The RPC LVL1 trigger system of the muon spectrometer of the ATLAS experiment at LHC

The Atlas Trigger System has been designed to reduce the LHC interaction rate of about 1 GHz to the foreseen storage rate of about 100 Hz. Three Trigger levels are designed in order to fulfill such a requirement. A detailed simulation of the ATLAS experiment and of both the hardware components and the logic of the Level-1 Muon Trigger in the barrel of the Muon Spectrometer has been performed. This simulation has been used not only to evaluate the performances of the system but also to optimise the trigger logic design. In the barrel of the Muon Spectrometer the trigger will be given by means of Resistive Plate Detectors (RPCs) working in avalanche mode. Before being mounted on the experiment, accurate quality tests with cosmic rays are carried out on each RPC chamber using the test station facility of the INFN and University Laboratory of Napoli. All working parameters are measured and the uniformity of the efficiency on the whole RPC surface is required. A brief description of the Atlas Trigger, in particular of the Level-1 Muon Trigger in the barrel, the preliminary results of the trigger simulation, and a description of the Napoli cosmic rays tests will he given.