Upgrade of the ATLAS Muon Spectrometer for Operation at the HL-LHC

The High-Luminosity Large Hadron Collider (HL-LHC) will increase the sensitivity of the ATLAS experiment to low-rate high-energy physics processes. In order to cope with the 10 times higher instantaneous luminosity compared to the LHC, the trigger system of ATLAS needs to be upgraded. The ATLAS experiment plans to increase the maximum rate capability of the first two trigger levels to 1 MHz at 6 µs latency. This requires new on- and off-chamber electronics for its muon spectrometer. The replacement of the precision chamber read-out electronics will make it possible to include their data in the first level trigger decision and thus to increase the selectivity of the first level muon trigger. The acceptance of the present RPC trigger system in the barrel will be increased from 75% to 95% by the installation of additional thin-gap RPC with a substantially increased high-rate capability compared to the current RPCs.