The cosmic-ray experiment KASCADE

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Abstract

KASCADE has been designed to measure air showers of primary cosmic-ray energies in the PeV region and to investigate the knee phenomenon in the all-particle energy spectrum. Several observations are measured simultaneously for each event by different detector systems. The experiment started to take data in 1996 and has been completed and extended since then. The individual detector systems and their performances are described. Also, the experience in long-term operation of the experiment and the interplay between different components is outlined.

Introduction

Investigating cosmic rays of primary energies around 1PeV and above is presently possible only with ground-based detector systems. With these installations large surface areas and long exposure times can be realized to cope with the low particle flux at high energies. Measurements above the atmosphere using detector systems on satellites, spacecrafts, or balloons are limited in acceptance area and observation time and run out of statistics at about 1PeV primary energy.

For ground-based experiments astrophysically relevant parameters like energy, mass, or direction of incoming cosmic-ray particles have to be deduced from the particle distributions in the extensive air showers (EAS) which they initiate in the atmosphere. Therefore, as many different observables as possible have to be measured simultaneously from which the properties of the primaries have to be calculated. Also, a thorough check of the interaction model used when simulating the EAS is important because the physics of the hadronic interaction at the high energies in question and in the very forward direction has been investigated at accelerators only scarcely and, thereby, is not known sufficiently well.

The experiment KArlsruhe Shower Core and Array DEtector (KASCADE) has been conceived following these aspects [1]. It is placed at the laboratory site of the Forschungszentrum Karlsruhe in the Rhine valley at 110m a.s.l. (49n,e) and takes data continuously since 1996. In the present article an overall description of the experimental performance is given including the interplay of a multi-component installation, its resolutions, and long-term stability.

Section snippets

Experimental set-up

The experiment measures the electromagnetic component with an array of scintillation counters, the muonic component by scintillators and tracking chambers at four different energy thresholds and the hadronic component in a sampling calorimeter. Fig. 1 shows the schematic layout with the three main components: detector array, central detector and muon tracking detector on a surface of 200×200m2. Fig. 2 gives an idea of the particle intensities in a typical EAS of 1PeV primary proton and their

Detector array

The scintillation detectors of the array are housed in 252 stations on a grid with 13m spacing and are electronically organized in clusters of 16 stations, the inner clusters only with 15 stations, see Fig. 1. In order to optimize the layout, the shower particles generated with CORSIKA have been tracked through the detector simulation code CRES, which is a specific adaptation of the GEANT 3 code [3] to the KASCADE detectors. It generates the same signal response as the real detectors do. As

Central detector

A sketch of the central detector with an area of 320m2 is displayed in Fig. 15. It consists of a hadron sampling calorimeter with eight tiers of iron absorber interspersed with nine layers of warm-liquid ionization chambers. Below the third absorber plane a layer of plastic scintillators serves as detector for studies of the EAS time structure and to trigger the read-out of the ionization chambers as well as the muon detectors in addition to the array trigger. The multi-wire proportional

Muon tracking detector

North of the central detector the muon tracking detector represents a second device for muon measurements by tracking. It came into operation recently. Fig. 26 shows a side view of the installation. A large spacing of 82cm between three horizontal planes of limited streamer tubes ensures a precise determination of the muon angle and allows to extrapolate the track back to find its production height by means of triangulation. The total length of the detector extends to 32m and provides an

Central data acquisition

The detector array, the FADC system, the muon tracking detector, the top-cluster, the trigger plane, the MWPCs and LSTs in the central detector basement as well as the hadron calorimeter are independent experimental components, which can be started, run, read out and stopped alone or together. To correlate the data from different parts of KASCADE, common clock signals are used as outlined in Section 3.4.

Fig. 30 gives an overview on the basic components of the data acquisition and control

Conclusion and outlook

Since 1996 the experiment has taken data continuously, in total 8×108 showers up to the end of 2002. A host of interesting results has been obtained, e.g. on the knee structure in the energy spectrum, the primary mass composition and the hadronic interaction in the forward direction. The analysis procedures have improved considerably, not least due to redundant data which allow important consistency checks. Regular calibrations and cross calibrations, tests of efficiency and uniformity in

Acknowledgements

The authors would like to thank the members of the engineering and technical staff of the collaboration who contributed with enthusiasm and engagement to the success of the experiment. The KASCADE experiment is supported by the German Federal Ministry of Education and Research. Additional support has been provided by collaborative WTZ projects between Germany and Romania (RUM 97/014), Poland (POL 99/005), and Armenia (ARM 02/98). The Polish group acknowledges the support by KBN grant no. 5PO3B

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Cited by (0)

1

On leave of absence from National Institute of Physics and Nuclear Engineering, 7690 Bucharest, Romania.

2

On leave of absence from Moscow State University 119899 Moscow, Russia.

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