TRTViewer: the ATLAS TRT detector monitoring and diagnostics tool.

The Transition Radiation Tracker (TRT) is the outermost of the three sub-systems of the ATLAS Inner Detector at the Large Hadron Collider (LHC) at CERN. It consists of close to 300000 thin-walled drift tubes (straws), providing on average 30 two-dimensional space points with 130 um resolution for charged particle tracks. Along with continuous tracking, it provides particle identification capability through the detection of transition radiation X-ray photons generated by high velocity particles in the many polymer fibers or films that fill the spaces between the straws, thus enabling the detector to separate electrons from pions over the energy range between 1 and 200 GeV. The TRT performance and its operation conditions have been permanently monitored during all commissioning and data-taking periods using various software tools, one of which - TRTViewer - is described in the present paper. The TRTViewer is the dedicated program for monitoring the TRT raw data quality and detector performance at different hardware levels: individual straws, readout chips and electronic boards. The data analysis results can be presented on the event-by-event basis or in the form of color maps representing the operation parameters (efficiencies, timing, occupancy, etc.) according to the real geometrical position of the detector hardware elements. This paper describes the TRTViewer software package as the event displaying tool, raw data processor and histogram and operation parameters presenter, which works with the different sources of input information: raw data files, online monitoring histograms, offline analysis histograms and TRT DAQ Configuration database. The TRTViewer proved to be one of the main instruments for the fast and effective TRT diagnostics during debugging and operation periods.