Tapping the Force of Fusion, Again

Scientists have long felt that the ideal source of energy would have to be nuclear fusion. It's the same process that powers the sun, and there's something elegant about the notion of two atomic nuclei joining and releasing energy but no radioactive waste. (Nuclear power plants, by contrast, run on fission, in which a large atomic nucleus is split--a far messier process.) For decades, nobody has been able to get fusion power to work. Last week, however, researchers at the University of California in Los Angeles announced in the journal Nature that they had succeeded in achieving fusion on a small scale. Their device may never provide power to cities, but it could yield a range of useful technologies.

The proof of their success is the creation of neutrons, a subatomic particle that is a byproduct of fusion. The last time anyone claimed to have produced fusion, three years ago, it was in a process called "sonofusion," in which collapsing bubbles generate intense heat. That turned out to be a bust when other researchers tried to repeat the experiment and didn't see any neutrons. "Cold fusion"--the idea that fusion energy could be produced by running electricity through water and metal plates--didn't reliably produce neutrons either.

The UCLA team's device is surprisingly low-tech. It relies on a common ingredient of sea water--deuterium--and a common crystal, often used in lasers, called lithium tantalate. The crystal is one of a group of pyroelectric materials, so named because they create electric fields when they change temperature. (A student of Aristotle noticed this when studying the gemstone tourmaline.) The team pumped air out of a narrow cylinder, filled it with deuterium gas--and inserted a chunk of lithium tantalate. They then warmed the device by 25 degrees Celsius, producing 100,000 volts. The voltage caused the gas to break up into positively charged ions (deuterium nuclei, or "deuterons") and electrons. The freed-up deuterons joined up with those in a solid deuterium "'target" inside the device. After only a minute or two, it began emitting neutrons. "You could take it from the freezer and put it on a countertop and get a measurable neutron signal," says team member Brian Naranjo.

The device offers many potential applications. Because it emits X-rays, it could be used to aim the rays directly at a tumor to destroy it, says UCLA physicist Seth Putterman. It could also enable a handheld neutron scanner to identify explosives. The most tantalizing goal, cheap clean energy, is within reach, says UCLA chemist James Gimzewski, another member of the team. Although the device doesn't generate a net output of energy--the scientists used more energy to run the thing than they got out of it--scientists think it's possible, at least in theory, to produce energy by bunching many tiny versions. "If you recover the energy of 5 percent of the deuterium in the ocean, you could power the world for a million years," says Putterman. That sounds easier than drilling for oil in seabeds.