Abstract--An extensive system test of the ATLAS muon
spectrometer has been performed in the H8 beam line at the
CERN SPS during the last four years. This spectrometer will use
pressurized Monitored Drift Tube (MDT) chambers and Cathode
Strip Chambers (CSC) for precision tracking, Resistive Plate
Chambers (RPCs) for triggering in the barrel and Thin Gap
Chambers (TGCs) for triggering in the end-cap region. The test
set-up emulates one projective tower of the barrel (six MDT
chambers and six RPCs) and one end-cap octant (six MDT
chambers, A CSC and three TGCs). The barrel and end-cap
stands have also been equipped with optical alignment systems,
aiming at a relative positioning of the precision chambers in each
tower to 30-40 micrometers.
In addition to the performance of the detectors and the
alignment scheme, many other systems aspects of the ATLAS
muon spectrometer have been tested and validated with this
setup, such as the mechanical detector integration and
installation, the detector control system, the data acquisition, high
level trigger software and off-line event reconstruction.
Measurements with muon energies ranging from 20 to 300 GeV
have allowed measuring the trigger and tracking performance of
this set-up, in a configuration very similar to the final
A special bunched muon beam with 25 ns bunch spacing,
emulating the LHC bunch structure, has been used to study the
timing resolution and bunch identification performance of the
Manuscript received October, 26, 2004. This work is supported by the
Israel Science Foundation and the German Israeli Foundation.
E. Etzion is with the School of Physics and Astronomy, Raymond and
Beverly Sackler Faculty of Excat Sciences, Tel Aviv University, Tel Aviv
69978, Israel (telephone: +41764870750, e-mail: firstname.lastname@example.org).
trigger chambers. The ATLAS first-level trigger chain has been
operated with muon trigger signals for the first time.
THE Large Hadron Collider (LHC) currently under
construction at the European Center for Nuclear Research
(CERN) is designed to collide proton-proton beams at the
energy of 7 TeV, the highest energy ever reached in a particle
accelerator. The ATLAS detector built for the LHC
experiment will collect events at a design luminosity of 1034
cm-2s-1 in a proton bunch crossing rate of 40 MHz (3-20
collisions every 25 ns).
The largest part in the ATLAS detector is the Muon
spectrometer . It has been designed to provide a standalone
trigger on single muons with transverse momentum of several
GeV as well as to measure final state muons with a momentum
resolution of about 3% over most of the expected momentum
range; a resolution of 10% is expected at transverse momenta
of 1 TeV. The ATLAS Muon spectrometer is a 4π detector
consists of four types of detector technologies.
Over most of the spectrometer acceptance, Monitored Drift
Tube (MDT) chambers are used for the precision measurement
of muon tracks. The MDTs are built from aluminum tubes
filled with Ar-CO2 at a pressure of 3 bars. Operated at a gas
gain of 2x104, each tube measures charged particle tracks with
an average spatial resolution better than 80 micrometers.
Cathode Strip Chambers (CSC) are used for muon momentum
measurement in the inner part of the end-cap regions where the
background rate is expected to reach 1 KHz/cm2.
15 Nov 2004
System Test of the ATLAS Muon Spectrometer
in the H8 Beam at the CERN SPS
On behalf of the ATLAS Muon Collaboration