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Assembly Precision and Alignment Knowledge in SMT/STT: Implications and Simulation Results

This document discusses the relationship between assembly precision and the knowledge of assembly in the context of silicon mounting simulation methods. It covers results from simulations involving true (non-ideal) geometry and reconstructions with ideal geometry, focusing on the implications of in-situ alignment. Key findings include the necessity of precise knowledge for optimal assembly and the limitations posed by varying tilt angles and distances. The conclusions highlight the need for in-situ alignment to meet assembly requirements effectively.

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Assembly Precision and Alignment Knowledge in SMT/STT: Implications and Simulation Results

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  1. STT & SMT Assembly Precision • Method • Results • no in situ alignment • w/in situ alignment • Conclusions Stress difference between assembly precision and knowledge of assembly Hobbs, Silicon Mtng

  2. Simulation Method • Tests • Generate tracks with “true” (non ideal) geometry • Reconstruct with different(ideal) geometry • Simple simulation • Correct SMT geometry (RECO) • Intersect helices and ladders • STT will use alignment • f, every cluster (zL=0) • r, avgs. in matrices (look up) Caveat: STT group not approved this yet... Hobbs, Silicon Mtng

  3. Move detector in X by 30 mm Tilt detector about X by 100 mrad Code Sanity Checks • Look at b(reco)-b(true) vs. ??? Hobbs, Silicon Mtng

  4. Result I: No in situ Alignment This relies completely on assembly precision…* • True, non-ideal for generation • Assume ideal geometry for reco 300 mrad 300 mrad 250 mm 100 mm *This also limits uncertainty on alignment knowledge for positions Hobbs, Silicon Mtng

  5. Result II: Perfect f This relies on assembly knowledge • True (non-ideal) for generation • For reconstruction • true f from true geometry & • matrices(radii) from ideal no problems if dr < 200 mm and tilt < 250 mrad Hobbs, Silicon Mtng

  6. 1 (1+2 )*(1 + )2 1 rc2 df2 = * * (dx2 + drc2) + dfc2 x rc x rc ( ) 2 ( ) 2 x rc ( ) 2 drc = 100 mm drc = 50 mm One line/layer smaller radii, larger effect f Precision (df) • Do we really know df well enough using alignment? • Alignment goal: Doesn’t effect hit resolution by more than 10%... • Look at (limited) effects http://sbhepnt.physics.sunysb.edu/ ~hobbs/alignment/align.pdf X = SMT position (local) rc = Radius at ladder center fc = f at ladder center Layer 1 Layer 8 Hobbs, Silicon Mtng

  7. Conclusions • Assembly requirements interplay with alignment status • Constraints • Knowledge, offsets ^beam 25 mm • Knowledge, radial offsets: 70 mm • Assembly tol., angles 200 mrad • Not met, require in situ alignment. • Time dependence? • Systematics in alignment (CDF)? • Absolute tolerances only on angles Hobbs, Silicon Mtng

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