1. MSC Technical Meeting 29 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 2013-08-29 Overheated splice @ QBBI.A21L62

3. The facts  Observations in the tunnel in the end of May 2013 (WISH)  NCR launched on June 10 th, 2013, M2 Int.: https://edms.cern.ch/document/1290623 https://edms.cern.ch/document/1290623  As observed by LMF-QA the disconnected cable has been severely damaged during installation (5 cut strands on the left side, and possibly signs of overheating on both sides)  The splice is part of a 1.9 K resistance outlier segment 2013-08-29 Overheated splice @ QBBI.A21L63

4. Measurements @ cold 2013-08-29 Overheated splice @ QBBI.A21L64 R meas =4.75nΩ R max =2.25nΩ Courtesy Z. Charifoulline

5. Reminder  Subject discussed at the LHC Splices TF Meeting #68, on 30 July 2013  See ref. EDMS 1304524 2013-08-29 Overheated splice @ QBBI.A21L65

6. Intervention workflow 2013-08-29 Overheated splice @ QBBI.A21L66 NCR EDMS 1290623 Extract strands for magnetization measurements Unsolder M2 Ext., and the spool cables Cut / remove the bellow (Left) Cut / remove the flange, and spider clamp (Right) Remove insulation as needed Cut / remove ~ 60mm of copper to check the cable Possibly, do radiographic examination Cable inspection: Visual Magnetization measurements Cable ok ? Repair / redo the splice according to new procedure Cut / remove more copper, i.e. additional 60mm (only left side) Put in place shunts Re-weld spool cables Put in place standard insulation YES NO In addition to standard QC, carry out radiographic examination Cable ok ? YES NO Replace the magnet(s)

7. LS1 Committee, 13 th Meeting, 21 June  https://indico.cern.ch/conferenceDisplay.py?confId=257962 https://indico.cern.ch/conferenceDisplay.py?confId=257962 2013-08-29 Overheated splice @ QBBI.A21L67 Courtesy C. Scheuerlein

8. The environment & space limits 2013-08-29 Overheated splice @ QBBI.A21L68

9. 45 mm Splice opening & preparation work 2013-08-29 Overheated splice @ QBBI.A21L69 45 mm 30 mm tbd 120 mm 50 mm 60 mm

10. Splice reconstruction 2013-08-29 Overheated splice @ QBBI.A21L610 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

11. Cut / remove Cu around the cable 2013-08-29 Overheated splice @ QBBI.A21L611

12. Cut / remove Cu around the cable 2013-08-29 Overheated splice @ QBBI.A21L612

13. Reconstruction 2013-08-29 Overheated splice @ QBBI.A21L613

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. 2013-08-29 Overheated splice @ QBBI.A21L614 The splice proposed for the overheated cable is in this range Courtesy C. Scheuerlein

15. 2009 – QBBI.B29R3 – M3 line 2013-08-29 Overheated splice @ QBBI.A21L615

16.  Carry out ELQC, apply standard checks  R 8 standard, and R 16 becomes R 16+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 Consolidation procedure & QC 2013-08-29 Overheated splice @ QBBI.A21L616

17. AugustSeptemberOctober W34W35W36W37W38W39W40W41W42 Procedure to remove Cu / 60mmxxxxx xxx__ Inspection procedure, visual, magnetization measurements … actually nothing to do xxxxx Procedure to make special splice, including tests (elqc, radiographs, cuts & macros) xxxxx Preparation work in the tunnelxxxxx Development of special insulation / spiderxxxxx Inspection in the tunnel, and tests on the surface (magnetization measurements, …) xxxxx Reconstruction of the splice / QC [if cable ok!]xxxxx Welding of a new bellow / M-flange / QCxxx__ Cu machining and shunt installation / QC__xxx US welding of the spool cables / QCxxx__ Insulation / Injection / QC__xxx 2013-08-29 Overheated splice @ QBBI.A21L617 This week Schedule

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] 2013-08-29 Overheated splice @ QBBI.A21L618

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 2013-08-29 Overheated splice @ QBBI.A21L619

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) 2013-08-29 Overheated splice @ QBBI.A21L620

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 2013-08-29 Overheated splice @ QBBI.A21L621