Anti-Hydrogen Atoms Detected in a Penning-IOFFE Trap

The Antiproton Trap Collaboration (ATRAP) working at CERN has succeeded in detecting, for the first time, the presence of anti-hydrogen atoms (each made of a positron and an anti-proton) in the heart of a combined Penning-Ioffe trap. Both types of trap combine electric and magnetic fields to hold charged particles and neutral particles with magnetic moments. Both traps play an important role: the Penning trap is needed to hold and control the positrons and antiprotons enough so that they can join into the antimatter counterpart of hydrogen atoms, while the Ioffe trap is needed to trap those atoms once they’re made, in order to carry out high-precision spectroscopic studies.

Producing and then cooling anti-protons (created in powerful collisions at energies of billion of electron volts and then slowed in stages to energies of milli- or micro-eV) is hard to do in the first place, much less combining them with positrons from a radioactive source. Some scientists feared that it might be impossible to hold the positrons and antiprotons long enough to produce anti-atoms when a Ioffe for neutral atoms was in place, but this new development dispels that worry. Gerald Gabrielse, head of the ATRAP team (<http://hussle.harvard.edu/~atrap/>) says that they do not yet have evidence of trapped anti-atoms, only that anti-atoms are being produced; indeed the number of anti-atoms actually goes up when the Ioffe trap is turned on. (Gabrielse et al., Physical Review Letters)