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VELO Mechanics RF/vacuum foil Rectangular bellow Wake field suppressors Cabling Summary & Outlook

VELO mechanical aspects. VELO Mechanics RF/vacuum foil Rectangular bellow Wake field suppressors Cabling Summary & Outlook. 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

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VELO Mechanics RF/vacuum foil Rectangular bellow Wake field suppressors Cabling Summary & Outlook

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  1. VELO mechanical aspects • VELO Mechanics • RF/vacuum foil • Rectangular bellow • Wake field suppressors • Cabling • Summary & Outlook

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

  3. RF and vacuum separation foil • Separate prim. and sec. Vacuum • Stiffness • Protect against RF effects • Wakefields • EMC • Restrict amount of material • Overlapping detectors • stereo angle • alignment

  4. RF foil box – outside view

  5. RF foil box – inside view

  6. FEA on Al. 250 mm 0.25 mm top plate 0.5 mm side plates 15 mbar max. displacement 0.35 mm max. stress [MPa] 58.8 MPa

  7. Thin RF/vacuum foil 2000 2001 Aluminum (250 mm thick): • FEA: max p 15 mbarirreversible 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

  8. 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

  9. SPF mold (1)

  10. SPF mold (2)

  11. Latest RF foils Deformation: 32 mm at +15 mbar 20 mm at -15 mbar Completely elastic He leak tested Concrete mold has been replaced by a brass one

  12. Explosive Formation Statement producer: Uniform thickness after deformation. Test will be performed.

  13. Rectangular Bellow (1)

  14. 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.

  15. Rectangular bellow (3) The forming mold with the pressure envelope. The pressure envelope is used to keep the system in place.

  16. Rectangular bellow (4) With nitrogen at a pressure of 10 bar the diaphragm are deformed into the right shape.

  17. Rectangular bellow (5)

  18. 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.

  19. Install wake field suppressors after mounting 2ary 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

  20. 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.

  21. Wake field suppressors (3) New design of the The Wake Field Suppressor, which follows better the contour of the beam pipe..

  22. Cabling (1) Almost solid cable tree! • Cables • Connectors • very expensive!

  23. 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

  24. Cabling(3)

  25. Summary & Outlook • Base solution for RF/vacuum foil • 300 mm base material Al with 3% Mg • 170 mm 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

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