1. X-Ray Survey of The ATLAS SCT

2. The ATLAS Semi-Conductor Tracker

3. Alignment Requirements  Alignment should not degrade track parameter measurements by more than 20%  Mis-alignment of SCT must fall within the following tolerances 1220050 SCT Forward 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  Module positions can be inferred from shape of support structure  Provide a starting point for Track Alignment  Allows for much faster alignment parameter fixing

6. X-ray Survey Overview

7. The Scanning Head Optical strip reader Linear Motion BM250 Rotary Motion ADR200 X-Ray Assembly

8. Barrel Scan  Ø and Z fixed by scanning head  R found through use of stereo angle between X-Ray collimators

9. Linear Motion  8 pole induction motor  25:1 ratio gear box  Rubber Wheel Linear Motion BM250 Scanning Head BM250 motor Gear Box Rubber Wheel Rail

10. Optical Strip Reader  1.6m Long Scale Strip  RGH25 Read Head  RGB25 Signal Processor  Maximum Spatial resolution of 5μm Resolution 5μm Signal Period 20μm RGH25 Read Head

11. Forward Scan θ SCT Forward Section Z Axis X-Ray Beam Scanning Head  No need to vary θ continuously, use 2 or 3 fixed angles and vary Z  Simpler and more cost effective  Recent simulation indicates improved accuracy

12. Summary  Positioning System is now functional  Currently assembling hardware required for calibration  Laser Alignment System for Scanning Head still to be completed  Projected date for survey late 2005