From SLAC National Accelerator Lab: “A day in the life of a midnight beam master”

From SLAC National Accelerator Lab

April 16, 2019 [Just today 4.23.19 in social media]
Angela Anderson

In SLAC’s accelerator control room, shift lead Ben Ripman and a team of operators fine-tune X-ray beams for science experiments around the clock.

When is a day not a day? When you work in the central nervous system of the world’s longest linear accelerator, open 24-7.

“There’s a constant cycle of people coming and going,” says Ben Ripman, an operations engineer at the Department of Energy’s SLAC National Accelerator Laboratory.

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Ben Ripman, operations engineer at the SLAC accelerator control room (Angela Anderson/SLAC National Accelerator Laboratory)

He might start at 8 a.m., at 4 p.m. or at midnight. But the shift rotations are no barrier to his passion for the job – leading a team of control room operators who deliver brilliant X-ray beams for scientific experiments.

Control room operators spend most of their workdays (or nights) in a room filled with monitors, three deep and crowded with numbers, charts and graphs. Those displays track the status of thousands of devices and systems in the linear accelerator that runs through a tunnel below Highway 280 and feeds SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS).

SLAC/LCLS

The accelerator boosts electrons to almost the speed of light and then wiggles them between magnets to generate X-rays. That X-ray light is formed into pulses and optimized for materials science, biology, chemistry, and physics experiments.

The entire operation is monitored in the control room, which also serves SPEAR3, the accelerator that produces X-rays for the Stanford Synchrotron Radiation Lightsource (SSRL).

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SLAC SPEAR3

SLAC/SSRL

Another set of monitors, staffed by SLAC Facilities, tracks water, compressed air and electricity systems that serve the lab campus.

Ripman and his fellow operators are experts in reading these digital vital signs. But they are also some of the most knowledgeable people at the lab when it comes to the entire physical machine.

“We know the accelerator from beginning to end,” he says. “When an operator adjusts something from the control room, they can picture that machine part and what it is doing.”

For LCLS, they measure the amount of energy in individual X-ray pulses being fed to experimental hutches and often spend hours improving the pulses: tweaking magnets, adjusting the undulators, tuning the shape and length of the electron bunches.

Some days the control room is quiet, and the operators focus on training and individual projects. On other, more challenging days when the machine is running in exotic modes, they work elbow to elbow with physicists.

“We love this machine, but the accelerator was built decades ago and can be cantankerous,” Ripman explains. “When things do go wrong, it’s like a game of pickup sticks – one problem triggers another and you need to know how it all fits together.”

An important part of the job is knowing who to call for help. “We wake up a lot of people in the middle of the night,” Ripman says with a smile.

Control room operators also make sure everyone who goes into the accelerator tunnel stays safe.

There are two ways to get into the accelerator. For minor repairs and inspections, people take keys from special key banks that block the accelerator from turning on until all the keys have been returned. On official maintenance days, the doors are thrown open.

“On those days, maintenance crews, engineers and physicists descend into the tunnel and swarm the machine to resolve as many issues as possible before we have to summon them out again,” Ripman says. “We search the machine to make sure everyone is out before it’s turned back on.”

Almost all of the displays in the control room were designed by the operators, he says. “We are known to hide ‘Easter eggs’ in them, but you have to get in our good graces to find out about them.”

New operators take more than a year to get trained and proficient, Ripman says. “People come with a physics degree, but there is not a lot of formal coursework you can take on accelerator operations – it’s a lot of on-the-job training.”

It was that hands-on learning that drew him to the job in 2010.

“I was a nerd in high school,” Ripman admits proudly, “Stephen Hawking was my hero.” After studying physics and astronomy in college, Ripman worked as a contractor for NASA before joining SLAC. On his off hours, he plays board games and travels several times a year for card tournaments. He also loves hiking, skiing and snowboarding, and is a member of the Stanford University Singers.

His favorite thing about the job? “My coworkers,” he says. “I have the privilege of working with smart, fun, quirky people. We all get along quite well, and there’s a great camaraderie.”

Operators leave sticky notes with jokes or short messages for the next shift and share stories about their days and nights in the accelerator’s brain.

Like the one about a ghost calling from an abandoned tunnel. But that’s a tale for another night…

LCLS and SSRL are DOE Office of Science user facilities.

See the full article here .


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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.

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From SLAC National Accelerator Lab: “Dancing atoms in perovskite materials provide insight into how solar cells work”

From SLAC National Accelerator Lab

November 6, 2018
Ali Sundermier

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When the researchers scattered neutrons off the perovskite material (red beam) they were able to measure the energy the neutrons lost or gained (white and blue lines). Using this information, they were able to see the structure and motion of the atoms and molecules within the material (arrangement of blue and purple spheres). (Greg Stewart/SLAC National Accelerator Laboratory)

A new study is a step forward in understanding why perovskite materials work so well in energy devices and potentially leads the way toward a theorized “hot” technology that would significantly improve the efficiency of today’s solar cells.

A closer look at materials that make up conventional solar cells reveals a nearly rigid arrangement of atoms with little movement. But in hybrid perovskites, a promising class of solar cell materials, the arrangements are more flexible and atoms dance wildly around, an effect that impacts the performance of the solar cells but has been difficult to measure.

In a paper published in the PNAS, an international team of researchers led by the U.S. Department of Energy’s SLAC National Accelerator Laboratory has developed a new understanding of those wild dances and how they affect the functioning of perovskite materials. The results could explain why perovskite solar cells are so efficient and aid the quest to design hot-carrier solar cells, a theorized technology that would almost double the efficiency limits of conventional solar cells by converting more sunlight into usable electrical energy.

Piece of the puzzle

Perovskite solar cells, which can be produced at room temperature, offer a less expensive and potentially better performing alternative to conventional solar cell materials like silicon, which have to be manufactured at extremely high temperatures to eliminate defects. But a lack of understanding about what makes perovskite materials so efficient at converting sunlight into electricity has been a major hurdle to producing even higher efficiency perovskite solar cells.

“It’s really only been over the last five or six years that people have developed this intense interest in solar perovskite materials,” says Mike Toney, a distinguished staff scientist at SLAC’s Stanford Synchrotron Radiation Light Source (SSRL) who led the study.

SLAC/SSRL

“As a consequence, a lot of the foundational knowledge about what makes the materials work is missing. In this research, we provided an important piece of this puzzle by showing what sets them apart from more conventional solar cell materials. This provides us with scientific underpinnings that will allow us to start engineering these materials in a rational way.”

Keeping it hot

When sunlight hits a solar cell, some of the energy can be used to kick electrons in the material up to higher energy states. These higher-energy electrons are funneled out of the material, producing electricity.

But before this happens, a majority of the sun’s energy is lost to heat with some fraction also lost during the extraction of usable energy or due to inefficient light collection. In many conventional solar cells, such as those made with silicon, acoustic phonons – a sort of sound wave that propagates through material – are the primary way that this heat is carried through the material. The energy lost by the electron as heat limits the efficiency of the solar cell.

In this study, theorists from the United Kingdom, led by Imperial College Professor Aron Walsh and electronic structure theorists Jonathan Skelton and Jarvist Frost, provided a theoretical framework for interpreting the experimental results. They predicted that acoustic phonons traveling through perovskites would have short lifetimes as a result of the flexible arrangements of dancing atoms and molecules in the material.

Stanford chemists Hema Karunadasa and Ian Smith were able to grow the large, specialized single crystals that were essential for this work. With the help of Peter Gehring, a physicist at the NIST Center for Neutron Research, the team scattered neutrons off these perovskite single crystals in a way that allowed them to retrace the motion of the atoms and molecules within the material. This allowed them to precisely measure the lifetime of the acoustic phonons.

The research team found that in perovskites, acoustic phonons are incredibly short-lived, surviving for only 10 to 20 trillionths of a second. Without these phonons trucking heat through the material, the electrons might stay hot and hold onto their energy as they’re pulled out of the material. Harnessing this effect could potentially lead to hot-carrier solar cells with efficiencies that are nearly twice as high as conventional solar cells.

In addition, this phenomenon could explain how perovskite solar cells work so well despite the material being riddled with defects that would trap electrons and dampen performance in other materials.

“Since phonons in perovskites don’t travel very far, they end up heating the area surrounding the electrons, which might provide the boost the electrons need to escape the traps and continue on their merry way,” Toney says.

Transforming energy production

To follow up on this study, researchers at the Center for Hybrid Organic-Inorganic Semiconductors for Energy (CHOISE) Energy Frontier Research Center led by DOE’s National Renewable Energy Laboratory will investigate this phenomenon in more complicated perovskite materials that are shown to be more efficient in energy devices. They would like to figure out how changing the chemical make-up of the material affects acoustic phonon lifetimes.

“We need to fundamentally transform our energy system as quickly as possible,” says Aryeh Gold-Parker, who co-led the study as a PhD student at Stanford University and SLAC. “As we move toward a low-carbon future, a very important piece is having cheap and efficient solar cells. The hope in perovskites is that they’ll lead to commercial solar panels that are more efficient and cheaper than the ones on the market today.”

The research team also included scientists from NIST; the University of Bath and Kings College London, both in the UK; and Yonsei University in Korea.

SSRL is a DOE Office of Science user facility. This work was supported by the DOE’s Office of Science and the Solar Energy Technologies Office; the Engineering and Physical Sciences Research Council; the Royal Society; and the Leverhulme Trust.

See the full article here .


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From SLAC National Accelerator Lab: “Catching the dance of antibiotics and ribosomes at room temperature”

From SLAC National Accelerator Lab

August 6, 2018
Ali Sundermier

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Hasan DeMirci refers to ribosomes as the 3D printers of the human body because they synthesize proteins, which are essential to life. (Dawn Harmer/SLAC National Accelerator Laboratory)

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Interns in DeMirci’s lab help grow ribosome crystals. Once grown and suspended in a special chemical solution called “mother liquor,” the crystals are imaged at the LCLS to uncover how they interact with antibiotics. (Dawn Harmer/SLAC National Accelerator Laboratory)

Antibiotics have been a pillar of modern medicine since the 1940s. Streptomycin, which belongs to a class of antibiotics called aminoglycosides, was the first hint of light in the millennia-long search for a treatment for tuberculosis, which remains one of the deadliest infectious diseases in human history.

Today, aminoglycosides are the most commonly prescribed antibiotics in the world due to their low cost and high effectiveness in tackling a broad spectrum of bacterial infections. But they also bring along side effects that can have lifelong impacts. Depending on the dosage and the particular antibiotic, an estimated 10 to 20 percent of patients who take aminoglycosides suffer kidney damage and 20 to 60 percent end up with irreversible hearing loss.

Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory have developed a new imaging technique to better understand the mechanisms that lead to hearing loss when aminoglycosides are introduced to the body. Using the lab’s Linac Coherent Light Source (LCLS) X-ray laser and Stanford Synchrotron Lightsource (SSRL), SLAC researchers, in collaboration with researchers at Stanford University, were able to observe interactions between the drugs and bacterial ribosomes at both extremely low and room temperatures, revealing never-before-seen details.

SLAC LCLS

SLAC/SSRL

They also demonstrated how small modifications to the antibiotics can lead to dramatic changes in ribosome shape that eliminate hearing loss. The research could lead to a better understanding of which parts of a drug molecule cause unwanted reactions in the body, which will enable the development of more effective antibiotics with fewer side effects.

The group was led by research associate and senior author Hasan DeMirci. Their results were published in Nucleic Acids Research.

3D printing proteins

Hasan DeMirci refers to ribosomes – tiny molecular machines made up of tangles of RNA and proteins clumped together and intricately wired like ramen noodles in soup – as “the 3D printers of the human body.” The ribosomes synthesize proteins using the genetic information contained in DNA, “building our bodies from the ground up.”

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Ribosomes (shown here) are tiny molecular machines made up of tangles of RNA and proteins clumped together and intricately wired like ramen noodles in soup. (Hasan DeMirci/SLAC National Accelerator Laboratory)

“While one subunit of the ribosome, its brain, deciphers and translates the genetic code, the other, its hands, links together amino acids to form proteins,” DeMirci said.

Unlike viruses, which have to leech off hosts to survive, bacteria have their own ribosomes, which is where antibiotics come into play. Bacterial ribosomes are the targets of many antibiotics. So-called “cidal” antibiotics like aminoglycosides function by attacking the brains of bacterial ribosomes, causing them to make mistakes and fill the cells with protein-like garbage molecules.

“It’s like a house with a lot of hoarded junk,” DeMirci says. “There’s no going back. From that point the bacteria just die.”

The problem with this strategy is that human cells contain energy-producing factories called mitochondria that have their very own ribosomes – and since those ribosomes are dangerously similar to those found in bacteria, they’re also vulnerable to antibiotic attack.

“We’re killing the bacteria, but the same drug gets into our mitochondria and destroys the ribosomes there,” DeMirci says. “Now we cannot produce those enzymes that power us. You take an antibiotic and you start losing your hearing, your kidney fails.”

Insights into molecular machinery

DeMirci has a strong interest in aminoglycosides because he can use them to gain insight into the molecular machinery of the ribosome.

“What I really want to know is what those drugs can teach us about how ribosomes decipher the genetic code,” DeMirci said. “Drugs give us an opportunity to stop that process at different stages to understand how each and every step is catalyzed by the ribosome.”

To better understand this process, he struck up a collaboration with Anthony Ricci, a biophysicist and professor of medicine at Stanford who focuses on the inner ear. In previous research, Ricci found that aminoglycosides infiltrate specialized channels to target the sensory cells essential to hearing.

“You can think of it as a roach motel,” Ricci says. “The drugs can get in but they can’t get out. They start to build up, binding to the ribosomes and altering protein synthesis. This puts a huge metabolic load on the sensory cells, which eventually leads to their deaths.”

A major goal of Ricci’s lab has been to design and develop new aminoglycosides that kill bacteria but cannot squeeze through the channel. In order to do this, the researchers need to understand exactly how the aminoglycosides interact with the ribosomes so they can modify parts of the drug without weakening its bacteria-killing properties.

Defrosting interactions

The best way to reach this understanding, researchers have found, is through a technique called X-ray crystallography. In X-ray crystallography, researchers use the patterns formed when a beam of X-rays scatters off a crystal sample to form a 3D model of how its atoms and molecules are arranged. This technique allows researchers to observe how a drug binds to a ribosome.

While the key interactions in these processes happen at body temperature, around 37 degrees Celsius, X-ray crystallography usually has to be done at extremely low, or cryogenic, temperatures, around minus 180 degrees Celsius. This leads to gaps in the data, obscuring tiny details that could greatly inform future experiments.

“Our bodies are warm, so the important biology is happening at body temperature,” DeMirci said, “but in crystallography everything is frozen. When you cool these processes down, you miss out on thermal fluctuations, tiny movements that could change your understanding of how the drugs and ribosomes are behaving.”

In order to design better antibiotics, they need to get as close a view as they can of this interaction happening under physiological conditions. At the LCLS, using a technique called serial femtosecond crystallography, DeMirci is able to catch the intricate waltz of the drugs and ribosomes at room temperature. Rather than freeze the ribosome crystals, the researchers suspend them in ‘mother liquor,’ a special chemical solution they were grown in that keeps them stable, so they are “swimming happily, still wiggling and fluctuating,” he says.

The crystals travel from a reservoir to the interaction region through a single capillary, like a garden hose. Once in the interaction region, the crystals are zapped with a beam of X-rays from the LCLS, which scatters off of them into a detector and provides the researchers with patterns they can use to build detailed 3D models of the ribosome before and after they’ve bound with the drugs. They then use these models to piece together a simulation of the interaction.

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At LCLS, crystallized ribosomes travel through a capillary into the interaction region, where they are zapped with a beam of X-rays. The X-rays scatter off the crystals into a detector, providing the researchers with patterns they can use to build detailed 3D models of interactions between the drug and ribosome. (Greg Stewart/SLAC National Accelerator Laboratory)

Uncovering hidden wiggles

To demonstrate their technique, the researchers imaged modified and unmodified drugs binding to ribosomes at both cryogenic and room temperatures to see if they could catch any differences. They found that the drug molecules were less flexible at cryogenic temperatures: Tiny wiggles essential to a better understanding of their interactions with ribosomes were frozen in place.

“Despite the fact that we’ve recorded hundreds of thousands of structures of ribosomal interactions, less than a handful of new-generation drugs have been designed based on these cryogenic structures,” DeMirci said. “That’s because every small interaction makes a huge difference, even a single hydrogen bond.”

With the images taken at room temperature, Ricci’s group identified a site where the drug could be modified without altering its effectiveness.

“We now have some idea that when the drug binds with the ribosome, a global change occurs in the ribosome that might actually be important for the function of the antibiotic and the sensitivity of the ribosome,” Ricci said.

Refining the jigsaw pieces

In the next phase of experiments, DeMirci hopes to design a setup in which the antibiotics aren’t introduced until the last second before the ribosome is imaged so that they can watch as it binds to the ribosome, rather than just taking images before and after.

Up to this point, Ricci said, his group had been doing drug synthesis with very little information or insight into how the antibiotic interacts with the ribosome.

“What this paper and overall collaboration allow is a direct investigation of the drug-ribosome interaction,” he said. “It’s like having more defined pieces to the jigsaw puzzle. You don’t have to guess about what’s happening.”

Developing antibiotics that can fight off drug-resistant bacteria with minimal side effects is essential because the rise of antibiotic resistant strains is currently the biggest threat to modern medicine, DeMirci said.

“Every year more than a million people die from tuberculosis and nearly half a million are HIV positive,” he said. “People don’t usually die from HIV or cancer, they die because their immune system is suppressed and they can’t fight off bacterial infections. That’s when you need antibiotics. But what if you don’t have one that’s effective against the resistant strains? That’s exactly what’s happening right now. This research can help us make informed decisions when designing the next generation of drugs.”

The research team included scientists from LCLS; SSRL; SLAC’s Biosciences Division; the Stanford PULSE Institute; and the Stanford School of Medicine.

See the full article here .


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Please help promote STEM in your local schools.

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

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From SLAC Lab: “A SLAC Legend Gives the Lab His Lifetime Collection of Precious Foils”


SLAC Lab

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Farrel Lytle’s career-long collection of calibration foils, including several extremely rare elements, is now available to SLAC users at SSRL. (Courtesy of Farrel Lytle)

April 23, 2018
Bobbi Fagone

The foils, each made from a single chemical element, are used to calibrate X-ray equipment at SLAC’s SSRL synchrotron, and were donated by long-time user, Farrel Lytle.

SLAC/SSRL

Scientists who conduct experiments at the Stanford Radiation Synchrotron Lightsource (SSRL) have received an unusual and highly valuable gift—a library of element calibration foils for a technique used to understand the structure of matter called X-ray absorption spectroscopy.

SSRL, a DOE Office of Science user facility at the SLAC National Accelerator Laboratory, offers scientists extremely bright X-ray beams to probe samples at the atomic and molecular level. X-ray absorption spectroscopy is used in a variety of studies, including physics, materials science, chemistry (such as the study of catalysts used to promote and control many chemical reactions), earth science and biology.

The foils were donated by entrepreneur, scientist and X-ray spectroscopy pioneer, Farrel W. Lytle, and include precious metals such as gold, silver, platinum, iridium and many other elements in the periodic table.

“The machines on the beam lines at SSRL are not always absolutely correct,” Lytle explains. “They may vary a little bit. So, scientists can use these pure elements to do a measurement, and then adjust their instrumentation so it’s exactly right.”

Each foil is a tiny strip of metal one-fifth of the thickness of a postage stamp, similar to a piece of cellophane. “You can get some of these elements in bulk, but not thin like this,” says Lytle. This is vital because the X-rays need to penetrate the element to complete the measurement. Over the years, Farrel made many of the foils himself or had them created by a machinist. But the entire collection, valued at $10,000, took a lifetime to build.

“I measured my first X-ray edge on a synchrotron in 1974 at SSRL,” Lytle recalls. “But I had been working on this problem in my own lab with my own equipment since 1960. Because whenever you change the experiment, you change the chemistry and you need new reference compounds.

“This collection of thin metal foils may not look like much, but it represents all of the different elements that I worked on during my career,” he continues. “Some of those most difficult to obtain are of interest for current projects at SSRL. While many elements are easily available as pure, thin foils (such as copper, silver and gold) many others are hard, brittle, rare and not available commercially. So, these elements would have to be created using difficult and/or expensive techniques.”

Fortunately, the foils are not consumed in the experiments when used as reference samples, so they can be used over and over again. Lytle describes the process as “just like shining a light on them.” The measured X-ray spectrum (a fingerprint-type of X-ray picture) of the pure metal is used to calibrate the experimental apparatus, and also to observe the changes to the atomic and electronic environment of the same type of element when exposed to the conditions of the experiment.

An SSRL Trailblazer Gives Back

A long-time visiting user of SSRL, Lytle is a well-known SLAC personality. Formerly a Boeing researcher, Lytle’s experiments at SSRL in the 1970s furthered the science of X-ray spectroscopy. He also authored and co-authored early papers describing the synchrotron X-ray technique and its first applications.

In 1998, the first Farrel W. Lytle Award was presented to him at an annual conference and bears his name to this day. This annual award recognizes important technical or scientific accomplishments in synchrotron radiation-based science and collaboration between visiting scientists and staff at SSRL.

“Every time I went to SSRL, I thought, ‘How wonderful that I get to work on this thing. All I have to do is have an idea, get it approved and it’s free,’” says Lytle. “I owe them! Donating these foils was a chance for me to give back.”

At 83, Lytle continues to work as the sole proprietor of a business he founded in 1974. He’s also busy building a special kind of X-ray detector that is used specifically in synchrotron experiments. “At the moment I have more business than I can handle,” he says. “Right now, I’m building three of these things.”

How about retiring? Maybe just go play golf? “I don’t play golf,” Lytle laughs. “It just ruins a good walk.”

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Farrel and Manetta Lytle at their beloved desert home in Eagle Valley, Lincoln County, Nevada. (Courtesy of Farrel Lytle)

See the full article here .

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From SLAC: “Scientists Use Machine Learning to Speed Discovery of Metallic Glass”


SLAC Lab

April 13, 2018
Glennda Chui

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Fang Ren, who developed algorithms to analyze data on the fly while a postdoctoral scholar at SLAC, at a Stanford Synchrotron Radiation Lightsource beamline where the system has been put to use. (Dawn Harmer/SLAC National Accelerator Laboratory)

SLAC and its collaborators are transforming the way new materials are discovered. In a new report, they combine artificial intelligence and accelerated experiments to discover potential alternatives to steel in a fraction of the time.

Blend two or three metals together and you get an alloy that usually looks and acts like a metal, with its atoms arranged in rigid geometric patterns.

But once in a while, under just the right conditions, you get something entirely new: a futuristic alloy called metallic glass that’s amorphous, with its atoms arranged every which way, much like the atoms of the glass in a window. Its glassy nature makes it stronger and lighter than today’s best steel, plus it stands up better to corrosion and wear.

Even though metallic glass shows a lot of promise as a protective coating and alternative to steel, only a few thousand of the millions of possible combinations of ingredients have been evaluated over the past 50 years, and only a handful developed to the point that they may become useful.

Now a group led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory, the National Institute of Standards and Technology (NIST) and Northwestern University has reported a shortcut for discovering and improving metallic glass – and, by extension, other elusive materials – at a fraction of the time and cost.

The research group took advantage of a system at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) that combines machine learning – a form of artificial intelligence where computer algorithms glean knowledge from enormous amounts of data – with experiments that quickly make and screen hundreds of sample materials at a time.

SLAC/SSRL

This allowed the team to discover three new blends of ingredients that form metallic glass, and to do this 200 times faster than it could be done before, they reported today in Science Advances.

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(Yvonne Tang/SLAC National Accelerator Laboratory)

“It typically takes a decade or two to get a material from discovery to commercial use,” said Northwestern Professor Chris Wolverton, an early pioneer in using computation and AI to predict new materials and a co-author of the paper. “This is a big step in trying to squeeze that time down. You could start out with nothing more than a list of properties you want in a material and, using AI, quickly narrow the huge field of potential materials to a few good candidates.”

The ultimate goal, he said, is to get to the point where a scientist could scan hundreds of sample materials, get almost immediate feedback from machine learning models and have another set of samples ready to test the next day – or even within the hour.

Over the past half century, scientists have investigated about 6,000 combinations of ingredients that form metallic glass, added paper co-author Apurva Mehta, a staff scientist at SSRL: “We were able to make and screen 20,000 in a single year.”

Just Getting Started

While other groups have used machine learning to come up with predictions about where different kinds of metallic glass can be found, Mehta said, “The unique thing we have done is to rapidly verify our predictions with experimental measurements and then repeatedly cycle the results back into the next round of machine learning and experiments.”

There’s plenty of room to make the process even speedier, he added, and eventually automate it to take people out of the loop altogether so scientists can concentrate on other aspects of their work that require human intuition and creativity. “This will have an impact not just on synchrotron users, but on the whole materials science and chemistry community,” Mehta said.

The team said the method will be useful in all kinds of experiments, especially in searches for materials like metallic glass and catalysts whose performance is strongly influenced by the way they’re manufactured, and those where scientists don’t have theories to guide their search. With machine learning, no previous understanding is needed. The algorithms make connections and draw conclusions on their own, and this can steer research in unexpected directions.

“One of the more exciting aspects of this is that we can make predictions so quickly and turn experiments around so rapidly that we can afford to investigate materials that don’t follow our normal rules of thumb about whether a material will form a glass or not,” said paper co-author Jason Hattrick-Simpers, a materials research engineer at NIST. “AI is going to shift the landscape of how materials science is done, and this is the first step.”

Strength in Numbers

The paper is the first scientific result associated with a DOE-funded pilot project where SLAC is working with a Silicon Valley AI company, Citrine Informatics, to transform the way new materials are discovered and make the tools for doing that available to scientists everywhere.

Founded by former graduate students from Northwestern and Stanford University, Citrine has created a materials science data platform where data that had been locked away in published papers, spreadsheets and lab notebooks is stored in a consistent format so it can be analyzed with AI specifically designed for materials.

“We want to take materials and chemical data and use them effectively to design new materials and optimize manufacturing,” said Greg Mulholland, founder and CEO of the company. “This is the power of artificial intelligence: As scientists generate more data, it learns alongside them, bringing hidden trends to the surface and allowing scientists to identify high-performance materials much faster and more effectively than relying on traditional, purely human-driven materials development.”

Until recently, thinking up, making and assessing new materials was painfully slow. For instance, the authors of the metallic glass paper calculated that even if you could cook up and examine five potential types of metallic glass a day, every day of the year, it would take more than a thousand years to plow through every possible combination of metals. When they do discover a metallic glass, researchers struggle to overcome problems that hold these materials back. Some have toxic or expensive ingredients, and all of them share glass’s brittle, shatter-prone nature.

Over the past decade, scientists at SSRL and elsewhere have developed ways to automate experiments so they can create and study more novel materials in less time. Today, some SSRL users can get a preliminary analysis of their data almost as soon as it comes out with AI software developed by SSRL in conjunction with Citrine and the CAMERA project at DOE’s Lawrence Berkeley National Laboratory.

“With these automated systems we can analyze more than 2,000 samples per day,” said Fang Ren, the paper’s lead author, who developed algorithms to analyze data on the fly and coordinated their integration into the system while a postdoctoral scholar at SLAC.

Experimenting with Data

In the metallic glass study, the research team investigated thousands of alloys that each contain three cheap, nontoxic metals.

They started with a trove of materials data dating back more than 50 years, including the results of 6,000 experiments that searched for metallic glass. The team combed through the data with advanced machine learning algorithms developed by Wolverton and graduate student Logan Ward at Northwestern.

Based on what the algorithms learned in this first round, the scientists crafted two sets of sample alloys using two different methods, allowing them to test how manufacturing methods affect whether an alloy morphs into a glass.

Both sets of alloys were scanned by an SSRL X-ray beam, the data fed into the Citrine database, and new machine learning results generated, which were used to prepare new samples that underwent another round of scanning and machine learning.

By the experiment’s third and final round, Mehta said, the group’s success rate for finding metallic glass had increased from one out of 300 or 400 samples tested to one out of two or three samples tested. The metallic glass samples they identified represented three different combinations of ingredients, two of which had never been used to make metallic glass before.

See the full article here .

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From SLAC: “Q&A: Sam Webb Teaches X-Ray Science from a Remote Classroom” Interview


SLAC Lab

December 20, 2017
Amanda Solliday

The staff scientist at the Stanford Synchrotron Radiation Lightsource discusses his research and teaching, which includes training an international group of students to conduct geobiology experiments at the synchrotron from an island about 350 miles away.

When Sam Webb teaches, he shows that science is a part of everyday life. For him, it’s important that students learn science does not need to be intimidating.

Webb is a staff scientist at the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy’s SLAC National Acceleratory Laboratory. He started working at SSRL in the fall of 2001 as a postdoctoral researcher.

SLAC/SSRL

Over the years, he’s helped with the annual Kids Night at SLAC and other lab outreach events. Webb often visits local classrooms to give science lessons, from demonstrations at his daughter’s preschool to guest lectures at high schools and colleges.

Webb earned his undergraduate and master’s degree at Caltech and a PhD at Northwestern University. His commitment to teaching and strong Caltech connection recently led to a unusual development where graduate students in a geobiology course at the university can watch their X-ray experiments run at SSRL without leaving Southern California.

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Sam Webb, staff scientist, lectures about studying the color of dinosaurs with X-rays at SLAC’s 2017 Kids’ Night. (Dawn Harmer/SLAC National Accelerator Laboratory)

Q: Why do you think science students should learn X-ray techniques?

It’s one of those tool sets that’s very important for geological, biological and environmental sciences, because you can find a lot of information that you can’t get with other techniques.

You can look at the precise chemistry of samples on really small scales, all the way up to large-scale systems. So X-ray science can be useful to a lot of researchers, and they don’t always get a chance to learn how to actually do it.

Q: How did you become interested in synchrotron research?

During my PhD studies, I was working on an environmental science project that looked at contaminants in the sediments of a lake with a zinc smelter at the edge.

My advisor had never done any research at synchrotrons, but he thought if someone was motivated and wanted to learn about X-rays, it would be a good way to answer some of the questions we had about the different types of metals present in the sediments.

It was really fun to work with a big accelerator at the Advanced Photon Source (APS) at DOE’s Argonne National Laboratory.


ANL/APS

So when I was done with the project, I thought it’d be great to do some more of the same type of research.

Q: Tell me more about the course you co-taught at Caltech.

It’s a 5-week intensive course where the students do a few weeks of field work and collect different types of samples including rock, sediment and DNA. They also analyze those samples in the lab. The goal of the course is to learn how to look at the relationships between geology and what’s living on Earth.

We’ve taught a variety of techniques, such as taking thin slices of rock samples, extracting DNA and lipids, and doing electron microscopy. This year we thought it would be cool to add synchrotron X-ray methods, because that might not be something a student would be exposed to in a typical geobiology course.

There were about 20 students taking the course this past year. Because it was too difficult to get all the students up to Northern California from the Los Angeles area, we decided to operate the synchrotron remotely from Southern California.

Q: How did that work, exactly?

I went down to Santa Catalina Island, where part of the course takes place at the University of Southern California’s Wrigley Marine Science Center. While I was there, I could run the SSRL beamline from my computer in a lecture hall setting. We had a postdoctoral researcher at SSRL helping us actually put the samples in front of the beam, so we could analyze the students’ samples remotely.

The students did some preliminary work in advance to figure out what they wanted to know, and we would discuss what we might be able to get with the technique. We then looked at the results together as they came out in real time from the beamline. It was a lot like doing three days of actual beam time; we just weren’t at SSRL. Many of the samples came from areas of interest in California – such as Mono Lake and the Monterey Formation. We used the X-rays to study the relationships between microbiology and the rock record, both in terms of current processes and those that may have happened millions of years ago.

Q: When did you start using X-rays for geobiology research?

Woody Fischer – a geobiology professor at Caltech – had called me out of the blue. Someone had suggested that he contact me if he was interested in examining manganese in rocks. Over the phone, we talked about X-ray techniques and what we could do with them, and then I invited him to come up for some of my beam time during the following week. It all worked really well, and we wrote up a proposal for some additional time at SSRL, and we’ve been working together ever since.

We started with the chemistry of manganese in rocks that are 2.5 billion years old. This is around the time that oxygen started building up in Earth’s atmosphere, produced by ancient bacteria that used manganese-containing enzymes for photosynthesis. The manganese records in these rocks helped us hypothesize that there may have been cyanobacteria that could do photosynthesis linked to the manganese cycle before they evolved the ability to evolve oxygen. We’ve also started looking at iron-sulfur cycles within early Earth. And we’re continuing to look at manganese in meteorites, as well as samples from Earth in the form of desert varnish – a dark coating of minerals and elements that can form on rocks found in extremely dry climates. So we’re focusing on geobiology in both modern and ancient systems, here on Earth and in extraterrestrial environments.

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Usha Lingappa, Caltech graduate student (left) Sam Webb, SLAC staff scientist (center), and Woody Fischer, geobiology professor at Caltech (right) working together on an experiment at the Stanford Synchrotron Radiation Lightsource. (Chris Smith/SLAC National Accelerator Laboratory)

Q: What are some of the challenges with investigating these types of samples?

Some of these rocks are more than 2 billion years old, so a lot can happen in that time. It takes quite a bit of careful work to look at the relationships within the rock on a microscale. We want to understand how it might have changed and when, to avoid the pitfalls of making conclusions based on something that happened at a different time in a rock’s history.

Q: Do you often run the beamlines from a remote location?

Not usually, because it’s helpful to be able to see what you’re working on. But this sort of remote access allows us to support and troubleshoot four beamlines with our limited staff of two or three people.

This is the first time we’ve used remote access in a course setting. It was a lot of fun and the students seemed excited to find ways to apply the newly learned technique to their research.

Some of the results are really interesting, and we’ll try to publish those findings. So there’s some real science that will come out of the project, as well.

SSRL and APS are DOE Office of Science user facilities.

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

See the full article here .

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From SLAC: “Scientists Watch ‘Artificial Atoms’ Assemble into Perfect Lattices with Many Uses”


SLAC Lab

July 31, 2017
Written by Glennda Chui

Press Office Contact:
Andrew Gordon
agordon@slac.stanford.edu
(650) 926-2282

1
An illustration shows nanocrystals assembling into an ordered ‘superlattice’ – a process that a SLAC/Stanford team was able to observe in real time with X-rays from the Stanford Synchrotron Radiation Lightsource (SSRL). They discovered that this assembly takes just a few seconds when carried out in hot solutions. The results open the door for rapid self-assembly of nanocrystal building blocks into complex structures with applications in optoelectronics, solar cells, catalysis and magnetic materials. (Greg Stewart/SLAC National Accelerator Laboratory.)

SLAC/SSRL

Some of the world’s tiniest crystals are known as “artificial atoms” because they can organize themselves into structures that look like molecules, including “superlattices” that are potential building blocks for novel materials.

Now scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have made the first observation of these nanocrystals rapidly forming superlattices while they are themselves still growing. What they learn will help scientists fine-tune the assembly process and adapt it to make new types of materials for things like magnetic storage, solar cells, optoelectronics and catalysts that speed chemical reactions.

The key to making it work was the serendipitous discovery that superlattices can form superfast – in seconds rather than the usual hours or days – during the routine synthesis of nanocrystals. The scientists used a powerful beam of X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) to observe the growth of nanocrystals and the rapid formation of superlattices in real time.

A paper describing the research, which was done in collaboration with scientists at the DOE’s Argonne National Laboratory, was published today in Nature.

2
A lab in the Stanford Chemical Engineering Department where nanocrystals are grown. Experiments at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) were able to observe the simultaneous growth of nanocrystals and superlattices for the first time. (Dawn Harmer/SLAC National Accelerator Laboratory.)

“The idea is to see if we can get an independent understanding of how these superlattices grow so we can make them more uniform and control their properties,” said Chris Tassone, a staff scientist at SSRL who led the study with Matteo Cargnello, assistant professor of chemical engineering at Stanford.

Tiny Crystals with Outsized Properties

Scientists have been making nanocrystals in the lab since the 1980s. Because of their tiny size –they’re billionths of a meter wide and contain just 100 to 10,000 atoms apiece — they are governed by the laws of quantum mechanics, and this gives them interesting properties that can be changed by varying their size, shape and composition. For instance, spherical nanocrystals known as quantum dots, which are made of semiconducting materials, glow in colors that depend on their size; they are used in biological imaging and most recently in high-definition TV displays.

In the early 1990s, researchers started using nanocrystals to build superlattices, which have the ordered structure of regular crystals, but with small particles in place of individual atoms. These, too, are expected to have unusual properties that are more than the sum of their parts.

But until now, superlattices have been grown slowly at low temperatures, sometimes in a matter of days.

That changed in February 2016, when Stanford postdoctoral researcher Liheng Wu serendipitously discovered that the process can occur much faster than scientists had thought.

3
The experimental set-up at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) where scientists used an X-ray beam to observe superlattices forming during the synthesis of nanocrystals for the first time. The vessel where the reactions took place is at bottom center, wrapped in gold heating tape that boosted the temperature inside to more than 230 degrees Celsius. (Liheng Wu/Stanford University.)

‘Something Weird Is Happening’

He was trying to make nanocrystals of palladium – a silvery metal that’s used to promote chemical reactions in catalytic converters and many industrial processes – by heating a solution containing palladium atoms to more than 230 degrees Celsius. The goal was to understand how these tiny particles form, so their size and other properties could be more easily adjusted.

The team added small windows to a reaction chamber about the size of a tangerine so they could shine an SSRL X-ray beam through it and watch what was happening in real time.

“It’s kind of like cooking,” Cargnello explained. “The reaction chamber is like a pan. We add a solvent, which is like the frying oil; the main ingredients for the nanocrystals, such as palladium; and condiments, which in this case are surfactant compounds that tune the reaction conditions so you can control the size and composition of the particles. Once you add everything to the pan, you heat it up and fry your stuff.”

Wu and Stanford graduate student Joshua Willis expected to see the characteristic pattern made by X-rays scattering off the tiny particles. They saw a completely different pattern instead.

“So something weird is happening,” they texted their adviser.

The something weird was that the palladium nanocrystals were assembling into superlattices.

4
Members of the nanocrystal research team, from left: Assistant Professor Jian Qin, postdoctoral researcher Liheng Wu and Assistant Professor Matteo Cargnello, all of Stanford; SLAC staff scientist Chris Tassone; and Stanford graduate student Joshua Willis. (Dawn Harmer/SLAC National Accelerator Laboratory)

A Balance of Forces

At this point, “The challenge was to understand what brings the particles together and attracts them to each other but not too strongly, so they have room to wiggle around and settle into an ordered position,” said Jian Qin, an assistant professor of chemical engineering at Stanford who performed theoretical calculations to better understand the self-assembly process.

Once the nanocrystals form, what seems to be happening is that they acquire a sort of hairy coating of surfactant molecules. The nanocrystals glom together, attracted by weak forces between their cores, and then a finely tuned balance of attractive and repulsive forces between the dangling surfactant molecules holds them in just the right configuration for the superlattice to grow.

To the scientists’ surprise, the individual nanocrystals then kept on growing, along with the superlattices, until all the chemical ingredients in the solution were used up, and this unexpected added growth made the material swell. The researchers said they think this occurs in a wide range of nanocrystal systems, but had never been seen because there was no way to observe it in real time before the team’s experiments at SSRL.

“Once we understood this system, we realized this process may be more general than we initially thought,” Wu said. “We have demonstrated that it’s not only limited to metals, but it can also be extended to semiconducting materials and very likely to a much larger set of materials.”

The team has been doing follow-up experiments to find out more about how the superlattices grow and how they can tweak the size, composition and properties of the finished product.

Ian Salmon McKay, a graduate student in chemical engineering at Stanford, and Benjamin T. Diroll, a postdoctoral researcher at Argonne National Laboratory’s Center for Nanoscale Materials (CNM), also contributed to the work.

SSRL and CNM are DOE Office of Science User Facilities. The research was funded by the DOE Office of Science and by a Laboratory Directed Research and Development grant from SLAC.

See the full article here .

Please help promote STEM in your local schools.

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