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Summary of LS1 main interconnection splice quality control results

Summary of LS1 main interconnection splice quality control results. S. Heck, C. Scheuerlein, M. Solfaroli, P. Thonet ELQC tests performed by BE-OP team led by M. Solfaroli LabVIEW data acquisition software by O. Andreassen, EN-ICE-MTA. Outline.

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Summary of LS1 main interconnection splice quality control results

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  1. Summary of LS1 main interconnection splice quality control results • S. Heck, C. Scheuerlein, M. Solfaroli, P. Thonet • ELQC tests performed by BE-OP team led by M. Solfaroli • LabVIEW data acquisition software by O. Andreassen, EN-ICE-MTA

  2. Outline • R-8 of splices produced before LS1; comparison between sector 5/6 and 6/7 • Geometrical distortions of splices produced before LS1 • QC of disconnected cables • R-8 of splices produced during LS1 • R-8 after busbar machining • R-top-side of consolidated splices • R-8 of consolidated splices C. Scheuerlein, LSC meeting 21.6.2013

  3. Reasons to repair “before LS1” splices in 5/6 • QC of main interconnection splices produced before LS1 in sector 5/6 has been completed by BE-OP team. • Analysis of splice defects is courtesy of R. Ostojic. • 25% of splices in 5/6 need to be repaired before consolidation (160×M1, 62×M2 and 94×M3 splices to be repaired). • More than half of the splice repairs are required because a flat surface for shunt installation cannot be produced by removing less than a 1.5 mm-thick layer. Most severe splice deformations are at the “Left” side of M1 splices. • About 60 splices need to be repaired to allow the assembly of the insulation box. • About 30 splices need to be repaired in sector 5/6 because of excessive R-8. The R-8 statistics in sector 6/7 are different. C. Scheuerlein, LSC meeting 21.6.2013

  4. Typical geometrical splice defects QBBI.B17R5-M1-Int local height gauge does not fit QQBI.13R5-M3 global gauge does not fit M3 busbar stabiliser nose is too strongly bent to machine a flat surface C. Scheuerlein, LSC meeting 21.6.2013

  5. R-8 predictions from 2009 data • Based on the biased 2009 R-8 data set it has been estimated that roughly 8 % of the before LS1 production splices exhibit R-8 excess resistances >5 µΩ. • Most R-8 outliers are on the so-called “Left” side (Lyra side) of M1 and M3 splices. From S. Heck, C. Scheuerlein, “Statistical analysis of LHC main interconnection splices room temperature resistance (R-8) results” EDMS No 1244158. From “Splices local Quality Control”, First LHC Splice Review, October 18, 2010 http://indico.cern.ch/conferenceDisplay.py?confId=109100 C. Scheuerlein, LSC meeting 21.6.2013

  6. Reasons for splice repairs of LHC installation splices in 2009 • In 2009 non invasive measurements at ambient temperature have been performed in sectors 1/2, 3/4, 4/5, 5/6 and 6/7. • Least high resistance splice segments were found in sector 5/6. Most splice repairs because of too high R-16 were done in sector 6/7. From M. Koratzinos et al., “Measurements of the Resistance of Main Circuit Busbar Segments at the LHC at Warm”, CERN-ATS 2010-200 http://cds.cern.ch/record/1288291/files/CERN-ATS-2010-200.pdf C. Scheuerlein, LSC meeting 21.6.2013

  7. R-16 of M3 splices from LHC installation measured in 2009 in sectors 5/6 and 6/7. C. Scheuerlein, LSC meeting 21.6.2013

  8. Comparison of M1 splices R-8 distribution in sectors 5/6 and 6/7 Sector 6/7 (updated 17.6.2013) 132 M1 R-8 results 18× R-8excess>5 μΩ (14%)R-8max=41.7 μΩ Sector 5/6 (QC completed) 722 M1 R-8 results 9× R-8excess>5 μΩ (1.2 %) R-8max=30.4 μΩ C. Scheuerlein, LSC meeting 21.6.2013

  9. Comparison of M2 splices R-8 distribution in sectors 5/6 and 6/7 Sector 6/7 (updated 17.6.2013) 132 M2 R-8 results 4× R-8excess>5 μΩ (3.0%) R-8max=27.4 μΩ Sector 5/6 (QC completed) 724 M2 R-8 results 5× R-8excess>5 μΩ (0.7%) R-8max=27.7 μΩ C. Scheuerlein, LSC meeting 21.6.2013

  10. Comparison of M3 splices R-8 distribution in sectors 5/6 and 6/7 Sector 6/7 (updated 17.6.2013) 132 M3 R-8 results 6× R-8excess>5 μΩ (4.5%) R-8max=29.2 μΩ Sector 5/6 (QC completed) 764 M3 R-8 results 16× R-8excess>5 μΩ (2.1%) R-8max=34.2 μΩ C. Scheuerlein, LSC meeting 21.6.2013

  11. R-8 of “before LS1” splices summary • In 5/6 in total 2.7% of splices to be redone because of too high R-8. • In 6/7 so far 13% of splices to be redone because of too high R-8 (updated 17.6.2013). • In 6/7 most R-8 outliers are M1 splices and the R-8 excess is usually on the “Left” side. • In three cases R-8 excess is distributed on both sides of the splice. C. Scheuerlein, LSC meeting 21.6.2013

  12. ELQC of disconected cables • One pair of cables has been found severely damaged, presumably during LHC installation (NCR LHC-QN-QBBI.A21L6-M2-Int-cable; EDMS No. 1290623). There are obvious signs of a strong busbar and cable overheating. • It is likely that the cable is insulated inside the busbar over a long length. • The splice QBBI.A21L6-M2-Int is part of a 1.9 K outlier segment (about 2 nΩ excess). All splices of this segment have been opened, and all other cables of this segment are ok. C. Scheuerlein, LSC meeting 21.6.2013

  13. Diagnostics for assessing cable damage • The cable damage caused by overheating can be assessed by magnetisation measurements of strand samples extracted at different positions of the potentially defective cable. • After excessive heating, the reduction of critical current density is accompanied by a degradation of the mechanical properties (the cable becomes brittle). • Excessive heating makes the cable unsolderable. Variation of the Nb-Ti strand magnetization (ΔM) at 4.2 K in magnetic field up to 6 T after heat treatment to different peak temperatures (duration always 5 minutes) (a) and relative flux pinning reduction vs. annealing temperature at different magnetic field (b). Nb-Ti/Cu strand elongation at fracture vs. peak temperature From “Temperature induced degradation of Nb-Ti/Cu composite superconductors”, Journal of Physics: Conference Series 234 (2010) 022031 C. Scheuerlein, LSC meeting 21.6.2013

  14. Magnetisation measurement results (preliminary) • Strand samples have been extracted at the cable extremities and in the cable center. • Magnetisation measurements courtesy of David Richter, TE-MSC-SCD. • First conclusions: Both cables are degraded over the entire length and cannot be reconnected as is. • Least, but still important degradation at the busbar ends. • Repair method is under definition, not yet validated. • Repairs of overheated cables may be particularly difficult at the connection side, and in extreme cases could require replacement of a magnet. Comparison of the variation of magnetic moment in magnetic field up to 5 Tesla of strand samples extracted from QBBI.A21L6-M2-Int cables and reference strands.

  15. How many overheated cables will we find? • It is likely that we will find overheated cables in other 1.9 K outlier segments. From 2nd splice review, 28.11.2011; 1.9 K resistance data courtesy Z. Charifoulline.

  16. QC of splices produced during LS1 • No major problems detected. • R-8 statistics (updated 18.06.2013): M1 Splices • R-8M1-Right=9.58±0.54µΩ (n=126, R-8M1-Right-max=11.2 µΩ, R-8M1-Right-min=8.4 µΩ) • R-8M1-Left=9.61±0.52 µΩ (n=126, R-8M1-Left-max=12.2 µΩ, R-8M1-Left-min=7.9 µΩ) M2 Splices • R-8M2-Right=9.45±0.47µΩ (n=50, R-8M2-Right-max=11.2 µΩ, R-8M2-Right-min=8.2 µΩ) • R-8M2-Left=9.66±0.57 µΩ (n=50, R-8M2-Left-max=12.2 µΩ, R-8M2-Left-min=9.0 µΩ) M3 Splices • R-8M3-Right=5.76±0.25 µΩ (n=69, R-8M3-Right-max=6.5 µΩ, R-8M3-Right-min=4.9 µΩ) • R-8M3-Left=5.84±0.35 µΩ (n=69, R-8M3-Left-max=7.5 µΩ, R-8M3-Left-min=5.1 µΩ) • 2009 production for comparison [i]: • R-8M1,M2= 9.51±0.74 μΩ • R-8M3=5.69±0.30 µΩ [i] S. Heck, C. Scheuerlein, “Statistical analysis of LHC main interconnection splices room temperature resistance (R-8) results”, CERN-ATS-Note-2012-076 TECH

  17. QC of machined splices • No major geometrical problems detected. In few cases R-8 increase indicates a splice degradation due to machining. • ΔR-8 statistics; ΔR-8=R-8 after machining minus R-8 before machining (updated 19.06.2013): • Δ R-8M1-Right=0.18±0.52 µΩ (n=302, Δ R-8 max=1.8 µΩ, Δ R-8 min=-2.0 µΩ) • ΔR-8M1-Left=0.50±0.60 µΩ (n=301, Δ R-8 max=3.3 µΩ, Δ R-8 min=-2.0 µΩ) • Δ R-8M2-Right=0.34±0.63 µΩ (n=298, Δ R-8 max=3.4 µΩ, Δ R-8 min=-2.1 µΩ) • Δ R-8M2-Left=0.24±0.66 µΩ (n=298, Δ R-8 max=2.8 µΩ, Δ R-8 min=-2.1 µΩ) • Δ R-8M3-Right=0.07±0.55 µΩ (n=319, Δ R-8 max=2.0 µΩ, Δ R-8 min=-3.0 µΩ) • Δ R-8M3-Left=0.18±0.53 µΩ (n=319, Δ R-8 max=1.9 µΩ, Δ R-8 min=-1.6 µΩ) . C. Scheuerlein, LSC meeting 21.6.2013

  18. QC of consolidated splices:Example of a real R-top-side outlier From “Splices local Quality Control”, First LHC Splice Review, October 18, 2010 http://indico.cern.ch/conferenceDisplay.py?confId=109100

  19. R-top-side statistics • Shunts are of good quality, seen by visual, geometrical and R-top-side tests. • R-top-side statistics: • Five R-top-side measurements on each shunt-two acceptance criteria: • Single R-top-side values must not exceed 2.2 µΩ. • The average of the 5 values must not exceed Ø R-top-side=1.7 µΩ. • In average, R-top-side M1,M2 values exceed R-top-side M3 by 0.25 µΩ (1.29 µΩ vs. 1.04 µΩ). Ø R-top-side for all shunts controlled before the 10.6.2013 (for M1,M2 n=103, for M3 n=116)

  20. R-top-side individual measurements summary (updated 17.6.2013) • 940 M1 and M2 shunts tested (corresponding with 4700 R-top-side measurements). • In few cases R-top-side slightly exceeded the acceptance threshold value, but no real outlier has been detected so far. • Average R-top-sideM1,M2=1.29±0.20 µΩ. C. Scheuerlein, LSC meeting 21.6.2013

  21. ΔR-8 after consolidation (updated 20.6.2013) • ΔR-8=R-8 after consolidation minus R-8 after machining • ΔR-8M1-Right=-1.05±0.55 µΩ (n=256, ΔR-8M1-Right-max=0.63 µΩ, ΔR-8M1-Right-min=-3.00 µΩ) • ΔR-8M1-Left=-1.47±0.72 µΩ (n=256, ΔR-8M1-Left-max=0.23 µΩ, ΔR-8M1-Left-min=-4.87 µΩ) • ΔR-8M2-Right=-1.28±0.72 µΩ (n=258, ΔR-8M2-Right-max=0.70 µΩ, ΔR-8M2-Right-min=-5.13 µΩ) • ΔR-8M2-Left=-1.15±0.62 µΩ (n=258, ΔR-8M2-Left-max=0.87 µΩ, ΔR-8M2-Left-min=-4.87 µΩ) • ΔR-8M3-Right=-0.75±0.43 µΩ (n=277, ΔR-8M3-Right-max=0.53 µΩ, ΔR-8M3-Right-min=-2.90 µΩ) • ΔR-8M3-Left=-0.93±0.59 µΩ (n=277, ΔR-8M3-Left-max=0.17 µΩ, ΔR-8M3-Left-min=-3.67 µΩ) • The calculated R-8 decrease due to the additional splice cross section (45 mm2 or 90 mm2 over 50 mm length) is -1.35 µΩ and -0.80 µΩ for quadrupole and dipole splices,respectively. C. Scheuerlein, LSC meeting 21.6.2013

  22. R-8 distribution of quadrupole splices before and after consolidation (updated 20.6.2013) C. Scheuerlein, LSC meeting 21.6.2013

  23. R-8 distribution of dipole splices before and after consolidation (updated 20.6.2013 C. Scheuerlein, LSC meeting 21.6.2013

  24. Conclusions • R-8 distribution of “before LS1” splices in sector 5/6 and sector 6/7 differs strongly, as expected from non-invasive resistance tests performed in 2009. • R-8 of LS1 production splices is comparable to that of splices produced in 2009. • In average the R-8 increase after busbar machining is as expected for solid splices. In sector 5/6 only in few cases a relatively strong R-8 increase indicated a splice degradation during busbar machining. To be monitored carefully in sector 6/7, which contains many more R-8 outliers. • After application of shunts average R-8 is reduced as expected, taking into account the additional Cu cross section. No real R-top-side outlier has been detected so far. • Cable defects in 1.9 K resistance outlier segments may require some complicated repairs, and in the worst case could require a magnet replacement. Splices of these outlier segments should be opened and controlled as soon as possible.

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