From 3.5 TeV to 7 TeV: Solution for the interconnect consolidation Francesco Bertinelli CERN – Technology Department – M

1. CERN Machine Advisory Committee 2nd Meeting – 26 April, 2010 From 3.5 TeV to 7 TeV: Solution for the interconnect consolidation Francesco Bertinelli CERN – Technology Department – MSC Group • Who is studying the solution and how? • What does the new design look like? • How will it be implemented? 20 minutes presentation, 10 minutes discussion: 26 slides

2. Splices Task Force • Mandate November 2009 (35th LMC, 4 Nov. 2009) • To review the status of all superconducting splices in the LHC machine and prepare the necessary consolidation actions for 7 TeV operation. • Time frame: • 6-8 months starting November 2009. Originally to prepare for a shutdown 2010-2011: plans for the main IC splices maintained after Chamonix2010 (→ shutdown 2012). • Participation: 12 members from different CERN groups and departments. P. Limon (Tevatron), K.-H. Mess (Hera), RHIC this week • www.cern.ch/splices F. Bertinelli, N. Catalan Lasheras, P. Fessia, C. Garion, S. Mathot, A. Perin, C. Scheuerlein, S. Sgobba, H. ten Kate, J.-P. Tock, A. Verweij, G. Willering 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

3. Reminder from Chamonix2010 from A. Verweij • by considering unbiased data, ~15% splices would need redoing from R16 ( = copper stabiliser continuity) alone; • but segment measurements cannot identify them precisely enough (for MQ in particular), plus need to open all M sleeves for a given segment, estimate ~90% of sleeves; • if in addition we consider repairs from visual and preference towards systematically adding a shunt/clamp, we conclude: • Open all W interconnects and cut open all M sleeves, make local R16 measurement, redo ~20% splices, add shunt to 100% splices 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

4. The consolidated main IC splice Mechanical clamping (not present in Tevatron and Hera …) For latest update see Splices Task Force meeting no.17: https://espace.cern.ch/lhcsplices/Meeting%2017/default.aspx Sn-Pb solder for shunt but same Sn-Ag solder where we redo splices Insulation and transversal restraint: injection molding in RYTON(PPS) 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

5. Rationale behind the design i/ii • “Flexible” shunts • e.g. Braids or lamellar construction (EMS-DE) • Should adapt to existing defects • Avoid in-situ machining and copper swarf • Stress-free (or as low as possible) Sn-Pb interface: limit risk of potential degradation • Designed for 13 kA. Critical parameters are thickness and unsoldered length (→ difficult to achieve flexibility with 10 mm ...) • Solder 60Sn-40Pb • Lower melting point than Sn-Ag • “classic” solution (Tevatron, Hera) • ... but additional safety requirements: Safety Commission already involved 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

6. Rationale behind the design ii/ii • Mechanical clamp • Shall not depend on solder strength • Designed to survive ramp-down time • Insulation • Combines electrical function and mechanical restraint to bending • Allows efficient cooling from LHe • Ease of assembly • Current question: Include additional insulation? • nQPS • Build-in monitoring of segment resistances in time • Dedicated resistance measurement campaigns scheduled in Operations • General approach: seek redundancy and safety, do not want to intervene again (but no paranoia ...) 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

7. 13 kA IC: 3 directions for development • ~500 splices redone in 2008-09 • Improved process and QC • Further improvements: • loss of solder • avoid cutting spools • Process speed 13 kA interconnect re-development • Shunt geometry • Solder options • Soldering process • Inductive (as for splice) • Resistive oven (“classic”) • “Fast” resistive • Mechanical clamp 13 kA coordination P. Fessia Shunt development • FEA computations • Materials, availability, costs • Design insulation test Insulation development 16 March, 2010 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

8. 13 kA splice and process improvements • Simplify mechanics for easier use • verify the minimum force to get a good joint (samples at 3 level of force 50%, 25%, 15%) → avoid cutting spools • Include external water cooling after soldering → faster process • Optimise temperature profile • Thermocouples • Optimise geometry of inductive coils 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

9. Precise measurement of temperature profile • Eight measurement points located on the upper surface of the bus-bar. • Temperature sensors: Thermocouples type K with Inconel sleeve. • Tester: Data logger by ATP Messtechnik (Sampling Time = 10s). • Standard inductive soldering procedure. • Kapton stripes around the interconnection to avoid Sn flow off. 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

10. Optimisation of temperature profile • A simplified 3D magneto-static model of the inductor and of the bus-bar has been done. • The aim of the model is to understand the relationship between the field and temperature profiles along the interconnection, during the soldering plateau. 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

11. Shunt soldering process • Resistive oven • “Fast” resistive process • Inductive soldering (possibly several shunts in parallel) Note: 550 N required 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

12. Other alloys that we will study • Baseline is 60Sn-40Pb, will be fully developed first • Other studies will be performed later, same temperature as 60Sn-40Pb • Verification of theoretical mechanical properties still to be checked 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

13. Insulation studies Max displacement reduced from 0.25 mm to 0.06 mm and displaced out of the connection and far from the shunt 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

14. 13 kA IC Quality Control Shunt contact resistance • Progressing in parallel to IC work • First tests of electrical resistance at warm • Launching feasibility studies with EMPA (CH) and BAM (DE) Ultrasonics test 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

15. FRESCA results and “proof of principle” test See L. Bottura 27 April • Quadrupole busbar, constant current • 2 shunted defects measured (3 mm thick, 6 – 10 mm non-soldered length) Shunted No shunt • Shunts show a large improvement of stability • However, results are not directly applicable to the LHC machine situation: → simulation work 15 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

16. Final Validation Test • In SM18 two special SSS cold masses in series (MQM for Q8 and Q9) • the M1 and M3 busbars are not connected to the magnet, hence no inductance during splice testing • in preparation for July 2010 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

17. Review • Formal reviews will be organised: • for the main IC splice design and process • two stages: before Validation Test and end 2010 • Composition? 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

18. Scenario for implementation • Series experience = real data • Average 30 IC activities per week • Capacity designed for 40 IC activities per week • Plan 2012 intervention to 50 IC activities per week (ambitious goal) • repair ≠ new • once work starts there will be huge pressure, many intervenants, little possibility for adaptations → do not count on learning curve • So many aleas at this stage → resist temptation to “squeeze” planning too much already now • Organise work as a train • Proceed to adjacent sector (→ do not jump), extend over 2-3 sectors • keep General Access mode as long as possible (→ cooldown and power as late as possible) • there will be additional work and surely unexpected work (→ Special Interventions Team) See K. Foraz 27 April 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

19. Series experience: soldering busbars 90% work in 11 wks … … but last 10% work in 9 wks from P. Fessia 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

20. Length of shutdown: estimate @50 IC/week The next sector ends 5 weeks later and so on ... 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

21. Resources for splices consolidation • Need to maintain a balance between “existing/experienced” resources and “newcomers” 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

22. Cost estimate of splices consolidation • 21.4 MCHF plus preparation in 2010-11 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

23. Additional magnets/splices work • a considerable amount of non-standard work !!! 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

24. Shutdown and resources issues • Moving magnets at Point 3 for collimators? • Same resources involved → there will be an inevitable time impact in the 2012 shutdown • Surface preparation work (busbar area setup and work, ….) • New Collaboration Agreement for Project Associates • we will first use all available resources on site, … • … but some resources will need to continue other critical activities • looking to set up a new Collaboration Agreement (“a la” Krakow Institutes for series production) • otherwise FSUs • and integrate first persons with existing resources already in 2010 • Xmas 2010 “Technical Stop”: • Could we consolidate 1 sector? → power and test the consolidated solution (and magnets), learning could allow optimization of 2012 shutdown • … or (not“and”) some of the “additional magnets/splices work” • If so needs to be decided by June 2010 (advice?) 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

25. Analysis of circuits • 13 kA: inside DFBAs in particular • 6 kA analysis started: • inventory of splices present: Points 2 and 4 done • Study failure mechanisms (multiple failures), quench detection, energy extraction → risk analysis • Slow progress (resources taken on LHC startup) Praying hands too! 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli

26. Conclusions • 13 kA IC:  we have a candidate design, first test evidence is promising, Final Validation results by August • Scenario for 2012 Shutdown for 13 kA IC exists • Highlighted issues and current questions where adviceis welcome 2nd MAC – From 3.5 TeV to 7 TeV- Francesco Bertinelli