Abstract

The ATLAS 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 μm resolution for charged particle tracks with |η| <; 2 and p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> >; 0.5 GeV. Along with continuous tracking, it provides particle identification 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. The custom-designed radiation-hard front-end electronics implements two thresholds to discriminate the signals: a low threshold (~300 eV) for registering the passage of charged particles, and a high threshold (~6 keV) to flag the absorption of transition radiation x-rays. The TRT was successfully commissioned with data collected from several million cosmic ray muons. A special Fast-OR signal from the front-end ASICs was utilized to build a level 1 trigger for cosmic rays traversing the ATLAS Inner Detector which allowed other ATLAS sub-detectors and level 1 triggers to align their timing. The very good timing properties of the TRT detector helped discriminate proton-proton collisions from beam background. This proceeding will describe the operational experiences gained with the ATLAS TRT detector during the commissioning with cosmic rays, and will highlight the excellent performance for charged particle tracking and electron identification based on transition radiation obtained from the first proton-proton collision data at 900 GeV and 7 TeV center-of-mass energy.

Highlights

  • A TLAS is a general purpose detector at the Large Hadron Collider (LHC) at CERN

  • The liberated electrons drift towards the anode, where the high electric field leads to secondary ionizations in the gas with an average gain of 25000

  • For the Transition Radiation Tracker (TRT) back-end electronics, clock, trigger, and command signals are sent to the front-end boards by TRT-TTC boards, 9U VME modules housed in the counting room

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Summary

INTRODUCTION

A TLAS is a general purpose detector at the Large Hadron Collider (LHC) at CERN. The LHC is a 27 km circumference, 40 MHz (allowing the design bunch spacing between proton bunches in the accelerator to be 25 ns) synchronous proton–proton, or Pb–Pb collider. Beam splashes are a spray of secondary particles which are produced when one LHC beam, in a controlled manner, is dumped into a closed collimator approximately 140 m before the beam reaches the ATLAS detector. This creates a synchronous shower of particles that cover the entire cross-section of the ATLAS detector. During the first injection of protons into the LHC in 2008 and 2009, beam splashes were used to check the timing alignment of the TRT.

APPARATUS
READOUT AND ELECTRONICS
FAST-OR COSMIC TRIGGER
TRACKING
PARTICLE IDENTIFICATION
PERFORMANCE
Findings
VIII. SUMMARY
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