Commissioning and Performance of the ATLAS Transition Radiation Tracker with high energy collisions at LHC

The ATLAS Transition Radiation Tracker (TRT) is the outermost of the three sub-systems of the ATLAS Inner Detector at the Large Hadron Collider at CERN. It consists of close to 300,000 thin-wall drift-tubes (straws) providing on average 30 two-dimensional space points for charged particle tracks. The straws have 0.13 mm resolution and measure tracks with $ ert eta ert < 2 $ and $ pT> 0.5 GeV$. Along with continuous tracking, it provides particle identification capability through the detection of transition radiation X-ray photons generated by high Lorenz gamma particles in the many polymer fibers or films that fill the spaces between the straws. In this talk, a review of the commissioning and first operational experience of the TRT detector will be presented. Emphasis will be given to performance studies based on the reconstruction and analysis of LHC proton-proton collisions.