National Geographic : 1984 Mar
industry. In furnaces where wafers of silicon crystal are processed into microcircuits, la ser light beamed into special gases provokes chemical reactions that etch silicon with in tricate circuit patterns, or lace it with "wires" far too fine to see with the naked eye. N ANOTHER FIELD lasers already per form alchemy, the ancient dream of transmuting common substances into precious ones. By separating different atomic forms-or isotopes-of the same ele ment, lasers can enrich ordinary uranium, turning it into valuable fuel for nuclear power reactors. Natural uranium contains chiefly the iso tope U 238 and a scant amount of U 235, whose concentration must be raised in ura nium meant for nuclear fuel. Chemically, U 238 and U 235 atoms all but match, so only a tiny weight difference allows their separa tion by conventional enrichment methods that require huge amounts of electricity or costly mammoth facilities. Far cheaper in energy and money are la sers that separate isotopes by ionizing U 235 atoms in vaporized uranium metal for elec tromagnetic collection. A pilot laser isotope separation plant to purify plutonium opens in 1984, and others to enrich uranium may follow in the 1990s. Scientists worldwide hope before then to show the feasibility of laser fusion-the pro duction of nuclear energy by heating, crush ing, and fusing hydrogen isotopes with laser light. A reactor that could fuse atoms rather than split them for their energy offers much: no risk of explosion, less radioactive waste, and the prodigious energy of an abundant fuel isotope-deuterium-found in the hy drogen of seawater. "Burning a fuel pellet little larger than a grain of sugar frees almost as much energy as a ton of explosives," said Robert McCrory, Jr., director of the Laboratory for Laser En ergetics at the University of Rochester. With him I wandered a football-field-size build ing: a tight fit for Omega, a neodymium glass laser of 12 trillion watts power. Later I watched mirrors split a pulse of Omega's light into 24 beams that entered portholes in a spherical steel target cham ber. In billionths ofa second, they vaporized the outer (Continuedon page 362) Lasers-"A Splendid Light"