Bubble fusion is the non-technical name for a
nuclear fusion
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...
reaction hypothesized to occur inside extraordinarily large collapsing gas bubbles created in a liquid during
acoustic cavitation. The more technical name is sonofusion.
The term was coined in 2002 with the release of a report by
Rusi Taleyarkhan and collaborators that claimed to have observed evidence of sonofusion. The claim was quickly surrounded by controversy, including allegations ranging from experimental error to academic fraud. Subsequent publications claiming independent verification of sonofusion were also highly controversial.
Eventually, an investigation by
Purdue University
Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money ...
found that Taleyarkhan had engaged in falsification of independent verification, and had included a student as an author on a paper when he had not participated in the research. He was subsequently stripped of his professorship. One of his funders, the
Office of Naval Research
The Office of Naval Research (ONR) is an organization within the United States Department of the Navy responsible for the science and technology programs of the U.S. Navy and Marine Corps. Established by Congress in 1946, its mission is to plan ...
reviewed the report by Purdue and barred him from federal funding for 28 months.
Original experiments
![Sonofusion](https://upload.wikimedia.org/wikipedia/commons/0/09/Sonofusion.svg)
US patent 4,333,796, filed by Hugh Flynn in 1978, appears to be the earliest documented reference to a sonofusion-type reaction.
In the March 8, 2002 issue of the peer-reviewed journal ''
Science
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...
'',
Rusi P. Taleyarkhan and colleagues at the
Oak Ridge National Laboratory (ORNL) reported that acoustic cavitation experiments conducted with
deuterated
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through a reaction, metabolic pathway, or cell. The reactant is 'labeled' by replacing specific ...
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
() showed measurements of
tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
and
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
output consistent with the occurrence of fusion. The neutron emission was also reported to be coincident with the
sonoluminescence
Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound.
History
The sonoluminescence effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. Hermann Frenzel and ...
pulse, a key indicator that its source was fusion caused by the heat and pressure inside the collapsing bubbles.
Oak Ridge failed replication
The results were so startling, that the Oak Ridge National Laboratory asked two independent researchers, D. Shapira and M. J. Saltmarsh, to repeat the experiment using more sophisticated
neutron detection
Neutron detection is the effective detection of neutrons entering a well-positioned detector. There are two key aspects to effective neutron detection: hardware and software. Detection hardware refers to the kind of neutron detector used (the most ...
equipment. They reported that the neutron release was consistent with random coincidence.
A rebuttal by Taleyarkhan and the other authors of the original report argued that the Shapira and Saltmarsh report failed to account for significant differences in experimental setup, including over an inch of shielding between the neutron detector and the sonoluminescing acetone. According to Taleyarkhan ''et al.'', when properly considering those differences, the results were consistent with fusion.
As early as 2002, while experimental work was still in progress, Aaron Galonsky of Michigan State University, in a letter to the journal ''Science''
expressed doubts about the claim made by the Taleyarkhan team. In Galonsky's opinion, the observed neutrons were too high in energy to be from a
deuterium
Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
-deuterium (d-d) fusion reaction. In their response (published on the same page), the Taleyarkhan team provided detailed counter-arguments and concluded that the energy was "reasonably close" to that which was expected from a fusion reaction.
In February 2005 the documentary series ''
Horizon
The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...
'' commissioned two leading sonoluminescence researchers, Seth Putterman
[, Seth Putterman personal page.] and
Kenneth S. Suslick, to reproduce Taleyarkhan's work. Using similar acoustic parameters, deuterated acetone, similar bubble nucleation, and a much more sophisticated neutron detection device, the researchers could find no evidence of a fusion reaction.
Subsequent reports of replication
In 2004, new reports of bubble fusion were published by the Taleyarkhan group, claiming that the results of previous experiments had been replicated under more stringent experimental conditions.
These results differed from the original results in that fusion was claimed to occur over longer times than previously reported. The original report only claimed neutron emission from the initial bubble collapse following bubble nucleation, whereas this report claimed neutron emission many acoustic cycles later.
In July 2005, two of Taleyarkhan's students at
Purdue University
Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money ...
published evidence confirming the previous result. They used the same acoustic chamber, the same deuterated acetone fluid and a similar bubble nucleation system. In this report, no neutron-sonoluminescence coincidence was attempted.
An article in ''Nature'' raised issues about the validity of the research and complaints from his Purdue colleagues (see full analysis elsewhere in this page).
Charges of misconduct were raised, and Purdue University opened an investigation. It concluded in 2008 that Taleyarkhan's name should have appeared in the author list because of his deep involvement in many steps of the research, that he added one author that had not really participated in the paper just to overcome the criticism of one reviewer, and that this was part of an attempt of "an effort to falsify the scientific record by assertion of independent confirmation". The investigation did not address the validity of the experimental results.
In January 2006, a paper published in the journal ''
Physical Review Letters
''Physical Review Letters'' (''PRL''), established in 1958, is a peer-reviewed, scientific journal that is published 52 times per year by the American Physical Society. As also confirmed by various measurement standards, which include the ''Journa ...
'' by Taleyarkhan in collaboration with researchers from
Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute () (RPI) is a private research university in Troy, New York, with an additional campus in Hartford, Connecticut. A third campus in Groton, Connecticut closed in 2018. RPI was established in 1824 by Stephen Van ...
reported statistically significant evidence of fusion.
[
*
* "...The experiment was specifically designed to address a fundamental research question, not to make a device that would be capable of producing ]energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
, Block says...To verify the presence of fusion, the researchers used three independent neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
detectors and one gamma ray detector. All four detectors produced the same results: a statistically significant increase in the amount of nuclear emissions due to sonofusion when compared to background levels..."
In November 2006, in the midst of accusations concerning Taleyarkhan's research standards, two different scientists visited the meta-stable fluids research lab at Purdue University to measure neutrons, using Taleyarkhan's equipment. Dr. Edward R. Forringer and undergraduates David Robbins and Jonathan Martin of
LeTourneau University
LeTourneau University (LETU) is a private, interdenominational evangelical Christian university in Longview, Texas. Founded as LeTourneau Technical Institute in February 1946 by R. G. LeTourneau with his wife, Evelyn, the school initially educate ...
presented two papers at the
American Nuclear Society
The American Nuclear Society (ANS) is an international, not-for-profit organization of scientists, engineers, and industry professionals that promote the field of nuclear engineering and related disciplines.
ANS is composed of three communities ...
Winter Meeting that reported replication of neutron emission. Their experimental setup was similar to previous experiments in that it used a mixture of deuterated acetone,
deuterated benzene
Deuterated benzene (C6D6) is an isotopologue of benzene (C6H6) in which the hydrogen atom ("H") is replaced with deuterium (heavy hydrogen) isotope ("D").
Properties
The properties of deuterated benzene are very similar to those of normal benzene ...
,
tetrachloroethylene
Tetrachloroethylene, also known under the systematic name tetrachloroethene, or perchloroethylene, and many other names (and abbreviations such as "perc" or "PERC", and "PCE"), is a chlorocarbon with the formula Cl2C=CCl2 . It is a colorless liq ...
and
uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
. Notably, however, it operated without an external neutron source and used two types of
neutron detectors. They claimed a liquid
scintillation detector measured neutron levels at 8
standard deviation
In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while ...
s above the background level, while plastic detectors measured levels at 3.8 standard deviations above the background. When the same experiment was performed with non-deuterated
control
Control may refer to:
Basic meanings Economics and business
* Control (management), an element of management
* Control, an element of management accounting
* Comptroller (or controller), a senior financial officer in an organization
* Controllin ...
liquid, the measurements were within one standard deviation of background, indicating that the neutron production had only occurred during cavitation of the deuterated liquid.
["Bubble Fusion Confirmed by LETU Research" LeTourneau University News (www.letu.edu/opencms/opencms/events/Bubble_Fusion_Confirmed_by_LETU_Research.html) link inactive as of 2008-05-10][ (confirmation of presentation)] William M. Bugg, emeritus physics professor at the
University of Tennessee
The University of Tennessee (officially The University of Tennessee, Knoxville; or UT Knoxville; UTK; or UT) is a public land-grant research university in Knoxville, Tennessee. Founded in 1794, two years before Tennessee became the 16th state, ...
also traveled to Taleyarkhan's lab to repeat the experiment with his equipment. He also reported neutron emission, using plastic neutron detectors.
["Bubble Fusion Research Under Scrutiny", IEEE Spectrum, May 2006] Taleyarkhan claimed these visits counted as independent replications by experts, but Forringer later recognized that he was not an expert, and Bugg later said that Taleyarkhan performed the experiments and he had only watched.
''Nature'' report
In March 2006, ''
Nature
Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'' published a special report that called into question the validity of the results of the Purdue experiments.
The report quotes Brian Naranjo of the
University of California, Los Angeles
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
to the effect that neutron energy spectrum reported in the 2006 paper by Taleyarkhan, et al. was statistically inconsistent with neutrons produced by the proposed fusion reaction and instead highly consistent with neutrons produced by the radioactive decay of
Californium 252, an isotope commonly used as a laboratory
neutron source
A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear p ...
.
The response of Taleyarkhan ''et al.'', published in ''Physical Review Letters'', attempts to refute Naranjo's hypothesis as to the cause of the neutrons detected.
Tsoukalas, head of the School of Nuclear Engineering at Purdue, and several of his colleagues at Purdue, had convinced Taleyarkhan to move to Purdue and attempt a joint replication. In the 2006 ''Nature'' report they detail several troubling issues when trying to collaborate with Taleyarkhan. He reported positive results from certain set of raw data, but his colleagues had also examined that set and it only contained negative results. He never showed his colleagues the raw data corresponding to the positive results, despite several requests. He moved the equipment from a shared laboratory to his own laboratory, thus impeding review by his colleagues, and he didn't give any advance warning or explanation for the move. Taleyarkhan convinced his colleagues that they shouldn't publish a paper with their negative results. Taleyarkhan then insisted that the university's press release present his experiment as "peer-reviewed" and "independent", when the co-authors were working in his laboratory under his supervision, and his peers in the faculty were not allowed to review the data. In summary, Taleyarkhan's colleagues at Purdue said he placed obstacles to peer review of his experiments, and they had serious doubts about the validity of the research.
''Nature'' also revealed that the process of anonymous peer-review had not been followed, and that the journal ''Nuclear Engineering and Design'' was not independent from the authors. Taleyarkhan was co-editor of the journal, and the paper was only peer-reviewed by his co-editor, with Taleyarkhan's knowledge.
In 2002 Taleyarkhan filed a patent application on behalf of the United States Department of Energy, while working in Oak Ridge. ''Nature'' reported that the patent had been rejected in 2005 by the US Patent Office. The examiner called the experiment a variation of discredited
cold fusion
Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. It would contrast starkly with the "hot" fusion that is known to take place naturally within stars and artificially in hydrogen bombs and p ...
, found that there was "no reputable evidence of record to support any allegations or claims that the invention is capable of operating as indicated", and found that there was not enough detail for others to replicate the invention. The field of fusion suffered from many flawed claims, thus the examiner asked for additional proof that the radiation was generated from fusion and not from other sources. An appeal was not filed because the Department of Energy had dropped the claim in December 2005.
Doubts prompt investigation
Doubts among Purdue University's Nuclear Engineering faculty as to whether the positive results reported from sonofusion experiments conducted there were truthful prompted the university to initiate a review of the research, conducted by Purdue's Office of the Vice President for Research. In a March 9, 2006 article entitled "Evidence for bubble fusion called into question", ''Nature'' interviewed several of Taleyarkhan's colleagues who suspected something was amiss.
On February 7, 2007, the Purdue University administration determined that "the evidence does not support the allegations of research misconduct and that no further investigation of the allegations is warranted". Their report also stated that "vigorous, open debate of the scientific merits of this new technology is the most appropriate focus going forward."
In order to verify that the investigation was properly conducted,
House Representative Brad Miller requested full copies of its documents and reports by March 30, 2007.
His congressional report concluded that "Purdue deviated from its own procedures in investigating this case and did not conduct a thorough investigation"; in response, Purdue announced that it would re-open its investigation.
In June 2008, a multi-institutional team including Taleyarkhan published a paper in Nuclear Engineering and Design to "clear up misconceptions generated by a webposting of UCLA which served as the basis for the ''Nature'' article of March 2006", according to a press release.
On July 18, 2008, Purdue University announced that a committee with members from five institutions had investigated 12 allegations of research misconduct against Rusi Taleyarkhan. It concluded that two allegations were founded—that Taleyarkhan had claimed independent confirmation of his work when in reality the apparent confirmations were done by Taleyarkhan's former students and was not as "independent" as Taleyarkhan implied, and that Taleyarkhan had included a colleague's name on one of his papers who had not actually been involved in the research ("the sole apparent motivation for the addition of Mr. Bugg was a desire to overcome a reviewer's criticism", the report concluded).
Taleyarkhan's appeal of the report's conclusions was rejected. He said the two allegations of misconduct were trivial administrative issues and had nothing to do with the discovery of bubble nuclear fusion or the underlying science, and that "all allegations of fraud and fabrication have been dismissed as invalid and without merit — thereby supporting the underlying science and experimental data as being on solid ground".
A researcher questioned by the LA Times said that the report had not clarified whether bubble fusion was real or not, but that the low quality of the papers and the doubts cast by the report had destroyed Taleyarkhan's credibility with the scientific community.
[Purdue physicist found guilty of misconduct](_blank)
Los Angeles Times, July 19, 2008, Thomas H. Maugh II
On August 27, 2008 he was stripped of his named Arden Bement Jr. Professorship, and forbidden to be a thesis advisor for graduate students for at least the next 3 years.
Despite the findings against him, Taleyarkhan received a $185,000 grant from the
National Science Foundation
The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National I ...
between September 2008 and August 2009 to investigate bubble fusion. In 2009 the Office of Naval Research debarred him for 28 months, until September 2011, from receiving U.S. Federal Funding. During that period his name was listed in the 'Excluded Parties List' to prevent him from receiving further grants from any government agency.
See also
*
Cold fusion
Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. It would contrast starkly with the "hot" fusion that is known to take place naturally within stars and artificially in hydrogen bombs and p ...
*
List of energy topics
The following outline is provided as an overview of and topical guide to energy:
Energy – in physics, this is an indirectly observed quantity often understood as the ability of a physical system to do work on other physical systems. Since ...
*
Mechanism of sonoluminescence
References
Further reading
*
"Bubble Fusion Research Under Scrutiny" IEEE Spectrum
''IEEE Spectrum'' is a magazine edited by the Institute of Electrical and Electronics Engineers.
The first issue of ''IEEE Spectrum'' was published in January 1964 as a successor to ''Electrical Engineering''. The magazine contains peer-revie ...
, May 2006
*
"Sonofusion Experiment Produces Results Without External Neutron Source"''
PhysOrg.com
Phys.org is an online science, research and technology news aggregator offering briefs from press releases and reports from news agencies (a form of journalism sometimes pejoratively called churnalism). The website also produces its own science ...
'' January 27, 2006
"Bubble fusion: silencing the hype" ''Nature'' online, March 8, 2006 — Nature reveals serious doubts over reports of fusion in collapsing bubbles (subscription required)
"Fusion controversy rekindled"BBC News, March 5, 2002
*
"Fusion experiment disappoints"BBC News, July 2, 2002
*
Kenneth Chang, ''
The New York Times
''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...
'', February 27, 2007
{{Nuclear fusion reactors
Nuclear fusion
Fusion power
Cold fusion
Physical phenomena
Bubbles (physics)
de:Kalte Fusion#Sonofusion