image: Sang-Ho Kim, ORNL Spallation Neutron Source Accelerator Systems section head, advances the capabilities of high-power proton accelerators.
Credit: ORNL, U.S. Dept. of Energy
Researchers Sang-Ho Kim, An-Ping Li, Bronson Messer and Zac Ward of the Department of Energy’s Oak Ridge National Laboratory have been named Fellows of the American Physical Society in recognition of their outstanding impact in their respective fields.
APS Fellows receive peer acknowledgment for their distinguished achievements in physics through outstanding research, innovative applications, leadership and dedicated service to both physics and physics education. Each year, fewer than one-half of one percent of the Society’s members are elevated to APS Fellow status.
"Congratulations to our 2025 APS Fellows,” said ORNL Director Stephen Streiffer. “Being named an APS Fellow is one of the highest honors in physics, recognizing a career that is defined by the relentless pursuit of scientific discovery and a profound impact on the research community. To have four Fellows named in a single year is a notable achievement for the laboratory and speaks to the caliber of our scientific leaders.”
Sang-Ho Kim, section head of the Accelerator Systems Section at ORNL’s Spallation Neutron Source, was cited by the APS Division of the Physics of Beams “for visionary leadership and technical excellence in the development of the world’s first high-power hadron superconducting radio-frequency linear accelerator, mentoring the next generation of experts, and guiding the design and operation of related machines.”
Kim leads the teams responsible for the systems that make the SNS accelerator work — including the front end that prepares the particle beam, the normal-conducting and superconducting RF structures that speed it up, the radio-frequency systems that drive the accelerating fields, the modulators and power systems that supply energy, along with the cryogenic systems that make superconducting acceleration possible, and the vacuum systems that let the beam travel undisturbed. He also oversees the associated test facilities and R&D programs. Kim earned his doctorate in nuclear engineering from Seoul National University, where he specialized in accelerator and fusion devices. For the past two decades, he has played a key role in various aspects of SNS accelerator systems and related R&D efforts. In June 2025, the United States Particle Accelerator School awarded Kim its 2025 prize for achievement in accelerator science and technology.
An-Ping Li, leader of the Scanning Tunneling Microscopy group at the Center for Nanophase Materials Sciences (CNMS) was cited by the APS Topical Group on Instrument and Measurement Science “for pioneering contributions to multiprobe and spin-sensitive scanning tunneling microscopy that enable groundbreaking advances in understanding and control of atomic defects, interfaces, and precision synthesis.”
Li, who has led the Heterogeneities in Quantum Materials theme at CNMS for over a decade, has enriched his career through postdoctoral research at the Max Planck Institute in Germany and various industrial and academic positions. He progressed from ORNL research associate to distinguished research staff and was recognized as a Fellow of the American Vacuum Society in 2017. Li’s research employs techniques such as scanning tunneling microscopy, molecular beam epitaxy and controlled on-surface chemical reactions to probe electronic, magnetic and thermoelectric properties at the atomic scale. This contribution not only advances fundamental condensed matter physics but also opens new avenues toward energy and quantum information applications.
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Bronson Messer, a distinguished staff scientist and director of science for the Oak Ridge Leadership Computing Facility at ORNL, was cited by the APS Forum on Outreach and Engaging the Public “for conveying the excitement and universal impact of physics to students, teachers, professionals, and the public via talks, multimedia, laboratory tours, popular national events, and for direct outreach to underserved Appalachian students and teachers.”
In his role at the OLCF, Messer ensures that high-performance computing resources are deployed to drive breakthrough research. As a joint faculty professor in the Department of Physics and Astronomy at the University of Tennessee, Knoxville, he engages students in his research spanning neutrino transport, dense matter physics, turbulent nuclear combustion and performance modeling for advanced computing architectures. Messer’s contributions have also been recognized by awards such as the Oak Ridge Postdoctoral Association Mentor of the Year in 2020 and the R&D 100 Award for his leadership on the Flash-X software project in 2022.
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Zac Ward, who leads the Functional Hybrid Nanomaterials group at CNMS, was cited by the APS Forum on Physics and Society “for pioneering experimental materials physics approaches that directly connect fundamental research to critical societal challenges in energy, computing, and workforce development.”
An experimental condensed matter physicist, Ward leads research on the design, synthesis and advanced characterization of new materials that host electronic, magnetic and optical phenomena relevant to emerging microelectronics and quantum information applications. He contributes broadly to the community through leadership in professional societies, by serving in editorial and advisory roles, and by organizing technical meetings that bridge academia, industry and government. Committed to workforce development, Ward mentors students and early-career researchers while establishing outreach programs that cultivate the next generation of STEM professionals.
UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. — Scott Gibson