Resolution and Efficiency of the ATLAS Muon Drift-Tube Chambers at High Background Rates

TL;DR

This study evaluates the resolution and efficiency of ATLAS muon drift-tube chambers under high background radiation, demonstrating improved resolution with time-slewing corrections and confirming expected efficiency levels at high irradiation rates.

Contribution

The paper presents the first detailed performance assessment of ATLAS muon drift-tube chambers at high background rates, including resolution improvements and efficiency validation.

Findings

Resolution improved from 104 to 82 microns without irradiation.

Resolution at maximum rate was 108 microns after corrections.

Efficiency matched expectations based on electronics dead time.

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 100 GeV muon beam and at photon irradiation rates of up to 990 Hz/square cm which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope was used 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 microns to 82 microns without irradiation and from 128 microns to 108 microns 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.