The notion that cold fusion might be possible burst onto the scene in March 1989. That's when chemists Martin Fleischmann and Stanley Pons, working at the University of Utah, announced that they had run a table-top electrolysis experiment in which a fusion reaction took place, producing more energy than it consumed. A world of endless, virtually free fuel seemed to be in the offing - but not for long. Fleischmann and Pons's results quickly proved elusive in other research labs. The hapless pair were laughed out of mainstream science, and most nuclear physicists since have refused to give the slightest credence to the idea.
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Not everyone gave up on cold fusion, however. Electrochemists Pamela Mosier-Boss and Stanislaw Szpak at the San Diego centre's navigation and applied sciences department were intrigued. Fortunately, so was Gordon, their boss, who provided limited funding for experiments. Mosier-Boss and Szpak have now run hundreds of tests at weekends and during their spare moments, and have published more than a dozen papers in various peer-reviewed journals (New Scientist, 29 March 2003, p 36).
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Typically, these table-top experiments have involved lowering an electrode made of the precious metal palladium into a solution of an inert salt dissolved in "heavy water" - in which a large proportion of the hydrogen atoms are of the element's heavy isotope deuterium. In deuterium, the atomic nucleus contains a neutron in addition to the usual single proton.
When an electric current is passed through the solution, deuterium atoms start to pack into spaces in the palladium's lattice-like atomic framework. Eventually, after a period of days or weeks, there is approximately one deuterium atom for each palladium atom, at which point things start to happen.
Quite what happens or why isn't clear. Whatever it is appears to release more energy, as heat, than the experiment consumes. Proponents of cold fusion claim that the excess energy comes from a nuclear fusion reaction involving the deuterium nuclei.
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the pair have deployed a detector long used by nuclear scientists, in an attempt to come up with convincing evidence that nuclear events are taking place.
That's where Gordon's sliver of polymer comes in. It is made of CR-39, a clear polycarbonate plastic that is commonly used to make spectacle lenses and shatter-proof windows - and which can also record the passage of subatomic particles. The neutrons, protons and alpha particles that spew from genuine nuclear reactions shatter the bonds within the polymer's molecules to leave distinctive patterns of pits and tracks that can be seen under a microscope.
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Mosier-Boss and Szpak say their cells show telltale signs of nuclear reactions, including anomalous amounts of tritium and low-intensity X-rays, just minutes after co-deposition starts. They say the electrode can sometimes become a few degrees warmer than the surrounding solution.
In their latest experiment, Mosier-Boss and Spzak placed wafers of CR-39 against the electrode. When they examined them after running the experiment, they discovered that regions nearest the electrode were speckled with microscopic pits, while those further away were not. A control experiment without any palladium chloride in the solution produced only a few randomly scattered tracks that could be accounted for by background radiation. The researchers have also deliberately inflicted chemical damage on the CR-39: it "looks like fluffy, popcorn-shaped eruptions" on the plastic, Mosier-Boss says, not pits or holes. They are trying to identify which particles might have left the tracks.
Nuclear scientists associated with the project who are well versed in reading CR-39 detectors say the results appear convincing. The pits "exactly mimic typical nuclear tracks in their depth, size, distribution, shape and contrast", says Lawrence Forsley, a physicist who has worked in fusion research for 16 years and is president of JWK Technologies in Annandale, Virginia, one of the San Diego centre's research partners.
"The pits mimic typical nuclear tracks in their depth, size, shape and contrast"Gary Phillips, a nuclear physicist who has used CR-39 detectors for 20 years to capture nuclear signatures and also works for JMK Technologies, is no less enthusiastic. "I've never seen such a high density of tracks before," he says. "It would have to be from a very intense source - a nuclear source. You cannot get this from any kind of chemical reaction."
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Objectors also point to the difficulty of reproducing these results. While Mosier-Boss and Szpak claim they can produce the reaction at will, other labs have struggled to reproduce consistent, if any, results using co-deposition. One researcher who has had some success is Winthrop Williams at the University of California, Berkeley, who has replicated the navy's experiment with CR-39. At a meeting of the American Physical Society in March he reported similar numbers of pits around the negative electrode. "It is encouraging," says Williams. "I have more work ahead of me to precisely understand and interpret what I am observing."
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The science writer and debunker Shawn Carlson, who in the past has done research in nuclear physics, listened to Gordon and Mosier-Boss make their case at the National Defense Industrial Association conference in Washington DC last year. He was not convinced. "A collection of disjoint anomalies is more consistent with bad experimental technique than a great discovery," he says. "It would take independent verification from a number of labs to swing the tide in favour of cold fusion."
The sceptics are not having it all their own way, though. Several respected scientists at universities in the US, Europe and Asia are attempting to replicate the US navy's lab experiments. David Nagel, a physicist and research professor at George Washington University in Washington DC who has followed the cold fusion saga since its inception, reports a growing willingness by the US Department of Energy to consider funding experiments to follow up these tantalising hints.
