Small-strip thin gap chambers for the muon spectrometer upgrade of the ATLAS experiment

Abstract

The instantaneous luminosity of the Large Hadron Collider at CERN will be increased by about a factor of five with respect to the design value after the extensive upgrade program over the coming decade. In order to cope with the increasing luminosity, the ATLAS experiment is being upgraded as well. The largest phase-1 upgrade project for the ATLAS Muon System is the replacement of the present first station in the forward regions with the New Small Wheels (NSWs) during the long-LHC shutdown in 2019-2021. The NSWs are based on two detector technologies: Micromegas (MM) and small-strip TGC (sTGC), the later arranged in two quadruplets, each consisting of 8 layers. To retain the good precision tracking and trigger capabilities in the high background environment of the high luminosity LHC, each sTGC plane must achieve a spatial resolution better than 100 μm. It will allow to reconstruct tracks with an angular resolution of approximately 1 mrad. The sTGC design, performance, construction and integration status are discussed, along with results from tests of the chambers with nearly final electronics with beams, cosmic rays and high-intensity radiation sources.