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Cold Fusion
Cold fusion
Cold fusion refers to a
nuclear fusion process which occurs at or near room
temperature, as compared to conventional nuclear fusion, which requires a
very hot (100 million degrees)
plasma. There are a number of such processes which are under investigation
and are generally considered to be scientifically reputable, although none of
them have reached anything close to
breakeven, including
muon-catalyzed fusion and
bubble fusion. However, cold fusion is often used to refer to a claimed
particular mechanism which is not considered viable by most scientists.
On
March 23,
1989,
Stanley Pons and
Martin Fleischmann at the
University of Utah claimed to measure a production of heat that could only
be explained by a nuclear process. Steven Jones at
Brigham Young University did not observe heat but claimed to observe
neutron emission that would also indicate a nuclear process. The claims were
particularly astounding given the simplicity of the equipment, just a pair of
electrodes connected to a battery and immersed in a jar of
heavy water. The immense beneficial implications of the Utah claims, if they
were correct, and the ready availability of the required equipment, led
scientists around the world to attempt to repeat the experiments within hours of
the announcement.
This claim was surrounded by a lot of
media attention and excitement which brought the phrase cold fusion into
popular consciousness. A few months after the initial cold fusion claims, the
Energy Research Advisory Board (part of the
US Department of Energy) formed a special panel to investigate cold fusion
and the scientists in the panel found the evidence for cold fusion to be
unconvincing.
[1]
The most common experiments involve a metal
electrode (usually
palladium or
titanium) which has been specially treated so that it is saturated with
deuterium and placed in an
electrolytic heavy water solution. The experimenters saw extra heat coming
from this system which was not readily explained by the electrolytic reaction
itself. Although some experiments claimed to see fusion products (tritium,
helium, or neutrons) the amount of detected fusion products did not match
what was necessary to explain the amount of excess heat. The initial
announcement by Pons and Fleischmann in March 1989 exhibited the discrepancy
between heat and fusion products in sharp terms. Namely, the level of neutrons
they claimed to observe was 109 times less than that required if
their stated heat output were due to fusion.
The idea that palladium or titanium might catalyze fusion
stems from the special ability of these metals to absorb large quantities of
hydrogen (or deuterium), the hope being that deuterium atoms would be close
enough together to induce fusion at ordinary temperatures. The special ability
of palladium to absorb hydrogen was recognized in the
nineteenth century. In the late
nineteen-twenties, two
German scientists, F. Paneth and K. Peters, reported the transformation of
hydrogen into helium by spontaneous nuclear catalysis when hydrogen is absorbed
by finely divided palladium at room temperature. These authors later
acknowledged that the helium they measured was due to background from the air.
In
1927,
Swedish scientist J. Tandberg claimed that he had fused hydrogen into helium
in an electrolytic cell with palladium electrodes. On the basis of his work he
applied for a Swedish patent for "a method to produce helium and useful reaction
energy". After deuterium was discovered in
1932,
Tandberg continued his experiments with heavy water. Due to Paneth and Peters'
retraction, Tandberg's patent application was denied eventually.
In fact, even though palladium can store large amounts of
deuterium, the deuterium atoms are still much too far apart for fusion to occur
in normal theories. Actually, deuterium atoms are closer together in D2 gas
molecules, which do not exhibit fusion. The closest deuterium-deuterium distance
between deuterons in palladium is approximately 0.17 nanometers. This distance
is large compared to the bond distance in D2 gas molecules of 0.074 nanometers.
There are still a few people trying to do cold fusion.
Robert L. Park (2000) gives a decent account of cold fusion
and its history which represents the perspective of the mainstream scientific
community.
Cold fusion is also sometimes used to refer
to the well established and reproducible process of
muon-catalyzed
fusion in which atoms consisting of
protons and muons (which are heavy
electrons) undergo fusion at low temperatures. In this method of fusion, the
muons shield the charges of the protons allows the protons to be close enough to
undergo fusion. As presently understood, muon catalysis will not produce net
energy in competition with the power required to produce the muons (too few
reactions before the muon sticks to a helium nucleus made in the process).
Another table top candidate for fusion is through an extreme
form of
sonoluminescence, is often called
bubble fusion. Natural bubbles of gas inside a liquid would be made to
expand to near vacuum, and then collapse. The extreme pressures and temperatures
needed for fusion could potentially be reached. Bubble fusion is often
associated with cold fusion due to the use of small room temperature containers
of
acetone (although the fusion process itself would still take place under
localised extreme thermonuclear temperatures and pressures). In 2002
bubble fusion attracted a significant amount of media coverage as controversial
results were published. As the liquid researchers chose heavy acetone (acetone
in which hydrogen atoms had been replaced by heavier deuterium atoms). It was
hoped the deuterium atoms would be fused to form helium, releasing energy.
Unlike the cold fusion results of Pons and Fleishman, the
bubble fusion results were published in a peer reviewed journal, Science.
In July of that same year however researchers from the
University of Illinois claimed they had discovered chemical reactions in the
collapsing bubbles, sapping most of the energy available. Instead of a
temperature of millions of degrees, they calculated the temperature within the
collapsed bubbles would be closer to 20,000 degrees.
Voodoo Science: The Road from Foolishness to Fraud,
by Robert L. Park; Oxford University Press, New York;
ISBN 0195135156; May 2000.
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