Share this article

print logo

An improbable catch ; Scientists briefly trap a form of antimatter

In Dan Brown's novel "Angels and Demons," villains try to use antimatter generated at CERN (the European Organization for Nuclear Research) to blow up the Vatican. The story is far-fetched, to be sure, but scientists at CERN have now figured out how to trap one type of antimatter -- elusive antihydrogen atoms -- according to research published online in the journal Nature.

The amount of antihydrogen the researchers stored -- 38 atoms, each held for just about two-tenths of a second -- isn't enough to power a 100-watt light bulb for even half a nanosecond, much less blow up a building. But once the new procedure is fine-tuned, scientists should be able to create enough of the stuff to conduct a long-awaited test of one of the fundamental theories of particle physics, said Jeffrey Hangst, a physics professor at Denmark's Aarhus University and the lead author of the study.

Theorists believe the Big Bang produced equal parts of matter and its opposite, antimatter. When the two came in contact they should have canceled each other out, leaving behind only a burst of energy.

The universe, however, is full of matter, whereas antimatter doesn't seem to exist in nature, a fact that has had physicists scratching their heads for decades and wondering if their theories are correct. If scientists, through studying the antimatter they now know how to make, were to find that antimatter is somehow fundamentally different from matter, it might help explain why this imbalance exists.

Hangst said his team would like to shine a laser at the stored antihydrogen atoms to see if they behave the same way hydrogen atoms do.

The Standard Model of particle physics predicts that hydrogen and antihydrogen atoms should be identical, he said. "If they're not, everything needs to be re-examined, and textbooks need to be rewritten," he added.

Scientists at CERN, including some affiliated with a rival research team, have been generating antihydrogen atoms in vacuum chambers since 2002. But until now, trapping those atoms has been impossible. As soon as the antihydrogen atoms touch matter -- including the walls of the device in which they're made -- they disappear.

It took Hangst and his team five years to figure out a way to cool the the antihydrogen atoms down to 0.5 degrees Kelvin, just a half-degree above absolute zero, the lowest temperature theoretically possible. Once the atoms were in this low-energy state, the researchers were able to keep them away from the walls of their container by catching them in a kind of "magnetic bowl" that keeps them suspended in the vacuum in which they're created.

The CERN scientists still need to increase the number of antihydrogen atoms they can produce, cool and store before they can start analyzing the antihydrogen with lasers, Hangst said.

Asked how long before that experiment might be under way, he said, "My stock response is that it should take five years." And, he added, "I've been saying that for 18 years."

***

Antimatter breakthrough

Top: An image taken by the ALPHA annihilation detector shows untrapped antihydrogen atoms annihilating on the inner surface of the trap.

The events are concentrated at the electrode radius of about 22.3mm.

Bottom: The electrodes (gold) for the ALPHA Penning trap being inserted into the vacuum chamber and cryostat assembly. This is the trap used to combine or "mix" positrons and antiprotons to make antihydrogen.

There are no comments - be the first to comment