Research, teaching and outreach in Physics at UW–Madison
Stas Boldyrev earns DOE funding to investigate turbulence in relativistic plasmas
This post was adapted from a U.S. Department of Energy announcement
The U.S. Department of Energy (DOE) announced August 23 that it is funding $9.96M to support research in basic plasma science and engineering as well as frontier plasma science experiments at several midscale DOE Collaborative Research Facilities (CRFs) across the nation. The funding will go to 20 universities — including to UW–Madison physics professor Stas Boldyrev — four private companies, and one national laboratory.
The funding will cover 30 awards aimed at supporting basic plasma science research as well as increasing research productivity and participation of U.S. researchers in the CRFs. The awards include three-year single investigator or small group projects as well as short-term, one-time seed funding projects.
“Basic and low temperature plasma science is an important area with many scientific and technological impacts,” said Jean Paul Allain, DOE Associate Director of Science for Fusion Energy Sciences. “The research funded under this FOA will enable the U.S research community to address many fundamental and technological science challenges helping to ensure continued American leadership in this critical field.”
Boldyrev’s award will investigate turbulence in relativistic plasmas, which is more poorly understood compared to its non-relativistic counterpart. Relativistic plasma turbulence exists in extremely hot and energetic natural systems, where plasma and/or particle flow rates approach the speed of light, and it is required to explain radiation spectra of space phenomena such as solar flares or galactic nuclei jets.
“This project intends to develop analytical, phenomenological, and numerical models of turbulent energy cascades, and describe how such turbulence interacts with magnetic fields,” Boldyrev says. “We will concentrate on universal statistical properties of relativistic turbulence, which makes the results applicable to various lab, space, and astronomy environments, where such turbulence is present.”
Vadim Roytershteyn of the Space Science Institute is a co-investigator.
Ke Fang, Ellen Zweibel earn Simons Foundation funding to study electrodynamics in extreme environments
Much of what we understand about fundamental physics is based on experiments done in the convenient “lab” of earth. But our planet is just one location, with its own relatively mild electromagnetic field. Do forces and energies work the same on earth as they do in all corners of the universe?
“It’s never guaranteed, as we see many theories break down at extreme environments,” says University of Wisconsin–Madison physics professor Ke Fang. “For example, a neutron star offers a magnetic field that is trillions of times stronger than on the Earth, and magnetars offer a field that is hundreds of trillions of time stronger. They are natural places to test many fundamental physics theories.”
SCEECS has six main research questions, three centered on understanding electrodynamics in neutron stars and three centered in black holes. Each question pairs at least one senior-level investigator with an early-career co-investigator. Zweibel serves as the lead investigator on her black hole question, and she is paired with Richard Anantua at UT-San Antonio. Fang is co-investigator on a neutron star question, and she is paired with Anatoly Spitkovsky at Princeton.
The neutron star “labs” that Fang is using are amongst the most dense stars in the universe — as small as 10 kilometers in diameter and with densities a million billion times that of water. High energy particles streaming from neutron stars are detectable on Earth, but they tend to be significantly altered by the time they make it here.
“How do those particles survive, in the sense that these extreme energy particles would interact with the surrounding media and produce secondary particles, and how do these interactions play a role in converting what you see on Earth?” Fang’s research asks. “There are also several major questions revealed by recent observations, such as extended TeV gamma-ray halos around neutron stars that are completely new phenomena. We would like to go from first principle physics to understand these phenomena.”
Zweibel’s research will use the extreme environment of spinning black holes, where the electromagnetic field has recently been identified as a major factor in accretion flows, or the movement of gases into the dense center. Her question asks how these accretion flows contribute to magnetizing black holes to form relativistic jets, or powerful emissions of radiation and high-energy particles.
“Accretion disks, their magnetic fields, and their magnetized jets are found throughout the Universe. They play essential roles in star formation, in the evolution of double, or binary stars, and in many other astrophysical settings,” Zweibel says. “The magnetized accretion disks surrounding black holes are by far the most extreme, and test our theories to the limits. Remarkably, we can circle back to laboratory plasma experiments, including some right here at UW, to study magnetized disks and jets as well.”
SCEECS is housed at Stanford University and includes researchers from 14 other US and international universities. UW–Madison and Columbia University are the only universities that have more than one investigator in the collaboration. Most of the funding will be used to support investigators, postdoctoral fellows, and graduate students.
The collaboration plans to host an in-person kick-off in October at Stanford with regular virtual meetings throughout the year. Those meetings will be a place where everyone involved in the research, including students, postdocs, and faculty, can provide updates and seek feedback. Larger-scale collaborations such as this one are nothing new to physicists, but those groups are almost always made up of experimental physicists.
“It’s rare for theorists to be in a larger collaboration because we’re usually working alone or in a small group,” Fang says. “This program is exciting because it collects leading theorists in the field from many different institutions and provides a network for us to collaborate with each other.”
The Simons Foundation’s mission is to advance the frontiers of research in mathematics and the basic sciences. The Foundation makes grants in four areas, including Mathematics and Physical Sciences, through which this collaboration is supported.
Physics researchers named part of $18M NSF materials research center
The Department of Physics is part of a six-year, $18 million grant awarded to the University of Wisconsin–Madison’s Materials Research Science and Engineering Center (MRSEC) by the National Science Foundation. The award creates a National User Facility for X-FAST (XUV Femtosecond Absorption Spectroscopy Tabletop), a powerful XUV laser developed in the department.
MRSEC brings together 30 affiliated faculty from across nine departments to answer fundamental questions in materials science. The two interdisciplinary research groups (IRGs) funded by the award include one on stability in supercooled glasses and a second on magnetics in strained membranes. Physics professor Uwe Bergmann is a co-lead on IRG-2 along with materials science and engineering professor and physics affiliate faculty member Jason Kawasaki.
“The idea of our IRG is to make thin membranes of materials and then by straining them in various ways, changing their properties,” Bergmann says. “And our specific role is that we are in charge of x-ray and ultrafast characterization.”
The membranes being studied are 20-50 nanometer thin, crystalline materials. Kawasaki developed a way to produce very strong strains, up to 10%, which disrupt the perfect crystal lattice when applied. Once the atoms are pulled out of equilibrium by the strain, the energy levels change a little, the bonding changes, and exotic new phases are introduced. Bergmann is part of the IRG-2 team whose role is to perform ultrafast characterization of these changes. His team then informs the simulations group, whose theoretical calculations inform Kawasaki’s sample synthesis group.
“This is the typical circle between making the sample, finding out its properties, and understanding the properties — and then feeding it back to make new samples,” Bergmann says. “We’re trying to characterize these properties so that we can tailor them, so we can control them with light.”
Being able to control the materials’ properties with fast, electromagnetic light pulses could be a boon to faster, more efficient computing and telecommunications, an important potential application of this work.
Bergmann’s role in MRSEC stems from his expertise in ultrafast x-ray spectroscopy. Since joining the department of physics in 2020, his group has developed and built the XUV transient absorption high harmonic generation instrument that will be used to characterize the changes in properties as a result of intense strain on the materials following ultrafast excitations. As part of the new funding, the X-FAST instrument is now a National User Facility, which provides access to researchers across the country. In addition, the new award is funding an upgrade that includes the terahertz (microwave to infrared) range for sample excitation, a range that team member and physics affiliate professor Jun Xiao has developed.
In addition to the two research thrusts, MRSEC also runs a robust outreach and education program as part of the funding.
MRSEC is one of 21 NSF-funded centers that conduct fundamental materials research, education and outreach at the nation’s leading research institutions. Paul Voyles, professor of materials science and engineering professor at UW–Madison, is MRSEC’s director.