From SLAC Lab: “Work Begins on New SLAC Facility for Revolutionary Accelerator Science”

From SLAC Lab

June 11, 2018
Manuel Gnida

The goal: develop plasma technologies that could shrink future accelerators up to 1,000 times, potentially paving the way for next-generation particle colliders and powerful light sources.

The Department of Energy’s SLAC National Accelerator Laboratory has started to assemble a new facility for revolutionary accelerator technologies that could make future accelerators 100 to 1,000 times smaller and boost their capabilities.

The project is an upgrade to the Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science user facility that operated from 2011 to 2016.

SLAC FACET

FACET-II will produce beams of highly energetic electrons like its predecessor, but with even better quality.

These beams will primarily be used to develop plasma acceleration techniques, which could lead to next-generation particle colliders that enhance our understanding of nature’s fundamental particles and forces and novel X-ray lasers that provide us with unparalleled views of ultrafast processes in the atomic world around us.

FACET-II will be a unique facility that will help keep the U.S. at the forefront of accelerator science, said SLAC’s Vitaly Yakimenko, project director. “Its high-quality beams will enable us to develop novel acceleration methods,” he said. “In particular, those studies will bring us close to turning plasma acceleration into actual scientific applications.”

SLAC is upgrading its Facility for Advanced Accelerator Experimental Tests (FACET) – a test bed for new technologies that could revolutionize the way we build particle accelerators. FACET-II will use the middle third of the lab’s 2-mile-long linear accelerator (SLAC ground plan at top). It will send a beam of electrons (bottom, blue line) from the electron source (bottom left) to the experimental area (bottom right), where it will arrive with an energy of 10 billion electronvolts. The design allows for adding the capability to produce and accelerate positrons (bottom, red line) later. (Greg Stewart/SLAC National Accelerator Laboratory)

The DOE has now approved the $26 million project (Critical Decisions 2 and 3). The new facility, which is expected to be completed by the end of 2019, will also operate as an Office of Science user facility – a federally sponsored research facility for advanced accelerator research available on a competitive, peer-reviewed basis to scientists from around the world.

“As a strategically important national user facility, FACET-II will allow us to explore the feasibility and applications of plasma-driven accelerator technology,” said James Siegrist, associate director of the High Energy Physics (HEP) program of DOE’s Office of Science, which stewards advanced accelerator R&D in the U.S. for the development of applications in science and society. “We’re looking forward to seeing the groundbreaking science in this area that FACET-II promises, with the potential for significant reduction of the size and cost of future accelerators, including free-electron lasers and medical accelerators.”

Bruce Dunham, head of SLAC’s Accelerator Directorate, said, “Our lab was built on accelerator technology and continues to push innovations in the field. We’re excited to see FACET-II move forward.”

Surfing the Plasma Wake

The new facility will build on the successes of FACET, where scientists already demonstrated that the plasma technique can very efficiently boost the energy of electrons and their antimatter particles, positrons. In this method, researchers send a bunch of very energetic particles through a hot ionized gas, or plasma, creating a plasma wake for a trailing bunch to “surf” on and gain energy.

Researchers will use FACET-II to develop the plasma wakefield acceleration method, in which researchers send a bunch of very energetic particles through a hot ionized gas, or plasma, creating a plasma wake for a trailing bunch to “surf” on and gain energy. (Greg Stewart/SLAC National Accelerator Laboratory)

In conventional accelerators, particles draw energy from a radiofrequency field inside metal structures. However, these structures can only support a limited energy gain per distance before breaking down. Therefore, accelerators that generate very high energies become very long, and very expensive. The plasma wakefield approach promises to break new ground. Future plasma accelerators could, for example, unfold the same acceleration power as SLAC’s historic 2-mile-long copper accelerator (linac) in just a few meters.

Aerial view of SLAC’s 2-mile-long linac. The longest linear accelerator ever built, it produced its first particle beams in 1966 and has been the lab’s backbone for accelerator-driven science ever since. (SLAC National Accelerator Laboratory)

Researchers will use FACET-II for crucial developments before plasma accelerators can become a reality. “We need to show that we’re able to preserve the quality of the beam as it passes through plasma,” said SLAC’s Mark Hogan, FACET-II project scientist. “High-quality beams are an absolute requirement for future applications in particle and X-ray laser physics.”

The FACET-II facility is currently funded to operate with electrons, but its design allows adding the capability to produce and accelerate positrons later – a step that would enable the development of plasma-based electron-positron particle colliders for particle physics experiments.

Future particle colliders will require highly efficient acceleration methods for both electrons and positrons. Plasma wakefield acceleration of both particle types, as shown in this simulation, could lead to smaller and more powerful colliders than today’s machines. (F. Tsung/W. An/UCLA; Greg Stewart/SLAC National Accelerator Laboratory)

Another important objective is the development of novel electron sources that could lead to next-generation light sources, such as brighter-than-ever X-ray lasers. These powerful discovery machines provide scientists with unprecedented views of the ever-changing atomic world and open up new avenues for research in chemistry, biology and materials science.

Other science goals for FACET-II include compact wakefield accelerators that use certain electrical insulators (dielectrics) instead of plasma, as well as diagnostics and computational tools that will accurately measure and simulate the physics of the new facility’s powerful electron beams. Science goals are being developed with regular input from the FACET user community.

“The approval for FACET-II is an exciting milestone for the science community,” said Chandrashekhar Joshi, a researcher from the University of California, Los Angeles, and longtime collaborator of SLAC’s plasma acceleration team. “The facility will push the boundaries of accelerator science, discover new and unexpected physics and substantially contribute to the nation’s coordinated effort in advanced accelerator R&D.”

Fast Track to First Experiments

To complete the facility, crews will install an electron source and magnets to compress electron bunches, as well as new shielding, said SLAC’s Carsten Hast, FACET-II technical director. “We’ll also upgrade the facility’s control systems and install tools to analyze the beam properties.”

FACET-II will use one kilometer (one-third) of the SLAC linac – sending electrons from the source at one end to the experimental area at the other end – to generate an electron beam with an energy of 10 billion electronvolts that will drive the facility’s versatile research program.

FACET-II has issued its first call for proposals for experiments that will run when the facility goes online in 2020.

“The project team has done an outstanding job in securing DOE approval for the facility,” said DOE’s Hannibal Joma, federal project director for FACET-II. “We’ll now deliver the project on time for the user program at SLAC.”

SLAC’s Selina Green, project manager, said, “After two years of very hard work, it’s very exciting to see the project finally come together. Thanks to the DOE’s continued support we’ll soon be able to open FACET-II for groundbreaking new science.”

Members of SLAC’s FACET-II project team. From left: Nate Lipkowitz, Kevin Turner, Carsten Hast, Lorenza Ladao, Gary Bouchard, Vitaly Yakimenko, Martin Johansson, Selina Green, Glen White, Eric Bong, Jerry Yocky. Not pictured: Lauren Alsberg, Jeff Chan, Karl Flick, Mark Hogan, John Seabury. (Dawn Harmer/SLAC National Accelerator Laboratory)

For more information, please visit the website:

FACET-II Website

Press Office Contact:
Andy Freeberg
afreeberg@slac.stanford.edu
(650) 926-4359

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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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From University of Wisconsin Madison: “Strain game: Leveraging imperfections to create better-behaved quantum dots”

From University of Wisconsin Madison

May 17, 2018
Sam Million-Weaver
perspective@engr.wisc.edu

Postdoctoral scholar Anastasios Pateras adjust an X-Ray instrument used to detect previously unknown defects in quantum dots. Photo credit: Sam Million-Weaver.

Potentially paving the way toward advanced computers, lasers or optical devices, University of Wisconsin-Madison researchers have revealed new effects in tiny electronic devices called quantum dots.

In their work, published recently in the journal Nano Letters, the researchers developed and applied analysis methods that will help answer other challenging questions for developing electronic materials.

“We can now look at a set of structures that people couldn’t look at before,” says Paul Evans, professor of materials science and engineering at UW-Madison. “In these structures, there are new sets of crucial materials problems that we previously weren’t able to think about solving.”

The structures Evans and colleagues looked at are thousands of times narrower than single sheets of paper, and smaller than the dimensions of individual human cells. In those structures, quantum dots form inside very thin stacks of crystalline materials topped by an asymmetrical arrangement of flat, spindly, fingerlike metallic electrodes. Between the tips of those metallic fingers are small spaces that contain quantum dots.

Creating such precise structures and peering inside those tiny spaces is technically challenging, however, and quantum dots don’t always behave as expected.

Previous work by Evans’ collaborators at the Delft University of Technology in the Netherlands, who created and extensively studied the crystal stack structures, led to suspicions that the quantum dots were different in important ways from what had been designed.

Until now, measuring those differences wasn’t possible.

“Previous imaging approaches and the modeling weren’t allowing people to structurally characterize quantum dot devices at this tiny scale,” says Anastasios Pateras, a postdoctoral scholar in Evans’ group and the paper’s first author.

Pateras and colleagues pioneered a strategy for using beams of very tightly focused X-rays to characterize the quantum dot devices—and that hinged on a new method for interpreting how the X-rays scattered. Using their approach, they observed shifts in the spacing and orientation of atomic layers within the quantum dots.

“Quantum dots need to be close to perfect,” says Evans. “This small deviation from perfection is important.”

The team’s discovery indicates that the process of creating the quantum dots—laying down metallic electrodes atop a lab-grown crystal—distorts the material underneath slightly. This puckering creates strain in the material, leading to small distortions in the quantum dots. Understanding and exploiting this effect could help researchers create better-behaved quantum dots.

“Once you know these quantities, then you can design devices that take into account that structure,” says Evans.

Designs with those small imperfections in mind will be especially important for future devices where many thousands of quantum dots must all work together.

“This is going to be very relevant because, right now, there are multiple sources of decoherence quantum dots,” says Pateras.

The researchers now are developing an algorithm to automatically visualize atomic positions in crystals from X-ray scattering patterns, given that performing the necessary calculations by hand would likely be too time-consuming. Additionally, they are exploring how the techniques could add insight to other hard-to study structures.

The work was supported by the United States Department of Energy Basic Energy Sciences, Materials Sciences and Engineering (contract no. DE-FG02-04ER46147), the National Science Foundation Graduate Research Fellowship Program (grant no. DGE-1256259), and the Netherlands Organization of Scientific Research (NOW). Use of the Center for Nanoscale Materials and the Advanced Photon Source, both Office of Science user facilities, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (contract no. DE-AC02-06CH11357). Laboratory characterization at UW–Madison used instrumentation supported by the NSF through the UW–Madison Materials Research Science and Engineering Center (DMR-1121288 and DMR-1720415).

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In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

From SLAC Lab: “X-ray Laser Reveals Ultrafast Dance of Liquid Water”

From SLAC Lab

May 16, 2018
Water is more complicated than it seems. Now a study led by researchers at Stockholm University has probed the movements of its molecules on a timescale of millionths of a billionth of a second.

An illustration shows the “blurring” effect caused by water molecules moving during imaging with the X-ray laser. As the laser pulse gets longer, from left to right, the diffraction pattern produced by X-rays hitting the molecules changes (bottom row), reflecting the motion of the water molecules (top row). Experiments at SLAC’s LCLS X-ray laser were able to provide the timescale of the water dynamics by using pulses less than 100 millionths of a billionths of a second long. (Fivos Perakis/Stockholm University)

Water’s lack of color, taste and smell make it seem simple – and on a molecular level, it is. However, when many water molecules come together they form a highly complex network of hydrogen bonds. This network is believed to be responsible for many of the peculiar properties of liquid water, but its behavior is not yet fully understood.

Now researchers have probed the movements of molecules in liquid water that occur in less than 100 millionths of a billionth of a second, or femtoseconds. An international team led by researchers at Stockholm University carried out the experiments with the Linac Coherent Light Source (LCLS) X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory. They published their report this week in Nature Communications.

SLAC/LCLS

The study is the first to “photograph” water molecules on this timescale with a technique called ultrafast X-ray photon correlation spectroscopy, which bounces X-rays pulses off the molecules to produce a series of diffraction patterns. Varying the duration of the X-ray pulses essentially varies the exposure time, and any motion of the water molecules during an exposure will blur the resulting picture. By analyzing the blurring produced by different exposure times, the scientists were able to extract information about the molecular motion.

On this timescale, it was assumed that water molecules move randomly due to heat, behaving more like a gas than a liquid. However, the experiments indicate that the network of hydrogen bonds plays a role even on this ultrafast timescale, coordinating the motions of water molecules in an intricate dance, which becomes even more pronounced when water is “supercooled” below its normal freezing point.

“The key to understanding water on a molecular level is watching the changes of the hydrogen-bond network, which can play a major role in biological activity and life as we know it,” says Anders Nilsson, a professor at Stockholm University and former professor at SLAC.

Adds Stockholm University researcher Fivos Perakis, “It is a brand-new capability to be able to use X-ray lasers to see the motion of molecules in real time. This can open up a whole new field of investigations on these timescales, combined with the unique structural sensitivity of X-rays.”

The experimental results were reproduced by computer simulations, which indicate that the coordinated dance of water molecules is due to the formation of transient tetrahedral structures.

“I have studied the dynamics of liquid and supercooled water for a long time using computer simulations, and it is very exciting to finally be able to directly compare with experiments,” says Gaia Camisasca, a postdoctoral researcher at Stockholm University who performed the computer simulations for this study. “I look forward to seeing the future results that can come out from this technique, which can help improve the current water computer models.”

LCLS is a DOE Office of Science user facility. SLAC’s Thomas J. Lane, Sanghoon Song, Takahiro Sato, Marcin Sikorski, Andre Eilert, Trevor McQueen, Hirohito Ogasawara, Dennis Nordlund, Jake Koralek, Silke Nelson, Philip Hart, Roberto Alonso-Mori, Yiping Feng, Diling Zhu and Aymeric Robert contributed to this study, along with researchers from KTH Royal Institute of Technology in Stockholm and DESY in Hamburg.

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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.

From Imperial College London: “X-rays from tabletop lasers allows scientists to peer through the ‘water window’”

From Imperial College London

11 May 2018
Hayley Dunning

Studying the fleeting actions of electrons in organic materials will now be much easier, thanks to a new method for generating fast X-rays.

The technique means advanced measurements of fast reactions will now be possible in physics labs around the world, without having to wait to use expensive and scarce equipment. It could be used, for example, to study and improve light-harvesting technologies like solar panels and water splitters.

When ‘soft’ X-rays, beyond the range of ultraviolet light, strike an object, they are strongly absorbed by some kinds of atoms and not others. In particular, water is transparent to these X-rays, but carbon absorbs them, making them useful for imaging organic and biological materials.

However, a challenge has been to generate very fast soft X-rays. Creating pulses of X-rays that only last one thousandth of a millionth of a millionth of a second would allow researchers to image the extremely quick motions of electrons, crucial for determining how charge travels and reactions occur.

Smallest and fastest reaction steps

Fast soft X-rays have been created with large facilities, such as multi-billion dollar costing free-electron lasers, but now a research team from Imperial College London have generated fast and powerful fast soft X-ray pulses using standard laboratory lasers.

The method, which can produce bright soft X-ray pulses that last hundreds of attoseconds (quintillionths of a second), is published today in Science Advances.

With the new technique, researchers will be able to watch the movement of electrons on their natural timescale, giving them a dynamic picture of the smallest and fastest reaction steps.

Senior author Professor Jon Marangos, from the Department of Physics at Imperial, said: “The strength of this technique is that it can be used by many physics labs around the world with lasers they already have installed.

“This discovery will allow us to make measurements at extreme timescales for the first time. We are at the frontiers of what we can measure, seeing faster-than-ever processes important for science and technology.”

Generating X-rays

Generating X-rays in a lab requires exciting atoms until they release photons – particles of light. Normally, atoms in a long, dispersed cloud are excited in sequence so that they emit photons in ‘phase’, meaning they add up and create a stronger X-ray pulse. This is known as phase matching.

But when trying to generate soft X-rays this way, effects in the cloud of atoms strongly defocus the laser, disrupting phase matching.

Instead, the team discovered that they needed a thin, dense cloud of atoms and short laser pulses. With this setup, while the photons could not stay in phase over a long distance, they were still in phase over a shorter distance and for a short time. This led to unexpectedly efficient production of the short soft X-ray pulses.

The team further measured and simulated the exact effects that cause high harmonic generation in this situation, and from this were able to predict the optimum laser conditions for creating a range of X-rays.

Lead researcher Dr Allan Johnson, from the Department of Physics at Imperial, said: “We’ve managed to look inside what was before the relatively black-box of soft X-ray generation, and use that information to build an X-ray laser on a table that can compete with football-field spanning facilities. Knowledge is quite literally power in this game.”

Improving solar technologies

The team at Imperial plan to use the technique to study organic polymer materials, in particular those that harvest the Sun’s rays to produce energy or to split water. These materials are under intense study as they can provide cheaper renewable energy.

However, many currently used materials are unstable or inefficient, due to the action of electrons that are excited by light. Closer study of the fast interactions of these electrons could provide valuable insights into methods for improving solar cells and catalysts.

• ‘High-Flux Soft X-ray Harmonic Generation from Ionization-Shaped Few-Cycle Laser Pulses’ by Allan S. Johnson, Dane R. Austin, David A. Wood, Christian Brahms, Andrew Gregory, Konstantin B. Holzner, Sebastian Jarosch, Esben W. Larsen, Susan Parker, Christian S. Strüber, Peng Ye, John W. G. Tisch, and Jon P. Marangos is published in Science Advances.

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Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

From DESY: “Freeze-framing nanosecond movements of nanoparticles”

From DESY

2018/05/03
No writer credit

New method allows to monitor fast movements at hard X-ray lasers.

A team of scientists from DESY, the Advanced Photon Source APS and National Accelerator Laboratory SLAC, both in the USA, have developed and integrated a new method for monitoring ultrafast movements of nanoscopic systems.

Argonne APS

SLAC LCLS

With the light of the X-ray laser LCLS at the research center SLAC in California, they took images of the movements of nanoparticles taking only the billionth of a second (0,000 000 001 s).

SLAC LCLS

In their experiments now published in the journal Nature Communications they overcame the slowness of present-day two-dimensional X-ray detectors by splitting individual laser flashes of LCLS, delaying one half of it by a nanosecond and recording a single picture of the nanoparticle with these pairs of X-ray pulses. The tunable light splitter for hard X-rays which the scientists developed for these experiments enables this new technique to monitor movements of nanometer size fluctuations down to femtoseconds and at atomic resolution. For comparison: modern synchrotron radiation light sources like PETRA III at DESY can typically measure movements on millisecond timescales.

DESY Petra III interior

Scheme of the experiment: An autocorrelator developed at DESY splits the ultrashort X-ray laser pulses into two equal intensity pulses which arrive with a tunable delay at the sample. The speckle pattern of the sample is collected in a single exposure of the 2-D detector (picture: W. Roseker/DESY).

he intense light flashes of X-ray lasers are coherent which means that the waves of the monochromatic laser light propagate in phase to each other. Diffracting coherent light by a sample usually results in a so-called speckle diffraction pattern showing apparently randomly ordered light spots. However, this speckle is also a map of the sample arrangement, and movements of the sample constituents result in a different speckle pattern.

For their experiments the researchers developed a special optical setup – a so-called optical autocorrelator – capable of splitting 100 femtosecond long XFEL pulses into two sub-pulses, deviate them into separated detours and recombining their paths with a tunable time delay between zero and a few nanoseconds. These pairs of XFEL pulses hit the sample with the tuned delay, spotting the sample´s structure at the two exposure times. The sum of both speckle pictures was recorded by a two-dimensional photon detector within one exposure time. The trick: If the constituents of the sample move during the two illuminations, the speckle pattern changes, resulting in an integrated picture of less contrast at the detector. The contrast is a measure on how strong the photon intensity varies on the detector. However, the intensity and especially the intensity difference measured at the detector are very weak. In their experiments the researchers had to work with only some 1000 detected photons on the one-million-pixels size detector.

“Such type of experiments has been done for much slower movements of nanoparticles at storage ring light sources,” explains first author Wojciech Roseker from DESY. “But now, the high coherence and intensity of the X-ray laser light at XFELs open up the opportunity to get pictures bright enough to provide reasonable information about quick movements in the nanosecond to femtosecond regime.”

In their work the researchers around Roseker used a suspension of two nanometers size gold particles undergoing Brownian motion. The experiment was in perfect agreement with the theoretical predictions thus proving not only the performance of the autocorrelator setup but also the validity of the data analysis procedure, demonstrating the first successful experiment of this kind. One of the challenges in this experiment, carried out at the XCS experimental station at LCLS, was to autocorrelate thousands of extremely weak double shot 2D images which was achieved with the help of a newly developed maximum likelihood analysis technique.

“This experiment paves the way to dynamics experiments of materials on atomic length and femtosecond-nanosecond timescales,” explains Gerhard Grübel, head of the DESY FS-CXS group. “Split-pulse X-ray Photon Correlation Spectroscopy (XPCS) can potentially track atomic scale fluctuations in liquid metals, multi-scale dynamics in water, heterogeneous dynamics about the glass transition, and atomic scale surface fluctuations.” Additionally, time-domain XPCS at FEL sources, especially at the European XFEL, is well suited for studying fluctuations in non-equilibrium processes that go beyond time-averaged structural descriptions.

DESY European XFEL

European XFEL

This will allow the elucidation of dynamics of ultrafast magnetization processes and can address open questions concerning photo-induced phonon dynamics and phase transitions.

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DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

From European XFEL: “Entering the realm of attosecond X-ray science”

European XFEL

European XFEL

2018/04/13

New methods for producing and characterizing attosecond X-ray pulses.

Ultrashort X-ray pulses (pink) at the Linac Coherent Light Source ionize neon gas at the center of a ring of detectors. An infrared laser (orange) sweeps the outgoing electrons (blue) across the detectors with circularly polarized light. Scientists read data from the detectors to learn about the time and energy structure of the pulses, information they will need for future experiments. Copyright: Terry Anderson / SLAC National Accelerator Laboratory.

SLAC/LCLS

European XFEL produces unfathomably fast X-ray pulses that are already being used by scientists to explore the unchartered territory of the atomic and molecular cosmos. Intense X-ray pulses lasting only a few femtoseconds – or a few millionths of a billionth of a second – are being used to reveal insights into the dynamics of chemical reactions and the atomic structures of biological molecules such as proteins and viruses. And while there is much more to discover in this femtosecond time range, scientists are already looking to take European XFEL to the next time dimension, exploring reactions and dynamics that occur on an even briefer time scale – the attosecond time regime.

If you leave the shutter of your camera open for too long while photographing a race, the resulting pictures will only be a smear of colour. To capture clear and sharp images of the athletes’ movements you need to make sure the shutter is only open for the shortest time; in fact the best shutter speed to capture a clear snapshot of the runners’ legs frozen in action would be faster than the time the runner needed to move their legs. Good light conditions help too to make sure your photos are sharp and in focus. And so it is as scientists attempt to take snapshots of some of nature’s fastest processes such as the movements of electrons within atoms and molecules. To capture snapshots of these movements in action we need pulses of intense X-rays that reflect the timescale on which these reactions occur – and these reactions can occur even down to the attosecond timescale.

XLEAP

Attosecond X-ray science is expected to allow scientists to delve even deeper into ultrafast chemical and molecular processes and the tiniest details of our world than already possible. But how to produce X-ray flashes that are even shorter than the already ultrafast femtosecond flashes? One of the methods currently being explored by scientists is ‘X-ray Laser-Enhanced Attosecond Pulse generation’ (XLEAP). The method, being developed at the SLAC National Accelerator Laboratory in the USA, is expected to be possible with only moderate modifications to the layout of existing FEL facilities. If successful, the usually chaotic time and energy structure of XFEL (X-ray Free-Electron Laser) pulses, consisting of a sequence of many intensity spikes based on the so-called SASE (Self-Amplification by Spontaneous Emission) principle, can be reliably narrowed down to one single, coherent intensity spike of only few hundreds of attoseconds. In a recent review article in the Journal of Optics, European XFEL scientists propose how the XLEAP method might be implemented at the SASE 3 branch of the facility, eventually providing attosecond pulses for experiments.

European XFEL scientist Markus Ilchen working on the original angle resolving time-of-flight spectrometer at PETRA III, DESY. Copyright: European XFEL

DESY Petra III

DESY Petra III interior

Angular Streaking diagnostics

While the free-electron laser technology is almost ready to provide attosecond pulses, another hurdle is to actually prove and characterize their existence. Experiments to date at XFEL facilities have often relied on indirect measurements and simulations of X-ray pulses to calibrate results. However, only with detailed information from direct measurements of the exact time and energy structure of each X-ray pulse, can X-ray science enter a new era of time resolved and coherence dependent experiments.

With this in mind, a novel experimental approach was conceived as part of an international collaboration including scientists from SLAC, Deutsches Elektronen-Synchrotron (DESY), European XFEL, the Technical University of Munich, University of Kassel, University of Gothenburg, University of Bern, University of Colorado, University of the Basque Country in Spain, and Lomonosov Moscow State University in Russia. In a study published in the journal Nature Photonics, the international groupdemonstrated the capability of a so-called ‘angular streaking’ method to characterize the time and energy structure of X-ray spikes. The scientists used the shortest pulses available at the Linac Coherent Light Source (LCLS) at SLAC in the USA for their experiment. Using the new angular streaking diagnostic method, millions of pulses, each of a few femtoseconds in length, were successfully captured and analyzed. “Being able to get the precise information about the energy spectrum, as well as the time and intensity structure of every single X-ray pulse is unprecedented” explains Markus Ilchen from the Small Quantum Systems group at European XFEL, one of the principal investigators of this work. “This is really one of the holy grails of FEL diagnostics” he adds enthusiastically.

The new angular streaking technique works by using the rotating electrical field of intense circularly polarized optical laser pulses to extract the time and energy structure of the XFEL pulses. Interaction with the XFEL pulse causes atoms to eject electrons which are then strongly kicked around by the surrounding laser field. Information about the electron’s exact time of birth is not only imprinted in the energy of the electron but also in the ejecting angle. This all provides a ‘clock’ by which to sort the resulting experimental data. Pulses generated by the SASE process, as implemented at European XFEL and SLAC, are intrinsically variable and chaotic. Some of the recorded pulses during the experiment at SLAC were, therefore, already single spikes in the attosecond regime which then were fully characterized for their time-energy structure.

Angle resolving time-of-flight spectrometer

An illustration of the ring-shaped array of 16 individual detectors arranged in a circle like numbers on the face of a clock. An X-ray laser pulse hits a target at the center and sets free electrons that are swept around the detectors. The location, where the electrons reach the “clock,” reveals details such as the variation of the X-ray energy and intensity as a function of time within the ultrashort pulse itself. Copyright: Frank Scholz & Jens Buck, DESY.

he underlying spectroscopic method is based on an angle resolving time-of-flight spectrometer setup consisting of 16 individual spectrometers aligned in a plane perpendicular to the XFEL beam. These are used to characterize the X-ray beam by correlating the electrons’ energies and their angle dependent intensities. An adapted version of the spectrometer setup originally developed at the PETRA III storage ring at DESY, was built in the diagnostics group of European XFEL and provided for the beamtime at SLAC.

At European XFEL the diagnostic goal is that scientists will eventually be able to use the method to extract all information online during their experiments and correlate and adjust their data analysis accordingly. Furthermore, although the method has so far only been designed and tested for soft X-rays, Ilchen and his colleagues are optimistic that it could also be used for experiments using hard X-rays. “By reducing the wavelength of the optical laser, we could even resolve the few hundreds of attosecond broad spikes of the hard X-ray pulses here at the SASE 1 branch of European XFEL” Ilchen says.

Time-resolved experiments

During the experiment at SLAC the scientists also showed that it was even possible to use the acquired data to select pulses with exactly two intensity spikes with a variable time delay between them. This demonstrates the capability of FELs to enable time-resolved X-ray measurements attosecond to few femtosecond delay. “By determining the time duration and distance of those two spikes, we can sort our data for matching pulse properties and use them to understand how certain reactions and processes have progressed on an attosecond timescale” explains Ilchen. “Since our method gives us precise information about the pulse structure, we will be able to reliably reconstruct what is happening in our samples by producing a sequence of snapshots, so that much like a series of photographs pasted together makes a moving film sequence, we can make ‘movies’ of the reactions” he adds.

From principle to proof

Due to the limited pulse repetition rate currently available at most XFELs, however, moving from a proof-of-principle experiment to actually using specifically structured pulses for so-called pump-probe experiments requires a large leap of the imagination. European XFEL, however, already provides more pulses per second than other similar facilities, and will eventually provide 27,000 pulses per second, making the dream of attosecond time-resolved experiment a real possibility. “Although, currently, no machine in the world can provide attosecond X-ray pulses with variable time delay below the femtosecond regime in a controlled fashion,” says Ilchen, “the technologies available at European XFEL in combination with our method, could enable us to produce so much data that we can pick the pulse structures of interest and sort the rest out while still getting enough statistics for new scientific perspectives.”

Further reading:

News from SLAC – “Tick, Tock on the ‘Attoclock’: Tracking X-Ray Laser Pulses at Record Speeds”

Overview of options for generating high-brightness attosecond x-ray pulses at free-electron lasers and applications at the European XFEL
S. Serkez et al., Journal of Optics, 9 Jan 2018 doi:10.1088/2040-8986/aa9f4f

See the full article here .

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XFEL Tunnel

XFEL Gun

The Hamburg area will soon boast a research facility of superlatives: The European XFEL will generate ultrashort X-ray flashes—27 000 times per second and with a brilliance that is a billion times higher than that of the best conventional X-ray radiation sources.

The outstanding characteristics of the facility are unique worldwide. Started in 2017, it will open up completely new research opportunities for scientists and industrial users.

From SLAC: “Tick, Tock on the ‘Attoclock:’ Tracking X-Ray Laser Pulses at Record Speeds”

SLAC Lab

April 4, 2018
Amanda Solliday
Angela Anderson

In this illustration, ultrashort X-ray pulses (pink) at the Linac Coherent Light Source ionize neon gas at the center of a ring of detectors.

SLAC/LCLS

An infrared laser (orange) sweeps the outgoing electrons (blue) across the detectors with circularly polarized light. Scientists read data from the detectors to learn about the time and energy structure of the pulses, information they will need for future experiments. (Terry Anderson / SLAC National Accelerator Laboratory)

When it comes to making molecular movies, producing the world’s fastest X-ray pulses is only half the battle. A new technique reveals details about the timing and energy of pulses that are less than a millionth of a billionth of a second long, which can be used to probe nature’s processes at this amazingly fast attosecond timescale.

To catch chemistry in action, scientists at the Department of Energy’s SLAC National Accelerator Laboratory use the shortest possible flashes of X-ray light to create “molecular movies” that capture the motions of atoms in chemical reactions and reveal new details about the most fundamental processes in nature.

Future experiments at the Linac Coherent Light Source (LCLS), SLAC’s X-ray free-electron laser, will use pulses that last just attoseconds (billionths of a billionth of a second). Such experiments will be even more powerful because they’ll be able to detect the motions of electrons within molecules during chemical reactions. However, to design such ultrafast experiments, researchers need meticulous measurements of the X-ray pulses so they can use that information to interpret the data they collect on the samples they study.

Now an international team, including SLAC scientists, has created an X-ray “attoclock” that lets them analyze X-ray pulses on the attosecond timescale of electron motions.

“Using this method, we can resolve details of the pulses in the attosecond domain for the first time,” says Ryan Coffee, a senior scientist at LCLS and the Stanford PULSE Institute and a principal investigator on the team. “This paves the way for X-ray free-electron laser science at a timescale that is key to understanding physical chemistry.”

The team’s research was published in Nature Photonics on March 5.

Timekeeping in Attoseconds

An illustration of the ring-shaped array of 16 individual detectors arranged in a circle like numbers on the face of a clock. An X-ray laser pulse hits a target at the center and sets free electrons that are swept around the detectors. The location, where the electrons reach the “clock,” reveals details such as the variation of the X-ray energy and intensity as a function of time within the ultrashort pulse itself. (Frank Scholz & Jens Buck / DESY)

The term “attoclock” was coined by Swiss physicist Ursula Keller, who first demonstrated a technique to study attosecond processes with circularly polarized light 10 years ago. However, the LCLS version is the first one designed to measure individual X-ray pulses, one by one.

It consists of a ring of detectors arranged like numbers on the face of a clock. When an X-ray pulse hits a target at the center of the clock, it knocks electrons out of the target’s atoms. Those electrons are hit by circularly polarized laser light that whirls the electrons around the ring before they land on one of the detectors. The position of that detector – the number on the clock face – tells scientists how much energy the X-ray pulse contained and when exactly it hit the target.

“It’s like reading a watch,” Coffee says. “An electron may strike a detector positioned at one o’clock or three o’clock or anywhere around the clock face. We can tell from where it hits exactly when it was generated by the X-ray pulse.”

In an experiment designed to test the technique, the researchers hit neon gas with an attosecond X-ray pulse and then read which of the 16 detectors arrayed around the attoclock the freed electrons hit.

“In coming up with this technique, we combined ideas from different fields,” says principal investigator Wolfram Helml, then a Marie Curie research fellow at SLAC and the Technical University of Munich and now at the Ludwig-Maximilian University of Munich. “For our purposes, it just made sense to combine the circularly polarized light used in the original attoclock with a ring-shaped detector that has been used in other kinds of experiments.”

Finding the True Colors

The technique will be especially important for pump-probe experiments, in which a molecule is first excited with a “pump” pulse and then analyzed by a second “probe” pulse to see how it reacted.

As short as they are, these pulses can contain many different colors or wavelengths. “The color can also vary widely from pulse to pulse, and our technique can sift through the pulses, finding those that are interesting for the experiment,” Coffee says, noting the importance that such sifting will have for the data deluge expected when an upgrade to the X-ray laser, LCLS-II, comes online a couple years from now.

SLAC/LCLS II projected view

With pulses that arrive up to a million times per second, LCLS-II will produce as much data in a few minutes as LCLS currently collects in a month.

“For instance, only a certain color may excite a molecule when it is ‘pumped,’” Helml said. “With the attoclock we can see what part of the pulse is actually exciting the molecule because we know exactly when particular colors of light arrive. This lets us pinpoint more precisely when changes occur in the molecule as a result of the interaction with light.”

What’s more, scientists can potentially excite individual elements in separate parts of the molecule at the same time using different colors of X-rays.

“With this technique we could look within a single molecule at the interplay between atoms. For example, what’s going on with an oxygen atom and how might that affect the chemical environment surrounding a nearby nitrogen atom?” Helml says. “With that level of detail, we can discern completely new chemical behavior.”

Progress in Motion

The attoclock team is now working on a proposal to build more refined detectors.

“With the next detector, we are aiming to precisely identify a broader spectrum of energies,” Coffee says. “This will be an important feature for our upgraded X-ray laser, LCLS-II, which will produce pulses with an even wider energy range and more multi-color flexibility than our current machine.”

This is one of several ideas being tested at SLAC to give scientists detailed information about attosecond pulses. Two other teams are building similar systems with different types of detectors, including one at LCLS and PULSE that recently published a study in Optics Express.

The international team on the Nature Photonics study also included scientists from Deutsches Elektronen-Synchrotron (DESY) and the European X-ray Free-electron Laser (Eu-XFEL), both in Germany, who also provided the unique ring-shaped detector; University of Kassel in Germany; University of Gothenburg in Sweden; University of Bern in Switzerland; University of Colorado at Boulder; University of the Basque Country in Spain; and Lomonosov Moscow State University in Russia.

LCLS is a DOE Office of Science user facility.

See the full article here .

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

From LBNL: “News Center COSMIC Impact: Next-Gen X-ray Microscopy Platform Now Operational”

Berkeley Lab

March 21, 2018

A next-generation X-ray beamline now operating at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) brings together a unique set of capabilities to measure the properties of materials at the nanoscale.

Called COSMIC, for Coherent Scattering and Microscopy, this X-ray beamline at Berkeley Lab’s Berkeley Lab’s Advanced Light Source (ALS) allows scientists to probe working batteries and other active chemical reactions, and to reveal new details about magnetism and correlated electronic materials.

From left to right: Advanced Light Source scientists Tony Warwick, Sujoy Roy, and David Shapiro at the COSMIC beamline. (Credit: Lori Tamura/Berkeley Lab)

LBNL/ALS

COSMIC has two branches that focus on different types of X-ray experiments: one for X-ray imaging experiments and one for scattering experiments. In both cases, X-rays interact with a sample and are measured in a way that provides, structural, chemical, electronic, or magnetic information about samples.

The beamline is also intended as an important technological bridge toward the planned ALS upgrade, dubbed ALS-U, that would maximize its capabilities.

Now, after a first-year ramp-up during which staff tested and tuned its components, the scientific results from its earliest experiments are expected to get published in journals later this year.

A study published earlier this month in the journal Nature Communications, based primarily on work at a related ALS beamline, successfully demonstrated a technique known as ptychographic computed tomography that mapped the location of reactions inside lithium-ion batteries in 3-D. That experiment tested the instrumentation that is now permanently installed at the COSMIC imaging facility.

A next-generation X-ray beamline now operating at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) brings together a unique set of capabilities to measure the properties of materials at the nanoscale.

Called COSMIC, for Coherent Scattering and Microscopy, this X-ray beamline at Berkeley Lab’s Berkeley Lab’s Advanced Light Source (ALS) allows scientists to probe working batteries and other active chemical reactions, and to reveal new details about magnetism and correlated electronic materials.

COSMIC has two branches that focus on different types of X-ray experiments: one for X-ray imaging experiments and one for scattering experiments. In both cases, X-rays interact with a sample and are measured in a way that provides, structural, chemical, electronic, or magnetic information about samples.

The beamline is also intended as an important technological bridge toward the planned ALS upgrade, dubbed ALS-U, that would maximize its capabilities.

Now, after a first-year ramp-up during which staff tested and tuned its components, the scientific results from its earliest experiments are expected to get published in journals later this year.

A study published earlier this month in the journal Nature Communications, based primarily on work at a related ALS beamline, successfully demonstrated a technique known as ptychographic computed tomography that mapped the location of reactions inside lithium-ion batteries in 3-D. That experiment tested the instrumentation that is now permanently installed at the COSMIC imaging facility.

“This scientific result came out of the R&D effort leading up to COSMIC,” said David Shapiro, a staff scientist in the Experimental Systems Group (ESG) at Berkeley Lab’s ALS and the lead scientist for COSMIC’s microscopy experiments.

That result was made possible by ALS investments in R&D, and collaborations with the University of Illinois at Chicago and with Berkeley Lab’s Center for Advanced Mathematics for Energy Research Applications (CAMERA), he noted.

X-rays strike a scintillator material at the COSMIC beamline, causing it to glow. (Credit: Simon Morton/Berkeley Lab)

“We aim to provide an entirely new class of tools for the materials sciences, as well as for environmental and life sciences,” Shapiro said. Ptychography achieves spatial resolution finer than the X-ray spot size by phase retrieval from coherent diffraction data, and “The ALS has done this with world-record spatial resolution in two and now three dimensions,” he added.

The ptychographic tomography technique that researchers used in this latest study allowed them to view the chemical states within individual nanoparticles. Young-Sang Yu, lead author of the study and an ESG scientist, said, “We looked at a piece of a battery cathode in 3-D with a resolution that was unprecedented for X-rays. This provides new insight into battery performance both at the single-particle level and across statistically significant portions of a battery cathode.”

COSMIC is focused on a range of “soft” or low-energy X-rays that are particularly well-suited for analysis of chemical composition within materials

Ptychographic tomography can be particularly useful for looking at cellular components as well as batteries or other chemically diverse materials in extreme detail. Shapiro said that the X-ray beam at COSMIC is focused to a spot about 50 nanometers (billionths of a meter) in diameter; however, ptychography can enhance the spatial resolution routinely by a factor of 10 or more. The current work was performed with a 120-nanometer beam that achieved a 3-D resolution of about 11 nanometers.

COSMIC’s X-ray beam is also brighter than the ALS beamline that was used to test its instrumentation, and it will become even brighter once ALS-U is complete. This brightness can translate to an even higher nanoscale resolution, and can also enable far more precision in time-dependent experiments.

Making efficient use of this brightness requires fast detectors, which are developed by the ALS detector group. The current detector can operate at a data rate of up to 400 megabytes per second and can now generate a few terabytes of data per day – enough to store about 500 to 1,000 feature-length movies. Next-generation detectors, to be tested shortly, will produce data 100 times faster.

“We are expecting to be the most data-intensive beamline at the ALS, and an important component of COSMIC is the development of advanced mathematics and computation able to quickly reconstruct information from the data as it is collected,” Shapiro said.

To develop these tools COSMIC coupled with CAMERA, which was created to bring state-of-the-art mathematics and computing to DOE scientific facilities.

CAMERA Director James Sethian said, “Building real-time advanced algorithms and the high-performance ptychographic reconstruction code for COSMIC has been a highly successful multiyear effort between mathematicians, computer scientists, software engineers, software experts, and beamline scientists.”

The code the team developed to improve ptychographic imaging at COSMIC, dubbed SHARP, is now available to all light sources across the DOE complex. For COSMIC, the SHARP code runs on a dedicated graphics processing unit (GPU) cluster managed by Berkeley Lab’s High Performance Computing Services.

Besides ptychography, COSMIC is also equipped for experiments that use X-ray photon correlation spectroscopy, or XPCS, a technique that is useful for studying fluctuations in materials associated with exotic magnetic and electronic properties.

COSMIC enables scientists to see such fluctuations occurring in milliseconds, or thousandths of a second, compared to time increments of multiple seconds or longer at predecessor beamlines. A new COSMIC endstation with applied magnetic field and cryogenic capabilities is now being built, with early testing set to begin this summer.

Scientists have already used COSMIC’s imaging capabilities to explore a range of nanomaterials, battery anode and cathode materials, cements, glasses, and magnetic thin films, Shapiro said.

“We’re still in the mode of learning and tuning, but the performance is fantastic so far,” he said. He credited the ALS crew, led by ESG scientist Tony Warwick, for working quickly to bring COSMIC up to speed. “It’s pretty remarkable to get to such high performance in such a short amount of time.”

The ALS is a DOE Office of Science User Facility. Development and deployment of the COSMIC beamline was supported by the DOE Office of Science.

See the full article here .

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A U.S. Department of Energy National Laboratory Operated by the University of California

From STFC: “UK joins World Leading X-Ray Laser Facility”

STFC

3.19.18
Jake Gilmore
STFC Media Manager
07970994586

The UK has today become the latest member state of the European XFEL, the international research facility that is home to the world’s largest X-ray laser.

DESY European XFEL

European XFEL

European XFEL

European XFEL Campus

Sited in Germany the European XFEL is capable of generating extremely intense X-ray laser flashes that offer new research opportunities for scientists across the world. Its range of capabilities include enabling researchers to take three-dimensional “photos” of the nanoworld, “film” chemical reactions as they happen and study processes such as those that occur deep inside planets.

In a ceremony at the British Embassy in Berlin, representatives of the UK government and the other contract parties, including the German federal government, signed the documents to join the European XFEL Convention. The UK is European XFEL’s twelfth member state. The UK’s contribution will amount to 26million Euro, or about 2% of the total construction budget of 1.22 billion Euro (both in 2005 prices) and an annual contribution of about 2% to the operation budget. The UK will be represented in European XFEL by the Science and Technology Facilities Council (STFC) as shareholder.

UK Science Minister Sam Gyimah said:

“The incredible XFEL laser will help us better understand life threatening diseases by using one of the world’s most powerful X-ray machines. Working with our international partners, the super-strength laser will help develop new medical treatments and therapies, potentially saving thousands of lives across the world.

“Through our modern Industrial Strategy we are investing an extra £4.7 billion into research and development. I am determined that we continue to secure our position as being a world-leader in science, research and innovation and I can’t wait to see the results that come from our participation in this extraordinary project.”

Although not an official shareholder until today the UK has been involved with XFEL since 2008 through both collaboration on technology and the two XFEL User Consortia. The first advanced detector to be installed at the European XFEL, the Large Pixel Detector (LPD), a cutting-edge X-ray “camera” capable of capturing images in billionths of a second, was developed and built by STFC. The LPD was installed mid-2017 and is now operational at the instrument for Femtosecond X-ray Experiments (FXE) at European XFEL.

In addition the STFC Central Laser Facility, based at Rutherford Appleton Laboratory near Oxford in the UK is currently building a nanosecond high energy laser for the High Energy Density (HED) instrument at European XFEL. This new “Dipole” laser will be used to recreate the conditions found within stars.

Dr Brian Bowsher, Chief Executive of STFC, said:

“As the UK becomes a full member of XFEL it opens up areas of research for British scientists at the atomic, molecular and nanoscale level that are currently inaccessible. This signing today reinforces our continued strategy to ensure UK science remains at the very forefront of global research by collaborating with the best scientists in the world and using the best facilities.

The capabilities offered by XFEL are already opening up entirely new scientific opportunities and this is a very important day for both UK science and STFC. Building on the contributions already made to XFEL by both STFC research and engineering staff and other UK researchers, I look forward with immense interest to see what my fellow UK research colleagues and the XFEL team will discover in the coming years”.

The UK has also developed a training facility at the Diamond Light Source on the Harwell campus in Oxfordshire for British scientists. The UK XFEL life sciences hub will enable users to fully prepare for their experiments with XFELs.

Chair of the European XFEL Council Professor Martin Meedom Nielsen who was present at the signing said:

“All member states are very happy that the United Kingdom now officially joins the European XFEL. The UK science community has been very active in the project since the very beginning, and their contribution of ideas and know-how has always been highly appreciated. Together, we will maintain and develop the European XFEL as a world leading facility for X-ray science.”

See the full article here .

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STFC Hartree Centre

Helping build a globally competitive, knowledge-based UK economy

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

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

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

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

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

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

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

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

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

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

From LLNL: “Earth’s core metals react well to electrons”

Lawrence Livermore National Laboratory

March 1, 2018

Anne M Stark
stark8@llnl.gov
925-422-9799

LLNL scientists discovered that at the thermodynamic conditions in Earth’s core, metals such as iron and nickel become electronegative and attract electrons. Image by Adam Connell/TID.

At temperatures and pressures found on Earth’s surface, metallic elements are electropositive and lose their valence electrons to form positively charged cations. Metals have free electrons that naturally form compounds with electronegative elements. For example, iron reacts with oxygen to form Fe2O3 – commonly referred to as rust.

In contrast, noble gas elements (NGEs), such as argon, neon and xenon — considered the most chemically inert elements – show very little reactivity with other elements.

However, in the Earth’s core, the reaction of metals with NGEs is quite different. Lawrence Livermore National Laboratory (LLNL) scientists, in collaboration with researchers at the University of Saskatchewan (UoS), the Carnegie Geophysical Laboratory (GL) and the University of Chicago, challenged this basic chemical phenomenon by examining the possible reaction between iron and nickel with xenon at thermodynamic conditions like those found in Earth’s core. Using synchrotron X-ray diffraction and Raman spectroscopy diagnostics in concert with first principles calculations, they discovered that it is possible to create stable xenon iron/nickel intermetallic compounds at Earth-core thermodynamic conditions. The experimental team used a natural iron meteorite, which fell on the Sikhote-Alin mountains in Russia, as a proxy to Earth’s core composition.

The research is published in the Feb. 28 edition of Physical Review Letters.

“We targeted iron/nickel-xenon reactions at pressures greater than 2 million times Earth’s atmospheric (surface) pressure and temperatures above 2000 Kelvin to simulate thermodynamic conditions representative of Earth’s core. Our aim was to solve the missing xenon paradox, that is xenon depletion in Earth’s atmosphere,” explained lead author, Elissaios (Elis) Stavrou, an LLNL physicist.

“In spite of our intentions, Elis and I were floored when, at the X-ray beamline [Advanced Photon Source, beamline GSECARS.], a clear signature of a reaction between iron and nickel with xenon was signaled by the diffraction pattern,” added LLNL physical chemist Joe Zaug.

ANL/APS

Heavy NGEs like xenon are known to react with strong electronegative elements, such as halogens; however, as Stavrou added: “This is the first experimental evidence of a noble gas element reacting with a metal.”

If this discovery were not enough, a transformative process was found to attribute the process where xenon reacted with metallic elements. Calculations by UoS and GL theorists Yansun Yao and Hanyu Liu revealed that at these conditions, iron and nickel metals become extraordinarily electronegative and attracted electrons away from xenon.

“Amazing,” Zaug said, “The metals effectively became halogen-like under the Earth-core conditions we created in the laboratory.”

The results indicate the changing chemical properties of elements under extreme conditions where elements, which are electropositive at ambient conditions, become electronegative. “A novel periodic table is needed to understand the changing chemical properties of elements under extreme thermodynamic conditions. There are many more systems and paradoxes to resolve. We look forward to writing new chapters about extreme physicochemical phenomena,” Stavrou said.

Researchers contributing to the work include Yansun Yao of University of Saskatchewan, Alexander Goncharov, Sergey Lobanov and Hanyu Liu of Geophysical Laboratory and Vitali Prakapenka and Eran Greenberg of the Advanced Photon Source/ University of Chicago.

This work was partially funded by a Laboratory Directed Research and Development Program project.

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Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security Administration

LLNL/NIF