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X-Ray Survey of
The ATLAS SCT
The ATLAS Semi-Conductor Tracker
Alignment Requirements
Error in Track Parameter measurements should not exceed 20%
Miss-alignment of SCT must not exceed the following tolerances
1220050SCT Wheels
1250 100SCT Barrel
Rø(μm)Z(μm)R(μm)
Alignment Techniques
Initial X-Ray Survey
Frequency Scanning Interferometry
Track-Based Alignment Procedures
Aims of The X-Ray Survey
Produce a map of the SCT modules Calibrate the FSI system Provide a starting point for Track
Alignment
X-Rays and SCT Modules
SCT modules not optimised for X-Rays Wide beam used to
compensate
Beam profile sacrifices Z resolution
Strip position (Rø)
Sig
na
le
50μm
2mm
X-ray Survey Overview
Positioning the Scanning Head
Z – Positioning Stage
Ø - Positioning Stage
X-Ray Assembly
Optical strip reader
Laser Alignment
Barrel Survey
Ø and Z fixed by scanning head
R found through use of stereo angle between X-Ray tubes
End Cap Survey
Different X-Ray assembly required
Ø and Z fixed by scanning head
R found by Illuminating modules from two Z positions
Rθ1 θ2Z – axis
Z1 Z2
Summary
X-Ray Survey is an alignment procedure for the ATLAS SCT
X-Ray trajectories follow those of actual events
The Majority of the hardware is already in place