lab)

    The project, which is now formally approved by the DOE to start construction and is being funded by DOE’s Office of Science, will enable experiments that sharpen our view of how nature works on the atomic level and on ultrafast timescales.

    Like the existing facility, LCLS-II will use electrons accelerated to nearly the speed of light to generate beams of extremely bright X-ray laser light. The electrons fly through a series of magnets, called an undulator, that forces them to travel a zigzag path and give off energy in the form of X-rays. At present, electrons are accelerated in a copper structure that operates at room temperature and allows the generation of 120 X-ray laser pulses per second.

    For LCLS-II, crews will install a new accelerator that is called “superconducting” because its metal cavities, made of niobium, will conduct electricity with nearly zero loss when chilled to minus 456 degrees Fahrenheit. Accelerating electrons through a series of these cavities allows the generation of an almost continuous X-ray laser beam.

    To make the upgrade a reality, a nationwide collaboration has formed that includes SLAC, Berkeley Lab and three other national labs—Argonne, Fermilab and Jefferson Lab—and Cornell University, with each partner making key contributions to project planning as well as to component design, acquisition and construction.

    “We bring a lot of expertise to the LCLS-II collaboration,” said John Corlett, senior team leader for the LCLS-II effort at Berkeley Lab. “We were selected to provide critical technologies that generate the high-brightness and high-repetition-rate electron beam that is the first component in the superconducting accelerator chain, and the undulators that are the core of the free-electron laser X-ray source.

    “Additionally, we have lead roles in control of the superconducting cavities, and in modeling the electron beam to optimize the laser performance.”

    SLAC’s John Galayda, head of the LCLS-II project team, said, “We couldn’t do this without our collaborators. To bring all the components together and succeed, we need the expertise of all partners, their key infrastructure and the commitment of their best people.”

    When LCLS opened six years ago as a DOE Office of Science User Facility, it was the first light source of its kind—a unique X-ray microscope that uses the brightest and fastest X-ray pulses ever made to provide unprecedented details of the atomic world.

    Hundreds of scientists, including Berkeley Lab researchers, use LCLS each year to catch a glimpse of nature’s fundamental processes in unprecedented detail. Molecular movies reveal how chemical bonds form and break; ultrafast snapshots capture electric charges as they rapidly rearrange in materials and change their properties; and sharp 3-D images of disease-related proteins provide atomic-level details that could hold the key for discovering potential cures.

    The new X-ray laser will work in parallel with the existing one, with each occupying one-third of SLAC’s 2-mile-long linear accelerator (“linac”) tunnel. Together they will allow researchers to make observations over a wider energy range, capture detailed snapshots of rapid processes, probe delicate samples that are beyond the reach of other light sources and gather more data in less time, thus greatly increasing the number of experiments that can be performed at this pioneering facility.

    SLAC is now clearing out the first third of the linac to make room for the superconducting accelerator, which is scheduled to begin operations in early 2020.

    “LCLS-II will take X-ray science to the next level, opening the door to a whole new range of studies of the ultrafast and ultrasmall,” said LCLS Director Mike Dunne. “This will tremendously advance our ability to develop transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions.”

    See the full article here .

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  • richardmitnick 1:23 pm on April 4, 2016 Permalink | Reply
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    From FNAL: “Putting it all together: Fermilab assembles first cryomodule for LCLS-II” 

    FNAL II photo

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

    April 4, 2016
    Leah Hesla

    1
    Members of the Fermilab Technical Division line up eight superconducting accelerator cavities to form a cavity string destined for SLAC National Accelerator Laboratory’s LCLS-II. Photo: Reidar Hahn

    In February, a Fermilab team came together to witness a moment they’d looked forward to for over a year. Crew members parted the plastic sheeting at one end of a cleanroom and rolled out on narrow tracks a long string of eight accelerating cavities. It was the first cavity string for LCLS-II, which will greatly increase the power and capacity of SLAC’s Linac Coherent Light Source.

    SLAC/LCLS II schematic
    SLAC/LCLS II schematic

    Accelerating cavities are structures that impart energy to a particle beam, and they’re the heart of the cryomodule — a major accelerator section — that Fermilab has designed and is building for LCLS-II.

    “It’s a big deal. The cavity string’s all bolted up — it’s beautiful,” said SLAC scientist Marc Ross, LCLS-II cryogenics systems manager. “It’s a concrete step toward LCLS-II’s realization.”

    SLAC’s LCLS-II is a powerful X-ray laser that will allow scientists to glimpse nature’s fundamental processes on an atomic level and ultrafast time scales. Today SLAC announced DOE approval of the start of construction for LCLS-II.

    Since the rollout, the Fermilab team has been outfitting the cavity string with cooling equipment, instrumentation and structural support to form the cryomodule. By summer, they will have completed their first one.

    “To me this is a major milestone because it shows that we can do it,” said Camille Ginsburg, the cryomodule team lead for the Fermilab LCLS-II effort. “It represents having tested all of those cavities successfully, finalized the design and put together all the assembly infrastructure that was required.”

    The cryomodule is destined for LCLS-II’s new superconducting linear accelerator. Electrons speeding down the accelerator will generate an almost continuous X-ray laser beam with pulses of up to a million times per second — thousands of times faster than the current LCLS puts out. To be superconducting, the cryomodule’s cavities, made of niobium, must operate at minus 456 degrees Fahrenheit.

    The linear accelerator backbone of LCLS-II comprises 37 cryomodules. Thomas Jefferson National Accelerator Facility in Virginia, another LCLS-II collaborating institution, will build 18 cryomodules of this type. Fermilab is building 17 of these cryomodules plus two that will operate at a higher frequency.

    2
    Andrew Penhollow of the Fermilab Technical Division tends to the LCLS-II prototype cavity string, which is seen here mounted to cooling infrastructure. Photo: Reidar Hahn

    The boost from a pulsed beam to a continuous one means that the new accelerator will require much more power to operate. And with great power comes the need for great efficiency.

    That’s why Fermilab scientists have, for the better part of a decade, been working on methods for building and treating cavities to be as efficient as they can be. By imparting maximum energy to the beam with minimal energy loss, efficient cavities help drive down the cost.

    Last year, the Fermilab team reported a world-record quality factor, an indicator of the cavity’s efficiency in minimizing thermal losses.

    “The performance of the individually tested cavities that were put into the string was far beyond anything that has been put into such a cryomodule before,” Ross said.

    Fermilab also designed the cryomodule’s instrumentation to be able to handle the high power and its plumbing system to carry away heat.

    “With continuous-wave operation, there’s a much higher heat load than there is with pulsed-beam acceleration, so everything has to be more robust,” said Fermilab’s Elvin Harms, who leads cryomodule testing for LCLS-II at Fermilab.

    Scientists and engineers specially designed the couplers that transfer the radio-frequency power to the cavities with thicker, high-conductivity plating, for example, to carry away the high heat load.

    The assembly process to this point has been painstaking, said Fermilab scientist Anna Grassellino, who is responsible for cavity preparation and testing for LCLS-II. And it promises to remain that way until the cryomodule is finally delivered to SLAC.

    “Everything that’s happening now with the cryomodule assembly — every step is critical,” Grassellino said. “How you handle the parts can affect performance.”

    Technicians who successfully assembled the first cavity string in the cleanroom spent two weeks carefully putting the components together. Following a protocol established at DESY in Germany and Saclay in France and borne out in tests at the Fermilab Accelerator Science and Technology facility, they moved in slow motion, since too-rapid movements would create particulates that could make their way into the cavity, degrading its operation in an accelerator.

    “These techniques that seem ancillary are actually quite sophisticated,” Grassellino said. “When the cavity string was finished, it was, ‘Phew! Now it’s sealed, now it rolls out.’”

    Crews are carefully installing shielding to protect the cavities from Earth’s magnetic field, which would ruin their performance; welding the cavity string to the plumbing for the super-cooled helium that will keep the cavities cold; and connecting everything structurally inside the vacuum vessel.

    Cryomodule tests will begin early this summer. Fermilab and Jefferson Lab plan to move the completed cryomodules to SLAC toward the end of 2016.

    “Congratulations to the entire cryomodule team here, at Jefferson Lab and at SLAC,” said Rich Stanek, Fermilab LCLS-II senior team leader. “We’re working hard to deliver cryomodules that meet or exceed specifications within the project cost and schedule.”

    LCLS-II, like its predecessor LCLS, will be a DOE Office of Science User Facility.

    See the full article here .

    Please help promote STEM in your local schools.

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    Fermilab Campus

    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 12:58 pm on April 4, 2016 Permalink | Reply
    Tags: , , , SLAC LCLS-II, ,   

    From SLAC: “Major Upgrade Will Boost Power of World’s Brightest X-ray Laser” 


    SLAC Lab

    April 4, 2016

    Construction begins today on a major upgrade to a unique X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory. The project will add a second X-ray laser beam that’s 10,000 times brighter, on average, than the first one and fires 8,000 times faster, up to a million pulses per second.

    The project, known as LCLS-II, will greatly increase the power and capacity of SLAC’s Linac Coherent Light Source (LCLS) for experiments that sharpen our view of how nature works on the atomic level and on ultrafast timescales.

    SLAC/LCLS
    SLAC/LCLS

    “LCLS-II will take X-ray science to the next level, opening the door to a whole new range of studies of the ultrafast and ultrasmall,” said LCLS Director Mike Dunne.

    SLAC/LCLS II schematic
    SLAC/LCLS II schematic

    “This will tremendously advance our ability to develop transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions.”

    SLAC Director Chi-Chang Kao said, “Our lab has a long tradition of building and operating premier X-ray sources that help users from around the world pursue cutting-edge research in chemistry, materials science, biology and energy research. LCLS-II will keep the U.S. at the forefront of X-ray science.”


    Access mp4 video here .
    This 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. These unrivaled capabilities will help researchers address a number of grand challenges in science by capturing detailed snapshots of rapid processes that are beyond the reach of other light sources. (SLAC National Accelerator Laboratory)

    A Superior X-ray Microscope

    When LCLS opened six years ago as a DOE Office of Science User Facility, it was the first light source of its kind – a unique X-ray microscope that uses the brightest and fastest X-ray pulses ever made to provide unprecedented details of the atomic world.

    Hundreds of scientists use LCLS each year to catch a glimpse of nature’s fundamental processes in unprecedented detail. Molecular movies reveal how chemical bonds form and break; ultrafast snapshots capture electric charges as they rapidly rearrange in materials and change their properties; and sharp 3-D images of disease-related proteins provide atomic-level details that could hold the key for discovering potential cures.

    The new X-ray laser will work in parallel with the existing one, with each occupying one-third of SLAC’s 2-mile-long linear accelerator tunnel. Together they will allow researchers to make observations over a wider energy range, capture detailed snapshots of rapid processes, probe delicate samples that are beyond the reach of other light sources and gather more data in less time, thus greatly increasing the number of experiments that can be performed at this pioneering facility.

    “The upgrade will benefit X-ray experiments in many different ways, and I’m very excited to use the new capabilities for my own research,” said Brown University Professor Peter Weber, who co-led an LCLS study that used X-ray scattering to track ultrafast structural changes as ring-shaped gas molecules burst open in a chemical reaction vital to many processes in nature. “With LCLS-II, we’ll be able to bring the motions of atoms much more into focus, which will help us better understand the dynamics of crucial chemical reactions.”

    1
    The future LCLS-II X-ray laser (blue, at left) is shown alongside the existing LCLS (red, at right). LCLS uses the last third of SLAC’s 2-mile-long linear accelerator – a hollow copper structure that operates at room temperature and allows the generation of 120 X-ray pulses per second. For LCLS-II, the first third of the copper accelerator will be replaced with a superconducting one, capable of creating up to 1 million X-ray flashes per second. (SLAC National Accelerator Laboratory)

    A Big Leap in X-ray Laser Performance

    3
    This photo shows the prototype of a novel electron source for LCLS-II. Located at the future X-ray laser’s front end, it will produce bunches of electrons for the generation of X-ray pulses that are only quadrillionths of a second long, at rates of up to a million bunches per second. (R. Kaltschmidt/Berkeley Lab)

    Like the existing facility, LCLS-II will use electrons accelerated to nearly the speed of light to generate beams of extremely bright X-ray laser light. The electrons fly through a series of magnets, called an undulator, that forces them to travel a zigzag path and give off energy in the form of X-rays.

    But the way those electrons are accelerated will be quite different, and give LCLS-II much different capabilities.

    At present, electrons are accelerated down a copper pipe that operates at room temperature and allows the generation of 120 X-ray laser pulses per second.

    For LCLS-II, crews will install a superconducting accelerator. It’s called “superconducting” because its niobium metal cavities conduct electricity with nearly zero loss when chilled to minus 456 degrees Fahrenheit. Accelerating electrons through a series of these cavities allows the generation of an almost continuous X-ray laser beam with pulses that are 10,000 times brighter, on average, than those of LCLS and arrive up to a million times per second.

    4
    Electron bunches will gain energy in niobium cavities like these. Cooled to extremely low temperature, these “superconducting” cavities allow radiofrequency fields to boost electron energies without electrical resistance – a crucial property for the acceleration of electrons at a rate of up to a million bunches per second. (R. Hahn/Fermilab)

    In addition to a new accelerator, LCLS-II requires a number of other cutting-edge components, including a new electron source, two powerful cryoplants that produce refrigerant for the niobium structures, and two new undulators to generate X-rays.

    4
    This image shows a segment of an undulator magnet that will turn powerful beams of electrons into extremely bright X-ray light. Two undulators for generating low- and high-energy X-rays at SLAC’s future X-ray laser facility will consist of 21 and 32 segments, respectively. (R. Kaltschmidt/Berkeley Lab)

    6
    Illustration of the electron accelerator of SLAC’s future rapid-fire LCLS-II X-ray laser. No image credit

    Strong Partnerships for a Bright Future in X-ray Science

    6
    For LCLS-II, SLAC has teamed up with four other national labs – Argonne, Berkeley Lab, Fermilab and Jefferson Lab – and Cornell University, with each partner making key contributions to the many aspects of project planning as well as component design, acquisition and construction. (SLAC National Accelerator Laboratory)

    To make this major upgrade a reality, SLAC has teamed up with four other national labs – Argonne, Berkeley Lab, Fermilab and Jefferson Lab – and Cornell University, with each partner making key contributions to project planning as well as to component design, acquisition and construction.

    “We couldn’t do this without our collaborators,” said SLAC’s John Galayda, head of the LCLS-II project team. “To bring all the components together and succeed, we need the expertise of all partners, their key infrastructure and the commitment of their best people.”

    With favorable “Critical Decisions 2 and 3 (CD-2/3)” in March, DOE has formally approved construction of the $1 billion project, which is being funded by DOE’s Office of Science. SLAC is now clearing out the first third of the linac to make room for the superconducting accelerator, which is scheduled to begin operations in the early 2020s. In the meantime, LCLS will continue to serve the X-ray science community, except for a construction-related, six-month downtime in 2017 and a 12-month shutdown extending from 2018 into 2019.

    With the upgrades that are now moving forward, Dunne said, SLAC will have an X-ray laser facility that will enable groundbreaking research for years to come.

    See the full article here .

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

    From SLAC: “5 Ways SLAC’s X-ray Laser Can Change the Way We Live” 


    SLAC Lab

    March 9, 2016

    The First Five Years’ Points to a Bright Future of High-impact Discovery at LCLS

    SLAC LCLS
    LCLS

    SLAC LCLS-II line
    LCLS II

    If you’ve ever stood in a dark room wishing you had a flashlight, then you understand how scientists feel when faced with the mysteries of physical processes that happen at scales that are mind-bogglingly small and fast.

    The future of life-changing science – science that will spawn the electronic devices, medications and energy solutions of the future – depends on being able to see atoms and molecules at work.

    To do that you need special light – such as X-ray light with a wavelength as small as an atom – that pulses at the rate of femtoseconds. A femtosecond is to a second what a second is to 32 million years. It is the timescale for the basic building blocks of chemistry, biology and materials science.

    That’s why, six years ago, the Department of Energy’s SLAC National Accelerator Laboratory answered a bold call by the scientific community: Build a transformative tool for discovery, an X-ray laser so bright and fast it can unravel the hidden dynamics of our physical world.

    Since it began operation in 2009, this singularly powerful “microscope” has generated molecular movies, gotten a glimpse of the birth of a chemical bond, traced electrons moving through materials and made 3-D pictures of proteins that are key to drug discovery. Known to scientists as an X-ray free-electron laser (XFEL), SLAC’s Linac Coherent Light Source, or LCLS, is a DOE Office of Science User Facility that draws many hundreds of scientists from around the world each year to perform innovative experiments.

    The success of LCLS has inspired the spread of such machines all over the world.

    The latest issue of Reviews of Modern Physics contains the most comprehensive scientific overview of its accomplishments in a paper entitled, Linac Coherent Light Source: The First Five Years.

    LCLS staff scientists devoted about a year to compiling the collection of reports, says LCLS Director Mike Dunne.

    “We hope this extensive paper will be a valuable go-to source for this new field of science,” he said. “It describes many of the major accomplishments of the first X-ray laser of its kind. It also testifies to the power of this unique tool for scientific discovery that will benefit society in many ways.”

    Here are five ways SLAC’s X-ray laser and the science it enables can impact our future.

    1. Next-generation Computers and the Power Grid

    LCLS studies are helping to home in on the most promising materials and methods for transforming the electric power grid and driving next-generation computer components beyond classical limits.

    To make computers and other electronics faster and smaller, scientists need to understand and control materials’ magnetism and electronic behavior in new and more precise ways.

    LCLS has given us new, nanoscale views of how laser light rapidly flips the magnetic state of materials, providing new insight on how to write data with light. It has pinpointed the speed of electrical switching – such as what occurs in semiconductor transistors – with trillionth-of-a-second precision.

    Researchers at LCLS have also discovered a new, 3-D phenomenon that may be linked to high-temperature superconductivity, which allows some exotic materials to conduct electricity with zero resistance.

    2. Better, Cleaner Fuels and Chemicals

    The ability to take direct measurements of never-before-seen steps in chemical reactions is what scientists need to design more efficient reactions to produce fuels, fertilizers and industrial chemicals.

    While we know the starting ingredients and outcomes of chemical reactions, the early and middle steps are hard to see in real time at the atomic scale.

    LCLS X-ray pulses are so fast that they allow us to observe and analyze these previously unseen steps. They work like ultrabright flashes to capture X-ray snapshots of chemical reactions as they happen.

    Researchers have used LCLS to see new details of a reaction in catalytic converters that neutralizes pollution from car exhaust, and to produce “molecular movies” of a molecule transforming after one of its chemical bonds breaks.

    3. More Effective Medication with Fewer Side Effects

    Half of the medications on the market target special receptor proteins in the outer layer of our cells. To figure out how drugs work so we can make them more effective and reduce side effects, we need to see how they dock with these receptors in atom-by-atom detail.

    The best way to see how they fit is to form the protein-drug complexes into crystals and study them with X-rays, but many important samples don’t form big enough crystals or are too damage-prone for conventional X-ray tools. LCLS, though, can study very tiny crystals under more natural conditions, making it possible to determine the 3-D atomic structure of important proteins that had been out of reach.

    Already, LCLS has revealed a potential weakness in a protein involved in the transmission of African sleeping sickness, provided the best 3-D atomic-scale look at how blood pressure medicines and painkillers interact with receptors in our cells, and pinpointed the mechanism that allows our brain to send ultrafast chemical signals.

    In more recent studies, LCLS has also been used to image living bacteria that are responsible for generating the oxygen in our atmosphere, demonstrating an entirely new X-ray imaging technique.

    4. Renewable Energy that Mimics Nature

    LCLS allows us to study how plants use energy from sunlight to release oxygen into the air we breathe during a process called photosynthesis. The X-ray laser is uniquely capable of mapping the individual sunlight-triggered steps. Early data is already giving us a detailed understanding of photosynthesis – information that’s crucial for developing renewable, clean sources of energy that mimic nature.

    Scientists are also using the tool to study how light affects other living things. Just as sunlight can be life-giving, it can also be damaging. Studies at LCLS have revealed how our DNA protects itself from the sun’s ultraviolet rays and how proteins in bacteria and in our eyes shift shape in response to light.

    5. Fusion Reactions and Seeing Inside Planets

    High-power laser systems at SLAC heat matter to millions of degrees and crush it with billions of tons of pressure per square inch. Scientists use LCLS to measure what happens to matter under these extreme conditions with high precision at very small scales, and over very short periods of time.

    Some studies test the resilience of materials, such as those used in jet engines, to see how they fail. Others have simulated and studied the shock effects of meteorite impacts and have reproduced the conditions that are believed to exist at the heart of giant gas planets, which improves our understanding of how solar systems form.

    The results also give scientists new insight into how to replicate the fusion reactions that fuel our sun, an essential step in the pursuit of fusion energy as a power source.
    Looking to the Future

    “Many of the methods developed over the first years of LCLS operations responded to the needs of science to address vital areas of discovery that promise to have a significant impact on our lives,” Dunne emphasizes. “We expect that the coming years of XFEL innovation will push us further into the future, as we look ever deeper into the dynamics of our natural world.”

    “The Linac Coherent Light Source: The First Five Years,” was authored by a team representative of the X-ray and accelerator science groups at SLAC during this pioneering period of XFEL science: Christoph Bostedt, Sébastien Boutet, David M. Fritz, Zhirong Huang, Hae Ja Lee, Henrik T. Lemke, Aymeric Robert, William F. Schlotter, Joshua J. Turner and Garth J. Williams.

    Citation: Bostedt, et al., Reviews of Modern Physics, 9 March 2016 (10.1103/RevModPhys.88.015007).

    See the full article here .

    Please help promote STEM in your local schools.

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 5:10 pm on November 12, 2015 Permalink | Reply
    Tags: , , , , , , SLAC LCLS-II   

    From FNAL: “Fermilab attains unprecedented quality factor for LCLS-II dressed cavity” 

    FNAL II photo

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

    Nov. 6, 2015
    Chris Patrick

    1
    A Technical Division team rallies around a dressed cavity from the LCLS-II project. Photo: Reidar Hahn

    2
    An LCLS-II-type accelerator cavity prepares to be treated with nitrogen, a process that increases the cavity’s quality factor. Fermilab recently reported a record quality factor for LCLS-II-type cavities. Photo: Reidar Hahn

    Members of Fermilab’s Technical Division are working on superconducting radio-frequency cavities that are shaped like squatty beads on straight string. These prone, uniformly bulging tubes accelerate the particle beams that shoot through their hollow insides.

    The team recently achieved a record-high quality factor with a fully dressed cavity for a SLAC-headed project, Linac Coherent Light Source II.

    SLAC LCLS-II line
    LCLS-II line

    “This has taken a lot of hard work from a very dedicated crew,” said Rich Stanek, Fermilab LCLS-II senior team leader. Stanek acknowledged the entire cavity dressing team and all of the SRF scientists that helped reach this record quality factor.

    Quality factor, Q, is a measure of how efficient a particle acceleration cavity is. A higher Q means a cavity is losing less energy, which is more cost-effective.

    The two LCLS-II free-electron lasers will produce X-rays to probe a wide variety of materials, exotic and otherwise, at the nanoscale. Fermilab is responsible for designing, developing, building and testing about 150 nine-cell cavities for the LCLS-II superconducting accelerator. The R&D process began one-and-a-half years ago. It includes ensuring that the cavities meet certain Q values during testing.

    “This is the first integrated test we did,” said Nikolay Solyak, project support group leader. In an integrated test, everything is checked under real conditions. “The conditions were very close to the cavity’s final condition in a cryomodule.”

    3
    A cryomodule of International Linear Collider being tested at Fermilab

    In this integrated test, the fully dressed 1.3-gigahertz cavity’s quality factor was 3.1 x 1010 at 2 Kelvin and at a 16-megavolt-per-meter peak surface electric field. This Q exceeds LCLS-II’s goal of 2.7 x 1010 and far surpasses current state-of-the-art standards.

    “This quality factor is an extremely important step,” said Slava Yakovlev, SRF department head. “It’s a victory.”

    SLAC physicist Marc Ross, LCLS-II cryogenics systems manager, says he’s pleased with the results.

    “It’s definitely a victory,” Ross said. “These are some of the highest-quality-factor practical resonators ever built.”

    A fully dressed cavity is outfitted with all the components it will wear in the LCLS-II accelerator. This includes a titanium jacket filled with liquid helium chilled to 2 Kelvin, a temperature at which niobium is superconducting. It’s also furnished with power-providing couplers, cavity-squeezing tuners to control frequency, and magnetic shielding. These components add heat and can lower Q, so the team had to develop a way to carry this heat away and keep Q high.

    “This record Q is really the sum, the final point, of many years of research,” said Anna Grassellino, Fermilab Technical Division scientist who leads cavity testing and processing for LCLS-II. “It’s really a miracle of science and technology and engineering coming together and producing an unprecedented quality factor. It opens up a way for machines to operate much more efficiently at a much lower cost.”

    Grassellino led the Fermilab effort to apply the breakthrough technology, dubbed nitrogen doping, that helped achieve this record Q. It involves infusing nitrogen into a cavity’s inner niobium surface. Nitrogen doping and other Fermilab discoveries that led to this Q value, such as the removal of magnetic flux through rapid cooling, will become new standards for achieving highly efficient accelerators worldwide.

    “This is a critical milestone not only in LCLS-II design, but in other modern accelerator projects including our own project, PIP-II,” Yakovlev said.

    FNAL PIP-II Home
    PIP-II

    But there’s more to be done for LCLS-II.

    “We still need to show that the full cryomodule with eight cavities meets specifications,” Grassellino said. “There’s always a next step.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    Fermilab Campus

    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.

     
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