Cold fusion

The field of research and the name cold fusion began spectacularly in 1989 when chemists Stanley Pons of the University of Utah and Martin Fleischmann of the University of Southampton reported in a press conference that they had conducted low-cost experiments that led to the production of excess heat in an electrolytic cell in a manner that could only be produced by a nuclear process. The report of their results was widely publicized amidst worldwide excitement, briefly raising hopes that a cheap and abundant source of energy had been found. These and similar claims for unexpected nuclear reactions were not replicated with consistency by other laboratories. In 1989 and 1990, 20 groups at major U.S. laboratories, with 135 researchers, published papers describing attempted replications that failed. Consequently the interest of mainstream science has waned.

Two separate review panels organized by the United States Department of Energy, the first in 1989 and the second in 2004, concluded that the evidence is not convincing. Both panels recommended that limited research funding be made available. The 2004 report says: "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. . ." This recommendation has not been implemented.

Many mainstream scientists have since cited cold fusion is an example of either irreproducible science or even of pseudoscience.

Cold fusion should not be confused with sonofusion (or bubble fusion), another controversial process.

Background

When a plasma is used to produce fusion between two deuterons, the process is called "plasma fusion" (or sometimes "hot fusion"). This reaction is known to emit neutrons and produce tritium in equal amounts. The established theory is that nuclear fusion reactions cannot be initiated without the input of significant energy to overcome the charge barrier between nuclei, called the Coulomb barrier, yet cold fusion occurs at very low energy levels.

Reactions involving neutrons (or muons, or other neutral particles) can occur because these particles do not have a charge and can pass through the barrier. However, neutrons are not observed to form under conditions that produce the cold fusion reactions and they are not known to exist as free particles in ordinary materials.

Cold fusion generated widespread publicity since it seemed to defy these theoretical considerations and it represented a potentially cheap and clean source of energy.

Experimental claims

Fleischmann and Pons, and others who have replicated their work, propose that nuclear reactions can be initiated without extra energy or application of neutrons by creating a special solid material: highly loaded palladium deuteride. That is, palladium which has absorbed nearly as many atoms of deuterium as the number of palladium atoms in the sample. This material is extremely difficult to produce. When fusion of deuterium takes place in this environment, they claim the main product is ordinary helium and heat, which are produced in the same ratio as they are with plasma fusion, and also tritium, neutrons, and mild radiation, which are detected at levels much lower than plasma fusion produces.

In addition, subsequent studies claim that more complex nuclear reactions can occur that are able to convert one element into another in a process called transmutation for which the Coulomb barrier is even greater than between deuterium nuclei. Conventional theory cannot explain such claims, and the observations have been difficult to reproduce, which is why the claims are controversial. In addition, some claims can be explained as being caused by error or unrecognized prosaic processes.

Continuing research

In spite of these objections, study of the effect has continued over the last 19 years. By September 1990, 92 groups from 10 countries reported successful replications. By the year 2000, over 200 groups had published replications in the peer-reviewed literature.

Evidence for a variety of nuclear processes has been presented including transmutation, fusion, and fission. For this reason, the terms "Low Energy Nuclear Reactions" (LENR), “Chemically Assisted Nuclear Reactions” (CANR), and "Condensed Matter Nuclear Science" (CMNS) are now used to describe work in this area of study. Many theories are being explored in order to identify a possible mechanism, although none have yet gained acceptance by conventional science. Many international conferences have been held and papers on the subject are regularly presented at American Physical Society, American Nuclear Society and American Chemical Society meetings in the US and at conferences in other countries. As a result, much more is known about the process than was available in 1989, when initial skepticism developed.

Excess heat production is an important characteristic of the effect and has created the most criticism. This is because calorimetry can be a difficult measurement and it is not well understood by many scientists. In addition, the original measurements, as well as a few other studies, were based on complex methods of isoperibolic calorimetry. Subsequently, evidence based on more readily understandable methods such as flow and Seebeck calorimetry have been published. For example, McKubre et al. at SRI spent millions of dollars developing a state of the art flow calorimeter (Fig. 1), which was used to study many samples that showed production of significant anomalous energy. Over 36 similar studies have observed the same general behavior as was reported by these workers. Of course, all of the positive results could be caused by various errors. This possibility has been explored in many papers, which have been reviewed and summarized by Storms. Although a few of the suggested errors might have affected a few studies, no error has been identified that can explain all of the positive results, especially those using well designed methods. At this time, it is safe to conclude that anomalous energy is produced, regardless of whether the source is nuclear reactions or something unknown to science. The magnitude of the heat release and the fact that no chemical fuel is consumed and no chemical ash produced rules out a chemical explanation.

© Image: SRI, Inc.
Figure 1. Labyrinth (L and M) Calorimeter and Cell developed by McKubre et al. at SRI. The entire calorimeter is contained in a vacuum Dewar to isolate it from the surroundings. Water flows into the inner region after its temperature is measured where it enters. After passing by and completely covering the wall of the electrolytic cell, it exits through a mixing tube, designed to insure that the measured temperature represents the average. Gas in the cell makes contact with a catalyst to insure all of the O₂ and D₂ is returned to the cell as D₂O. Loss or gain of gas is measured external to the cell. The D/Pd ratio of the Pd cathode is measured using its resistivity, which is determined using the 4 probe method. Heating wire is wrapped around the electrolytic cell to maintain constant temperature and to allow calibration. The device was demonstrated to be accurate and stable to better than ±50 mW.

To show that the source of the energy is a nuclear reaction, it is necessary to show that the amount of energy is related to the amount of a nuclear product. Until the work of Miles et al. various unexpected nuclear products had been detected, but never in sufficient amounts. Miles et al. showed that the helium was generated when anomalous heat was measured and that the relationship between the two measurements was consistent with the amount of energy known to result from a d-d fusion reaction. Since then, five other studies have observed the same relationship. Some of the detected helium could have resulted from helium known to be in normal air. It is unlikely that the heat and helium measurements were wrong by just the right amount every time the measurements were made. When helium leaks into a cell with air, it is found in much larger amounts than Miles and others observed, and it leaks in along with other gases that were not present in the sample. Thus, heat and helium appear to be correlated, but the nuclear process producing helium is still to be determined.

Nuclear products other than helium are detected in much smaller quantities. Early in the history, great effort was made to detect neutrons, an expected nuclear product from the d-d fusion reaction. Except for occasional bursts, the emission rate was found to be near the limit of detection or completely absent. This fact was used to reject the initial claim. It is now believed that the few observed neutrons are caused by a secondary nuclear reaction, possibly having nothing to do with the helium producing reaction. Tritium is another expected product of d-d fusion, which was sought. Again, tritium was detected but only in small amounts that were inconsistent with expectations. Nevertheless, the amount of tritium detected could not be explained by any prosaic process after all of the possibilities had been completely explored. The source of tritium is still unknown although it clearly results from a nuclear reaction that is initiated within the apparatus. Various nuclear products normally associated with d-d fusion also have been detected as energetic emissions, but at very low rates. Clearly, unusual nuclear processes are occurring in material where none should be found. Cold fusion researchers feel that this fact alone, regardless of the explanation, requires serious attention.

Finally, the presence of heavy elements having unnatural isotopic ratios and in unexpected large amounts are detected under some conditions. These are the so called transmutation products. Work in Japan has opened an entirely new aspect to the phenomenon by showing that impurity elements in palladium, through which D₂ is caused to pass, are converted to heavier elements to which 2D, 4D or 6D have been added. The claims have been replicated in Japan.

Although initial observations were made using an electrolytic cell in which the active material was palladium and the source of fuel was D₂O, many other methods are now claimed to produce the same kind of nuclear reactions. In addition, the active material can be several other materials besides palladium, all of which need to have a unique structure and generally are present with nanosized dimensions.

Explanations for the phenomena

Many theories are being explored, a few examples of which are:

1. Reduction of the Coulomb barrier by electrons being concentrated between the nuclei;
2. Conversion of deuterium into a wave structure that ignores the Coulomb barrier,
3. Creation or release of neutrons within the structure, which add to nuclei that are present,
4. Creation of clusters of deuterons that interact as units,
5. Involvement of phonons to concentrate energy at the reaction site and carry away the released energy.
6. Models showing that the Coulomb barrier is not as high as previously thought if certain conditions are present.

All of these mechanisms are only possible because a regular lattice of atoms and electrons is available and because the normally applied large energy does not hide these subtle processes. Models based on experience using high energy and/or a plasma, in which this regular array of atoms is not present, are not applicable.

A clean, cheap source of energy?

If the claims are real, regardless of their explanation, what are the potential consequences to society? Like plasma fusion -- which is produced in a Tokamak reactor such as the upcoming ITER -- cold fusion is also proposed to produce energy from the fusion reaction. Unlike plasma fusion, cold fusion produces only helium without a significant amount of radioactive products. The main source of energy proposed for plasma and cold fusion is deuterium, which is present in all water.

The hopes of nuclear fusion as an energy source are fueled by the fact that enough deuterium is available on earth to produce energy at present rates for billions of years. The cost of refining deuterium from water is far cheaper per unit of energy than for chemical, wind or solar energy. While plasma fusion requires huge installations to be practical the attraction of cold fusion is that it could be practical on a small scale. By 1990, cold fusion cathodes produced temperature and power density equal to a fission reactor core, and power levels up to 100 W, so if the reaction can be controlled and generated on demand, it seems likely that it can be used as a practical source of energy. If it can be made to work, mankind could expect to produce pollution-free, low cost power without the risk posed by radioactive products, far into the future.

The history of cold fusion before 1989

Although cold fusion was discovered by M. Fleischmann and S. Pons and announced in 1989, other researchers had earlier observed fleeting evidence for it. In the 1920s Paneth and Peters thought they had measured helium from a metal hydride room temperature fusion reaction, but they later retracted the claim. Y. E. Kim believes that P. I. Dee may have seen evidence for cold fusion in 1934.

In 1929, A. Coehn showed anomalies in the electromigration of protons. In 1949, Fleischmann became aware of this work, and speculated that the observations might open up "a slim chance of inducing nuclear processes if his methodology were combined with such explosions (which one would now describe under the heading of inertial confinement) . . ." He also cited work by Oliphant, Harteck and Rutherford, and the work by Dee later cited by Kim. Fleischmann revisited the topic in the late 1960s, and in the 1980s he began experimental studies in collaboration with Pons.

In the 1980s, some theoreticians speculated that extremely high pressure can be developed in microscopic areas on the surface of a palladium hydride. In 1981, around the time Fleischmann and Pons were beginning their experiments, Mizuno was working with palladium deuterides for reasons unrelated to cold fusion. He observed evidence of excess heat and charged particles, but after puzzling over them for some time, he dismissed them as instrument error. He later wrote that most electrochemists who worked with palladium deuterides were aware of reports of possible nuclear anomalies.

Unlike these early researchers, Fleischmann and Pons observed a clear signal, which they repeated many times, and after years of effort in the 1980s they developed fairly reliable techniques to reproduce the effect. One of their experiments produced a gigantic heat release during the night that destroyed the apparatus and burned a hole in the table underneath it. The energy required to do this is far greater than the chemical energy available in the cell. (Six similar explosions have been reported since 1989. )

Shortly before Fleischmann and Pons announced their work, they became embroiled in an acrimonious dispute over academic priority with S. Jones. The University of Utah, which held intellectual property rights to their discovery, was forced to hold a press conference and release the results several years before they originally planned to. Jones claimed priority in the discovery of neutrons from palladium deuterides. This dispute is largely moot because soon after the announcement, it was shown that the Fleischmann and Pons neutron results were in error, and Jones later expressed doubts about his own neutron studies, which have proved very difficult to reproduce. He does not believe any excess heat reports, so he does not dispute this priority. Other researchers subsequently published more convincing neutron results, which have not been retracted.

The Pons and Fleischmann announcement and its aftermath

Soon after the announcement, researchers in many laboratories attempted to replicate the experiment. Many of these researchers were not electrochemists and did not realize what the experiment entailed, what the control factors were, or how difficult the experiment was. Although it is widely believed that cold fusion experiments are "easy," most electrochemists consider them extremely difficult. R. Oriani said that in his 50-year career this was the most difficult experiment he ever performed.

As noted above, the results were released years earlier than planned because of intellectual property concerns. Fleischmann and Pons did not understand the experiment well enough to describe it properly. As noted above, in 1989 and 1990, 20 groups at major U.S. laboratories, with 135 researchers, published papers describing attempted replications that failed. The reasons for these failures are now well understood, but at the time these researchers were justifiably upset. Storms later wrote: ". . . the many failures and the serious errors found in the Fleischmann and Pons paper fueled a growing doubt about the original claims. Too many people had spent too much time to get so little. They were beginning to feel they had been had."

Skeptics pointed to the work of three laboratories as proof that cold fusion does not exist: N. Lewis et al. (CalTech), D. E. Williams et al. (Harwell) and D. Albagli et al. (MIT). Experts in calorimetry and electrochemistry later reviewed these results and disputed the conclusions. They found that the results from CalTech and Harwell were actually positive but the authors’ analysis of the data is in error.

The published data from MIT is clearly negative, but a copy of the original data was leaked and it is substantially different from the published version. The original graphs show small but clear indications of excess heat, yet in the published version the data points have been lowered and 7 extraneous data points have been added to the graph, which leads to the suspicion that the data may have been tampered with.

In May 1989 the US Energy Research Advisory Board (ERAB) formed a special panel to investigate cold fusion. The scientists in the panel found the evidence to be unconvincing. Electrochemists pointed out that the materials preparation and initial loading usually takes several months, so it was unlikely that anyone would replicate at the time the ERAB panel surveyed results (May 1989). They think this was rush to judgment. Miles later wrote:

In retrospect, it would be impossible for any research group to adequately investigate the multitude of variables involved with this field in only a few months. These variables range from the palladium metallurgy to the D₂O purity, the type of electrolyte and concentration, the electrochemical cell, the electrode arrangement, the type of calorimeter, proper scaling of the experiments, the handling of materials, the current densities used, the duration of the experiments, the loading of deuterium into the palladium, the use of additives, and so on.

In late 1989, Miles and others informed the ERAB panel members that their experiments were now producing excess heat, tritium and other effects, but the ERAB panel did not revise their conclusions, and they listed Miles as a negative result.

In 1989, the state of Utah funded a National Cold Fusion Institute. Researchers there published several peer-reviewed papers describing 100% reproducible production of tritium, at rates of 7 x 10¹⁰ to 2.1 x 10¹¹. The institute was soon closed down in response to harsh opposition to cold fusion research and ridicule in the national press.

Soon after the announcement, many scientists and journalists concluded that cold fusion must be incorrect, and some declared that it is fraudulent. In 1991 Robert Park famously denounced cold fusion in the Washington Post as the result of "foolishness or mendacity." . . . "What began as wishful interpretations of sloppy and incomplete experiments ended with altered data, suppression of contradictory evidence and deliberate obfuscations." F. Slakey, the Science Policy Administrator of the American Physical Society, said that cold fusion scientists are "a cult of fervent half-wits" "While every result and conclusion they publish meets with overwhelming scientific evidence to the contrary, they resolutely pursue their illusion of fusing hydrogen in a mason jar. . . . And a few scientists, captivated by [Fleischmann and Pons'] fantasy . . . pursue cold fusion with Branch Davidian intensity." Thousands of similar harsh comments have been published in the mass media.

Cold fusion researchers complain that they have not committed fraud, and they feel they have been persecuted. Most report they have not been promoted since 1989. At least three were forced to retire early or fired outright. Full professors were locked out of laboratories and reassigned to menial jobs such as stockroom clerks. They were repeatedly investigated by university committees, and their lives disrupted by attacks in major newspapers and magazines. Most Federal researchers have been ordered not to publish their results or attend conferences. No research has been funded by the Department of Energy (except some discretionary funding at a few National Laboratories). The U.S. Department of Defense has funded some programs.

In 1990 the American Physical Society (APS) told Nobel laureate Julian Schwinger he would not be allowed to publish papers or even letters on cold fusion in APS journals. Schwinger resigned in protest, saying:

The pressure for conformity is enormous. I have experienced it in editors’ rejection of submitted papers, based on venomous criticism of anonymous referees. The replacement of impartial reviewing by censorship will be the death of science.

Skeptics opposed to cold fusion feel they are not persecuting anyone, but merely upholding academic standards and preventing fraud. The dispute continues to the present day.

Some examples of progress made since 1989

Considerable progress has been made in cold fusion since 1989, notably in a collaborative research project with SRI, DARPA, the Italian government ENEA agency, the Naval Research Laboratory (NRL), MIT and Energetics Technology, Ltd. Israel. Progress has been made in reproducibility; in identifying and fabricating suitable materials; identifying factors that stimulate and control the reaction; and in increasing the magnitude of the excess heat, and the ratio of output to input. This section presents some data from this collaborative project.

© Image: EPRI
Figure 2. An example of excess heat from SRI, 1992 measured with the calorimeter type shown in Fig. 1. From: McKubre, M.C.H., et al., Development of Advanced Concepts for Nuclear Processes in Deuterated Metals. 1994, EPRI.

Figure 2 shows excess heat measured with the calorimeter shown in Fig. 1. Excess heat peaked at 0.5 W (500 mW) in a calorimeter that can measure 50 mW with confidence (as noted in Fig. 1). The excess continued for 122 hours. The blue data points at the bottom show results from a light water cell run in parallel to the heavy water cell, which produced no excess heat. Total excess energy was 0.20 MJ. Input power in this case was 10.5 W, so average excess output power was only 4.8% of input. Excess power up to 350% of input has been measured in other experiments using this equipment.

© Image: Energetics Technology, Ltd.
Figure 3. An example of excess heat from Energetics Technology, Ltd., 2006. Input power is typically ~1 W, and average output is 25 times larger. Total excess energy output is 1.14 MJ, which far exceeds any possible chemical energy output from a cell of this size. From McKubre, M.C.H. Cold Fusion at SRI (PowerPoint slides). in APS March Meeting. 2007. Denver, CO.

Figure 3 shows a more recent example of excess heat. Compared to Fig. 2, this cell produced higher absolute power (~20 W), more excess energy (1.14 MJ), and a larger ratio of output to input (2500%). Note that in many experiments such as those with gas loading or in heat after death, there is no input electric power, so all output heat is from cold fusion.

© Image: SRI
Figure 4. Data from 70 experiments performed at SRI and ENEA. Cathodes which are loaded to a ratio above 0.92 (with 92 deuterium atoms for every 100 atoms of palladium) are much more likely to produce excess heat than cathodes at lower loading. From McKubre, M.C.H. Cold Fusion at SRI (PowerPoint slides). in APS March Meeting. 2007. Denver, CO.

Figure 2 shows that excess heat is correlated with current density; current density is a control factor. Figure 4 shows that loading is another important control factor. Most experiments that failed in 1989 did not achieve sufficient loading or current density. Several other control factors and necessary conditions have been established.