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Physicists recreate forgotten experiment observing fusion -- Los Alamos National Laboratory
https://phys.org/news/2025-06-physicists-recreate-forgotten-fusion.htmlA Los Alamos collaboration has replicated an important but largely forgotten physics experiment: the first deuterium-tritium (DT) fusion observation. As described in the article published in Physical Review C, the reworking of the previously unheralded experiment confirmed the role of University of Michigan physicist Arthur Ruhlig, whose 1938 experiment and observation of deuterium-tritium fusion likely planted the seed for a physics process that informs national security work and nuclear energy research to this day.
"As we've uncovered, Ruhlig's contribution was to hypothesize that DT fusion happens with very high probability when deuterium and tritium are brought sufficiently close together," said Mark Chadwick, associate Laboratory director for Science, Computation and Theory at Los Alamos. "Replicating his experiment helped us interpret his work and better understand his role, and what proved to be his essentially correct conclusions. The course of nuclear fuel physics has borne out the profound consequences of Arthur Ruhlig's clever insight."
The DT fusion reaction is central to enabling fusion technologies, whether as part of the nation's nuclear deterrence capabilities or in ongoing efforts to develop fusion for civilian energy. For instance, the deuterium-tritium reaction is at the center of efforts at the National Ignition Facility to harness fusion. Los Alamos physicists developed a theory about where the idea came from—Ruhlig—and then built an experiment that would confirm the import and accuracy of Ruhlig's suggestion.
Tracking down the origin of DT fusion
In 2023, Chadwick was working with colleagues, including theoretical physicist Mark Paris, on a compendium of the early history of the development of fusion. A reasonably well-known part of that history is the suggestion—at a meeting at future Manhattan Project-director J. Robert Oppenheimer's July 1942 Berkeley physics conference—by physicist Emil Konopinski that DT fusion, among numerous possible fusion reactions, would be particularly advantageous as a component of a fission-reaction weapon.
But Chadwick and his Los Alamos colleagues wondered: How did Konopinski arrive at this insight about DT fusion? Seizing on the most viable fusion process among several options this early in the program—the Manhattan Project had started in earnest only months before—certainly proved a fortuitous decision.
. . .
"As we've uncovered, Ruhlig's contribution was to hypothesize that DT fusion happens with very high probability when deuterium and tritium are brought sufficiently close together," said Mark Chadwick, associate Laboratory director for Science, Computation and Theory at Los Alamos. "Replicating his experiment helped us interpret his work and better understand his role, and what proved to be his essentially correct conclusions. The course of nuclear fuel physics has borne out the profound consequences of Arthur Ruhlig's clever insight."
The DT fusion reaction is central to enabling fusion technologies, whether as part of the nation's nuclear deterrence capabilities or in ongoing efforts to develop fusion for civilian energy. For instance, the deuterium-tritium reaction is at the center of efforts at the National Ignition Facility to harness fusion. Los Alamos physicists developed a theory about where the idea came from—Ruhlig—and then built an experiment that would confirm the import and accuracy of Ruhlig's suggestion.
Tracking down the origin of DT fusion
In 2023, Chadwick was working with colleagues, including theoretical physicist Mark Paris, on a compendium of the early history of the development of fusion. A reasonably well-known part of that history is the suggestion—at a meeting at future Manhattan Project-director J. Robert Oppenheimer's July 1942 Berkeley physics conference—by physicist Emil Konopinski that DT fusion, among numerous possible fusion reactions, would be particularly advantageous as a component of a fission-reaction weapon.
But Chadwick and his Los Alamos colleagues wondered: How did Konopinski arrive at this insight about DT fusion? Seizing on the most viable fusion process among several options this early in the program—the Manhattan Project had started in earnest only months before—certainly proved a fortuitous decision.
. . .