Ultrahigh energy cosmic rays – Pierre Auger Observatory


The Pierre Auger Observatory studies the properties of ultra-high energy cosmic rays (UHECR, above 1 EeV (10^(18) eV). The hybrid concept and the size of the Observatory provide unprecedented opportunities to precisely measure the UHECR and start to reveal the long-lasting mystery of UHECR.  The Pierre Auger Observatory is an international collaboration of 17 countries including around 500 scientists from about 90 institutes world-wide. This collaboration was established in the ’90s and the Czech Republic has participated in the project since 1997. Between 2000-2008, the largest cosmic-ray observatory in the world was built with a strong Czech contribution, especially in the fluorescence detector part. The Observatory is located in the Pampa Amarilla, near the city of Malargue, Mendoza province, Argentina.

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Test setup for new electronics of the upgrade Pierre Auger Observatory. (ESS-lab.JPG)

There are two detection techniques combined at the Pierre Auger Observatory. The fluorescence detector consists of 27 telescopes located at 4 sites surrounding the array of 3000 km2. Around 1660 surface detectors are installed at this array with 1.5 km spacing in a regular triangular grid. For the first time in history, the combination of two detection techniques has been implemented providing a collection of unprecedented high statistics of UHECR adopting precise energy calibration.

Our researchers are highly involved in the measurement of mass composition of UHECR, testing of hadronic interactions using the cosmic-ray data, anisotropy searches in the arrival directions of UHECR and upgrade of the surface detectors. The group has significantly contributed to the development and operation of the fluorescence detector. The collaboration within the Institute covers namely scientists from the astroparticle physics department and from Joint laboratory of Palacky University and the Institute of Physics that is located in Olomouc. Half of the mirrors for fluorescence detectors were produced in Olomouc and our opticians are now involved in the calibration of the fluorescence telescopes.

Our researchers are also involved in the atmospheric monitoring that is crucial for precise measurement of UHECR in the fluorescence detectors.

Pierre Auger Observatory, which was founded 20 years ago, is currently being upgraded. As a part of this upgrade, the electronics of the surface detectors are being exchanged for a new, more powerful system. Czech contribution to the realization of the upgrade consists of mass testing of all electronic modules before their transportation and installation in Argentinian pampa. In the laboratory of astroparticle physics, we designed and created a test bench and developed a procedure for burn-in and functionality tests emulating the hard climatic conditions in pampa.

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Station of the water Cherenkov detector (in front) and the fluorescence detector building (at the horizon near the communication tower).

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