The new Muon-to-Central-Trigger-Processor Interface at ATLAS

The ATLAS trigger system includes a Level-1 (L1) trigger based on custom electronics and firmware, and a high-level trigger based on off-the-shelf hardware and processing software. The L1 trigger system uses information from the calorimeters and the muon trigger detectors, consisting of Resistive Plate Chambers in the barrel, and Thin-Gap Chambers, small-strip Thin-Gap Chambers and MicroMegas in the endcaps. Once information from all muon trigger sectors has been received, trigger candidate multiplicities are calculated by the Muon-to-Central-Trigger-Processor Interface (MUCTPI). In the next stage, muon multiplicity information is sent to the Central-Trigger-Processor (CTP) and trigger objects are sent to the L1 Topological Trigger Processor (L1Topo). The CTP combines the information received from the MUCTPI with the trigger information from the calorimeters and the L1Topo, and takes the L1 trigger decision. As part of the ATLAS L1 trigger system upgrade for Run-3 of the Large Hadron Collider (LHC), a new MUCTPI has been designed and commissioned. We discuss the commissioning and integration of the new MUCTPI used in ATLAS from the beginning of Run-3. In particular, we describe monitoring tools which have been developed for the commissioning and operation of the new MUCTPI.