ATLAS Detector Operation 2011 
Muon System

During the 2011 LHC Data taking period the ATLAS Detector recorded 5.22 fb-1 which is 96.5% of the delivered data from proton-proton collisions. The Muon Spectrometer was improved to 100% operational fraction at the Level 1 trigger and more than 98.7% operational fraction of trigger and precision chambers. The recorded data with Muon Spectrometer was at a level of more than 99% good for physics analysis. This illustrates an excellent performance. This poster presents performance of the Muon Spectrometer trigger chambers as well as precision chambers. In addition a combined Muon Spectrometer performance is presented.