Resolution and efficiency of the ATLAS muon drift-tube chambers at high background rates

Abstract

The resolution and efficiency of a precision drift-tube chamber for the ATLAS muon spectrometer with final read-out electronics was tested at the Gamma Irradiation Facility at CERN in a 100GeV muon beam at photon irradiation rates of up to 990Hz/cm2, which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope served as external reference in the beam. The pulse-height measurement of the read-out electronics was used to perform time-slewing corrections, which lead to an improvement of the average drift-tube resolution from 104 to 82μm without irradiation, and from 128 to 108μm at the maximum expected rate. The measured drift-tube efficiency agrees with the expectation from the dead time of the read-out electronics up to the maximum expected rate.