Updated November 11, 2016
Cold Fusion: A New Perspective
Recently there have been reliable reports that some big U.S. investment groups as well as at least one of the biggest U.S. high-tech companies have decided to invest large amounts of money into the development of so-called “cold fusion” as an energy source. There is reportedly now a race for control over patent rights, manpower and laboratory capabilities relevant to achieving that goal. The reason for the sudden burst of interest from the side of U.S. businessmen is not yet clear. At the same time, the U.S. Department of Energy and most of the scientific community continue to take the position that cold fusion does not exist.
Cold fusion, it will recalled, is the phenomenon first reported by the chemists Fleischman and Pons in 1989, of the generation of significant amounts of heat by nuclear fusion reactions between deuterium nuclei implanted or “loaded” at high density into the crystal lattice of certain metals -- at room temperature and without producing dangerous amounts of ionizing radiation of the type that normally accompany nuclear reactions. The term “low energy nuclear reactions (LENR)” has also come into use, reflecting the opinion of some scientists that other nuclear processes may be occurring besides fusion.
Needless to say, the idea of a nuclear energy source that could fit into a briefcase, produces no hazardous radioactivity and has a virtually unlimited supply of fuel, seems “too good to be true”. The situation around cold fusion today is indeed paradoxical. The consensus opinion in the scientific establishment remains that the phenomenon of cold fusion does not exist, that reported observations of cold fusion are invalid and based on experimental errors, and that cold fusion is impossible according to the known laws of physics. (I shall indicate below why the latter assertion is premature and almost certainly incorrect.) Especially the absence of significant ionizing radiation (radioactivity) accompanying the claimed production of energy in cold fusion experiments, seems incredible. Critics have even spoken of cold fusion as an example of pseudo-science or “pathological science”. Nevertheless, cold fusion research has continued in government, university and private laboratories around in world, including in the U.S., Japan, India, Russia, Italy and a number of other European countries -- although often rather quietly. An international community of scientists has arisen who are willing to risk their reputations by engaging in this work, and who gather regularly at conferences and seminars.
It should be emphasized that although hundreds of scientific experiments, carried out independently in scientific laboratories around the world, continue to provide evidence for the existence of cold fusion, these results remain curiously sporadic in character and (as far as I know) cannot yet be reproduced in a reliable manner. Evidently the exact conditions under which the cold fusion phenomenon occurs – assuming that it really exists – are not sufficiently understood. On this background, widely circulated claims that cold fusion reactors are already operating in the basements of maverick inventors are highly implausible.
In my view the amount and variety of experimental evidence in favor of cold fusion are so enormous, that it is virtually impossible for an unbiased scientist to reject the conclusion that some sort of nuclear reactions are actually taking place in at least in some of the experiments. The fact that the effect occurs sporadically is irrelevant, as far as that conclusion is concerned. It is also irrelevant that the effect appears to contradict present-day knowledge of nuclear physics. Reality is reality. If an overwhelming amount of evidence demonstrates that something is happening, then we must accept this, whether it fits our theories or not. We should welcome this anomaly as an opportunity to develop our knowledge further. Maybe it will even lead us to a scientific revolution.
In the meantime new facts have emerged which indicate that the phenomenon of cold fusion is by no means so far-fetched as it first appeared, and may even become understandable on the basis of existing principles of nuclear physics, if certain habitual over-simplifications are abandoned.
I would like especially to call attention to experimental and theoretical research carried out over the last 10 years by an international team under the leadership of the Polish nuclear physicist Konrad Czerski (see references below). The results are relevant not only to cold fusion, but also to the understanding of nuclear reactions occurring in the super-dense environment in the cores of stars and possibly also giant planets.
Czerski’s team has been investigating the characteristics of nuclear reactions when they take place inside a crystalline material. For this purpose they use specially-designed accelerator systems to generate high-current beams of deuterium ions having sharply-defined energies in the range of 10 keV (and in the future even less than 1 keV), which is much smaller than the energies commonly used in nuclear physics experiments. The deuterium beam irradiates a metal target which has previously been “loaded” with deuterium under very high pressure, giving rise to collisions between deuterium ions from the beam and ions within the crystalline lattice. Fusion reactions are detected and analyzed by an advanced detector system.
Remarkably, the experiments reveal that rate of fusion reactions (the so-called reaction cross-section) in the crystal is many orders of magnitude larger than it would be if the ion collisions took place in empty space. There are also significant differences in the so-called branching ratio and other characteristics of the reactions. These effects depend strongly on the composition and structure of the crystal, and can be reproduced in a consistent manner.
The huge enhancement in the rate of fusion reactions can be explained in part by so-called “electron screening”: negatively-charged electrons, present at high density in the crystal, can “cancel out” part of the repulsive force between the positive deuterium ions, thereby lowering the so-called Coulomb barrier and greatly increasing the probability for fusion reactions to take place. This effect is particularly large at low ion energies. Theoretical estimates indicate, however, that the mechanism of “electron screening” in the crystal can explain only part of the effect. Czerski and his colleagues suggest that the additional increase in the fusion rate may be due to a resonance effect involving a specific excited state of the so-called compound nucleus that is formed when two deuterium nuclei come sufficiently near to each other. Further work will be needed to distinguish the two effects and to discover the suspected resonant state.
If this hypothesis is correct then it could possibly explain why, under certain conditions, the emission of significant amounts of high-energy radiation would be suppressed according to the conservation laws of nuclear physics. The dependence of the enhancement effect on sharply-defined nuclear resonances as well as details of the crystalline structure (including crystal defects) might help to explain why cold fusion experiments, in which the energies of the ions are poorly defined, have yielded inconsistent results. This suggests also that the realization of cold fusion as a commercial energy source, if it turns out to be feasible, will not be so simple as some people expect.
Without going into further technical details, I want to point out a general lesson. The popular mental image of particles as tiny “billiard balls” and of nuclei as clumps of billiard balls, is very far from reality. Even the so-called “building blocks” of atomic nuclei – protons and neutrons – are extraordinarily complex entities. The enormous complexity of particles, nuclei and nuclear reactions, and the impossibility of carrying out exact calculations in most cases, has induced physicists to rely on highly simplified models. Moreover most of our empirical knowledge about the details and parameters of even the simplest fusion reactions has been obtained from experiments made at high energies, and not enough attention has been given to lower energies. It is no exaggeration to say that the physics of these reactions has only begun to be explored.
Whatever may be the future of cold fusion, its discovery has opened up an exciting new branch of science: Solid State Nuclear Physics.
(References: K. Czerski et al.,“New Accelerator Facility for Measurements of Nuclear Reactions at Energies below 1 keV” Acta Physica Polonica B, Vol. 45, 2014; K. Czerski et al. “Screening and resonance enhancements of the 2H(d, p)3H reaction yield in metallic environments”, EPL, 113, January 2016).