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Research, teaching and outreach in Physics at UW–Madison
News Archives
Physics technology shines at Summerfest Tech
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Kieran Furlong
Six top technologies in development at the University of Wisconsin-Madison and other UW System campuses headlined WARF Innovation Day at Summerfest Tech June 29. Wednesday’s event at BMO Tower in Milwaukee drew dozens of in-person and virtual investors who heard seven-minute pitch presentations on high-tech innovations ranging from fusion power to bridge safety monitoring.
“This forum was an exceptional opportunity for investors, media and the public to interface with top University of Wisconsin ideas,” said Erik Iverson, CEO of WARF. “It is this exchange of passion and expertise that forwards the state’s innovation ecosystem.”
One of the presenters included Kieran Furlong, an Honorary Fellow with the College of Letters & Science and CEO of Realta Fusion. Furlong is also the Technology-to-Market (T2M) Advisor to the WHAM project, a fusion energy project led by physics professor Cary Forest.
Furlong’s presentation, titled “Breakthrough Physics for Clean Energy Generation,” had this summary:
The Wisconsin High-field Axisymmetric Mirror (WHAM) project is leveraging major advances in superconducting magnets and plasma heating to pursue commercially viable nuclear fusion power. Fusion is how energy is generated in the sun, yet it has been tremendously challenging to harness on Earth. This project seeks to pave the way to a comparatively low-cost fusion device that can be a net energy generator.
The Department of Physics is happy to announce that Professor Brian Rebel has been promoted to full professor.
Rebel is a high energy experimentalist whose research focuses on accelerator-based neutrino physics. He joined the department as an associate professor with a joint appointment at Fermilab in 2018, where he is now a senior scientist.
“Professor Rebel is a leader in neutrino science, making major contributions to DUNE experiments and having published recently on four different neutrino collaborations,” says Mark Eriksson, physics department chair. “The department is thrilled about his promotion to full professor.”
Rebel has established himself as a leader in the Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE). DUNE is an international experiment for neutrino science and proton decay studies that consists of two neutrino detectors — one near Fermilab in Illinois, and one in South Dakota. The experiment will be installed in LBNF, which will produce the neutrino beam. Rebel is currently the DUNE Anode Plane Assembly (APA) consortium manager, and has previously led Fermilab’s DUNE Science Group.
Since 2005, Rebel has also been involved in Fermilab’s NOvA experiment, which uses precision measurements to investigate the flavor oscillations of neutrinos that are not predicted by the Standard Model. He is currently serving as the co-convener of the analysis group searching for oscillations of active neutrino flavors into a sterile neutrino.
Rebel is currently training three graduate students and two postdoctoral scholars, and expects to graduate his first UW–Madison doctoral student soon. Additionally, he supervised several trainees at Fermilab before he came to UW–Madison. He has enjoyed teaching both introductory physics as well as physics courses for non-majors, and is an effective and engaging teacher.
Congrats, Prof. Rebel, on this well-deserved recognition!
NASA Sounding Rocket Mission Seeks Source of X-rays Emanating From Inner Galaxy
To human eyes, the night sky between the stars appears dark, the void of space. But X-ray telescopes capture a profoundly different view. Like a distant firework show, our images of the X-ray sky reveal a universe blooming with activity. They hint at yet unknown cosmic eruptions coming from somewhere deeper into our galaxy.
To help find the source of these mysterious X-rays, University of Wisconsin—Madison astronomer Dan McCammon and his team are launching the X-ray Quantum Calorimeter or XQC instrument. XQC will make its seventh trip to space aboard a NASA suborbital rocket. This time, XQC will observe a patch of X-ray light with 50 times better energy resolution than ever before, key to revealing its source. The launch window opens at Equatorial Launch Australia’s Arnhem Space Centre in Northern Territory, Australia, on June 26, 2022.
Because Earth’s atmosphere absorbs X-rays, our first views of cosmic X-rays awaited the space age. In June 1962, physicists Bruno Rossi and Ricardo Giacconi launched the first X-ray detector into space. The flight revealed the first sources of X-rays beyond our Sun: Scorpius X-1, a binary star system some 9,000 light-years away, as well as a diffuse glow spread across the sky. The discovery founded the field of X-ray astronomy and later won Giacconi a share of the 2002 Nobel Prize in physics.
This image shows a “map” of the night sky in soft X-ray light in galactic coordinates, with the Sun positioned at the center. The horizontal line across the middle of the image runs along the plane of our disk-shaped galaxy. University of Wisconsin, Madison astronomer Dan McCammon and the XQC team will be observing the bright blob in the center of the image, circled with a dotted line. This is the southern part of a roughly circular blob around the center of the galaxy, cut in half by cold absorbing gas in the plane of the galaxy. Credits: Snowden et al., 1997
Scientists have now mapped the X-ray sky in ever-finer detail with the help of other NASA X-ray missions. Still, there are several bright patches whose sources are unknown. For the upcoming flight, McCammon and his team will target a patch of X-ray light only partly visible from the Northern Hemisphere.
“It covers a big part of the galaxy, but we needed to be in the Southern Hemisphere to see that part of the sky,” McCammon said. “We’ve been waiting a long time for this expedition to Australia.”
Scientists believe the X-ray patch comes from diffuse, hot gas heated by supernovae, the brilliant eruptions of dying stars. The XQC mission is investigating two possible sources, illustrated in the graphic below.
One possibility is that the X-rays come from gas heated by “Type Ia” supernovae, the death throes of massive stars that live tens to hundreds of millions of years. The inner part of our galaxy has a high enough concentration of this type of supernova to heat the X-ray patch McCammon is investigating.
The other possible source is “Type II” supernovae. The stars behind Type II supernova are even more massive, burn brighter and hotter, and live just a few million years before going supernova. They occur in active star-forming regions, like those in one of our galaxy’s inner spiral arms.
To distinguish these possibilities, XQC will analyze the X-ray light, looking for traces of oxygen and iron. More oxygen points to Type II supernovae, while less oxygen suggests Type 1a supernovae. The physics behind it is complex but ultimately stems from how long the stars burned before erupting. The smaller stars behind Type 1a supernovae burn for longer, leaving less oxygen behind than Type II supernovae.
Of course, the flight is likely to capture much more information as well. “This is an exploration with a new capability – we want to see what we can see,” McCammon said. “Every time we look at the X-ray sky with a new capability, it turns out to be more complicated that we supposed.”
After the flight, the team plans to recover the instrument. It will retire to Oak Ridge National Labs in Tennessee where it will aid in laboratory experiments.
This flight will be XQC’s final trip to space, but the very first from the new Arnhem Space Centre rocket range in East Arnhem, Australia. XQC is part of a three-rocket campaign launching from the range in June and July 2022, NASA’s first time launching from Australia since 1995.
Sau Lan Wu honored with named planet
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The International Astronomical Union (IAU) has named a minor planet ‘Saulanwu’ after UW–Madison physics professor Sau Lan Wu.
The planet (177770) ‘Saulanwu’ (=2005 JE163) was discovered on May 8, 2005 at Mt Lemmon observatory in southern Arizona by a NASA funded project, the Catalina Sky Survey. More details about the planet can be found from NASA’s JPL website, including a sketch of the planet’s orbit, which is in the asteroid belt between Mars and Jupiter. Minor planet ‘Saulanwu’ is about two kilometers in diameter, and it takes four years to orbit the sun once. This planet is relatively stable, dynamically, and is expected to remain in our cosmos for millions of years to come.
Wu was nominated for this honor by astronomer Gregory J. Leonard from the University of Arizona’s Department of Planetary Sciences.
Victor Brar, Moritz Münchmeyer funded through latest round of Research Forward
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Victor Brar
Sixteen projects — including two from Physics — have been selected for funding in the second round of Research Forward, a program to stimulate innovative and groundbreaking research at UW–Madison that is collaborative, multidisciplinary and potentially transformative.
The winning projects were chosen from 96 proposals submitted by applicants across campus. The Research Forward initiative is sponsored by the Office of the Vice Chancellor for Research and Graduate Education and is supported by the Wisconsin Alumni Research Foundation, which provides funding for one or two years, depending on the needs and scope of the project. Some of the projects that have been funded have the potential to fundamentally transform a field of study.
Moritz Münchmeyer
The Research Forward initiative is sponsored by the Office of the Vice Chancellor for Research and Graduate Education and is supported by the Wisconsin Alumni Research Foundation, which provides funding for one or two years, depending on the needs and scope of the project. Some of the projects that have been funded have the potential to fundamentally transform a field of study.
“Research Forward encourages collaboration among campus PIs, enhances PhD student and postdoc training, and strengthens our external grant funding requests,” says Steve Ackerman, vice chancellor for research and graduate education. “The projects we selected are truly forward-looking and use innovative approaches and tools such as state-of-the-art machine learning methods, 3D printing techniques and geostationary satellites.”
The Physics projects are:
Multiscale Photonic Structures for Complete Opto-Electronic Control of Light, Victor Brar, assistant professor of physics. This project will lead to creation of a crucial electrical component for holographic displays, high-resolution biomedical imaging, and laser-based range finders valuable for self-driving cars.
Reconstructing the Big Bang with Physics-Guided Machine Learning, Moritz Muenchmeyer, assistant professor of physics. Physicists and computer scientists will develop a new technique to look back in time and reconstruct what happened at the Big Bang, aided by recent developments in machine learning. Gary Shiu is a co-PI of this award.
Keith Bechtol selected to Department of Energy Early Career Research Program
The funding will allow Bechtol and his group to first work on commissioning the Vera C. Rubin Observatory in preparation for the Legacy Survey of Space and Time (LSST), then they will transition to data collection and analysis for their cosmology research.
“We are anticipating that LSST will catalog more stars, more galaxies and more solar system objects during its first year of operations than all previous telescopes combined,” Bechtol says.
Rubin Observatory’s telescope will have an eight-meter diameter mirror and a ten square degree field of view. The 3.2-billion-pixel camera will collect an image every 30 seconds. All told, LSST will amass around 10 terabytes of data every night.
Bechtol has leadership roles for building and commissioning the observatory as well as with the Dark Energy Science Collaboration (DESC), the international science collaboration that will make high accuracy measurements of fundamental cosmological parameters using LSST data. At least seven other collaborations have formed around different science areas to analyze the data. Rubin Observatory is preparing to serve the LSST data to many thousands of scientists in the US, Chile, and at international partner institutions around the world.
“DESC will use LSST data to address several outstanding physics questions, such as: Why are the distances between galaxies growing at an accelerating rate? What is the fundamental nature of dark matter? What is the absolute mass scale of neutrinos? How did the universe begin and what were the initial conditions?” Bechtol says.
Bechtol will receive around $150,000 per year for five years to cover summer salary and research expenses. The research expenses will be used mostly to cover the analyses after the data collection starts. However, because there cannot be useful data without the initial commissioning and science validation steps — and because the Observatory is still a couple of years away from first light — the DOE award is also supporting Bechtol’s efforts during the commissioning phase to accelerate the realization of DESC science goals.
“For me, the most important thing about this award is that it will provide more opportunity for students and postdocs to directly contribute to this ambitious experiment. Turning on a new experiment of this scale and complexity doesn’t happen every day,” Bechtol says. “For my research group to be able to participate firsthand in the commissioning, seeing first light, and contributing to the first cosmology results is so valuable from a career development perspective. We are training the next generation of experiment builders.”
The DOE early career program is open to untenured, tenure-track professors at a U.S. academic institution (or a full-time employee at a DOE national laboratory) who received a PhD within the past 10 years. Research topics are required to fall within one of the DOE Office of Science’s eight major program offices, including high energy physics, the program through which Bechtol’s award was made.
Thad Walker honored with Vilas Distinguished Achievement Professorship
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Thad Walker
Extraordinary members of the University of Wisconsin–Madison faculty, including physics professor Thad Walker, have been honored during the last year with awards supported by the estate of professor, U.S. senator and UW Regent William F. Vilas (1840-1908).
Walker was one of seventeen professors were named to Vilas Distinguished Achievement Professorships, an award recognizing distinguished scholarship as well as standout efforts in teaching and service. The professorship provides five years of flexible funding — two-thirds of which is provided by the Office of the Provost through the generosity of the Vilas trustees and one-third provided by the school or college whose dean nominated the winner.
In addition, nine professors received Vilas Faculty Mid-Career Investigator Awards and six professors received Vilas Faculty Early Career Investigator Awards.
Detailed analysis of old star provides template for heavy element formation
The fusion furnaces that are the universe’s stars create the elements from helium up to iron. But iron is only number 26 on the periodic table out of well over 100 known elements. So the heavier ones, like gold, lead and uranium, must come from somewhere other than fusion.
Scientists have long known that those heavy elements come from neutron capture, where neutrons are added to an element that make it unstable, then it radioactively decays and its atomic number increases by one. Nearly 70 years ago, they confirmed one site, or event, of a neutron capture method known as the slow, or s-process. The rapid, or r-process, was not confirmed with a site until 2017, when the LIGO/VIRGO collaboration detected a neutron star merger.
“With a neutron star merger, the neutron stars are ripped apart and they throw out neutrons, and you can build lots of heavy elements out of these neutron stars,” says Jim Lawler, a professor of physics at the University of Wisconsin–Madison. “The mystery arises when we look at the total r-process inventory of our home galaxy: Can we explain all that with neutron star mergers or are there additional sites?”
In a new study led by astronomers from the University of Michigan, Lawler and colleagues identified the elemental composition of HD 222925, a Milky Way star located over 1400 lightyears from earth. Their analysis confirmed that the star was rich in r-process elements, and they were able to identify and calculate the relative abundance of each element. They also found that the star is iron- and metal-poor, a proxy for age that indicates HD 222925 is relatively old and provides information about early star formation.
“We were able to determine a complete r-process abundance pattern for what we think is probably one event that happened early in the beginning of the universe,” Lawler says. “So that r-process template now can be used to screen various models of the nuclear physics that produce the r-process and see if the models for all sites are physically correct.”
At UW–Madison, Lawler and scientist Elizabeth Denhartog contributed the spectroscopic analysis that identified the elements in the star. Every element has a unique electromagnetic spectrum that can be separated into spectral lines using a diffraction grating — just like a prism separates white light into a rainbow. HD 222925 is a relatively bright star, meaning it provided stronger spectra to analyze. It was also identified by the Hubble Space Telescope, providing access to data in the ultraviolet range that is normally blocked by the ozone layer and undetectable by telescopes on Earth.
THIS STUDY WAS SUPPORTED IN PART BY NASA (GRANTS GO-15657, GO-15951, AND 80NSSC21K0627); U.S. NATIONAL SCIENCE FOUNDATION (NSF, GRANTS PHY 14-30152, OISE 1927130, AST 1716251 AND AST 1815403); AND THE U.S. DEPARTMENT OF ENERGY (GRANT DE-FG02-95-ER40934); AND NOIRLAB, WHICH IS MANAGED UNDER A COOPERATIVE AGREEMENT WITH THE NSF.
Researchers aim X-rays at century-old plant secretions for insight into Aboriginal Australian cultural heritage
For tens of thousands of years, Aboriginal Australians have created some of the world’s most striking artworks. Today their work continues long lines of ancestral traditions, stories of the past and connections to current cultural landscapes, which is why researchers are keen on better understanding and preserving the cultural heritage within.
Secretions called exudate cover parts of the spike of a Xanthorrhoea plant — colloquially called “grass tree” or “yakka” — used in aboriginal art. PHOTO COURTESY FLINDERS UNIVERSITY, SOUTH AUSTRALIA
In particular, knowing the chemical composition of pigments and binders that Aboriginal Australian artists employ could allow archaeological scientists and art conservators to identify these materials in important cultural heritage objects. Now, researchers are turning to X-ray science to help reveal the composition of the materials used in Aboriginal Australian cultural heritage – starting with the analysis of century-old samples of plant secretions, or exudates.
Aboriginal Australians continue to use plant exudates, such as resins and gums, to create rock and bark paintings and for practical applications, such as hafting stone points to handles. But just what these plant materials are made of is not well known.
Therefore, scientists from six universities and laboratories around the world turned to high-energy X-rays at the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy’s SLAC National Accelerator Laboratory and the synchrotron SOLEIL in France. The team aimed X-rays at ten well-preserved plant exudate samples from the native Australian genera Eucalyptus, Callitris, Xanthorrhoea and Acacia. The samples had been collected more than a century ago and held in various institutions in South Australia.
The results of their study were clearer and more profound than expected.
“We got the breakthrough data we had hoped for,” says Uwe Bergmann, physicist at the University of Wisconsin–Madison and former SLAC scientist who develops new X-ray methods. “For the first time, we were able to see the molecular structure of a well-preserved collection of native Australian plant samples, which might allow us to discover their existence in other important cultural heritage objects.”
Researchers today published their results in the Proceedings of the National Academy of Sciences.
Uwe Bergmann
Looking below the surface
Over time, the surface of plant exudates can change as the materials age. Even if these changes are just nanometers thick, they can still block the view underneath it.
“We had to see into the bulk of the material beneath this top layer or we’d have no new information about the plant exudates,” SSRL Lead Scientist Dimosthenis Sokaras says.
Conventionally, molecules with carbon and oxygen are studied with lower-energy, so-called “soft” X-rays, that would not be able to penetrate through the debris layer. For this study, researchers sent high-energy X-ray photons, called “hard” X-rays, into the sample. The photons squeezed past foggy top layers and into the sample’s elemental arrangements beneath. Hard X-rays don’t get stuck in the surface, whereas soft X-rays do, Sokaras says.
Once inside, the high-energy photons scattered off of the plant exudate’s elements and were captured by a large array of perfectly aligned, silicon crystals at SSRL. The crystals filtered out only the scattered X-rays of one specific wavelength and funneled them into a small detector, kind of like how a kitchen sink funnels water drops down its drain.
Next, the team matched the wavelength difference between the incident and scattered photons to the energy levels of a plant exudate’s carbon and oxygen, providing the detailed molecular information about the unique Australian samples.
Century-old plant exudate samples in amber jars. Researchers mapped the chemistries of these samples using high-energy photons, knowledge that will help study and preserve the work of aboriginal artists who used plant material. PHOTO COURTESY FLINDERS UNIVERSITY, SOUTH AUSTRALIA
A path for the future
Understanding the chemistries of each plant exudate will allow for a better understanding of identification and conservation approaches of Aboriginal Australian art and tools, Rafaella Georgiou, a physicist at Synchrotron SOLEIL, said.
“Now we can go ahead and study other organic materials of cultural importance using this powerful X-ray technique,” she says.
Researchers hope that people who work in cultural heritage analysis will see this powerful synchrotron radiation technique as a valuable method for determining the chemistries of their samples.
“We want to reach out to that scientific community and say, ‘Look, if you want to learn something about your cultural heritage samples, you can come to synchrotrons like SSRL,’” Bergmann says.
SSRL is a DOE Office of Science user facility. In addition to SSRL, parts of this research were carried out at SOLEIL in France and three CNRS laboratories (PPSM, IPANEMA, IMPMC). The University of Pisa, the Université Paris-Saclay, the University of Melbourne, Flinders University, the Australian Synchrotron International Synchrotron Access Program, and other organizations also supported this research.
Kevin Anderson ’83 never abandoned his youthful passion, and now he’s one of the most successful authors in his field.
When he was growing up in Wisconsin, there was little on the surface of Kevin Anderson ’83’s life to suggest he’d become one of the world’s most prolific science-fiction authors.
“I was an alien child, I think,” says Anderson, who grew up first in Racine and then in Oregon, outside of Madison. “My dad was a bank president, and my mom was an accountant. We didn’t have an artsy streak in our family.”
Still, when Anderson was five, he saw the 1953 film The War of the Worlds and was mesmerized. Later he raced through the Ray Bradbury paperbacks he checked out of his school library, and he was left with one consuming thought.
“I wanted to tell stories like that,” he says.
In ninth grade, Anderson submitted his first science fiction story to a magazine.
“I got my first rejection slip,” he says. “I now have around 800 rejection slips. But I’ve had a couple of successes, too.”
You could say that. Anderson, who turns 60 in 2022 and now lives with his wife, Rebecca Moesta, outside Colorado Springs, has published a staggering 175 books, though that number may already be dated. Many have landed on various best-seller lists.
He has written Star Wars novels, X-Files novels, Dune novels in collaboration with Brian Herbert (son of Dune creator Frank Herbert), and even steampunk fantasy novels with a rock-and-roll star for a coauthor. Clockwork Lives, Anderson’s second novel with the late Rush drummer, Neil Peart, is his favorite among all his books.
The genesis of their unlikely friendship is itself a good tale. It followed the appearance of Resurrection, Inc., Anderson’s first novel, published when he was 25 and working as a technical writer at the Lawrence Livermore National Laboratory in California.
Anderson got the Livermore job after graduating from UW–Madison with a degree in physics and astronomy and a minor in Russian history. He took a few writing classes but says, “I guess I wanted to know things to write about rather than how to write. I wanted to have ingredients, not cookbooks.”
Recalling his time at the UW, Anderson notes, “I loved the campus and student life. I still miss Rocky Rococo’s pizza. That was one of my main food groups.”
More seriously, he adds, “Growing up in a small town was great. But being sort of an odd duck who liked to read comic books and make up stories about space battles and things — I didn’t have a whole lot of people that I had much in common with. It wasn’t until I got to the university that I found other writers and creative people.”
Resurrection, Inc. was inspired by the Rush album Grace under Pressure. Anderson had admired the band for years. He sent signed copies of the novel to Mercury Records, asking that they be forwarded to Rush, not really expecting that to happen.
Yet Peart not only received the novel, he loved it and sent Anderson a seven-page, single-spaced letter saying so. A correspondence ensued. The friendship included yearly invitations for Anderson to hang backstage at Rush concerts. It was in 2010 while hiking on a mountain in Colorado — a passion of Anderson’s — that the two agreed to collaborate on a novelization of Rush’s album Clockwork Angels. The book appeared in 2012.
Anderson has published a staggering 175 books, with many landing on various best-seller lists.
When Anderson met Moesta, a science-fiction fan who was working as a proofreader and copy editor at the Livermore lab, “we hit it off right away,” he says. In three decades of marriage, they’ve coauthored dozens of books, including an entire series of Star Wars adventures for young adults. They moved to Colorado in 1997, and in 2021, Anderson was inducted into the Colorado Authors’ Hall of Fame.
Anderson’s writing has paid off handsomely. A 1997 Publishers Weekly article stated that he and Herbert had signed a $3 million deal for a trilogy of sequels to Dune. Anderson’s website notes that 23 million copies of his books are in print in more than 30 languages.
These days he’s busier than ever. Anderson teaches writing at Western Colorado University, and he and Moesta have a publishing company, WordFire Press, that has released some 400 titles.
When his schedule allows, Anderson likes to write in the mornings. But he doesn’t sit at a computer. Instead, he heads outside and talks.
“I do all my writing on a digital recorder,” he says. “I love to go out on the trail and dictate — usually two chapters a morning. I go for a walk and tell myself a story. I send it off to a transcriptionist, who sends it back. Then I have to polish it, of course.”
Anderson has several titles coming in 2022, including the third book in the Dune trilogy and the last novel in his Clockwork series with Peart, who died in 2020. More will surely follow. This is an author who loves what he’s doing.
“It’s exactly what I’ve wanted to do since I was five years old and saw War of the Worlds,” he says. “Not many people can say they’ve built their entire career on what they wanted to be when they were a little kid.” •
