Superconducting X-ray laser reaches operating temperature colder than outer space

The facility, LCLS-II, will soon sharpen our view of how nature works on ultrasmall, ultrafast scales, impacting everything from quantum devices to clean energy.

Nestled 30 feet underground in Menlo Park, California, a half-mile-long stretch of tunnel is now colder than most of the universe. It houses a new superconducting particle accelerator, part of an upgrade project to the Linac Coherent Light Source (LCLS) X-ray free-electron laser at the Department of Energy’s SLAC National Accelerator Laboratory.

Crews have successfully cooled the accelerator to minus 456 degrees Fahrenheit – or 2 kelvins – a temperature at which it becomes superconducting and can boost electrons to high energies with nearly zero energy lost in the process. It is one of the last milestones before LCLS-II will produce X-ray pulses that are 10,000 times brighter, on average, than those of LCLS and that arrive up to a million times per second – a world record for today’s most powerful X-ray light sources.

“In just a few hours, LCLS-II will produce more X-ray pulses than the current laser has generated in its entire lifetime,” says Mike Dunne, director of LCLS. “Data that once might have taken months to collect could be produced in minutes. It will take X-ray science to the next level, paving the way for a whole new range of studies and advancing our ability to develop revolutionary technologies to address some of the most profound challenges facing our society.”

With these new capabilities, scientists can examine the details of complex materials with unprecedented resolution to drive new forms of computing and communications; reveal rare and fleeting chemical events to teach us how to create more sustainable industries and clean energy technologies; study how biological molecules carry out life’s functions to develop new types of pharmaceuticals; and peek into the bizarre world of quantum mechanics by directly measuring the motions of individual atoms.

A chilling feat

LCLS, the world’s first hard X-ray free-electron laser (XFEL), produced its first light in April 2009, generating X-ray pulses a billion times brighter than anything that had come before. It accelerates electrons through a copper pipe at room temperature, which limits its rate to 120 X-ray pulses per second.

Read more on the SLAC website

Record time resolution

RESEARCH TEAM DEMONSTRATES BEST PUMP–PROBE TIME RESOLUTION REPORTED SO FAR AT X-RAY FREE-ELECTRON LASER FACILITIES

After being illuminated with light, the atoms in materials react within femtoseconds, i.e. quadrillionths of a second. To observe these reactions in real time, the experiment setup used to capture them must operate with femtosecond time resolution too, otherwise the resulting images will be “blurred”. In a proof-of-principle experiment at the European XFEL, a research team has demonstrated a record time resolution of around 15 femtoseconds—the best resolution reported so far in a pump–probe experiment at an X-ray free-electron laser (FEL) facility, while keeping a high spectral resolution. “These results open up the possibility of doing time-resolved experiments with unprecedented time resolution, enabling the observation of ultrafast processes in materials that were not accessible before,” explains Daniel Rivas from European XFEL, principal investigator of the experiment and first author of the publication in the scientific journal Optica, in which the team from European XFEL and the DESY research centre in Hamburg report their results.

One of the goals of experiments at the European XFEL is to record “molecular movies”, i.e. series of snapshots of dynamic processes taken in extremely rapid succession, which reveal the details of chemical reactions or physical changes in materials at high time resolution. Understanding the molecular rearrangement during such reactions is an essential step towards controlling processes in our natural environment, such as radiation damage in biological systems or photochemical and catalytic reactions. One technique to create such movies is pump–probe spectroscopy, where an optical laser pulse (the “pump” pulse) excites a certain process in a sample and the X-ray laser pulses (the “probe” pulses) are used to take a series of snapshots in order to observe how the process evolves in time.

Read more on the European XFEL website

Image: An ultrashort X-ray pulse and an optical laser pulse interact simultaneously with a neon atom. The X-ray pulse removes an electron from the inner electronic shell and, due to the electromagnetic field of the optical laser that is present at the moment of ionization, the outcoming electron is modulated in energy.

Credit: illustratoren.de/TobiasWuestefeld in cooperation with European XFEL

If at first you don’t succeed…….

For our final Monday Montage, we focus on the benefits of perseverance and our ability as humans to dig deep and remain determined even when things are going wrong. Maximilian Obst, one of the FELBE (HZDR) users, and Michele Manfredda, from FERMI at Elettra, give honest and insightful accounts of their light source experimental experiences. Light sources are complex scientific tools. They are challenging to build, optimise and utilise. But by continuing to overcome obstacles and working as a team, great and unexpected results can appear. Often these results are obtained in the middle of the night or towards the end of a very long shift on the beamline. However, the lucky few who observe them realise they are the first people in the world to have gleaned this knowledge. Perseverance pays off!

Opening the door to X-ray quantum optics

The possibility to generate coherent copies of X-ray pulses from FELs would facilitate a realm of X-ray techniques analogous to those currently available with optical laser light. Yet, this is a challenge due to the short wavelength of X-rays. Now, researchers have devised a new solution that ‘splits’ the electron bunch prior to generation of photons, producing two perfectly coherent copies of pulses.

X-ray free electron lasers (FELs) deliver ultra-bright, ultra-short and coherent X-ray pulses. Short pulses enable time-resolved studies of phenomena such as optical switching, whilst the short wavelength of X-rays, enables experiments with clear fingerprints of atomic species, which also resolve the distances between atoms in solids and liquids. In contrast, optical spectroscopies and microscopies primarily probe electrons shared across molecules, and provide neither images at the atomic scale nor allow unique identification of atomic constituents. Thus, X-ray FELs provide essential insights for fields ranging from pharmacology to electronic device engineering.

Yet, so far, part of the picture that is missing is the ability to do experiments with two – or more – coherent copies of beams. Splitting light is par for the course in optical spectroscopies. Phase-locked pulses – pulse pairs that have a fixed phase relation, split via mirrors, enable a host of interferometric and multidimensional spectroscopies. For X-ray light, the challenge comes with the advantage: the short wavelength. The wavelength – of the order of interatomic spacings – makes it extremely challenging to split the beam using mirrors, where even the smallest path length difference introduces phase jitter.

A perfect X-ray beam splitter

Now, researchers at the SwissFEL have come up with an ingenious solution. This takes a step back in the FEL and ‘splits’ the electron bunch in the accelerator, prior to the production of photons. Collaborators from both the electron and photon ends of SwissFEL have been a feature of this project, which uses a solution from the accelerator side to meet the photon requirements.

“What is really special is that from the beginning this has been a close interaction between quantum technologists and accelerator physicists. This is really facilitated by the interdisciplinarity of PSI, and its early recognition that the current, second quantum revolution will impact its core activity of building and operating large machines”, believes Simon Gerber, head of the Quantum Photon Science Group and corresponding author in the recent publication.

Read more on the PSI website

Image: Authors (L to R) Sven Reiche, Gabriel Aeppli and Simon Gerber standing outside the entrance to the SwissFEL

Credit: Paul Scherrer Institute / Mahir Dzambegovic

Triggering room-temperature superconductivity with light

Scientists discover that triggering superconductivity with a flash of light involves the same fundamental physics that are at work in the more stable states needed for devices, opening a new path toward producing room-temperature superconductivity.

Much like people can learn more about themselves by stepping outside of their comfort zones, researchers can learn more about a system by giving it a jolt that makes it a little unstable – scientists call this “out of equilibrium” – and watching what happens as it settles back down into a more stable state.

In the case of a superconducting material known as yttrium barium copper oxide, or YBCO, experiments have shown that under certain conditions, knocking it out of equilibrium with a laser pulse allows it to superconduct – conduct electrical current with no loss – at much closer to room temperature than researchers expected. This could be a big deal, given that scientists have been pursuing room-temperature superconductors for more than three decades.

But do observations of this unstable state have any bearing on how high-temperature superconductors would work in the real world, where applications like power lines, maglev trains, particle accelerators and medical equipment require them to be stable?

A study published in Science Advances today suggests that the answer is yes.

“People thought that even though this type of study was useful, it was not very promising for future applications,” said Jun-Sik Lee, a staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory and leader of the international research team that carried out the study.

Read more on the SLAC website

Image: To study superconducting materials in their “normal,” non-superconducting state, scientists usually switch off superconductivity by exposing the material to a magnetic field, left. SLAC scientists discovered that turning off superconductivity with a flash of light, right, produces a normal state with very similar fundamental physics that is also unstable and can host brief flashes of room-temperature superconductivity. These results open a new path toward producing room-temperature superconductivity that’s stable enough for practical devices.

Credit: Greg Stewart/SLAC National Accelerator Laboratory

One of the most exciting things is being part of the community

FERMI #LightSourceSelfie

Michele Manfredda is an Italian physicist working at FERMI, the Free Electron laser Radiation for Multidisciplinary Investigations, near Trieste in Italy. Michele words in the PADReS group, which stands for photon analysis delivery and reduction system. The group’s role is to make experiments possible for FERMI users and they look after the optics and diagnostics of the light. As Michele explains, the role involves working in different places and with different teams. His #LightSourceSelfie takes viewers on a fantastic tour of FERMI.

Michele explains that he was first attracted to this field of research by the fact that simple things are done in a very complicated way. When it comes to advice that Michele would give those starting out in their careers, he says, “The advice I would give to someone entering the world of large facilities is go for it. They are crazy environments and you will enjoy it, but remember large facilities can be very time-consuming. So always keep in mind what you can give to science and what science can give you back. Also, find the right people. People you can learn from and people you like to work with because remember, science facilities are wonderful creations but the most wonderful creation is your career, your life. So, as an optical physicist, I tell you don’t be focused on your sample only, be focused mostly on you.”

Someday you will get to play with those electrons!

Razib Obaid is a project scientist at the Linac Coherent Light Source (LCLS) at SLAC in California. LCLS is one of 7 free electron lasers in the Lightsources.org collaboration. The facility takes X-ray snapshots of atoms and molecules at work, providing atomic resolution detail on ultrafast timescales to reveal fundamental processes in materials, technology and living things. Its snapshots can be strung together into “molecular movies” that show chemical reactions as they happen.

In Razib’s #LightSourceSelfie, he takes you into the Near Experimental Hall and describes the stunning equipment that is used to undertake the experiments, the science it enables and the possibilities for new science with the upgrade to LCLSII. Razib says, “The best thing about working at a light source is the ability as a user to tap into the enormous scientific resources and experience that exists among the staff and scientists. Not to mention the state of the art instrumentation that you have access to, to realise your science. To my younger self, I would say, keep studying quantum mechanics, someday you will get to play with those electrons.”

To learn more about LCLS, visit https://lcls.slac.stanford.edu/

Photon Science: A career of creativity & intriguing questions awaits

Markus Ilchen is a physicist at FLASH, the world’s first short wavelength free-electron laser. FLASH is located at DESY in Hamburg. The DESY campus is a ‘small city’ of science offering a versatile and vibrant culture for a wide variety of professions and scientific disciplines. In his #LightSourceSelfie, Markus gives you a peek into some of the highlights on campus, describing some of its history and how FLASH’s unique capabilities will help him to study the chirality (handedness) of molecules. Contributing to solving the mystery behind what chirality does in our universe, drives him and his colleagues.

For those starting out in photon science, Markus has this advice, “Enjoy the great choice! But still of course find your sweet spot. Find your place where you have fun; where you can be yourself; where you can work with nice people; where you are working on intriguing questions; where you can be creative and enjoy the freedom of science in a way that, for one, it keeps you up at night but in a good way.”

An X-ray view of carbon

New measurement method promises spectacular insights into the interior of planets

At the heart of planets, extreme states are to be found: temperatures of thousands of degrees, pressures a million times greater than atmospheric pressure. They can therefore only be explored directly to a limited extent – which is why the expert community is trying to use sophisticated experiments to recreate equivalent extreme conditions. An international research team including the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has adapted an established measurement method to these extreme conditions and tested it successfully: Using the light flashes of the world’s strongest X-ray laser the team managed to take a closer look at the important element, carbon, along with its chemical properties. As reported in the journal Physics of Plasmas (DOI: 10.1063/5.0048150), the method now has the potential to deliver new insights into the interior of planets both within and outside of our solar system.

The heat is unimaginable, the pressure huge: The conditions in the interior of Jupiter or Saturn ensure that the matter found there exhibits an unusual state: It is as dense as a metal but, at the same time, electrically charged like a plasma. “We refer to this state as warm dense matter,” explains Dominik Kraus, physicist at HZDR and professor at the University of Rostock. “It is a transitional state between solid state and plasma that is found in the interior of planets, although it can occur briefly on Earth, too, for example during meteor impacts.” Examining this state of matter in any detail in the lab is a complicated process involving, for example, firing strong laser flashes at a sample, and, for the blink of an eye, heating and condensing it.

Read more on the HZDR website

Image: High-resolution spectroscopy will enable unique insights into chemistry happening deep inside planets

Credit: HZDR / U. Lehmann

Scientists capture a ‘quantum tug’ between neighbouring water molecules

The work sheds light on the web of hydrogen bonds that gives water its strange properties, which play a vital role in many chemical and biological processes.

Water is the most abundant yet least understood liquid in nature. It exhibits many strange behaviors that scientists still struggle to explain. While most liquids get denser as they get colder, water is most dense at 39 degrees Fahrenheit, just above its freezing point. This is why ice floats to the top of a drinking glass and lakes freeze from the surface down, allowing marine life to survive cold winters. Water also has an unusually high surface tension, allowing insects to walk on its surface, and a large capacity to store heat, keeping ocean temperatures stable.

Now, a team that includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Stockholm University in Sweden have made the first direct observation of how hydrogen atoms in water molecules tug and push neighbouring water molecules when they are excited with laser light. Their results, published in Nature today, reveal effects that could underpin key aspects of the microscopic origin of water’s strange properties and could lead to a better understanding of how water helps proteins function in living organisms.

Read more on the LCLS website

Image: For these experiments, the research team (left to right: Xiaozhe Shen, Pedro Nunes, Jie Yang and Xijie Wang) used SLAC’s MeV-UED, a high-speed “electron camera” that uses a powerful beam of electrons to detect subtle molecular movements in samples.

Credit: Dawn Harmer/SLAC National Accelerator Laboratory

First detailed look at how charge transfer distorts a molecule’s structure

Charge transfer is highly important in most areas of chemistry, including photosynthesis and other processes in living things. A SLAC X-ray laser study reveals how it works in a molecule whose lopsided response to light has puzzled scientists for nearly a decade.

When light hits certain molecules, it dislodges electrons that then move from one location to another, creating areas of positive and negative charge. This “charge transfer” is highly important in many areas of chemistry, in biological processes like photosynthesis and in technologies like semiconductor devices and solar cells.

Even though theories have been developed to explain and predict how charge transfer works, they have been validated only indirectly because of the difficulty of observing how a molecule’s structure responds to charge movements with the required atomic resolution and on the required ultrafast time scales.

In a new study, a research team led by scientists from Brown University, the Department of Energy’s SLAC National Accelerator Laboratory and the University of Edinburgh used SLAC’s X-ray free-electron laser to make the first direct observations of molecular structures associated with charge transfer in gas molecules hit with light.

Molecules of this gas, called N,N′-dimethylpiperazine or DMP, are normally symmetric, with a nitrogen atom at each end. Light can knock an electron out of a nitrogen atom, leaving a positively charged ion known as a “charge center.”

Read more on the SLAC website

Image: In experiments with SLAC’s X-ray free-electron laser, scientists knocked electrons out of a molecule known as DMP to make the first detailed observations of how a process called charge transfer affects its molecular structure. Left: DMP is normally symmetric. Center: When a pulse of light knocks an electron out of one of its nitrogen atoms (blue spheres), it leaves a positively charged ion known as a charge center, shown in pink. This creates a charge imbalance that shifts the positions of atoms. Right: But within three trillionths of a second, the charge redistributes itself between the two nitrogen atoms until it evens out and the molecule becomes symmetric again.

Credit: Greg Stewart/ SLAC National Accelerator Laboratory

Beaming in on Coronavirus details

User operation resumed at European XFEL end of March, and the first experiments to receive beamtime are those being carried out at the Single Particles, Clusters, and Biomolecules & Serial Femtosecond Crystallography (SPB/SFX) instrument. They will focus on getting deeper insights into the Coronavirus, and, if successful, can lead to a better understanding of the structure of key Coronavirus proteins. New information about the shapes of these proteins, which the virus needs to copy itself, will aid scientists in their quest to find ways to fight COVID.

“Three user collaborations have proposed experiments that will use two distinct approaches to study the Coronavirus. Two collaborations lead by scientists from DESY and Diamond Light Source will look at the structure and binding of ligands to the proteases of the Coronavirus,” says Adrian Mancuso, leading scientist at the SPB/SFX instrument. A ligand is a molecule that binds another specific molecule or atom. Some ligands deliver a signal during the binding process and can be thought of as signaling molecules, which interact with proteins in target cells called receptors. At the European XFEL, scientists can potentially observe the process of these ligands attaching to proteins at atomic resolution, however, first an ordered crystal of the relevant protein is required. “XFELs are uniquely positioned to watch how irreversible processes in proteins—such as binding of potential drug candidates—happen,” explains Mancuso.

Read more on the European XFEL website

Image: A shot from the control hutch showing one of the first COVID-related beamtimes at SPB/SFX

Credit: European XFEL