Cosmic Rays


The Pierre Auger Observatory is the largest experiment on cosmic rays in the world. The observatory is located in the Pampa Amarilla, near Malargüe in the province of Mendoza, Argentina. The main goal of the experiment is to unveil the nature and origin of the highest energy cosmic rays through detailed measurements of the properties of air showers (particle cascades) produced by these cosmic rays in the atmosphere.

pierre auger obervatory

The baseline Pierre Auger Observatory consists of a surface detector (SD) with 1600 water-Cherenkov detectors spread over 3000 square kilometers and a fluorescence detector (FD) with four stations, each containing 6 telescopes with a field of view of a solid angle of 30 by 30 degrees and together they overlook the atmosphere above the Observatory.


Within Auger, our group has pioneered the technique of detecting air showers through the radio signal they emit (Radio detection of air showers). This led to the creation of the Auger Engineering Radio Array (AERA), in which we collaborate with the Astrophysics department at Radboud. Our focus has been on understanding the radio signal emission process in detail in the 30-80 MHz frequency regime by comparing the radio data to the information provided by the Auger SD and FD.


The baseline Pierre Auger Observatory is being upgraded to AugerPrime, in which the surface detector gets a massive overhaul. A Scintillating Surface Detector (SSD) layer and a radio antenna (RD) are added to each SD water-Cherenkov detector. In addition, the electronics has been improved. All enhancements are aimed to improve the quality of air shower measurements and therefore be better at distinguishing different types of cosmic rays hitting the Earth’s atmosphere. This opens up the path to identifying sources of cosmic rays, as well as understanding the interactions in the atmosphere and thus studying particle physics at the highest energies. Our group led the mechanical design of the scintillator detector and produced 180 complete modules. Together with the Astrophysics department we lead the design, production and commissioning of the complete radio detector layer.

In parallel we are performing R&D for the construction of Giant Radio Array for Neutrino Detection (GRAND), a proposed distributed radio detector with a total area of 200,000 square kilometer that will be a true multi-messenger observatory, being sensitive to cosmic rays, photons and neutrinos at the highest energies. Our group leads the development of GP300, a 300 square kilometer prototype of GRAND located in Western-China, in which all aspects of the full detector will be tested and optimized.

Our group

Our group works on many aspects on ultra high energy cosmic ray physics, with the main goal of using information on the first interactions in the atmosphere to test the standard model of particle physics in an otherwise unreachable energy regime. The present members of our group are:


  • Sijbrand de Jong: Works on radio detection of cosmic rays, composition of UHECR and commissioning of the SSD installation for AugerPrime.
  • Cristina Galea: Works on the calibration of the radio detector and study of horizontal air showers.
  • Harm Schoorlemmer: develops new analysis and calibration techniques to improve the accuracy of air shower measurements obtained from the radio detectors at the Pierre Auger Observatory and GRAND.
  • Charles Timmermans: Works on the interpretation of the particle detector information in Auger, and the development, commissioning and understanding of GP300.

Graduate Students:

  • Mohit Saharan: Works on the calibrating and understanding of the AugerPrime RD and searching for ultra high energy neutrinos.
  • Mart Pothast: Works on understanding cosmic ray composition using the surface detector, in particular also using the new Scintillating Surface Detector units.
  • Anthony Bwembya: Measuring the cosmic ray composition with the Auger Radio Upgrade.
  • Mohamed Emam: Hunting for the highest energy photons with the Auger Radio Upgrade.

Master Students:

  • Henk Brans: Uses simulated data from radio stations at the Cherenkov-ring in order to obtain a reliable energy estimate.
  • Inge van Rens: Studies if the width of the radio signal, using a full detector description, can be used as a measure for the shower development in the 50-200 MHz frequency regime
  • Eric Teunis de Boone: Time synchronization for distributed sensors in ultra high energy cosmic ray projects.

Bachelor students:

  • Emma Spierings: Studies a physics motivated lateral distribution function for the radio signal footprint of extensive air showers.
  • Madelief Koster: : Constructing and understanding a water-Cherenkov detector.
  • Lotta van Broekhoven: Investigating the role of pi0s in extensive air showers.
  • Bram Ruiter: Running the GP300 detector in France.