Status of the low triplets Accident during pressure

Status of the low-β triplets Accident during pressure test on March 27 th Outcome of the review held April 24 -25 th Impact on cool-down of Sector 4 -5 27 avril 2007 S. WEISZ /TS-IC 1

LHC low-b triplet – warm assembly 27 avril 2007 S. WEISZ /TS-IC 2

Completed cold mass and piping on spider supports 27 avril 2007 S. WEISZ /TS-IC 3

Q 1/Q 2, Q 2/Q 3 interconnections General view Heat exchanger line (L) Cold mass/heat exchanger line (M 4) Pumping line 2 (Xbt) Instrumentation line (M 2) Q 3 Thermal shield return line (FF) Beam line (V) Q 2 Main bus bar line (M 1) Beam screen line (K) 4. 5 K heat intercept line (C’) Thermal shield cooling line (EE), filling line (LD) and pumping line (XB) are not visible on this photo. S. WEISZ /TS-IC

LHC low-b triplet – DFBX 27 avril 2007 S. WEISZ /TS-IC 5

Q 1 supports at IP 5 L 27 avril 2007 S. WEISZ /TS-IC 6

Cold Mass Support • A ‘fixed’ and ‘free’ spider support • Invar rod connecting the two to share support S. WEISZ /TS-IC

• Tables are the full load cases IF all lines were pressurized to MAWP • 27 March test the pumping and shield lines were not pressurized, and failure was at 20 bar – Q 1 load 115 k. N – Q 3 load 93 k. N S. WEISZ /TS-IC

S. WEISZ /TS-IC

Review of the inner triplet 24 -25 April 2007 Summary C. Hauviller 27 avril 2007 S. WEISZ /TS-IC 10

Fix Points Internal heat exchanger D 1 LBX FP Cold Mass. Vacuum Vessel Q 3 DFBX Fixed Point Triplet. Tunnel Floor MQXA 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 27 avril 2007 S. WEISZ /TS-IC 11

Inner Triplet Review Main subjects – General – Internal piping and anchoring to cold masses (helium vessels) – Connection of cold masses to vacuum vessels – Forces on vacuum vessels transferred to ground 27 avril 2007 S. WEISZ /TS-IC 12

Inner Triplet 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 27 avril 2007 S. WEISZ /TS-IC 13

Q 1 pipe support weldment (Q 3 similar) 14 27 avril 2007 S. WEISZ /TS-IC 14

Q 1 pipe support weldment proposed modification See Q 1 Pipe Anchor Stress Analysis – T. Page, April 19, 2007 Modified pipe anchor stresses Bracket to cold mass weld stress: 9121 psi (63 MPa) Elbow to end dome weld stress: 9430 psi (65 MPa) As designed pipe anchor stresses Bracket to cold mass weld stress: 41797 psi (288 MPa) Elbow to end dome weld stress: 17383 psi (120 MPa) 27 avril 2007 S. WEISZ /TS-IC 15

DFBX Piping Layout D 1 End Q 3 End 27 avril 2007 C. Hauviller/TS-IC 16

Bus Duct Thrust Support Analysis (weld clamp) Weld Clamp Stress Calculation Details Material: 304 L stainless steel Peak thrust load: 20. 1 k. N (4510 lb) Weld size: 1. 59 mm (1/16”) 2 sides of clamp Weld diameter: 48. 3 mm (1. 90”) Shear stress: 61. 5 MPa (8. 92 ksi) Equivalent stress: 107 MPa (15. 4 ksi) Weld clamp Allowable stress: 115 MPa (16. 7 ksi) Weld efficiency factor: 0. 55 Net allowable stress: 63. 3 MPa (9. 19 ksi) Weld stress exceeds allowable stress dictated by PV code but is still within material strength limits 27 avril 2007 Thrust support C. Hauviller/TS-IC 17

Connection of cold masses to vacuum vessels • Define the worst case loading of the spider, including tie rods contractions, and pre-stress. Validate by testing that the SF on longitudinal load is at least 4. • Validate the cartridge solution fix: – Complete thermo-mechanical analysis including a sensitivity analysis on T profiles, in particular including cool-down/warm-up transients, accidental loss of insulation vacuum – Encourages the components and assembly tests proposals, possibly including a LN 2 cold test. – Understand the mechanics of the overall support system (component and integrated assembly). Experimental validation recommended. • Check thermo-mechanical transverse stability/reproducibility of the magnets inside the vessels. 27 avril 2007 S. WEISZ /TS-IC 18

Meshing of the supports was refined to include three elements through the half-inch thickness of the G 11. The G 11 was treated as orthotropic; in the plane of the support (the xy plane in the analysis) bending is resisted primarily by the tension or compression of the relatively stiff glass fibers; the Young's modulus is dominated by the glass, and was set to 3 e 6 psi in both the x and y directions. For the z-direction (through the thickness), loads are perpendicular to the glass fibers, and the stiffness is influenced more strongly by the epoxy matrix; a reduced modulus of 1 e 6 psi was used for this direction. Note that while this is technically "orthotropic", it really assumes isotropy in the xy plane. S. WEISZ /TS-IC

Repaired spider 27 avril 2007 S. WEISZ /TS-IC 20

Requirements for a Fix • In Situ • Does not move fix point of the assemblies • React loads with sufficient stiffness to limit deflection – 150 k. N design load (slide 4) • Acts at any temperature 300 K to 2 K • Focus on implementation in Q 1—Q 3 solution tuned for length will then accommodate 27 avril 2007 S. WEISZ /TS-IC 21

Cartouche / Cartridge • Affixed at Q 1 non-IP end; Q 3 IP end • Transfer load at all temperatures • Limits support deflections 27 avril 2007 S. WEISZ /TS-IC 22

Pieces…. 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 27 avril 2007 S. WEISZ /TS-IC 23

Cartridge Initial Analysis Cartridge looks very promising, and is the proposed solution • • • Worst case Q 1 spider support longitudinal deflection < 2 mm limit Worst case Q 1 spider load < ¼ load that caused failure during recent pressure test Does not move magnet fix point – In fact fixes Q 1 / Q 3 better than currently • • Magnetic effect negligible Design is ongoing to look at: – – – Length; diameter of rod (not 10% effect in various models) Steady state thermalization BC’s Thermal performance under upset / transient conditions Attachment details to cold mass (corrector containment volume shell) Attachment details to vacuum vessel, including effect on O ring groove due to • Cartridge bracket / tie rod ear deflections • Cooling of the Vacuum Vessel due to additional heat leak – Q 3 attachment – Consolidation of design variants and anlayses 27 avril 2007 S. WEISZ /TS-IC 24

Inner Triplet Review Forces on vacuum vessels transferred to ground Overall approach unclear. Not clearly specified/ understood. Two extreme cases: Case 1: - loads transmitted to the DFBX and then to ground through the tie bars (initial specification) Case 2: -loads transmitted to the ground through the jacks 27 avril 2007 S. WEISZ /TS-IC 25

Tie rod assembly at warm fit-up 27 avril 2007 S. WEISZ /TS-IC 26

Q 1/Q 2, Q 2/Q 3 interconnections Vacuum vessel closure 4. 8 mm thick Bellows buckling pressure: 3. 7 bars Vacuum longitudinal force: Max 8000 da. N Buckling force (per rod): 5770 da. N Is the guide length sufficient to avoid rotation? Buckling force (per rod): 1440 da. N Stiff guidance has probably to be implemented 27 avril 2007 WEISZ /TS-IC C. S. Garion 27

Inner Triplet Review – Forces on vacuum vessels transferred to ground Case 1: - loads transmitted to the DFBX and then to ground through the tie bars Resistance of tie bars and tie bars supports not adequate. Can be modified in-situ. Free the jacks Global (in)stability to be assessed 27 avril 2007 S. WEISZ /TS-IC 28

External jack stands in warm fitup 27 avril 2007 S. WEISZ /TS-IC 29

Inner Triplets Supports: fixation to the ground – Different tunnel ground conditions: Point 1: Two holes of ~400 mm diameter to fix the supports to the concrete underneath Point 2 (RB 24): platform made of concrete blocks and reinforced concrete slabs to continue the tunnel slope Point 8 (RB 86): reinforced concrete beam 27 avril 2007 S. WEISZ /TS-IC 30

Inner Triplet Review – Forces on vacuum vessels transferred to ground Case 2: -loads transmitted to the ground through the jacks Longitudinal forces on jacks limited to 4 tons due to anchoring and local floor conditions 27 avril 2007 S. WEISZ /TS-IC 31

Inner Triplet review Main Recommendations • 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 27 avril 2007 S. WEISZ /TS-IC 32

Sectors 34 & 45 34 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 45 Option A : Wait for IT to cool-down 45 9/10/2020 34 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 45 . Option B : Do not wait IT repairs for cool-down 45 K. Foraz TS-IC-PL. S. WEISZ /TS-IC 34 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 45 Option C: Do not wait IT repairs for cooldown 45 & minimize QUI interventions 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52