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Simulation study of the ATLAS Muon Drift Tube Chambers performance in presence of magnetic field

Simulation study of the ATLAS Muon Drift Tube Chambers performance in presence of magnetic field. Mermigka Kalliopi National Technical University of Athens Faculty of Applied Sciences Department of Physics Ioannina, 13-16 April 2006. Muon Drift Tube. ATLAS Experiment. ATLAS detector.

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Simulation study of the ATLAS Muon Drift Tube Chambers performance in presence of magnetic field

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  1. Simulation study of the ATLAS Muon Drift Tube Chambers performance in presence of magnetic field Mermigka Kalliopi National Technical University of Athens Faculty of Applied Sciences Department of Physics Ioannina, 13-16 April 2006

  2. Muon Drift Tube ATLAS Experiment ATLAS detector Operation Principle Drift Time Spectrum Muon Drift Chamber Mermigka Kalliopi - N.T.U.A.

  3. Outline • Detailed simulation studies have been performed investigating the drift properties of the nominal MDT gas (Ar/CO2-93/7) in presence of magnetic field. • Results of the effect of magnetic field varying from 0.1 T to 1.4 T on muon tracks passing at different distances from the tube anode wire will be discussed. • The reliability of the simulation program -Garfield with Magboltz- has been verified with comparisons of precision measurements in the bibliography.It is the first time of validation with magnetic field against to the measurements. • - NIM A324 (1993) 127-140, T. Kunst, B. Gotz, B. Schmidt • - NIM A398 (1997) 249-264, X. Bittl, V. Fessler, et al. • The only measurements in ATLAS with magnetic field done by • O. Kortner, C. Valderanis, MPI, not published yet Mermigka Kalliopi - N.T.U.A.

  4. Garfield Simulation The drift time of electrons depends on: • gas composition, • temperature, • pressure variationsand • magnetic field. We will show this dependence in presence and absence of magnetic field. • Garfield is a computer program for the detailed simulation of two- and three-dimensional drift chambers. • Magboltz provides the computation of electron transport properties in gas mixtures under the influence of electric and magnetic fields. We have used the newestGarfield 9 with Magboltz 7. Mermigka Kalliopi - N.T.U.A.

  5. Typical Events in Garfield simulation Muon Track Muon Track Electron drift lines Electron drift lines Ion drift lines Ion drift lines NO magnetic field Magnetic field of 3Tparallel to the wire Mermigka Kalliopi - N.T.U.A.

  6. Gas Composition Temperature 20 °C – Pressure 3 bar NO magnetic field Magnetic field 0.5Tparallel to the wire The maximum drift timedecreases (↓)up to 3% of CO2 and then increases (↑). For higher percentages of CO2 the cross section goes up (↑), the mean free path goes down (↓) and consequently the drift time increases (↑). Mermigka Kalliopi - N.T.U.A.

  7. Temperature Effect Ar/CO2 (93:7) – Pressure 3 bar NO magnetic field Magnetic field 0.5 Tparallel to the wire According to gas equation P=(n/V)RT and Pressure (P)=constant: Temperature (T) (↑)number of molecules per volume (n/V) (↓) the mean free path(↑)and the maximum drift time(↓). Mermigka Kalliopi - N.T.U.A.

  8. Pressure Effect Ar/CO2 (93:7) – Temperature 20 °C NO magnetic field Magnetic field 0.5Tparallel to the wire According to gas equation P=(n/V)RT and Temperature (T)=constant: Pressure(P) (↑)number of molecules per volume (n/V) (↑) the mean free path(↓)and the maximum drift time(↑). Mermigka Kalliopi - N.T.U.A.

  9. ΔT vs. r P. Bagnaia, G. Volpi The maximum drift time differences due to a magnetic field B, parallel to the wire, as a function of the distance r between the track and the anode wire. The parallel component of the magnetic field in the ATLAS muon spectrometer. The position of the MDT chambers is shown. Mermigka Kalliopi - N.T.U.A.

  10. Reliability of simulation program • Two components of the drift velocity: • (uz)parallel to the electric field, • (ux)perpendicular to both the electric and magnetic field. • One can specify the absolute value of the drift velocity(u) and tana=ux/uz, where a is called the Lorentz angle. It is the first time of validation with magnetic field against to the measurements. Mermigka Kalliopi - N.T.U.A.

  11. Reliability of simulation program Left side:Drift velocity in 90% Ar + 10% CH4with magnetic field 2 Hx (=B/N). Right side:Lorentz angle in 90% Ar + 10% CH4with magnetic field 2 Hx. Mermigka Kalliopi - N.T.U.A.

  12. Reliability of simulation program Left side:Drift velocity in 90% Ar + 10% CH4with magnetic field 20 Hx (=B/N). Right side:Lorentz angle in 90% Ar + 10% CH4with magnetic field 20 Hx. Mermigka Kalliopi - N.T.U.A.

  13. Summary • Maximum drift time dependence: • Higherpercentages of CO2tm(↑) • Temperature(↑) tm(↓) • Pressure(↑) tm(↑) • Garfield with Magboltz is a good simulation tool for the study of MDT Chambers in presence of magnetic field. Mermigka Kalliopi - N.T.U.A.

  14. Acknowledgements I would like to thank: • University Professor, Evangelos N. Gazis • Dr Rachel-Maria Avramidou, and • Dr Rob Veenhof Mermigka Kalliopi - N.T.U.A.

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