The Hisparc cosmic ray experiment : data acquisition and reconstruction of shower direction

The field of cosmic ray physics is a century old and an exciting area of research. When cosmic ray particles enter our atmosphere they collide with air molecules creating new high-energy particles. These particles participate in further collisions and the entire process is known as an air shower. Much is still unknown about the origin of the high-energy particles. This thesis has been carried out as part of the HiSPARC science and outreach project. It focuses on the reconstruction of the direction of an extensive air shower using a station containing three 0.5 m^2 scintillator detectors in a 10 m triangle. This yields information on the origin of the cosmic rays. First, a method for reconstructing the shower direction is developed using a direct calculation. The method is based on the observation that a slanted air shower will arrive at separate detectors at different times. The thickness of the shower front, the geometry of the detectors, and other experimental effects result in measurement uncertainties of the arrival times. These introduce an uncertainty in the direction of the air shower. Using error propagation, equations are derived for calculating this uncertainty. The methods developed in this thesis have been verified first by simulations. Subsequently, data was analyzed from a station located inside the KASCADE air shower array in Karlsruhe, Germany. The 200 × 200 m KASCADE experiment provided us with an independent measurement of the direction of the air showers. The accuracy of the HiSPARC station has been determined to be 8.6° for proton showers arriving at an angle of 22.5°. Given the small size and low cost of a single HiSPARC station, the results are very good. Reconstructing the direction of an air shower by means of multiple stations has also been investigated. Using three stations with distances of 120 - 150 m an accuracy of only 1.5° can be accomplished. The goals of HiSPARC are two-fold. On the one hand, it is a traditional research group comprising research staff, graduate and undergraduate students. On the other hand, the experiment enables high-school students to participate in scientific research.