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Advanced Alignment Techniques for Quadrupoles in CERN's LHC

This document details the alignment procedures for quadrupoles within the CERN LHC, emphasizing the optical paths and challenges posed by the Zerodur spokes used in their construction. It discusses the limitations of alignment methods and the need for external reference systems, as well as the properties of materials used, including thermal expansion coefficients. The text outlines the importance of minimizing spoke deformation, maintaining stability within defined temperature ranges, and achieving high precision in alignment. Insights into material properties and structural requirements are included for engineering effective alignment strategies.

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Advanced Alignment Techniques for Quadrupoles in CERN's LHC

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  1. RasClicQuadrupole Alignment 12-07-2011 Cern

  2. Alignment of Quadrupoles 3m Optical path through these tubes Zerodur spokes within these tubes

  3. Alignment of Quadrupoles • Path of the bundle can not be used for alignment purposes, as this would reduce the amount of time available for the experiment. • Use of external reference (ground) would introduce additional errors => transfer Quadrupole position to outside of magnets.

  4. Alignment of LHC - Alignment of pipe sections Low CTE spokes Thin, vulnerable spokes. RasClic components at spoke end • Large amount of spoke bending requires support with aluminum/ carbon fibre tubes

  5. Reference Rings • Zerodurrefence rings All dof constraint Vertical dof constraint

  6. RasClic at end of spokes

  7. Meeting the requirements • Temperature range in Quadrupole Structure: 15 – 25oC • => Spoke-to-spoke deviation in expansion << 1um.

  8. PropertiesZerodur: • r = 2.53g/cm^3 = 25300 kg/m^3 • E20oC=90.3GPa,n=0.243 • afe – 3 categories: • Class 0: 0+/- 0.02x10-6/K • Class 1: 0+/- 0.05x10-6/K • Class 2: 0+/- 0.10x10-6/K • Company: Schott • Rods of 6mm x 6mm square cross-section with a maximum length of 200mm. Goal: 3m • => Requires gluing of several sections of rod.

  9. Quadrupole Reference Ring

  10. Quadrupole Reference Ring - deformation • Deformation under its own weight – 1.3um deformation. • Not absolute deformation, but ring-to-ring variation is important.

  11. Spoke test structure Rubber flexo Zerodur spoke Al tube

  12. Press-fit Spoke is pressed against flat reference block, which has been orderedRequirement: well-defined force and therefore deformation Or Demand:Within 0.1 um reproducable

  13. Guiding spoke in tubes

  14. Guiding spoke in tubes - 2

  15. Flexo - Mesh

  16. Flexo F

  17. Flexo flexible enough – hand calculation Say:

  18. Thermal expansion of AL tube w.r.tZerodur spoke • CTEZerodur

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