Antihydrogen

Antihydrogen, the antimatter counterpart of hydrogen. The nucleus consists of an antiproton, the nuclear envelope of a positron.

History of antihydrogen production

End of 1995, succeeded at CERN in Geneva for the first time to produce some atoms of antihydrogen. The working group under Walter Oelert from Forschungszentrum Jülich put to an antiproton as a core with a positron together. In the following two years and improved researchers repeated at Fermilab in the U.S. the experiment.

Normal hydrogen ( an atom and an element ) consists of a proton as the core and the elementary electron as an outer shell. For each elementary an antiparticle exists with the property to be reversed electrically charged. An electron has a single negative electronic charge. Its antiparticle, the positron, carries a positive elementary charge.

Antiparticles occur in the normal nature rare, since they convert upon contact with particles in radiation and / or other particle-antiparticle pairs (see annihilation). They are produced artificially in particle accelerators, for example, with a very large technical effort. Therefore, it is a phenomenon that when two antiparticles can be combined to form an anti- atom. Physicists speculate for a long time about whether anti- atoms behave like normal matter. This question can only be answered, however, if you have enough anti- atoms to measure their spectra, so the wavelengths of radiated by them or absorbed light.

The particles produced at CERN and Fermilab were "hot" too: They were moving so fast that they were unsuitable for spectroscopic studies. 2002 was the two international working groups at CERN to produce the experimental facilities ATRAP and ATHENA antihydrogen in large quantities ( about 50,000 atoms). The ATHENA working group in the beaten under the leadership of the CERN physicist Rolf Landua the ATRAP Working Group ( under Gerald Gabrielse ) "race " to the detection of cold antihydrogen for a few weeks.

A storage in a magnetic trap, a modified Ioffe trap for further studies at temperatures of a few degrees above absolute zero succeeded in November 2010, an international research group ALPHA Jeffrey Hangst of the University of Aarhus at CERN. 38 antihydrogen atoms could be studied for 172 ms. In 2011, it was possible to save 309 antihydrogen atoms for 1,000 seconds ( about 16 minutes). The first measurement of a transition in antihydrogen was published in 2012 by the same group.

Storing anti-hydrogen in a neutral trap is necessary to enhance the anti atoms such as laser cooling or by sympathetic cooling ( cooling other atoms or ions that serve as a coolant) to temperatures of a few milli- Kelvin or even to cool micro Kelvin and then high-resolution perform laser spectroscopy on antihydrogen. The goal of laser spectroscopy is a measurement of the 1S- 2S line with a comparable resolution, as achieved in the laboratory of Theodor W. Hänsch of hydrogen. By comparing the 1S- 2S transition frequency in hydrogen and antihydrogen I test the CPT theorem, a cornerstone of modern physics.

Another goal is the accurate assessment of gravitational theories. Since antimatter has positive mass in the sense of general relativity, it is assumed that it behaves like ordinary matter in the gravitational field. With the electromagnetically neutral antihydrogen atoms can in principle the test more accurate than with charged particles, because their electromagnetic interaction is much stronger than the gravitational and would interfere with these measurements. To verify this, including the AEGIS experiment at the Antiproton Decelerator at CERN has been developed. This is currently (2013 ) still in the preparation phase.