Science: Frail Lawrencium

During their wartime race to build the world’s first Abomb, U.S. scientists urgently needed one vital component: a chemical element that was fissionable (explosive) but not so radioactive that it would disintegrate before the big bang was touched off. The bomb builders found what they wanted at the University of California’s famed Radiation Laboratory at Berkeley, where Drs. Glenn Seaborg and Edwin McMillan had put together some synthetic plutonium, element 94. Until then, plutonium was no more than a lab curiosity, but it proved to be properly fissionable, and it was so slightly radioactive that only half of it would disintegrate in 24,100 years.

Since then, Radiation Lab scientists have gone right on adding to the table of elements. By last week they were up to No. 103. But the job is getting increasingly difficult; the newest element was so frail that it decayed almost before anyone recognized that it was around. It was manufactured, explained a lab team (Albert Ghiorso, Torbjorn Sikkeland, Almon E. Larsh and Robert M. Latimer), by coating thin nickel foil with a circular film of artificial californium (element 98) only one-tenth of an inch in diameter. Placed in a container filled with helium gas, this tiny target was bombarded by a beam of boron nuclei from the lab’s heavy-ion linear accelerator. Most of the boron bullets missed, but a few scored a bull’s-eye on californium nuclei. Atoms formed by the combination of californium and boron bounced off the nickel foil, were slowed by collision with helium atoms and were picked up by a copper conveyor belt. At intervals, an automatic device moved the copper belt a short distance, bringing the newly created atoms close to a series of silicon radiation detectors. About five times each hour the detectors signaled the capture of an alpha particle charged with 8,600,000 electron volts of energy. Nuclear theory predicts that this is just the particle that would be emitted during the disintegration of element 103. The scientists estimated its half-life as eight seconds, and they named it lawrencium, after Ernest Lawrence, founder of their laboratory.

Today, element 103 and its short-lived relatives are of interest only to theoretical physicists. They have no known practical value—but neither did plutonium when it was first manufactured at Berkeley more than 20 years ago.

The contrasting names of the four men who created element 103 are characteristic of U.S. science, which wears its “democracy of the intellect” mantle with a casual air and generally opens its door to everyone regardless of national, racial, religious or social background.

Two of the Berkeley element makers—Almon Larsh, 32, and Robert Latimer, 26—are native Californians. Larsh, the son of a traveling salesman from Oklahoma, graduated from Caltech as an electrical engineer. Chemist Latimer, a Berkeley graduate, was born with a silver test tube in his mouth: his father, Wendell Latimer, was a famous chemist and head of Berke ley’s department of chemistry. But the distinction brought young Robert no favors at the Radiation Lab. His own scientific skill earned him the right to handle the intricate machinery with which new elements are manufactured.

Chemist Torbjorn Sikkeland, 37, was born in Norway and educated at the University of Oslo. In 1957 he came to Berkeley as an exchange scientist and won a permanent place on the Radiation Lab’s cosmopolitan staff. He is the only one of the four with a Ph.D. But the lack of an advanced degree is no handicap to the others; top-rank laboratories admit that doctorates are nice decorations, but the lab directors know only too well that the degrees often mean little more than three extra years of unprofitable study.

The fourth element maker, Albert Ghiorso, 45, has a Berkeley B.S. in electrical engineering, but he got into longhair physics by a back door. Son of a Vallejo, Calif, riveter, he went to work for a local electronics manufacturer and designed a successful commercial Geiger counter. While selling and servicing his product, he came in contact with the Radiation Lab, was fascinated, and got a job there. Working with top scientists, Ghiorso listened hard, and in the informal classroom he absorbed a higher education in higher physics. “I grew up with atomic energy,” he says lightly.