Catching Cosmic Waves

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Category: Department News

Published: Wednesday, September 11 2024 05:24

University of Maryland (UMD) physics Ph.D. student Max Trevor found himself at a crossroads in 2016. Long fascinated by black holes, Trevor studied the enigmatic objects using X-ray astronomy as an undergraduate at the University of Maryland, Baltimore County (UMBC). But as his graduation date grew closer, Trevor wondered how he could take his passion to the next level. 

A groundbreaking announcement helped Trevor make a decision. In February 2016, scientists working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) project announced that for the first time in history, they detected gravitational waves—ripples in spacetime caused by some of the most violent events in the universe, waves that were caused by two black holes colliding with each other billions of light-years away. For Trevor and many other researchers, the Nobel Prize-winning discovery opened up an entirely new way of observing the universe.

“I had some experience with X-rays at UMBC, which I enjoyed,” Trevor recalled. “But hearing about LIGO’s success made me think that gravitational astronomy was going to be the new hot research area for high-energy astrophysics. At that moment, I knew I had to jump in no matter what.”

Knowing that he wanted to pursue gravitational wave research and LIGO science as a graduate student, Trevor found his perfect match at UMD. Attracted by the Department of Physics’ decades-long legacy of gravitational wave research and its continued influence on the field, he joined the lab of Peter Shawhan—a professor of physics and LIGO principal investigator—in spring 2020. Together, they’re working to detect gravitational waves and improve the quality of the data collected by LIGO to ensure its accuracy for all researchers in the community.  

Shawhan, whose work with LIGO stretches back to his time as a postdoctoral researcher at Caltech in 1999, says that the project has come a long way since the announcement of its initial success.

“Today we can laugh and say, ‘Oh, it’s just another regular binary black hole merger,’ but it was a really big deal the first time we were able to detect one,” Shawhan said. “We’re now in the middle of LIGO’s fourth observational run. Thanks to decades of hard work from across the globe and our efforts here at UMD, we can now observe these events every couple of days.” 

Filtering out the noise, keeping the community connected

Detecting gravitational waves in space is no easy task, even now. To do its job, LIGO requires incredibly sensitive instruments called interferometers, which use laser beams to measure minute changes in distance caused by passing gravitational waves. There are currently two interferometers in the United States—one in Louisiana and another in Washington state—and it’s Trevor’s job to weed through the flood of data these interferometers produce, searching for the telltale signs of a gravitational wave event. 

“I write code that performs data analysis in real time. It basically asks, ‘Is this a gravitational wave, yes or no?’ and it tries to match the data points with known profiles of gravitational waves,” Trevor explained. “After that’s done, it repeats the process with the next batch. All this happens in seconds.”

Although interferometers can capture faint signals that come with faraway colliding neutron stars or merging black holes, the instruments are also prone to catching other waves that may not be involved with the cosmos at all—like nearby earthquakes, moving trains or even local weather. Trevor uses tools like machine learning to correlate these irrelevant waves with potential sources and adjusts the detection code to avoid them. According to Shawhan, Trevor’s work is paving the way for upgrades to the LIGO system for future observational runs. 

“Max’s improvements to the algorithms are especially valuable for detecting signals that are particularly challenging to identify,” Shawhan said. “He’s made it easier to separate out irrelevant noise from signals that are made by massive black holes.” 

Trevor is also a major part of the effort to keep astronomers around the world in touch with LIGO’s latest findings. He’s in charge of operating and running a rapid alert software package called Python search for Compact Binary Coalescences (PyCBC). Any time a potential gravitational wave is detected in space, PyCBC feeds information into a system that sends out rapid alerts to astronomers around the world through NASA’s General Coordinates Network—giving them a chance to turn their telescopes to the right part of the sky and potentially catch any visible light from explosive cosmic events. Thanks in part to Trevor’s efforts, PyCBC sends out an alert about once every three days on average, helping to produce over 120 alerts total since LIGO’s current run began.  GCN diagram

“The data is collected, analyzed and sent out really quickly,” Trevor said. “The astronomy community can get preliminary alerts about a possible event within 30 seconds. Timeliness is essential so that scientists can observe the event right as it’s happening and we can form a better understanding of phenomena like black holes and neutron star mergers. It’s really fulfilling for me to play a part in keeping everyone connected.” 

Since joining Shawhan’s lab, Trevor has made significant contributions to LIGO, co-authoring over 30 highly cited papers on the data gathered by the system. As he nears the completion of his doctoral program at UMD, Trevor hopes to continue his work. He believes that his projects, specifically those focused on identifying extraneous noise sources, will play a role in optimizing the next version of LIGO and bring scientists closer to understanding the world beyond Earth. 

“This current observational run is projected to end in June 2025, which is when LIGO will undergo crucial upgrades and changes to make it even more sensitive than previous iterations,” Trevor said. “I’d like to keep doing my part in helping the project stay alive—and supporting the community that seeks to explain how our universe works.”  

UMD Physicists Advance NASA’s Mission to ‘Touch the Sun’

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Category: Research News

Published: Wednesday, September 11 2024 05:24

Those who say there’s “nothing new under the sun” must not know about NASA’s Parker Solar Probe mission. Since its launch in 2018, this spacecraft has been shedding new light on Earth’s sun—and University of Maryland physicists are behind many of its discoveries.

At its core, the Parker Solar Probe is “on a mission to touch the sun,” in NASA’s words. It endures extreme conditions while dipping in and out of the corona—the outermost layer of the sun’s atmosphere—to collect data on magnetic fields, plasma and energetic particles. The corona is at least 100 times hotter than the sun’s surface, but it’s no match for the spacecraft’s incredible speed and carbon composite shield, which can survive 2,500 degrees Fahrenheit. Last year, the spacecraft broke its own record for the fastest object ever made by humans. Parker Solar Probe (courtesy of NASA)

This engineering feat was built to solve solar mysteries that have long confounded scientists: What makes the sun’s corona so much hotter than its surface, and what powers the sun’s supersonic wind? These questions aren’t just of interest to scientists, either. The solar wind, which carries plasma and part of the sun’s magnetic field, can cause geomagnetic storms capable of knocking out power grids on Earth or endangering astronauts in space.

To better understand these mechanisms, the Parker Solar Probe will attempt its deepest dive into the corona on December 24, 2024, with plans to come within 3.9 million miles of the sun’s surface. Researchers hope its findings will help them predict space weather with greater accuracy and frequency in the future.

James Drake, a Distinguished University Professor in UMD’s Department of Physics and Institute for Physical Science and Technology (IPST), is helping to move the needle closer to that goal as a member of the Parker Solar Probe research team.

“This mission is what's called a discovery mission, and with a discovery mission we can never be sure what we're going to find,” Drake said. “But of course, everybody is most excited about the data that will come from the Parker Solar Probe getting very close to the sun because that will reveal new information about the solar wind.” 

Reconnecting the dots

Drake and Marc Swisdak, a research scientist in UMD’s Institute for Research in Electronics & Applied Physics (IREAP), have been involved with this mission since its inception. The researchers were asked to join because of their expertise in magnetic reconnection, a process that occurs when magnetic fields pointing in opposite directions cross-connect, releasing large amounts of magnetic energy.

Before the Parker Solar Probe, it was known that magnetic reconnection could produce solar flares and coronal mass ejections that launch magnetic energy and plasma out into space. However, this mission revealed just how important magnetic reconnection is to so many other solar processes. 

Early Parker Solar Probe data showed that magnetic reconnection was happening frequently near the equatorial plane of the heliosphere, the giant magnetic bubble that surrounds the sun and all of the planets. More specifically, this activity was observed in the heliospheric current sheet, which divides sectors of the magnetic field that point toward and away from the sun. 

“That was a big surprise,” Drake said of their findings. “Every time the spacecraft crossed the heliospheric current sheet, we saw evidence for reconnection and the associated heating and energization of the ambient plasma.”

In 2021, the Parker Solar Probe made another unexpected discovery: the existence of switchbacks in the solar wind, which Drake described as “kinks in the magnetic field.” Characterized by sharp changes in the magnetic field’s direction, these switchbacks loosely trace the shape of the letter S.

“No one predicted the switchbacks—at least not the magnitude and number of them—when Parker launched,” Swisdak said. 

To explain this odd phenomenon, Drake, Swisdak and other collaborators theorized that switchbacks were produced by magnetic reconnection in the corona. While the exact origin of those switchbacks hasn’t been definitively solved, it prompted UMD’s team to take a closer look at magnetic reconnection, especially its role in driving the solar wind.

“The role of reconnection has gone from something that was not necessarily that significant at the beginning to a major component of the entire Parker Solar Probe mission,” Drake said. “Because of our group's expertise on the magnetic reconnection topic, we have played a central role in much of this work.”

Last year, Drake and Swisdak co-authored a study with other members of the Parker science team that explained how the sun’s fast wind—one of two types of solar wind—can surpass 1 million miles per hour. They once again saw that magnetic reconnection was responsible, specifically the kind that occurs between open and closed magnetic fields, known as interchange reconnection.

To test their theories about solar activity, the UMD team also uses computer simulations to try to reproduce Parker observations. 

“I think that one of the things that convinced people that magnetic reconnection was a major driver of the solar wind is that our computer simulations were able to produce the energetic particles that they saw in the Parker Solar Probe data,” Drake said. 

As part of his dissertation, physics Ph.D. student Zhiyu Yin built the simulation model that is used to see how particles might accelerate during magnetic reconnection.

“Magnetic reconnection is very important, and our simulation model can help us connect theory with observations,” Yin said. “I'm really honored to be part of the Parker Solar Probe mission and to contribute to its work, and I believe it could lead to even more discoveries about the physics of the sun, giving us the confidence to take on more projects in exploring the solar system and other astrophysical realms.”

Swisdak explained that simulations also help researchers push past the limitations of space probes.

“Observations are measuring something that is real, but they’re limited. Parker can only be in one place at one time, it has a limited lifetime and it’s also very hard to run reproducible experiments on it,” Swisdak said. “Computations have complementary advantages in that you can set up a simulation based on what Parker is observing, but then you can tweak the parameters to see the bigger picture of what we think is happening.”

‘Things no one has seen’

There are still unsolved mysteries, including the exact mechanisms that produce switchbacks and drive the solar wind, but researchers hope that the Parker Solar Probe will continue to answer these and other important questions. The sun is currently experiencing more intense solar flares and coronal mass ejections than usual, which could yield new and interesting data on the mechanisms that energize particles in these explosive events.

This research also has wider relevance. Studying the solar wind can help scientists understand other winds throughout the universe, including the powerful winds produced by black holes and rapidly rotating stars called pulsars. Winds can even offer clues about the habitability of planets because of their ability to deflect harmful cosmic rays, which are forms of radiation.

“One of the reasons why the solar wind is important is because it protects planetary bodies from these very energetic particles that are bouncing around the galaxy,” Drake said. “If we didn't have that solar wind protecting us, it's not totally clear whether the Earth would have been a habitable environment.”

As the spacecraft prepares for its December descent into the sun, the UMD team is eager to see what the new observations will reveal.

“One of the nice things about being involved with this mission is that it’s a chance to make observations of things that no one has seen before. It lets you go into a new regime of space and say, ‘Alright, we thought things would look this way, and inevitably they don't,’” Swisdak said. “The ability to get close enough to the sun to see where the solar wind starts and where coronal mass ejections begin—and being able to take direct measurements of those phenomena—is really exciting.”

Leaning into Lidar

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Category: Department News

Published: Wednesday, September 11 2024 05:24

Swarnav Banik’s (Ph.D. ’21, physics) parents were visiting from India when they saw a strange-looking car on a San Francisco street that stopped them in their tracks.

“They asked what it was, and I said, ‘That’s a Waymo car. It has no driver in it. It drives itself.’ And they were so surprised,” Banik recalled. “They kept looking at the Waymo and taking pictures of it, they were so excited. And I said, ‘Yes, this technology is indeed exciting. Until a few years ago, we used to think of this as some future technology—now this is what I do.”Swarnav Banik

And what Banik does might just be the future of transportation. Since 2022, he’s been working on sensing technology for the next generation of autonomous vehicles.  He first worked as a senior photonics engineer at Aurora Innovation, a company that’s developing self-driving systems for semitrucks and other commercial vehicles; now he’s at Aeva, a Silicon Valley firm developing sensing and perception tools for driverless cars and industrial automation. 

In his work, Banik develops next-generation sensors that use lidar—light detection and ranging —technology to help autonomous vehicles “see” objects on the road ahead and safely avoid them.

“A typical autonomous vehicle has three kinds of sensors—a radar, a camera and a lidar,” Banik explained. “I have been working on frequency-modulated continuous wave lidar (FMCW), which has several advantages over the more commonly used time-of-flight lidar. Unlike time-of-flight lidars, FMCW lidar detects both the position and velocity of obstacles. This is extremely useful for highway driving where maneuvering decisions need to be made quickly.”

For Banik, working with lidar technology means putting his physics skill set to work in a way he never expected.

“Lidar is an interesting application of lasers. It uses many of the optical spectroscopy principles that I used as an atomic physics grad student, but I never thought I’d be doing anything like this,” he reflected. “It just kind of happened and I’m happy about it. I really like what I’m doing.”

The path to physics

Growing up in Mumbai, India, Banik was a curious and enthusiastic student, especially when he started taking high school physics.

“I really loved physics. It felt very logical, and I had a lot of fun solving physics problems,” he said. “In a way, it was like applying mathematics to real-world problems, and I believe that’s what interested me.”

In 2009, Banik entered the Indian Institute of Technology Delhi as an engineering physics major. As a sophomore, he landed an internship developing mathematical models for a cosmic ray experiment at the Tata Institute of Fundamental Research in Mumbai. Then as a junior, he interned in the U.S. at Fermilab, near Chicago, where he tackled the challenges of avalanche silicon photodiodes that are used for detecting high-energy particles.

“The idea was that these photodiodes would eventually be used in the Large Hadron Collider particle accelerator, and I was involved in the development of the photodiodes,” Banik explained. “I wasn’t married to particle physics back then, but I enjoyed designing engineering solutions from first principles: I learned how to break complex problems into smaller pieces and tackle them one by one, and I really appreciated that.”

After earning his undergraduate degree in India in 2013, Banik headed back to the U.S. to begin graduate school at the University of Maryland, where he hoped to find his niche in physics.

The thrill of research

“The Department of Physics at Maryland does very good research in almost every possible field of physics,” Banik explained. “I thought it would be a great place to get exposure and decide what I want to do.”

Banik connected with as many grad students and faculty members as he could, exploring everything from plasma physics and condensed matter theory to atomic, molecular, and optical physics and quantum information. Atomic physics won him over.

“The quantum computing applications that come out of atomic physics experiments were very exciting to me,” he recalled. “I saw grad students building atomic physics labs and I saw all the skills they had developed just by doing this research. I was impressed, and I wanted to be one of them.”

Working in UMD’s Joint Quantum Institute (JQI), Banik’s Ph.D. research focused on simulating cosmological inflation, such as the expansion of the universe, using a Bose-Einstein condensate.

"We start with sodium atoms and cool them to ultra-low temperatures of less than 100 nanokelvin using techniques like laser and evaporative cooling," Banik explained. "These atoms then form a quantum degenerate gas known as a Bose-Einstein condensate, and we use this as a platform to simulate phenomena like cosmological Hubble friction, which is impossible to study experimentally due to the massive scale of the universe."

For Banik, the thrill of successfully simulating Hubble friction—and working in the collaborative culture of JQI—energized and inspired him.

“I was working with Gretchen Campbell and Ian Spielman and they were really great,” he said. “The whole JQI ecosystem is so supportive. There are so many people you can rely on—the professors, the older grad students, the postdocs, we were constantly exchanging equipment and ideas.”

Lidar on a chip

After earning his Ph.D. in 2021, Banik charted a course toward industry.  And he saw a unique opportunity at Aurora. 

“Aurora makes autonomous freight-hauling trucks, and they were looking for someone with a physics mindset, someone who would approach solving problems from first principles,” Banik said. “Most of the people there were electrical engineers, and they needed someone who could think about next-gen architecture because they were building a newer version of the lidar sensor for fleets of vehicles.” 

Over the next two years, Banik and his colleagues met that challenge, developing and patenting a cost-saving, integrated, chip-based lidar sensor system.

“Making a lidar sensor is not that tricky—but the company wanted to mass-produce them,” Banik explained. “These chip-based sensors have the same capability as the traditional bulk optic sensors, but they could be produced more cheaply and in volume, meaning more lidars for more trucks.”

When Banik took a test ride in an autonomous semitruck equipped with lidar and other sensors (and a human “operator” on board as a backup), he got a whole new perspective on what driverless technology could do.

“It was fascinating—I was in this big self-driving truck, not a simulation, this was the real thing,” he recalled. “It was highway driving, there was heavy traffic, and the operator wasn’t doing anything. He was just sitting there while the truck drove itself. And then when we weren’t on the highway, there was a pedestrian who came all of a sudden, and the truck stopped for the pedestrian—just like that. The truck did exactly what it was supposed to do.”

Earlier this year, Banik moved on from Aurora to become a senior photonics module engineer at Aeva, where he continues to work with lidar and sensing modules, advancing autonomous driving technology that could be on the road in the not-too-distant future. 

“I feel that, if not today, then in a few years this technology is pretty much within the reach of the companies that are trying to do it,” Banik explained. “Aurora will be launching its self-driving trucks commercially by the end of this year, and I know of some other companies that are also doing that at the end of this year or early next year.”

There are still plenty of challenges on the road ahead, but Banik wouldn’t want to be anywhere else.

“It feels very good to be making an impact,” Banik said. “That’s the thing that motivates you and keeps you going. It’s pretty exciting.”

UMD Adds Undergraduate Physics Specializations in Biophysics and Applied Physics

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Category: Department News

Published: Wednesday, September 11 2024 05:24

The University of Maryland’s Department of Physics added two new specializations to its bachelor’s degree program this fall: biophysics and applied physics. These augment the existing primary physics major designed to prepare students for graduate studies in physics and the physics education specialization designed for students obtaining a teaching certificate through the College of Education.

“The American Institute of Physics and the American Physical Society have recommended that undergraduate physics programs be diversified to prepare students for a variety of career paths, including those that extend beyond graduate study in physics,” said Carter Hall, a professor and the associate chair of undergraduate education for the Department of Physics. “The biophysics and applied physics specializations were developed with these recommendations in mind and based upon input from our students and faculty.”

The biophysics specialization is designed for students interested in exploring the intersection of physics and biology. It serves those who aim to study biophysics in graduate school and those who seek a strong physics foundation while preparing for the MCAT and medical school. This specialization provides a comprehensive understanding of biological and physical systems, offering insights into the physical principles underlying biological processes. Students will gain valuable analytical and problem-solving skills, preparing them for advanced studies in biophysics or medical research or a career in the health sciences.

The applied physics specialization is designed for students who aim to enter the workforce in technical or scientific roles immediately after graduation or those who plan to pursue further studies in applied physics at the graduate level. This specialization focuses on practical applications of physics principles, equipping students with hands-on experience and problem-solving skills relevant to technology and research industries. By blending theoretical knowledge with practical training, the applied physics specialization prepares students to tackle real-world challenges and innovate in their chosen fields.

At UMD, the nearly 300 physics majors benefit from small class sizes, outstanding teachers and talented classmates. In addition, they are encouraged to participate in cutting-edge research with the department’s internationally recognized faculty members.

“Through participation in research projects, our students learn what it takes to conduct world-class scientific research,” Hall added. “Whether students decide to continue to study physics in graduate school or work in fields such as engineering, software development, law, business or education, a bachelor's degree in physics from Maryland provides an excellent foundation.”