Cold fusion is the term proposed to describe controlled nuclear fusion reactions occurring at or near room temperature. The attainment of cold fusion, with a net release of energy, was announced at a press conference in Salt Lake City, Utah, on March 23, 1989, by B. Stanley Pons of the University of Utah and Martin Fleishman of Southampton University in England. The following day, a paper claiming the achievement of cold fusion at a much lower rate was mailed to the British journal Nature by Steven E. Jones, a professor of physics at Brigham Young University, and a group of his colleagues. The announcement by Pons and Fleishman received worldwide media coverage, but also a great deal of criticism as it did not provide adequate technical details for other scientists to independently verify what was claimed. As the details of the experiment became known, attempts to reproduce it in a number of other laboratories gave inconsistent results. In addition, Pons and Fleishman found it necessary to retract some of their initial claims. To deal with the controversy, the Energy Research Advisory Board of the United States Department of Energy appointed a fact-finding panel. By the end of the year, this panel concluded that there was "no convincing evidence that useful sources of energy would result from" the cold fusion work. Within a few years, the majority of chemists and physicists reached consensus that the Fleishman and Pons experiment had failed to demonstrate the release of fusion energy on a significant scale. While some scientists believe that Jones and others following his approach had demonstrated an interesting new effect, there is currently only limited interest in funding research pertaining to cold fusion as a potential energy source.
Nuclear fusion is the process responsible for the production of heat energy in the sun and other stars. It can be understood using a few basic ideas from nuclear physics. The structure of the nucleus is the result of two different fundamental forces: the long range electrical repulsion which exists between protons, and the short range nuclear strong force which is attractive and of roughly equal strength between protons and protons, protons and neutron and neutrons and neutrons. Just as electrons outside the atom, the protons and neutrons separately occupy set of energy levels within the nucleus, with the number in each level limited by the Pauli exclusion principle. A third fundamental force, the nuclear weak force, allows for neutrons to decompose into a proton plus an electron plus a massless particle called an antineutrino, or a proton, if it has enough energy available, to split into a neutron and a positron plus a massless neutrino. These weak-force induced properties account for the roughly equal number of protons and neutrons in the common elements, since an excess of protons or neutrons requires that the excess particles be in higher energy levels and can spontaneously change into the other type of particle.
In the sun and other stars, hydrogen is fused into helium in a cyclic reaction in which two protons first combine to form a deuteron (heavy hydrogen nucleus), a third proton is added to form a nucleus of helium-3, and then two helium-3 nuclei combine to form helium-4 and release two protons. This reaction occurs only in the core of the sun at a temperature of about ten million degrees Kelvin. The high kinetic energies of the particles in this case are sufficient to allow the particles to approach closely enough to allow the short-range strong force to act. Each day approximately 1.5 x 1019 kJ of energy reaches the earth's surface as a result of the fusion reactions taking place in the interior of the sun. The direct fusion of deuterons is also possible, with three possible outcomes: the formation of a helium-three nucleus and release of a neutron, the formation of a tritium (hydrogen-3) nucleus with the release of a proton, and the direct formation of a helium-4 nucleus with the emission of a gamma ray. Both theoretical and experimental studies indicate that the third possibility occurs with the least frequency and the first two with nearly equal frequency.
The harnessing of fusion energy to replace fossil and nuclear (fission) fuels has been a goal of energy researchers since the 1960s. The main obstacle to controlled thermonuclear fusion had been being able to confine plasma, a mixture of ions and electrons, at the extremely high temperature required for thermonuclear fusion--temperatures hot enough to melt the walls of any container. The cold fusion researchers had in mind another possibility. The tunnel effect of quantum mechanics allows the spontaneous fusion of the two nuclei in a diatomic deuterium molecule, although at an astronomically slow rate. If one of the bonding elect rons is replaced by a muon, an elementary particle with the same charge as the electron and 200 times the mass, the bond is much shorter and tunneling becomes far more probable. Indeed, Steven E. Jones, was a recognized researcher in muon-catalyzed fusion.
The premise behind the cold fusion experiments was that one could achieve a comparable increase in the rate of deuterium fusion by electrochemically driving the nuclei into one of the transition metals known to have a large capacity to absorb hydrogen gas. Palladium, for example, is able to absorb six hydrogen atoms for every ten palladium atoms. The experiment would require energy input to establish the required current in an electrochemical cell, but the energy output could be determined by calorimetry. The initial report by Pons and Fleishman claimed a fourfold return on the energy input and a net production of helium. The experiment did not however, show a significant production of neutrons, as would be expected from the helium-3 producing process, or the level of gamma ray production to be expected with helium-4, and the original claims of heat and helium production were also brought into doubt by subsequent investigation. Many other investigators have elaborated the more careful experiment of Jones, with generally lower estimates obtained for the possible fusion rate. These studies, however, leave open the possibility that some real but as of yet unexplained phenomenon may be at the root of the reported results. It may be several years, perhaps even decades, before all of the experimental research pertaining to cold fusion is explained to everyone's satisfaction. In the meantime small pockets of research are still being conducted at several prominent research laboratories both in the United States and abroad.
This is the complete article, containing 1,071 words
(approx. 4 pages at 300 words per page).
