HEGRA

HEGRA, which stands for High-Energy-Gamma-Ray Astronomy, was an atmospheric Cherenkov telescope for Gamma-ray astronomy. With its various types of detectors, HEGRA took data between 1987 and 2002, at which point it was dismantled in order to build its successor, MAGIC, at the same site. HEGRA, which stands for High-Energy-Gamma-Ray Astronomy, was an atmospheric Cherenkov telescope for Gamma-ray astronomy. With its various types of detectors, HEGRA took data between 1987 and 2002, at which point it was dismantled in order to build its successor, MAGIC, at the same site. It was located at Roque de los Muchachos Observatory on La Palma at a height of 2200 m above sea level. It was operated by an international collaboration of research institutes and universities, such as the Max Planck Institute for Physics in Munich, the Universidad Complutense de Madrid, the German Max Planck Institute for Nuclear Physics, the University of Wuppertal, the IFKKI in Kiel or the University of Hamburg. It consisted of several detector types for observing secondary particles from particle cascades in the atmosphere. The particle cascades detected by HEGRA were produced by cosmic ray particles in the energy range of 1012eV to 1016eV. The detectors with the lowest energy threshold were the atmospheric Cherenkov telescopes with 'cameras' of photomultiplier tubes. They were sensitive to showers above 1012eV (1 TeV) but had to look towards possible sources and could be operated only during clear, moonless nights. They detected Cherenkov light from relativistic secondary particles in the air showers. The field of view was about 4.6°. There were a total of six of these telescopes in operation. They were dismantled in September 2002. Another detector type for Cherenkov light was AIROBICC (AIRshower Observation By angle Integrating Cherenkov Counters) with one large photomultiplier looking at the sky above it. 49 of these detectors were spread in a 7-by-7 grid to observe the amplitude and the time of arrival of the front of Cherenkov light. Another 48 were added later on. These counters had a wide field of view but could only be operated during clear, moonless nights, like the atmospheric Cherenkov telescopes. Their energy threshold was a few 1013eV. The AIROBICC array has been dismantled.