Nb 3 Sn Cable and Insulation for LARP High-Gradient Quadrupole Magnets

1. US LHC Accelerator Research Program bnl - fnal- lbnl - slac Nb3Sn Cable and Insulation for LARP High-Gradient Quadrupole Magnets D.R. Dietderich Lawrence Berkeley National Laboratory

2. Outline of the Presentation • Cabling Philosophy for Rutherford Cables • 1 Pass and 2 Pass cables • Cored cables • R&D to reduce HQ cable dimensions • With wire diameters of 0.778 mm and 0.800 mm • Insulation development LARP TQ cable D.R. Dietderich Hi Lumi/LARP CM17 CERN

3. 2 pass process was developed to reduce dimensional changes of a cable during coil processing and reaction A cable is fabricated oversize in thickness, annealed (200C for 2-4 hrs), and re-rolling to final thickness. The anneal reduces the residual stress in the cable and the cable typically shortens by 0.20 – 0.25%. Very important -- Cable is permitted to get wider during the second pass – 2nd pass roll are~ 50-100 microns wider If a cable is too narrow -- Strain localized to 3 strands at the edge of a cable due to friction between rolls and strand LARP Cable Fabrication – 2 Pass D.R. Dietderich Hi Lumi/LARP CM17 CERN

4. LARP Cable Fabrication – 1 Pass • 1 pass process has been developed for adding stainless steel (SS) cores to cables • Strand is annealed (190C for 4 hrs) prior to cabling • Cable is made in 1 pass to final dimensions • Due to mechanical differences between the strand and the SS core a 2 pass process is not possible. • However, other core materials such as S-glass tape or MgO paper tape could be made in 2-pass. Un-reacted Reacted wire Ductility check D.R. Dietderich Hi Lumi/LARP CM17 CERN

5. 2 Pass Cable with MgO Paper & S-glass Cores D.R. Dietderich Hi Lumi/LARP CM17 CERN

6. Cored Cables (HQ-1012) Used in HQ Coil 12 Mandrel with slot for adding a core • HQ cable 1012 (old cable parameters) • 35 strands with diameter of 0.80 mm • 1.44 mm mid-thickness, • Did not increase mid-thickness with of core addition • 15.1 mm wide • 0.75 deg. Keystone angle • 8 mm wide, 0.025 mm thick stainless steel core • Biased to thick edge of cable • Core biased toward thick edge of the cable • No fabrication issue with the addition of a SS core • Addition of the core did not degrade the Ic • Measurements show a reduction of 3-5 % which is typical for an HQ cable without a core D.R. Dietderich Hi Lumi/LARP CM17 CERN

7. Objective of Cable R&D • To permit the use of existing HQ tooling • The cable dimensions needed to be reduced to: • Provide more space azimuthally (i.e. thinner cable) • Provide more radial space (i.e. narrower cable) • Cable R&D targets dimensions: • Reduce HQ cable thickness by 65-100 microns • To 1.375 mm - 1.340mm • Width target is < 15mm (14.7mm -15mm) • Accommodates dimensional changes of cable during reaction • Thicker insulation or more insulation between layers and tooling • Keystone angle un-changed at 0.75 deg. D.R. Dietderich Hi Lumi/LARP CM17 CERN

8. HQ Cable R&D to Reduce Cable Size • The next slide shows the thickness and width of several cable samples • Cable 1014 • 34 strands with a diameter of 0.80 mm • Cable 1015 • 35 strands with a diameter of 0.778 mm • “Blue Box” denotes the target parameters needed to accommodate the cable dimensional changes in the present tooling. • The box with dashed lines are the parameters deduced from R&D on TQ and LQ coils • “Red Circle” denotes the new HQ parameters with the 0.778 mm diameter strand D.R. Dietderich Hi Lumi/LARP CM17 CERN

9. TQ LQ HQ Cable Parameters of R&D Cables Old HQ cable HQ Box New HQ cable Zone with Too much damage D.R. Dietderich Hi Lumi/LARP CM17 CERN

10. Critical Current Cable 1014 with 34 strands and wire diameter 0.80 mm Un-deformed Round Wire Extracted Strands • Gosh (BNL) • A. Godeke (LBNL) D.R. Dietderich Hi Lumi/LARP CM17 CERN

11. RRR 1014 – 0.80 mm wire Un-deformed Round Wire D.R. Dietderich Hi Lumi/LARP CM17 CERN

12. Critical Current Cable 1015 & 1017 with 35 strands and wire diameter 0.778 mm 36 strands Un-deformed Round Wire 1st Production cable 1017 Extracted strands Un-deformed round wire 665C for 48h 650C for 72h D.R. Dietderich Hi Lumi/LARP CM17 CERN

13. RRR 1015 – 0.778 mm wire D.R. Dietderich Hi Lumi/LARP CM17 CERN

14. Cable 1015 Sections I & L • No significant sub-element damage is observed in the wire cross-sectional images 1015-L 1015-I D.R. Dietderich Hi Lumi/LARP CM17 CERN

15. Cable -- Summary • A stainless steel core can be added to the standard HQ cable without significant loss of critical current • Standard HQ cable with 0.80 mm diameter wire could have be decreased in thickness and width to meet the target parameters (HQ box) • However, the risk of damaging to the strand was considered to great with addition of a corfe – i.e. reduced processing margin. • New HQ cable uses a 0.778 mm diameter strand to achieve the new cable parameter • The critical current variation in cable 1015 is not understood but could be due to: • Sample handling while preparing for Jc testing. • Or localized damage in some strands during cabling. • Suggests that a cable testing facility is needed for accurate cable critical current measurements. • RRR was reduced slightly by cabling D.R. Dietderich Hi Lumi/LARP CM17 CERN

16. Insulation Braided onto Cables New England Wire S-glass with 636 sizing TQ/LQ Cable 10 mm wide Braid angle 64 deg. New England Wire S-glass with 933 sizing HQ Cable 15 mm wide Braid angle 55, 60, 64 deg. Pitch Angle Thickness 55o 0.103 mm 60o 0.109 mm 64o 0.114 mm A. Ghosh - BNL D.R. Dietderich Hi Lumi/LARP CM17 CERN

17. Tape Winding • LBNL having vendor fabricate tape winding machine • Demo video • FNAL has an established process with E-glass • 2 layers • Thickness ~0.100mm D.R. Dietderich Hi Lumi/LARP CM17 CERN

18. Summary – Insulation Options • Braided insulation onto cable – Primary option • New England Wire • S2-glass with 636 and 933 sizing – Requires cleaning of insulated cable • thickness of 0.103-0.114 mm • Plan to develop process for fibers with Silane sizing • Revolution Composites • S2-glass – Also makes sleeve • New company but with staff from EDO Fiber Innovations • Tape options – Second option • E-glass 2 layers can produce 0.100 mm • Contains boron – could be an issue. • S2-glass tape • Two layers of tape is > 0.100mm (0.125-0.150 mm) • Consider making braided insulation thicker to match • Consider single layer of tape 0.100 mm thick D.R. Dietderich Hi Lumi/LARP CM17 CERN

19. Extra slides

20. R&D to Reduce HQ Cable Dimensions • New cable parameters: • Mid-thickness 1.375 mm from 1.44 mm • Width 14.80 mm from 15.10 mm • Keystone angle 0.75 deg. Unchanged • New cable designs will provide more space in tool for cable dimensional changes • Have made the first production cable 1017 with new parameters • HQ coil 14 has been fabricated and is ready to test in a mirror. • Have just made a cored cable with the new cable parameters with a strand diameter of 0.778mm. • Coil winding with the cored cable was OK • However, popped strands were produced going around the pole • They are pushed back into position and winding continues • Planning to cut HQ coil 12 into sections for inspection. D.R. Dietderich Hi Lumi/LARP CM17 CERN

21. 1 Pass Cable with Stainless Steel Core D.R. Dietderich Hi Lumi/LARP CM17 CERN