1. Dec. 4, 2001 CERN-1 Hans de Vries VELO Mechanics  RF/vacuum foil  Rectangular bellow  Wake field suppressors  Cabling Summary & Outlook VELO mechanical aspects

2. Dec. 4, 2001 CERN-2 Hans de Vries Global system design Decouple access to Si detectors from access to 1 ary vacuum Use (ultra)pure neon venting NEGs need not be baked after access to Si detector Baking up to 150 o C is possible Mount two detector halves independently Note large-size, rectangular bellows and thin RF screen 2 ary vacuum 1 ary vacuum air

3. Dec. 4, 2001 CERN-3 Hans de Vries

4. Dec. 4, 2001 CERN-4 Hans de Vries RF and vacuum separation foil Overlapping detectors stereo angle alignment Separate prim. and sec. Vacuum Stiffness Protect against RF effects Wakefields EMC Restrict amount of material

5. Dec. 4, 2001 CERN-5 Hans de Vries RF foil box – outside view

6. Dec. 4, 2001 CERN-6 Hans de Vries RF foil box – inside view

7. Dec. 4, 2001 CERN-7 Hans de Vries FEA on Al. 250  m 0.25 mm top plate 0.5 mm side plates 15 mbar max. displacement 0.35 mm max. stress [MPa] 58.8 MPa

8. Dec. 4, 2001 CERN-8 Hans de Vries Aluminum (250  m thick): FEA: max  p  15 mbar irreversible deform., no safety factor successfully welded 100  m on 300  m press-shaping developed: superplastic forming of AlMg3 “cheap & readily” available (compared to Be) Foil can be produced with radius of 6 mm Sharp edges of detector have to be rounded off Thin RF/vacuum foil 2000 2001

9. Dec. 4, 2001 CERN-9 Hans de Vries Superplastic Forming 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. Discovered in 1920 (Pb-Zn, Cd-Zn) not much interest in the West. 1947: sverhplastichnost http://www.superform-aluminium.com T = 470 - 520° C small grain size bubble or cavity forming

10. Dec. 4, 2001 CERN-10 Hans de Vries SPF mold (1)

11. Dec. 4, 2001 CERN-11 Hans de Vries SPF mold (2)

12. Dec. 4, 2001 CERN-12 Hans de Vries Latest RF foils Deformation: 32  m at +15 mbar 20  m at -15 mbar Completely elastic He leak tested Concrete mold has been replaced by a brass one

13. Dec. 4, 2001 CERN-13 Hans de Vries Explosive Formation Statement producer: Uniform thickness after deformation. Test will be performed.

14. Dec. 4, 2001 CERN-14 Hans de Vries Rectangular Bellow (1)

15. Dec. 4, 2001 CERN-15 Hans de Vries Rectangular Bellow (2) The diaphragms were cut out of a 0.15 mm stainless steel plate with a laser machine. Next the diaphragms have successfully been shaped in a forming mold.

16. Dec. 4, 2001 CERN-16 Hans de Vries Rectangular bellow (3) The forming mold with the pressure envelope. The pressure envelope is used to keep the system in place.

17. Dec. 4, 2001 CERN-17 Hans de Vries Rectangular bellow (4) With nitrogen at a pressure of 10 bar the diaphragm are deformed into the right shape.

18. Dec. 4, 2001 CERN-18 Hans de Vries Rectangular bellow (5)

19. Dec. 4, 2001 CERN-19 Hans de Vries Rectangular bellow (6) 7 stainless steel plates (0.15 mm) will be vacuum brazed together. Before brazing, the 0.05 mm Ni-alloy solder is spot welded between the layers.

20. Dec. 4, 2001 CERN-20 Hans de Vries Install wake field suppressors after mounting 2 ary vacuum container Upstream is “easy”: mounted with large flange off Downstream is more delicate: mount through top flanges 70  m CuBe, O/C, coated Install wake field suppressors after mounting 2 ary vacuum container Upstream is “easy”: mounted with large flange off Downstream is more delicate: mount through top flanges 70  m CuBe, O/C, coated Wake field suppressors (1) Aim: Provide a continuous conducting wall throughout the VELO to guide the mirror charge Aim: Provide a continuous conducting wall throughout the VELO to guide the mirror charge

21. Dec. 4, 2001 CERN-21 Hans de Vries Wake field suppressors (2) The Wake field suppressor is made of two 0.075 mm 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 320 degrees Celsius to get better spring properties.

22. Dec. 4, 2001 CERN-22 Hans de Vries Wake field suppressors (3) New design of the The Wake Field Suppressor, which follows better the contour of the beam pipe..

23. Dec. 4, 2001 CERN-23 Hans de Vries Cabling (1) Almost solid cable tree! Cables Connectors very expensive!

24. Dec. 4, 2001 CERN-24 Hans de Vries Cabling (2) 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

25. Dec. 4, 2001 CERN-25 Hans de Vries Cabling(3)

26. Dec. 4, 2001 CERN-26 Hans de Vries Summary & Outlook Base solution for RF/vacuum foil –300  m base material Al with 3% Mg –170  m at inner region –Radius 6 mm Rectangular bellow –Diaphragms are ready –Will be assembled the coming months Wake field suppressors –The wake field suppressors work fine –A new design is in production Cabling solution available –Has to be discussed further