The first atoms of antihydrogen – the antimatter counterpart of the simplest atom, hydrogen – were created at CERN in 1995. An atom of antihydrogen consists of an antiproton and a positron (an antielectron), which makes it the simplest antiatom. Unfortunately, this does not make it any easier to produce in the lab. It was a difficult task both for the physicists and for the operation team at CERN’s Low Energy Antiproton Ring (LEAR) – where the discovery of antihydrogen took place. The researchers allowed antiprotons circulating inside LEAR to collide with atoms of a heavy element. Any antiprotons passing close enough to heavy atomic nuclei could create an electron-positron pair; in a tiny fraction of cases, the antiproton would bind with the positron to make an atom of antihydrogen.
However, the fleeting existence of the antiatoms meant that they could not be used for further studies. Each one existed for only about 40 billionths of a second, travelling at nearly the speed of light over a path of 10 metres before it annihilated with ordinary matter. In 2011, ALPHA – an international collaboration currently running experiments at CERN's Antiproton Decelerator facility – succeeded in trapping antihydrogen atoms for 1000 seconds. By precise comparisons of hydrogen and antihydrogen, several experimental groups hope to study the properties of antihydrogen and see if it has the same spectral lines as hydrogen. One group, AEGIS, will even attempt to measure g, the gravitational acceleration constant, as experienced by antihydrogen atoms.
The ACE experiment is testing the use of antiprotons for cancer therapy. From 2016, a facility called ELENA will enable all experiments working at the Antiproton Decelerator to get lower energy and more abundant antiproton beams, making it even easier to produce antihydrogen in large quantities.
Featured updates on this topic
CERN experiment reports sixfold improved measurement of the magnetic moment of the antiproton
ALPHA shows the most accurate measurement yet of the electric charge of antihydrogen atoms in a new Nature paper
In a paper published today in Nature, BASE reports the most precise comparison of the charge-to-mass ratio of the proton to the antiproton
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BASE has kept a shot of antiprotons trapped for more than one year: it is the longest-lived, coldest, known baryonic antimatter object in the Universe
The commissioning of ELENA, a new antiproton deceleration ring, has begun
In September 1995 physicists at CERN synthesised the first antihydrogen atoms, paving the way for today’s growing antimatter research
TEDed and CERN physicist Chloé Malbrunot team up to test the principle of universality of free fall for antimatter
Latest measurements from the AMS experiment unveil new territories in the flux of cosmic rays
ALPHA reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places
The ASACUSA experiment at CERN has succeeded for the first time in producing a beam of antihydrogen atoms
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A ground-breaking ceremony today marked the start of construction of an extension to CERN's antimatter facility