R Ostojic CERN AT Department The LHC lowb

R. Ostojic CERN, AT Department

The LHC low-b triplet D 1 DFBX Q 3 Q 2 Q 1 TASB LBX DFBX MCSOX MCBXA IR 1 and 5, D 1 is a normal conducting dipole. MQXA MQXB 6. 37 5. 5 MQSX MCBX MQXB MQXA 5. 5 6. 37 MCBX Triplets were designed and built by a collaboration of five laboratories: BNL, CERN, Fermilab, KEK, LBNL. 2

Design and manufacture • Magnets – – MQXA (Q 1, Q 3) MQXB (Q 2) Correctors MBX (D 1) KEK Fermilab CERN BNL • Cryostats – Q 1, Q 2, Q 3 – D 1 • DFBX • Interconnects Design – Q 1 -Q 2, Q 2 -Q 3, Q 3 -DFBX – D 1 -DFBX Execution • Jacks and tunnel installation Fermilab BNL LBNL, Fermilab CERN 3

Design specifications and documents • All design specifications and solutions are documented in the functional and interface specifications. These documents were released following collaboration meetings and independent reviews, and after a formal review procedure in the CERN EDMS. (EDMS documents: LHC-LQX-ES%, LHC-DFBX-ES%, LHC-MBX-ES%). • Acceptance procedures for all magnets and DFBX are defined in appropriate Acceptance Plans, also formally reviewed in CERN EDMS. (EDMS documents: LHC-LQX-TP%, LHC-DFBX-ES-0001, LHC-MBX-ES 0003). • Safety related procedures and documents were reviewed by competent bodies in participating laboratories following the Memoranda of Understanding. (http: //sc-gs. web. cern. ch/sc-gs/gs_ms/TISUS/) 4

Key dates • Design and development 1998 -2002 • Production 2001 -05 • Delivery at CERN 2003 -07 • First triplet assembly at CERN April 2005 • First triplet in tunnel (8 L) Dec 2005 • Triplet in 8 L under vacuum June 2006 • Pressure test of Sector 7 -8 (8 L) Nov 2006 • Repair of HX in all triplets Feb-May 2007 • Pressure test of triplet in 5 L Mar 2007 5

Schematics of the mechanical design Internal heat exchanger D 1 LBX FP Cold Mass. Vacuum Vessel Q 3 DFBX MQXA Fixed Point Triplet. Tunnel Floor Fixed Point HX -Cold Mass Q 2 B Q 2 A MQXB Tie Rods Linking Vacuum Vessels External heat exchanger (HX) Q 1 MQXA Jacks (longitudinal) 38490 For details see dwg. LHCLSX__0001 and LHCLSX__0003. 6

LHC low-b triplet – Q 2 GRP spider External heat exchanger MQXB quadrupoles 7

LHC low-b triplet – Q 1 End domes and cryopiping assembled by Fermilab MQXA quadrupole 8

LHC low-b triplet – warm assembly 9

Failure of HX tube in 8 L 10

Preferred solution: new HX tubes – Manufacture of corrugated tubes in Nexans (DE): – OD/ID 95. 9/82. 3 mm, 1 mm thick wall. – Fermilab supplied OFE C 102 Cu-strips – Bi-metallic transitions designed and assembled by CERN – Tube production completed and all tubes delivered: – Acceptance tests give a buckling pressure of 84 bar. – Assembly of the bi-metallic extremities proceeding in TS/MME. 11

Tests of the 3 -m HX tube Pressure leak tested to 25 bar. Buckling pressure 84 bar. (= buckling pressure at Nexans) 12

Removal and introduction of new tubes in 5 L 13

Pressure test of triplet in 5 L Pressure test failed at 20 bar. Direct cause: Axial movement of Q 1 cold mass towards the IP due to thrust force, which led to the break of the support system (spiders) and rupture of M 1 bellows. 14

Immediate Actions (ICC, 30 Mar 07) – Blank-off DFBX-QRL jumpers to allow pressure test of Sector 4 -5 without the triplet (May 11). – Disassemble the interconnects to allow removal of Q 1. L 5 to surface (to be replaced by spare magnet). Remove other magnets and DFBX to surface for inspection before flushing of Sector 4 -5. – Project Leader called a Review of the mechanical design of the triplets for April 24 -25. – Installation of new heat exchangers in 5 R and Sector 8 -1 to continue as planned. – Investigate possible solutions for reinforcing the fixedpoints of Q 1 and Q 3 and present a proposal at the Review. 15

Requirements for the fix • In situ • Does not move the fixed point of the cold masses • Reacts loads with sufficient stiffness to limit deflection for a design load of 150 k. N • Acts at any temperature 300 K to 2 K • Implementation in Q 1—Q 3 16

Cartouche/Cartridge • Affixed at Q 1 non-IP end; Q 3 IP end • Transfer of load at all temperatures • Limits spider deflections 17

Components Cold Mass Bracket, mechanically and thermally attaches AL cylinder to cold mass volume Vacuum vessel bracket, transfers Invar load to Vacuum Vessel Cartridge, Invar rod centered in Al tube 18

Q 1 Cartridge Modeling • Cartridge applied to Q 1 model including bellows for: – Warm 25 bar pressure test load – Cold, 20 bar quench load Figure 1. Finite Element Model of Q 1 with Cartridge 19

Repairing the fixed points Invar rod and hook 20

Findings of the Review • Internal piping and anchoring to cold masses (helium vessels) – Weak points located in the anchoring to cold masses. To be reinforced on Q 1, Q 3 and DFBX. Can be done in-situ – Too low safety factor for the global stability of the piping. Recommended to add extra supports. Can be done in or near the interconnections • Connection of cold masses to vacuum vessels – Safety factor to ultimate too low for composite parts in Q 1/Q 2/Q 3 (spiders). • Integrity of these parts not guaranteed. Limit the load where possible. • Repaired part not acceptable. To be replaced. – Fixes in Q 1 and Q 3 to be finalized and qualified (including transients, accidental loss of insulation vacuum, a LN 2 cold test): cartouche proposal. Unload the spiders from longitudinal loads. • Forces on vacuum vessels transferred to ground – – Clarify the situation and decide on the option. Reinforce tie bars and tie bars supports. Can be modified in-situ. Study carefully the load sharing Take into account the transverse adjustment requirements for alignment 21

Updated schedule 18 May 19 20 21 1 R 22 June 24 25 23 Q 1 Q 2 Q 1 2 L 2 R 26 Q 3 M 1 M 2 -H 5 R 31 35 September 36 37 38 39 2 L - Transport Q 1 Fixes No access 5 L 30 August 32 33 34 Q 3 Q 1 -Q 2 & DFBX-D 1 electrical 27 July 28 29 Transport Fixes 8 L Fixes and repairs 8 R Q 1 -Q 3 H 1 L Q 1 -Q 3 H Fixes Transport Alignment Interconnection IT pressure test Leak test 22

Summary – Installation of new HX tubes completed in all triplets in the tunnel. – Disassembly of triplet in 5 L completed: all magnets and DFBXE brought to surface. Inspections of the triplet and DFBXE confirm the cause of pressure test failure and the limited extent of damage. – A favoured solution for reinforcing the fixed points (“cartouche”) was presented to the Review of the 24 -25 April. The Review panel endorsed the choice and recommended a few other actions. – The testing of the cartouche is progress. A final test expected by the end of May; repair of triplets in the tunnel foreseen in the period June-August 07. 23