Buonanno Receives Galileo Galilei Medal

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Category: Department News

Published: Thursday, February 18 2021 12:45

Alessandra Buonanno has been awarded the Galileo Galilei Medal by the National Institute for Nuclear Physics (INFN). Buonanno was cited with Thibault Damour of the Institut des Hautes Études Scientifiques in Paris and Frans Pretorius of Princeton University “for the fundamental understanding of sources of gravitational radiation by complementary analytic and numerical techniques, enabling predictions that have been confirmed by gravitational wave observations and are now key tools in this new branch of astronomy”.  

Stefania De Curtis, director of the Galileo Galilei Institute, wrote that "Professors Buonanno and Damour, and professor Pretorius proposed two complementary approaches, analytical and numerical, to describe the behavior of two black holes spiraling around each other until they collide. Their description was used for the analysis of experimental data that, in 2015, led the LIGO and VIRGO scientific collaborations to the observation of the first gravitational waves emitted by the collision of two black holes". 2021 Galileo Galilei medal

Buonanno is the director of the Astrophysical and Cosmological Relativity Department at the Max Planck Institute for Gravitational Physics in Potsdam and a Research Professor at the University of Maryland. She joined the UMD Physics in 2005, and received an Alfred P. Sloan Foundation Fellowship and the Richard A. Ferrell Distinguished Faculty Fellowship. She is a Fellow of the American Physical Society and the International Society of General Relativity and Gravitation. In 2018, she received the Leibniz Prize, Germany's prestigious research award. 

In discussing the work that led to the Galilei Medal, Buonanno explained that "To identify the source that generated the gravitational waves we observe on Earth, we need hundred thousand of waveform models. To achieve this goal about 20 years ago we introduced a novel approach to solve analytically the two-body problem in general relativity. This approach paved the way to develop the highly precise waveform models that today are routinely used by LIGO and VIRGO to detect binary systems composed of black holes and neutron stars and infer unique information about astrophysics, cosmology and gravity”. She offers futher discussion in this video.  

Buonanno and others detailed UMD's contributions to gravitational studies in a 2016 forum, A Celebration of Gravitational Waves. 

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This story was adapted from the INFN website; for further information on the award, see https://home.infn.it/en/media-outreach/press-releases/4303-the-2021-galileo-galilei-medal-goes-to-alessandra-buonanno-thibault-damour-and-frans-pretorius

CU²MiP: Online and Expanded

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Category: Department News

Published: Monday, February 08 2021 12:28

In January 2021, the University of Maryland’s Department of Physics and the National Institute of Standards and Technology (NIST) hosted the third Conference for Undergraduate Underrepresented Minorities in Physics (CU²MiP). The conference launched in 2016 to address the historically low representation of minorities in the physics community.

This year, UMD President Darryll J. Pines gave a welcoming and encouraging address. UMD College of Computer, Mathematical, and Natural Sciences Dean Amitabh Varshney, NIST director Walter Copan. Physics Chair Steve Rolston, Rowan University’s Tabbatha Dobbins and Howard University Thomas A. Searles were among many speakers, workshop leaders and panelists.

Though COVID-19 required an online gathering this year, organizers adapted and expanded the program in significant ways, offering a research panel on quantum science, helpful videos and an entire slate for high school students.

“The quantum panel and quantum speakers for both undergrad and high school were very well received,” said Donna Hammer, director of education for the Department of Physics. Among the speakers at the quantum panel was alumna Ana Maria Rey (Ph.D. ’04), recipient of a MacArthur “genius” grant.

CU²MiP videos included several lab tours, as well as interviews with UMD students explaining their choice and enjoyment of physics.

Other CU2MiP highlights included a fireside chat where College Park Professor Sylvester James Gates Jr. was interviewed by his daughter, Delilah Gates (B.S. ’15), who is now a physics Ph.D. candidate at Harvard University. The elder Gates mentioned events in his life that helped him succeed as a physicist and contribute to society. He also addressed “imposter syndrome,” which is a sense of not belonging or being good enough, and discussed ways that students might overcome it.

Jorge Ramirez Ortiz and Daniel Serrano of UMD gave a presentation on Rostros Físicos, a new multimedia celebration of the successes of Latinx/Latin American physicists across all stages of the scientific career path.

Fostering collegiality has always been a primary CU²MiP goal, and this year’s virtual gathering continued this emphasis.

“Adding mentoring chats throughout the conference fostered meaningful networking beyond the breakout rooms associated with the panels and workshops,” Hammer said. “Drop-in mentoring provided shared stories, guidance and collaboration in real time.”

Undergraduates responded positively.

“It was great to meet people and I found all of the speakers inspiring and engaging!” wrote one participant. Another expressed gratitude for the conference, noting, “I spoke with a lot of supportive people on the prospects of research.” 

The high school conference featured a plenary talk by Professor Willie Rockward, the physics department chair at Morgan State University, on “Your Pathway in Physics using Passion, Purpose, and Problem-solving.” High school student Anisha Musti discussed founding Q-munity, a group of high school students working together in quantum computing. College Park Professor and Nobel Laureate Bill Phillips, along with NIST’s Angie Hight Walker, held a Quantum Science Showcase. 

Erin Lukomska-Schlauch, chair of the science department at Charles Herbert Flowers High School in Prince George’s County, helped to organize the conference, and found the experience memorable.

"As an educator, I will be taking a lot of what I learned back to my students, especially from the diversity workshops,” she said. "All the sessions that I attended were all really engaging, well planned and well executed."

Cindy Hollies, a teacher who has led many UMD physics summer programs, wrote, “I logged out of the conference on Sunday evening feeling proud and impressed with the young people leading the future of physics and amazed at the inspiring opportunities this conference presented for high school students. May there be many more such conferences.”  

Hammer observed that high school students learned about the many career opportunities opened by degrees in physics. As one student wrote, “…although I have taken a physics class, I didn't know much about its applications. I am very excited to take more related classes in college.”

Rolston, the department chair, was pleased with the undergraduate program and the extended efforts for high school students.

“We are grateful to everyone who contributed to CU²MiP,” he said. “Studying physics is a great path, not only to research and teaching careers, but to an extremely wide range of interesting professions. And the discipline itself helps develop a discerning way of seeing the world.”

"CU²MiP is a catalyst for change,” summarized Hammer. “The outcomes of each conference inspire me to keep moving forward and to know, not just believe, that real, positive change is possible and happening right now. As one student said to me, ‘This conference showed me that with each day I study physics, I'm part of the solution.’”

Pushing the Frontier of Extreme Light-Matter Interaction Research

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Category: Research News

Published: Monday, February 08 2021 05:33

University of Maryland Physics Professor Howard Milchberg and the students and postdoctoral researchers in his lab explore the dramatic results of experiments that push light to extremes in the presence of matter. In Milchberg’s opinion, researching the intense interactions between light and matter—which are only possible thanks to the revolutionary technology of lasers—brings together the most interesting aspects of physics.

“Once you considered the effect that an intense laser beam has on matter, the number of basic physics and application areas exploded,” said Milchberg, who also holds appointments in the Department of Electrical and Computer Engineering and the Institute for Research in Electronics and Applied Physics. “And understanding the interaction between intense light and matter requires bringing in tools from all areas of physics. It flexes all your physics muscles, experimental and theoretical, and it overlaps with all of the major areas. You have to deal with atomic physics, plasma physics, condensed matter physics, high-pressure physics and quantum physics. It is intellectually challenging and, as a bonus, it has many practical applications.”

In explorinIntense Laser-Matter Interactions Lab, University of Marylandg this research topic, his lab has discovered new physics and technological opportunities. From cutting-edge, powerful laser pulses to vortices made of light, recent research from Milchberg’s lab keeps revealing new ways that light and matter can come together and deliver new results.

The richness of this line of research comes from the fact that light is much more than just illumination traveling in straight lines at a constant speed. It is energy that can dance intricately as it travels and can interact with matter in exotic ways—including tearing atoms into pieces.

Light is traveling electric and magnetic energy, and it is often convenient to visualize light as traveling waves in the electric and magnetic fields. The hills and troughs in the waves represent the shifting of the strength and direction of the fields that push and pull on charged particles, like the protons and electrons that make up atoms. Powerful lasers can even accelerate charged particles to near the speed of light where the unusual behaviors described by Einstein’s theory of relativity come into play.

Milchberg’s lab often investigates the dramatic results of dialing a laser up to extreme strengths where it exceeds the field that connects the cores of atoms to its electrons. As researchers like Milchberg push lasers to greater and greater power levels, they reach a roadblock: A laser tends to spread its power out over an increasing area as it travels, and a laser with enough power will vaporize any solid piece of equipment that researchers try to use to corral it.

So an optical fiber, like those that commonly carry internet signals, are useless when faced with a powerful research laser. The central core and outer cladding that make up the fiber get destroyed without any chance to keep the light concentrated as it blazes forward.

But Milchberg’s research has uncovered multiple ways to use the interactions of light with matter to keep powerful laser beams contained. In papers published in the journals Physical Review Letters and Physical Review Research over the past year, Milchberg and his colleagues described two new ways to keep intense laser beams contained in a way that can accelerate particles and produce advanced coherent light sources. In addition to improving our understanding of how light and matter interact, the techniques might be implemented as tools for research in other areas, like high-energy physics, and for use in industrial and medical settings.Researchers have generated vortices of light that they describe as “edge-first flying donuts” and developed a new technique for imaging them in mid-flight. (Credit: Scott Hancock/University of Maryland)

In these projects, the group used its expertise to give the technology of optical fibers an extreme indestructible makeover. The key lies in building the waveguides—devices such as optical fibers that transport waves down a confined path—out of a material that has already been vaporized. The team forms the material—an energetic state of matter called a plasma—by letting a laser rip electrons free from their atoms to form a cloud of charged particles.

“A plasma waveguide has all the structure of an optical fiber, the classic core, the classic cladding,” Milchberg said. “Although in this case, it's indestructible. The hydrogen plasma forming the waveguide is already ripped up into its protons and electrons, so there's not much more violence you can do to it.”

For the first project, the group used two laser pulses: a solid beam and then a hollow tube of light matching the desired form of the outer shell. These two lasers allowed the team to independently craft the low-density cores and outer shells more carefully than previous approaches. This refined control improved the amount of power the techniques could concentrate and the distance the powerful pulses could travel­­­­­—a key to achieving desired levels of acceleration with a compact system.

The second approach produced a similar plasma waveguide but sacrificed the ability to tailor the resulting waveguide in favor of using a simpler, more accessible technique. In this technique, the researchers created a tube of low-density gas and then relied on the front edge of the powerful pulse to rip the electrons free and create the waveguide structure on-the-fly.

“It's actually simpler than the first method,” Milchberg said. “But there's less control. And we did an analysis which shows that if you want to have big diameter waveguides, the first method is actually more efficient than the second method.”

Both methods have potential uses as laser accelerators that can generate bursts of electrons of energy 10 billion electron volts, and Milchberg’s group is already doing those experiments.

In addition to these two techniques, Milchberg’s group is developing a technique that uses a 1,000 times higher density hydrogen gas to accelerate electrons without constructing a waveguide, while using 1,000 times less laser energy. This new technique improves on established methods by avoiding negative effects from the light vibrating the electrons as they get accelerated behind the intense laser pulse.

To do this, they used pulses of circularly polarized light that aren’t even as long as two full lengths of the waves of the light that is used. The field of circularly polarized light rotates as the light travels and this variation cancels out the effect of the asymmetries of the vibration from the light waves, enabling electron beams of higher quality than previous attempts. The denser gas used in this approach isn’t compatible with the 10 billion electron volt energies of the other approaches, but the technique might have its own niche to fill.

“Our experiments have spanned the higher through lower energy ends of laser-based acceleration,” Milchberg said. “The plasma waveguide effort is aimed at 10 billion electron volts, which is of high energy physics interest, while the newer research using millijoule pulses and dense hydrogen generates 15 million electron volts.  Although a high energy, it isn’t enough for high energy physics. But the energy is more than sufficient to do time-resolved medical imaging and materials imaging.”

But accelerating particles is not the only aspect of light-matter interactions that Milchberg’s group investigates. For instance, they also discovered new intricate effects that can be created in light pulses.

In a paper published in the journal Optica in December 2019, they generated and observed a new kind of light structure called a spatiotemporal optical vortex (STOV). STOVs are whorls in the way the phase—the property of light and other waves that tells you are where you are on the wave—changes in space and time. The researchers had to first develop a method to create these vortices and then figure out how to observe them in flight. The observation required analysis of the interaction between the STOVs and another bit of light while traveling through a thin glass window.

Understanding STOVs provides insight into how light produces the high-intensity laser effect called self-guiding. Milchberg’s team had previously discovered a naturally occurring form of STOV that behave like “optical smoke rings” and are crucial for all self-guiding processes. These vortices may also have applications in transmitting information because the twisting structure tends to stabilize itself by filling any sections that get knocked out—say by water droplets in the air that the signal travels through.

All of these research results represent new techniques that may be useful tools for researchers and industry, and they deepen our understanding of the intricate back-and-forth that can be engineered between light and matter.

“One of the things that I would say my group is known for is that all of our papers include theory and simulation that accompanies the experiments,” Milchberg said. “And that has provided an important feedback loop to guide and refine the experiments.”

Milchberg credits his group’s steady generation of new discoveries to his graduate students.

“I don't think I could have done any of this in a non-university setting,” Milchberg said. “I think the sort of relationship one has with students and they have with each other where we're all batting ideas back-and-forth and having a continuous free-for-all discussion—with crazy thoughts encouraged—is not the same as in a place filled with longtime Ph.D.s and an established hierarchy. The freedom to ask naïve questions and argue a lot is essential.”

Written by Bailey Bedford

Despite Pandemic, Physics Lab Courses Go On

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Category: Department News

Published: Monday, February 08 2021 05:33

Lab courses are where physics students learn firsthand that reality, even the one carefully curated by their instructors, is messy. Scales need to be recalibrated, projectiles hit lab benches instead of completing perfect arcs, and there’s always a mysterious source of issues popularly known as human error. Students traditionally tackle experiments in person, either individually or in pairs, on pre-arranged experimental stations. These are difficult things to replicate online or even in a physically distanced environment.

Nevertheless, when the pandemic hit, the UMD Department of Physics’ lab courses moved online for spring and summer 2020. And after the campus reopened in the fall, many of the lab courses were offered in person again, with a multitude of safety precautions and—perhaps most importantly—without any known spread of COVID-19.

A small cast of dedicated department staff members worked hard to pull it all off. One key figure is Allen Monroe, the assistant director of physics instructional labs, who has been at UMD for 43 years. Monroe first started working for the department in 1978 while he was still in high school.

“They called me a gopher,” said Monroe, “because I would ‘go for’ this and ‘go for’ that.”

He was hired to run the labs for classes taken by physics majors in 1984 and has remained here ever since. During this time, he went from lab manager to lab coordinator to assistant director, and he earned a bachelor’s degree in industrial education in 1994 from UMD.

Monroe says remaining at the university for this long has been easy.

“There's always something new to learn,” Monroe said. “And it's always something different. It’s fascinating. And at this point, I’m seeing the whole picture.”

The whole picture can be pretty overwhelming.

“During a typical semester up here, I've got 2,000 students roaming through these hallways going through these labs every week,” Monroe said.  

When the university moved to online classes in March, each instructor handled the situation differently: some asked students do simulations, while others provided students data to be analyzed. But this wasn’t going to work for an entire course. Monroe needed to begin planning for summer classes, which would be taught entirely online. Migrating the whole operation to Zoom was an enormous and time-sensitive undertaking—there were lab courses starting in under two months.

“We had to work very quickly,” said Monroe, “because, you know, this was early April and we had to have this stuff ready for June 1.”

But even with his decades of experience, Monroe says he could not have done it alone. He relied on Physics Professor and Joint Quantum Institute Co-director Frederick Wellstood, who has been a mainstay of the department’s labs for decades. Wellstood first began designing lab courses in the mid-1990s with Distinguished University Professor of Physics Jordan Goodman and continued to do so after he became associate chair of undergraduate education in 1999. After he left that post in 2004, he remained the go-to physicist for all lab-related things.

“This is my secret side job, this is my night job,” Wellstood said.

For more than 20 years, he designed and reinvented much of the UMD physics lab curriculum. So last spring when Monroe needed help, Wellstood stepped up to the plate.

Not only did Monroe and Wellstood have to work quickly, they had to thread a fine needle. Students needed to be able to follow the experiment without actually being in the lab, and they also needed to stay engaged and not simply watch projectiles being thrown for them.

“You don't want the students to sit there and for their first thought to be ‘This is stupid,’” Monroe said. “So you have to kind of make it interesting.”

Wellstood and Monroe decided to go for an amalgam approach wherever possible. Wellstood filmed himself doing several versions of data collection, like sending projectiles along a few different paths. The students would choose one of the experiments, watch their chosen video and analyze the corresponding data themselves. 

Once the summer courses were humming along, Wellstood and Monroe immediately started preparing for the fall. They had to figure out how to quickly convert a lot more courses to online versions, as well as how to prepare for safe if partial, return to campus.

“We were in major survival mode, or firefighting mode,” Wellstood recalled.

A team headed by Professor and Associate Chair of Undergraduate Studies Carter Hall, Director of Student Services Donna Hammer, and professors Sarah Eno, Dan Lathrop and Kara Hoffman pitched in, obtaining a grant from the Provost’s office that allowed them to hire physics graduate student Brandon Johnson and undergraduate physics major Robert Wolle to record videos of themselves doing experiments and create online versions of the lab instruction manuals.

For the courses that were small enough to be held in person, Monroe wrote up safety protocols that were approved by the university. He put fans in all the windows, spaced out the experimental stations as much as possible, and converted some of the courses to a partial schedule, with alternating halves of the class coming in each week. If students ran into trouble doing one of the in-person labs, they would call their teaching assistant via Zoom, from their station to the front of the class, to avoid putting either the students or teaching assistant at risk.

Even with all the preparation, unpredictable problems arose.

“We used to run from 8 or 9 in the morning until 10 at night,” Monroe said. “In between every one of these sections, we had to go in and sanitize the room. And that all worked pretty good until we found that we were wiping the lettering off of keyboards.”

They did some research and switched to a less-abrasive cleaning product.

By putting in many extra hours and taking advantage of everything at their disposal, including online lab manual distribution tools, partial schedules and physically distanced in-person protocols, they pulled off a successful fall semester.

“It worked reasonably well,” said Wellstood, “which means it didn't catch fire and burn down. You know, we actually got through it.”

Both Wellstood and Monroe also credit the ensemble of people that made it all possible. Labs are staffed by Omar Torres, Greg Wolter and Catherine Owens.  

“We’ve tried to make sure that we can offer in-person experiments where it's possible,” said Wellstood, “and I think it’s a credit to the university that they let us try. And it’s a credit to the instructors.”

Monroe and Wellstood were ready when in-person spring classes began this week, and they’re proud of what they’ve pulled off thus far, but they both agree this past year has been extremely tough.  

“I'm looking forward to being able to open up again someday,” said Monroe, “because oh boy, it's exhausting.”

Written by Dina Genkina