The BIS78 Pad trigger board for the Phase-I Upgrade of the Level-1 Muon Trigger of the ATLAS experiment at LHC

The Phase-I Level-1 Muon Trigger of the ATLAS Experiment receives inputs from the Resistive Plate Chamber (RPC) detector in the barrel region and from the Thin Gap Chamber (TGC), the BIS78 RPC and the New Small Wheel (NSW) detectors in the endcap region. It undergoes an intensive upgrade programme to withstand the increasing LHC luminosity and the more demanding requirements on trigger efficiency and performance. The Level-1 trigger electronics identifies muons with specific values of transverse momentum (pT) using coincidences between different detector layers. The on-detector data are transferred to the off-detector trigger electronics, which combines the information of different trigger towers and generates the Level-1 muon candidate for each ATLAS sector. As part of the upgrade programme, sixteen new RPC chambers (BIS78 system) in the Barrel Inner Small (BIS) region have been developed in order to reduce the fake trigger rate in the barrel-endcap transition region. In this work, we describe the design of the BIS78 Pad, a FPGA-based board which collects the BIS78 RPC hit data, performs the local coincidence of the detector triplet, and sends the trigger information to the off-detector endcap Sector Logic board. The Phase-I endcap Sector Logic combines the information coming from the TGC, the NSW and the BIS78 RPC to produce the endcap Level-1 muon trigger candidate.