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

Cold fusion refers to nuclear fusion of atoms at conditions close to room temperature, in contrast to the conditions of well-understood fusion reactions such as those inside stars and high energy experiments. Interest in the field was dramatically increased on March 23, 1989 when Martin Fleischmann, then one of the world's leading electro-chemists,[1] and Stanley Pons reported that they had produced 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. They further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium.[3] These reports raised hopes of a cheap and abundant source of energy.[4]

Enthusiasm turned to skepticism as 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.[5] By late 1989, most scientists considered cold fusion claims dead,[6] and cold fusion subsequently gained a reputation as pathological science.[7] However, some researchers continue to investigate cold fusion,[6][8][9][10] and some have reported positive results at mainstream conferences and in peer-reviewed journals.[11] [12] Cold fusion research sometimes is referred to as low energy nuclear reaction (LENR) studies or condensed matter nuclear science,[13] in order to avoid negative connotations.[14][15]

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. There have been few mainstream reviews of the field since 1990. A second DOE review, convened in 2004 to look at new research, reached conclusions similar to the first, but with a smaller majority.[16]

Contents

History

Early work

The ability of palladium to absorb hydrogen was recognized as early as the nineteenth century by Thomas Graham.[17] 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.[17][18]

In 1927, Swedish scientist J. Tandberg stated that he had fused hydrogen into helium in an electrolytic cell with palladium electrodes.[17] 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.[17]

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.[19]

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.[20]

Fleischmann-Pons 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.[21 ] 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.[21 ] 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.[22] 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.[22]

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.[23] The grant proposal was turned over for peer review, and one of the reviewers was Steven E. Jones of Brigham Young University.[23] 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.[22] 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.[23] 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.[24]

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.[24] Fleischmann and Pons, however, pressured by the University of Utah which wanted to establish priority on the discovery,[25] 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.[23] Jones, upset, faxed in his paper to Nature after the press conference.[24]

Reaction to the announcement

Fleischmann and Pons' announcement drew wide media attention.[26] The recent discovery of high-temperature superconductivity in 1986 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 lacked a theoretical basis that explained them.[27] Cold fusion was proposing the counter-intuitive idea that a nuclear reaction could be affected by happening inside a crystal structure, and many scientists immediately thought of the Mössbauer effect, since it was an example of this happening, and its discovery 30 years earlier had also been unexpected and it had been quickly replicated and explained within the existing physics framework.[28]

Scores of laboratories in the United States and abroad 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.[29] Even those reporting success had difficulty reproducing Fleischmann and Pons' results.[30] One of the more prominent reports of success came from a group at the Georgia Institute of Technology, which observed neutron production.[31] The Georgia Tech group later retracted their announcement.[32] Another team, headed by Robert Huggins at Stanford University also reported early success,[33] but it was called into question by a colleague who reviewed his work.[6] For weeks, competing claims, counterclaims and suggested explanations kept what was referred to as "cold fusion" or "fusion confusion" in the news.[34]

In April 1989, Fleischmann and Pons published a "preliminary note" in the Journal of Electroanalytical Chemistry.[21 ] 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.[35][36] 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.[22]

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 with the ninth abstaining.[29] In July and November 1989, Nature published papers critical of cold fusion claims.[37][38] Negative results were also published in several scientific journals including Science, Physical Review Letters, and Physical Review C (nuclear physics).[39]

Nevertheless, Fleischmann and Pons and a number of other researchers who found positive results remained convinced of their findings.[29] In August 1989, the state of Utah invested $4.5 million to create the National Cold Fusion Institute.[40]

The United States Department of Energy organized a special panel to review cold fusion theory and research.[41]:39 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.[41]:36 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, if verified, would require theory 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."[41]:37

In the ensuing years, several books came out critical of cold fusion research methods and the conduct of cold fusion researchers.[42]

Further developments

Cold fusion claims were, and still are, considered extraordinary.[43] In view of the theoretical issues alone, most scientists would require extraordinarily conclusive data to be convinced that cold fusion has been discovered.[44] After the fiasco following the Pons and Fleischmann announcement, most scientists became dismissive of new experimental claims.[45]

Nevertheless, there were positive results that kept some researchers interested and got new researchers involved.[46] 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.[47]

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.[48]

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."[49]

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."[28]

Cold fusion researchers have complained there was virtually no possibility of obtaining funding for cold fusion research in the United States, and no possibility of getting published.[50] University researchers, it has been claimed, were unwilling to investigate cold fusion because they would be ridiculed by their colleagues.[51] 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; he was deeply insulted by the manner of its rejection, and was led to resign from that body in protest.[52]

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 because of the lack of consensus among mainstream scientists and the US denunciation of it.[53]

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.[54]

In 2004, at the request of cold fusion researchers, the DOE organized a second review of the field. These researchers were asked to present a review document of all the evidence since the 1989 review. Their review stated 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.[55]

18 reviewers in total examined the written and oral testimony given by cold fusion researchers. 9 of them were picked by the DOE for their backgrounds in theoretical nuclear physics, material science, and electrochemistry, and they were given a month to peer review the report and the supplementary material. Other 9 reviewers were picked from relevant fields, they examined the peer reviews made by the other nine reviewers, and then they assisted to six presentations of one hour each, given by six different research groups.[56]:1

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. The reviewers that didn't find the evidence compelling cited a series of issues including: measuring excess power in a short time versus measuring the total net energy of an experiment, the non-elimination of all effects that could explain excess heat, and the net excess power being so small in percentage that it could be caused by calibration of systematic effects. Most of the reviewers, from both sides of the split, said that "the effects are not repeatable, the magnitude of the effect has not increased in over a decade of work, and that many of the reported experiments were not well documented".[56]:3

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.[56]:4

On the question of further research, the report reads:

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.[56]:5

The 2004 report summarized its conclusions as being similar to those of the 1989 review despite the progress being made in calorimeters. It also recommended specific areas where research could resolve the controversies in the field, and said that the field would benefit from following peer-review processes.[56]

Thirteen papers were presented at the "Cold Fusion" session of the March 2006 American Physical Society (APS) meeting in Baltimore.[57] In 2007, the American Chemical Society's (ACS) held an "invited symposium" on cold fusion and low-energy nuclear reactions.[58] 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.[59]

In 2005, Physics Today stated that new reports of excess heat and other cold fusion effects were still no more convincing than 15 years ago.[60] 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.[14] 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.[14] A number of researchers keep researching and publishing in the field.[10][15] These researchers have tried to avoid the negative connotations of the "cold fusion" label by replacing with labels like, for example, "anomalous effects in deuterated materials", which are both more accurate and "safer" for presentation to people outside the cold fusion community.[15] The research currently appears under the name of low-energy nuclear reactions, or LENR.[14] According to Simon, one of the reasons because the "cold fusion" label is still in widespread use is because it serves a social function in creating a collective identity for the field.[15] In 2007 the interest in the field was growing again, as shown by the presence of cold fusion sessions at the national meeting of the ACS. An ACS program chair said that "with the world facing an energy crisis, it is worth exploring all possibilities."[61] The APS has also hosted sessions on cold fusion.[61]

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.[53] The interest in cold fusion in India had been rekindled earlier that year by a demonstration in Bangalore by Japanese researcher Yoshiaki Arata.[62]

"Triple tracks" in a CR-39 plastic radiation detector claimed as evidence for neutron emission from palladium deuteride, suggestive of a deuterium-tritium reaction

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 standard cold fusion cell design[63] using CR-39,[11] a result previously published in Die Naturwissenschaften.[64] The authors claim that these neutrons are indicative of nuclear reactions,[65] although some scientists indicated that a quantitative analysis would be necessary before the results are accepted by the scientific community, and that the neutrons could be caused by another nuclear mechanism than fusion.[64][66]

Patents

Although the details have not surfaced, it appears that the University of Utah forced the Fleischmann and Pons announcement in 23 March 1989 in order to establish priority over the discovery and its patents before the joint publication with Jones.[25] The Massachusetts Institute of Technology (MIT) announced in April 12, 1989 that it had applied for its own patents based on the theoretical work of one of it own researchers, Peter L. Hagelstein, who had been sending papers to journals from the 5th to the 12th of April.[67]

The U.S. Patent and Trademark Office (USPTO) now rejects patents claiming cold fusion.[68] 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.[68] Patent applications are required to show that the invention is "useful", and this utility is dependent upon the invention's ability to function.[69] In general rejections by the USPTO on the sole grounds of the invention being "inoperative" are rare, since such rejections need to demonstrate "proof of total incapacity",[69] 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.[69][70]

Researchers in the US can still obtain grants and patents by giving a different name to the research in order to disassociate it from cold fusion,[71] 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.[71] David Voss said in 1999 that some patents that very closely resemble cold fusion processes, and that use materials used in cold fusion, have been slipping by and being granted by the USPTO.[72] The holder of three such patents says that his applications were initially rejected when they were reviewed by experts in nuclear science, but that he managed to have a second application reviewed instead by experts in electrochemistry, who approved them.[72] 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.[72] Melvin Miles was granted in 2004 a patent for a cold fusion device, and he later described in 2007 his efforts to remove all instances of "cold fusion" from the patent description to avoid having it rejected outright.[73]

At least one patent related to cold fusion has been obtained in Europe.[74]

A patent only legally prevents others from using or benefiting from your invention. However, the general public perceives them 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.[72]

Experimental details

A cold fusion experiment usually includes:

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.[63]

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.[22] 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.[76] 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.[56]:3[77] Many others have reported similar results.[78][79][80][81][82][83]

A 2007 review determined that more than 10 groups worldwide 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.[77]

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.[84] Similar observations have been reported by others as well.[85][86]

Non-nuclear explanations for excess heat

The calculation of excess heat in electrochemical cells involves certain assumptions.[87] Errors in these assumptions have been offered as non-nuclear explanations for excess heat.

One assumption made by Fleischmann 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.[22] This assumption gives the amount of energy expended converting liquid D2O into gaseous D2 and O2.[88]

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. [89][90 ][91]

Another assumption is that heat loss from the calorimeter maintains the same relationship with measured temperature as found when calibrating the calorimeter.[22] 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.[92] This can happen, for example, if fluid circulation within the cell becomes significantly altered.[93][94] Recombination of hydrogen and oxygen within the calorimeter would also alter the heat distribution and invalidate the calibration.[91][95][96]

Reports of nuclear products in association with excess heat

Considerable attention has been given to measuring 4He production. [12] 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.[76] 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.[56]:3,4 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 theoretical framework that tried to account for the lack of gamma rays.[56]:3,4

In 1999 several heavy elements had been detected by other researchers, especially 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.[76] 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 and it was a line of work that could give conclusive results on the matter.[56]:3,4,5

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 1012 neutrons per second, levels that would have been fatal to the researchers.[97]

The Fleischmann and Pons early findings regarding helium, neutron radiation and tritium were later discredited.[98][99] 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.[100][101] In 2009, Mosier-Boss et al. reported what they called the first scientific report of highly energetic neutrons, using CR-39 plastic radiation detectors,[102][103] although some scientists say that the results will need a quantitative analysis in order to be accepted by the physics community.[64][66]

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.[104] 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.[105 ] 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.[105 ] 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.[76]

Discussion

Inconsistencies with conventional physics

There are at least three reasons that fusion is an unlikely explanation for the experimental results described above.[106]

Probability of reaction

Because nuclei are all positively charged, they strongly repel one another.[30] Normally, in the absence of a catalyst such as a muon, very high kinetic energies are required to overcome this repulsion.[107] 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.[108] [109]

Since the 1920s, it has been known that hydrogen and its isotopes can dissolve in certain solids at high densities so that their separation can be relatively small, and that electron charge inside metals can partially cancel the repulsion between nuclei. These facts suggest the possibility of higher cold fusion rates than those expected from a simple application of Coulomb's law. However, modern theoretical calculations show that the effects should be too small to cause significant fusion rates.[110] Supporters of cold fusion pointed to experiments where bombarding metals with deuteron beams seems to increase reaction rates, and suggested to the DOE commission in 2004 that electron screening could be one explanation for this enhanced reaction rate.[111][112]

Observed branching ratio

Deuteron fusion is a two-step process,[113] 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.[114] The products formed via these decay pathways are:

n + 3He + 3.3 MeV (50%)
p + 3H + 4.0 MeV (50%)
4He + γ + 24 MeV (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.[76] 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.[76] 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.[115] 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.[76]

Conversion of gamma rays to heat

The γ-rays of the 4He pathway are not observed.[76]. 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.[114] 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.[116]

Proposed explanations

Cold fusion researchers have described possible cold fusion mechanisms (e.g., electron shielding of the nuclear Coulomb barrier), but they have not received mainstream acceptance.[117] In 2002, Gregory Neil Derry described them as ad hoc explanations that didn't coherently explain the experimental results. [118]

Many groups trying to replicate Fleischmann and Pons' results have reported 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.[119] These reports, combined with negative results from some famous laboratories,[120] led most scientists to conclude that no positive result should be attributed to cold fusion, at least not on a significant scale.[121][122]

See also

References

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  2. ^ Voss 1999
  3. ^ Fleischmann & Pons 1989, p. 301 ("It is inconceivable that this [amount of heat] could be due to anything but nuclear processes... We realise that the results reported here raise more questions than they provide answers...")
  4. ^ Browne 1989, para. 1
  5. ^ Browne 1989, Close 1992, Huizenga 1993, Taubes 1993
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  10. ^ a b Randy 2009
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  13. ^ Biberian 2007, Hagelstein et al. 2004
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  16. ^ Choi 2005, Feder 2005, US DOE 2004
  17. ^ a b c d US DOE 1989, p. 7
  18. ^ Paneth and Peters 1926
  19. ^ Laurence 1956
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  22. ^ a b c d e f g Fleischmann et al. 1990
  23. ^ a b c d Crease & Samios 1989, p. V1
  24. ^ a b c Lewenstein 1994, p. 8
  25. ^ a b Shamoo 2003, p. 86, Simon 2002, pp. 28–36
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  31. ^ Broad 1989
  32. ^ Wilford 1989
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  35. ^ Tate 1989, p. 1
  36. ^ Platt 1998
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    • Miskelly, GM; Heben MJ; Kumar A; Penner RM; Sailor MJ; Lewis NL (1989), "Analysis of the Published Calorimetric Evidence for Electrochemical Fusion of Deuterium in Palladium", Science 246 (4931): 793–796, doi:10.1126/science.246.4931.793, PMID 17748706  
    • Aberdam, D; Avenier M; Bagieu G; Bouchez J; Cavaignac JF; Collot J et al. (1990), "Limits on neutron emission following deuterium absorption into palladium and titanium", Phys. Rev. Lett. 65 (10): 1196–1199, doi:10.1103/PhysRevLett.65.1196  
    • Price, PB; Barwick SW; Williams WT; Porter JD (1989), "Search for energetic-charged-particle emission from deuterated Ti and Pd foils", Phys. Rev. Lett. 63 (18): 1926, doi:10.1103/PhysRevLett.63.1926  
    • Roberts, DA; Becchetti FD; Ben-Jacob E; Garik P; Musser J; Orr B; Tarlé G et al. (1990), "Energy and flux limits of cold-fusion neutrons using a deuterated liquid scintillator", Phys Rev C 42 (5): R1809–R1812, doi:10.1103/PhysRevC.42.R1809  
  40. ^ Joyce 1990
  41. ^ a b c US DOE 1989
  42. ^ Taubes 1993, Close 1992, Huizenga 1993, Park 2000
  43. ^ Schaffer 1999, p. 3
  44. ^ Schaffer 1999, p. 3, Adam 2005 - ("Extraordinary claims . . . demand extraordinary proof")
  45. ^ Schaffer and Morrison 1999, p. 3 ("You mean it's not dead?" – recounting a typical reaction to hearing a cold fusion conference was held recently)
  46. ^ Adam 2005 - ("Advocates insist that there is just too much evidence of unusual effects in the thousands of experiments since Pons and Fleischmann to be ignored")
  47. ^ Mallove 1991, p. 246-248
  48. ^ Voss 1999
  49. ^ Pollack 1997, p. C4
  50. ^ Feder 2004, p. 27
  51. ^ Adam 2005 (comment attributed to George Miley of the University of Illinois)
  52. ^ Jagdish Mehra, K. A. Milton, Julian Seymour Schwinger (2000), Oxford University Press, ed., Climbing the Mountain: The Scientific Biography of Julian Schwinger (illustrated ed.), New York: Oxford University Press, p. 550, ISBN 0198506589, http://books.google.com/books?id=9SmZSN8F164C&pg=PA550&vq=resigned+american+physical+society+cold+fusion&dq=Julian+Schwinger+cold+fusion&hl=es&source=gbs_search_s&cad=0  
  53. ^ a b Jayaraman 2008
  54. ^ Mullins 2004
  55. ^ Hagelstein et al. 2004, p. 3, 14
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  57. ^ Chubb et al. 2006, Adam 2005 ("Anyone can deliver a paper. We defend the openness of science" - Bob Parks of APS, explaining that hosting the meeting does not show a softening of scepticism)
  58. ^ Van Noorden 2007, para. 2
  59. ^ Di Giulio 2002
  60. ^ Feder 2005
  61. ^ a b Van Noorden 2007
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  63. ^ a b "New Cold Fusion Evidence Reignites Hot Debate", IEEE Spectrum, http://www.spectrum.ieee.org/energy/nuclear/new-cold-fusion-evidence-reignites-hot-debate  
  64. ^ a b c Barras 2009
  65. ^ Scientists in possible cold fusion breakthrough, AFP, http://www.google.com/hostednews/afp/article/ALeqM5j2QobOQnlULUZ7oalSRUVjnlHjng, retrieved 2009-03-24  
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  71. ^ a b Simon 2002, pp. 193,233
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  74. ^ Fox 1994 in reference to Canon's EP patent 568118
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  86. ^ Szpak 2004
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  94. ^ Wilson 1992
  95. ^ Shanahan 2005
  96. ^ Shanahan 2006
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Bibliography

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Study guide

Up to date as of January 14, 2010

From Wikiversity

Welcome to the Cold Fusion learning project.

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Content summary

Cold fusion is technically the name for any nuclear fusion reaction that may occur well below the temperature required for thermonuclear reactions (millions of degrees Celsius).

There are a number of established processes by which this can occur, although currently none of these can produce more energy than is required to sustain and contain the reaction.

Types of Cold Fusion

The term "cold fusion" is most often used in the narrow sense of a poorly understood phenomenon in electrolytic cells in which a small (table-top) setup near room temperature and standard atmospheric pressure, which has been controversially suggested produces the fusion of hydrogen (specifically deuterium) atoms into helium.

Room temperature

  • Electrolytic cell fusion. Fleischmann and Pons used a double-walled vacuum flask for the electrolysis chamber (palladium cathode), so that heat conduction would be minimal. They used an open cell, thus allowing the gaseous deuterium and oxygen resulting from the electrolysis reaction to leave the cell. It was necessary to replenish the cell with heavy water at regular intervals.
  • ..

Generally cold, locally hot fusion

  • Sonoluminescence
  • ...

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Simple English

Cold fusion is nuclear fusion at room temperature and normal pressure. Nuclear fusion is the process by which many nuclei, the center of an atom, containing protons and neutrons, are forced to join together to form a heavier nucleus (singular of nuclei) and during that process, energy is released. Some scientists hope that this may be Earth's future energy source, but most scientists do not agree.

For nuclear fusion to take place, a large amount of energy is needed. With this energy, the atoms are pushed together, which are repelled by the electrostatic force (a force between protons which are particles in the nucleus of the atom and have a positive electrical charge). But once this force is overcome and the nuclei are pushed close enough together, another much more powerful force will take over: the strong nuclear force. It only operates at short distances, so when the nuclei are close enough, they attract each other because of the strong nuclear force which is stronger than the electrostatic force. It is hoped that the energy released by cold fusion is much greater than the energy used to push the atoms together.

In 1989 two scientists, Stanley Pons and Martin Fleischmann, published a paper in Nature, an important science journal, claiming to have created cold fusion. This was a very important story at the time. Other scientists were not able to repeat their experiments and this is why cold fusion is not generally accepted by scientists at the moment. Several dozen scientists are still working on cold fusion still, and they publish in peer-reviewed journals and other academic sources regularly, but most are not convinced.

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