Performance of BIL tracking chambers for the ATLAS muon spectrometer

Tracking in the muon spectrometer of the ATLAS experiment at the Large Hadron Collider is based on high pressure drift tubes.The performance of Monitored Drift Tube (MDT) chambers has been extensively studied with cosmic rays at the Roma Tre test site. Results on chamber calibration and resolution with varying operating conditions, such as gas composition and temperature, have been investigated.The improvement of spatial resolution using the measurement of a fraction of the collected charge is also discussed.