Extensive performance studies for the ATLAS BIS-MDT precision muon chambers with cosmic rays

ATLAS (a toroidal LHC apparatus) is a general purpose experiment that will start its operation at the large hadron collider (LHC) at CERN in 2007. The ATLAS detector is designed to explore numerous physics processes by recording, measuring, and investigating the products emerging from proton-proton collisions at energies up to 14 TeV. High-precision muon momentum measurement (dp/p∼10% at p_T=1 TeV/c) over large areas using monitored drift tube (MDT) chambers is crucial for the ATLAS experiment. More than 1200 MDT chambers, consisting of approximately 370 000 drift tubes, will provide a total coverage of 5500 m². Three Greek universities have taken the responsibility to construct 130 barrel inner small (BIS)-MDT chambers using 30 000 drift tubes of ∼1.7 m length that have been quality tested before assembly. The design of the muon drift tubes aims at high detection efficiency (>95%) and a spatial single tube resolution of <80 μm. This paper describes the cosmic ray test setup, which has been instrumented in order to verify that the BIS-MDT chamber Module-0 fulfills its design requirements. The analysis of its data shows that the chamber meets these requirements; it has low noise levels, uniform drift properties, good spatial resolution, and high particle detection efficiency.