Muon Chambers

In the barrel region (|η| < 1.0), which is covered by the large barrel toroid system, muons are measured in three layers of chambers around the beam axis using precision Monitored Drift Tubes (MDTs) and fast Resistive Plate Chambers (RPCs). In regions of larger pseudorapidity, also three layers of chambers are installed, but vertically. Here Thin Gap Chambers (TGCs) are used for triggering. The precision measurement of muons is again done with MDTs, except for the innermost ring of the inner station of the end caps and for
|η| > 2, where high particle fluxes require the more radiation tolerant Cathode Strip Chamber (CSC) technology.

In the barrel of the ATLAS muon system, the muon chambers are installed in three cylinders concentric with the beam axis at radii of about 5, 7.5 and 10 m. They are arranged to form projective towers pointing to the nominal interaction vertex. In the end caps, the distance in z from the vertex is about 7, 10 and 14 m for the three layers.