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 * ''For information on legitimate research into relatively or locally "cold" fusion, see the Wikipedia article on nuclear fusion

Cold fusion, also called Low Energy Nuclear Reactions (LENR) or Chemically-Assisted Nuclear Reactions (CANR) by its proponents, is the claim of nuclear reactions at relatively low temperatures, rather than at millions of degrees. The most common system where this phenomenon is supposed to occur is an electrolytic cell with a palladium cathode that is electrolyzing deuterium oxide (a.k.a. heavy water).

The term was popularised with the work of Pons and Fleischmann, which gained tremendous publicity but was difficult to reproduce. It was then taken up with enthusiasm by cranks, thinking they could be the ones to bring cheap energy to the world. The most outrageous claims include blatant fraud such as the Energy Catalyzer. Cranks also believe there is a massive conspiracy to suppress information about cold fusion.

There are credible scientists working on fusion at less than millions of degrees, but they tend to avoid the term "cold fusion."

Pons and Fleischmann
Martin Fleischmann and Stanley Pons were electrochemists who had worked together for many years. In 1983, they claimed they saw something anomalous and thought "That's funny ..." Allegedly refining their experiments over the next six years, they finally decided that all chemical explanations had been shown false and that a nuclear reaction was the only remaining possibility. Their paper, "Electrochemically induced nuclear fusion of deuterium," was accepted by the Journal of Electroanalytical Chemistry March 22, 1989, but was publicized by press conference the next day and was published April 10.

Pons' and Fleischmann's work was quickly discredited by scientists, due to multiple, repeated failures of replication, and a lack of reports of expected neutron flux from the fusion reaction. Deuterium fusion often produces helium-3 as well as substantial amounts of neutrons, an effect that can be demonstrated using a Farnsworth fusor (a hot-fusion device developed by one of the several inventors of television); the canonical experiment involves irradiating a piece of aluminum foil with the fusor and then testing the foil for radioactivity with a Geiger counter. Since neutrons can do this to pretty much any element, including carbon (creating a radiation source within the subject's body), the joke that went around physics labs at the time was along the lines of "Did you hear about Pons and Fleischmann's lab tech? He's perfectly healthy." This has been called the "dead graduate student effect." The reaction rate necessary for the reported heat would have produced fatal levels of highly-penetrating neutron radiation.

At the present time, with our current understanding of physics and electrochemistry, cold fusion as Pons and Fleischmann described it is impossible. This is because the energy required to kick start a fusion reaction is very high, and doing it with a mere electrochemical cell is an astounding result &mdash; one that would have to have extraordinary evidence to back it up. Cold fusion cranks tout the few physicists, such as Schwinger and Hagelstein, who even entertain the possibility Pons and Fleischmann were onto something. Nevertheless, everyone else thinks they were deluded at best.

Energy Catalyzer
Entrepreneur, convicted felon, and inventor Andrea Rossi has announced the E-Cat (Energy Catalyzer), a device claimed to generate kilowatt-level heat from nickel and hydrogen. Rossi has explained this as involving the transmutation of nickel into copper, a reaction so ridiculously unfeasible it doesn't occur even in supernovae.

Demonstrations of Rossi's devices have been controversial and insufficient details have been released for independent third-party verification. The claimed reaction has not been supported by independent observers, even by a physicist (Sven Kullander) who has supported the claims of excess heat. Even cold fusion proponents are skeptical of Rossi's claims.

Cold fusion as pseudoscience
Pons and Fleischmann may have been doing low-quality real science, not definitively pseudoscience. Current advocates, however, are well into the realm of the determined pseudoscientific crackpot.


 * 1) The effects are difficult to reproduce, and the level of heat produced can vary greatly.
 * 2) The existence of this effect, and especially the lack of gamma radiation, is contrary to the current understanding of nuclear physics, for which there is massive evidence.
 * 3) Proponents trumpet any paper concerning the subject that achieves peer review in any venue whatsoever, as if "peer reviewed" meant "solid verified and settled science" rather than "not-obviously-wrong request for comment."
 * 4) Proponents advocate cold fusion as an alternative energy source with imminent practical utility, despite the aforementioned lack of reproducibility.
 * 5) At the same time, proponents try to blame their lack of success on persecution from the establishment.
 * 6) The theories proposed to explain the supposed effect, outlined in the 2010 review, are little more than contrived rationalizations of the claimed observations. When considered in the context of what is already known about physics and chemistry, they border on the nonsensical.

There is a continuing failure to find a setup that consistently (nearly 100% of the time) reproduces the supposed effect. The majority of written-up experiments failed even to obtain excess heat. The primary research effort should be on improving reproducibility; instead, the cold fusion people live in a fantasy where their field has imminent practical engineering applications despite not having even reproducible science. This is a telltale sign of crankery.

Pons and Fleischmann method
Experiments along the lines of what Pons and Fleischmann did are still being carried out at the US Navy's Space and Naval Warfare Systems Center. Several have been published in the off-topic or fringe journals Naturwissenschaften, the Journal of Electroanalytical Chemistry and the Journal of Fusion Energy.

The most recent comprehensive review of the field by Edmund Storms, a proponent of cold fusion, Status of cold fusion (2010), was published in a peer-reviewed journal on life sciences and environmental sciences in which Storms is a member of the editorial board. The review claims that there is evidence that the effect exists and involves a nuclear reaction, but in fact the included charts show that the majority of reports analyzed, on that point, observed no excess heat.

Production of very-high-Z nuclides
Producing very-high-Z nuclides &mdash; new elements not previously observed in nature &mdash; is commonly done through arranging collisions of nuclei in particle accelerators at energies below the energy normally needed to penetrate the repulsion of nuclei from each other. Thus it is "cold," and the yield is low because the reaction only takes place through tunneling. There is a large net energy absorption in this fusion. It's done this way because the nucleides being produced are extremely fragile, in addition to having very short lifetimes.

Muon-catalyzed cold fusion
Muons are "heavy electrons", with the same size and electrical charge, but about 207 times heavier than the ordinary electron. When it replaces an ordinary electron, it will, in the ground state, orbit 207 times closer to the nucleus. If this occurs in a molecule of deuterium, the two nuclei will be drawn close enough together that quantum tunneling may result in fusion to helium.

The highest reaction rate is seen when deuterium and tritium are involved. However, muons have a half-life of about 2 microseconds, so a single muon will only catalyze so many reactions. So to generate useful power, muons would need to be continually produced, and the energy required to generate them with known techniques is much more than is generated by the number of reactions attained. As the reactions take place, in actual research, at temperatures close to absolute zero, in mixtures of hydrogen isotopes, this is truly cold fusion, and was the first reaction to be so termed.