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S. Guragain , G. Baksay, M. Hohlmann Florida Tech

First Reconstruction Results on the Alignment of Muon Endcap Chambers in the CMS Experiment at CERN. S. Guragain , G. Baksay, M. Hohlmann Florida Tech. 74 th Annual meeting of SESAPS, Nashville, TN, Nov 8-10, 2007. CMS detector of LHC @ CERN. C ompact M uon S olenoid. ME -. ME+2. ME+3.

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S. Guragain , G. Baksay, M. Hohlmann Florida Tech

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  1. First Reconstruction Resultson the Alignment of Muon Endcap Chambers in the CMS Experiment at CERN S. Guragain, G. Baksay, M. Hohlmann Florida Tech 74th Annual meeting of SESAPS, Nashville, TN, Nov 8-10, 2007

  2. CMS detector of LHC @ CERN Compact Muon Solenoid ME - ME+2 ME+3 ME+1 ME+4 Z+ CMS solenoid -13 m long Magnetic field - 4 Tesla Total weight - 12500 t Overall diameter -15 m Overall length - 21.6 m Muon Endcaps S. Guragain - SESAPS meeting, Tennessee Yokes

  3. A part of CMS Ref. DCOPS 2 Crosshair Lasers (adjustable) Z-sensors Z-tube Back Chamber Chamber DCOPS’s Laser beam Clinometer Transfer Plate Mounting Tower Transfer Line DCOPS R-sensor Laser on ! ZCMS RphiCMS ME+2 SLM S. Guragain - SESAPS meeting, Tennessee

  4. Full Reconstruction Model Z-sensors Clinometers Transfer plate Lasers Note: only small sample of analog sensors shown SLM currently under study (ME+2 SLM 2-5) R-sensors DCOPS’s The system monitors the positions of CSCs relative to each other and to the MABs Lasers Straight Line Monitors (SLMs) and Transfer lines Chamber resolution 75 micron for ME1/2 and 150micron for other. S. Guragain - SESAPS meeting, Tennessee

  5. Basic strategy • Fit DCOPS data at B=0T and reconstruct DCOPS and CSC positions using COCOA(CMS Object-oriented Code for Optical Alignment) • Check B=0T reco results for one SLM against photogrammetry (PG) in full detail and with great care until we can trust the reconstruction • Quantify precisions and accuracies • Reconstruct DCOPS & CSC positions at B=4T • Apply lessons learned to reco of other SLMs S. Guragain - SESAPS meeting, Tennessee

  6. Simultaneous fit in zCMS for two lasers in ME+2 SLM2-5 at B=0T First CCD pixels Laser hits (shifted to the sides of CCDs for display) bad hits not used in fit CCD2 CCD4 CCD4 CCD2 fitted position B=0T laser line fit laser line fit Simultaneous fitting of 2 lasers with hits that overlap on 4 central DCOPS’s is now working ! DCOPS CCDs Ref. CCD Ref. CCD Note: In MTCC 2006 the lasers were tilted towards the CSCs on purpose to compensate for disk bending at B=4T ! S. Guragain - SESAPS meeting, Tennessee

  7. Fit Residuals Precision in zCMS (“z-resolution”) ≈ 60 m S. Guragain - SESAPS meeting, Tennessee

  8. Shim delta Reconstructed DCOPS & CSC Positions and their Precision Reconstructed positions of outer CSC PCB skins zreco~ 270 m B=0T Dowel pins PG of TPs determines global zCMS position of entire system New shim New shim Reconstructed tops of CSC Alignment pins First CCD pixels CCDs Note: In this coordinate system the DCOPS are “up-side-down” (ME+2 DCOPS tops are at smaller zCMS) Reconstructed tops of DCOPS boxes S. Guragain - SESAPS meeting, Tennessee

  9. Now, accuracy … S. Guragain - SESAPS meeting, Tennessee

  10. Perfect ! Accuracy check of ABSOLUTE positions against PG at B=0T Reconstructed positions of outer CSC PCB skins (no PG avail.) PG measurements of coded targets on outer CSC PCB skins PG of TPs determines global zCMS position of entire system Solid triangles: Reconstructed tops of CSC Alignment pins Open triangles: PG meas. of CSC Alignment pins First CCD pixels B=0T Reco and PG now match well !!! CCDs Solid triangles: Reconstructed tops of DCOPS boxes Open triangles: PG measurement of tops of DCOPS boxes S. Guragain - SESAPS meeting, Tennessee

  11. Discrepancy in Z between PG and Fitted positions 683 micron S. Guragain - SESAPS meeting, Tennessee

  12. Reconstruction of zCMS for CSCs in ME+2 SLM2-5 at B=4T B=0T fit positions ~ 13mm B=4T fitted CSC positions B=4T Disk bending is reconstructed ! This assumes (incorrectly) that the TP’s do not shift in z & do not rotate! S. Guragain - SESAPS meeting, Tennessee

  13. Summary • Reconstruction of zCMS coordinate is working • Z-resolution & Sensitivity to relative motion≈ 60 m • Z-precision of reconstructed CSC centers ≈ 270m • Z-accuracy of reconstruction ≈ 680 m (Comparison with Photogrammetry data) Accuracy required by design 1 mm • Disk bending at B=4T is reconstructed THANKS S. Guragain - SESAPS meeting, Tennessee

  14. Back up slides S. Guragain - SESAPS meeting, Tennessee

  15. ME+2 Disk S. Guragain - SESAPS meeting, Tennessee

  16. Beam Profiles measured with CCDs 2 & 4 in ME+2 SLM2-5 for both Lasers Laser 2 CCDs 2 in 10 DCOPS Laser 5 Pt.5 Pt.2 Good hits ! One MTCC2 alignment event: Nov 3, 2006 00:01:16:48 Laser 2 CCDs 4 Laser 5 Laser Beam Profiles supplied by Jim Bellinger S. Guragain - SESAPS meeting, Tennessee

  17. Reconstructing ABSOLUTE CSC zCMS- coordinates via DCOPS geometry… All dimensions in mm Top of DCOPS box DCOPS Side View CCD Allowed Laser Range CCDs 2 & 4 nominal zCMS- position for SLM z-coordinate of first CCD pixel (14 m/pixel × 1024 pixels) + DCOPS foot z-reference surface for DCOPS dowel pin (new!) center Dowel pin (precision element) updated CAD Drawing by Dave Eartly – 10/15/07 S. Guragain - SESAPS meeting, Tennessee

  18. 38.194 … CSC geometry… Top of DCOPS box z-coord. of PG Target on top of DCOPS box CCD nominal zCMS- position for SLM z-coordinate of first CCD pixel DCOPS foot z-reference surface for DCOPS dowel pin Mounting bar coded PG target lives here ! Mounting plate Shim CSC z-reference surface for al. reco (new!) top CSC PCB panel CSC frame updated CAD Drawing by Dave Eartly – 10/15/07 S. Guragain - SESAPS meeting, Tennessee

  19. …and Transfer Plate (TP) geometry Transfer Line DCOPS SLM Reference DCOPS Laser 6.73 (newly found shim !) TP ref. surface (also for PG) updated CAD Drawing by Dave Eartly – 10/17/07 S. Guragain - SESAPS meeting, Tennessee

  20. Sanity check on Precision as returned by Reconstruction All errors in microns ok ! All tolerances In this column under review ! Precision dominated by mechanical tolerances and not by spread of laser hits in fit (60 m res.) ! S. Guragain - SESAPS meeting, Tennessee

  21. Effect of missing hits Simulate effect of missing laser hits (e.g. due to shadowing) on the reco results by manually inflating errors on good hits This Example: Turn one good hit into a bad hit on two separate DCOPS on the same chamber Result: This has only a small effect on the overall fit and reconstructed positions ! S. Guragain - SESAPS meeting, Tennessee

  22. Effect of missing hits cont’d S. Guragain - SESAPS meeting, Tennessee

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