PARIS--Scientists at CERN, the European laboratory for particle physics, near Geneva were the first to create antiatoms. Now they are racing to perform in-depth studies of the exotic material, which so far has existed only ephemerally in the lab. But antimatter has an annoying habit of winking out of existence when it encounters ordinary matter, so before studying it, scientists have to make it stand still. Yesterday, CERN announced that it had found funding for a machine to do just that: an antiproton decelerator, which should corral antimatter in quantity starting in spring 1999, enabling scientists to ferret out any fundamental differences between matter and antimatter.
The antimatter in question is antihydrogen--an antiproton and a positron, the electron's antimatter counterpart. CERN scientists coaxed the first antiatoms to form in September 1995 and quickly began dreaming of experiments to compare antihydrogen to ordinary hydrogen. Any differences could force them to rethink tenets of the symmetry between matter and antimatter, which underlies basic physical theories. But newly created antiatoms move too fast for study, and the antimatter tap dried up completely last December, when CERN's facility for generating antiprotons--the Low-Energy Antiproton Ring (LEAR)--was shuttered to save money for the construction of the multibillion-dollar Large Hadron Collider.
But now countries including Denmark, Germany, Italy, Japan, Poland, and the United States have come to the rescue with a pledge to contribute $7 million to CERN to build a machine to trap antiatoms. The plan is to transform LEAR--which produces and stores antiprotons--into an antiproton decelerator, which can cool the antiprotons as well, making them easier to handle. Japan will toss in an additional $10 million to help fund experiments on the new machine.
Designers of the machine face a thorny problem. "Normally at CERN, we have particles at rest and accelerate them, and here we go the other way," says CERN physicist John Eades. "It's much more difficult to slow things down than to speed them up." Eades says the plan is to use laser beams to slow antiatoms and then trap them in a vacuum. The CERN team should be able to trap a few thousand antiatoms every hour, bottling them up for weeks or even months, so that scientists can perform studies such as the effects of gravity on antimatter. Says antiproton researcher Gerald Gabrielse of Harvard University, "If it wasn't for this facility, [CERN's antimatter research] would just stop."