Prototype Slice of the Level-1 Muon Trigger in the Barrel Region of the ATLAS Experiment

The ATLAS barrel level-1 muon trigger system makes use of the Resistive Plate Chamber detectors mounted in three concentric stations.Signals coming from the first two RPC stations are sent to dedicated on detector ASICs in the low-p T PAD boards, that select muon candidates compatible with a programmable p T cut of around 6 GeV, and produce an output pattern containing the low-p T trigger results.This information is transferred to the corresponding high-p T PAD boards, that collect the overall result for low-p T and perform the high-p T algorithm using the outer RPC station, selecting candidates above a threshold around 20 GeV.The combined information is sent via optical fibre to the off-detector optical receiver boards and then to the Sector Logic boards, that count the muon candidates in a region of =1.00.1, and encode the trigger results.The elaborated trigger data is sent to the Central Trigger Processor Muon Interface on dedicated copper link.The read-out data for events accepted by the level-1 trigger are stored on-detector and then sent to the offdetector Read-Out Drivers via the same receiver boards used for trigger data, sharing the bandwidth.A trigger slice is made of the following components: a splitter, a low-p T PAD board, containing four Coincidence Matrix boards; a high-p T PAD board, containing 4 CM boards and the optical link transmitter; an optical link receiver; a Sector Logic board; a Read-Out Driver board.