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Precision Physics of Antiatoms: Berkeley Lab Physicists Bound the Charge of Antihydrogen

Chukman image charge annihilation Thumbnail

Hydrogen is a neutral atom. Its single electron orbits a single proton, and the net effect is no electrical charge. But what about hydrogen’s antimatter counterpart, antihydrogen? Made of a positron that orbits an antiproton, the antihydrogen atom should be neutral too. Various results have indicated as much, but because the charge of antiatoms is

Does Antimatter Fall Up or Down?

Theory and observations support the view that antimatter experiences gravity just as ordinary matter does, but the evidence so far has been indirect. Indeed, some theorists speculate that antimatter is antigravitational, that it may fall “up” instead of “down.” Led by Berkeley Lab physicists, the ALPHA Collaboration at CERN has made direct measurements of the gravitational mass of atoms of antihydrogen, testing how they fall and in what direction.

The First Spectroscopic Measurement of an Anti-Atom

Like ordinary hydrogen, a single electron orbiting a proton nucleus, antihydrogen is the simplest of atoms, a single positron (antielectron) orbiting a single antiproton. CERN’s ALPHA experiment was first to trap antihydrogen in a magnetic bottle, using a superconducting octupole magnet. (Images by Chukman So, copyright © 2011 Wurtele Research Group. All rights reserved.)

Scientists at Lawrence Berkeley National Laboratory have played leading roles in designing and operating ALPHA, the CERN experiment that was the first to capture and hold atoms of antihydrogen, a single antiproton orbited by a single positron. Now, by measuring antihydrogen’s hyperfine structure, ALPHA has achieved another first in antimatter science with the very first measurements of the energy spectrum of an anti-atom.

ALPHA Stores Antimatter Atoms Over a Quarter of an Hour – and Still Counting

An artistic representation of the ALPHA neutral antimatter trap, suggesting the nature of the ALPHA apparatus as a container for antihydrogen. (Chukman So,  copyright © 2011 Wurtele Research Group. All rights reserved.)

Physicists in Berkeley Lab’s Accelerator and Fusion Research Division are key members of the international ALPHA Collaboration at CERN in Geneva, which has succeeded in storing a total of 309 antihydrogen atoms, many of them for as long as 1,000 seconds (almost 17 minutes) and some for much longer — more than enough time to perform meaningful scientific experiments on confined anti-atoms.