ATLAS Trigger

The ATLAS detector has been built in an underground cavern of the Large Hadron Collider. The ATLAS Trigger and Data Acquisition (TDAQ) system will have to handle extremely high data rates, due to the very high bunch crossing frequency at the LHC (40 MHz), high number of overlapping events and the large amount of data produced by the ATLAS detector itself (1-2 MB/event). The task of the TDAQ system is to select from this unprecedented amount of data the most interesting events and save them for later analysis at a rate of 200 Hz. ATLAS Trigger is organized as a multilevel structure where event selection is done in three steps.