first-ever beam of antihydrogen atoms

CERN announced that its ASACUSA experiment has produced the world's first-ever beam of antihydrogen atoms. Such beams will make possible a couple of tests that seek to answer one of the biggest questions in physics: Why is there more matter than antimatter?

"The ASACUSA experiment at CERN has succeeded for the first time in producing a beam of antihydrogen atoms. In a paper published today in Nature Communications, the ASACUSA collaboration reports the unambiguous detection of 80 antihydrogen atoms 2.7 metres downstream of their production, where the perturbing influence of the magnetic fields used initially to produce the antiatoms is small. This result is a significant step towards precise hyperfine spectroscopy of antihydrogen atoms." in CERN Press Office

Antihydrogen for 1000 seconds

(a) A schematic view of the ALPHA trap. Penning trap electrodes are held at ~9 K, and have an inner diameter of 44.5 mm. A three-layer silicon vertex detector surrounds the magnets and the cryostat. A 1 T base field is provided by an external solenoid (not shown). An antiproton beam is introduced from the right, while positrons from an accumulator are brought in from the left. (b) The magnetic field strength in the y-z plane (z is along the trap axis, with z=0 at the centre of the magnetic trap). Green dashed lines in this and other figures depict the location of the inner walls of the electrodes. (c) The axial field profile, with an effective trap length of ~270 mm. (d) The field strength in the x-y plane. (e) The field strength profile along the x-axis. Image credit: ArXiv paper

CERN scientists confine antihydrogen atoms for 1000 seconds

(PhysOrg.com) -- Seventeen minutes may not seem like much, but to physicists working on the Antihydrogen Laser Physics Apparatus (ALPHA) project at the CERN physics complex near Geneva, 1000 seconds is nearly four orders of magnitude better than has ever been achieved before in capturing and holding onto antimatter atoms. In a paper published in arXiv, a team of researchers studying the properties of antimatter, describe a process whereby they were able to confine antihydrogen atoms for just that long, paving the way for new experiments that could demonstrate properties of antimatter that until now, have been largely speculation.

More info: http://arxiv.org/abs/1104.4982

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Trapping antihydrogen

By Physics Today on December 6, 2010 11:51 AM

Are there any unexpected differences between matter and antimatter? The international ALPHA collaboration has taken an important step toward answering that question by constructing an apparatus at CERN that can confine freshly made atoms of antihydrogen, the bound state of an antiproton and a positron, for nearly 0.2 seconds—long enough for the antimatter to be examined spectroscopically. A hot plasma of roughly 104 antiprotons—produced by slamming 26-GeV protons into a metal target—is cooled and introduced into one end of the apparatus, while about 106 low-energy positrons from the decay of radioactive sodium are introduced into the other. Electric fields gently nudge the charged species together in the heart of the device, pictured here, where they mix at cryogenic temperatures and form antihydrogen. If their kinetic energies are low enough—in temperature units, less than 0.5 K—the antihydrogen atoms are held in the grip of a superconducting octupole magnet and solenoidal “mirror” coils that together interact with the atoms’ magnetic moments. When the magnetic fields are abruptly turned off, the atoms are released and their spatial distribution captured by a three-layer silicon detector, which locates the atoms’ annihilations and distinguishes them from events triggered by lone antiprotons and stray cosmic rays. In 335 trial runs, the researchers confirmed that 38 antihydrogen atoms had survived in the trap for at least 172 ms. Although the trapping rate per atom produced is low—about 10−5—the achievement sets the stage for precision spectroscopy and antihydrogen tests of fundamental symmetries and gravitation. (G. B. Andresen et al., Nature 468, 673, 2010.)—R. Mark Wilson Read more at blogs.physicstoday.org

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