1. April 15, 2002 NIKHEF-1 Hans de Vries Status RF foil Projects in progress: Rectangular bellows Wakefieldsuppressors EMI measurements RF/vacuum foil  Production methods used  Coating  Results and conclusions  Interference Silicons

2. April 15, 2002 NIKHEF-2 Hans de Vries VELO Overview Bellow Wakefield suppressor EMI pick –up Cabling RF foil box

3. April 15, 2002 NIKHEF-3 Hans de Vries Rectangular Bellow (1)

4. April 15, 2002 NIKHEF-4 Hans de Vries Rectangular Bellow (2)

5. April 15, 2002 NIKHEF-5 Hans de Vries Rectangular Bellow (3) Assembled last week Vacuum brazed this weekend Tests to be performed: Vacuum tightness Mechanical behavior (10,000 movements)

6. April 15, 2002 NIKHEF-6 Hans de Vries Wake field suppressors The Wake field suppressor is made of two 75 m m thin CuBe foils, compressed with gear wheel and rack. CuBe is chosen for the good electrical and elastic properties. The foil can be hardened at 320º C to get better spring properties. Amount of material will be optimized.

7. April 15, 2002 NIKHEF-7 Hans de Vries Wakefield Suppressor test The CuBe 2 Wake Field suppressor has been tested for 30.000 cycles. No cracks or other damage was observed

8. April 15, 2002 NIKHEF-8 Hans de Vries RF-test: EMI effects (1)

9. April 15, 2002 NIKHEF-9 Hans de Vries RF-tests: EMI effects (2) No signal observed for Al foil of 25 m m Study of RF pick-up in silicons and read-out electronics

10. April 15, 2002 NIKHEF-10 Hans de Vries Cabling Cables inside vacuum: Heat production Signal shielding Kapton with 3 Cu layers: Outer layers for power and ground Inner layer for signal Very expensive! New design has been made to optimize nr. of kapton sheets required

11. April 15, 2002 NIKHEF-11 Hans de Vries VELO RF/vacuum box

12. April 15, 2002 NIKHEF-12 Hans de Vries RF and vacuum separation foil(1) Why? Separation extreme-high-vacuum of LHC from Detector vacuum (outgassing electronics, cables,…!) Stiffness Protect against RF effects Wakefields in Vertex vessel EMI in detectors Good conductivity Physics requirement: Restrict amount of material –preferably low-Z (small radiation length) Detectors should overlap –Alignment –Stereo angle

13. April 15, 2002 NIKHEF-13 Hans de Vries RF and vacuum separation foil(2) Shape and material choice: Physics –Thin-walled “Roman pots” around detectors Wakefields –Small cylindrical aperture Compromise: –Corrogated structure –Toblerone shape Material: –Beryllium too expensive –Aluminum has been chosen Thickness: –Rigidity and conductance vs. low-material budget: < 300 m m Al

14. April 15, 2002 NIKHEF-14 Hans de Vries RF and vacuum separation foil(3) Production of the toblerone: Machining from solid material: In the sub-mm region for a 1200 mm long structure we expect: Accuracy problems Stress (frequent annealing) Production from foil: Requirements for: Stiffness Welding Shape Choice of material Methods to be used

15. April 15, 2002 NIKHEF-15 Hans de Vries RF foil box

16. April 15, 2002 NIKHEF-16 Hans de Vries Production of RF foil Methods investigated: –Cold formation Press- anneal at 420°- cool- press … –More than 15 cycles, 2 – 100 bar –Two or more molds –Superplastic deformation Deform at 520° –One cycle, p  10 bar –Explosive formation –Cold formation Annealing at 320°

17. April 15, 2002 NIKHEF-17 Hans de Vries Cold formation(1) Oct, 2000 0.25 mm 99% Al - 12 steps - 9 to 40 bar Between each step the plate is 20 min annealed at 420º C. Surplus of material Buckling and folding

18. April 15, 2002 NIKHEF-18 Hans de Vries Cold formation(2) April, 2001 0.25mm 99%Al : shaped in 2 steps. Step 1: formed the round shape, with 2 pressure steps from 15 to 20 bar. Step 2: 30 pressure steps from 10 to 32 bar. - No more folds in the middle round shape. - Crystal structure.

19. April 15, 2002 NIKHEF-19 Hans de Vries Cold formation(3) May, 2001 0.28 mm 99%Al Thickness of the deformed material: Large thickness variations: Minimal thickness 0.11 mm. Small cracks and pinholes.

20. April 15, 2002 NIKHEF-20 Hans de Vries Cold formation(4) June 10, 2001 New material: 0.3mm AlMg3 shaped in 2 molds. Final pressure: 95 bar without cracks. Between each pressure step the plate is a annealed at 520º Celsius. Radius less than 8 mm, but this shape is not reproducible

21. April 15, 2002 NIKHEF-21 Hans de Vries Cold formation(5) July 9, 2001 0.3 mm AlMg3 Shaped with 2 molds. The maximum pressure in step 2 is 60 bar. Between each pressure step the plate is a annealed at 520º C. The foil cracked at 65 bar on the 'sharp' edge. Radius = 13 mm. Strong crystal growth!

22. April 15, 2002 NIKHEF-22 Hans de Vries Plastic deformations So-far we used plastic deformation For pure Al: 30% at room temperature 60% at 200º C We need deformations of 400%: annealing steps required Principal mechanism: Dislocation creep High dislocation density Grain elongation Cavity formation Induces multiplication and gathering of dislocations Cavitation is important cause of failure

23. April 15, 2002 NIKHEF-23 Hans de Vries Superplastic Forming(2) September, 2001 Aluminium Superplastic Forming (SPF) Hot stretching process: sheet of superplastic grade aluminium alloy is forced onto or over a single surface tool by the application of air pressure. Typical temperatures T = 470 - 520° C Requirement: small grain size (<10 m m) bubble or cavity forming Al alloys for integral solutions with: low weight high stiffness

24. April 15, 2002 NIKHEF-24 Hans de Vries Superplasticity(1) Superplasticity: Polycristalline solids which have the ability to undergo large uniform strains prior to failure Elongations: 200% - 5500% Fine grain size (< 10  m) Strain rate change 10 -5 – 10 -1 /s T > 0.5 T m Discovered in 1920 (Pb-Zn, Cd-Zn) not much interest in the West. 1947: sverhplastichnost John Pillings and Norman Ridley Superplasticity in crystalline solids

25. April 15, 2002 NIKHEF-25 Hans de Vries Superplasticity(5) Mechanisms: Not quite well understood Grain boundary sliding Grain rotation Partial melting Uniform strains Grain size effects Presence of “dispersoids” like Mn, Zr, … –Al 6 Mn and Al 3 Zr act as grain boundary pinning agents Better performance for: Increasing temperatures Decreasing grain size Strain enhanced grain growth is widespread problem in SPD!

26. April 15, 2002 NIKHEF-26 Hans de Vries Superplasticity(6) What is the effect of the Magnesium addition? Atomistic models: Embedded Atom Method Energy Functions Calculations of total internal energy of crystals Calculation of grain boundary energy and surface energy GBS more favorable than void formation Migration: In pure Al3 layers9 Angstrom Al-Mg alloys4 layers13 Angstrom

27. April 15, 2002 NIKHEF-27 Hans de Vries Superplasticity(7) Laboratory research: Small scale, small samples Mainly 2D-elongations Commercial firms: Al-Cu-Zn alloys not weldable! Special patents Expensive tools! Control of many variables –Special additions like Zr –Equal Angle Channel Extrusion for homogeneous material –Special heat treatment during rolling process Thickness used is normally 2 – 3 mm no experience 100 m m Black Magic: sometimes conflicting advices

28. April 15, 2002 NIKHEF-28 Hans de Vries Superplasticity(8) Deformations: No sharp corners: Superplasticity, while capable of reproducing fine details, cannot produce very sharp corners. Careful considerations needs to be given to determining the minimum radii of curvature that can be sustained without excessive thinning or wrinkling of the sheet. Other problems: Cavitation and fracture We have 3D deformations. At strongest radii small leaks and/or pin holes were found.

29. April 15, 2002 NIKHEF-29 Hans de Vries SPD mold (1)

30. April 15, 2002 NIKHEF-30 Hans de Vries SPD mold (2)

31. April 15, 2002 NIKHEF-31 Hans de Vries Samples from the regions(1)

32. April 15, 2002 NIKHEF-32 Hans de Vries Samples from the regions(2) 100 m m Neutral part no deformations

33. April 15, 2002 NIKHEF-33 Hans de Vries Samples from the regions(3) 100 m m Outer part Intermediate deformations

34. April 15, 2002 NIKHEF-34 Hans de Vries Samples from the regions(4) 100 m m Inner part Largest deformations

35. April 15, 2002 NIKHEF-35 Hans de Vries Elasticity tests RF foils(1) Elastic behavior: 300 m m foil Deformation: 320  m at +15 mbar 200  m at -15 mbar Completely elastic N.B.: Unfortunately, in the presentation there was a factor 10 off in the quoted values for the deflection.

36. April 15, 2002 NIKHEF-36 Hans de Vries Elasticity tests RF foils(2) April 16, 2002 Two more foils have been tested: AlMg3 Foil 0.2mm thick over under pressure [mbar]deflection [mm]pressure [mbar]deflection [mm] 3 0.2 2.4 0.2 5 0.33 0.3 7 0.44,5 0.4 9 0.55 0.5 10 0.556 0.6 AlMg3 Foil 0.28mm thick (CERN material) overunder pressure [mbar]deflection [mm]under pressure [mbar]deflection [mm] 3 0.13 0.1 6 0.25 0.2 9 0.36.5 0.3 10 0.338 0.4 10 0.5

37. April 15, 2002 NIKHEF-37 Hans de Vries Leak rate 19 forming steps, 3 molds needed. 7.0 E-8 -> 7.0 E-7 1 corner= 8.0 E-5 1 forming step at 520º C 9.8 E-6 -> 2.0 E-5

38. April 15, 2002 NIKHEF-38 Hans de Vries Coating The extreme deformation results 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

39. April 15, 2002 NIKHEF-39 Hans de Vries Final solution(?) 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 BeforeAfter 1.2e-33.2e-7 1.2e-57.2e-7 3.6e-55.2e-7 3.8e-52.4e-6 1.2e-63.2e-7

40. April 15, 2002 NIKHEF-40 Hans de Vries Statement producer: Uniform thickness after deformation. Test have been performed. Explosive Formation(1)

41. April 15, 2002 NIKHEF-41 Hans de Vries Explosive Formation(2) The explosive sandwich method. Pure aluminium Aluminium + 3% Mg

42. April 15, 2002 NIKHEF-42 Hans de Vries Full size mold Produced at VU by Frans Mul

43. April 15, 2002 NIKHEF-43 Hans de Vries Summary & Outlook Base solution for RF/vacuum foil obtained –Material: 200  m Al with 3% Mg –Minimal radius 8 mm (cold formation and SPD) –Tolerances estimated to be 1 mm –Application of poly-amide-imide: Vacuum tight Intrinsically baked out Only applied inside the secondary vacuum Good electric insulation Radiation resistant More layers can be applied Can be used as glue –Full scale box will be produced before summer

44. April 15, 2002 NIKHEF-44 Hans de Vries RF foil and Silicons Black: Detector Red: Rf foil Blue: region for detector, assuming 1 mm clearance

45. April 15, 2002 NIKHEF-45 Hans de Vries RF foil and Silicons-detailed