<<http://www.technologyreview.com/articles/wo_hecht042304.asp?p=0>>
Is Cold Fusion Heating Up?
Though their work is dismissed by most physicists, a determined cadre of
scientists is still chasing after what could be an energy jackpot�and
their experiments are producing heat and nuclear byproducts that can't be
otherwise explained.
By Jeff Hecht
April 23, 2004
Fifteen years after the first controversial claims hit the headlines,
cold fusion refuses to die. A small cadre of die-hard advocates argues
that experiments now produce consistent results. The physics
establishment continues to scoff, but some scientists who have been
watching the field carefully are convinced something real is happening.
And now the U.S. Department of Energy has decided that recent results
justify a fresh look at cold fusion.
Fusion of the nuclei of hydrogen atoms powers the sun, and promises
nearly limitless energy on Earth. But fusion is extraordinarily difficult
to tame because nuclei strongly repel each other. The tremendous heat and
pressure inside the sun can overwhelm this repulsion, and thermonuclear
bombs can attain those conditions, fleetingly, on Earth. But building a
fusion reactor that can convert that tremendous heat into useful energy
has posed an immense challenge. After decades of research, the conditions
needed for fusion still can be attained only briefly, and these
experimental fusion reactions produce less energy than is needed to
ignite them.
Physicists were stunned when two University of Utah electrochemists,
Stanley Pons and Martin Fleischmann, claimed in 1989 that they had
achieved nuclear fusion at room temperature. Their experiment packed
deuterium�the stable heavy isotope of hydrogen�into palladium electrodes.
After many hours of operation, they reported that more heat was generated
than a purely chemical reaction could have produced. At first it looked
like Pons and Fleischman might have come up with a revolutionarily easy
way to tap fusion energy, and laboratories around the world rushed to try
the experiment for themselves. The simple-looking experiment proved
virtually impossible to reproduce, however, and within weeks, most
physicists wrote off cold fusion as a mistake�an experimental result that
contradicted the known laws of physics.
Yet the potential of limitless energy lured a band of would-be
revolutionaries who kept on working the problem. Often they found
nothing. Sometimes, however, their experiments appeared to produce more
energy than they expected from chemical reactions; at other times they
detected traces of potential fusion reaction products, suggesting that
some previously unknown physical effects may be at work.
The evidence for "new physics" has been building for years, says Peter
Hagelstein, associate professor of electrical engineering and computer
science at MIT, who chaired the tenth International Conference on Cold
Fusion in Cambridge last August. Experiments performed under properly
controlled conditions reliably produce more heat than standard theory
predicts. Nuclear products show up in about the right amounts to account
for this excess heat. Patterns have emerged that explain previous
anomalies. When Hagelstein saw how pieces of the puzzle were fitting
together at the August meeting, he urged the Department of Energy to
reconsider a field that had been cast out of orthodox science soon after
its birth.
Over the past 15 years, enthusiasts have generated some 3,000 manuscripts
on cold fusion, but very few were ever published in scientific journals.
Many results evaporated under outside examination, and promoters pushed
"free energy" schemes that sounded more like perpetual motion than
physics. Most of those manuscripts "are not helpful," says Hagelstein, a
theorist with wide-ranging interests in optics, energy, and nuclear
physics. But some 50 do show interesting, reproducible effects. "The heat
effect has been replicated many times," Hagelstein. It works only when
deuterium is loaded into palladium cells, and never when normal hydrogen
is used instead of the heavy isotope. Exacting measurements with
heat-measurement instruments have answered criticisms of the original
experiments. Excess heat has been measured beyond what Hagelstein
considers any reasonable doubt.
Experiments that produce excess heat also have yielded helium-4, one
potential product of the fusion of two deuterium nuclei, in amounts that
correlate with the excess heat. Theory predicts that the fusion reaction
should generate 24 million electron volts (MeV) of energy per helium-4
nucleus. An analysis by Michael McKubre of SRI International detected
energy of 31 MeV� a match within the experimental uncertainty of plus or
minus 13 MeV. Skeptics had doubted the reaction was possible, but
Hagelstein says McKubre's analysis of the experiments, reported at last
year's cold fusion meeting, shows that fusion of two deuterium to yield
helium-4 "is not as nutty as it initially seemed."
McKubre has also found that the seeming inconsistency in experimental
heat production arose from differences in the amount of deuterium packed
into the palladium electrode. Whenever the number of deuterium atoms
loaded into the metal matched or exceeded the number of palladium atoms,
excess heat was generated. Palladium loaded with slightly less deuterium
produced inconsistent results, and if the deuterium level was reduced by
a great amount, then no excess heat at all was produced. Deuterium
loading was hard to control and limited by the strength of the metal.
Unfortunately, palladium strength is difficult to predict or control, and
is not improved by purification; indeed, the purest palladium ruptured at
lower loadings, and the highest strength was seen only in one impure
batch.
The growing evidence has convinced fusion physicist George Miley of the
University of Illinois at Urbana-Champaign that "there are important
physical phenomena occurring." Skeptics aren't changing their minds, but
he thinks that previously neutral observers are becoming more receptive
to the possibility that a real phenomenon is occurring in these
experiments. Yet while cold fusion researchers have gone from thinking
they smell smoke to feeling warmth, it's still not clear what's really
going on. "This field is led experimentally. We've got to get the
theories up to where they start helping lead the experiments," Miley
says.
The challenge for theorists like Hagelstein is to fill the yawning gap
between traditional nuclear theory and cold fusion experiments. He
suspects the difficulty lies with "a very powerful approximation" at the
root of 70 years of nuclear physics�that all nuclear interactions occur
between two particles in a vacuum. He thinks that assumption breaks down
in cold fusion, where the interacting particles are tightly packed in a
metal lattice. His idea is that the deuterium nuclei exchange vibrational
energy, or "phonons," with the surrounding palladium atoms. That exchange
could enhance nuclear interactions that would otherwise be vanishingly
small, so that the reactions can occur at the rates implied by cold
fusion experiments. Hagelstein's theory is still in development, but is
reaching a point where he can start making testable predictions�a vital
step toward making cold fusion a credible science. "In time, hopefully,
we'll get more of the puzzle figured out," he says.
A positive Department of Energy review would open the door to badly
needed research support, but big questions remain even if the reality of
the physics can be established. Is the cold fusion effect strong enough
to be used for practical energy production? If it is, it's not likely to
compete directly with hot fusion, says Miley, who works on both. Cold
fusion works on a small scale, so it might find a home in small
distributed power units. Hot fusion's natural home is inside the sun; if
it can be controlled on our planet, it would be inside large reactors
feeding power into the grid.
But those goals are a long ways off. For now, the little community of
cold-fusion researchers hopes it is on the threshold of validation after
15 years of struggle.
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