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

LHC low-b triplet – warm assembly 27 avril 2007

Completed cold mass and piping on spider supports 27 avril 2007 3

Q1/Q2, Q2/Q3 interconnections General view Heat exchanger line (L) Cold mass/heat exchanger line (M4) Pumping line 2 (Xbt) Instrumentation line (M2) Q3 Thermal shield return line (FF) Beam line (V) Q2 Main bus bar line (M1) 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.

LHC low-b triplet – DFBX 27 avril 2007

Q1 supports at IP 5L 27 avril 2007 6

Cold Mass Support A ‘fixed’ and ‘free’ spider support Invar rod connecting the two to share support

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 Q1 load 115kN Q3 load 93kN

Review of the inner triplet 24-25 April 2007 Summary C. Hauviller 27 avril 2007

Fix Points D1 Q3 Q2B Q2A Q1 Internal heat exchanger FP Cold Mass-Vacuum Vessel Fixed Point HX-Cold Mass External heat exchanger (HX) D1 Q3 Q2B Q2A Q1 LBX DFBX MQXA MQXB MQXB MQXB MQXA Fixed Point Triplet-Tunnel Floor Tie Rods Linking Vacuum Vessels Jacks (longitudinal) 38490 27 avril 2007 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

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 Q1, Q3 and DFBX. Can be done in-situ 27 avril 2007

Q1 pipe support weldment (Q3 similar) 27 avril 2007 14

Q1 pipe support weldment proposed modification See Q1 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 15

DFBX Piping Layout D1 End Q3 End 27 avril 2007 16

Bus Duct Thrust Support Analysis (weld clamp) Weld Clamp Stress Calculation Details Material: 304L stainless steel Peak thrust load: 20.1 kN (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) Allowable stress: 115 MPa (16.7 ksi) Weld efficiency factor: 0.55 Net allowable stress: 63.3 MPa (9.19 ksi) Weld clamp Weld stress exceeds allowable stress dictated by PV code but is still within material strength limits Thrust support 27 avril 2007

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 the 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 LN2 cold test. Understand the mechanics of the overall support system (component and integrated assembly). Experimental validation recommended. Check the thermo-mechanical transverse stability/reproducibility of the magnets inside the vessels. 27 avril 2007

Meshing of the supports was refined to include three elements through the half-inch thickness of the G11. The G11 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 3e6 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 1e6 psi was used for this direction. Note that while this is technically "orthotropic", it really assumes isotropy in the xy plane.

Repaired spider 27 avril 2007

Requirements for a Fix In Situ Does not move fix point of the assemblies React loads with sufficient stiffness to limit deflection – 150kN design load (slide 4) Acts at any temperature 300K to 2K Focus on implementation in Q1—Q3 solution tuned for length will then accommodate 27 avril 2007 21

Cartouche / Cartridge Affixed at Q1 non-IP end; Q3 IP end Transfer load at all temperatures Limits support deflections 27 avril 2007 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 23

Cartridge Initial Analysis Cartridge looks very promising, and is the proposed solution Worst case Q1 spider support longitudinal deflection < 2mm limit Worst case Q1 spider load < ¼ load that caused failure during recent pressure test Does not move magnet fix point In fact fixes Q1 / Q3 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 Q3 attachment Consolidation of design variants and anlayses 27 avril 2007 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

Tie rod assembly at warm fit-up 27 avril 2007 26

Q1/Q2, Q2/Q3 interconnections Vacuum vessel closure 4.8 mm thick Bellows buckling pressure: 3.7 bars Vacuum longitudinal force: Max 8000daN Buckling force (per rod): 5770daN Is the guide length sufficient to avoid rotation? Buckling force (per rod):1440daN Stiff guidance has probably to be implemented 27 avril 2007 C. Garion

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

External jack stands in warm fit-up 27 avril 2007

Inner Triplets Supports: fixation to the ground Different tunnel ground conditions: Point 1: Two holes of ~400mm diameter to fix the supports to the concrete underneath Point 2 (RB24): platform made of concrete blocks and reinforced concrete slabs to continue the tunnel slope Point 8 (RB86): reinforced concrete beam 27 avril 2007

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

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 Q1, Q3 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 Q1/Q2/Q3 (spiders). Integrity of these parts not guaranteed. Limit the load where possible. Repaired part not acceptable. To be replaced. Fixes in Q1 and Q3 to be finalized and qualified (including transients, accidental loss of insulation vacuum, a LN2 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 32

Sectors 34 & 45 Option A : Wait for IT to cool-down 45 Option B : Mar. Apr. May Jun. Jul. Aug. Oct. Sep. Nov. Dec. Jan. Feb. 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 . 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 Option A : Wait for IT to cool-down 45 Option B : Do not wait IT repairs for cool-down 45 Option C: Do not wait IT repairs for cool-down 45 & minimize QUI interventions 4/24/2018 K. Foraz TS-IC-PL