MPI für Physik / MPI für Physik |
|Modelling of the Space-to-Drift-Time Relationship of the ATLAS Monitored Drift-Tube Chambers in the Presence of Magnetic Fields|
|Authors:||Dubbert, Jörg; Horvat, Sandra; Khartchenko, Dmitri; Kortner, Oliver; Kotov, Sergei; Kroha, Hubert; Manz, Andrea; Nikolaev, Kiril; Rauscher, Felix; Richter, Robert; Staude, Arnold; Valderanis, Chrysostomos|
|Intended Educational Use:||No|
|Abstract / Description:||The ATLAS muon spectrometer uses tracking chambers consisting of up to 6 m long drift tubes filled with Ar:CO2 (93:7) at 3 bars. The chambers are run in a average|
toroidal magnetic field of 0.4 T created by 8 air core coils. They provide a track point accuracy of 40 µm if the space-to-drift-time relationship r(t) is known with
20 µm accuracy. The magnetic field B influences the
electron drift inside the tubes: the maximum drift time
tmax=700 ns increases by about 70 (ns/T^2)*B^2 .
B varies by up to ±0.4 T along the tubes of the chambers mounted near the magnet coils which
translates into a variation of tmax of up to 45 ns. The dependence of r(t) on B must
be taken into account. Test-beam measurements show that the electron drift in case
of B>0 can be modelled with the required accuracy by a Langevin equation with
a friction term which is slightly non-linear in the drift velocity.
|Classification / Thesaurus:||ATLAS|
|Affiliations:||MPI für Physik|
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