Construction and Performance of the sMDT Precision Muon Tracking Chambers for ATLAS at the HL-LHC

Abstract

In order to improve the muon trigger efficiency and the rate capability of the ATLAS muon detectors for operation at the high luminosity upgrade of the Large Hadron Collider (HL-LHC), the Monitored Drift Tube (MDT) tracking chambers in the inner barrel layer of the ATLAS Muon Spectrometer will be replaced by small-diameter Muon Drift Tube (sMDT) chambers integrated with new thin-gap RPC trigger chambers. The sMDT chambers are in serial production since January 2021. This documentation provides insight into the drift tube production and every step performed in the chamber construction at the MPI Munich. The serial production involves a stringent quality control program to assure the reliability and high mechanical precision of the chambers. This program consists of tests of the individual drift tubes, measurements of the chamber geometry and proof of gas tightness. Final certification at the production site is provided using cosmic rays. The dedicated quality control database and monitoring Web interface that is used commonly for both production sites of the sMDT chambers is presented