MSC Technical Meeting 29 August 2013

1. MSC Technical Meeting29 August 2013 Overheated splice @ QBBI.A21L6 F. Savary with contributions from N. Dalexandro,H. Prin, C. Scheuerlein, P. Voisin

2. Outline • The facts • Proposed work plan • Intervention workflow • Description of the repair procedure • Description of the consolidation procedure • Schedule • Status of tooling • Conclusion Overheated splice @ QBBI.A21L6

3. The facts • Observations in the tunnel in the end of May 2013 (WISH) • NCR launched on June 10th, 2013, M2 Int.: https://edms.cern.ch/document/1290623 • As observed by LMF-QA the disconnected cable has been severely damaged during installation (5 cut strandson the left side, and possibly signs of overheating on both sides) • The splice is part of a 1.9 K resistance outlier segment Overheated splice @ QBBI.A21L6

4. Measurements @ cold Rmeas=4.75nΩ Rmax=2.25nΩ Courtesy Z. Charifoulline Overheated splice @ QBBI.A21L6

5. Reminder • Subject discussed at the LHC Splices TF Meeting #68, on 30 July 2013 • See ref. EDMS 1304524 Overheated splice @ QBBI.A21L6

6. Intervention workflow NCREDMS 1290623 • Cable inspection: • Visual • Magnetization measurements Extract strands for magnetization measurements Repair / redo the splice according to new procedure Cable ok ? YES • Unsolder M2 Ext., and the spool cables • Cut / remove the bellow (Left) • Cut / remove the flange, and spider clamp (Right) NO In addition to standard QC, carry out radiographic examination • Cut / remove more copper, i.e. additional 60mm (only left side) • Remove insulation as needed • Cut / remove ~ 60mm of copper to check the cable • Possibly, do radiographic examination Cable ok ? • Put in place shunts • Re-weld spool cables • Put in place standard insulation YES NO Replace the magnet(s) Overheated splice @ QBBI.A21L6

7. LS1 Committee, 13th Meeting, 21 June • https://indico.cern.ch/conferenceDisplay.py?confId=257962 Courtesy C. Scheuerlein Overheated splice @ QBBI.A21L6

8. The environment & space limits Overheated splice @ QBBI.A21L6

9. Splice opening & preparation work 45 mm 120 mm 45 mm 50 mm 30 mm 60 mm tbd Overheated splice @ QBBI.A21L6

10. Splice reconstruction 150 mm + 2 x 60 mm (up to 330 mm, in case left side needs to be extended farther) Smooth blending and overlap, avoid 2 mm step and sharp edges Overheated splice @ QBBI.A21L6

11. Cut / remove Cu around the cable Overheated splice @ QBBI.A21L6

12. Cut / remove Cu around the cable Overheated splice @ QBBI.A21L6

13. Reconstruction Overheated splice @ QBBI.A21L6

14. Reminder • Force @ rupture, and resistance of a splice, both @ 4.3 K, as a function of the overlap • Note CERN-ATS-Note-2011-074, EDMS 1159508, by C. Scheuerlein et al. The splice proposed for the overheated cable is in this range Courtesy C. Scheuerlein Overheated splice @ QBBI.A21L6

15. 2009 – QBBI.B29R3 – M3 line Overheated splice @ QBBI.A21L6

16. Consolidation procedure & QC • Carry out ELQC, apply standard checks • R8 standard, and R16 becomes R16+12 • Cu machining, and shunt installation procedures are standard (as this is a quad. line, @ bottom only) • Insulation needs to be rebuilt in the 60 mm extensions of the splice (50% overlap, pre-preg, …), then the standard insulation system can be put in place Overheated splice @ QBBI.A21L6

17. Schedule This week Overheated splice @ QBBI.A21L6

18. Status on tooling • For preparation • Almost finished • Induction loop for unsoldering to be optimized, utilization of tooling recovered from ACCEL (already utilized for the construction of the Q7) • For reconstruction • Soldering molds to be designed and fabricated • For testing • ELQC, ok • Radiographic examination, should be ok [to be checked with Jean-Michel Dalin] Overheated splice @ QBBI.A21L6

19. To understand it better • Understand in what conditions there is overheating • Organize the execution of tests on the surface • Heat up a splice + bb progressively, and check the effect on the copper parts, and insulation (oxidation, color, …) • This will help on deciding what to do in the other cases • Statistics in preparation by Sandrine Overheated splice @ QBBI.A21L6

20. Conclusions • A repair (special splice) is feasible • It allows installing the standard shunts, and the standard insulation system, but not the standard clamp (spider) on the right side • Special tooling is needed for the preparation work (induction), and for the re-soldering (resistive). However, not a major issue • The repair is only possible if the cable is sane in the 60mm on the right side, and in the 60mm or 120 mm on the left side of the original splice • We rely on both top & bottom contacts of the 60 mm splice to get an “almost” standard splice in terms of overlap • If the above conditions are not fulfilled, one (or two) magnet(s) has(have) to be replaced • A special splice is also possible if only one magnet is replaced • The repair procedure allows intervention on any type of IC, QBB, QQB, and QBQ, and on any line (M1, M2, and M3) Overheated splice @ QBBI.A21L6

21. To be checked … • With magnet coordination, what magnet can we put in place, in case the cable is excessively degraded? • How many magnets do we have available in case there would be other cases? • Statistics (# of known cases of overheated cables) will be shown at the SMACC Meeting of next week Overheated splice @ QBBI.A21L6