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Any serious prospect of practical fusion will attract federal research funding. For decades the Government has spent billions of dollars in pursuit of this tantalizing but elusive goal. The first man-made fusion reactions took the form of H-bomb explosions in the 1950s. Scientists then set out to bring that incredible power under control. Their strategy was to confine deuterium, a heavy form of hydrogen, within a "bottle" of magnetic force and heat it to tens of millions of degrees. The nuclei of the atoms, forced close together despite their mutually repellent positive electric charges, would fuse, releasing energy. Elaborated and modified, that is the approach still being taken at such state-of-the-art facilities as Princeton's Plasma Physics Laboratory. But the lab has achieved only brief bursts of fusion at enormous cost. A more recent concept, represented by Livermore's Nova machine, is to take tiny "marbles" filled with deuterium and concentrate 100 trillion watts of laser light on them for a billionth of a second. The deuterium should theoretically fuse and produce energy, but a far more powerful laser would be needed to spark a useful reaction.
Although superhot fusion has always been considered the best way to generate power, physicists have known since the 1950s that the process can take place at room temperature as well. If the electrons in deuterium are replaced with heavier particles called muons, the deuterium nuclei can approach each other more closely and occasionally fuse on their own. This muon-catalyzed fusion has never produced significant amounts of energy.
Yet the thought that cold fusion was possible at all continued to intrigue some scientists, including Pons and Fleischmann. When Pons got his Ph.D. at Southampton in 1978, Fleischmann was his department head. They became close friends and collaborators after Pons graduated, and remained so when he settled at Utah. One day in 1984 Pons and Fleischmann had a sudden idea for a new way to achieve cold fusion. The brainstorm came, Pons says, during a hike up Millcreek Canyon, near his home in Salt Lake City. He and Fleischmann were puzzling over the peculiar properties of certain metals, like palladium, that are known to absorb huge quantities of hydrogen gas. In the presence of an electric field, the chemists had noticed, deuterium nuclei appeared to be unusually free to move around within palladium's latticework of atoms. They speculated that the nuclei might even come close enough together to make nuclear fusion more likely.
"We came down from the hike," recalls Pons, "and then we stood around the table in my kitchen, had a couple of Jack Daniel's and started drawing pictures." Their experiments resembled nothing more than the simple electrochemical cells often entered in high school science fairs: two metal electrodes immersed in a bath of water laced with mineral salts and connected to a power supply. The only differences were that one of the electrodes was made of palladium and the water was heavy water, or deuterium oxide (chemical formula D2O), rather than ordinary H2O.