Alignment Activities for ATLAS at MPI
To provide a precise measurement of the muon tracks in the ATLAS
muon spectrometer it is essential to know the relative position of the
chambers along the track of the muon by a precision less than the
intrinsic resolution of the chambers. Also it is necessary to know the
chamber deformation (due to gravity) to extract the actual wire position.
Therefor the relative position and the actual deformation
of the chambers will monitored all the times by a sophisticated
alignment system.
The chamber deformation is monitored by an optical in-plane
alignmet system based on RASNIKs which can measure the relative
movement of the cross plates, but is not sensitive to expansions along
the wire axis.
The chamber position is in the barrel derived form a projective
system (projective to the interaction point) for towers of ~2 chambers
in the theer layer combined with an axial system for neighbouring
chambers.
For the end caps a grid is used that consists of reference bars -
alignment bars - connected to each other by azimuthal and polar
monitors. The relative position of the chambers is reconstructed by
monitoring the position of them wrt the alignment grid using BCAMs.
To get reliable results also the deformation of the alignment bars has
to be taken into account. Therefor an optical in-bar system is
implemented in the bar. At the moment a ste of 3-4 RASNIKs is used in
this purpose. But also a system of 2 BCAMs looking at several light
points in the bar might be possible und is under study.
In the design of the alignment bars the MPI is involved.
Pictures are shown below.
Pictures on the alignment bars and the in-bar alignment system
Further links
Alignment Activities for ATLAS at MPI
|
To provide a precise measurement of the muon tracks in the ATLAS
muon spectrometer it is essential to know the relative position of the
chambers along the track of the muon by a precision less than the
intrinsic resolution of the chambers. Also it is necessary to know the
chamber deformation (due to gravity) to extract the actual wire position.
Therefor the relative position and the actual deformation
of the chambers will monitored all the times by a sophisticated
alignment system.
The chamber deformation is monitored by an optical in-plane
alignmet system based on RASNIKs which can measure the relative
movement of the cross plates, but is not sensitive to expansions along
the wire axis.
The chamber position is in the barrel derived form a projective
system (projective to the interaction point) for towers of ~2 chambers
in the theer layer combined with an axial system for neighbouring
chambers.
For the end caps a grid is used that consists of reference bars -
alignment bars - connected to each other by azimuthal and polar
monitors. The relative position of the chambers is reconstructed by
monitoring the position of them wrt the alignment grid using BCAMs.
In the design of the alignment bars the MPI is involved.
Pictures are shown below.
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Pictures on the alignment bars and the in-bar alignment system
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Further links |
