Department №40

Laboratory work №2

Detector TRT and modern monitoring methods and diagnostic tools (TRTVIEWER)


The main goal of the laboratory work #2 is to study the construction and functioning of the ATLAS TRT and also to get some experience with modern detector monitoring tools using TRTViewer software package.

Students will learn to work with TRTViewer monitoring software package. They will determine TRT noise characteristics and will test TRT prototype on cosmic rays, will get an insight into track reconstruction, timing calibration and malfunctions diagnostics.


  • ATLAS TRT detector function and construction
  • Introduction to the TRT front-end electronic principles (FE-ROD-ROS-EventBuilder)
  • TRTViewer software package (short description), means of data presentation (event display, straw data, straw maps, histograms (straw click and browser))
  • Timing bit pattern from the drift tube and its presentation in TRTViewer window
  • Threshold scan (noises), threshold tuning, the means of noise suppressions (Validity gate)
  • Operation with cosmic particles data and Fast-OR trigger
  • Track reconstruction procedure, timing calibration (t0, R-t dependence), coordinate accuracy, efficiency.
  • Electrons identification principles, dependency on threshold and high voltage
  • Analysis of test results and problems characterization (noise, electronics problems, high voltage problems)
  • Answer to control questions, plotting

Additional information and links

This laboratory work is dedicated to the learning of modern detector monitoring and diagnostic tools. It based on example of the TRT detector of the ATLAS experiment on LHC.

The introductory lecture overviews the basics principles of TRT construction and functionality. The TRT data acquisition system and stored data formats are described. The overview of dedicated TRT monitoring and diagnostic tool – TRTViewer program – is presented. We learn how to work with TRTViewer, the meaning and significance of presented information.

By use of TRTViewer version installed on MEPhI computer students will process stored experimental data obtained with the engineering TRT prototype in cosmic rays at different operational conditions (high voltage, electronics threshold) an will plot the appropriate dependencies.

At the end of this work students will present the obtained results and answer the test questions.

The ATLAS TRT detector

TRT detector (Transition Radiation Tracker) is a part of the ATLAS Inner Detector. Its purpose is a coordinate measurement of charged particles produced in the interactions of colliding beams of the LHC and the identification of these particles. The detector consists of a central (the barrel) and the two end-caps pieces. The main detecting elements are thin-walled cylindrical drift chambers (straws). In the barrel part of the TRT 52544 150 cm chambers are arranged along the axis of the colliding beams. In End-caps 245,760 chambers with a length of 64 to 103 cm are orientated in the radial direction. TRT gives in average about 35 coordinate measurements on the charged particle track with an accuracy of about 150 microns. Pions suppression factor at 90% of electrons detection efficiency is about 100.

Detailed description of the TRT is presented in the introductory lecture to the lab. Official Web page of the ATLAS TRT detector can be found here (a special permission to access is required). For a detector acquaintance one can also see a variety of TRT photos and video animation.

TRTViewer program

The TRTViewer program is dedicated for monitoring and diagnostic of TRT detector at the level down to a single electronics channel. The program gives a possibility of quick and visually evident identification of possible problems - noisy, dead, inefficient channels, chip or circuit boards , as well as problems with timing or amplitude calibration. TRTViewer can operate in both on-line, receiving information from the ATLAS data acquisition system (DAQ) during operation of the accelerator, and in offline mode. In the latter case, the source data are already stored as recorded files with raw (unprocessed) data or as ROOT histograms. The program can also operate in "Event display” mode, allowing you to browse the individual events in the TRT.

Detailed description of the TRTViewer program is given in introductory lecture to the laboratory work. Official Web page with the TRT detector documentation, including description of the TRTViewer program is located here (a special permission to access is required).