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Status RF foil

Status RF foil. RF/vacuum foil Purpose Production methods used Deformations: static - overpressure Electrical properties Coating Cables Interference Silicons. Protect against RF effects Wakefields in Vertex vessel EMI in detectors Good conductivity. RF and vacuum separation foil(1).

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Status RF foil

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  1. Status RF foil • RF/vacuum foil • Purpose • Production methods used • Deformations: static - overpressure • Electrical properties • Coating • Cables • Interference Silicons

  2. Protect against RF effects Wakefields in Vertex vessel EMI in detectors Good conductivity RF and vacuum separation foil(1) Why? • Separation extreme-high-vacuum of LHC from Detector vacuum • (outgassing electronics, cables, NEG coating,…!) • Stiffness Physics requirement: • Restrict amount of material • preferably low-Z (small radiation length) • Thin • Detectors should overlap • Alignment • Stereo angle • Complicated shape

  3. RF and vacuum separation foil(2) • Production from foil • Requirements for: • Stiffness • Welding • Thickness • Shape • Choice of material • Methods to be used

  4. RF foil and Silicons

  5. VELO Overview

  6. Secondary vacuum box

  7. Material data Material: AlMg3 Young's modulus: 70.000 MPa Poisons ratio: 0.33 Shear Modulus: 27.3 GPa Yield Strength: 80-180 MPa Ultimate Strength: 180-260 MPa Electrical conductivity: 1.9x107 ohm-1 m-1 (almost 50% of pure Al) Weldable!

  8. Production of RF foil • Methods investigated: • Cold formation • Press- anneal at 420° (or 350 °) - cool- press … • More than 15 cycles, 2 – 100 bar • Two or more molds • Hot gas forming • Deform at 350° • Time consuming • Explosive formation • Uncontrolled • Superplastic deformation • Deform at 520° • One cycle, p  10 bar • Crystal growth, melting, • Vacuum leaks • Formation speed, • Temperature

  9. Hot gas forming

  10. Full size foil Vacuum tight foil from 300 µm AlMg3 Buckling in the center toblerones is solved Ribs (2.5mm high) are added at the forward-end to increase the stiffness.

  11. 3D measurement set-up Exploded view

  12. Measurement of one slot 20 x 5 measurement points

  13. 3D result for one slot

  14. Projection for one slot Variation in depth of one slot ± 0.1 mm

  15. Minimum depth along foil

  16. Minima enlarged Variation in depth for all slots: ± 0.2 mm

  17. Close-up minima Position of slots along foil: 0.1 mm

  18. Central region • Interference Si and rf foil: • Minimum radius • Saddle point Variation 0.2 mm

  19. Thickness measurements Along central beam line: 0.28 0.29 0.27 mm 0.24 0.27 0.25 0.26 0.30 0.27 0.24 0.27 mm Largest curvature point: 0.15 mm

  20. FEM analysis: input Input model for the FEM calculations

  21. FEM analysis: down 10 mbar over pressure in primary vacuum Maximum deflection 0.88 mm in “floppy part” of foil

  22. FEM analysis: up 10 mbar over pressure in secundary vacuum Maximum deflection 1.04 mm in “floppy part” of foil

  23. Deflection measurement

  24. FEA for full box (1)

  25. FEA for full box (2)

  26. FEA for full box (3)

  27. FEA for full box (4)

  28. RF foil and Silicons-reinforcements

  29. RF shielding Frans Kroes has produced a note on Attenuation of an EM field by AlMg4 screen of 0.2 mm Conclusion: Assuming a conductivity of 0.33 of pure Al: At 1 mm distance to the rf screen: 1.415 x 10-3 V/m

  30. Conductivity • Pure Al = 37 x 106 Ohm-1 m-1 • Measured (accuracy 10%) conductivity of 1 m long 1 cm wide strips of AlMg3: • undeformed = 17 x 106 Ohm-1 m-1 • deformed = 11 x 106 Ohm-1 m-1 • 45% for undeformed • 30% for deformed material

  31. Coating (1) • The extreme deformation might result in tiny leaks in the material. • Also a protective layer might be used at the inside of the detector box. • Apply poly-amide-imide coating • Solution in N-Methyl-2-Pyrrolidone (NMP) • Drying and polymerization at 60º, 150º, 260º and 315º C • Properties like Kapton and Torlon • Good electric insulation • Radiation resistant 30 MGy, strength not changed • Outgassing properties have been studied

  32. Coating (2) A thin layer of poly-amide-imide is air brushed on the inside of the foil for electrical protection and to increase vacuum tightness Effect of the layer: Leak detection With Helium Before After 1.2e-3 3.2e-7 1.2e-5 7.2e-7 3.6e-5 5.2e-7 3.8e-5 2.4e-6 1.2e-6 3.2e-7

  33. Outgassing (1) Outgassing poly-amide-imide coating

  34. Outgassing (2) Poly-amide-imide coating: 1.5 m2 Kapton cables: 20 m2

  35. Summary and outlook • Full size RF/vacuum foil has been obtained • Material: 300 mm Al with 3% Mg • Minimal radius 8 mm • Deviations measured: ± 0.3 mm • FEM analysis has been performed • Variations measured for 10 mbar overpressure • Electrical properties measured

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