1. X-Ray Survey of The ATLAS SCT

2. The ATLAS Semi-Conductor Tracker

3. Alignment Requirements Error in Track Parameter measurements should not exceed 20% Miss-alignment of SCT must not exceed the following tolerances 1220050 SCT Wheels 1250100 SCT Barrel Rø(μm)Z(μm)R(μm)

4. Alignment Techniques Initial X-Ray Survey Frequency Scanning Interferometry Track-Based Alignment Procedures

5. Aims of The X-Ray Survey Produce a map of the SCT modules Calibrate the FSI system Provide a starting point for Track Alignment

6. 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) Signal e 50μm 2mm

7. X-ray Survey Overview

8. Positioning the Scanning Head Z – Positioning Stage Ø - Positioning Stage X-Ray Assembly Optical strip reader Laser Alignment

9. Barrel Survey Ø and Z fixed by scanning head R found through use of stereo angle between X-Ray tubes

10. End Cap Survey Different X-Ray assembly required Ø and Z fixed by scanning head R found by Illuminating modules from two Z positions R θ1θ1 θ2θ2 Z – axis Z1Z1 Z2Z2

11. 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