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ATLAS Note
Report number	ATL-INDET-PROC-2016-001
Title	ATLAS Transition Radiation Tracker (TRT): Straw tubes for tracking and particle identification at the Large Hadron Collider
Author(s)	Mindur, Bartosz (AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow)
Corporate Author(s)	The ATLAS collaboration
Publication	2017
Imprint	16 Mar 2016
Number of pages	4
In:	Nucl. Instrum. Methods Phys. Res., A 845 (2017) 257-261
In:	14th Vienna Conference on Instrumentation, Vienna, Austria, 15 - 19 Feb 2016, pp.257-261
DOI	10.1016/j.nima.2016.04.026
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	gaseous detectors ; transition radiation detector ; tracking ; particle identification ; VCI2016
Abstract	The ATLAS Transition Radiation Tracker (TRT) is the outermost of the three inner detector tracking subsystems and consists of ∼300,000 thin-walled drift tubes (“straw tubes”) that are 4 mm in diameter. The TRT system provides ∼30 space points with ∼130 micron resolution for charged tracks with |η| < 2 and p$_{T}$ > 0.5 GeV/c . The TRT also provides electron identification capability by detecting transition radiation (TR) X-ray photons in an Xe-based working gas mixture. Compared to Run 1, the LHC beams now provide a higher centre of mass energy (13 TeV), more bunches with a reduced spacing (25 ns), and more particles in each bunch leading to very challenging, higher occupancies in the TRT. Significant modifications of the TRT detector have been made for LHC Run 2 mainly to improve response to the expected much higher rate of hits and to mitigate leaks of the Xe-based active gas mixture. The higher rates required changes to the data acquisition system and introduction of validity gate to reject out-of-time hits. Many gas leaks were repaired and the gas system was modified to use a cheaper Ar-based gas mixture in some channels. A likelihood method was introduced to optimise the TRT electron identification.
Copyright/License	Preprint: (License: CC-BY-4.0)

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