The alignment system of the ATLAS muon spectrometer

Abstract

The muon spectrometer of the ATLAS detector at the LHC has been designed to provide a good stand-alone momentum resolution for muons up to about 1 TeV. For this purpose, muon drift tube chambers with very high spatial resolution were developed; in addition, a precise online alignment monitoring system is required. This system is based on optical sensors measuring the individual deformations and the relative positions of muon chambers; temperature sensors are used to monitor their thermal expansion. In the endcap, the alignment system has to make use of additional alignment bars, used as precision reference rulers. In the year 2002, the ATLAS muon collaboration has installed a large-scale test setup of the muon spectrometer barrel and endcap in the H8 test beam line at CERN; one of its aims is to test the concepts and the final prototypes of the components of the alignment system before starting the mass production.