Construction of a high-resolution muon drift tube prototype chamber for LHC upgrades

The proposed upgrade of the Large Hadron Collider at CERN to luminosities above 1 × 10³⁴ cm^-2 s^-1 necessitates the replacement of a large number of tracking chambers of the muon spectrometer of the ATLAS experiment to avoid deterioration of the muon identification and the momentum measurement at high background rates. Based on the standard ATLAS Monitored Drift Tube chambers (2 × 3 or 4 tube layers, drift tube diameter 30 mm), a new design with 15 mm diameter tubes and matching services has been developed, offering an increased rate capability and better pattern recognition and redundancy due to the higher cell density. A full-sized prototype chamber consisting of 1152 tubes arranged in 2 × 8 tube layers and covering an area of 1 m² has been built to validate the assembly procedures and to test its performance.