Kyungseon Joo, a professor of physics, has been named Chair of the CLAS Collaboration, one of the largest international collaborations in nuclear physics. CLAS involves 50 institutions from 9 countries and has about 250 collaborators. The collaboration recently completed the upgrade of the CEBAF Large Acceptance Spectrometer (CLAS12) for operation at 11 GeV beam energy in Hall B at Jefferson National Laboratory in Newport News, VA, funded by the United States Department of Energy.
CLAS12 is based on a dual-magnet system with a superconducting torus magnet that provides a largely azimuthal field distribution that covers the forward polar angle range up to 35°, and a solenoid magnet and detector covering the polar angles from 35° to 125° with full azimuthal coverage. Trajectory reconstruction in the forward direction using drift chambers and in the central direction using a vertex tracker results in momentum resolutions of 1% and 3%, respectively. Cherenkov counters, time-of-flight scintillators, and electromagnetic calorimeters provide good particle identification. Fast triggering and high data-acquisition rates allow operation at a luminosity of 1035 cm−2s−1. These capabilities are being used in a broad scientific program to study the structure and interactions of nucleons, nuclei, and mesons, using polarized and unpolarized electron beams and targets for beam energies up to 11 GeV.
As Chair, Joo represents the collaboration in scientific, technical, and managerial concerns, while he closely works with the Lab management on scheduling experiments, organizing collaboration activities and expanding the reach of the collaboration. He currently focuses on collaboration-wide efforts to timely make first publications from CLAS12 with high impact science.
Could traveling into the past be part of our future? Quite possibly, says Ron Mallett, a UConn emeritus professor of physics who has studied the concept of time travel for decades. Earlier this month, he spoke with NBC Connecticut reporter Kevin Nathan about his life and work as a theoretical physicist, and discussed how time travel may be possible someday.
The UConn Physics Department is delighted to announce that our 2019 Distinguished Katzenstein Lecturer will be
Professor Dame Jocelyn Bell Burnell
Friday, November 8th, 2019
04:00 PM – 05:00 PM
Storrs Campus, Student Union Theater
Professor Dame Jocelyn Bell Burnell (pictured at left) is world-famous for her discovery of pulsars in 1967. Pulsars are a special type of neutron star, the rotating dense remnant of a massive star. Pulsars have highly magnetic surfaces and emit a beam of electromagnetic radiation along their poles. This beam of light moves into and out of our line-of-sight at quick, constant intervals, appearing as a regular “pulse” of light.
At the time of this discovery, Bell Burnell was a graduate student at the University of Cambridge and worked with her supervisor, Anthony Hewish, to construct the Interplanetary Scintillation Array to study another class of objects called quasars. In the course of her daily detailed analysis, she noticed a strange “pulsing” signal in her data. Jokingly dubbed “Little Green Man 1” (LGM-1), further data-taking and analysis revealed this signal to be rapidly spinning neutron star, eventually dubbed a “pulsar.”
Bell Burnell’s discovery is considered one of the most important achievements of the 20th century and was recognized by a Nobel Prize in Physics in 1974, awarded to her supervisor Anthony Hewish as well as to astronomer Martin Ryle. While many condemned the omission of Bell Burnell for the award, she rose above, graciously stating, “I believe it would demean Nobel Prizes if they were awarded to research students, except in very exceptional cases, and I do not believe this is one of them. Finally, I am not myself upset about it – after all, I am in good company, am I not!”
Professor Dame Jocelyn Bell Burnell has a highly distinguished career. Some notable highlights include serving as head of the Royal Astronomical Society and as the first female president of both the Institute of Physics and The Royal Society of Edinburgh. She was appointed Dame Commander of the Order of the British Empire for services to astronomy in 2007. Her story has been featured in a number of works, including the BBC Four’s Beautiful Minds and BBC Two’s Horizon. Bell Burnell is currently the chancellor of the University of Dundee in Scotland and a visiting professor of astrophysics at the University of Oxford.
In 2018 Bell Burnell was awarded a Special Breakthrough Prize in Fundamental Physics. Only four such prizes have been awarded, one to Stephen Hawking, one to the CERN scientists who discovered the Higgs Boson, and one to the LIGO team for their detection of gravitational waves. This award recognizes her discovery of pulsars and “a lifetime of inspiring scientific leadership.” In addition to her research accolades, her teaching, leadership, and work to lift up women and minorities in science is without parallel.
The Daily Campus published an article highlighting the research of Prof. Thomas Blum about Quantum Chromodynamics, a theory which describes the interactions between elementary particles. The development of this theory could help further understanding of the Standard Model of particle physics. The Standard Model is what physicists use to describe the fundamental building blocks of everything in the universe.
UConn Astrophysicist and observational astronomer Jonathan Trump was a recent guest on UConn 360, a podcast from the Storrs campus of the University of Connecticut. In this conversation, Jonathan tells about how attending a lecture as an undergraduate at Penn State captured his interest and changed the course of his professional career. Now Jonathan offers similar career-changing opportunities to UConn students, who just this year have applied for and obtained dedicated time for observations by the Hubble space telescope.
Physicists used to think that superconductivity – electricity flowing without resistance or loss – was an all or nothing phenomenon. But new evidence suggests that, at least in copper oxide superconductors, it’s not so clear cut.
Superconductors have amazing properties, and in principle could be used to build loss-free transmission lines and magnetic trains that levitate above superconducting tracks. But most superconductors only work at temperatures close to absolute zero. This temperature, called the critical temperature, is often only a few degrees Kelvin and requires liquid helium to stay that cold, making such superconductors too expensive for most commercial uses. A few superconductors, however, have a much warmer critical temperature, closer to the temperature of liquid nitrogen (77K), which is much more affordable.
Many of these higher-temperature superconductors are based on a two-dimensional form of copper oxide.
“If we understood why copper oxide is a superconductor at such high temperatures, we might be able to synthesize a better one” that works closer to room temperature (293K), says UConn physicist Ilya Sochnikov.
Sochnikov and his colleagues at Rice University, Brookhaven National Lab and Yale recently figured out part of that puzzle, and they report theirresults in the latest issue ofNature.
Their discovery was about how electrons behave in copper oxide superconductors. Electrons are the particles that carry electric charge through our everyday electronics. When a bunch of electrons flow in the same direction, we call that an electric current. In a normal electric circuit, say the wiring in your house, electrons bump and jostle each other and the surrounding atoms as they flow. That wastes some energy, which leaves the circuit as heat. Over long distances, that wasted energy can really add up: long-distance transmission lines in the U.S. lose on average 5% of their electricity before reaching a consumer, according to the Energy Information Administration.
But in a superconductor below its critical temperature, electrons behave totally differently. Instead of bumping and jostling, they pair up and move in sync with the other electrons in a kind of wave. If electrons in a normal current are a rushing, uncoordinated mob, electrons in a superconductor are like dancing couples, gliding across the floor like people in a ballroom. It’s this friction-free dance – coherent motion – of paired electrons that makes a superconductor what it is.
The electrons are so happy in pairs in a superconductor that it takes a certain amount of energy to pull them apart. Physicists can measure this energy with an experiment that measures how big a voltage is needed to tear an electron away from its partner. They call it the ‘gap energy’. The gap energy disappears when the temperature rises above the critical temperature and the superconductor changes into an ordinary material. Physicists assumed this is because the electron pairs have broken up. And in classic, low-temperature superconductors, it’s pretty clear that that’s what’s happening.
But Sochnikov and his colleagues wanted to know whether this was really true for copper oxides. Copper oxides behave a little differently than classic superconductors. Even when the temperature rises well above the critical level, the energy gap persists for a while, diminishing gradually. It could be a clue as to what makes them different.
The researchers set up a version of the gap energy experiment to test this. They made a precise sandwich of two slices of copper oxide superconductor separated by a thin filling of electrical insulator. Each slice was just a few nanometers thick. The researchers then applied a voltage between them. Electrons began to tunnel from one slice of copper oxide to the other, creating a current.
By measuring the noise in that current, the researchers found that a significant number of the electrons seemed to be tunneling in pairs instead of singly, even above the critical temperature. Only about half the electrons tunneled in pairs, and this number dropped as the temperature rose, but it tapered off only gradually.
“Somehow they survive,” Sochnikov says, “they don’t break fully.” He and his colleagues are still not sure whether the paired states are the origin of the high-temperature superconductivity, or whether it’s a competing state that the superconductor has to win out over as the temperature falls. But either way, their discovery puts a constraint on how high temperature superconductors happen.
“Our results have profound implications for basic condensed matter physics theory,” says co-author Ivan Bozovic, group leader of the Oxide Molecular Beam Epitaxy Group in the Condensed Matter Physics and Materials Science Division at the U.S. Department of Energy’s Brookhaven National Laboratory and professor of applied physics at Yale University. Sochnikov agrees.
“There’s a thousand theories about copper oxide superconductors. This work allows us to narrow it down to a much smaller pool. Essentially, our results say that any theory has to pass a qualifying exam of explaining the existence of the observed electron pairs,” Sochnikov says. He and his collaborators at UConn, Rice University, and Brookhaven National Laboratory plan to tackle the remaining open questions by designing even more precise materials and experiments.
The research work at UConn was funded by the State of Connecticut through laboratory startup funds.
Daniel McCarron, assistant professor of physics, the College of Liberal Arts and Sciences, will receive $645,000 over five years for his work on the development of techniques to trap large groups of molecules and cool them to temperatures near absolute zero. The possible control of molecules at this low temperature provides access to new research applications, such as quantum computers that can leverage the laws of quantum mechanics to outperform classical computers.
The NSF Faculty Early Career Development (CAREER) Program supports early-career faculty who have the potential to serve as academic role models in research and education, and to lead advances in the mission of their department or organization. Activities pursued by early-career faculty build a firm foundation for a lifetime of leadership in integrating education and research.
August 19, 2019 – Anna Zarra Aldrich ’20 (CLAS), Office of the Vice President for Research
When Carlos Trallero started his academic career in physics, he had no idea he would become a pioneer in a field of research that uses high-power lasers to investigate atomic and molecular physical phenomena.
Originally from Cuba, where there isn’t much funding for experimental research, Trallero began his academic career by studying theoretical physics. But as a senior graduate student at Stony Brook University, he got the chance to work in a lab doing experimental work and quickly recognized it was his true passion.
“I talked to a professor doing experimentation with ultra-fast lasers and I fell in love with it. And at first, I sucked at it — I was horrible,” says the professor of physics who is now working with four research grants funding separate investigations.
Trallero works with very short laser beams, with an emphasis onvery short. The lasers he uses can pulse with attosecond precision. As a comparison, there are as many attoseconds in one second as there have been seconds in the entire history of the universe since the Big Bang.
It takes light half an attosecond to cross the orbit of hydrogen, the smallest atom. When trying to study something that fast, scientists need the kind of precision the lasers Trallero can offer. The goal of this research is to gain a better understanding of how electrons, one of the fundamental atomic building blocks in the universe, move and react to light. By understanding the physics of electron movement, scientists could improve the design of technologies like superconductors.
“The dream is to be able to perform logistical operations like a computer at the attosecond level,” Trallero says. “It would really advance computational speeds. If you could make as many calculations in a second as there have been seconds in the history of the universe – that’s an astounding number.”
His lab is now working to break the attosecond barrier into the zeptosecond barrier which is 1,000 times faster than the attosecond.
While some of the potential applications of this research remain unknown since the field is still in its infancy, Trallero views the premise of his research as creating basic knowledge. He is investigating the atomic and molecular phenomena which determine so many things in our universe but about which we still know relatively little.
One project funded by the Department of Energy has Trallero looking at the properties of atoms and molecules in the quantum world by harnessing light waveforms at the attosecond time scale through interferometry. Interferometers provide precise measurements of molecules using two beams of light which interfere with each other. The images produced by this technology will allow Trallero to find out information about the rotational dynamics of molecules.
“In the quantum world, properties of atoms and molecules are not as simple as in the real world,” says Trallero.
Another of Trallero’s grants, from the U.S. Air Force Office of Scientific Research, involves creating an incredibly bright beam. Trallero’s lab is working on taking electrons out of nanoparticles and then sending them back in, which will produce a bright, energetic light. “The process to study these dynamics has never been executed in this manner,” Trallero says.
Trallero is also working on two grants from the U.S. Navy, including one that aims to develop infrared “body heat lasers.”
Through these grants, Trallero is developing a new class of laser which is only comparable to those found at large, multinational laser facilities like the European Light Infrastructure. Compared to the technology currently available to Trallero at UConn, this new class of laser will have almost 20 times more average power than the current laser.
Developing a laser of this caliber will be incredibly useful for studying phenomena that only occur a few times per shot of the laser in real time. The laser will enable researchers to probe the molecules with X-rays and ultraviolet rays to look at their structure and is being developed through a partnership with a Canadian company, Few-cycle, and a German company, Amphos. Researchers like Trallero are able to get advanced technology for a fraction of their retail value by doing research of interest for these companies, which are constantly trying to innovate in step with the science.
“We’re only paying a fraction of the price because the company is interested in showing they can develop this kind of technology,” Trallero says. “Showing they have the capacity and showcasing what we do with, and for, them helps them gain a customer base and it helps us make major advances in basic science at the same time.”
Trallero is also considering creating spin-off tech companies based on his university inventions with graduate students and postdocs. He has developed nanoparticle technology which can help transform molecules from a liquid to a gaseous state which could be beneficial for producing aerosols.
Trallero views physics as “the broadest science” since it has unique applications to math, engineering, chemistry and, even, biology. “I try to think about particular scientific questions in a different way than perhaps other people who have been working in this field for a long time do,” Trallero says. “Often we suffer from too much in-depth specialization.”
He wants to make use of the tools from every specialty he can, and he instills this same inclination in the students working in his lab.
“They don’t know what they’re going to face in the future and by having a broad skill set and a broad mindset they’ll be prepared for anything,” Trallero says. “You’re opening your mind to more possibilities.”
Amelia Henkel, graduating Double Major in Physics and Human Rights, and President of the Undergraduate Women in Physics Club, speaks on the CLAS website about her passion for physics and human rights, and how she mastered challenges in her remarkably interdisciplinary curriculum. “We really need to interact with other disciplines,” says Amelia, “because that’s when physics has the opportunity to make a real impact on the rest of the world.” Her broad research interests range from A to W: from Astronomy to Women’s, Gender, and Sexuality Studies. “Respecting and promoting human rights is a prerequisite to realizing our full potential as human beings,” says Amelia. Physics as a discipline has made progress to become more inclusive, but many groups remain minorities including women. In daily college life in physics departments female students still face “microaggressions and discriminatory practices” which are often unintended and unconscious but nonetheless damaging and frustrating. As the President of the Undergraduate Women in Physics Club, Amelia helped to organize “events that promote community cohesion and inform the students about the nature of some of the barriers that exist in physics and in STEM, while talking about how we can overcome them.” The recent department-wide event Women in Physics Colloquium organized by Amelia was thought provoking and well-received. The percentage of women earning a Bacheleor’s Degree in Physics from UConn, though slowly increasing and compatible with the national average of about 20% published by APS, is far away from where we wish to be. But the efforts of students like Amelia contribute to improving the situation. Many thanks to Amelia whose commitment helps to make our department better.
Read more about Amelia on the CLAS website. A short summary of her story is in UConn Today.