Cold fusion

This article is about the Fleischmann–Pons claims of nuclear fusion at room temperature using only a tabletop setup, and its related experiments. For the original use of the term 'cold fusion', see Muon-catalyzed fusion. For all other definitions, see Cold fusion (disambiguation).

Diagram of an open type calorimeter used at the New Hydrogen Energy Institute in Japan

Cold fusion refers to a proposed nuclear fusion process offered to explain a group of disputed experimental results first reported by electrochemists Martin Fleischmann and Stanley Pons. The field originates with reports of an experiment by Martin Fleischmann, then one of the world's leading electrochemists, and Stanley Pons in March 1989 where they reported anomalous heat production ("excess heat") of a magnitude they asserted would defy explanation except in terms of nuclear processes. They further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium. The small tabletop experiment involved electrolysis of heavy water on the surface of a palladium (Pd) electrode.

The media reported that nuclear fusion was happening inside the electrolysis cells, and these reports raised hopes of a cheap and abundant source of energy. Hopes fell when replication failures were weighed in view of several reasons cold fusion is not likely to occur, the discovery of possible sources of experimental error, and finally the discovery that Fleischmann and Pons had not actually detected nuclear reaction byproducts. By late 1989, most scientists considered cold fusion claims dead, and cold fusion subsequently gained a reputation as pathological science. In 1989, the majority of a review panel organized by the US Department of Energy (DOE) found that the evidence for the discovery of a new nuclear process was not persuasive enough to start a special program, but was "sympathetic toward modest support" for experiments "within the present funding system." A second DOE review, convened in 2004 to look at new research, reached conclusions similar to the first.

A small community of researchers continues to investigate cold fusion, claiming to replicate Fleischmann and Pons' results including nuclear reaction byproducts. Since cold fusion articles are rarely published in refereed scientific journals, the results do not receive as much scrutiny as more mainstream topics.

History

Before the Fleischmann–Pons experiment

The ability of palladium to absorb hydrogen was recognized as early as the nineteenth century by Thomas Graham. In the late 1920s, two Austrian born scientists, Friedrich Paneth and Kurt Peters, originally reported the transformation of hydrogen into helium by spontaneous nuclear catalysis when hydrogen was absorbed by finely divided palladium at room temperature. However, the authors later retracted that report, acknowledging that the helium they measured was due to background from the air.

In 1927, Swedish scientist J. Tandberg stated that he had fused hydrogen into helium in an electrolytic cell with palladium electrodes. On the basis of his work, he applied for a Swedish patent for "a method to produce helium and useful reaction energy". After deuterium was discovered in 1932, Tandberg continued his experiments with heavy water. Due to Paneth and Peters' retraction, Tandberg's patent application was eventually denied. His application for a patent in 1927 was denied as he could not explain the physical process.

The term "cold fusion" was used as early as 1956 in a New York Times article about Luis W. Alvarez' work on muon-catalyzed fusion. E. Paul Palmer of Brigham Young University also used the term "cold fusion" in 1986 in an investigation of "geo-fusion", the possible existence of fusion in a planetary core.

Fleischmann–Pons experiment

Events preceding announcement

Electrolysis cell schematic

Martin Fleischmann of the University of Southampton and Stanley Pons of the University of Utah hypothesized that the high compression ratio and mobility of deuterium that could be achieved within palladium metal using electrolysis might result in nuclear fusion. To investigate, they conducted electrolysis experiments using a palladium cathode and heavy water within a calorimeter, an insulated vessel designed to measure process heat. Current was applied continuously for many weeks, with the heavy water being renewed at intervals. Some deuterium was thought to be accumulating within the cathode, but most was allowed to bubble out of the cell, joining oxygen produced at the anode. For most of the time, the power input to the cell was equal to the calculated power leaving the cell within measurement accuracy, and the cell temperature was stable at around 30 °C. But then, at some point (in some of the experiments), the temperature rose suddenly to about 50 °C without changes in the input power. These high temperature phases would last for two days or more and would repeat several times in any given experiment once they had occurred. The calculated power leaving the cell was significantly higher than the input power during these high temperature phases. Eventually the high temperature phases would no longer occur within a particular cell.

In 1988, Fleischmann and Pons applied to the United States Department of Energy for funding towards a larger series of experiments. Up to this point they had been funding their experiments using a small device built with $100,000 out-of-pocket. The grant proposal was turned over for peer review, and one of the reviewers was Steven E. Jones of Brigham Young University. Jones had worked for some time on muon-catalyzed fusion, a known method of inducing nuclear fusion without high temperatures, and had written an article on the topic entitled "Cold nuclear fusion" that had been published in Scientific American in July 1987. Fleischmann and Pons and co-workers met with Jones and co-workers on occasion in Utah to share research and techniques. During this time, Fleischmann and Pons described their experiments as generating considerable "excess energy", in the sense that it could not be explained by chemical reactions alone. They felt that such a discovery could bear significant commercial value and would be entitled to patent protection. Jones, however, was measuring neutron flux, which was not of commercial interest. In order to avoid problems in the future, the teams appeared to agree to simultaneously publish their results, although their accounts of their March 6 meeting differ.

Announcement

In mid-March 1989, both research teams were ready to publish their findings, and Fleischmann and Jones had agreed to meet at an airport on March 24 to send their papers to Nature via FedEx. Fleischmann and Pons, however, pressured by the University of Utah which wanted to establish priority on the discovery, broke their apparent agreement, submitting their paper to the Journal of Electroanalytical Chemistry on March 11, and disclosing their work via a press release and press conference on March 23. Jones, upset, faxed in his paper to Nature after the press conference.

Fleischmann and Pons' announcement drew wide media attention. The 1986 discovery of high-temperature superconductivity had caused the scientific community to be more open to revelations of unexpected scientific results that could have huge economic repercussions and that could be replicated reliably even if they had not been predicted by established conjecture. Cold fusion was proposing the counterintuitive idea that a nuclear reaction could be caused to occur inside a chemically bound crystal structure. Many scientists were reminded of the Mössbauer effect, a process involving nuclear transitions in a solid. Its discovery 30 years earlier had also been unexpected, though it was quickly replicated and explained within the existing physics framework.

The announcement of a new clean source of energy came at a crucial time: everyone still remembered the 1973 oil crisis and the problems caused by oil dependence, anthropogenic global warming was starting to become notorious, the anti-nuclear movement was labeling nuclear power plants as dangerous and getting them closed, people had in mind the consequences of strip mining, acid rain and the greenhouse effect, and, to top it all, the Exxon Valdez oil spill happened the day after the announcement. In the press conference, Peterson, Fleischmann and Pons, backed by the solidity of their scientific credentials, repeatedly assured the journalists that cold fusion would solve all of these problems, and would provide a limitless inexhaustible source of clean energy, using only seawater as fuel. They said the results had been confirmed dozens of times and they had no doubts about them. in the accompanying press release Fleischmann was quoted saying: "What we have done is to open the door of a new research area, our indications are that the discovery will be relatively easy to make into a usable technology for generating heat and power, but continued work is needed, first, to further understand the science and secondly, to deter­mine its value to energy economics."

Response and fallout

Several laboratories in several countries attempted to repeat the experiments. A few initially reported success, but most failed to validate the results; Nathan Lewis, professor of Chemistry at the California Institute of Technology, led one of the most ambitious validation efforts, trying many variations on the experiment without success, while CERN physicist Douglas R. O. Morrison said that "essentially all" attempts in Western Europe had failed. Even those reporting success had difficulty reproducing Fleischmann and Pons' results. On April 10, a group at Texas A&M University published results of excess heat and later that day a group at the Georgia Institute of Technology announced neutron production—the strongest replication announced up to that point due to the detection of neutrons and the reputation of the lab. In 12 April Pons was acclaimed at a ACS meeting. But the Georgia Tech retracted their announcement in 13 April, explaining that their neutron detectors gave false positives when exposed to heat. Another attempt at independent replication, headed by Robert Huggins at Stanford University also reported early success with a light water control, saved cold fusion almost single-handedly and became the only scientific support for cold fusion in the 26 April US Congress hearings. But, when he finally presented his results, he reported an excess heat of only one celsius degree, a result that could be explained by chemical differences between heavy and light water in the presence of lithium, he had not tried to measure any radiation, and his research was derided by the scientists that saw it later. For the next six weeks, competing claims, counterclaims, and suggested explanations kept what was referred to as "cold fusion" or "fusion confusion" in the news.

In April 1989, Fleischmann and Pons published a "preliminary note" in the Journal of Electroanalytical Chemistry. This paper notably showed a gamma peak without its corresponding Compton edge, which indicated they had made a mistake in claiming evidence of fusion byproducts. Fleischmann and Pons replied to this critique, but the only thing left clear was that no gamma ray had been registered and that Fleischmann refused to recognize any mistakes in the data. A much longer paper published a year later went into details of calorimetry but did not include any nuclear measurements.

Nevertheless, Fleischmann and Pons and a number of other researchers who found positive results remained convinced of their findings. The University of Utah asked Congress to provide $25 million to pursue the research, and Pons was scheduled to meet with representatives of President Bush in early May.

In 30 April 1989, cold fusion was declared dead by the New York Times. The Times called it a circus the same day, and the Boston Herald attacked cold fusion the following day.

In 1 May 1989, the American Physical Society held a session on cold fusion in Baltimore, including many reports of experiments that failed to produce evidence of cold fusion. At the end of the session, eight of the nine leading speakers stated that they considered the initial Fleischmann and Pons claim dead with the ninth, Johann Rafelski, abstaining. Steven E. Koonin of Caltech called the Utah report a result of "the incompetence and delusion of Pons and Fleischmann" which was met with a standing ovation. Douglas R. O. Morrison, a physicist representing CERN, was the first to call the episode an example of pathological science.

In May 4, due to all this new criticism, the meetings with various representatives from Washington were canceled.

From 8 May only the A&M tritium results kept cold fusion afloat,

In July and November 1989, Nature published papers critical of cold fusion claims. Negative results were also published in several other scientific journals including Science, Physical Review Letters, and Physical Review C (nuclear physics).

In August 1989, in spite of this trend, the state of Utah invested $4.5 million to create the National Cold Fusion Institute.

The United States Department of Energy organized a special panel to review cold fusion theory and research. The panel issued its report in November 1989, concluding that results as of that date did not present convincing evidence that useful sources of energy would result from the phenomena attributed to cold fusion. The panel noted the large number of failures to replicate excess heat and the greater inconsistency of reports of nuclear reaction byproducts expected by established conjecture. Nuclear fusion of the type postulated would be inconsistent with current understanding and, if verified, would require established conjecture, perhaps even theory itself, to be extended in an unexpected way. The panel was against special funding for cold fusion research, but supported modest funding of "focused experiments within the general funding system." Cold fusion supporters continued to argue that the evidence for excess heat was strong, and in September 1990 the National Cold Fusion Institute listed 92 groups of researchers from 10 different countries that had reported corroborating evidence of excess heat. However no further DOE nor NSF funding resulted from the panel's recommendation. By this point, however, academic consensus had moved decidedly toward labeling cold fusion as a kind of "pathological science".

In early May 1990 one of the two A&M researchers, Kevin Wolf, acknowledged the possibility of spiking, but said that the most likely explanation was tritium contamination in the palladium electrodes or simply contamination due to sloppy work. In June 1990 an article in Science by science writer Gary Taubes destroyed the public credibility of the A&M tritium results when it accused its group leader John Bockris and one of his graduate students of spiking the cells with tritium. A A&M cold fusion review panel found that the tritium evidence was not convincing and that, while they couldn't rule out spiking, contamination and measurements problems were more likely explanations. and Bockris never got support from his faculty to resume his research.

In 30 June 1991 the National Cold Fusion Institute closed after it run out of funds; it found no excess heat, and its reports of tritium production were met with indifference.

Pons left his tenure, and both him and Fleischmann quietly left the United States. In 1991 they resumed research with Toyota's IMRA lab in France. Fleischmann left for England in 1995, and the contract with Pons was not renewed in 1998 after spending $40 million with no tangible results. Pons has made no public declarations since, and only Fleischmann continues giving talks and publishing papers.

In the ensuing years, several books came out critical of cold fusion research methods and the conduct of cold fusion researchers while only a few came in their defence. The scientific community continues to maintain a skeptical consensus regarding the subject due to the lack of experimental reproducibility and theoretical implausibility. New experimental claims are routinely dismissed or ignored by mainstream scientists and journals.

In April 2011 Dennis M. Bushnell, a senior NASA research manager, stated that LENR is a very "interesting and promising" new technology that is likely to advance "fairly rapidly."

Ongoing scientific work

Cold fusion apparatus at the Space and Naval Warfare Systems Center San Diego (2005)

A small but committed group of cold fusion researchers has continued to conduct experiments using Fleischmann and Pons electrolysis set-ups in spite of the rejection by the mainstream community. Often they prefer to name their field "Low Energy Nuclear Reaction" (LENR) or "Chemically Assisted Nuclear Reaction" (CANR), also "Lattice Assisted Nuclear Reaction" (LANR) and "Condensed Matter Nuclear Science" (CMNS), one of the reasons being to avoid the negative connotations associated with the original name. In 1992, Fleischmann and Pons relocated their laboratory to France under a grant from the Toyota Motor Corporation. The laboratory, IMRA, was closed in 1998 after spending £12 million on cold fusion work. Between 1992 and 1997, Japan's Ministry of International Trade and Industry sponsored a "New Hydrogen Energy Program" of US$20 million to research cold fusion. Announcing the end of the program in 1997, the director and one-time proponent of cold fusion research Hideo Ikegami stated "[w]e couldn't achieve what was first claimed in terms of cold fusion. (...) [w]e can't find any reason to propose more money for the coming year or for the future." Also in the 1990s, India stopped its research in cold fusion at the Bhabha Atomic Research Centre because of the lack of consensus among mainstream scientists and the US denunciation of the research.

In February 2002, the U.S. Navy revealed that researchers at their Space and Naval Warfare Systems Center in San Diego, California had been quietly studying cold fusion since 1989. They released a two-volume report, "Thermal and nuclear aspects of the Pd/D₂O system," with a plea for funding.

A 2008 report in Bangalore by Japanese researcher Yoshiaki Arata revived some interest for cold fusion research in India. Projects were commenced at the Chennai's Indian Institute of Technology, the Bhabha Atomic Research Centre and the Indira Gandhi Centre for Atomic Research. The National Institute of Advanced Studies has also recommended the Indian government to revive this research.

Claims of commercialization

Several entrepreneurs have claimed in the past that a working cold fusion energy generator is near to commercialization, yet so far no working machine is available on the market.

In January 2011 researchers from the University of Bologna, Andrea Rossi and Sergio Focardi, claimed to have successfully demonstrated commercially viable cold fusion. The apparatus, built by themselves, is called an Energy Catalyzer. In March 2011, two Swedish physicists evaluated the Energy Catalyzer, under the control of Rossi. As the target is immediate commercialization, the inventors say that details of the invention will not be published yet. The international patent application has been partially rejected because it seemed to "offend against the generally accepted laws of physics and established theories" and to overcome this problem the application should have contained either experimental evidence or a firm theoretical basis in current scientific theories. Due to this secrecy, the Swedish evaluators were not allowed to examine the inside of the reactor, and there is still uncertainty about the viability of the invention. Peer-reviewed journals have not published papers on this invention, leading Rossi to create his own online journal, Journal of Nuclear Physics.

Publications

The ISI identified cold fusion as the scientific topic with the largest number of published papers in 1989, of all scientific disciplines. The number of papers sharply declined after 1990 as scientists abandoned the controversy and journal editors declined to review new papers, and cold fusion fell off the ISI charts. The publication in mainstream journals has continued to decline but has not entirely stopped; this has been interpreted variously as the work of aging proponents who refuse to abandon a dying field, or as the normal publication rate in a small field that has found its natural niche. Researchers who got negative results abandoned the field, and mostly only believers kept publishing in the field. A 1993 paper in Physics Letters A was the last paper published by Fleischmann, and "one of the last reports to be formally challenged on technical grounds by a cold fusion skeptic".

The decline of publications in cold fusion has been described as a "failed information epidemics". The sudden surge of supporters until roughly 50% of scientists support the theory, followed by a decline until there is only a very small number of supporters, has been described as a characteristic of pathological science. The lack of a shared set of unifying concepts and techniques has prevented the creation of a dense network of collaboration in the field; researchers perform efforts in their own and in disparate directions, making more difficult the transition of cold fusion into "normal" science.

Cold fusion reports continued to be published in a small cluster of specialized journals like Journal of Electroanalytical Chemistry and Il Nuovo Cimento. Some papers also appeared in Journal of Physical Chemistry, Physics Letters A, International Journal of Hydrogen Energy, and a number of Japanese and Russian journals of physics, chemistry, and engineering. Since 2005, Naturwissenschaften has published cold fusion papers; in 2009, the journal named a cold fusion researcher to its editorial board.

The Nobel Laureate Julian Schwinger declared himself a supporter of cold fusion in the fall of 1989, after much of the response to the initial reports had turned negative. He tried to publish theoretical papers supporting the possibility of cold fusion in Physical Review Letters, but was deeply insulted by their rejection, and resigned from the American Physical Society (publisher of PRL) in protest.

The Journal of Fusion Technology (FT) established a permanent feature in 1990 for cold fusion papers, publishing over a dozen papers per year and giving a mainstream outlet for cold fusion researchers. When editor-in-chief George Miley retired in 2001, the journal stopped accepting new cold fusion papers. This has been cited as an example of the importance of sympathetic influential individuals to the publication of cold fusion papers in certain journals.

In the 1990s, the groups that continued to research cold fusion and their supporters established periodicals such as Fusion Facts, Cold Fusion Magazine, Infinite Energy Magazine and New Energy Times to cover developments in cold fusion and other radical claims in energy production that were being ignored in other venues. In 2007 they established their own peer-reviewed journal, the Journal of Condensed Matter Nuclear Science. The internet has also become a major means of communication and self-publication for CF researchers, allowing for revival of the research.

Conferences

Cold fusion researchers were for many years unable to get papers accepted at scientific meetings, prompting the creation of their own conferences. The first International Conference on Cold Fusion (ICCF) was held in 1990, and has met every 12 to 18 months since. By 1994, attendees offered no criticism to papers and presentations for fear of giving ammunition to external critics; according to physicist David Goldstein, this allowed for the proliferation of crackpots and prevented the normal processes of serious science. By 2002, critics and skeptics had stopped attending the conferences. With the founding in 2004 of the International Society for Condensed Matter Nuclear Science (ISCMNS), the conference was renamed the International Conference on Condensed Matter Nuclear Science—an example of the approach the cold fusion community has adopted in avoiding the term cold fusion and its negative connotations. Cold fusion research is often referenced by proponents as "low-energy nuclear reactions", or LENR, but according to sociologist Bart Simon the "cold fusion" label continues to serve a social function in creating a collective identity for the field.

Since 2006, the American Physical Society (APS) has included cold fusion sessions at their semiannual meetings, clarifying that this does not imply a softening of skepticism. Since 2007, the American Chemical Society (ACS) meetings also include "invited symposium(s)" on cold fusion. An ACS program chair said that without a proper forum the matter would never be discussed and, "with the world facing an energy crisis, it is worth exploring all possibilities."

On 22–25 March 2009, the American Chemical Society meeting included a four-day symposium in conjunction with the 20th anniversary of the announcement of cold fusion. Researchers working at the U.S. Navy's Space and Naval Warfare Systems Center (SPAWAR) reported detection of energetic neutrons using a heavy water electrolysis set-up and a CR-39 detector, a result previously published in Die Naturwissenschaften. The authors claim that these neutrons are indicative of nuclear reactions; without quantitative analysis of the number, energy, and timing of the neutrons and exclusion of other potential sources, this interpretation is unlikely to be accepted by the wider scientific community.

Further reviews and funding issues

Around 1998 the University of Utah had already dropped its research after spending over $1 million, and in the summer of 1997 Japan cut off research and closed its own lab after spending $20 million. Cold fusion researchers have complained there has been virtually no possibility of obtaining funding for cold fusion research in the United States, and no possibility of getting published. University researchers are unwilling to investigate cold fusion because they would be ridiculed by their colleagues and their professional careers would be at risk. In 1994, David Goodstein described cold fusion as:

"a pariah field, cast out by the scientific establishment. Between cold fusion and respectable science there is virtually no communication at all. Cold fusion papers are almost never published in refereed scientific journals, with the result that those works don't receive the normal critical scrutiny that science requires. On the other hand, because the Cold-Fusioners see themselves as a community under siege, there is little internal criticism. Experiments and theories tend to be accepted at face value, for fear of providing even more fuel for external critics, if anyone outside the group was bothering to listen. In these circumstances, crackpots flourish, making matters worse for those who believe that there is serious science going on here."

Particle physicist Frank Close has gone even further, stating that the problems that plagued the original cold fusion announcement are still happening (as of 2009): results from studies are still not being independently verified and inexplicable phenomena encountered are being labelled as "cold fusion" even if they are not, in order to attract the attention of journalists.

Cold fusion researchers themselves acknowledge that the flaws in the original announcement still cause their field to be marginalized and to suffer a chronic lack of funding, but a small number of old and new researchers have remained interested in investigating cold fusion.

In August 2003, responding to a April 2003 letter from MIT's Peter L. Hagelstein, the energy secretary Spencer Abraham ordered the DOE to organize a second review of the field. Cold fusion researchers were asked to present a review document of all the evidence since the 1989 review. The report was released in 2004. The reviewers were "split approximately evenly" on whether the experiments had produced energy in the form of heat, but they all complained about the lack of proof and the poor documentation of the experiments. In summary, the reviewers were not convinced and they didn't recommend a federal research program, but they did recommend individual well-thought studies. They summarized its conclusions thus:

While significant progress has been made in the sophistication of calorimeters since the review of this subject in 1989, the conclusions reached by the reviewers today are similar to those found in the 1989 review.

The current reviewers identified a number of basic science research areas that could be helpful in

resolving some of the controversies in the field, two of which were: 1) material science aspects of deuterated metals using modern characterization techniques, and 2) the study of particles reportedly emitted from deuterated foils using state-of-the-art apparatus and methods. The reviewers believed that this field would benefit from the peer-review processes associated with proposal submission to agencies and paper submission to archival journals.

— Report of the Review of Low Energy Nuclear Reactions, US Department of Energy, December 2004

The mainstream and popular scientific press presented this as a setback for cold fusion researchers, with headlines such as "cold fusion gets chilly encore", but cold fusion researchers placed a "rosier spin" on the report, noting that it also recommended specific areas where research could resolve the controversies in the field. In 2005, Physics Today reported that new reports of excess heat and other cold fusion effects were still no more convincing than 15 years previous.

Experiments and reported results

A cold fusion experiment usually includes:

• a metal, such as palladium or nickel, in bulk, thin films or powder;
• deuterium and/or hydrogen, in the form of water, gas or plasma; and
• an excitation in the form of electricity, magnetism, temperature, pressure, laser beam(s), or of acoustic waves.

Electrolysis cells can be either open cell or closed cell. In open cell systems, the electrolysis products, which are gaseous, are allowed to leave the cell. In closed cell experiments, the products are captured, for example by catalytically recombining the products in a separate part of the experimental system. These experiments generally strive for a steady state condition, with the electrolyte being replaced periodically. There are also "heat after death" experiments, where the evolution of heat is monitored after the electric current is turned off.

The most basic setup of a cold fusion cell consists of two electrodes submerged in a solution of palladium and heavy water. The electrodes are then connected to a power source to transmit electricity from one electrode to the other through the solution. Even when anomalous heat is reported, it can take weeks for it to begin to appear - this is known as the "loading time."

The Fleischmann and Pons early findings regarding helium, neutron radiation and tritium were later discredited. However, neutron radiation has been reported in cold fusion experiments at very low levels using different kinds of detectors, but levels were too low, close to background, and found too infrequently to provide useful information about possible nuclear processes.

Excess heat and energy production

An excess heat observation is based on an energy balance. Various sources of energy input and output are continuously measured. Under normal condition, the energy input can be matched to the energy output to within experimental error. In experiments such as those run by Fleischmann and Pons, a cell operating steadily at one temperature transitions to operating at a higher temperature with no increase in applied current. In other experiments, however, no excess heat was discovered, and, in fact, even the heat from successful experiments was unreliable and could not be replicated independently. If higher temperatures were real, and not experimental artifact, the energy balance would show an unaccounted term. In the Fleischmann and Pons experiments, the rate of inferred excess heat generation was in the range of 10-20% of total input. The high temperature condition would last for an extended period, making the total excess heat appear to be disproportionate to what might be obtained by ordinary chemical reaction of the material contained within the cell at any one time, though this could not be reliably replicated. Subsequent researchers who advocate for cold fusion report similar results. Nevertheless, as early as 1997, at least one research group was reporting that, with the proper procedure, "...5 samples out of 6 that had undergone the whole procedure showed very clear excess heat production."

One of the main criticisms of cold fusion was that the predictions from deuteron-deuteron fusion into helium should have resulted in the production of gamma rays which were not observed and have never been observed in any subsequent cold fusion experiments. Cold fusion researchers have since claimed to find X-rays, helium, neutrons and even nuclear transmutations. Some of them claim to have found them using only light water and nickel cathodes.

In 1993, after the initial discrediting, Fleischmann reported "heat-after-death" experiments: where excess heat was measured after the electric current supplied to the electrolytic cell was turned off. This type of report also became part of subsequent cold fusion claims.

Helium, heavy elements, and neutrons

"Triple tracks" in a CR-39 plastic radiation detector claimed as evidence for neutron emission from palladium deuteride.

Known instances of nuclear reactions, aside from producing energy, also produce nucleons and particles on ballistic trajectories which are readily observable. In support of their claim that nuclear reactions took place in their electrolytic cells, Fleischmann and Pons reported a neutron flux of 4,000 neutrons per second, as well as detections of tritium. The classical branching ratio for previously known fusion reactions that produce tritium would predict, with 1 watt of power, the production of 10¹² neutrons per second, levels that would have been fatal to the researchers. In 2009, Mosier-Boss et al. reported what they called the first scientific report of highly energetic neutrons, using CR-39 plastic radiation detectors, but the claims can not be validated without a quantitative analysis of neutrons.

Several medium and heavy elements like calcium, titanium, chromium, manganese, iron, cobalt, copper and zinc have been reported as detected by several researchers, like Tadahiko Mizuno or George Miley; these elemental transmutations are totally unexpected products of nuclear fusion processes and won't be believed by the scientific community until iron-clad reproducible proof has been presented. The report presented to the DOE in 2004 indicated that deuterium loaded foils could be used to detect fusion reaction products and, although the reviewers found the evidence presented to them as inconclusive, they indicated that those experiments didn't use state of the art techniques.

In response to skepticism about the lack of nuclear products, cold fusion researchers have tried to capture and measure nuclear products correlated with excess heat. Considerable attention has been given to measuring ⁴He production. However, the reported levels are very near to the background, so contamination by trace amounts of helium which are normally present in the air cannot be ruled out. The lack of detection of gamma radiation seen in the fusion of hydrogen or deuterium to ⁴He was seen as an explanation that the helium detections are due to experimental error. In the report presented to the DOE in 2004, the reviewers' opinion was divided on the evidence for ⁴He; with the most negative reviews concluding that although the amounts detected were above background levels, they were very close to them and therefore could be caused by contamination from air. The panel also expressed concerns about the poor-quality of the theoretical framework cold fusion proponents presented to account for the lack of gamma rays.

In other experiments where laser beams or deuteron beams were used as excitation the reaction rates of D-D fusion were shown to increase. In a paper from similar experiments the researchers conclude that their "findings also provide a first independent support for the claim in cold fusion ..."

Incompatibilities with conventional fusion

There are many reasons conventional fusion is an unlikely explanation for the experimental results described above.

Repulsion forces

Because nuclei are all positively charged, they strongly repel one another. Normally, in the absence of a catalyst such as a muon, very high kinetic energies are required to overcome this repulsion. Extrapolating from known rates at high energies down to energies available in cold fusion experiments, the rate for uncatalyzed fusion at room-temperature energy would be 50 orders of magnitude lower than needed to account for the reported excess heat.

Lack of expected reaction products

Conventional deuteron fusion is a two-step process, in which an unstable high energy intermediary is formed:

D + D → ⁴He^* + 24 MeV

High energy experiments have observed only three decay pathways for this excited-state nucleus, with the branching ratio showing the probability that any given intermediate will follow a particular pathway. The products formed via these decay pathways are:

⁴He^* → n + ³He + 3.3 MeV (ratio=50%)

⁴He^* → p + ³H + 4.0 MeV (ratio=50%)

⁴He^* → ⁴He + γ + 24 MeV (ratio=10⁻⁶)

Only about one in one million of the intermediaries decay along the third pathway, making its products comparatively rare when compared to the other paths. If one watt of nuclear power were produced from deuteron fusion consistent with known branching ratios, the resulting neutron and tritium (³H) production would be easily measured. Some researchers reported detecting ⁴He but without the expected neutron or tritium production; such a result would require branching ratios strongly favouring the third pathway, with the actual rates of the first two pathways lower by at least five orders of magnitude than observations from other experiments, directly contradicting mainstream-accepted branching probabilities. Those reports of ⁴He production did not include detection of gamma rays, which would require the third pathway to have been changed somehow so that gamma rays are no longer emitted. Proponents have proposed that the 24 MeV excess energy is transferred in the form of heat into the host metal lattice prior to the intermediary's decay. However, the known rate of the decay process together with the inter-atomic spacing in a metallic crystal makes such a transfer inexplicable in terms of conventional understandings of momentum and energy transfer, and even then we would see measurable levels of radiations.

Explanations

There is no accepted explanation for the alleged cold fusion experimental findings. Even amongst cold fusion supporters there is no consensus on the claims or what the underlying mechanism could be.

Explanations given by cold fusion opponents

There are many different objections to cold fusion:

• The results of the experiments can not be reproduced.
• The results are based on misinterpretation of the collected data.
• Calorimetry errors
• The results of the experiments are only small.
• The results are based on chemical processes, not nuclear processes.
• No control experiments were performed

The experiments can not be reproduced

Many research groups tried to reproduce the Fleischmann-Pons experiment, without success. Reproducibility is one of the main principles of the scientific method, and its lack led most physicists to believe that the few positive reports could be attributed to experimental error.

Misinterpretation of the collected data

Some research groups initially reported that they had replicated the Fleischmann and Pons results but later retracted their reports and offered an alternative explanation for their original positive results. A group at Georgia Tech found problems with their neutron detector, and Texas A&M discovered bad wiring in their thermometers. These retractions, combined with negative results from some famous laboratories, led most scientists to conclude that no positive result should be attributed to cold fusion.

Calorimetry errors

The calculation of excess heat in electrochemical cells involves certain assumptions. Errors in these assumptions have been offered as non-nuclear explanations for excess heat.

One assumption made by Fleischmann and Pons is that the efficiency of electrolysis is nearly 100%, meaning nearly all the electricity applied to the cell resulted in electrolysis of water, with negligible resistive heating and substantially all the electrolysis product leaving the cell unchanged. This assumption gives the amount of energy expended converting liquid D₂O into gaseous D₂ and O₂. The efficiency of electrolysis will be less than one if hydrogen and oxygen recombine to a significant extent within the calorimeter. Several researchers have described potential mechanisms by which this process could occur and thereby account for excess heat in electrolysis experiments.

Another assumption is that heat loss from the calorimeter maintains the same relationship with measured temperature as found when calibrating the calorimeter. This assumption ceases to be accurate if the temperature distribution within the cell becomes significantly altered from the condition under which calibration measurements were made. This can happen, for example, if fluid circulation within the cell becomes significantly altered. Recombination of hydrogen and oxygen within the calorimeter would also alter the heat distribution and invalidate the calibration.

John R. Huizenga who co-chaired the DOE 1989 panel stated simply a priori: "Furthermore, if the claimed excess heat exceeds that possible by other conventional processes (chemical, mechanical, etc.), one must conclude that an error has been made in measuring the excess heat."

The results are only small

The detected results are barely above background levels. The levels of 4He could have already been in the surrounding air instead of being created by any nuclear process. Detected neutrons and tritium were often barely above background level.

Chemical process not nuclear processes

Another objection offered the explanation that the heat was a result of a chemical process instead of a nuclear process. See also calorimetry errors

No control experiments were performed

Control experiments are part of the scientific method to prove that the measured effects do not happen by chance, but are direct results of the experiment. One of the points of criticism of Fleischmann and Pons was the lack of control experiments.

Explanations given by cold fusion proponents

Reports of reproductions

Some research groups reported successful reproductions. In July 1989 an Indian group of BARC (P. K. Iyengar and M. Srinivasan) and in October 1989 an team from USA (Bockris et al.) reported on creation of tritium. In December 1990 Professor Richard Oriani of Minnesota University reported excess heat

But even groups that reported successes found that some of their cells were producing the effect where other cells that were built exactly the same and used the same materials were not producing the effect.

Explanations why early reproduction attempts have failed were offered by D. Cravens and D. Letts in The Enabling Criteria Of Electrochemical Heat: Beyond Reasonable Doubt. in ICCF-14 International Conference on Condensed Matter Nuclear Science. 2008. Washington, DC.

Proposed theories

Researchers proposed alternative explanations for Fleischmann and Pons' results even before various other labs reported null results. Skeptics call cold fusion explanations ad hoc and lacking rigor, and state that they are used simply to disregard the negative experiments—symptoms of pathological science.

The initial cold fusion explanation was motivated by the high excess heat reported and by the insistence of the initial reviewer, Stephen E. Jones, that nuclear fusion might rationalize the data. Hydrogen and its isotopes can be absorbed in certain solids, including palladium hydride, at high densities. This creates a high partial pressure, greatly reducing the average separation of the hydrogen nuclei. Electron screening of the positive hydrogen nuclei by the negative electrons in the palladium lattice was also suggested to the 2004 DOE commission. It was proposed that a higher density of hydrogen nuclei inside the palladium and a lower potential barrier could raise the possibility of fusion at lower temperatures than expected from a simple application of Coulomb's law, but theoretical calculations show that these effects are too small to increase the rate of fusion by any detectable amount. The 2004 DOE commission found the theoretical explanations (Charge Element 2) to be the weakest part of cold fusion claims.

Cold fusion researchers do not agree on a single theoretical explanation or on a single experimental method that can produce replicable results. Attempts at theoretical justification have either been explicitly rejected by mainstream physicists or lack independent review.

Several novel scenarios and theories have been proposed to explain the positive experimental results, but they have been unable to convince mainstream scientists.

Patents

Although the details have not surfaced, it appears that the University of Utah forced the 23 March 1989 Fleischmann and Pons announcement in order to establish priority over the discovery and its patents before the joint publication with Jones. The Massachusetts Institute of Technology (MIT) announced on 12 April 1989 that it had applied for its own patents based on theoretical work of one of its researchers, Peter L. Hagelstein, who had been sending papers to journals from the 5th to the 12th of April. On 2 December 1993 the University of Utah licensed all its cold fusion patents to ENECO, a new company created to profit from cold fusion discoveries, and on March 1998 it said that it would no longer defend its patents.

The U.S. Patent and Trademark Office (USPTO) now rejects patents claiming cold fusion. Esther Kepplinger, the deputy commissioner of patents in 2004, said that this was done using the same argument as with perpetual motion machines: that they do not work. Patent applications are required to show that the invention is "useful", and this utility is dependent on the invention's ability to function. In general USPTO rejections on the sole grounds of the invention's being "inoperative" are rare, since such rejections need to demonstrate "proof of total incapacity", and cases where those rejections are upheld in a Federal Court are even rarer: nevertheless, in 2000, a rejection of a cold fusion patent was appealed in a Federal Court and it was upheld, in part on the grounds that the inventor was unable to establish the utility of the invention.

U.S. patents might still be granted when they are given a different name in order to disassociate it from cold fusion, although this strategy has had little success in the US: the very same claims that need to be patented can identify it with cold fusion, and most of these patents cannot avoid mentioning Fleischmann and Pons' research due to legal constraints, thus alerting the patent reviewer that it is a cold-fusion-related patent. David Voss said in 1999 that some patents that closely resemble cold fusion processes, and that use materials used in cold fusion, have been granted by the USPTO. The inventor of three such patents had his applications initially rejected when they were reviewed by experts in nuclear science; but then he rewrote the patents to focus more in the electrochemical parts so they would be reviewed instead by experts in electrochemistry, who approved them. When asked about the resemblance to cold fusion, the patent holder said that it used nuclear processes involving "new nuclear physics" unrelated to cold fusion. Melvin Miles was granted in 2004 a patent for a cold fusion device, and in 2007 he described his efforts to remove all instances of "cold fusion" from the patent description to avoid having it rejected outright.

At least one patent related to cold fusion has been granted by the European Patent Office.

A patent only legally prevents others from using or benefiting from one's invention. However, the general public perceives a patent as a stamp of approval, and a holder of three cold fusion patents said the patents were very valuable and had helped in getting investments.

See also

• Bubble fusion
• Energy Catalyzer/Rossi Reactor
• Faraday-efficiency effect
• List of experimental errors and frauds in physics
• List of topics characterized as pseudoscience
• Muon-catalyzed fusion
• Nuclear transmutation
• Pathological science
• Scientific misconduct

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External links

• Cold fusion at Curlie
• Britz, Dieter, Britz's cold nuclear fusion collection, retrieved 2011-07-29 {{citation}}: Unknown parameter |name= ignored (help). Lists books, papers and conferences about cold fusion; has graphs of publication rate over time.
• Two video press conferences on "Cold Fusion Rebirth" during the 237th National Meeting of the American Chemical Society, March 23, 2009, Session 1, Session 2.
• International Society for Condensed Matter Nuclear Science, organizes the ICCF conferences and publishes the Journal of Condensed Matter Nuclear Science.