Pierre Auger Observatory
The Pierre Auger Observatory is an international project to investigate ultrahigh energetic cosmic radiaton located in Malargue, Argentina. It was founded by the US-American Nobel laureate Jim Cronin and the Briton Alan Watson in 1992. The observatory was named after the French physicist Pierre Victor Auger (1899 - 1993) who discovered giant airshowers. With an area of 3000 km2, it is the largest cosmic ray observatory worldwide.
Cosmic radiation is an immensely high-energy particle radiation reaching us from all directions of the outer space. It mainly consists of nucleus of the elements from hydrogen to iron. Via interaction with the earth's atmosphere, they produce cascades of ionized particles and electromagnetic radiation, called air showers.
The observatory is designed to measure radiation with energies from 1017 eV to 1020 eV. For energies of 1019 eV, only 1 particle per sqare kilometer and century is expected. Due to this small flux, such particles can only be observed by monitoring a large area.
The first part of the observatory was completed in 2004 and has been providing data since.
Two Detector Systems
The observatory consists of two independent detectorsystems, a surface detector and a fluorescence detector.
The surface detector is organized in a grid of 1600 autonomous stations with a distance of 1.5 km. In sum, they cover an area of 3000 km2. Each station is a water Cherenkov detector, measuring incoming charged particles. An airshower leaves a signal in several stations. From the signal strength and the time of each individual event, the energy and the direction of the primary particle can be determinded.
The fluorescence detector is built of 24 telescopes, separated onto four locations. They measure fluorescence light having its origin in interactions of airshowers with the atmosphere. The fluorescence light, invisible to the human eye, is very weak. It can only be detected in moonless nights which corresponds to approximately 15 % of the uptime. Compared to the surface detector, this disadvantage is compensated by a precise energy measurement. Moreover, the fluorescence detector gives an insight into the propagation of showers.
Auger at Aachen III A
Prof. Thomas Hebbeker: FAMOUS, Aachen Muon Detector
Prof. Martin Erdmann: more information on current research