A digital trigger for the electromagnetic calorimeter at the COMPASS experiment

At the COMPASS experiment at CERN´s SPS many physics channels containing neutral particles are studied. These particles are identified by two electromagnetic calorimeters covering different transfers regions. For certain physics the main signature is described by these neutral particles which requires a calorimetric trigger system. The method described here is fully based on the existing front end electronics and uses digital pulse shape analysis techniques. This approach allows to implement a flexible trigger system as well as to reduce cost by avoiding to produce new electronic components. The implementation of this new trigger as well as the performance measured during the 2009 run will be discussed.