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