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

The Phase-I upgrade Level-1 Muon Trigger of the ATLAS Experiment will receive inputs from the Resistive Plate Chamber (RPC) detector in the barrel region and from the Thin Gap Chamber, the Barrel Inner Small 7/8 (BIS78) RPC and the New Small Wheel detectors in the endcap region. The intensive upgrade program will allow the trigger to withstand the increasing LHC luminosity and the more demanding requirements on trigger efficiency and performance. As part of the upgrade program, 32 new RPC chambers (the BIS78 system) in the barrel inner small region have been developed to reduce the fake trigger rate in the barrel-endcap transition region. In this work, we describe the design of the BIS78 Pad, an 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 Thin Gap Chamber, the New Small Wheel and the BIS78 RPC to produce the endcap Level-1 muon trigger candidate; it identifies muons with specific values of transverse momentum using coincidences between different detector layers.