Ryan Amberger, a dedicated Ph.D. candidate in the Department of Physics and Astronomy at Texas A&M University, has been honored with the prestigious 2025 Los Alamos National Laboratory-Texas A&M University System Graduate Fellowship. This accolade recognizes his innovative graduate research and his potential to confront significant challenges in nuclear science. The fellowship, amounting to $75,000, offers a vital platform of support for doctoral candidates aiming to conduct their dissertation research in collaboration with Los Alamos National Laboratory, including an invaluable in-residency experience at the lab itself.
This fellowship is a joint initiative by the Texas A&M University System and Los Alamos National Laboratory, with a highly selective process driven by a panel of experts who assess proposals based on academic excellence, technical merit, and the mentorship and training quality provided. Beyond the financial stipend, the fellowship covers educational expenses, travel, and essential research materials. Amberger’s selection highlights the scientific community’s anticipation of his contributions to the field of nuclear astrophysics and nuclear science more broadly.
Amberger’s research aligns closely with the work of Dr. Philip Adsley, a renowned physicist at Texas A&M’s Cyclotron Institute and recipient of the 2023 Department of Energy Early Career Research Award. Since joining Adsley’s group in June 2022, Amberger has immersed himself as a graduate research assistant, focusing on the intricate nuclear reactions occurring within stars—a subfield of nuclear astrophysics. Central to his work is the investigation of the “s-process,” or slow neutron capture process, which is critical to the production of roughly half of the universe’s elements heavier than iron.
The s-process is a sequence of nuclear reactions that occur in stellar interiors, during which neutrons are slowly captured by atomic nuclei followed by beta decay, transforming an element into the next heavier element on the periodic table. Understanding the mechanisms and environmental conditions that drive this process is vital to explaining the cosmic abundance of various elements. Amberger’s efforts specifically target how neutron availability and neutron-nucleus interaction probabilities influence the s-process pathway.
Fundamentally, the s-process hinges on two unknown factors: the quantity of neutrons available for capture and the neutron capture cross section, or likelihood that neutrons collide and interact with specific nuclei. Amberger’s current research endeavors are primarily focused on quantifying neutron production and availability during these stellar reactions. He elaborates that neutron capture, followed by beta decay, incrementally builds heavier elements by increasing the atomic number—this slow progression defines the s-process.
In his experimental focus, Amberger and Adsley have concentrated on particular nuclear reactions involving isotopes neon-22 (Ne-22) and magnesium-26 (Mg-26), alongside alpha particles. These two reactions yield different outputs: one pathway emits a neutron, while the other results in gamma radiation. This dichotomy is traced back to differences in their decay rates, which Amberger seeks to understand more clearly by examining the byproducts of a third related reaction. A better grasp of the branching ratio—how often Mg-26 decays via neutron emission versus gamma radiation—will enhance the understanding of neutron populations in stellar environments.
To address the second primary uncertainty—the neutron capture cross section—Amberger plans to collaborate with scientists at the Los Alamos Neutron Science Center (LANSCE), a cutting-edge facility equipped with one of the nation’s most powerful linear accelerators. Among LANSCE’s advanced instruments is DICER (Device for Indirect Capture Experiments on Radionuclides), designed to facilitate detailed studies of neutron-induced reactions. Amberger’s proposal, titled “Neutron-induced reactions; neutrons for s-process,” outlines the use of DICER to measure neutron capture probabilities with unprecedented precision.
During his planned residency at Los Alamos from April 2025 to March 2026, Amberger will work closely with Thanos Stamatopoulos, the DICER instrument scientist and nuclear physicist at Los Alamos. The experimental methodology involves directing a neutron beam of varying energies onto a target and measuring the neutrons that are not captured by the material using a detector positioned behind the target. By comparing the incident neutron flux to the detected un-captured neutrons, the neutron capture cross section for the target nuclei can be accurately determined, shedding light on the likelihood of neutron absorption relevant to the s-process.
Amberger’s scientific journey began in Benbrook, Texas, and he holds a dual Bachelor of Science degree in mathematics and physics from the University of Texas at Arlington. He joined Texas A&M’s Physics Department in the fall of 2021 and quickly integrated into the challenging and multifaceted realm of nuclear science under Dr. Adsley’s mentorship. His training encompasses diverse experimental techniques, from designing and fabricating specialized targets to operating complex detector systems essential for nuclear astrophysics research.
Dr. Philip Adsley emphasizes the versatile skill set Amberger brings to the laboratory, noting that nuclear science demands expertise across a broad range of experimental platforms. Amberger’s upcoming experience at Los Alamos will expand his experimental toolkit, particularly in neutron scattering techniques not available at the Cyclotron Institute. These advanced capabilities have broad implications across several domains, including nuclear safety, national security, and medical isotope production, aside from their astrophysical importance.
The fellowship signifies not just recognition for Amberger’s past academic and technical accomplishments but also a critical investment in the development of future leaders in nuclear science. Los Alamos National Laboratory is a hub for multidisciplinary research integral to national security, managed by Triad—a unique national security science organization jointly owned by Battelle Memorial Institute, the Texas A&M University System, and the Regents of the University of California under the Department of Energy’s National Nuclear Security Administration.
This opportunity places Amberger at the forefront of experimental nuclear astrophysics, with the potential to shed light on longstanding mysteries surrounding the cosmos’s elemental origins. By refining neutron capture measurements and advancing nuclear reaction models, his research will deepen our understanding of stellar nucleosynthesis, enhancing the scientific narrative of how the universe’s elemental makeup has evolved over billions of years.
His work marks an important step toward unraveling the fundamental processes that govern stellar interiors and element formation. Through precise experimental techniques and interdisciplinary collaboration, Amberger’s research not only unites physics and astrophysics but also aligns with applied fields that influence technology and society. As his work progresses, the nuclear science community anticipates transformative findings that may redefine current models of stellar nucleosynthesis and neutron behavior.
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Subject of Research: Nuclear Astrophysics, Neutron Capture, Stellar Nucleosynthesis
Article Title: Advancing Our Understanding of the s-Process: Ryan Amberger’s Nuclear Astrophysics Fellowship at Los Alamos
News Publication Date: Not specified
Web References:
– Texas A&M Department of Physics and Astronomy: https://artsci.tamu.edu/physics-astronomy/index.html
– Texas A&M University System: https://www.tamus.edu/
– Los Alamos National Laboratory: https://www.lanl.gov/
– Texas A&M Cyclotron Institute: https://cyclotron.tamu.edu/
– Los Alamos Neutron Science Center: https://lansce.lanl.gov/
– DICER Instrument Details: https://lansce.lanl.gov/facilities/lujan/instruments/fp-13/index.php
Image Credits: Argonne National Laboratory
Keywords
Science careers, Nuclear astrophysics, Neutrons, Stellar physics, Neutron capture, Experimental physics, Cyclotron Institute, Graduate research, Neutron detectors, Nuclear reactions, Isotopes, Nuclear science fellowship
