From Science and Technology Facilities Council: “Super laser developed in the UK will help scientists create the conditions found inside planets”

From Science and Technology Facilities Council

19 March 2020

Central Laser Facility’s DiPOLE 100 X laser in the lab before delivery to the European XFEL facility in Germany. (Credit: STFC.)

STFC DiPOLE 100-X Laser for European XFEL

A unique laser developed at the UK’s Central Laser Facility will allow scientists working at European XFEL to create conditions simulating the interior of Earth-type planets for the first time.

European XFEL campus

The UK is a core partner in the European X-Ray Free Electron Laser (European XFEL) facility in Germany. XFEL is the largest, most powerful X-Ray laser in existence, with a brilliance that is a billion times higher than any other conventional X-ray radiation source. By using this new laser, DiPOLE 100-X, in combination with the extremely bright, intense X-ray beam produced by the XFEL, scientists will be able to probe the atomic structure and dynamics of materials under the extreme conditions found within the core of a planet where temperatures can be up to 10,000°C and pressures can be up to 10,000 tonnes per square centimetre.

Scientists have already discovered more than 3,000 planets outside our own solar system. What these planets are composed of, their mass, pressure and temperature conditions found in and on these planets is not yet known. The experimental set-up being developed at XFEL will allow X-ray diffraction and spectroscopy techniques that could simulate these conditions on Earth.

“It is thought that the form of elements such as carbon and iron found on some of these exoplanets does not exist elsewhere” says Ulf Zastrau, group leader at the instrument for High-Energy Density science at European XFEL. “Until now, it has not been technically possible to study these fascinating worlds before, because we could not create such extreme temperatures and pressures in the lab. Now, with the arrival of the new DiPOLE 100-X laser at European XFEL we are a step closer to being able to study the behavior, composition and conditions of these planets. This really opens up an entirely new field of scientific exploration.”

A joint XFEL and the Science and Technology Facilities Council CLF team of scientists and engineers is already busy installing the DiPOLE 100-X laser in the underground laser “hutch” and commissioning experiments will begin in the summer. Integration and synchronisation with the XFEL beam will follow, with experimental time available from next year.

Professor John Collier, CLF Director, said: “I am delighted that CLF’s latest generation of DiPOLE laser technology is being installed on the European XFEL. The unique combination of DiPOLE laser radiation with the XFEL beam will transform laboratory astrophysics and the study of matter in extreme conditions. DiPOLE’s high repetition rate will deliver a step-change in the speed of data collection, producing orders of magnitude improvements in the accuracy of our measurements and the ability to detect previously unobservable effects.”

In addition to developing and building the DiPOLE laser for XFEL UK scientists at STFC also played a major role in the design and development of a cutting edge X-ray camera for the facility. The Large Pixel Detector (LPD) was installed at XFEL in 2017 and records images at a rate of 4.5 million frames per second – fast enough to keep up with the European XFEL’s 27,000 pulses per second, which are arranged into short high speed bursts. The LPD enables users to take clear snapshots of ultrafast processes such as chemical reactions as they take place.

Further information

Construction of the DiPOLE 100-X laser was funded by joint equipment grants from the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC), both part of UK Research and Innovation.

The UK was European XFEL’s twelfth member state. The UK is represented in European XFEL by the Science and Technology Facilities Council (STFC) as shareholder.

About STFC’s Central Laser Facility

The Central Laser Facility (CLF) at the STFC Rutherford Appleton Laboratory is one of the world’s leading laser facilities providing scientists from the UK and Europe with an unparalleled range of state of the art technology. CLF’s facilities range from advanced, compact tuneable lasers which can pinpoint individual particles to high power laser installations that recreate the conditions inside stars.

What is an X-ray Free Electron Laser anyway?

Free Electron Lasers (FEL) are at the cutting edge of scientific research, with the huge potential to tackle global challenges, from drug development to producing hydrogen powered fuels. FELs allow us to look at things on a much closer scale. Like other lasers, they rely on light, and to do this they use electrons. These electrons are driven by a particle accelerator to incredibly high speeds. They are then passed through series of magnets in such a way that creates bunches of electrons, and during this process induced to emit ultrashort bursts of the light.

This light can then be aimed at a target within a sample station. This interaction between the light and the sample is captured using a detector. Unlike standard lasers and synchrotron light sources, FELs can produce light at a range of frequencies. They are the most flexible, high power and efficient generators of tuneable coherent light from infra-red to X-rays. European XFEL, the worlds’ largest, most powerful laser, can generate 27,000 X-ray flashes per second.

This power allows scientists to observe reactions that are happening on the atomic and molecular scales, opening up totally new avenues of research, beyond reach of other types of X-ray or laser facility.

Further information about European XFEL

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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.

Daresbury Laboratory at Sci-Tech Daresbury in the Liverpool City Region,

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 SLAC National Accelerator Lab via phys.org: “Terahertz radiation technique opens a new door for studying atomic behavior”

From SLAC National Accelerator Lab

via

phys.org

March 6, 2020
Erika K. Carlson, SLAC National Accelerator Laboratory

A compressor using terahertz radiation to shorten electron bunches is small enough to fit into the palm of a hand. Credit: Dawn Harmer/SLAC National Accelerator Laboratory.

Researchers from the Department of Energy’s SLAC National Accelerator Laboratory have made a promising new advance for the lab’s high-speed “electron camera” that could allow them to “film” tiny, ultrafast motions of protons and electrons in chemical reactions that have never been seen before. Such “movies” could eventually help scientists design more efficient chemical processes, invent next-generation materials with new properties, develop drugs to fight disease and more.

The new technique takes advantage of a form of light called terahertz radiation, instead of the usual radio-frequency radiation, to manipulate the beams of electrons the instrument uses. This lets researchers control how fast the camera takes snapshots and, at the same time, reduces a pesky effect called timing jitter, which prevents researchers from accurately recording the timeline of how atoms or molecules change.

The method could also lead to smaller particle accelerators: Because the wavelengths of terahertz radiation are about a hundred times smaller than those of radio waves, instruments using terahertz radiation could be more compact.

The researchers published the findings in Physical Review Letters on February 4.

A Speedy Camera

SLAC’s “electron camera,” or ultrafast electron diffraction (MeV-UED) instrument, uses high-energy beams of electrons traveling near the speed of light to take a series of snapshots—essentially a movie—of action between and within molecules. This has been used, for example, to shoot a movie of how a ring-shaped molecule breaks when exposed to light and to study atom-level processes in melting tungsten that could inform nuclear reactor designs.

The technique works by shooting bunches of electrons at a target object and recording how electrons scatter when they interact with the target’s atoms. The electron bunches define the shutter speed of the electron camera. The shorter the bunches, the faster the motions they can capture in a crisp image.

“It’s as if the target is frozen in time for a moment,” says SLAC’s Emma Snively, who spearheaded the new study.

SLAC’s Emma Snively and Mohamed Othman at the lab’s high-speed “electron camera,” an instrument for ultrafast electron diffraction (MeV-UED). Credit: Jacqueline Orrell/SLAC National Accelerator Laboratory.

For that reason, scientists want to make all the electrons in a bunch hit a target as close to simultaneously as possible. They do this by giving the electrons at the back a little boost in energy, to help them catch up to the ones in the lead.

So far, researchers have used radio waves to deliver this energy. But the new technique developed by the SLAC team at the MeV-UED facility uses light at terahertz frequencies instead.

Why terahertz?

A key advantage of using terahertz radiation lies in how the experiment shortens the electron bunches. In the MeV-UED facility, scientists shoot a laser at a copper electrode to knock off electrons and create beams of electron bunches. And until recently, they typically used radio waves to make these bunches shorter.

However, the radio waves also boost each electron bunch to a slightly different energy, so individual bunches vary in how quickly they reach their target. This timing variance is called jitter, and it reduces researchers’ abilities to study fast processes and accurately timestamp how a target changes with time.

The terahertz method gets around this by splitting the laser beam into two. One beam hits the copper electrode and creates electron bunches as before, and the other generates the terahertz radiation pulses for shortening the electron bunches. Since they were produced by the same laser beam, electron bunches and terahertz pulses are now synchronized with each other, reducing the timing jitter between bunches.

Down to the femtosecond

A key innovation for this work, the researchers say, was creating a particle accelerator cavity, called the compressor. This carefully machined hunk of metal is small enough to sit in the palm of a hand. Inside the device, terahertz pulses shorten electron bunches and give them a targeted and effective push.

From left: SLAC’s Emma Snively, Michael Kozina and Mohamed Othman at the lab’s MeV-UED instrument. Credit: Jacqueline Orrell/SLAC National Accelerator Laboratory.

As a result, the team could compress electron bunches so they last just a few tens of femtoseconds, or quadrillionths of a second. That’s not as much compression as conventional radio-frequency methods can achieve now, but the researchers say the ability to simultaneously lower jitter makes the terahertz method promising. The smaller compressors made possible by the terahertz method would also mean lower cost compared to radio-frequency technology.

“Typical radio-frequency compression schemes produce shorter bunches but very high jitter,” says Mohamed Othman, another SLAC researcher on the team. “If you produce a compressed bunch and also reduce the jitter, then you’ll be able to catch very fast processes that we’ve never been able to observe before.”

Eventually, the team says, the goal is to compress electron bunches down to about a femtosecond. Scientists could then observe the incredibly fast timescales of atomic behavior in fundamental chemical reactions like hydrogen bonds breaking and individual protons transferring between atoms, for example, that aren’t fully understood.

“At the same time that we are investigating the physics of how these electron beams interact with these intense terahertz waves, we’re also really building a tool that other scientists can use immediately to explore materials and molecules in a way that wasn’t possible before,” says SLAC’s Emilio Nanni, who led the project with Renkai Li, another SLAC researcher. “I think that’s one of the most rewarding aspects of this research.”

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SLAC/LCLS II projected view

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SSRL and LCLS are DOE Office of Science user facilities.

From Brookhaven National Lab: “Light Sources Form Data Solution Task Force”

From Brookhaven National Lab

February 12, 2020
Stephanie Kossman
skossman@bnl.gov

New collaboration between scientists at the five U.S. Department of Energy light source facilities will develop flexible software to easily process big data.

BNL NSLS-II

LBNL ALS

ANL Advanced Photon Source

SLAC SSRL Campus

SLAC LCLS

Above are the five DOE light sources: Brookhaven National Laboratory’s National Synchrotron Light Source II (NSLS-II), Lawrence Berkeley National Laboratory’s Advanced Light Source (ALS), Argonne National Laboratory’s Advanced Photon Source (APS), and SLAC National Accelerator Laboratory’s Stanford Synchrotron Radiation Lightsource (SSRL) and Linac Coherent Light Source (LCLS).

Light source facilities are tackling some of today’s biggest scientific challenges, from designing new quantum materials to revealing protein structures. But as these facilities continue to become more technologically advanced, processing the wealth of data they produce has become a challenge of its own. By 2028, the five U.S. Department of Energy (DOE) Office of Science light sources, will produce data at the exabyte scale, or on the order of billions of gigabytes, each year. Now, scientists have come together to develop synergistic software to solve that challenge.

With funding from DOE for a two-year pilot program, scientists from the five light sources have formed a Data Solution Task Force that will demonstrate, build, and implement software, cyberinfrastructure, and algorithms that address universal needs between all five facilities. These needs range from real-time data analysis capabilities to data storage and archival resources.

“It is exciting to see the progress that is being made by all the light sources working together to produce solutions that will be deployed across the whole DOE complex,” said Stuart Campbell, leader of the data acquisition, management and analysis group at the National Synchrotron Light Source II (NSLS-II), a DOE Office of Science user facility at DOE’s Brookhaven National Laboratory.

In addition, the new software will be designed to facilitate multimodal research—studies that combine data collected from multiple experimental stations, called beamlines. Typically, each beamline at a light source uses custom-built data acquisition software that is incompatible with another beamline’s, making it difficult for scientists to collect and compare data from multiple experimental stations. The task force aims to develop flexible software that can be deployed at multiple beamlines across all five facilities, expanding the possibilities for scientific collaboration.

Members of the task force met at NSLS-II for a project kickoff meeting in August of 2019.

To develop the new software, the task force will start by building up existing solutions that can already be found at the five light sources. Two of the key components are Bluesky, an open source software that was created at NSLS-II, and Xi-CAM, which was developed at the Advanced Light Source (ALS) and the Center for Advanced Mathematics for Energy Research Applications—both at DOE’s Lawrence Berkeley National Laboratory. Together, Bluesky and Xi-Cam will provide capabilities like live visualization and interactivity, data processing tools, and the ability to export data in real time into nearly any file format.

Each of the five light sources in the task force is bringing unique tools and skillsets to help develop a more robust and scalable solution to extract scientific knowledge from data for the nation’s light sources.

“There is tremendous enthusiasm at the light sources for solving the data challenge,” said Alexander Hexemer, senior scientist and computing program lead at ALS. “We strongly believe this will be the path forward for light sources to work together in the future.”

With the task force in its early stages, researchers have begun running test experiments on beamlines at NSLS-II and installing Bluesky and Xi-CAM at the Advanced Photon Source, a DOE Office of Science user facility at DOE’s Argonne National Laboratory.

By the end of the two-year pilot project, “we plan to deliver a set of tools that will provide an end-to-end software solution for the targeted scientific areas that can be deployed and used on different beamlines across all the DOE light sources,” Campbell said.

Alongside the task force pilot, the five light sources are working with DOE to develop data systems solutions that will scale to the unprecedented data rates that will be produced in the near future, using the new generation of “exascale” computers being built by DOE.

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One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

From Techniche Universität Wein (Vienna) via phys.org: “How to take a picture of a light pulse”

From Techniche Universität Wein (Vienna)

via

phys.org

Two laser pulses hitting a silicon dioxide crystal. Credit: Vienna University of Technology, TU Vienna.

Until now, complex experimental equipment was required to measure the shape of a light pulse. A team from TU Wien (Vienna), MPI Garching and LMU Munich has now made this much easier.

Today, modern lasers can generate extremely short light pulses, which can be used for a wide range of applications from investigating materials to medical diagnostics. For this purpose, it is important to measure the shape of the laser light wave with high accuracy. Until now, this has required a large, complex experimental setup. Now this can be done with a tiny crystal with a diameter of less than one millimeter. The new method has been developed by the MPI for Quantum Optics in Garching, the LMU Munich and the TU Wien (Vienna). The advance will now help to clarify important details about the interaction of light and matter.

Looking at Light with Electrons

Extremely short light pulses with a duration in the order of femtoseconds (10-15 seconds) were investigated. “In order to create an image of such light waves, they must be made to interact with electrons,” says Prof. Joachim Burgdörfer from the Institute of Theoretical Physics at the TU Wien. “The reaction of the electrons to the electric field of the laser gives us very precise information about the shape of the light pulse.”

Previously, the common way to measure an infrared laser pulse was adding a much shorter laser pulse with a wavelength in the X-ray range. Both pulses are sent through a gas. The X-ray pulse ionizes individual atoms, electrons are released, which are then accelerated by the electric field of the infrared laser pulse. The motion of the electrons is recorded, and if the experiment is carried out many times with different time shifts between the two pulses, the shape of the infrared laser pulse can eventually be reconstructed. “The experimental effort required for this method is very high,” says Prof. Christoph Lemell (TU Vienna). “A complicated experimental setup is needed, with vacuum systems, many optical elements and detectors.”

Measurement in Tiny Silicon Oxide Crystals

To bypass such complications, the idea was born to measure light pulses not in a gas but in a solid: “In a gas you have to ionize atoms first to get free electrons. In a solid it is sufficient to give the electrons enough energy so that they can move through the solid, driven by the laser field,” says Isabella Floss (TU Vienna). This generates an electric current which can be directly measured.

Tiny crystals of silicon oxide with a diameter of a few hundred micrometers are used for this purpose. They are hit by two different laser pulses: The pulse which is to be investigated can have any wavelength ranging from ultraviolet light and visible colors to long-wave infrared. While this laser pulse penetrates the crystal, another infrared pulse is fired at the target. “This second pulse is so strong that non-linear effects in the material can change the energy state of the electrons so that they become mobile. This happens at a very specific point in time, which can be tuned and controlled very precisely,” explains Joachim Burgdörfer.

As soon as the electrons can move through the crystal, they are accelerated by the electric field of the first beam. This produces an electric current which is measured directly at the crystal. This signal contains precise information about the shape of the light pulse.

Many Possible Applications

At TU Wien, the effect was studied theoretically and analyzed in computer simulations. The experiment was performed at the Max Planck Institute for Quantum Optics in Garching. “Thanks to the close cooperation between theory and experiment, we have been able to show that the new method works very well, over a large frequency range, from ultraviolet to infrared,” says Christoph Lemell. “The waveform of light pulses can now be measured much more easily than before, with the help of such a much simpler and more compact setup.”

The new method opens up many interesting applications: It should be possible to precisely characterize novel materials, to answer fundamental physical questions about the interaction of light and matter, and even to analyze complex molecules—for example, to reliably and quickly detect diseases by examining tiny blood samples.

Science paper:
Shawn Sederberg et al. Attosecond optoelectronic field measurement in solids.
Nature Communications

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From UC Berkeley: “Blue diode illustrates limitations, promise of perovskite semiconductors”

From UC Berkeley

January 24, 2020
Robert Sanders
rlsanders@berkeley.edu

UC Berkeley chemists created a type of halide perovskite crystal that emits blue light, something that has been hard to achieve with the trendy new material. But the researchers also found that these materials are inherently unstable, requiring careful control of temperature and chemical environment to maintain their precise color. (UC Berkeley photo courtesy of Peidong Yang)

University of California, Berkeley, scientists have created a blue light-emitting diode (LED) from a trendy new semiconductor material, halide perovskite, overcoming a major barrier to employing these cheap, easy-to-make materials in electronic devices.

In the process, however, the researchers discovered a fundamental property of halide perovskites that may prove a barrier to their widespread use as solar cells and transistors.

Alternatively, this unique property may open up a whole new world for perovskites far beyond that of today’s standard semiconductors.

In a paper appearing Jan. 24 in the journal Science Advances, UC Berkeley chemist Peidong Yang and his colleagues show that the crystal structure of the halide perovskites changes with temperature, humidity and the chemical environment, disrupting their optical and electronic properties. Without close control of the physical and chemical environment, perovskite devices are inherently unstable. This is not a major problem for traditional semiconductors.

“Some people may say this is a limitation. For me, this is a great opportunity,” said Yang, the S. K. and Angela Chan Distinguished Chair in Energy in the College of Chemistry and director of the Kavli Energy NanoSciences Institute. “This is new physics: a new class of semiconductors that can be readily reconfigured, depending on what sort of environment you put them in. They could be a really good sensor, maybe a really good photoconductor, because they will be very sensitive in their response to light and chemicals.”

Current semiconductors made of silicon or gallium nitride are very stable over a range of temperatures, primarily because their crystal structures are held together by strong covalent bonds. Halide perovskite crystals are held together by weaker ionic bonds, like those in a salt crystal. This means they’re easier to make — they can be evaporated out of a simple solution — but also susceptible to humidity, heat and other environmental conditions.

“This paper is not just about showing off that we made this blue LED,” said Yang, who is a senior faculty scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) and a UC Berkeley professor of materials science and engineering. “We are also telling people that we really need to pay attention to the structural evolution of perovskites during the device operation, any time you drive these perovskites with an electrical current, whether it is an LED, a solar cell or a transistor. This is an intrinsic property of this new class of semiconductor and affects any potential optoelectronic device in the future using this class of material.”

The blue diode blues

Making semiconductor diodes that emit blue light has always been a challenge, Yang said. The 2014 Nobel Prize for Physics was awarded for the breakthrough creation of efficient blue light-emitting diodes from gallium nitride. Diodes, which emit light when an electric current flows through them, are optoelectronic components in fiber optic circuits as well as general purpose LED lights.

The crystal structure of the blue-emitting halide perovskite changes with heating from room temperature, 300 Kelvin, to 450 Kelvin, the typical operating temperature of an electronic device. The structural change alters the wavelength of light, changing it from blue to blue-green, an unacceptable instability in electronics. (UC Berkeley photo courtesy of Peidong Yang)

Since halide perovskites first drew wide attention in 2009, when Japanese scientists discovered that they make highly efficient solar cells, these easily made, inexpensive crystals have excited researchers. So far, red- and green-emitting diodes have been demonstrated, but not blue. Halide perovskite blue-emitting diodes have been unstable — that is, their color shifts to longer, redder wavelengths with use.

As Yang and his colleagues discovered, this is due to the unique nature of perovskites’ crystal structure. Halide perovskites are composed of a metal, such as lead or tin, equal numbers of larger atoms, such as cesium, and three times the number of halide atoms, such as chlorine, bromine or iodine.

When these elements are mixed together in solution and then dried, the atoms assemble into a crystal, just as salt crystalizes from sea water. Using a new technique and the ingredients cesium, lead and bromine, the UC Berkeley and Berkeley Lab chemists created perovskite crystals that emit blue light and then bombarded them with X-rays at the Stanford Linear Accelerator Center (SLAC) to determine their crystalline structure at various temperatures. They found that, when heated from room temperature (about 300 Kelvin) to around 450 Kelvin, a common operating temperature for semiconductors, the crystal’s squashed structure expanded and eventually sprang into a new orthorhombic or tetragonal configuration.

Since the light emitted by these crystals depends on the arrangement of and distances between atoms, the color changed with temperature, as well. A perovskite crystal that emitted blue light (450 nanometers wavelength) at 300 Kelvin suddenly emitted blue-green light at 450 Kelvin.

Yang attributes perovskites’ flexible crystal structure to the weaker ionic bonds typical of halide atoms. Naturally occurring mineral perovskite incorporates oxygen instead of halides, producing a very stable mineral. Silicon-based and gallium nitride semiconductors are similarly stable because the atoms are linked by strong covalent bonds.

Making blue-emitting perovskites

According to Yang, blue-emitting perovskite diodes have been hard to create because the standard technique of growing the crystals as a thin film encourages formation of mixed crystal structures, each of which emits at a different wavelength. Electrons get funneled down to those crystals with the smallest bandgap — that is, the smallest range of unallowed energies — before emitting light, which tends to be red.

Two different types of blue light-emitting perovskite crystal. On the left, perovskite with two layers of the octahedral perovskite structure produces a shorter wavelength of blue light than a crystal with three octahedral layers, right. (UC Berkeley photos courtesy of Peidong Yang)

To avoid this, Yang’s postdoctoral fellows and co-first authors — Hong Chen, Jia Lin and Joohoon Kang — grew single, layered crystals of perovskite and, adapting a low-tech method for creating graphene, used tape to peel off a single layer of uniform perovskite. When incorporated into a circuit and zapped with electricity, the perovskite glowed blue. The actual blue wavelength varied with the number of layers of octahedral perovskite crystals, which are separated from one another by a layer of organic molecules that allows easy separation of perovskite layers and also protects the surface.

Nevertheless, the SLAC experiments showed that the blue-emitting perovskites changed their emission colors with temperature. This property can have interesting applications, Yang said. Two years ago, he demonstrated a window made of halide perovskite that becomes dark in the sun and transparent when the sun goes down and also produces photovoltaic energy.

We need to think in different ways of using this class of semiconductor,” he said. “We should not put halide perovskites into the same application environment as a traditional covalent semiconductor, like silicon. We need to realize that this class of material has intrinsic structural properties that make it ready to reconfigure. We should utilize that.”

The work was supported by the U.S. Department of Energy’s Basic Energy Sciences program. Other co-authors of the paper are Qiao Kong, Dylan Lu, Minliang Lai, Li Na Quan and Jianbo Jin of UC Berkeley; Jun Kang, Zhenni Lin and Lin-wang Wang of Berkeley Lab; and Michael Toney of SLAC. Chen is currently at Southern University of Science and Technology in Shenzhen, China; Lin is at Shanghai University of Electric Power; and Joohoon Kang is at Sungkyunkwan University in Seoul, South Korea.

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Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

From Brookhaven National Lab: “NSLS-II Achieves Design Beam Current of 500 Milliamperes”

From Brookhaven National Lab

January 22, 2020
Cara Laasch
laasch@bnl.gov

Accelerator division enables new record current during studies.

The NSLS-II accelerator division proudly gathered to celebrate their recent achievement. The screen above them shows the slow increase of the electron current in the NSLS-II storage ring and its stability.

The National Synchrotron Light Source II (NSLS-II) [below] at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory is a gigantic x-ray microscope that allows scientists to study the inner structure of all kinds of material and devices in real time under realistic operating conditions. The scientists using the machine are seeking answers to questions including how can we built longer lasting batteries; when life started on our planet; and what kinds of new materials can be used in quantum computers, along with many other questions in a wide variety of research fields.

The heart of the facility is a particle accelerator that circulates electrons at nearly the speed of light around the roughly half-a-mile-long ring. Steered by special magnets within the ring, the electrons generate ultrabright x-rays that enable scientists to address the broad spectrum of research at NSLS-II.

Now, the accelerator division at NSLS-II has reached a new milestone for machine performance. During recent accelerator studies, the team has been able to ramp up the machine to 500 milliamperes (mA) of current and to keep this current stable for more than six hours. Similar to a current in a river, the current in an accelerator is a measure of the number of electrons that circulate the ring at any given time. In NSLS-II’s case, a higher electron current opens the pathway to more intense x-rays for all the experiments happening at the facility.

“Since we turned on the machine for the first time in 2014 with 50mA current, we have progressed steadily upwards in current and now – in just five years – we have reached 500mA,” said Timur Shaftan, NSLS-II accelerator division director. “Along the way, we encountered many significant challenges, and it is thanks to the dedication, knowledge, and expertise of the team that we were able to overcome them all to get here.”

All good things come in threes?

On their quest to a higher current, the accelerator division faced three major challenges: an increase in power consumption of the radiofrequency (RF) accelerating cavities, more intense “wakefields,” and the unexpected heating of some accelerator components.

The purpose of the RF accelerating cavities can be compared to pushing a child on a swing – with the child being the electrons. With the correct timing, large amplitudes can be driven with little effort. The cavities feed more and more energy to the electrons to compensate for the energy the electrons lose as they generate x-rays in their trips around the ring.

“The cavities use electricity to push the electrons forward, and even though our cavities are very efficient, they still draw a good amount of raw power,” said Jim Rose, RF group leader. “To reach 500 mA, we monitored this increase closely to ensure that we wouldn’t cross our limit for power, which we didn’t. However, there is another challenge we now have to face: The cavities compress the groups of electrons—we call them bunches—that rush through the machine, and by doing so they increase the heating issues that we face. To fully address this in the future, we will install other cavities of a different RF frequency that would lengthen the bunches again.”

Rose is referring to the issue of “wakefields.” As the electrons speed around the ring, they create so called wakefields—just like when you run your finger through still water and create waves that roll on even though your fingers are long gone. In the same way, the rushing electrons generate a front of electric fields that follow them around the ring.

“Having more intense wakefields causes two challenges: First, these fields influence the next set of electrons, causing them to lose energy and become unstable, and second, they heat up the vacuum chamber in which the beam travels,” said accelerator physicist Alexei Blednykh. “One of the limiting components in our efforts to reach 500mA was the ceramic vacuum chambers, because they were overheating. We mitigated the effect by installing additional cooling fans. However, to fully solve the issue we will need to replace the existing chambers with new chambers that have a thin titanium coating on the inside.”

The accelerator division decided to coat all the new vacuum chambers in house using a technique called direct current magnetron sputtering. During the sputtering process, a titanium target is bombarded with ionized gas so that it ejects millions of titanium atoms, which spray onto the surface of the vacuum chamber to create a thin metal film.

“At first, coating chambers sounds easy enough, but our chambers are long and narrow, which forces you to think differently how you can apply the coating. We had to design a coating system that was capable of handling the geometry of our chambers,” said vacuum group leader Charlie Hetzel. “Once we developed a system that could be used to coat the chambers, we had to develop a method that could accurately measure the thickness and uniformity along the entire length of the chamber.”

For the vacuum chambers to survive the machine at high current, the coatings had to meet a number of demanding requirements in terms of their adhesion, thickness, and uniformity.

The third challenge the team needed to overcome was resolving the unexpected heating found between some of the vacuum flanges. Each of the vacuum joints around the half-mile long accelerator contain a delicate RF bridge. Any errors during installation can result in additional heating and risk to the vacuum seal of the machine.

“We knew from the beginning that increasing the current to 500 mA would be hard on the machine, however, we needed to know exactly where the real hot spots were,” explained accelerator coordination group leader Guimei Wang. “So, we installed more than 1000 temperature sensors around the whole machine, and we ran more than 400 hours of high-current beam studies over the past three years, where we monitored the temperature, vacuum, and many other parameters of the electrons very closely to really understand how our machine is behaving.”

Based on all these studies and many more hours spend analyzing each single study run, the accelerator team made the necessary decisions as to which what parts needed to be coated or changed and, most importantly, how to run the machine at such a high current safely and reliably.

Where do we go from here?

Achieving 500mA during beam studies was an important step to begin to shed light on the physics within the machine at these high currents, as well as to understand the present limits of the accelerator. Equipped with these new insights, the accelerator division now knows that their machine can reach the 500mA current for a short time, but at this point it’s not possible to sustain high current for operations over extended periods with the RF power necessary to deliver it to users. To run the machine at this current, NSLS-II’s accelerator will need additional RF systems both to lengthen the bunches and to secure high reliability of operations, while providing sufficient RF power to the beam to generate x-rays for the growing set of beamlines.

“Achieving 500 mA for the first time is a major milestone in the life of NSLS-II, showing that we can reach the aggressive design current goals we set for ourselves when we first started thinking about what NSLS-II could be all those years ago. This success is due to a lot of hard work, expertise, and dedication by many, many people at NSLS-II and I would like to thank them all very much,” said NSLS-II Director John Hill. “The next steps are to fully understand how the machine behaves at this current and ultimately deliver it to our users. This will require further upgrades to our accelerator systems—and we are actively working towards those now.”

NSLS-II is a DOE Office of Science user facility.

See the full article here .

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One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

From Lawrence Berkeley National Lab: “Milestone in Advanced Light Source Upgrade Project Will Bring in a New Ring”

From Lawrence Berkeley National Lab

January 8, 2020
Glenn Roberts Jr.
geroberts@lbl.gov
(510) 486-5582

Construction of innovative accumulator ring as part of ALS-U project will keep Berkeley Lab at the forefront of synchrotron light source science.

This cutaway rendering of the Advanced Light Source dome shows the layout of three electron-accelerating rings. A new approval step in the ALS Upgrade project will allow the installation of the middle ring, known as the accumulator ring. (Credit: Matthaeus Leitner/Berkeley Lab)

An upgrade of the Advanced Light Source (ALS) at the U.S. Department of Energy’s (DOE’s) Lawrence Berkeley National Laboratory (Berkeley Lab) has passed an important milestone that will help to maintain the ALS’ world-leading capabilities.

LBNL ALS

On Dec. 23 the DOE granted approval for a key funding step that will allow the project to start construction on a new inner electron storage ring. Known as an accumulator ring, this inner ring will feed the upgraded facility’s main light-producing storage ring, and is a part of the upgrade project (ALS-U).

This latest approval, known as CD-3a, authorizes an important release of funds that will be used to purchase equipment and formally approves the start of construction on the accumulator ring. This approval is an essential step in a DOE “critical decision” process that involves in-depth reviews at several key project stages.

“It’s exciting to finally be able to start construction and see all our hard work come to fruition and to get one step closer to having a next-generation light source,” said David Robin, director of the ALS-U project.

The ALS produces ultrabright light over a range of wavelengths, from infrared to high-energy X-rays, by accelerating electrons to nearly the speed of light and guiding them along a circular path.

Powerful arrays of magnets bend the beam of electrons, causing it to emit light that is channeled down dozens of beamlines for experiments in a wide range of scientific areas – from physics, medicine, and chemistry to biology and geology. More than 2,000 scientists from around the world conduct experiments at the facility each year.

Brighter, more laser-like beams, and ‘recycled’ electrons

In addition to installing the accumulator ring, the upgrade project will replace the existing main storage ring with a next-generation storage ring that will reduce the size of the light beams at their source from around 100 microns (millionths of a meter) to below 10 microns.

This illustration shows components of the accumulator ring (top) and new storage ring (bottom) that will be installed as a part of the ALS-U project. (Credit: Berkeley Lab)

The combination of the accumulator ring and upgraded main storage ring will enable at least 100 times brighter beams at key energies, and will make the beams more laser-like by enhancing a property known as coherence. This will make it possible to reveal nanometer-scale features of samples, and to observe chemical processes and the function of materials in real time.

Today, electrons at the ALS are first accelerated by a linear (straight) accelerator and a booster ring before they are transferred to the storage ring that feeds light to the beamlines. After the upgrade, electrons from the booster ring will instead go to the accumulator ring, which will reduce the size and spread of the electron beam and accumulate multiple batches or “injections” of electron bunches from the booster ring before transferring bunches to the storage ring.

Shrinking the beam profile in the accumulator ring, together with an innovative technique for swapping electron bunches between ALS rings – and the use of improved magnetic devices called undulators that wiggle the electrons and help to narrow the path of the light they emit – will enable the higher brightness of the upgraded ALS.

This rendering shows a sector of accumulator ring equipment along an inner wall at the Advanced Light Source. (Credit: Scott Burns/Berkeley Lab)

The accumulator ring will also “recycle” incoming electron bunches – via a transfer line from the main storage ring – that have a depleted charge. It will restore them to a higher charge and feed them back into the storage ring.

This electron-bunch recycling, known as “bunch train swap-out,” is a unique design feature of the upgraded ALS that could also prove useful if adopted at other accelerator facilities around the globe. It will reduce the number of lost electrons, in turn reducing the workload for the facility’s production of electrons.

To allow precisely timed electron bunch-train exchanges between the accumulator ring and the booster and storage rings, three transfer lines are needed.

One of these transfer lines will deliver bunches of electrons from the booster ring to the accumulator ring, where the size of the bunches will be reduced and the charge progressively increased, before delivering them via another transfer line to the main storage ring. A third transfer line will allow excess electrons that would otherwise be discarded to reenter the accumulator ring for reuse.

This silicon-based device is one of eight stages of an inductive voltage adder, which is used to drive a “kicker” that kicks electrons from one path to another. (Credit: Marilyn Sargent/Berkeley Lab)

“Every upgrade project should contribute to accelerator technology and push the field forward in some way,” Robin said. “Recent state-of-the art facilities and upgrades in Europe and the U.S. have implemented technology that we are making use of. Using an accumulator with bunch train swap-out injection is one of our main contributions.”

At the leading edge of ‘soft’ and ‘tender’ X-ray science

Robin credited Christoph Steier, who is the Accelerator Systems Lead for the ALS-U project, and his team for developing the bunch train swap-out technique and related technologies that are critical for the facility’s enhanced performance.

The ALS-U project will keep the facility at the forefront of research using “soft” X-rays, which are well-suited to studies of the chemical, electronic, and magnetic properties of materials. Soft X-rays can be used in studies involving lighter elements like carbon, oxygen, and nitrogen, and have a lower energy than “hard” X-rays that can penetrate deeper into samples.

It will also expand access to “tender” X-rays, which occupy an energy range between hard and soft X-rays and can be useful for studies of earth, environmental, energy, and condensed-matter sciences.

But achieving this performance is a tricky feat, noted Daniela Leitner, who is responsible for accelerator removal and installation for the ALS-U project. The main storage ring is housed in thick concrete tunnels designed to fit one ring, and now the upgrade requires that a second ring be squeezed in.

Accumulator ring to function as a mini ALS, will boost performance of new storage ring

“We need to build a ‘mini ALS,’” Leitner said, in the form of the accumulator ring. The accumulator ring will measure about 600 feet in circumference while the main storage ring will be about 640 feet in circumference. It must be installed about 6 1/2 feet above the floor, just 7 inches below the ceiling height in some places – and fit snugly around an inner wall to allow workers to safely navigate the ALS’ tunnels.

Robin noted, “This is a complicated logistical ‘dance.’ It is a very confined space, and there is equipment in the existing tunnel that has to be moved to make room.”

The accumulator ring is designed to be compact, with a reduced weight, footprint, and power consumption compared to the existing storage ring.

The accumulator ring installation – which is enabled by the CD-3a release of funds – will also be carefully orchestrated to minimize disruptions to ALS operations, with installation work fit into regularly scheduled downtimes over the next few years. The ALS typically runs 24/7 outside of scheduled maintenance downtimes.

The plan is to install and test the accumulator ring prior to a planned yearlong shutdown – with the potential to test the new ring even during regular ALS operations. The shutdown period, known as “dark time,” will allow the removal of the existing storage ring and installation of the new storage ring.

Installing the accumulator ring in advance allows the project team to minimize the shutdown period, which will require the removal and replacement of 400 tons of equipment. This final stage of the project is slated to begin in a few years.

This powerful magnetic device is a prototype for 84 “main bend” magnets that will be installed as a part of the new main storage ring. An additional 24 bend magnets will have a different design. The poles are constructed of precision-machined cobalt-iron. The device weighs 1 ton. (Credit: Marilyn Sargent/Berkeley Lab)

The accumulator ring will bring about 80 tons of new equipment into the facility, with construction expected to begin in the summer of 2020. There are dozens of major pieces of equipment to install, including specialized magnetic devices that help to bend and focus the electron beam. These magnetic devices are part of an array of seven pieces that must be installed in each of the 12 ALS sectors and connected by vacuum tubes.

The accumulator ring installation will take an estimated 53,000 worker-hours and requires the placement of thousands of cables.

Prototypes and simulations to ease assembly, installation, troubleshooting

The ALS-U project team has built and acquired prototypes for key components of the accumulator ring, and has constructed models of some of the accumulator ring equipment at their designed height to find the best installation methods. Project crews will also build out fully equipped sections of the accumulator ring to measure their alignment and test the integrated hardware prior to installation to help speed up the process.

Leitner said that about 80 percent of the installation can be assisted by an overhead crane that will lift heavy equipment into the tunnels, but there are also plans for elevated platforms to ease the installation, and customized lifts to enable installation where the crane cannot be used.

Steier said that technical improvements in accelerator simulations should help to troubleshoot and negate potential problems ahead of time that may arise with the commissioning of the accumulator ring and storage ring. The algorithms account for misaligned magnets and power-supply fluctuations, for example, that are common with constructing large accelerator facilities.

“In general, we simulate everything beforehand, and over time these simulations have become more accurate,” he said, to the point that the simulations can actually guide design choices for the accelerator equipment, and could speed up the ALS-U startup process.

Robin said, “I’m really proud of what the team has accomplished over the last few years.”

The Advanced Light Source is a DOE Office of Science User Facility.

See the full article here .

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Bringing Science Solutions to the World
In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

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From Optics & Photonics: “Lasers Extend Study of Matter at Extremes”

From Optics & Photonics

12.27.19
Stewart Wills

Researchers at the Gemini Laser Facility, Central Laser Facility, U.K. The laser was used to drive the creation, through laser wakefield acceleration, of X-rays that can potentially be used to probe processes in solid matter at extremely high temperatures, relevant to fusion energy and studies of planetary interiors. [Image: STFC]

The dynamics of high-energy density (HED) matter—“warm, dense matter,” with the density of a solid but at temperatures as high as 10,000 °C—hold potential insights in domains ranging from studies of planetary interiors to efforts for fusion energy. But getting a grip on those ephemeral, femtosecond-scale processes in these piping-hot materials has been tough.

An international team led by researchers at Imperial College London (ICL), U.K., now reports that it has developed a practical platform for study of these ultrafast HED-matter processes [Physical Review Letters].

The secret lies in tricking out a laser-wakefield accelerator (LWFA) to deliver single-shot, broadband X-ray fluxes that are reportedly 100 times greater than previous measurements—and that pack enough energy to get the job done.

Difficult environment for study

In principle, researchers interested in atomic-scale dynamics in HED matter have a number of options for peering into the maelstrom. But none are perfect. X-ray scattering, for example, reportedly falls short for studying non-equilibrium processes, and the extremely small scattering cross-sections require hefty, high-brightness sources such as X-ray free-electron lasers (XFELs) to get any meaningful result.

A potentially better and more flexible route to studying HED-matter processes is X-ray absorption, which overcomes some of the experimental limitations of scattering techniques. But performing single-shot experiments that could capture the ultrafast dynamics at work requires a combination—high-brightness, broadband X-rays with multi-keV photon energy—that been elusive in practice. Behemoth lasers like the U.S. National Ignition Facility, for example, can supply plenty of photon energy, but in pulses on the scale a hundred picoseconds or even longer. Synchrotron sources also lack ultrashort duration, while XFEL pulses, though short enough, lack the required broadband operation.

Realizing the LWFA advantage

LWFAs, which use laser-driven plasmas to accelerate electrons and create by-product X-rays through betatron radiation, could potentially circumvent these problems. That’s because LWFAs are, according to the researchers behind the new study, “the only currently available sources that provide bright bursts of broadband X-rays on the femtosecond timescale.”

But heretofore, the source fluxes and photon energies available in LWFAs have required integration across many shots to achieve the energy needed to study warm dense matter. Getting a true, femtosecond-scale view of electron dynamics in HED matter would require an LWFA that could pack sufficient energy into a single, ultrafast broadband pulse.

In the setup for generating ultrashort X-ray bursts, the driving laser passes through a gas cell (left), accelerating electrons and creating a plasma wakefield that gives rise to high-energy X-rays that exit through a pinhole (right). [Image: Brendan Kettle]

The ICL-led team, helmed by Stuart Mangles and by first author Brendan Kettle, sought to achieve just that, with a novel setup. The setup begins with an extremely powerful driving laser, the 200-TW Gemini Laser at the U.K.’s Central Laser Facility at Rutherford Appleton Laboratory.

STFC Rutherford Appleton Laboratory at Harwell in Oxfordshire, UK

The laser’s 800-nm-wavelength beam is focused into a helium gas cell, where it strips electrons from the gas and creates an electron plasma wave in the laser’s wake. The high laser fields subsequently accelerate the electrons to GeV-scale energies, forcing out high-energy betatron X-rays. A sacrificial length of polyimide plastic tape absorbs the surplus laser energy and allows the X-rays to pass through to the sample.

In measurements with their setup, the researchers found that the use of the powerful Gemini Laser to drive an LWFA allowed the creation of single shots with energies in the 5-keV range, and with photon flxes on the order of 1.2 million per eV. The team was able to use those pulses to perform X-ray absorption near-edge structure experiments on a piece of room-temperature titanium foil. And numerical simulations by the team suggest that it should work as a platform for ultrafast electron processes in HED matter as well.

Higher-intensity lasers ahead

The team believes that such experiments will become increasingly viable as new and even higher-intensity driving lasers (such as those at the European Extreme Light Infrastructure) come online. The researchers envision setups in which these LWFA-driving lasers are deployed in tandem with XFELs or other high-energy lasers that are used to push the samples to HED states, which are then probed with the LWFA-generated X-rays in ultrafast and brilliant single shots.

“We will now be able to probe warm dense matter much more efficiently, and in unprecedented resolution,” first author Kettle said in an ICL press release accompanying the work. That, he suggested, “could accelerate discoveries in fusion experiments and astrophysics, such as the internal structure and evolution of planets including the Earth itself.”

See the full article here .

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

From Imperial College London and STFC: “Ultrashort x-ray technique will probe conditions found at the heart of planets”

From Science and Technology Facilities Council

and

From Imperial College London

19 December 2019
Hayley Dunning

Working with the Gemini Laser. Credit: STFC

Combining powerful lasers and bright x-rays, Imperial and STFC researchers have demonstrated a technique that will allow new extreme experiments.

The new technique would be able to use a single x-ray flash to capture information about extremely dense and hot matter, such as can be found inside gas giant planets or on the crusts of dead stars.

The same conditions are also found in fusion experiments, which are trying to create a new source of energy that mimics the Sun.

______________________________________
We will now be able to probe warm dense matter much more efficiently and in unprecedented resolution.
Dr Brendan Kettle
______________________________________

The technique, reported this week in Physical Review Letters, was developed by a team led by Imperial College London scientists working with colleagues including those at the UK’s Central Laser Facility at the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory [below], and was funded by the European Research Council.

The researchers wanted to improve ways to study ‘warm dense matter’ – matter that has the same density as a solid, but is heated up to 10,000?C. Researchers can create warm dense matter in the lab, recreating the conditions in the hearts of planets or crucial for fusion power, but it is difficult to study.

Accelerating discoveries

The team used the Gemini Laser, which has two beams – one which can create the conditions for warm dense matter, and one which can create ultrashort and bright x-rays to probe the conditions inside the warm dense matter.

STFC Gemini Laser

Previous attempts using lower-powered lasers required 50-100 x-ray flashes to get the same information that the new technique can gain in just one flash. The flashes last only femtoseconds (quadrillionths of a second), meaning the new technique can reveal what is happening within warm dense matter across very short timescales.

First author Dr Brendan Kettle, from the Department of Physics at Imperial, said: “We will now be able to probe warm dense matter much more efficiently and in unprecedented resolution, which could accelerate discoveries in fusion experiments and astrophysics, such as the internal structure and evolution of planets including the Earth itself.”

The technique could also be used to probe fast-changing conditions inside new kinds of batteries and memory storage devices.

Answering key questions

In the new study, the team used their technique to examine a heated sample of titanium, successfully showing that it could measure the distribution of electrons and ions.

Lead researcher Dr Stuart Mangles, from the Department of Physics at Imperial, said: “We are planning to use the technique to answer key questions about how the electrons and ions in this warm dense matter ‘talk’ to each other, and how quickly can energy transfer from the electrons to the ions.”

The Central Laser Facility’s Gemini Laser is currently one of the few places the right conditions for the technique can be created, but as new facilities start operating around the world, the team hope the technique can be expanded and used to do a whole new class of experiments.

Dr Rajeev Pattathil, Gemini Group Leader at the Central Laser Facility, said: “With ultrashort x-ray flashes we can get a freeze-frame focus on transient or dynamic processes in materials, revealing key new fundamental information about materials here and in the wider Universe, and especially those in extreme states.”

See the full article here .

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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.

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STFC Rutherford Appleton Laboratory at Harwell in Oxfordshire, UK

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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.

From SLAC National Accelerator Lab: “Scientists discover how proteins form crystals that tile a microbe’s shell”

From SLAC National Accelerator Lab

December 17, 2019
Glennda Chui

In this illustration, protein crystals join six-sided ’tiles’ forming at top left and far right, part of a protective shell worn by many microbes. A new study zooms in on the first steps of crystal formation and helps explain how microbial shells assemble themselves so quickly. Credit: Greg Stewart/SLAC National Accelerator Laboratory

A new understanding of the nucleation process could shed light on how the shells help microbes interact with their environments, and help people design self-assembling nanostructures for various tasks.

Many microbes wear beautifully patterned crystalline shells, which protect them from a harsh world and can even help them reel in food. Studies at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have revealed this food-reeling process and shown how shells assemble themselves from protein building blocks.

Now the same team has zoomed in on the very first step in microbial shell-building: nucleation, where squiggly proteins crystallize into sturdy building blocks, much like rock candy crystallizes around a string dipped into sugar syrup.

The results, published today in the Proceedings of the National Academy of Sciences, could shed light on how the shells help microbes interact with other organisms and with their environments, and also help scientists design self-assembling nanostructures for various tasks.

Jonathan Herrmann, a graduate student in Professor Soichi Wakatsuki’s group at SLAC and Stanford, collaborated with the structural molecular biology team at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) on the study.

SLAC/SSRL

They scattered a powerful beam of X-rays off protein molecules that were floating in a solution to see how the atomic structures of the molecules changed as they nucleated into crystals. Meanwhile, other researchers made a series of cryogenic electron microscope (cryo-EM) images at various points in the nucleation process to show what happened over time.

They found out that crystal formation takes place in two steps: One end of the protein molecule nucleates into crystal while the other end, called the N-terminus, continues to wiggle around. Then the N-terminus joins in, and the crystallization is complete. Far from being a laggard, the N-terminus actually speeds up the initial nucleation step ­– although exactly how it does this is still unknown, the researchers said – and this helps explain why microbial shells can form so quickly and efficiently.

Some of the X-ray data was collected at Lawrence Berkeley National Laboratory’s Advanced Light Source, which like SSRL is a DOE Office of Science user facility.

LBNL ALS

Researchers from the University of British Columbia and from Professor Lucy Shapiro’s laboratory at Stanford also contributed to this work, funded in part by the National Institute of General Medical Sciences and the Chan Zuckerberg Biohub. Work in Wakatsuki’s labs at SLAC and Stanford was funded by a Laboratory Directed Research and Development grant from SLAC, the DOE Office of Science’s Office of Biological and Environmental Research, and Stanford’s Precourt Institute for Energy.

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SLAC/LCLS

SLAC/LCLS II projected view

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.
The scientists used special software, designed by van den Bedem, that is highly sensitive to identifying protein movement from X-ray crystallography data to interpret the results, revealing never-before-seen motions that play a key role in catalyzing complex reactions, such as breaking down antibiotics. Next, the researchers hope to use LCLS to obtain room temperature structures of other enzymes to get a better look at how the motions occurring within them help move along reactions.
SSRL and LCLS are DOE Office of Science user facilities. This work was funded by the DOE Office of Science and the National Institutes of Health, among other sources.