From Symmetry: “How to break a theory”

From Symmetry

DOE’s Fermi National Accelerator Laboratory(US) Wilson Hall.

DOE’s SLAC National Accelerator Laboratory campus with world’s first x-ray laser- the Linac Coherent Light Source (LCLS) unveiled in 2009.

03/08/22
Sarah Charley

When a theory breaks, you learn how to build it better.

In 1859, a French astronomer noticed that gradual changes to Mercury’s orbit could not be explained by Isaac Newton’s concept of gravity.

“Mercury is within the solar system, where Newton’s laws had worked perfectly, and continue to work perfectly, in almost all cases,” says Sophie Renner, a fellow in the CERN Theory Group. “But for some reason, they saw a discrepancy.”

Astronomers attributed the observation to a missing variable, such as an unseen planet slowly tugging Mercury off course. But Mercury’s mysterious playmate was never found.

That’s because their equations didn’t need a new variable; their theory needed a revolution.

Half a century later, scientists found the explanation for Mercury’s behavior: The sun was stretching spacetime and creating a gravity well that slowly changed Mercury’s path. This revelation brought to light the limits of Newtonian physics—and validated Albert Einstein’s theory of general relativity.

These fractures between prediction and observation are what physicists look for.

“We want to break theories for the same reason you want to break software,” says Cynthia Keeler, an assistant professor at Arizona State University. “You have to stress-test it and find out what its boundaries are. When a theory breaks, you learn how to build it better.”

When the CMS and ATLAS experiments at CERN saw an unexpected bump in their data in 2016, theorists submitted nearly 500 papers speculating about what new physics it might reveal. (When the experiments collected more data, the bump disappeared.)

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] Compact Muon Solenoid Detector.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] ATLAS another view Image Claudia Marcelloni ATLAS CERN.

But rigorous experimental testing is only one of the many ways to break a theory. Physicists constantly run quality-control checks designed to crack, bend and extend their favorite mathematical models of the universe.

Ask weird questions

Einstein had a wild imagination. He asked himself questions like: What would he feel if he rode an elevator through outer space? What would he see if he chased a beam of light?

Other daydreamers might not have moved beyond wondering. But Einstein had a background in physics and friends with advanced degrees in mathematics. His thought experiments seeded deeper investigations that eventually showed the limitations of Newtonian mechanics.

“What Einstein did was expose internal paradoxes of the theory itself,” says Stephon Alexander, a physics professor at Brown University. “It’s like looking at a picture of something beautiful, but then finding a new angle and the picture isn’t as beautiful or elegant as you thought.”

Theorists must look for every possible angle, Alexander says. “As a theorist, you have the responsibility to strive for mastery and at the same time, be willing to look at things from the outside-in.”

Today’s thought experiments sound just as bizarre as Einstein’s from 100 years ago. The internal paradoxes they reveal are just as gnarly.

For example: “If I build a black hole out of a bunch of dictionaries, can I find the information in those dictionaries?” Keeler says. “Quantum mechanics says the information should be preserved—maybe it’s hard to get because it’s all mixed up, but it shouldn’t go away.

“Black holes seem to contradict that. We’ve had 50 years of discussions over this problem.”

Check the math

Theories tell stories. What are the smallest pieces of matter? What are their characteristics? What are their relationships? What is their destiny?

But unlike the stories of Shakespeare or Kurosawa, a physics theory is told in the language of mathematics. If the math doesn’t check out, neither does the theory.

“A lot if it is asking, ‘Is this legal?’” Keeler says. “You might write down something that seems mathematically consistent and then run into problems later. You have to ask, could any universe be constructed with this, or would it fall apart?”

Quantum field theory, which describes physics at subatomic scales, makes many mathematicians cringe because of its “algebraic shenanigans,” says Dorota Grabowska, a fellow in the CERN Theory Group. “If I had a conversation with a mathematician about quantum field theory, they would start crying. It’s like when your mom tells you to clean your room, so you shove everything in the closet. It looks fine, but please don’t open the closet.”

Quantum field theory is rife with something mathematicians can’t stand: unresolved infinities. In a 1977 essay, Nobel Laureate Steven Weinberg [The University of Texas-Austin (US)] wrote that “[Quantum field theory’s] reputation among physicists suffered frequent fluctuations… at times dropping so low that quantum field theory came close to be[ing] abandoned altogether.”

But quantum field theory survives because at the end of the day, it still makes predictions that check out with experiments, such as those at the Large Hadron Collider at CERN.

“The LHC is like our mother, and when she opens the closet, everything is magically organized,” Grabowska says.

Push it to extremes

Physics before the 20th century was mostly limited to the study of speeds, sizes and energies around the human scale. But then scientists started asking, what happens if we go faster? Or smaller? Or to a higher energy?

“A theory breaks when you try to calculate something new with the theory you have, and it gives you something absurd,” Renner says. “That’s what happened with the ultraviolet catastrophe of black-body radiation.”

Any blacksmith can attest that there is a link between the temperature of molten iron and the color and brightness of the light it emits. Classical physics did a pretty good job predicting the intensity of this light (hotter objects glow more brightly).

The trouble started when they pushed into the ultraviolet range.

Scientists calculated the amount of ultraviolet radiation an object burning at high temperature would emit. They found the prediction from classical physics in no way reflected reality, Renner says. “It went towards infinity at high frequencies, which is not what we see at all.”

The newly exposed edges of classical physics inspired Max Planck to reinterpret what energy actually is.

Planck proposed that unlike speed—which can be any value up to the speed of light—energy is more like a currency that comes in discrete bills called quanta. High-frequency light costs big quanta to shine, which explained the steep drop-off in the intensity of light radiating from an object in the ultraviolet range.

Today scientists are pushing far beyond the ultraviolet. UV light has around 3 to 30 electronvolts of energy; scientists at the Large Hadron Collider are currently studying the laws of physics at up to 13 trillion electronvolts.

The LHC’s enormous energy allowed physicists to finally find the legendary Higgs boson, which was theorized 50 years before its discovery and helps explain the origin of mass.

But this discovery illuminated what might be the limits of current theory in the form of the Standard Model, which physicists use to describe subatomic particles, forces and fields.

“If the Standard Model is valid across a large range of energies, we would expect the Higgs to have a much heavier mass than it does,” Renner says. “There’s no reason why the Higgs should be at the mass that it is, unless some new theory takes over at energies just out of our reach.”

Physicists are pushing the limits and searching for cracks that will let them see beyond the boundaries of the Standard Model’s effectiveness. Theory alone can go only so far, and many theorists are looking to experimentalists to light the way.

“Theoretical physics has always been driven by observations and detection,” Alexander says. “The field would be nothing without it. We’re relying on experimentalists to break the theory, and we’re really interested to see how they will surprise us.”

See the full article here .

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Symmetry is a joint Fermilab/SLAC publication.

From Lawrence Livermore National Laboratory: “World’s largest optical lens shipped to SLAC”

From Lawrence Livermore National Laboratory

Sept. 12, 2019

Stephen Wampler
wampler1@llnl.gov
925-423-3107

LLNL engineer Vincent Riot (left), who has worked on the Large Synoptic Survey Telescope (LSST) for more than a decade and has been the full camera project manager since 2017, and LLNL optical engineer Justin Wolfe, the LSST camera optics subsystems manager, stand in front of the LSST main lens assembly. Photo by Farrin Abbott/SLAC National Accelerator Laboratory.

When the world’s newest telescope starts imaging the southern sky in 2023, it will take photos using optical assemblies designed by Lawrence Livermore National Laboratory (LLNL) researchers and built by Lab industrial partners.

A key feature of the camera’s optical assemblies for the Large Synoptic Survey Telescope (LSST), under construction in northern Chile, will be its three lenses, one of which at 1.57 meters (5.1 feet) in diameter is believed to be the world’s largest high-performance optical lens ever fabricated.

The lens assembly, which includes the lens dubbed L-1, and its smaller companion lens (L-2), at 1.2 meters in diameter, was built over the past five years by Boulder, Colorado-based Ball Aerospace and its subcontractor, Tucson-based Arizona Optical Systems.

Mounted together in a carbon fiber structure, the two lenses were shipped from Tucson, arriving intact after a 17-hour truck journey at the SLAC National Accelerator Laboratory in Menlo Park.

SLAC is managing the overall design and fabrication, as well as the subcomponent integration and final assembly of LSST’s $168 million, 3,200-megapixel digital camera, which is more than 90 percent complete and due to be finished by early 2021. In addition to SLAC and LLNL, the team building the camera includes an international collaboration of universities and labs, including the Paris-based Centre National de la Recherche Scientifique and Brookhaven National Laboratory.

LSST the Vera C. Rubin Observatory

LSST Camera, built at SLAC

LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

“The success of the fabrication of this unique optical assembly is a testament to LLNL’s world-leading expertise in large optics, built on decades of experience in the construction of the world’s largest and most powerful laser systems,” said physicist Scot Olivier, who helped manage Livermore’s involvement in the LSST project for more than a decade.

Olivier said without the dedicated and exceptional work of LLNL optical scientists Lynn Seppala and Brian Bauman and LLNL engineers Vincent Riot, Scott Winters and Justin Wolfe, spanning a period of nearly two decades, the LSST camera optics, including the world’s largest lens, would not be the reality they are today.

“Riot’s contributions to LSST also go far beyond the camera optics — as the current overall project manager for the LSST camera, Riot is a principal figure in the successful development of this major scientific instrument that is poised to revolutionize the field of astronomy,” Olivier added.

LSST Director Steven Kahn, a physicist at Stanford University and SLAC, noted that “Livermore has played a very significant technical role in the camera and a historically important role in the telescope design.”

Livermore’s researchers made essential contributions to the optical design of LSST’s lenses and mirrors, the way LSST will survey the sky, how it compensates for atmospheric turbulence and gravity, and more.

LLNL personnel led the procurement and delivery of the camera’s optical assemblies, which include the three lenses (the third lens, at 72 centimeters in diameter, will be delivered to SLAC within a month) and a set of filters covering six wavelength-bands, all in their final mechanical mount.

Livermore focused on the design and then delegated fabrication to industry vendors, although the filters will be placed into the interface mounts at the Lab before being shipped to SLAC for final integration into the camera.

The 8.4-meter LSST will take digital images of the entire visible southern sky every few nights, revealing unprecedented details of the universe and helping unravel some of its greatest mysteries. During a 10-year time frame, LSST will detect about 20 billion galaxies — the first time a telescope will observe more galaxies than there are people on Earth – and will create a time-lapse “movie” of the sky.

This data will help researchers better understand dark matter and dark energy, which together make up 95 percent of the universe, but whose makeup remains unknown, as well as study the formation of galaxies, track potentially hazardous asteroids and observe exploding stars.

The telescope’s camera — the size of a small car and weighing more than three tons — will capture full-sky images at such high resolution that it would take 1,500 high-definition television screens to display just one picture.

Research scientists aren’t the only ones who will have access to the LSST data. Anyone with a computer will be able to fly through the universe, past objects 100 million times fainter than can be observed with the unaided eye. The LSST project will provide an engagement platform to enable both students and the public to participate in the process of scientific discovery.

Riot, who started on the LSST project in 2008, initially managed the camera optics fabrication planning, became the LSST deputy camera manager in 2013 and the full camera project manager in 2017. For the past three years, he has worked at LLNL and at SLAC on special assignment.

“There are important challenges getting everything together for the LSST camera. We’re receiving all of these expensive parts that people have been working on for years and they all have to fit together,” Riot said.

Wolfe, an LLNL optical engineer and the LSST camera optics subsystems manager, and Riot are pleased that the world’s largest optical lens has overcome hurdles.

“Any time you undertake an activity for the first time, there are bound to be challenges, and production of the LSST L-1 lens proved to be no different,” Wolfe said. “Every stage was crucial and carried great risk. You are working with a piece of glass more than five feet in diameter and only four inches thick. Any mishandling, shock or accident can result in damage to the lens. The lens is a work of craftsmanship and we are all rightly proud of it.

“When I joined LLNL I had no idea that it would lead to the opportunity to deliver first-of-a-kind optics to a first-of-a-kind telescope,” Wolfe said. “From production of the largest precision lens known, to coating of the largest precision bandpass filters, the LSST optics have set a new standard.”

Livermore involvement in LSST started around 2001, spurred by the scientific interest of LLNL astrophysicist Kem Cook, a member of the Lab team that previously led the search for galactic dark matter in the form of Massive Compact Halo Objects.

However, LLNL participation in LSST quickly became centered on the Lab’s expertise in large optics, built over decades of developing the world’s largest laser systems. Starting in 2002, LLNL optical scientist Seppala, who helped design the National Ignition Facility, made a series of improvements to the optical design of LSST leading to the 2005 baseline design. This consisted of three mirrors, the two largest in the same plane so they could be fabricated from the same piece of glass, and three large lenses, as well as a set of six filters that define the color of the images recorded by the 3.2-gigapixel camera detector.

Construction on LSST started in 2014 on El Peñon, a peak 8,800 feet high along the Cerro Pachón ridge in the Andes Mountains, located 220 miles north of Santiago, Chile.

Financial support for LSST comes from the National Science Foundation (NSF), the U.S. Department of Energy’s Office of Science, and private funding raised by the LSST Corporation. The NSF-funded LSST Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy. The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory.

The camera system for LSST, including the three lenses and six filters designed by LLNL researchers and built by Lab industrial partners, will be shipped from SLAC to the telescope site in Chile in early 2021

See the full article here .

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Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security Administration
Lawrence Livermore National Laboratory (LLNL) is an American federal research facility in Livermore, California, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center (FFRDC), it is primarily funded by the U.S. Department of Energy (DOE) and managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it.
LLNL is self-described as “a premier research and development institution for science and technology applied to national security.” Its principal responsibility is ensuring the safety, security and reliability of the nation’s nuclear weapons through the application of advanced science, engineering and technology. The Laboratory also applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.

The Laboratory is located on a one-square-mile (2.6 km2) site at the eastern edge of Livermore. It also operates a 7,000 acres (28 km2) remote experimental test site, called Site 300, situated about 15 miles (24 km) southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of roughly 5,800 employees.

LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley. It was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence,[2] director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility.

The new laboratory was sited at a former naval air station of World War II. It was already home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions (i.e. fusion). About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus.

Lawrence tapped 32-year-old Herbert York, a former graduate student of his, to run Livermore. Under York, the Lab had four main programs: Project Sherwood (the magnetic-fusion program), Project Whitney (the weapons-design program), diagnostic weapon experiments (both for the Los Alamos and Livermore laboratories), and a basic physics program. York and the new lab embraced the Lawrence “big science” approach, tackling challenging projects with physicists, chemists, engineers, and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university’s board of regents named both laboratories for him, as the Lawrence Radiation Laboratory.

Historically, the Berkeley and Livermore laboratories have had very close relationships on research projects, business operations, and staff. The Livermore Lab was established initially as a branch of the Berkeley laboratory. The Livermore lab was not officially severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, and LLNL’s remote test location as Site 300.[3]

The laboratory was renamed Lawrence Livermore Laboratory (LLL) in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had exclusively managed and operated the Laboratory since its inception 55 years before. The laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008.[4] The jury found that LLNS breached a contractual obligation to terminate the employees only for “reasonable cause.”[5] The five plaintiffs also have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial.[6] There are 125 co-plaintiffs awaiting trial on similar claims against LLNS.[7] The May 2008 layoff was the first layoff at the laboratory in nearly 40 years.[6]

On March 14, 2011, the City of Livermore officially expanded the city’s boundaries to annex LLNL and move it within the city limits. The unanimous vote by the Livermore city council expanded Livermore’s southeastern boundaries to cover 15 land parcels covering 1,057 acres (4.28 km2) that comprise the LLNL site. The site was formerly an unincorporated area of Alameda County. The LLNL campus continues to be owned by the federal government.

LLNL/NIF

From SLAC: “A miniature camera for the Large Synoptic Survey Telescope will help test the observatory and take first images”

June 19, 2019
By Aiko Takeuchi-Demirci

SLAC completed its work on ComCam, a commissioning device to be installed in Chile later this year.

LSST ComCam

Scientists at the Department of Energy’s SLAC National Accelerator Laboratory are building the world’s largest digital camera for astronomy and astrophysics – a minivan-sized 3,200-megapixel ‘eye’ of the future Large Synoptic Survey Telescope (LSST) that will enable unprecedented views of the universe starting in the fall of 2022 and provide new insights into dark energy and other cosmic mysteries.

LSST Camera, being built at SLAC

In the meantime, the lab has completed its work on a miniature version that will soon be used for testing the telescope and taking LSST’s first images of the night sky.

These images will include glimpses of the motions of asteroids and objects in our solar system with orbits beyond that of Neptune, as well as alerts of sudden events such as supernovae, exploding stars that temporarily light up parts of the sky.

ComCam, a commissioning camera for LSST. (Farrin Abbott/SLAC National Accelerator Laboratory)

The device, called ComCam (short for Commissioning Camera), will use only four percent of the full LSST camera’s focal plane and produce much smaller images, but it will provide enough “imaging power” to test the observatory while its ultimate camera is still under construction. In fact, ComCam’s 144 megapixels outnumber the pixel count that was available to the Sloan Digital Sky Survey, a pioneering astrophysical survey project in the early 2000s.

“ComCam will give us a great head start in checking all of the interfaces between the camera, telescope, site infrastructure and data management,” says Kevin Reil, LSST commissioning scientist and SLAC staff scientist.

After completing the integration of imaging sensors into ComCam and other tasks, the SLAC team today shipped the device to LSST headquarters in Tucson, Arizona. There, more components will be added before the finished ComCam is sent to its final destination in Chile later this year.

A miniature LSST camera

The extraordinarily high image quality of the full LSST camera will be largely due to its 189 state-of-the-art imaging sensors. Arranged into square arrays, called rafts, of nine sensors each, they’ll make up the camera’s focal plane. ComCam has only a single raft, which was provided by DOE’s Brookhaven National Laboratory and recently inserted into the ComCam cryostat at SLAC.

The cryostat, specially designed and built for ComCam, holds the raft in place and cools its imaging sensors to very low temperatures to eliminate unwanted background signals and improve image quality. The ComCam cryostat uses a different refrigeration system from that of the final LSST camera, which requires a more complex system in order to handle 21 rafts.

The raft also contains electronics boards that will digitize data taken with ComCam. These data will be sent to data management systems at the National Science Foundation-supported National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign and centers at France’s National Institute of Nuclear and Particle Physics and in Chile, where they will be analyzed by scientists around the world.

SLAC is also building and testing the camera control system, which will allow the observatory software to send commands to ComCam, for instance, to change filters and take images. The LSST camera will use the same control system.

Toward first images

Once ComCam arrives in Tucson, LSST scientists will add lenses, a filter changer and a shutter. They will integrate the complete instrument with the observatory software and computing infrastructure and perform crucial tests, including a dry run that will simulate a night of observations.

“In large projects like LSST, it’s exciting to watch the hardware and software come together into a working system over the years,” says Brian Stalder, LSST commissioning scientist in Tucson.

Finally, ComCam will be sent to Chile and installed on the actual telescope, paving the way for LSST commissioning.

In addition, it’ll produce LSST’s first images, albeit at a much smaller scale than the final camera. Although science studies won’t be ComCam’s primary purpose, the team expects the camera to produce images of very good quality, Reil says: “It’ll be exciting to see these early images taken with our brand new, world-class telescope.”

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.

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.

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).

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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Please help promote STEM in your local schools.

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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.

From SLAC National Accelerator Lab: “Study shows single atoms can make more efficient catalysts”

From SLAC National Accelerator Lab

January 7, 2019
Glennda Chui

Scientists used a combination of four techniques, represented here by four incoming beams, to reveal in unprecedented detail how a single atom of iridium catalyzes a chemical reaction. (Greg Stewart/SLAC National Accelerator Laboratory)

Detailed observations of iridium atoms at work could help make catalysts that drive chemical reactions smaller, cheaper and more efficient.

Catalysts are chemical matchmakers: They bring other chemicals close together, increasing the chance that they’ll react with each other and produce something people want, like fuel or fertilizer.

Since some of the best catalyst materials are also quite expensive, like the platinum in a car’s catalytic converter, scientists have been looking for ways to shrink the amount they have to use.

Now scientists have their first direct, detailed look at how a single atom catalyzes a chemical reaction. The reaction is the same one that strips poisonous carbon monoxide out of car exhaust, and individual atoms of iridium did the job up to 25 times more efficiently than the iridium nanoparticles containing 50 to 100 atoms that are used today.

The research team, led by Ayman M. Karim of Virginia Tech, reported the results in Nature Catalysis.

“These single-atom catalysts are very much a hot topic right now,” said Simon R. Bare, a co-author of the study and distinguished staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory, where key parts of the work took place. “This gives us a new lens to look at reactions through, and new insights into how they work.”

Karim added, “To our knowledge, this is the first paper to identify the chemical environment that makes a single atom catalytically active, directly determine how active it is compared to a nanoparticle, and show that there are very fundamental differences – entirely different mechanisms – in the way they react.”

Is smaller really better?

Catalysts are the backbone of the chemical industry and essential to oil refining, where they help break crude oil into gasoline and other products. Today’s catalysts often come in the form of nanoparticles attached to a surface that’s porous like a sponge – so full of tiny holes that a single gram of it, unfolded, might cover a basketball court. This creates an enormous area where millions of reactions can take place at once. When gas or liquid flows over and through the spongy surface, chemicals attach to the nanoparticles, react with each other and float away. Each catalyst is designed to promote one specific reaction over and over again.

But catalytic reactions take place only on the surfaces of nanoparticles, Bare said, “and even though they are very small particles, the expensive metal on the inside of the nanoparticle is wasted.”

Individual atoms, on the other hand, could offer the ultimate in efficiency. Each and every atom could act as a catalyst, grabbing chemical reactants and holding them close together until they bond. You could fit a lot more of them in a given space, and not a speck of precious metal would go to waste.

Single atoms have another advantage: Unlike clusters of atoms, which are bound to each other, single atoms are attached only to the surface, so they have more potential binding sites available to perform chemical tricks – which in this case came in very handy.

Research on single-atom catalysts has exploded over the past few years, Karim said, but until now no one has been able to study how they function in enough detail to see all the fleeting intermediate steps along the way.

Grabbing some help

To get more information, the team looked at a simple reaction where single atoms of iridium split oxygen molecules in two, and the oxygen atoms then react with carbon monoxide to create carbon dioxide.

They used four approaches­ – infrared spectroscopy, electron microscopy, theoretical calculations and X-ray spectroscopy with beams from SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) – to attack the problem from different angles, and this was crucial for getting a complete picture.

SLAC/SSRL

SLAC SSRL Campus

“It’s never just one thing that gives you the full answer,” Bare said. “It’s always multiple pieces of the jigsaw puzzle coming together.”

The team discovered that each iridium atom does, in fact, perform a chemical trick that enhances its performance. It grabs a single carbon monoxide molecule out of the passing flow of gas and holds onto it, like a person tucking a package under their arm. The formation of this bond triggers tiny shifts in the configuration of the iridium atom’s electrons that help it split oxygen, so it can react with the remaining carbon monoxide gas and convert it to carbon dioxide much more efficiently.

More questions lie ahead: Will this same mechanism work in other catalytic reactions, allowing them to run more efficiently or at lower temperatures? How do the nature of the single-atom catalyst and the surface it sits on affect its binding with carbon monoxide and the way the reaction proceeds?

The team plans to return to SSRL in January to continue the work.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

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

From SLAC: “SLAC Produces First Electron Beam with Superconducting Electron Gun”

SLAC Lab

Image of the first electron beam (bright colors) produced with a superconducting electron gun at SLAC and analyzed with an energy spectrometer. The beam energy was more than a million electronvolts. (SLAC National Accelerator Laboratory)

April 9, 2018
Manuel Gnida

Making a high-quality beam of high-energy electrons starts with an electron gun: It knocks electrons out of atoms with a laser beam so they can be accelerated to nearly the speed of light for experiments that explore nature’s fastest atomic processes.

Now accelerator scientists at the Department of Energy’s SLAC National Accelerator Laboratory are testing a new type of electron gun for a future generation of instruments that take snapshots of the atomic world in never-before-seen quality and detail, with applications in chemistry, biology, energy and materials science.

Unlike other electron sources at SLAC, the new one is superconducting: When chilled to extremely low temperatures, some of its key components conduct electricity with nearly 100 percent efficiency. This allows it to produce superior, almost continuous electron beams that will be needed for future high-energy X-ray lasers and ultrafast electron microscopes. The new superconducting electron gun recently produced its first beam of electrons at SLAC.

“This is an important milestone,” says Xijie Wang, who leads the project. “The use of superconducting accelerator technology represents the beginning of a new era at the lab that will create unforeseen research opportunities, and will keep us at the forefront of science for decades to come.”

SLAC’s accelerator scientists are testing a superconducting electron gun (inside the large vessel at center), a new type of electron source that could be used in next-generation X-ray lasers and ultrafast electron microscopes. (Dawn Harmer/SLAC National Accelerator Laboratory)

A Superior Electron Source

At SLAC and other labs, beams of high-energy electrons are used as tools to precisely examine the atomic fabric of our world and to look at atomic-scale processes that occur within femtoseconds, or millionths of a billionth of a second. The beams are used directly, in instruments for ultrafast electron diffraction and microscopy (UED/UEM), or indirectly in X-ray lasers like SLAC’s Linac Coherent Light Source (LCLS), where the energy of the electron beam is converted into powerful X-ray light.

SLAC LCLS

In both approaches, the electrons are produced with an electron gun. It consists of a photocathode, where electrons are released when a metal is hit by a laser pulse; a hollow metal cavity, which accelerates the electrons with a radiofrequency field; and a magnetic lens that bundles the electrons into a tight beam.

Conventional electron guns use cavities made of normal-conducting metals like copper. But the new device’s cavity is made of niobium, which becomes superconducting at temperatures close to absolute zero. Several groups around the world are actively pursuing the superconducting technology for next-generation particle accelerators and X-ray lasers.

“Superconducting electron guns have the potential to outperform current guns,” says accelerator physicist Theodore Vecchione, coordinator of the SLAC project. “For instance, while the electron gun that’s being installed as part of the future LCLS-II will generate electron pulses at an extremely high repetition rate, the superconducting gun should be able to produce similar pulses at four times higher beam energy.

SLAC/LCLS II projected view

It should also be able to achieve twice the beam acceleration over a given distance, producing a tighter beam of electrons with extraordinary average brightness.”

SLAC schematic of superconducting electron gun

LCLS-II will already use superconducting cryomodules to bring electrons up to speed, which will allow the X-ray laser to fire 8,000 times faster after the upgrade. A superconducting electron gun could be ready for a future high-energy upgrade that would further enhance its scientific potential.

“In addition to advancing X-ray science, the superconducting technology could also turn into an electron source for the UED/UEM techniques we’re developing,” says SLAC accelerator physicist Renkai Li. “It would further improve the quality of atomic-level images and movies we’re able to capture now.”

A Top R&D Priority

The SLAC team is testing a superconducting gun that was originally built for a project at the University of Wisconsin, Madison. About two years ago, the DOE relocated the gun to SLAC, asking the lab to recommission it for R&D work in the field of future electron sources.

“There is a lot of excitement at the lab and the DOE about the opportunity to develop the superconducting technology into something that will drive future applications that require powerful electron beams,” says Bruce Dunham, associate lab director for SLAC’s Accelerator Directorate. “It’s very exciting to see the new gun produce its first electron beam, as it represents the very first step toward that future.”

Over the past few months, the team installed the gun at SLAC’s Next Linear Collider Test Accelerator (NLCTA) facility and built an experimental setup with diagnostics needed to analyze the generated electron beam. “This successful effort involved many different groups around the lab, including people working on lasers, metrology, vacuum and controls,” says Keith Jobe, the NLCTA facility manager. “We’re also grateful to Bob Legg and other members of the original Wisconsin team, who were very helpful in getting this effort underway here.”

Now that the team has demonstrated the superconducting gun is working and capable of producing electron beams with energies above a million electronvolts, they are planning their next steps. They first want to make a number of upgrades to improve the gun’s performance, including an overhaul of its refrigeration system. Then, they will be ready to push the technology to higher beam energies that could pave the way for future applications.

The project is funded by the DOE Office of Science. LCLS is a DOE Office of Science user facility.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

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

From SLAC: “Weird Superconductor Leads Double Life”

SLAC Lab

March 20, 2018
Glennda Chui

One unusual property of superconducting materials is that they expel magnetic fields and thus cause magnets to levitate, as shown here. A study at SLAC and Stanford of a particularly odd superconductor, strontium titanate, will aid understanding and development of these materials. (ViktorCap/iStock)

Understanding strontium titanate’s odd behavior will aid efforts to develop materials that conduct electricity with 100 percent efficiency at higher temperatures.

Until about 50 years ago, all known superconductors were metals. This made sense, because metals have the largest number of loosely bound “carrier” electrons that are free to pair up and flow as electrical current with no resistance and 100 percent efficiency – the hallmark of superconductivity.

Then an odd one came along – strontium titanate, the first oxide material and first semiconductor found to be superconducting. Even though it doesn’t fit the classic profile of a superconductor – it has very few free-to-roam electrons – it becomes superconducting when conditions are right, although no one could explain why.

Now scientists have probed the superconducting behavior of its electrons in detail for the first time. They discovered it’s even weirder than they thought. Yet that’s good news, they said, because it gives them a new angle for thinking about what’s known as “high temperature” superconductivity, a phenomenon that could be harnessed for a future generation of perfectly efficient power lines, levitating trains and other revolutionary technologies.

The research team, led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, described their study in a paper published Jan. 30 in the Proceedings of the National Academy of Sciences.

“If conventional metal superconductors are at one end of a spectrum, strontium titanate is all the way down at the other end. It has the lowest density of available electrons of any superconductor we know about,” said Adrian Swartz, a postdoctoral researcher at the Stanford Institute for Materials and Energy Science (SIMES) who led the experimental part of the research with Hisashi Inoue, a Stanford graduate student at the time.

“It’s one of a large number of materials we call ‘unconventional’ superconductors because they can’t be explained by current theories,” Swartz said. “By studying its extreme behavior, we hope to gain insight into the ingredients that lead to superconductivity in these unconventional materials, including the ones that operate at higher temperatures.”

Dueling Theories

According to the widely accepted theory known as BCS for the initials of its inventors, conventional superconductivity is triggered by natural vibrations that ripple through a material’s atomic latticework. The vibrations cause carrier electrons to pair up and condense into a superfluid, which flows through the material with no resistance – a 100-percent-efficient electric current. In this picture, the ideal superconducting material contains a high density of fast-moving electrons, and even relatively weak lattice vibrations are enough to glue electron pairs together.

But outside the theory, in the realm of unconventional superconductors, no one knows what glues the electron pairs together, and none of the competing theories hold sway.

To find clues to what’s going on inside strontium titanate, scientists had to figure out how to apply an important tool for studying superconducting behavior, known as tunneling spectroscopy, to this material. That took several years, said Harold Hwang, a professor at SLAC and Stanford and SIMES investigator.

“The desire to do this experiment has been there for decades, but it’s been a technical challenge,” he said. “This is, as far as I know, the first complete set of data coming out of a tunneling experiment on this material.” Among other things, the team was able to observe how the material responded to doping, a commonly used process where electrons are added to a material to improve its electronic performance.

‘Everything is Upside Down’

The tunneling measurements revealed that strontium titanate is the exact opposite of what you’d expect in a superconductor: Its lattice vibrations are strong and its carrier electrons are few and slow.

“This is a system where everything is upside down,” Hwang said.

On the other hand, details like the behavior and density of its electrons and the energy required to form the superconducting state match what you would expect from conventional BCS theory almost exactly, Swartz said.

“Thus, strontium titanate seems to be an unconventional superconductor that acts like a conventional one in some respects,” he said. “This is quite a conundrum, and quite a surprise to us. We discovered something that was more confusing than we originally thought, which from a fundamental physics point of view is more profound.”

He added, “If we can improve our understanding of superconductivity in this puzzling set of circumstances, we could potentially learn how to harvest the ingredients for realizing superconductivity at higher temperatures.”

The next step, Swartz said, is to use tunneling spectroscopy to test a number of theoretical predictions about why strontium titanate acts the way it does.

SIMES is a joint SLAC/Sanford institute. Theorists from SIMES and from the University of Tennessee, Knoxville also contributed to this study, which was funded by the DOE Office of Science and the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

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

From SLAC: “In a First, Tiny Diamond Anvils Trigger Chemical Reactions by Squeezing”

SLAC Lab

February 21, 2018
Glennda Chui

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

Experiments with ‘molecular anvils’ mark an important advance for mechanochemistry, which has the potential to make chemistry greener and more precise.

An illustration shows complexes of soft molecules (yellow and pink) attached to “molecular anvils” (red and blue) that are about to be squeezed between two diamonds in a diamond anvil cell. The molecular anvils distribute this pressure unevenly, breaking bonds and triggering other chemical reactions in the softer molecules. (Peter Allen/UC-Santa Barbara)

A disassembled diamond anvil cell. Each half contains a tiny diamond housed in stainless steel. Samples are placed between the diamond tips; then the cell is closed and the tips squeezed together by tightening screws. This small device can generate pressures in the gigapascal range – 10,000 times the atmospheric pressure at the Earth’s surface. (Dawn Harmer/SLAC National Accelerator Laboratory)

An animation shows how attaching molecular anvils (gray cages) to softer molecules (red and yellow balls) distributes the pressure from a bigger diamond anvil unevenly, so chemical bonds bend and eventually break around the atom that bears the largest deformation (circled red ball). (Greg Stewart/SLAC National Accelerator Laboratory)

Scientists have turned the smallest possible bits of diamond and other super-hard specks into “molecular anvils” that squeeze and twist molecules until chemical bonds break and atoms exchange electrons. These are the first such chemical reactions triggered by mechanical pressure alone, and researchers say the method offers a new way to do chemistry at the molecular level that is greener, more efficient and much more precise.

The research was led by scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, who reported their findings in Nature today.

“Unlike other mechanical techniques, which basically pull molecules until they break apart, we show that pressure from molecular anvils can both break chemical bonds and trigger another type of reaction where electrons move from one atom to another,” said Hao Yan, a physical science research associate at SIMES, the Stanford Institute for Materials and Energy Sciences, and one of the lead authors of the study.

“We can use molecular anvils to trigger changes at a specific point in a molecule while protecting the areas we don’t want to change,” he said, “and this creates a lot of new possibilities.”

A reaction that’s mechanically driven has the potential to produce entirely different products from the same starting ingredients than one driven the conventional way by heat, light or electrical current, said study co-author Nicholas Melosh, a SIMES investigator and associate professor at SLAC and Stanford. It’s also much more energy efficient, and because it doesn’t need heat or solvents, it should be environmentally friendly.

Putting the Squeeze on Materials with Diamonds

The experiments were carried out with a diamond anvil cell about the size of an espresso cup in the laboratory of paper co-author Wendy Mao, an associate professor at SLAC and Stanford and an investigator with SIMES, which is a joint SLAC/Stanford institute.

Diamond anvil cells squeeze materials between the flattened tips of two diamonds and can reach tremendous pressures – over 500 gigapascals, or about one and a half times the pressure at the center of the Earth. They’re used to explore what minerals deep inside the Earth are like and how materials under pressure develop unusual properties, among other things.

These pressures are reached in a surprisingly straightforward way, by tightening screws to bring the diamonds closer together, Mao said. “Pressure is force per unit area, and we are compressing a tiny amount of sample between the tips of two small diamonds that each weigh only about a quarter of a carat,” she said, “so you only need a modest amount of force to reach high pressures.”

Since the diamonds are transparent, light can go through them and reach the sample, said Yu Lin, a SIMES associate staff scientist who led the high-pressure part of the experiment.

“We can use a lot of experimental techniques to study the reaction while the sample is compressed,” she said. “For instance, when we shine an X-ray beam into the sample, the sample responds by scattering or absorbing the light, which travels back through the diamond into a detector. Analyzing the signal from that light tells you if a reaction has occurred.”

Illustration of a diamond anvil cell, where samples can be compressed to very high pressures between the flattened tips of two diamonds. (Argonne National Laboratory, Greg Stewart/SLAC National Accelerator Laboratory)

What usually happens when you squeeze a sample is that it deforms uniformly, with all the bonds between atoms shrinking by the same amount, Melosh said.

Yet this is not always the case, he said: “If you compress a material that has both hard and soft components, such as carbon fibers embedded in epoxy, the bonds in the soft epoxy will deform a whole lot more than the ones in the carbon fiber.”

They wondered if they could harness that same principle to bend or break specific bonds in an individual molecule.

What got them thinking along those lines was a series of experiments Melosh’s team had done with diamondoids, the smallest possible bits of diamond, which are invisible to the naked eye and weigh less than a billionth of a billionth of a carat. Melosh co-directs a joint SLAC-Stanford program that isolates diamondoids from petroleum fluid and looks for ways to put them to use. In a recent study, his team had attached diamondoids to smaller, softer molecules to create Lego-like blocks that assembled themselves into the thinnest possible electrical wires, with a conducting core of sulfur and copper.

Like carbon fibers in epoxy, these building blocks contained hard and soft parts. If put into a diamond anvil, would the hard parts act as mini-anvils that squeeze and deform the soft parts in a non-uniform way?

The answer, they discovered, was yes.

A disassembled diamond anvil cell. Each half contains a tiny diamond housed in stainless steel. Samples are placed between the diamond tips; then the cell is closed and the tips squeezed together by tightening screws. This small device can generate pressures in the gigapascal range – 10,000 times the atmospheric pressure at the Earth’s surface. (Dawn Harmer/SLAC National Accelerator Laboratory)

Tiny Anvils Open New Possibilities

For their first experiments, they used copper sulfur clusters – tiny particles consisting of eight atoms – attached to molecular anvils made of another rigid molecule called carborane. They put this combination into the diamond anvil cell and cranked up the pressure.

When the pressure got high enough, atomic bonds in the cluster broke, but that’s not all. Electrons moved from its sulfur atoms to its copper atoms and pure crystals of copper formed, which would not have occurred in conventional reactions driven by heat, the researchers said. They discovered a point of no return where this change becomes irreversible. Below that pressure point, the cluster goes back to its original state when pressure is removed.

Computational studies revealed what had happened: Pressure from the diamond anvil cell moved the molecular anvils, and they in turn squeezed chemical bonds in the clusters, compressing them at least 10 times more than their own bonds had been compressed. This compression was also uneven, Yan said, and it bent or twisted some of the cluster’s bonds in a way that caused bonds to break, electrons to move and copper crystals to form.

Other experiments, this time with diamondoids as molecular anvils, showed that small changes in the sizes and positions of the tiny anvils can make the difference between triggering a reaction or protecting part of a molecule so it doesn’t bend or react.

The scientists were able to observe these changes with several techniques, including electron microscopy at Stanford and X-ray measurements at two DOE Office of Science user facilities – the Advanced Light Source at Lawrence Berkeley National Laboratory and the Advanced Photon Source at Argonne National Laboratory.

LBNL/ALS

ANL/APS

Researchers in a SIMES lab with equipment used in the molecular anvil study. From left: Hao Yan, a physical science research associate at SIMES; Nicholas Melosh, a SIMES investigator and associate professor at SLAC and Stanford; and Yu Lin, a SIMES associate staff scientist. (Dawn Harmer/SLAC National Accelerator Laboratory)

“This is exciting, and it opens up a whole new field,” Mao said. “From our side, we’re interested in looking at how pressure can affect a wide range of technologically interesting materials, from superconductors that transmit electricity with no loss to halide perovskites, which have a lot of potential for next-generation solar cells. Once we understand what’s possible from a very basic science point of view we can think about the more practical side.”

Going forward, the researchers also want to use this technique to look at reactions that are hard to do in conventional ways and see if compression makes them easier, Yan said.

“If we want to dream big, could compression help us turn carbon dioxide from the air into fuel, or nitrogen from the air into fertilizer?” he said. “These are some of the questions that molecular anvils will allow people to explore.”

In addition to SLAC, Stanford, Berkeley Lab and Argonne, researchers who contributed to this study came from the National Autonomous University of Mexico (UNAM), Justus-Liebig University in Germany, Hong Kong University of Science and Technology and the University of Chicago. Major funding came from the DOE Office of Science.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

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

From SLAC: “Q&A: Alan Heirich and Elliott Slaughter Take On SLAC’s Big Data Challenges”

SLAC Lab

January 9, 2018
Manuel Gnida

Members of SLAC’s Computer Science Division. From left: Alex Aiken, Elliott Slaughter and Alan Heirich. (Dawn Harmer/SLAC National Accelerator Laboratory)

As the Department of Energy’s SLAC National Accelerator Laboratory builds the next generation of powerful instruments for groundbreaking research in X-ray science, astronomy and other fields, its Computer Science Division is preparing for the onslaught of data these instruments will produce.

The division’s initial focus is on LCLS-II, an upgrade to the Linac Coherent Light Source (LCLS) X-ray laser that will fire 8,000 times faster than the current version. LCLS-II promises to provide completely new views of the atomic world and its fundamental processes. However, the jump in firing rate goes hand and in hand with an explosion of scientific data that would overwhelm today’s computing architectures.

SLAC/LCLS

SLAC/LCLS II projected view

In this Q&A, SLAC computer scientists Alan Heirich and Elliott Slaughter talk about their efforts to develop new computing capabilities that will help the lab cope with the coming data challenges.

Heirich, who joined the lab last April, earned a PhD from the California Institute of Technology and has many years of experience working in industry and academia. Slaughter joined last June; he’s a recent PhD graduate from Stanford University, where he worked under the guidance of Alex Aiken, professor of computer science at Stanford and director of SLAC’s Computer Science Division.

What are the computing challenges you’re trying to solve?

Heirich: The major challenge we’re looking at now is that LCLS-II will produce so much more data than the current X-ray laser. Data rates will increase 10,000 times, from about 100 megabytes per second today to a terabyte per second in a few years. We need to think about the computing tools and infrastructure necessary to take control over that enormous future data stream.

Slaughter: Our development of new computing architectures is aimed at analyzing LCLS-II data on the fly, providing initial results within a minute or two. This allows researchers to evaluate the quality of their data quickly, make adjustments and collect data in the most efficient way. However, real-time data analysis is quite challenging if you collect data with an X-ray laser that fires a million pulses per second.
How can real-time analysis be achieved?

Slaughter: We won’t be able to do all this with just the computing capabilities we have on site. The plan is to send some of the most challenging LCLS-II data analyses to the National Energy Research Scientific Computing Center (NERSC) at DOE’s Lawrence Berkeley National Laboratory, where extremely fast supercomputers will analyze the data and send the results back to us within minutes.

Our team has joined forces with Amedeo Perazzo, who leads the LCLS Controls and Data Systems Division, to develop the system that will run the analysis. Scientists doing experiments at LCLS will be able to define the details of that analysis, depending on what their scientific questions are.

Our goal is to be able to do the analysis in a very flexible way using all kinds of high-performance computers that have completely different hardware and architectures. In the future, these will also include exascale supercomputers that perform more than a billion billion calculations per second – up to a hundred times more than today’s most powerful machines.

Is it difficult to build such a flexible computing system?

Heirich: Yes. Supercomputers are very complex with millions of processors running in parallel, and we need to figure out how to make use of their individual architectures most efficiently. At Stanford, we’re therefore developing a programming system, called Legion, that allows people to write programs that are portable across very different high-performance computer architectures.

Traditionally, if you want to run a program with the best possible performance on a new computer system, you may need to rewrite significant parts of the program so that it matches the new architecture. That’s very labor and cost intensive. Legion, on the other hand, is specifically designed to be used on diverse architectures and requires only relatively small tweaks when moving from one system to another. This approach prepares us for whatever the future of computing looks like. At SLAC, we’re now starting to adapt Legion to the needs of LCLS-II.

We’re also looking into how we can visualize the scientific data after they are analyzed at NERSC.

NERSC Cray XC40 Cori II supercomputer

LBL NERSC Cray XC30 Edison supercomputer

The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

NERSC PDSF

PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

The analysis will be done on thousands of processors, and it’s challenging to orchestrate this process and put it together into one coherent visual picture. We just presented one way to approach this problem at the supercomputing conference SC17 in November.

What’s the goal for the coming year?

Slaughter: We’re working with the LCLS team on building an initial data analysis prototype. One goal is to get a first test case running on the new system. This will be done with X-ray crystallography data from LCLS, which are used to reconstruct the 3-D atomic structure of important biomolecules, such as proteins. The new system will be much more responsive than the old one. It’ll be able to read and analyze data at the same time, whereas the old system can only do one or the other at any given moment.
Will other research areas besides X-ray science profit from your work?

Slaughter: Yes. Alex is working on growing our division, identifying potential projects across the lab and expanding our research portfolio. Although we’re concentrating on LCLS-II right now, we’re interested in joining other projects, such as the Large Synoptic Survey Telescope (LSST). SLAC is building the LSST camera, a 3.2-gigapixel digital camera that will capture unprecedented images of the night sky. But it will also produce enormous piles of data – millions of gigabytes per year. Progress in computer science is needed to efficiently handle these data volumes.

Heirich: SLAC and its close partnership with Stanford Computer Science make for a great research environment. There is also a lot of interest in machine learning. In this form of artificial intelligence, computer programs get better and more efficient over time by learning from the tasks they performed in the past. It’s a very active research field that has seen a lot of growth over the past five years, and machine learning has become remarkably effective in solving complex problems that previously needed to be done by human beings.

Many groups at SLAC and Stanford are exploring how they can exploit machine learning, including teams working in X-ray science, particle physics, astrophysics, accelerator research and more. But there are very fundamental computer science problems to solve. As machine learning replaces some conventional analysis methods, one big question is, for example, whether the solutions it generates are as reliable as those obtained in the conventional way.

LCLS and NERSC are DOE Office of Science user facilities. Legion is being developed at Stanford with funding from DOE’s ExaCT Combustion Co-Design Center, Scientific Data Management, Analysis and Visualization program and Exascale Computing Project (ECP) as well as other contributions. SLAC’s Computer Science Division receives funding from the ECP.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

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

From SLAC: “SLAC Scientists Investigate How Metal 3-D Printing Can Avoid Producing Flawed Parts”

SLAC Lab

January 30, 2018
Kimber Price

A metal 3-D printed sample the team used for experiments. (Johanna Nelson Weker/SLAC)

Video – 3-D printing of a metal sample inside an X-ray chamber

This video shows the 3-D printing of a metal sample inside an X-ray characterization chamber at Lawrence Livermore National Laboratory before the chamber was dismantled, transported to SLAC and rebuilt. At SLAC the glass windows were replaced with X-ray transparent beryllium windows. The chamber allows researchers to observe metal 3-D printing in real time. No video credit.

This video shows the 3-D printing of a metal sample inside an X-ray characterization chamber at Lawrence Livermore National Laboratory before the chamber was dismantled, transported to SLAC and rebuilt. At SLAC the glass windows were replaced with X-ray transparent beryllium windows. The chamber allows researchers to observe metal 3-D printing in real time. No video credit.

SLAC staff scientist Johanna Nelson Weker, front, leads a study on metal 3-D printing at SLAC’s Stanford Synchrotron Radiation Lightsource with researchers Andrew Kiss and Nick Calta, back. (Dawn Harmer/SLAC).

SLAC/SSRL

Pits Among the Layers

In metal 3-D printing, a thin layer of powdered metal, such as titanium alloys, steel, aluminum alloys, or copper, is distributed on a platform and selectively melted by a high-powered laser beam. Then the platform is lowered, a new layer of metal powder is applied and the process is repeated until the object is fully formed.

This process often results in the formation of pits, or weak spots, when the metal cools and hardens unevenly while building up the layers. In the SLAC X-ray experiments, scientists are analyzing every aspect of the process ­– the kind of metal used, the level of heat from the laser, the speed at which the metal heats and cools – to find the best combination for eliminating pits, controlling the microstructure, and manufacturing strong metal parts.

“We are providing the fundamental physics research that will help us identify which aspects of metal 3-D printing are important,” says Chris Tassone, a staff scientist in SSRL’s Materials Science Division. It’s practical information, he says, that could eventually lead to writing recipes for 3-D printer laser settings that manufacturers can use to produce sturdy parts.

Diving in for a Better View

Until recently, researchers watched from above as layers were being added to form a part. Because they couldn’t see below the surface of the metal, it was impossible to tell how deeply the laser was melting the layers as each one was applied. They tried imaging the growing layers with thermal radiation, or heat, but this did not give them enough information about what was causing the weak spots. X-rays, however, give researchers an excellent tool to see and record what’s happening inside the part as it’s being built.

The scientists are using two X-ray methods to see what happens during metal 3-D printing. With one type of X-ray light, they create micron-resolution images of what happens as the layers of metal build up. The second method bounces X-rays off the atoms in the material to analyze its atomic structure as it changes from solid to liquid and back to solid form during the melting and cooling process.

Thus far, the group has been looking at lasers hitting layers of metal powder, but they also plan to investigate another approach called “directed energy deposition.” In this process, a laser beam hits and melts metal powder or wire as it is being laid down, allowing creation of more complex geometric forms. This sort of 3-D printing is especially useful in making repairs.

They also want to incorporate a high-speed camera into their experimental setup so they can collect photographs and video of the manufacturing process and correlate what they see with their X-ray data.

This is important to manufacturers and other researchers who use cameras to observe the process but don’t have access to an X-ray synchrotron, Nelson Weker says: “We want people to be able to connect what they see on their cameras with what we are measuring here so they can infer what’s happening below the surface of the growing metal material. We want to put meaning to those signatures.”

Other researchers on the metal 3-D printing project include Kevin Stone, Anthony Fong, Andrew Kiss and Vivek Thampy. SSRL is a DOE Office of Science user facility. The research was funded by the DOE Office of Energy Efficiency and Renewable Energy’s Advanced Manufacturing Office.

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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.