An upgraded ATLAS Central Trigger for post-2014 LHC luminosities

In early 2012, the Large Hadron Collider (LHC) reached instantaneous luminosities of 6.7·1033 cm−2s−1 and produced events with up to 40 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS trigger in order to reduce the collision rate of up to 40 MHz when operating with design parameters to a manageable event storage rate of about 400 Hz without discarding those events considered interesting. The Level-1 trigger is the first rate-reducing step in the ATLAS trigger and primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS detectors. After 2014, the LHC will run at a centre of mass energy of up to 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 1034 cm−2s−1. With higher luminosities, the required number and complexity of Level-1 triggers will increase in order to satisfy the physics goals of ATLAS while keeping the total Level-1 rates at a maximum of 100 kHz. To provide this added functionality, the Central Trigger Processor will be upgraded during the planned LHC shutdown that begins in 2013.