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Cold fusion is the name for a nuclear fusion reaction that occurs well below the temperature required for thermonuclear reactions (millions of degrees Celsius). Such reactions may occur near room temperature and atmospheric pressure, and even in a relatively small (table top) experiment. In a narrower sense, "cold fusion" also refers to a particular type of fusion supposedly occurring in electrolytic cells.

The term "cold fusion" was coined by Dr Paul Palmer of Brigham Young University in 1986 in an investigation of "geo-fusion", or the possible existence of fusion in a planetary core. It was brought into popular consciousness by the controversy surrounding the Fleischmann-Pons experiment in March of 1989. A number of other scientists have reported replication of their experimental observation of anomalous heat generation in electrolytic cells, but in a non-predictable way, and most scientists believe that there is no proof of cold fusion in these experiments. A majority of scientists consider this research to be pseudoscience, while proponents argue that they are conducting valid experiments in a protoscience that challenges mainstream thinking.

The subject has been of scientific interest since nuclear fusion was first understood. Hot nuclear fusion using deuterium yields large amounts of energy, uses an abundant fuel source, and produces only small amounts of manageable waste; thus a cheap and simple process of nuclear fusion would have great economic impact. Unfortunately, no "cold" fusion experiments that gave an otherwise unexplainable net release of energy have so far been reproducible.

History of cold fusion by electrolysis

Early work

The idea that palladium or titanium might catalyze fusion stems from the special ability of these metals to absorb large quantities of hydrogen (including its deuterium isotope), the hope being that deuterium atoms would be close enough together to induce fusion at ordinary temperatures. The special ability of palladium to absorb hydrogen was recognized in the nineteenth century. In the late nineteen-twenties, two German scientists, F. Paneth and K. Peters, reported the transformation of hydrogen into helium by spontaneous nuclear catalysis when hydrogen is absorbed by finely divided palladium at room temperature. These authors later acknowledged that the helium they measured was due to background from the air.

In 1927, Swedish scientist J. Tandberg said 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.

Pons and Fleischmann's experiment

On March 23, 1989, the chemists Stanley Pons and Martin Fleischmann ("P and F") at the University of Utah held a press conference and reported the production of excess heat that could only be explained by a nuclear process. The report was particularly astounding given the simplicity of the equipment, just a pair of electrodes connected to a battery and immersed in a jar of heavy water (dideuterium oxide). The press reported on the experiments widely, and it was one of the front-page items on most newspapers around the world. The immense beneficial implications of the Utah experiments, if they were correct, and the ready availability of the required equipment, led scientists around the world to attempt to repeat the experiments within hours of the announcement.

The press conference followed about a year of work of increasing tempo by Pons and Fleischmann, who had been working on their basic experiments since 1984. In 1988 they applied to the US Department of Energy for funding for a larger series of experiments: up to this point they had been running their experiments "out of pocket".

The grant proposal was turned over to several people for peer review, including Steven Jones of Brigham Young University. Jones had worked on muon-catalyzed fusion for some time, and had written an article on the topic entitled Cold Nuclear Fusion that had been published in Scientific American in July 1987. He had since turned his attention to the problem of fusion in high-pressure environments, believing it could explain the fact that the interior temperature of the Earth was hotter than could be explained without nuclear reactions, and by unusually high concentrations of helium-3 around volcanoes that implied some sort of nuclear reaction within. At first he worked with diamond anvils, but had since moved to electrolytic cells similar to those being worked on by Pons and Fleischmann, which he referred to as piezonuclear fusion. In order to characterize the reactions, Jones had spent considerable time designing and building a neutron counter, one able to accurately measure the tiny numbers of neutrons being produced in his experiments.

Both teams were in Utah, and met on several occasions to discuss sharing work and techniques. During this time Pons and Fleischmann described their experiments as generating considerable "excess energy", excess in that it could not be explained by chemical reactions alone. If this were true, their device would have considerable commercial value, and should be protected by patents. Jones was measuring neutron flux instead, and seems to have considered it primarily of scientific interest, not commercial. In order to avoid problems in the future, the teams apparently agreed to simultaneously publish their results, although their accounts of their March 6th meeting differ.

In mid-March both teams were ready to publish, and Fleischmann and Jones were to meet at the airport on the 24th to both hand in their papers at the exact same time. However Pons and Fleischmann then "jumped the gun", and held their press conference the day before. Jones, apparently furious at being "scooped", faxed in his paper to Nature as soon as he saw the press announcements. Thus the teams both rushed to publish, which has perhaps muddied the field more than any scientific aspects.

Within days scientists around the world had started work on duplications of the experiments. On April 10th a team at Texas A&M University published results of excess heat, and later that day a team at the Georgia Institute of Technology announced neutron production. Both results were widely reported on in the press. Not so well reported was the fact that both teams soon withdrew their results for lack of evidence. For the next six weeks competing claims, counterclaims, and suggested explanations kept the topic on the front pages, and led to what writers have referred to as "fusion confusion."

In mid-May Pons received a huge standing ovation during a presentation at the American Chemical Society. The same month the president of the University of Utah, who had already secured a $5 million commitment from his state legislature, asked for $25 million from the federal government to set up a "National Cold Fusion Institute". On May 1st a meeting of the American Physical Society held a session on cold fusion that ran past midnight; a string of failed experiments were reported. A second session started the next evening and continued in much the same manner. The field appeared split between the "chemists" and the "physicists".

At the end of May the Energy Research Advisory Board (under a charge of the US Department of Energy) formed a special panel to investigate cold fusion. The scientists in the panel found the evidence for cold fusion to be unconvincing. Nevertheless, the panel was "sympathetic toward modest support for carefully focused and cooperative experiments within the present funding system".

Both critics and those attempting replications were frustrated by what they said was incomplete information released by the University of Utah. With the initial reports suggesting successful duplication of their experiments there was not much public criticism, but a growing body of failed experiments started a "buzz" of their own. Pons and Fleischmann later apparently claimed that there was a "secret" to the experiment, a statement that infuriated the majority of scientists to the point of dismissing the experiment out of hand.

By the end of May much of the media attention had faded. This was due not only to the competing results and counterclaims, but also to the limited attention span of modern media. However, while the research effort also cooled to some degree, projects continued around the world.

Experimental set-up and observations

In their original set-up, Fleischmann and Pons used a Dewar flask (a double-walled vacuum flask) for the electrolysis, so that heat conduction would be minimal on the side and the bottom of the cell (only 5 % of the heat loss in this experiment). The cell flask was then submerged in a bath maintained at constant temperature to eliminate the effect of external heat sources. They used an open cell, thus allowing the gaseous deuterium and oxygen resulting from the electrolysis reaction to leave the cell (with some heat too). It was necessary to replenish the cell with heavy water at regular intervals. The cell was tall and narrow, so that the bubbling action of the gas kept the electrolyte well mixed and of a uniform temperature. Special attention was paid to the purity of the palladium cathode and electrolyte to prevent the build-up of material on its surface, especially after long periods of operation.

The cell was also instrumented with a thermistor to measure the temperature of the electrolyte, and an electrical heater to generate pulses of heat and calibrate the heat loss due to the gas outlet. After calibration, it was possible to compute the heat generated by the reaction.

A constant current was applied to the cell continuously for many weeks, and heavy water was added as necessary. For most of the time, the power input to the cell was equal to the power that went out of the cell within measuring 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, for durations of 2 days or more. The generated power was calculated to be about 20 times the input power during the power bursts. Eventually the power bursts in any one cell would no longer occur and the cell was turned off.

Continuing efforts

There are still a number of people researching the possibilities of generating power with cold fusion. Scientists in several countries continue the research, and meet at the International Conference on Cold Fusion (see Proceedings at www.lenr-can.org).

The generation of excess heat has been reported by

• Michael McKubre, director of the Energy Research Center at Stanford Research International,
• Richard A. Oriani (University of Minnesota, in December 1990),
• Robert A. Huggins (at Stanford University in March 1990),
• Y. Arata (Osaka University, Japan),

among others. In the best experimental set-up, excess heat was observed in 50% of the experiment reproductions. Various fusion ashes and transmutations were observed by some scientists.

Dr. Michael McKubre thinks a working cold fusion reactor is possible. Dr. Edmund Storms, a former scientist with The Los Alamos National Laboratory in New Mexico, maintains an international database of research into cold fusion.

In March, 2004, the U.S. Department of Energy (DOE) decided to review all previous research of cold fusion in order to see whether further research was warranted by any new results.

On May 14, 2004, a foremost cold fusion champion, Dr. Eugene Mallove, was brutally murdered in a yet unresolved case. His death has both saddened and inspired the cold fusion and free energy community in general and has drawn international attention to the status of cold fusion today.

Arguments in the controversy

A majority of scientists consider current cold fusion research to be pseudoscience, while proponents argue that they are conducting valid experiments that challenge mainstream science. (see history of science and technology). Here are the main arguments in the controversy.

Reproducibility of the result

While some scientists have reported to have reproduced the excess heat with similar or different set-ups, they could not do it with predictable results, and many others failed. Some see this as a proof that the experiment is pseudoscience.

Yet, it is not uncommon for a new phenomenon to be difficult to control, and to bring erratic results. For example attempts to repeat electrostatic experiments (similar to those performed by Benjamin Franklin) often fail due to excessive air humidity. That does not mean that electrostatic phenomena are fictitious, or that experimental data are fraudulent. On the contrary, occasional observations of new events, by qualified experimentalists, can in some cases be the preliminary steps leading to recognized discoveries.

The reproducibility of the result will remain the main issue in the Cold Fusion controversy until a scientist designs an experiment that is fully reproducible by simply following a recipe, or that generates power continuously rather than sporadically.

Current understanding of nuclear process

The DOE panel says: "Nuclear fusion at room temperature, of the type discussed in this report, would be contrary to all understanding gained of nuclear reactions in the last half century; it would require the invention of an entirely new nuclear process".

However, this argument only says that the experiment has unexplained results, not that the experiment is wrong. As an analogy, superconductivity was observed in 1911, and explained theoretically only in 1957.

Current understanding of hot nuclear fusion shows that the following explanations are not adequate:

• Nuclear reaction in general: The average density of deuterium in the palladium rod seems vastly insufficient to force pairs of nuclei close enough for fusion to occur according to mechanisms known to mainstream theories. The average distance is approximately 0.17 nanometers, a distance at which the attractive strong nuclear force cannot overcome the Coulomb repulsion. Actually, deuterium atoms are closer together in D2 gas molecules, which do not exhibit fusion.

• Absence of standard nuclear fusion products: if the excess heat were generated by the fusion of 2 deuterium atoms, the most probable outcome would be the generation of either a tritium atom and a proton, or a He and a neutron. The level of neutrons, tritium and He actually observed in Fleischmann-Pons experiment have been well below the level expected in view of the heat generated, implying that these fusion reactions cannot explain it.

• Fusion of deuterium into helium 4: if the excess heat were generated by the hot fusion of 2 deuterium atoms into He, a reaction which is normally extremely rare, gamma rays and helium would be generated. Again, insufficient levels of helium and gamma rays have been observed to explain the excess heat, and there is no known mechanism to explain how gamma rays could be converted into heat.

Energy source vs power store

While the output power is higher than the input power during the power burst, the power balance over the whole experiment does not show significant imbalances. Since the mechanism under the power burst is not known, one cannot say whether energy is really produced, or simply stored during the early stages of the experiment (loading of deuterium in the Palladium cathode) for later release during the power burst.

A "power store" discovery would have much less value than an "energy source" one, especially if the stored power can only be released in the form of heat.

Other kinds of fusion

This article focuses on fusion in electrolytic cells. Other forms of fusion have been studied by scientists. Some are "cold" in the sense that no part of the reaction is actually hot (except for the reaction products), some are "cold" in the sense that the energies required are low and the bulk of the material is at a relatively low temperature, and some are "hot", involving reactions which create macroscopic regions of very high temperature and pressure.

Locally cold fusion :

• Muon-catalyzed fusion is a well-established and reproducible fusion process which occurs at low temperatures. It has been studied in detail by Steven Jones in the early 1980s. Because of the energy required to create muons, it is not able to produce net energy.

Generally cold, locally hot fusion :

• In Cluster impact fusion, microscopic droplets of heavy water (on the order of 100-1000 molecules) are accelerated to collide with a target, so that their temperature at impact reaches at most 10 kelvin, 10,000 times smaller than the temperature required for hot fusion. In 1989, Friedlander and his coworkers observed 10 more fusion events than expected with standard fusion theory. Recent research () suggests that the calculation of effective temperature may have failed to account for certain molecular effects which raise the effective collision temperature, so that this is a microscopic form of hot fusion.

• In sonoluminescence, acoustic shock waves create temporary bubbles that collapse shortly after creation, producing very high temperatures and pressures. In 2002, Rusi P. Taleyarkhan explored the possibility that bubble fusion occurs in those collapsing bubbles. If this is the case, it is because the temperature and pressure are sufficiently high to produce hot fusion.

• The Farnsworth-Hirsch Fusor is a tabletop device in which fusion occurs. This fusion comes from high effective temperatures produced by electrostatic acceleration of ions. The device can be built inexpensively, but it too is unable to produce a net power output.

• Antimatter-catalyzed fusion uses small amounts of antimatter to trigger a tiny fusion explosion. This has been studied primarily in the context of making nuclear pulse propulsion feasible.

Hot fusion :

• "Standard" fusion, in which the fuel reaches tremendous temperature and pressure inside a fusion reactor, nuclear weapon, or star.

Several of these systems are "nonequilibrium systems", in which very high temperatures and pressures are produced in a relatively small region adjacent to material of much lower temperature. In his doctoral thesis for Massachusetts Institute of Technology, Todd Rider did a theoretical study of all non-equilibrium fusion systems. He demonstrated that all such systems will leak energy at a rapid rate due to Bremsstrahlung, radiation produced when electrons in the plasma hit other electrons or ions at a cooler temperature and suddenly decelerate. The problem is not as pronounced in a hot plasma because the range of temperatures, and thus the magnitude of the deceleration, is much lower.

References

• Robert L. Park (2000) gives a thorough account of cold fusion and its history which represents the perspective of the mainstream scientific community.
• Two other sceptical books from the scientific mainstream are those by Frank Close (1992) and John Huizenga (1992). Huizenga was co-chair of the DOE panel set up to investigate the Pons/Fleischmann experiment, and his book is perhaps the definitive account of the cold fusion affair.
• Eugene Mallove's Fire from Ice (1991) is an early account from the pro-cold-fusion perspective. Charles Beaudette's Excess heat (2000) is a more recent scientific account of why cold fusion research prevailed.
• Voodoo Science: The Road from Foolishness to Fraud, by Robert L. Park; Oxford University Press, New York; ISBN 0195135156; May 2000.
• Too Hot To Handle, by Frank Close; Penguin Books; ISBN 0140159266; 1992.
• Cold Fusion: the scientific fiasco of the century, by John R Huizenga; Oxford Paperbacks; ISBN 0198558171; 1992.
• Fire from Ice, by Eugene Mallove; Infinite Energy Press; ISBN 1892925028; 1991.
• Excess Heat: why cold fusion research prevailed, by Charles Beaudette; Infinite Energy Press; ISBN 0967854814

See also

• alchemy
• transmutation
• Pathological science
• Protoscience

External links

Information:

• Energy Research Advisory Board, "Conclusions and recommendations"
• "Low Energy Nuclear Reactions - Chemically Assisted Nuclear Reactions". -- Information and links from pro-cold fusion research.
• L. Kowalski's web site: an overview of the current state of cold fusion research from a physics teacher
• Britz's cold nuclear fusion bibliography: An extentisve overview and review of almost all available publications about cold nuclear fusion.

News:

• "Sound waves size up sonoluminescence". PhysicsWeb. February 2002.
• "Whatever happened to cold fusion?". Physics World. March 1999.
• "Fusion experiment disappoints". BBC News. July 25, 2002
• "Cold Fusion Heats Up. CBC Science.
• DoE to review cold fusion Physics Today April 2004.
• Phys. Rev. E 69, 036109 (2004) "Additional evidence of nuclear emissions during acoustic cavitation", R. P. Taleyarkhan, J. S. Cho, C. D. West, R. T. Lahey, Jr., R. I. Nigmatulin, and R. C. Block.

• Pseudoscience