The global trigger system of the magic telescope array

The Magic experiment is located in the La Palma island, Canary (Spain) and has started collecting data in 2004. The upgrade project of the experiment consists in the construction of a second telescope similar to the first one using new technologies such as high efficiency photon detectors, last generation VCSELs for optical signal transmission and signal sampling at GHz frequencies. With the operation of the first telescope the collaboration has succeeded in lowering the energy threshold the very low value of 30 GeV never reached before by other Cherenkov telescopes. The construction of the second telescope will allow the experiment to perform stereo observations of the atmospheric showers and help in resolving structured objects. For the simultaneous observation it is possible to drastically reduce the muonic background by applying a narrow time coincidence between the trigger signals from the two telescopes. During normal operation each telescope operates with several trigger sources and it is therefore mandatory to discriminate the trigger source when applying the coincidence logic. The design of the global trigger system is described in detail and performances of the system are presented.