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Vacuum Chambers & Dipole Magnets for TL-2: Status Report

Detailed report on fabrication, welding, and machining of vacuum chambers and dipole magnets for TL-2 at CTF3. Includes material processes, TIG welding details, and current status. Awaited approvals and future plans discussed.

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Vacuum Chambers & Dipole Magnets for TL-2: Status Report

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  1. STATUS REPORT ON VACUUM CHAMBERS (Dipole & Straight) & DIPOLE MAGNETS FOR TL-2 OF CTF3 A.K. JAIN, S.S. PRABHU,S. KOTAIAH RRCAT, INDORE (INDIA)

  2. Vacuum Chambers

  3. Dipole Vacuum Chambers : Initially, two test vacuum chambers fabricated in aluminum grade AA 6061 for qualifying machining & welding procedure. Surface finish < 0.30 microns achieved. Welding torch manuveres needed to access some portions of chamber. For third chamber, design was changed to simplify welding. Leak rate obtained ~3 x 10-10 Torr – ltr / sec.

  4. DIPOLE VACUUM CHAMBERS Machined & Welded Prototype Chamber Initial Trial Final Trial

  5. DIPOLE VACUUM CHAMBERS

  6. END FLANGES OF DIPOLE VACUUM CHAMBERS

  7. Dipole Vacuum Chambers (Contd…) Fabrication & Processing : Material: AA6061–T6 is silicon magnesium based aluminium alloy. (Material is solution heat treated and artificially aged). Tooling : High-speed cutters were used. Cutters equipped with peripheral mounting, high positive rake angle (340), coated carbide inserts with 900 approach angle. One of three inserts had a “wiper insert” to get good surface finish. Processing : Chemical cleaning-Approved by CERN for aluminium alloy grade AA6061-T6. After chemical cleaning, jobs were hand scrapped in the lip area to remove oxide layer just before welding.

  8. Dipole Vacuum Chambers (Contd…) TIG WELDING : Welders were qualified as per section IX of ASME code. Cleanliness and humidity level of the weld room was maintained using air conditioners, air curtains and Dehumidifiers. Base material used: AA 6061 –T6 ( containing Si- 0.6%, Mg – 1-1.2%, - Cu - 0.27%) Filler wire used: AWS A5.10 ER 4043 (Containing Si–5%, Mn –0.05% Fe – 0.4% Al – rest) Shielding gas used: XL grade argon 99.999% as per IS-5760-1983 (Grade - 1) (Impurities - Oxygen less than 1.5 ppm., Moisture less than 1.0 ppm, total hydrocarbon – NIL)

  9. Welding Parameters Peak current 60-70 Amps. Back ground current 25 Amps. Pulse frequency 7 Hz. (at high position) Pulse Ratio 80% Type of arc Hard Arc Shielding gas flow rate 8 Ltrs / min Relative Humidity Less than 35%

  10. Dipole Vacuum Chambers (Contd…) Present Status : Fabrication and welding procedures qualified. Raw material AA 6061 T6 procured. Awaiting CERN’s approval of TL-2 optics design & also magnet design. Final drawings for chamber fabrication to be taken up thereafter. Total nos. of dipole chambers ~5. Assembly of dipole chamber with bending magnet has been tried using CAD. There is no problem in the assembly.

  11. Straight Chambers : RRCAT, Indore will deliver these chambersbuilt out of extruded aluminum grade AA 6061 T6. This will avoid welding of chambers at the edges and their machining on a CNC vertical milling machine. Extrusion job already ordered. Extruded material expected at RRCAT ~April, 2007. Once TL-2 optics is frozen, material will be cut to required lengths, ends machined to suit the welding joints with end flanges.

  12. Straight Chambers

  13. DIPOLE MAGNETS FOR TL-2

  14. DIPOLE MAGNET Specifications 

  15. Dipole Magnets (Contd…) Magnet Core Material: 1.5 mm thick low carbon steel sheets supplied by M/s Cockrehill Sambre. B/H data and other information : Coercivity – 70 A/m  Carbon content < 0.01 %  Yield Strength 120 N/mm2  Tensile Strength 260 N/mm2  Thickness spread < 1.5 %

  16. Dipole Magnet Bottom Half Block Dipole Magnet Coil Pan Cake

  17. DIPOLE MAGNET ASSEMBLY Overall Mechanical Details of Assembled 35 Dipole Magnet Magnet height 640 mm Magnet Width 1000 mm (812 + 30 + 158) Magnet Length 910 mm Magnet total weight 2200 kg

  18. CORE BLOCK FOR DIPOLE MAGNET

  19. Fabrication Stages: • Laser Cutting of Stampings. • Stacking of stampings & pressing to form a block. • Welding of stampings to get block. • Machining of pole surface & other reference surfaces. • Assembly of two blocks along with water cooled coil pancakes.

  20. Dipole Magnets (Contd…) Present Status : Engineering drawings for 350 bending magnet completed; Sent to CERN, but approval awaited. Quantity required 2 nos. Fabrication will start only after CERN’s approval of drawing. Engg drawings for 17.50 bending magnet completed; will be shortly sent to CERN for approval. Quantity required 3 nos. Raw material for core & coil procured.

  21. THANK YOU FOR YOUR ATTENTION

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