TWENTY years to the day after two chemists ignited controversy by announcing signs of 鈥渃old fusion鈥� at a in Utah, a fresh claim by a separate team was made this week, again in Utah. This time the researchers have been careful to avoid the pitfalls that led to the original claims being ridiculed and dismissed out of hand.
In 1989, Martin Fleischmann and Stanley Pons at the University of Utah offered the tantalising prospect of abundant, almost free energy from nuclear fusion reactions that they said they had produced in a simple tabletop set-up. Their claims were dismissed by nuclear physicists, not least because such reactions normally occur only at the high temperatures and pressures found inside stars.
Now Pamela Mosier-Boss and colleagues at the in San Diego, California, are claiming to have found 鈥渟ignificant鈥� evidence of cold fusion. They presented the work on 23 March at the in Salt Lake City, Utah, and have published in the peer-reviewed journal Naturwissenschaften ().
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Using a similar experimental set-up to Fleischmann and Pons, they found what they say are 鈥渢racks鈥� left behind by high-energy neutrons produced in the fusion reaction between deuterium and tritium nuclei. The team used a low-tech particle detector: a plastic called , which they placed in contact with a gold or nickel cathode in an electrochemical cell. After passing a current through the cell for two to three weeks, the team found a small number of 鈥渢riple tracks鈥� in the plastic: three 8-micrometre-wide pits radiating from a point (see diagram).
Mosier-Boss鈥檚 team say the pattern is the result of a high-energy neutron striking the nucleus of a carbon atom inside the plastic and shattering it into three charged alpha particles. As these particles rip through the plastic, they leave the characteristic tracks. No such tracks were seen when the experiment was repeated using normal water rather than heavy water that contains deuterium.
at the Massachusetts Institute of Technology, an expert at interpreting CR-39 tracks produced in conventional high-temperature fusion reactions, supports the team鈥檚 interpretation. 鈥淚 must say that the data and their analysis seem to suggest that energetic neutrons have been produced,鈥� he says, although he points out that their data set is small.
Whether this is the result of a nuclear fusion reaction is more controversial. Because normal chemical reactions do not produce high-energy neutrons, Mosier-Boss suggests they could have been created as a by-product of the fusion of deuterium and tritium nuclei crammed together at the cathode. Some researchers agree. 鈥淚n my view [it鈥檚] a cold fusion effect,鈥� says at MIT, who has studied possible cold fusion mechanisms.
鈥淭he tracks in the detector could be the result of the fusion of deuterium and tritium nuclei鈥�
Others are not convinced. Steven Krivit, editor of , has been following the cold fusion debate for many years and also spoke at the ACS conference. 鈥淭heir hypothesis as to a fusion mechanism I think is on thin ice,鈥� he says. 鈥淭his is an unfortunate distraction from their excellent empirical work.鈥�
Krivit thinks cold fusion remains fantasy. He views Mosier-Boss鈥檚 work as evidence of low-energy nuclear reactions, which he says can be explained by nuclear mechanisms other than cold fusion.