One promising method for creating nuclear fusion is to zap pellets of hydrogen fuel with lasers. To achieve temperatures and pressures high enough to force the hydrogen to fuse into helium, however, scientists have had to build big lasers at considerable expense. Last March a group of physicists at Imperial College in London announced a way to do fusion research with a laser small enough to fit on a tabletop. The trick was to take advantage of the peculiar physics of atomic clusters.
Whereas big laser-fusion devices work by forming a tightly compressed plasma of about a hundred million trillion highly energetic hydrogen atoms, Todd Ditmire and his colleagues squirted an extremely fine mist of xenon into a vacuum chamber, where the xenon atoms hung in clusters—microscopic droplets—of about 2,500 atoms each. Then the researchers fired a sharply focused laser beam into the mist for less than a trillionth of ...
