1 / 13

SCT Endcap Module Initial Alignments Using Survey Data

SCT Endcap Module Initial Alignments Using Survey Data. Paul S Miyagawa University of Manchester. Outline. Objectives Available survey data Calculation of alignment constants Comparison with CSC constants Summary and future work. Objectives.

baba
Download Presentation

SCT Endcap Module Initial Alignments Using Survey Data

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SCT Endcap Module Initial Alignments Using Survey Data Paul S Miyagawa University of Manchester

  2. Outline • Objectives • Available survey data • Calculation of alignment constants • Comparison with CSC constants • Summary and future work ATLAS Software & Computing Workshop

  3. Objectives • Extensive survey data available for SCT endcap modules and discs • Combine the survey data to produce “as-built” module-on-disc (level-3) alignments • Compare with the distributions used for CSC production • Use alignments as initial step in alignment algorithms ATLAS Software & Computing Workshop

  4. Module Survey Data (1) • Modules consist of two (or four) wafers mounted at an angle of 40 mrad • (For outer and middle modules, each wafer is split into two parts) • Hole and slot used to mount the module on disc ATLAS Software & Computing Workshop

  5. Module Survey Data (2) • Modules surveyed during assembly at Manchester, NIKHEF and Geneva • Survey information on positions of wafers, hole + slot, angle between wafers • Uncertainties in module construction < O(10 μm) ATLAS Software & Computing Workshop

  6. Disc Survey Data (1) • Modules mounted on disc in three rings • 40 modules each in inner and middle rings, 52 in outer ring • Outer and inner rings mounted on front face of disc, middle ring on rear face • At each position on disc, main/secondary pins insert into hole/slot on module • 2 reference holes define survey coordinates • Holes also used to align discs within the endcap ATLAS Software & Computing Workshop

  7. Disc Survey Data (2) • Discs surveyed during assembly at Liverpool and NIKHEF • Positions of pins and reference holes surveyed on disc • Uncertainties in pin positions O(60 μm) • Should be dominant over module uncertainties ATLAS Software & Computing Workshop

  8. Y x y z X Z Athena Conventions • Level-3 AlignableTrans-forms define translations and rotations of modules in local frame • Centre of rotations taken to be stereo centre on rφ face of module • Strips of rφ face point along radial direction • Strips of stereo face rotated 40 mrad • Transforms are for entire module; not available separately for each face of a module • Cannot reflect shift of stereo centre or non-nominal angle between wafers ATLAS Software & Computing Workshop

  9. Stereo Centre of Module • Stereo centre defined to be intersection of central strips of each wafer • Shift in wafer positions relative to each other causes shift in stereo centre • Positions of overlaps relative to stereo centre are unaffected • Endpoints of strips relative to stereo centre are changed • Leads to inefficiency at one end of strips • Cannot be reflected by AlignableTransforms ATLAS Software & Computing Workshop

  10. Angle Between Wafers • Central axis of module chosen such that angle between wafers is symmetric about nominal angle • Non-nominal angle affects positions of overlaps • Cannot be reflected by AlignableTransforms ATLAS Software & Computing Workshop

  11. Alignment Parameters • Calculated in-plane translations and rotations for modules • Translations < O(100 μm) • Rotations O(400 mrad) • Distributions are (vaguely) Gaussian • Largely determined by positions of pins on disc • Still need to complete verification of data • Using Michal Dwuznik’s viewer • Running alignment algorithm on this set of misalignments ATLAS Software & Computing Workshop

  12. Comparison with CSC Numbers • CSC misalignment set used flat distributions • estimates for CSC misalignments were slightly pessimistic • CSC misalignments are random; survey misalignments are correlated • Relative alignment between modules could be used as a constraint ATLAS Software & Computing Workshop

  13. Summary and Future Work • Extensive survey data available for SCT endcap modules and discs • Uncertainties in module construction < O(10 μm) • Uncertainties in disc construction • Combined survey data to produce “as-built” in-plane level-3 alignments • Translations < O(100 μm) • Rotations O(400 mrad) • Roughly Gaussian distributions • Numbers used for CSC misalignments were slightly pessimistic • AlignableTransforms not available separately for each face of a module • Cannot reflect shift of stereo centre or non-nominal angle between wafers • Work to come • Complete verification of data • Compare reconstruction performance on real data with survey misalignments versus nominal geometry ATLAS Software & Computing Workshop

More Related