KASCADE-Grande

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KASCADE-Grande ( acronym for KA rlsruhe S hower C ore and A rray DE tector-Grande) was an experiment in the field of astroparticle physics at the Karlsruhe Research Center (today Karlsruhe Institute of Technology ). It consisted of a ground-based network of 252 detector stations, with which extensive air showers were measured, which are caused by the reaction of high-energy cosmic rays with our earth's atmosphere . The aim of the experiment was the indirect measurement of the energy and mass spectrum of cosmic rays in the energy range of 10 14 –10 18  eV .

KASCADE-Grande was the extension of the original KASCADE experiment started in 1996. The data acquisition of the KASCADE Grande experiment began in 2003 and officially ended on March 30, 2009. In 2013 the experiment was dismantled. Some of the detectors are now used in other experiments for air showers, e.g. B. at LOFAR or Tunka .

In the KASCADE Cosmic-Ray Data Center (KCDC), the measurement data from the experiment have now been made publicly available.

Overview

The experiment was set up on the property of the research center. There was a densely populated, rectangular core field that consisted of the previous KASCADE experiment. It was embedded in a larger rectangular field with larger distances between the individual detector stations.

The individual stations each contained different particle detectors ( plastic or liquid scintillators with photo multipliers ), which are sensitive to the muonic and electromagnetic components of an extensive air shower. Parts of an air shower were measured from each station, the measured values were brought together centrally in real time and filtered for interesting events. Important local measurands were the particle density , the arrival time and the muon-to- electron ratio.

The LOPES experiment was also located on the same site . LOPES measured the radio emission from air showers with antennas set up within the KASCADE Grande experiment.

Determination of the mass and energy of cosmic rays

With the experiment, the energy and mass of cosmic rays could only be determined indirectly via their influence on the development and shape of the shower. An important pillar of the necessary reconstruction are detailed computer simulations of the processes taking place in the earth's atmosphere that lead to the formation of a specific shower. Since the showers naturally fluctuate strongly even for identical particles, the reconstruction is only possible on a statistical basis.

Computer simulations

Through extensive computer simulations with the Karlsruhe shower simulator CORSIKA, relationships between the measured shower shape on the ground and the mass and energy of the generating primary particle can be established. One problem here is that the computer simulation has to calculate the reaction of particles with such high energy that they have not yet been measured by any high-energy experiment in the world. In order to carry out the simulation anyway, a selection of extrapolated reaction models is used, which, however, are all based on different assumptions and vary slightly in their predictions. Due to these differences in the models, the reconstructed energy and mass also carry a systematic uncertainty in addition to the statistical uncertainty and measurement uncertainty.

Reconstruction of the shower shape

In a first step, the shape of the shower is reconstructed using the local data from the individual stations. The direction of the primary particle can already be determined from the slightly varying arrival times of the individual stations, since the shower front is perpendicular to the direction of flight of the primary particle. The front is also slightly curved: this curvature is also reconstructed from the arrival times. The particle density recorded at the network points is adapted to a radial density function emanating from the shower center, the shape of which was determined from computer simulations.

Reconstruction of the primary particle

The energy and mass of the generating cosmic particle can now be derived from the reconstructed shower data. The energy is determined via the radial density function, the conversion again depending on the simulation results. To reconstruct the mass, the muon-to-electron ratio and the front curvature are used.

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Coordinates: 49 ° 5 ′ 58 ″  N , 8 ° 26 ′ 15 ″  E