A journey into space via CERN
A mere hop, skip and a jump before the long haul into space. On 25 September, the core of the AMS experiment was moved to CERN, a few kilometres from the University of Geneva where it had undergone partial assembly, for the final preparations prior to take-off. By the end of 2008, the AMS experiment will be ready to be launched into space to dock with the International Space Station, which orbits the Earth at an altitude of 400 kilometres.
The AMS (Anti Matter Spectrometer) is being sent into space to look for antimatter. Antimatter is the “mirror” form of matter. Each particle has a twin anti-particle with virtually identical properties, except that it has the opposite charge and certain subtle differences in behaviour. Matter and antimatter should have been created in equal quantities at the birth of the Universe. But for a reason yet to be elucidated, antimatter seems to have completely disappeared.
Physicists are seeking an explanation for this disappearance or else proof of the existence of antimatter in some remote corner of the Universe. Antiparticles originating from space are detected on the Earth but they are almost certainly secondary particles produced by interactions between cosmic rays and atmospheric particles in particular.
Several Earth-based experiments have looked for primordial antimatter but none has yet succeeded. AMS will go where no other antimatter experiment has ever gone before: to the International Space Station (ISS). If a significant quantity of antimatter were to be detected from the ISS, it would be proof that there is still an active source of antimatter in the cosmos. In addition to its search for primordial antimatter, AMS will analyse the composition of galactic and extra-galactic cosmic rays and look for dark matter. As its name suggests, dark matter cannot be observed directly, because it does not emit any electromagnetic radiation. However, its gravitational effects can be felt by astronauts. It is thought to constitute about 26% of the Universe, and AMS will attempt to detect it. AMS will remain on board the ISS for several years and will send out data throughout its time in space.
The experiment is now entering the final assembly phase. The detector, which weighs seven tonnes, has been built according to extremely strict specifications in order to meet the quality requirements imposed by NASA and be able to withstand a high degree of acceleration when the space shuttle is launched. For example, the glue used to assemble the tracker had to be degassed, and only 2500 of the 4000 silicon sensors produced were usable.
AMS has “recognised experiment” status at CERN and is the fruit of a collaboration involving 600 participants from Europe, the United States, China, Taiwan and Korea.