X-ray Survey of the ATLAS SCT Hardware Overview Nick Brett and Jim Loken

Nick Brett – University of Oxford 2 The ATLAS Semi-Conductor Tracker

Nick Brett – University of Oxford 3 Alignment Requirements  Alignment should not degrade track parameter measurements by more than 20%  Mis-alignment of SCT must fall within the following tolerances SCT Forward SCT Barrel Rø(μm)Z(μm)R(μm)

Nick Brett – University of Oxford 4 Alignment Techniques  Initial X-Ray Survey  Frequency Scanning Interferometry  Track-Based Alignment Procedures

Nick Brett – University of Oxford 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  Compliment Track Alignment  Provides an initial geometry  Identify otherwise unrecoverable distortions

Nick Brett – University of Oxford 6 X-ray Survey Overview

Nick Brett – University of Oxford 7 The Scanning Head Optical strip reader Linear Motion BM250 Rotary Motion ADR200 X-Ray Assembly

Nick Brett – University of Oxford 8 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

Nick Brett – University of Oxford 9 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

Nick Brett – University of Oxford 10 R Measurement  Ø and Z fixed by scanning head  R found through use of stereo angle between X-Ray tubes Scanning head in calibration stand SCT barrelX-ray beam

Nick Brett – University of Oxford 11 X-rays on silicon Problems low Interaction probability digital readout Solutions Use long integration window (x-ray mode) Multiple triggers for each beam position strip position (Rø) hits

Nick Brett – University of Oxford 12 Module response narrow beam wide beam strip position (Rø) hits Problem  Non-uniform response to x-rays Solution  Use wide beam to measure response  Modulate narrow beam accordingly

Nick Brett – University of Oxford 13 Calibration X-Ray Beam Optical Table SCT Module (In transport case) Z Axis

Nick Brett – University of Oxford 14 Calibration

Nick Brett – University of Oxford 15 Calibration

Nick Brett – University of Oxford 16 Summary  Proposed x-ray survey would occur during construction of ATLAS  Data could be used to remove ambiguities in other alignment techniques  Calibration of hardware is proceeding well  Actual deployment is unlikely

Nick Brett – University of Oxford 17 Backup Slides

Nick Brett – University of Oxford 18 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

Nick Brett – University of Oxford 19 Support tube and cooling

Nick Brett – University of Oxford 20 Module support