Wing Sheung Chan

The Large Hadron Collider and the ATLAS detector 41 by the CSCs. The CSCs are multiwire proportional chambers with wires oriented in the radial direction. Trigger chambers The trigger chambers of the MS are resistive plate chambers (RPC) and thin gap chambers (TGC). The fast response and read-out of these chambers allow the trigger system (see Section 2.2.8) to be quickly informed with the multiplicity of muon tracks and their estimated transverse momenta, which are essential for making trigger decisions. The RPCs are used in the barrel to cover the region | η | < 1 . 05 , while the TGCs are used in the end-caps to cover the region 1 . 05 < | η | < 2 . 7 . The trigger chambers also complement the tracking chambers by measuring coordinates in the direction orthogonal to that measured by the tracking chambers. 2.2.6. The magnet system Four superconducting electromagnets are stationed in the ATLAS detector. They create strong magnetic fields that bend charged particle tracks with the Lorentz force. The direction and curvature of the bent tracks can then be used to deduce the charges and momenta of particles. The layout of the four magnets is shown in Figure 2.8. Figure 2.8.: The layout of the ATLAS magnet system [67] . The magnetic field in the inner detector is provided by a solenoid magnet located between the ID and the calorimeters. It has a magnetic field strength of 2 T and is pointing in the z -direction with a high uniformity. As a result, charged particles in the ID follow helical paths with axes parallel to the beam direction.