Pierre Auger Observatory

Telescope Pierre Auger Observatory
Type	Hybrid (surface + fluorescence detectors)
Location	Malargüe Province of Mendoza , Argentina
height	1330 m – 1620 m, mean ~ 1400 m
Geographic coordinates	35 ° 28 ′ 0 ″ S , 69 ° 18 ′ 41 ″ W Coordinates: 35 ° 28 ′ 0 ″ S , 69 ° 18 ′ 41 ″ W-35.466666666667 -69.311388888889
wavelength	330–380 nm UV (fluorescence detector), 10 ¹⁷ –10 ²¹ eV cosmic rays (surface detector)
Aperture
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)

Cherenkov tank of the south station in the Pampas Amarilla

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)

LPDA antenna of the Auger Engineering Radio Array with solar cell to supply the associated electronics

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. ${\ displaystyle 5 {,} 6 \ cdot 10 ^ {19} \, \ mathrm {eV}}$ ${\ displaystyle 8 \ cdot 10 ^ {18} \, \ mathrm {eV}}$

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

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]).

[hybrid-1] Auger Hybrid Detector at auger.org

[2] Public event viewer of the Pierre Auger Observatory

[3] 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]).

[4] 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]).

[5] 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]).

[6] 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]).