A first-level calorimeter trigger for the ATLAS experiment

In the RD27 collaboration we have carried out system studies on the implementation of a first level calorimeter trigger processor system for the ATLAS experiment. These system studies have led to the design of a fully synchronous calorimeter trigger processor system using commercial high-speed optical links. The links will terminate in multi-chip modules incorporating custom-designed integrated optics, and the trigger algorithms will be implemented in ASICs. The full system can be contained in six 18SU size crates which will process approximately 4000 electromagnetic and 4000 hadronic trigger cells and provide the central trigger processor with signals from events with high-P T electrons/photons, jets and missing-ET.