Pierre Auger Observatory
The largest in the world to unravel the mysteries of the cosmos
The Pierre Auger Cosmic Ray Observatory is located in the city of Malargüe, in the south of the province of Mendoza, Argentina. It is an international initiative that seeks to determine the origin and identity of cosmic rays, which would allow us to advance in the understanding of our universe.
It was built by a collaboration of 18 countries, with the participation of 500 scientists from 90 institutions, and has been operating uninterruptedly since 2004. The ITeDA (CNEA-CONICET-UNSAM) has been involved in this project since its inception with the active participation of scientific groups, technical and engineering support.
Official website: auger.org.ar
What are cosmic rays?
They are enigmatic subatomic particles that reach Earth from outer space. They are predominantly protons and other atomic nuclei. Some of these cosmic particles, or astroparticles, arrive with an enormous energy charge; they are like “messengers from space” since this energy contains information that can reveal the great mysteries of outer space.
Billions of astroparticles pass through our planet and everything on it every second. This phenomenon reaches the Earth’s atmosphere with different speeds and energy ranges. The greater their energy, the lower their abundance, and those with the highest speed and energy are a very small fraction of the total: only a few per century impact each square kilometer of the Earth’s atmosphere, so their detection is very difficult.
What does the Pierre Auger Observatory study?
This Pierre Auger Observatory is the largest in the world. The main array consists of a hexagonal grid of 1,660 surface detectors, spaced 1.5 km apart, covering a total area of 3,000 km2. Around the main array are 27 fluorescence telescopes located in four buildings. On clear, moonless nights, they scan the atmosphere to observe the faint ultraviolet light produced by particle showers as they pass through the atmosphere.
AMIGA Project
Technology and innovation in the detection of the highest energies
The AMIGA project (Auger Muons and Infill for the Ground Array) is an extension of the Pierre Auger Observatory. AMIGA’s main objective is to extend the Observatory’s energy detection range by more than one order of magnitude, reaching energies up to 10^17 eV (10 million TeV).
Its scientific objective is to study the so-called “transition zone” between 10^17 and 10^19 eV, in which the change from galactic to extragalactic sources of cosmic rays is believed to occur. This region represents an area of immense astrophysical interest, marking the beginning of the study of extragalactic sources that, at higher energies, has allowed the emergence of a new type of astronomy: charged particle astronomy.
What is AMIGA?
The detection system for this project is composed of an infill of 85 pairs of surface detectors (DS) and buried detectors (DE). Of these pairs, 61 are separated at 750 meters and 24 at 433 meters. The buried detectors consist of three muon counters, each consisting of 64 plastic scintillators, a multi-pixel light sensor (SiPM) and data acquisition electronics. These counters work in conjunction with the surface detectors (DS) which detect Cherenkov radiation in water produced by particle showers.
The muon counters are buried approximately 2.3 meters underground, allowing them to detect only the muonic component of the particle showers, thus filtering out other secondary particles of lower energy. This configuration provides an accurate measurement of the muonic component, a key feature for understanding the nature of cosmic rays in the energy range of interest.
What is AMIGA’s contribution to the study of cosmic rays?
This observatory is the largest in the world. It consists of a network of 1,660 surface detectors, spaced 1.5 km apart, covering a total area of 3,000 km2 and is complemented by a set of 27 highly sensitive fluorescence telescopes that, on clear, moonless nights, scan the atmosphere to observe the faint ultraviolet light produced by cosmic ray cascades, also called particle showers, as they pass through the atmosphere.
The surface detectors are manufactured using a very specific technology. They consist of large cylindrical tanks deployed in the Pampa Amarilla area, between the Departments of San Rafael and Malargüe. Each of these tanks is hermetically sealed and contains 1,200 liters of purified water and 3 photomultiplier tubes. When the particles pass through the tank and the water it contains at very high speed, an ultraviolet light is emitted that is mostly invisible to the human eye, called Cherenkov radiation. The inside of the tank is coated with a material that is highly reflective and scattering of Cherenkov light, which redirects the light towards the photomultiplier tubes.
When the detector registers an event, the central station analyses whether neighbouring detectors also observed something. In this way, an event is recorded as a series of signals taken by different detectors. This allows the impact position of the shower to be reconstructed with high precision.
AMIGA Project
The AMIGA (Auger Muons and Infill for the Ground Array) project is an extension of the Pierre Auger Observatory. Its main objective is to extend the Observatory’s energy detection range by more than an order of magnitude, reaching energies up to 1016,8 eV.
The aim is to study in detail the so-called “transition zone” between 1016,8 and 1019 eV, where the transition from galactic to extragalactic cosmic ray sources is believed to occur.
What is AMIGA?
The detection system for this project consists of an infill of 85 pairs of surface detectors (SD) and buried detectors (BD). Of these pairs, 61 are spaced 750 meters apart, and 24 are spaced 433 meters apart. The buried detectors consist of three muon counters, each consisting of 64 plastic scintillators, a multi-pixel light sensor (SiPM), and data acquisition electronics. These counters work in conjunction with the surface detectors (SD), which detect Cherenkov radiation in water produced by particle showers.
The muon counters are buried approximately 2.3 meters underground, allowing detection of only the muon component of the particle showers, thus filtering out other, lower-energy secondary particles. This configuration provides an accurate measurement of the muon component, a key feature for understanding the nature of cosmic rays in the energy range of interest.
AUGER PRIME
Pierre Auger Observatory Upgrade Project
In recent years, the Observatory team has worked hard to upgrade, install, and commission new systems for the surface detectors. This included replacing all the electronics and replacing the solar panels with more efficient and higher-power ones. Two new detection systems were also incorporated into each surface detector: a scintillator located on the top and a radio antenna. A small phototube was also installed inside each surface detector, expanding its dynamic range.
The AMIGA muon detectors have been included in AugerPrime, as they are another of the new detection systems added to the Observatory’s basic design. Its technology, developed entirely in Spain by ITeDA, consists of underground detectors for the direct measurement of muons, a high-energy and highly penetrating elementary particle that could help us understand the nature of cosmic rays. This is of great importance for studying the transition between cosmic rays of galactic and extragalactic origin.
