Cold fusion (sometimes referred to as low energy nuclear reaction (LENR) studies or condensed matter nuclear science^[1]) refers to a postulated nuclear fusion process of unknown mechanism offered to explain a group of disputed experimental results first reported by electrochemists Martin Fleischmann and Stanley Pons.

Cold fusion, under this definition, was only first announced on March 23, 1989 when Fleischmann and Pons reported producing nuclear fusion in a tabletop experiment involving electrolysis of heavy water on a palladium (Pd) electrode.^[2] They reported anomalous heat production ("excess heat") of a magnitude they asserted would defy explanation except in terms of nuclear processes.^[3] They further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium.^[4] These reports raised hopes of a cheap and abundant source of energy.^[5]

Enthusiasm turned to skepticism as replication failures were weighed in view of several theoretical reasons cold fusion should not be possible, the discovery of possible sources of experimental error, and finally the discovery that Fleischmann and Pons had not actually detected nuclear reaction byproducts.^[6] By late 1989, most scientists considered cold fusion claims dead,^[7] and cold fusion subsequently gained a reputation as pathological science.^[8] However, some researchers continue to investigate cold fusion and publish their findings at conferences, in books, and scientific journals.^[7][9][10]

There have been few mainstream reviews of the field since 1990. In 1989, the majority of a review panel organized by the US Department of Energy (DOE) had found that the evidence for the discovery of a new nuclear process was not persuasive. A second DOE review, convened in 2004 to look at new research, reached conclusions that were similar to those of the 1989 panel.^[11]

History

Early work

The ability of palladium to absorb hydrogen was recognized as early as the nineteenth century by Thomas Graham.^[12] In the late nineteen-twenties, 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.^[12][13]

In 1927, Swedish scientist J. Tandberg stated that he had fused hydrogen into helium in an electrolytic cell with palladium electrodes.^[12] 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.^[12]

The term "cold fusion" was coined by E. Paul Palmer of Brigham Young University in 1986 in an investigation of "geo-fusion", or the possible existence of fusion in a planetary core.^[14]

Fleischmann-Pons announcement

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.^[15] 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.^[15] 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.^[16] 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 (and 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.^[16]

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.^[17] The grant proposal was turned over for peer review, and one of the reviewers was Steven E. Jones of Brigham Young University.^[17] 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.^[18] 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.^[17] 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.^[19]

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.^[19] Fleischmann and Pons, however, broke their apparent agreement, submitting their paper to the Journal of Electroanalytical Chemistry on March 11, and disclosing their work via a press conference on March 23.^[17] Jones, upset, faxed in his paper to Nature after the press conference.^[19]

Reaction to the announcement

Fleischmann and Pons' announcement drew wide media attention.^[20]

Scores of laboratories in the United States and abroad attempted to repeat the experiments.^[21] A few reported success, many others failure.^[21] Even those reporting success had difficulty reproducing Fleischmann and Pons' results.^[22] One of the more prominent reports of success came from a group at the Georgia Institute of Technology, which observed neutron production.^[23] The Georgia Tech group later retracted their announcement.^[24] Another team, headed by Robert Huggins at Stanford University also reported early success,^[25] but this too was refuted.^[7] For weeks, competing claims, counterclaims and suggested explanations kept what was referred to as "cold fusion" or "fusion confusion" in the news.^[26]

In May 1989, the American Physical Society held a session on cold fusion, at which were heard 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 they considered the initial Fleischmann and Pons' claim dead.^[21]

In April 1989, Fleischmann and Pons published a "preliminary note" in the Journal of Electroanalytical Chemistry.^[15] 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.^[27][28] The preliminary note was followed up a year later with a much longer paper that went into details of calorimetry but did not include any nuclear measurements.^[18]

In July and November 1989, Nature published papers critical of cold fusion claims.^[29][30]

Nevertheless, Fleischmann and Pons and a number of other researchers who found positive results remained convinced of their findings.^[21] In August 1989, the state of Utah invested $4.5 million to create the National Cold Fusion Institute.^[31]

The United States Department of Energy organized a special panel to review cold fusion theory and research.^[32] 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 phenomena attributed to cold fusion.^[33] The panel noted the inconsistency of reports of excess heat and the greater inconsistency of reports of nuclear reaction byproducts. Nuclear fusion of the type postulated would be inconsistent with current understanding and would require the invention of an entirely new nuclear process. The panel was against special funding for cold fusion research, but supported modest funding of "focused experiments within the general funding system."^[34]

In the ensuing years, several books came out critical of cold fusion research methods and the conduct of cold fusion researchers.^[35]

Further developments

Cold fusion claims were, and still are, considered extraordinary.^[36] In view of the theoretical issues alone, most scientists would require extraordinarily conclusive data to be convinced that cold fusion has been discovered.^[37] After the fiasco following the Pons and Fleischmann announcement, most scientists became dismissive of new experimental claims.^[38]

Nevertheless, there were positive results that kept some researchers interested and got new researchers involved.^[39] In September 1990, Fritz Will, Director of the National Cold Fusion Institute, compiled a list of 92 groups of researchers from 10 different countries that had reported excess heat, ³H, ⁴He, neutrons or other nuclear effects.^[40]

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.^[41]

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, Hideo Ikegami stated "We couldn't achieve what was first claimed in terms of cold fusion." He added, "We can't find any reason to propose more money for the coming year or for the future."^[42]

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."^[43]

In some cases, cold fusion researchers contend that cold fusion research is being suppressed.^[44] They complained there was virtually no possibility of obtaining funding for cold fusion research in the United States, and no possibility of getting published.^[45] University researchers were unwilling to investigate cold fusion because they would be ridiculed by their colleagues.^[46] In a biography by Jagdish Mehra et al. it is mentioned that to the shock of most physicists, the Nobel Laureate Julian Schwinger declared himself a supporter of cold fusion and tried to publish a paper on it in Physical Review Letters; when it was roundly rejected, in a manner that he considered deeply insulting, he resigned from that body in protest.^[47]

To provide a forum for researchers to share their results, the first International Conference on Cold Fusion was held in 1990. The conference, recently renamed the International Conference on Condensed Matter Nuclear Science, is held every 12 to 18 months in various countries around the world. The periodicals Fusion Facts, Cold Fusion Magazine, Infinite Energy Magazine, and New Energy Times were established in the 1990s to cover developments in cold fusion and related new energy sciences. In 2004 The International Society for Condensed Matter Nuclear Science (ISCMNS) was formed "To promote the understanding, development and application of Condensed Matter Nuclear Science for the benefit of the public."

In the 1990s, India stopped its research in cold fusion due to the lack of consensus among mainstream scientists and the US denunciation of it.^[48]

In February 2002, the U.S. Navy revealed that its researchers had been quietly studying cold fusion continually since 1989. Researchers at their Space and Naval Warfare Systems Center in San Diego, California released a two-volume report, entitled "Thermal and nuclear aspects of the Pd/D₂O system," with a plea for proper funding.^[49]

In 2004, at the request of cold fusion advocates, the DOE organized a second review of the field. Cold fusion researchers presented a review document stating that the observation of excess heat has been reproduced, that it can be reproduced at will under the proper conditions, and that many of the reasons for failure to reproduce it have been discovered.^[50]

18 reviewers in total examined the written and oral testimony given by cold fusion researchers. On the question of excess heat, the reviewers' opinions ranged from "evidence of excess heat is compelling" to "there is no convincing evidence that excess power is produced when integrated over the life of an experiment". The report states the reviewers were split approximately evenly on this topic. On the question of evidence for nuclear fusion, the report states:

Two-thirds of the reviewers...did not feel the evidence was conclusive for low energy nuclear reactions, one found the evidence convincing, and the remainder indicated they were somewhat convinced. Many reviewers noted that poor experiment design, documentation, background control and other similar issues hampered the understanding and interpretation of the results presented.

On the question of further research, the report reads:^[51]

The nearly unanimous opinion of the reviewers was that funding agencies should entertain individual, well-designed proposals for experiments that address specific scientific issues relevant to the question of whether or not there is anomalous energy production in Pd/D systems, or whether or not D-D fusion reactions occur at energies on the order of a few eV. These proposals should meet accepted scientific standards, and undergo the rigors of peer review. No reviewer recommended a focused federally funded program for low energy nuclear reactions.

Thirteen papers were presented at the "Cold Fusion" session of the March 2006 American Physical Society (APS) meeting in Baltimore.^[52] In 2007, the American Chemical Society's (ACS) held an "invited symposium" on cold fusion and low-energy nuclear reactions.^[53] Cold fusion reports have been published in Naturwissenschaften, Japanese Journal of Applied Physics, European Physical Journal A, European Physical Journal C, International Journal of Hydrogen Energy, Journal of Solid State Phenomena, Journal of Electroanalytical Chemistry, and Journal of Fusion Energy.^[54]

Cold fusion researchers have described possible cold fusion mechanisms, but they have not received mainstream acceptance.^[55] Physics Today said, in 2005, that new reports of excess heat and other cold fusion effects were still no more convincing than 15 years ago.^[56] 20 years later, in 2009, cold fusion researchers complain that the flaws in the original announcement still cause the field to be marginalized and to suffer a chronic lack of funding.^[57] Frank Close claims that a problem plaguing the original announcement is still happening: results from studies are still not being independently verified, and that inexplicable phenomena encountered in the last twenty years are being labeled as "cold fusion" even if they aren't, in order to attract attention from journalists.^[57] A number of researchers keep researching and publishing in the field, working under the name of low-energy nuclear reactions, or LENR, in order to avoid the negative connotations of the "cold fusion" label.^[57][58][59]

Research in India started again in 2008 in several centers like the Bhabha Atomic Research Centre thanks to the pressure of influential Indian scientists; the National Institute of Advanced Studies has also recommended the Indian government to revive this research.^[48]

On 22–25 March 2009, the American Chemical Society held a four-day symposium on "New Energy Technology", in conjunction with the 20th anniversary of the announcement of cold fusion. At the conference, researchers with the U.S. Navy's Space and Naval Warfare Systems Center (SPAWAR) reported detection of energetic neutrons in a palladium-deuterium co-deposition cell using CR-39,^[60] a result previously published in Die Naturwissenschaften.^[61] Neutrons are indicative of nuclear reactions.^[62]

Experimental details

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.^[63]

Electrolysis cells can be either open cell or closed cell. In open cell systems, the electrolyis 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.

Excess heat observations

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.^[64] At the higher temperature, the energy balance shows an unaccounted term. In the Fleischmann and Pons experiments, the rate of 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 disproportionate to what might be obtained by ordinary chemical reaction of the material contained within the cell at any one time. These high temperature phases did not last indefinitely and did not occur in every experiment, but in those experiments where they did occur, they would usually reoccur several times.^[65][66] Many others have reported similar results.^{[67][68][69][70][71][72]}

A 2007 review determined that more than 10 groups world wide reported measurements of excess heat in 1/3 of their experiments using electrolysis of heavy water in open and/or closed electrochemical cells, or deuterium gas loading onto Pd powders under pressure. Most of the research groups reported occasionally seeing 50-200% excess heat for periods lasting hours or days.^[66]

In 1993, Fleischmann reported "heat-after-death" experiments: he observed the continuing generation of excess heat after the electric current supplied to the electrolytic cell was turned off.^[73] Similar observations have been reported by others as well.^[74][75]

Reports of nuclear products in association with excess heat

Considerable attention has been given to measuring ⁴He production.^[76] In 1999 Schaffer says that the levels detected were very near to background levels, that there is the possibility of contamination by trace amounts of helium which are normally present in the air, and that the lack of detection of Gamma radiation led most of the scientific community to regard the presence of ⁴He as the result of experimental error.^[77] In the report presented to the DOE in 2004, ⁴He was detected in five out of sixteen cases where electrolytic cells were producing excess heat.^[78] The reviewers' opinion was divided on the evidence for ⁴He; some points cited were that the amounts detected were above background levels but very close to them, that it could be caused by contamination from air, and there were serious concerns about the assumptions made in the theorical framework that tried to account for the lack of gamma rays.^[78]

In 1999 several heavy elements had been detected by other researchers, specially Tadahiko Mizuno in Japan, although the presence of these elements was so unexpected from the current understanding of these reactions that Schaffer said that it would require extraordinary evidence before the scientific community accepted it.^[79] 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 unconclusive, they indicated that those experiments didn't use state of the art techniques and it was a line of work that could give conclusive results on the matter.^[80].

Neutron radiation

Fleischmann and Pons reported a neutron flux of 4,000 neutrons per second, as well as tritium, while the classical branching ratio for previously known fusion reactions that produce tritium would predict, with 1 Watt of power, the production of 10^12 neutrons per second, levels that would have been fatal to the researchers.^[81]

The Fleischmann and Pons early findings regarding helium were later retracted^[82], and the findings regarding neutron radiation and tritium have been retracted or discredited.^{[citation needed]} 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.^[83][84] However, energetic neutrons were also reported in 2008 by Mosier-Boss et al, using CR-39 plastic radiation detectors.^[85]

Evidence for nuclear transmutations

There have been reports that small amounts of copper and other metals can appear within Pd electrodes used in cold fusion experiments.^[86] Iwamura et al. report transmuting Cs to Pr and Sr to Mo, with the mass number increasing by 8, and the atomic number by 4 in either case.^[87]. Cs or Sr was applied to the surface of a Pd complex consisting of a thin Pd layer, alternating CaO and Pd layers, and bulk Pd. Deuterium was diffused through this complex. The surface was analyzed periodically with X-ray photoelectron spectroscopy and at the end of the experiment with glow discharge mass spectrometry.^[87] Production of such heavy nuclei is so unexpected from current understanding of nuclear reactions that extraordinary experimental proof will be needed to convince the scientific community of these results.^[88]

Non-nuclear explanations for excess heat

The calculation of excess heat in electrochemical cells involves certain assumptions.^[89] Errors in these assumptions have been offered as non-nuclear explanations for excess heat.

One assumption made by Fleishmann and Pons is the efficiency of electrolysis is nearly 100%, meaning they assumed 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.^[90] This assumption gives the amount of energy expended converting liquid D₂O into gaseous D₂ and O₂.^[91]

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 electrolyis experiments.^[92][93][94]

Another assumption is that heat loss from the calorimeter maintains the same relationship with measured temperature as found when calibrating the calorimeter.^[95] 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.^[96] This can happen, for example, if fluid circulation within the cell becomes significantly altered.^[97][98] Recombination of hydrogen and oxygen within the calorimeter would also alter the heat distribution and invalidate the calibration.^{[94][99][100]}

Discussion

Lack of accepted explanation using conventional physics

Postulating cold fusion to explain experimental results raises at least three separate theoretical problems.^[101]

1.- The probability of reaction

Because nuclei are all positively charged, they strongly repel one another.^[102] Normally, in the absence of a catalyst such as a muon, very high kinetic energies are required to overcome this repulsion.^[103] Extrapolating from known rates at high energies, 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.^[104]

2.- The branching ratio

Fusion is a two-step process.^[105] In the case of deuterium fusion, the first step is combination to form a high energy intermediary:

D + D → ⁴He + 24 MeV

In high energy experiments, this intermediary has been observed to quickly decay through three pathways:^[106]

n + ³He + 3.3 MeV (50%)

p + ³H + 4.0 MeV (50%)

⁴He + γ + 24 MeV (10^-6)

The first two pathways are equally probable, while the third one happened very slowly when compared with the other two.^[107] If one watt of nuclear power were produced, the neutron and tritium production from the first two pathways would be easy to measure.^[108] Neutrons and tritium (³H) were not being detected at levels commensurate with claimed heat, while some researchers have detected ⁴He</ref>; to achieve this result the rates of the first two pathways would have to be at least five orders of magnitude lower than observed in other experiments^[109]

3.- Conversion of γ-rays to heat

The γ-rays of the ⁴He pathway are not observed.^[110]. It has been 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.^[111] However, the speed 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.^[112]

Proposed explanations

According to Storms (2007), no published theory has been able to meet all the requirements of basic physical principles, while adequately explaining the experimental results he considers established or otherwise worthy of theoretical consideration.^[113]

Experimental error

Many groups trying to replicate Fleischmann and Pons' results found alternative explanations for their original positive results, like problems in the neutron detector in the case of Georgia Tech or bad wiring in the thermometers at Texas A&M.Alexander Bird (1998). Routledge (ed.). Philosophy of Science: Alexander Bird (illustrated, reprint ed.). pp. 261–262. ISBN 1857285042. The replication effort in 1989 at Caltech found that apparent excess heat was caused by failure to stir the electrolyte; however, Fleischmann later responded that his original experiments had been adequately stirred by the bubbles of evolved deuterium gas, as shown by dye diffusion. Generally, positive cold fusion results, when not retracted, were considered to be explainable by undiscovered experimental error, and in some cases, these errors were discovered or reasonably postulated.^{[citation needed]}

Among those who continue to believe claims of Cold Fusion are not attributable to error, some possible theoretical interpretations of the experimental results have been proposed.^[114] As of 2002, according to Gregory Neil Derry, they were all ad hoc explanations with no coherent explanation for the results being given.^[114]

Source of energy not d-d fusion

A number of different possible fusion pathways, other than deuterium-deuterium fusion, have been proposed, but most of them produce too little energy per resulting helium nucleus to explain the experimentally inferred energy of 25±5 MeV/⁴He.^[115] However, Takahashi has proposed that four deuterons condense to make ⁸Be, which quickly decays to two alpha particles, each with 23.8 MeV.^[116]

Hydrino (Deuterino) theory

Mills (2006) has suggested that electrons can occupy energy levels lower than previously understood, but that under normal conditions, a barrier exists to prevent transitions to such a reduced energy state. It is postulated that some atoms with an appropriate available energy level can catalyze the transition of electrons to this state. If an electron has reached a sufficiently collapsed state, this electron may then shield two deuterons similarly to muon-catalyzed fusion, allowing the nuclei to approach and fuse, and the electron could then be emitted as a prompt beta particle, thus explaining the lack of gamma radiation and conserving momentum.^[117]

See also

• Bubble fusion
• List of energy topics
• New Energy Times, newsletter
• Infinite Energy, magazine

References

Bibliography

External links

• American Chemical Society, 273rd Annual Meeting, March 23, 2009, Press Conference on "Cold Fusion Rebirth." (video) Session 1, Session 2.
• The Return of Cold Fusion
• What If Cold Fusion Is Real?
• CBS 60 Minutes: Cold Fusion Is Hot Again (video) April 24, 2009