Pierre Auger Observatory
Telescope Pierre Auger Observatory |
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Type | Hybrid (surface + fluorescence detectors) |
Location |
Malargüe Province of Mendoza , Argentina
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height | 1330 m – 1620 m, mean ~ 1400 m |
Geographic coordinates | 35 ° 28 ′ 0 ″ S , 69 ° 18 ′ 41 ″ W |
wavelength | 330–380 nm UV (fluorescence detector), 10 17 –10 21 eV cosmic rays (surface detector) |
Aperture |
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Installation | 2004–2008 (with measurements during construction) |
Specialty | Official website |
The Pierre Auger Observatory is an international large-scale physical experiment to investigate cosmic rays at the highest energies.
History, experiment and setup
The observatory was designed in 1992 by the Nobel laureate in physics Jim Cronin and Alan Andrew Watson and named after the French physicist Pierre Auger , who discovered the extensive air showers in 1938 .
The radiation window to be observed lies in the energy range from 10 17 eV to 10 20 eV ( electron volts ). The radiation consists mainly of protons , rarely also heavier atomic nuclei , which generate a large number (more than 10 6 ) of other particles when they hit the earth's atmosphere . This cascade of particles is known as an air shower. Since cosmic rays can no longer be observed directly with satellite or balloon experiments at energies above approx. 10 14 eV , the Pierre Auger Observatory observes these showers and thus the cosmic rays only indirectly.
The Pierre Auger Observatory was built in the Pampa Amarilla near the small Argentine town of Malargüe and was officially inaugurated in November 2008 in the presence of Jim Cronin. The test facility mainly consists of two independent detector systems , the surface detector (SD) and the fluorescence detector (FD). Radio antennas (RD) and muon detectors (MD) were later installed in part of the detector field in order to increase the measurement accuracy for lower energies . The observatory is currently being upgraded under the name AugerPrime, which consists of several improvements, above all an increase in the measurement accuracy of the surface detectors.
The surface detector (SD)
The surface detector consists of 1660 stations, which are set up in a triangular pattern with a distance of 1500 meters each on an area of about 3000 km² on a plateau about 1400 m above sea level . Each individual station consists of a tank filled with 12 m³ of ultrapure water in which incident particles generate Cherenkov radiation . This is registered by three photomultipliers in the tank lid. An air shower creates a signal in several tanks. The strength and time of the individual signals can then be used to determine the energy and direction of the primary particle.
As part of the AugerPrime upgrade, a plastic scintillation detector is installed above the surface detectors . The combined measurement with the water Cherenkov detectors makes it possible to measure the proportion of electrons and muons in the air shower and to estimate the mass of the primary particle of cosmic radiation from this.
The fluorescence detector (FD)
The fluorescence detector consists of 27 telescopes that survey the field of the surface detector from four locations. The fluorescence detector registers fluorescence light generated by the shower in the atmosphere. In this way, the development of the shower can be explored and conclusions can be drawn about the properties of the primary particle independently of the surface detector.
The fluorescence light generated is very weak, which is why the fluorescence detector can only be operated during moonless nights, which make up about 13% of the operating time. However, this short operating time is compensated for by a significantly higher accuracy compared to the surface detector.
The radio detector (RD)
The radio detector, the Auger Engineering Radio Array (AERA), consists of over 150 antenna stations on an area of 17 km². Two types of antennas are mainly used for the stations: Log Periodic Dipole Antenna (LPDA) and Active Bow tie Antenna (Butterfly). Each station has two antennas to measure the electronic field proportionally in the east-west and north-south polarization . Both antenna types measure between 30 and 80 MHz. While the focus was initially on the technical feasibility of the radio technology, the focus is now on increasing the measurement accuracy for air showers through joint evaluation with the other detectors.
As part of the AugerPrime upgrade, a SALLA radio antenna is to be installed on every surface detector, the previous model of which was already successfully used in the Tunka experiment . These antennas will increase the measurement accuracy for steeply sloping air showers.
The muon detector (MD)
The muon detector consists of buried scintillation particle detectors. So far, additional muon detectors have been installed in seven SD detectors to increase the accuracy of the composition of cosmic rays. In the next few years, more than 20 km² of the surface detector will be equipped with muon detectors, precisely where the radio antennas are located. Because at this point the surface detector is compressed to a distance of 750 m, which enables a lower energy threshold of less than 1 EeV (exa electron volt).
The Pierre Auger Collaboration has decided to make 1% of the data publicly available. Events collected since 2004 can be viewed on a website that is updated daily.
First results
The first observations of the high-energy cosmic rays above showed an accumulation from the direction of the centers of active galactic nuclei . However, it is not yet clear to what extent active galactic nuclei are actually the sources of this radiation, since their spatial distribution is also correlated with the distribution of other possible sources. In the meantime a significant anisotropy of cosmic rays above has been observed. This confirms the assumption that the highest energy cosmic rays do not originate in our galaxy, the Milky Way , but in other galaxies. The type of galaxy from which the radiation originates has not yet been conclusively determined. Future measurements with the observatory improved by AugerPrime should provide information on this.
New questions also arise, for example an increased occurrence of muons is measured, which does not fit into the previous air shower models. This observation is confirmed by data from several other experiments.
German members of the Pierre Auger Observatory
- RWTH Aachen
- Max Planck Institute for Radio Astronomy , Bonn
- University of Hamburg
- Karlsruher Institute for Technology
- University of Siegen
- University of Wuppertal
literature
- Hilmar Schmundt: Hunt for the puzzle pieces . In: Der Spiegel . No. 49 , 2008, p. 167 ( online ).
Web links
- Pierre Auger Observatory international (English)
- German pages of the Pierre Auger Observatory
- local pages of the Pierre Auger Observatory (Spanish)
- Pierre Auger Observatory determines active galactic nuclei as the source of the high-energy cosmic particles
- Public event viewer
- Report ( memento of September 30, 2007 in the Internet Archive ) in the program nano on 3sat, January 2006
Individual evidence
- ↑ Auger Hybrid Detector at auger.org
- ↑ Public event viewer of the Pierre Auger Observatory
- ↑ A. Aab, P. Abreu, M. Aglietta, E. J. Ahn, I. Al Samarai: Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events . In: Physical Review D . tape 91 , no. 3 , February 6, 2015, ISSN 1550-7998 , p. 032003 , doi : 10.1103 / PhysRevD.91.032003 ( aps.org [accessed July 17, 2020]).
- ^ Sarah Müller, for the Pierre Auger Collaboration: Direct Measurement of the Muon Density in Air Showers with the Pierre Auger Observatory . In: EPJ Web of Conferences . tape 210 , 2019, ISSN 2100-014X , p. 02013 , doi : 10.1051 / epjconf / 201921002013 ( epj-conferences.org [accessed July 17, 2020]).
- ^ F. Gesualdi, A. D. Supanitsky, A. Etchegoyen: Muon deficit in air shower simulations estimated from AGASA muon measurements . In: Physical Review D . tape 101 , no. 8 , April 22, 2020, ISSN 2470-0010 , p. 083025 , doi : 10.1103 / PhysRevD.101.083025 ( aps.org [accessed July 17, 2020]).
- ↑ HP Dembinski, JC Arteaga-Velázquez, L. Cazon, R. Conceição, J. Gonzalez: Report on Tests and Measurements of Hadronic Interaction Properties with Air Showers . In: EPJ Web of Conferences . tape 210 , 2019, ISSN 2100-014X , p. 02004 , doi : 10.1051 / epjconf / 201921002004 ( epj-conferences.org [accessed July 17, 2020]).