Charge-dependent corrections to the time response of ATLAS muon chambers

Monitored Drift Tubes (MDT), filled with a mixture of Ar – CO 2 at 3 bar pressure, are used as tracking devices for the ATLAS muon spectrometer at the Large Hadron Collider. MDT chambers were tested at the Roma Tre cosmic test site with the final version of front-end electronics, which provides information about the collected charge through a Wilkinson ADC. We present an analysis of the signal and timing characteristics in cosmic ray events, and of charge-dependent time response of the MDTs. A method to improve the spatial resolution of MDT chambers using the ADC information to correct the time response was developed. The procedure is based solely on the data from the MDT chamber itself. The results are compared with a simulation of the tube response with the Garfield program.