Later this month, the U.S. Department of Energy will receive a report from a panel of experts on the prospects for cold fusion--the supposed generation of thermonuclear energy using tabletop apparatus. It's an extraordinary reversal of fortune: more than a few heads turned earlier this year when James Decker, the deputy director of the DOE's Office of Science, announced that he was initiating the review of cold fusion science. Back in November 1989, it had been the department's own investigation that determined the evidence behind cold fusion was unconvincing. Clearly, something important has changed to grab the department's attention now.
The cold fusion story began at a now infamous press conference in March 1989. Stanley Pons and Martin Fleischmann, both electrochemists working at the University of Utah in Salt Lake City, announced that they had created fusion using a battery connected to palladium electrodes immersed in a bath of water in which the hydrogen was replaced with its isotope deuterium--so-called heavy water. With this claim came the idea that tabletop fusion could produce more or less unlimited, low-cost, clean energy.
In physicists' traditional view of fusion, forcing two deuterium nuclei close enough together to allow them to fuse usually requires temperatures of tens of millions of degrees Celsius. The claim that it could be done at room temperature with a couple of electrodes connected to a battery stretched credulity [see photo, "To good to be true?"].
But while some scientists reported being able to reproduce the result sporadically, many others reported negative results, and cold fusion soon took on the stigma of junk science.
Today the mainstream view is that champions of cold fusion are little better than purveyors of snake oil and good luck charms. Critics say that the extravagant claims behind cold fusion need to be backed with exceptionally strong evidence, and that such evidence simply has not materialized. "To my knowledge, nothing has changed that makes cold fusion worth a second look," says Steven Koonin, a member of the panel that evaluated cold fusion for the DOE back in 1989, who is now chief scientist at BP, the London-based energy company.
Because of such attitudes, science has all but ignored the phenomenon for 15 years. But a small group of dedicated researchers have continued to investigate it. For them, the DOE's change of heart is a crucial step toward being accepted back into the scientific fold. Behind the scenes, scientists in many countries, but particularly in the United States, Japan, and Italy, have been working quietly for more than a decade to understand the science behind cold fusion. (Today they call it low-energy nuclear reactions, or sometimes chemically assisted nuclear reactions.) For them, the department's change of heart is simply a recognition of what they have said all along--whatever cold fusion may be, it needs explaining by the proper process of science.
The first hint that the tide may be changing came in February 2002, when the U.S. Navy revealed that its researchers had been studying cold fusion on the quiet more or less continuously since the debacle began. Much of this work was carried out at the Space and Naval Warfare Systems Center in San Diego, where the idea of generating energy from sea water--a good source of heavy water--may have seemed more captivating than at other laboratories.
Many researchers at the center had worked with Fleischmann, a well-respected electrochemist, and found it hard to believe that he was completely mistaken. What's more, the Navy encouraged a culture of risk-taking in research and made available small amounts of funding for researchers to pursue their own interests.
At San Diego and other research centers, scientists built up an impressive body of evidence that something strange happened when a current passed through palladium electrodes placed in heavy water.
And by 2002, a number of Navy scientists believed it was time to throw down the gauntlet. A two-volume report, entitled "Thermal and nuclear aspects of the Pd/D2O system," contained a remarkable plea for proper funding from Frank Gordon, the head of navigation and applied science at the Navy center. "It is time that this phenomenon be investigated so that we can reap whatever benefits accrue from scientific understanding. It is time for government funding agencies to invest in this research," he wrote. The report was noted by the DOE but appeared to have little impact.
Then, last August, in a small hotel near the Massachusetts Institute of Technology, in Cambridge, some 150 engineers and scientists met for the Tenth International Conference on Cold Fusion. Conference observers were struck by the careful way in which various early criticisms of the research were being addressed. Over the years, a number of groups around the world have reproduced the original Pons-Fleischmann excess heat effect, yielding sometimes as much as 250 percent of the energy put in.
To be sure, excess energy by itself is not enough to establish that fusion is taking place. In addition to energy, critics are quick to emphasize, the fusion of deuterium nuclei should produce other byproducts, such as helium and the hydrogen isotope tritium. Evidence of these byproducts has been scant, though Antonella de Ninno and colleagues from the Italian National Agency for New Technologies Energy and the Environment, in Rome, have found strong evidence of helium generation when the palladium cells are producing excess heat but not otherwise.
Other researchers are finally beginning to explain why the Pons-Fleischmann effect has been difficult to reproduce. Mike McKubre from SRI International, in Menlo Park, Calif., a respected researcher who is influential among those pursuing cold fusion, says that the effect can be reliably seen only once the palladium electrodes are packed with deuterium at ratios of 100 percent--one deuterium atom for every palladium atom. His work shows that if the ratio drops by as little as 10 points, to 90 percent, only 2 experimental runs in 12 produce excess heat, while all runs at a ratio of 100 percent produce excess heat.
And scientists are beginning to get a better handle on exactly how the effect occurs. Stanislaw Szpak and colleagues from the Space and Naval Warfare Systems Command have taken infrared video images of palladium electrodes as they produce excess energy. It turns out that the heat is not produced continuously over the entire electrode but only in hot spots that erupt and then die on the electrode surface. This team also has evidence of curious mini-explosions on the surface.
Fleischmann, who is still involved in cold fusion as an advisor to a number of groups, feels vindicated. He told the conference: "I believe that the work carried out thus far amply illustrates that there is a new and richly varied field of research waiting to be explored." (Pons is no longer involved in the field, having dropped from view after a laboratory he joined in southern France ceased operations.)
For Peter Hagelstein, an electrical engineer at MIT who works on the theory behind cold fusion and who chaired the August 2003 conference, the quality of the papers was hugely significant. "It's obvious that there are effects going on," he says. He and two colleagues believed the results were so strong that they were worth drawing to the attention of the DOE, and late last year they secured a meeting with the department's Decker.
It was a meeting that paid off dramatically. The review will give cold fusion researchers a chance--perhaps their last--to show their mettle. The department has yet to decide just what will be done and by whom. There is no guarantee of funding or of future support. But for a discipline whose name has become a byword for junk science, the DOE's review is a big opportunity.