Researchers get anti-hydrogen for 16 minutes

Long lasting and in the ground state - an important breakthrough for antimatter research

Illustration of Antimatter Trap ALPHA © Wurtele Research Group
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For the first time, physicists have produced anti-hydrogen atoms and not just received them for fractions of a second, but for about 16 minutes. This is one of the most important prerequisites for a closer investigation of antimatter: enough time to carry out experiments. The achievement now presented in "Nature Physics" also allows for the first time to keep an antimatter particle in the ground state, also a prerequisite for meaningful research results.

The ALPHA experiment at CERN basically consists of a superconducting eight-part magnet serving as an atomic trap: In this vacuum chamber, antiprotons from an accelerator ring are mixed with positrons - the antiparticles of the electrons. It creates neutral antihydrogen. The tiny magnetic moments, the spin, these antiparticles keep them floating in the interior of the magnets and do not touch the walls made of matter. Because then matter and its corresponding antiparticles cancel each other out and only energy remains.

Modified detection method extends "captivity"

Exactly this energy has also been used to detect antiparticles: "So far, turning off the magnet was the only way to tell whether we captured an antiatom or not, " explains Joel Fajans of the University of California at Berkeley and a member of the ALPHA collaboration, "When the antiatom hits the wall of the trap, it goes out and that's what tells us we have one. So in the beginning, we've shut down our trap as soon as possible after every antimatter attempt, so we will not miss any. "

Now, however, the researchers have modified their trap to detect the presence of antihydrogen via the interaction of these particles with the photons of light or microwaves. This allows the anti-hydrogen substance to last longer in the magnetic trap - long enough to enable future experiments and measurements on its properties. The experiments have already succeeded in capturing up to three anti-hydrogen particles at once for up to 1, 000 seconds, which corresponds to around 16 minutes.

Anti-hydrogen (above) and hydrogen. In an anti-hydrogen, a positron orbits a negatively charged antiproton. Wurtele Research Group

Prerequisite for first experiments on antimatter now fulfilled

"A thousand seconds is more than enough time to take measurements on a trapped antiatom, " says Fajans. For example, the collaboration has already succeeded in measuring the energy distribution of such an antihydrogen for the first time. "That may not sound very exciting, but it's the first experiment ever conducted on captured antihydrogen atoms, " explains fellow colleague Jonathan Wurtele. display

However, with the long lifespan, the researchers reached another important milestone: "Perhaps the most important part of this result is that these anti-hydrogen atoms must have reached their ground state after one second, " Fajans said. "Thus, these are most likely the first ground state antiatoms ever to be produced." Since nearly all precision measurements of the behavior and properties of matter require this ground state, the ALPHA experiment opens now the way to new experiments with antimatter. Microwave experiments will follow this year, and in 2012 the scientists hope to be able to carry out laser experiments on captured antihydrogen atoms. (Nature Physics, 2011; DOI: 10.1038 / nphys2025)

(DOE / Lawrence Berkeley National Laboratory / University of California - Berkeley, 06.06.2011 - NPO)