Cold fusion

Public interest in cold fusion began in dramatic fashion 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 fusion process.

The fusion of nuclei is an energy source, as is witnessed by the hydrogen bomb. A number of nuclei fuse together in an exploding hydrogen bomb releasing enormous amounts of energy, but, unfortunately, this happens in an uncontrolled manner. Since the early 1950s worldwide research has been underway to control the fusion process because it would give an unlimited source of energy. This research focuses on very high temperatures (on the order of a billion degrees Celsius) to achieve the fusion process. Cold fusion, on the other hand, seems to proceed in the laboratory at room temperature, hence its name.

The report of the results of Pons and Fleischmann 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 was not convincing. Many mainstream scientists have since cited cold fusion is an example of either irreproducible science or even of pseudoscience.

Background

When a very hot (on the order of 10⁸ to 10⁹ °C) 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 propose that nuclear reactions can be initiated without extra energy or application of neutrons by creating a special solid material: highly loaded palladium deuteride (i.e. 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 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. Some claims can be explained as being caused by error or unrecognized prosaic processes.

Continuing research

Despite these objections, study of the effect continued, and by 2000, over 200 groups had published replications.

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 have been explored, but none have gained acceptance by conventional science.

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. 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 developed 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. but no single error has been identified that can explain all of the positive results.

© 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. 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.

Finally, the presence of heavy elements having unnatural isotopic ratios and in unexpectedly large amounts are detected under some conditions. These are the so called transmutation products. Work in Japan has opened a 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.

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

Before the announcement of Fleischmann and Pons in 1989, other researchers had reported some tentative evidence for cold fusion. In the 1920's 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 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.

The Pons and Fleischmann announcement and its aftermath

Soon after the announcement, researchers in many laboratories attempted to replicate the experiment. 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.

In 1989 and 1990, 20 groups at major U.S. laboratories, with 135 researchers, published papers describing attempted replications that failed. 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 in particular to the work of three internationally leading laboratories (in Caltech, Harwell and MIT) as proof that the reported evidence for cold fusion was unsound. Experts in calorimetry and electrochemistry later reviewed these results and disputed the conclusions.

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.

In 1989, the state of Utah funded a National Cold Fusion Institute. Researchers there published several papers describing 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 the reported evidence for cold fusion must be incorrect, and some declared that it is fraudulent. In 1991, Robert Park 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 feel they have been persecuted. 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 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.

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.