Antimatter Kept Stable For Record Time

New Record: Antimatter trapped

and kept stable for 15 minutes

Physicists at CERN in Switzerland have been able to trap the simplest element of antimatter, antihydrogen, for more than 15 minutes in a magnetic device roughly similar to a capacitor. These researchers were able to trap antihydrogen last year, but the material lasted for less than two tenths of a second. The magnetic trap extends the life of the particles more than 5,000 times, as noted in a study published online June 5 in Nature Physics (itself part of the same publishing group as Scientific American).

Antihydrogen is made from a particle of antiproton with a positron, the counterparts of hydrogen. But such particles tend to mutually annihilate each other almost immediately. Antihydrogen is not easy to confine because it is not affected by electric fields, which are useful in steering charged antiparticles such as antiprotons. This experiment used superconducting magnets to trap antihydrogen instead.

Isolating antihydrogen and testing it is useful for physicists because the properties, once studied, provide new scientific knowledge. Is antihydrogen affected by gravity the same way that hydrogen is? Why did matter "win out" in the formation of the universe instead of antimatter? Clifford Surko, a physicist at the University of California at San Diego, wrote a commentary accompanying their new study in Nature Physics. Between matter and antimatter, "There’s got to be an asymmetry somewhere, so that’s a long-term goal," he wrote.

Jeffrey Hangst of Aarhus University in Denmark, spokesperson for the group at CERN, looks forward to performing initial studies that will irradiate the anti-atoms with microwaves in an attempt to flip the spin of the particles. Since the antimatter lasts for 15 minutes, this is time for the atoms to decay into their lowest-energy state (a "ground state"), rather than the excited states in which they are formed. "They’re fragile, and for really high-precision measurements of antihydrogen you need them in the ground state," Surko says.

Hangst said that another big improvement was increasing the number of antihydrogen atoms that become trapped magnetically. "What was tricky here was not keeping them but trapping enough of them to do the experiment. The big technological step here is we’re much better now at trapping them at all."

The trapping is far from perfect – for each antiatom confined in the trap, thousands escape. Only seven antihydrogen atoms were detected in sixteen trapping experiments. The detection is achieved by shutting off the magnets and watching for matter-antimatter annihilations along the walls of the trap.

A competing experiment at CERN called "ATRAP" has sought to produce larger numbers of antihydrogen at a less excited state, but it has yet to achieve results. Work continues on this alternative.

-- summarized by the blog author from the June 5, 2011 Scientific American article by John Matson online at http://www.scientificamerican.com/article.cfm?id=antiatoms-alpha-1000-seconds