Fast Digital Trigger Systems for Experiments in High Energy Physics

Abstract: The data acquisition in high energy physics experiments is typically started by a pulse from a fast coincidence-based trigger system. It is essential that such a system can identify an event in a shortest possible time and with as good selectivity as possible. In order to meet these requirements, several new techniques and developments in the domain of signal discrimination and rapid hit-topology analysis are presented. Two digital rise-time compensation methods were developed to improve the time resolution of the comparatively slow signals from inorganic scintillators. Both methods utilize double threshold analog comparators and digital processing logic.A unique adaptive threshold discrimination method was developed to reject after-pulses. The method was found to give the best timing, the smallest dead time and a complete rejection of noise pulses without missing physically significant pulses. Algorithms for fast multiplicity calculations of clusters of hits in two-dimensional matrices, in strings and in planar detector configurations were evaluated.All techniques described in this thesis were implemented and verified in the trigger systems built for the experiments WASA (Wide Angle Shower Apparatus) at TSL, Uppsala, Sweden and the AMANDA (Antarctic Muon And Neutrino Detector Array) at the South Pole.