{"id":60142,"date":"2025-07-12T17:45:13","date_gmt":"2025-07-12T17:45:13","guid":{"rendered":"https:\/\/www.europesays.com\/us\/60142\/"},"modified":"2025-07-12T17:45:13","modified_gmt":"2025-07-12T17:45:13","slug":"forgotten-for-nearly-a-century-a-lost-fusion-breakthrough-has-been-unearthed-and-physicists-just-recreated-it","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/60142\/","title":{"rendered":"Forgotten for Nearly a Century, a \u2018Lost\u2019 Fusion Breakthrough Has Been Unearthed\u2014and Physicists Just Recreated It"},"content":{"rendered":"

In 1938, an experiment by University of Michigan physicist Arthur Ruhlig led to a remarkable accidental discovery: the first recorded observation of deuterium-tritium (DT) fusion<\/a>.<\/p>\n

Ruhlig reported his discovery, detailing what he characterized at the time as a gamma-ray<\/a> experiment, in a letter to the editor published in Physical Review. Yet despite the experiment\u2019s groundbreaking nature, it was largely overlooked at the time, and became just another lost anecdote from the annals of science history.<\/p>\n

That is, until now. Thanks to the work of a team of Los Alamos scientists in collaboration with Duke University, Ruhlig\u2019s forgotten experiment from 1938 has been unearthed and replicated, revealing a lost discovery that nonetheless may have seeded a foundational concept in nuclear physics<\/a>.<\/p>\n

The discovery was made as part of a recent effort to trace the origin of DT fusion within the broader historical record of fusion. The experiment, now having been replicated using modern equipment and theoretical tools, allowed the Los Alamos team to confirm Ruhlig\u2019s primary observation that DT fusion occurs with high probability during interactions between deuterium and tritium nuclei\u2014an insight that now underpins both nuclear energy development<\/a> and national defense<\/a> technologies.<\/p>\n

A Forgotten Chapter in Fusion Research, Rediscovered<\/strong><\/p>\n

Today, the DT fusion reaction is of fundamental significance to fusion energy<\/a> technologies and plays a key role in modern nuclear deterrence<\/a>. Despite its crucial role in these modern applications, questions had long remained about where, precisely, the first evidence of this reaction had originated.<\/p>\n

Such questions had been on the minds of Los Alamos physicists Mark Chadwick and his colleague Mark Paris, who in 2023 were delving deeply into the early history of nuclear fusion. While revisiting known milestones like physicist Emil Konopinski\u2019s 1942 endorsement of DT fusion during a conference led by J. Robert Oppenheimer, a fundamental question arose: what led Konopinski to this precocious insight, especially one that foreshadowed DT fusion\u2019s potential uses involving a fission reaction weapon?<\/p>\n

Given that the Manhattan Project had only begun a few months beforehand, the choice in pursuing DT fusion would certainly have been fortuitous, especially if it had involved blind luck. However, Chadwick, Paris, and their colleagues soon determined that this likely hadn\u2019t been the case at all.<\/p>\n

Archive Searches Reveal a Forgotten Clue <\/strong><\/p>\n

A deeper dive into the mystery eventually led Chadwick to the National Security Research Center archives, where a late-night search uncovered a potential clue: a 1986 audio recording in which Konopinski credited his unique interest in DT fusion to \u201cpre-war\u201d research.<\/p>\n

\u201cI happened to know from pre-war work that the reaction of deuterium with hydrogen-3 produces much more energy and has a larger cross-section, so to speak,\u201d Konopinski can be heard<\/a> saying in the recording. \u201c[It] happens more easily than deuterium with deuterium.\u201d<\/p>\n<\/p>\n

\u201cI just happened to remember these things,\u201d Konapinski said. \u201cWe had these continuous conversations going on about rates of reaction, and I happened to know that this rate of reaction was a very good one. A very rapid one.\u201d<\/p>\n

Based on Konapinski\u2019s recollection involving \u201cpre-war work,\u201d Chadwick and his colleagues were able to track down Arthur Ruhlig\u2019s 1938 letter in Physical Review discussing his studies involving high-energy proton emissions while bombarding deuterium with deuterons.<\/p>\n

Ruhlig noted toward the end of his letter that the unusually energetic protons he observed were the result of secondary reactions involving tritium, formed in situ, and deuterium. He concluded that DT fusion \u201cmust be an exceedingly probable one,\u201d estimating its reaction rate based on the yields of protons.<\/p>\n

Lost, But Not Forgotten Physics <\/strong><\/p>\n

Ruhlig\u2019s work may have eventually been lost to history, but it had hardly been entirely forgotten. If anything, it seemingly left quite an impression on those who encountered it, which likely included Konopinski, who would recall reading about such \u201cpre-war work\u201d decades later.<\/p>\n

Building on the potential connection, Chadwick and his colleagues noted that both Konopinski and Ruhlig had been University of Michigan doctoral students in the 1930s, with overlapping mentors and connections to Hans Bethe, who was also mentioned in Ruhlig\u2019s paper regarding a private conversation the two men had where Ruhlig detailed what he had observed for his mentor. The DT reaction, Ruhlig concluded, \u201cmust be an exceedingly probable one.\u201d<\/p>\n

\"ArthurPhysicist Arthur Ruhlig in an undated photo from around the time of the publication of his letter in Physical Review (Photograph courtesy Vivian Ruhlig Lamb).
\nRecreating the 1938 Experiment<\/strong><\/p>\n

After tracing the likely origins of DT fusion\u2019s discovery back to its earliest pre-war roots, the next step for Chadwick and Paris was to recreate the original experiment from 1938. To achieve this, they approached Los Alamos Lab Director Thom Mason, who encouraged the team to recreate the experiment using modern physical hardware, rather than relying solely on simulations.<\/p>\n

This led to a collaboration with Duke University physicists at the Triangle Universities Nuclear Laboratory in North Carolina, where the team successfully reconstructed Ruhlig\u2019s setup using modern equipment and state-of-the-art precision.<\/p>\n

To achieve this, they utilized a 3.5-mm deuteron beam from the laboratory\u2019s Tandem accelerator, which was set to its lowest operating power. Next, the team directed the beam at a deuterated phosphoric acid target, similar to the one used in 1938. To mimic Ruhlig\u2019s original beam environment, a cobalt-alloy foil was used, along with a liquid scintillator neutron detector, which allowed the team to track the signature neutron emissions from secondary DT fusion reactions.<\/p>\n

\u201cIn contrast to fusion experiments such as in the inertial confinement fusion efforts at the National Ignition Facility, we were able to perform, for the first time at a low-energy nuclear physics facility, a DT fusion experiment as a secondary reaction following the initial deuterium-deuterium interaction which provides the tritium,\u201d said Werner Tornow, the Duke University lead physicist on the project.<\/p>\n

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\u201cThis work helps answer some intriguing questions about physics history, but it\u2019s also impactful in extending our ability to work with DT fusion in a considerably more challenging environment,\u201d Tornow said.<\/p>\n

Ruhlig\u2019s Findings Validated<\/strong><\/p>\n

Fundamentally, the team\u2019s work has confirmed that secondary DT reactions occur under such experimental conditions, although with one caveat: Ruhlig appeared to have overestimated the frequency of those reactions. Still, although his original 1938 letter lacked the detailed methodology to determine his precision, the modern replication of his experiment produced results that were a close match for Ruhlig\u2019s original estimates.<\/p>\n

\u201cRegardless of the inconsistency of Ruhlig\u2019s rate of fusion against our modern understanding, our replication leaves no doubt that he was at least qualitatively correct when he said that DT fusion was \u2018exceedingly probable,\u2019\u201d Chadwick said in a statement.<\/p>\n

\u201cRuhlig\u2019s accidental observation of DT fusion, together with subsequent Manhattan Project cross-section measurements, contributed to the peaceful application of DT fusion in tokamaks focused on energy projects,\u201d Chadwick added.<\/p>\n

\u201cI think we\u2019re all proud to lift Arthur Ruhlig up again out of history as an important contributor to ongoing, vital research,\u201d he said.<\/p>\n

Additionally, as a final fitting tribute to Ruhlig\u2019s pioneering work, the team published one of three new papers detailing the results of their recent work in Physical Review\u2014the same journal that first printed Ruhlig\u2019s 1938 letter 87 years ago.<\/p>\n

That paper<\/a>, \u201cModern version of the uncited 1938 experiment that first observed DT fusion,\u201d was published on June 20, 2025, along with two supplemental papers, \u201cA lost detail in D-T fusion history,\u201d appearing<\/a> in Physics Today, and \u201cEarly nuclear fusion cross-section advances 1934-1952 and comparison to today\u2019s ENDF data,\u201d published<\/a> in Fusion Science and Technology.<\/p>\n

Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at<\/strong>\u00a0<\/strong>micah@thedebrief.org<\/strong><\/a>. Follow his work at\u00a0<\/strong>micahhanks.com<\/strong><\/a>\u00a0and on X:\u00a0<\/strong>@MicahHanks<\/strong><\/a>.<\/strong><\/p>\n

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