Arup K. Ghosh

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WBS 2.4.2 STRAND PROCUREMENT

• Arup K. Ghosh
• BNL

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Outline

• Present status of strand procurement
• Future strand for LARP
• Smaller Filament Deff
• PIT strand
• Tolerance of RRP conductors to cabling
  degradation
• Filament Spacing
• Rolled strand
• Revisit strand specification

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Procurement PlanNov-05
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Nb3Sn Strand SpecificationRRP-54/61
Spec. No. LARP-MAG-M-8001-RevB
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Procurement Status3-30-06
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Strand Purchase and Inventory as of 4-20-06
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RRP 54/61 Piece Length

• 250 kg of wire produced for LARP and CDP in the
  last 12 months, single billet yield is 35kg
• 93 in lengths gt1Km, 57 in lengths gt3 km

• With the following HT 665C/50 hrs
• Average Jc(12T)2880 A/mm2
• Average RRR 189

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Procurement Plan For FY07 3-30-06
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Projected Inventory
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Towards a more flux-jump stable conductor

• Why ?
• Intrinsic (Adiabatic) stability of wire
• Field quality in magnets
• Reduce Effective Filament Diameter Deff
• Deff lt 30 mm (adiabatic limit not established
  experimentally for high Jc wire )
• For Deff gt 35 mm, maintain high RRR after
  reaction ? prevent Sn-leakage
• OST-RRP- 91 and 127 sun-element billet design
• Cabling Effects
• Shearing of sub-elements ?RRR degradation
• SMI-PIT- 288
• 50 mm at 1.25 mm wire
• 32 mm at 0.8 mm wire

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Decreasing the sub-element size

• Pack increasing number of sub-elements into
  Re-stack
• Increasing number of bundles ? packing more
  difficult
• More cold work increases the hardness of non-Sn
  parts
• Additional Cu-Cu surfaces ? worse bonding ? yield
  ?

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91-127-217 series made with Nb-Ta for CDP RD

• High Jc design (3000 A/mm2)
• Objective was to only vary the sub-element size
• same sub element billet for all restacks
• all restacks 53 non-Cu, 0.7 mm strand
• Significant wire breakage for all, 217-stack the
  worst
• For a reaction at 665 C/50hrs
• (Jc, RRR)
• 91-stack 2920, 134
• 127-stack 2720, 110
• 217-stack 2660, 7 (Many broken barriers)
• Suggests there is some size effect controlling
  the maximum Jc

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Future RRP Strand

• Is OST ready to produce 91 and 127 sub-element
  billets ?

Further to our discussions today about 61 ? 127
stack designs for LARP, this year we are
producing 91-stack material for the EFDA dipole.
The sub-element design is for lower Jc and uses
Nb-Ti (Jc 2400 _at_ 12 T), but the work will give
us some yield data on our way to 127 stacks.
Based on CDP RD billet 8079 (90/91) and FNAL
billet 8195 (108/127) both of which uses the
same sub-elements of Nb/Nb-47Ti
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(No Transcript)
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EFDA Dipole Project
E. Salpietro
Strand based on 90/91-stack design using Nb/
Nb-47Ti rods
Due dates Delivery One (30 kg strand) delivered
Delivery Two (120 kg strand) 9 months
Delivery Three (280 kg strand) 15 months
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Future RRP Strand

• Is OST ready to produce 91 and 127 sub-element
  billets ?
• At present the lower Jc ( gt 2000 A/mm2) 91-design
  billet is moving into production ? EFDA Order of
  400 kg
• Under CDP RD this year, a high Jc 108/127
  billet is being processed (Nov-06)
• FNAL has OST fabricating a RD billet using
  120/127 design (Dec-06)

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Powder-in-Tube (NbTa)3Sn (PIT)Shape Metal
Innovation (SMI)
J. Lindenhovious
B179
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PIT -Strand
Luc Oberli (CERN) WAMDO-06

• NED is pushing SMI-VAC to develop strand.
• Latest billet B207 is 288 filament, similar to
  B179
• Strand Diameter 1.25 mm
• Cu/Non-Cu 0.96
• Jc gt 2400 A/mm2 At 12 T

B179
B 207
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SMI 288 filament
Luc Oberli (CERN) WAMDO-06
Jc 2077 A/mm2 at 12 T Jc 1118 A/mm2 at 15
T HT 84 hours at 675 0C Jc non Cu lower than
B179 by 10 - 15 due to powder preparation
which underwent by mistake an additional HT.

• Stability measurements performed by LASA
  Field rate 15 mT/s
• At 1591 A, no quench in the field range 0 - 5
  T

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SMI-PIT B-207
Wire drawn to 0.8 mm Jc(12T) 2145 A/mm2 , Js gt
4500 A/mm2 (Is gt1200A) Filament size 32 mm (No
flux-jump observed in magnetization)
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Cabling Degradation

• Strand Deformation at the cable edges
• Filament Distortion
• Simulate by rolling strands
• E. Barzi (FNAL)
• Filament Merging
• Microscopy, Ic and Is measurements

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Rolled Strands
RRP 54/61
Def28
Def14
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SMI Strand deformation by rolling
Luc Oberli (CERN) WAMDO-06
B 201
B 179
Deformation of 25 , i.e. d0 - t 0.25 mm.
Distribution of Cu within the strand important
in order the strand can sustain heavy
mechanical deformation as in cabling.
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SMI Deformation by rolling on B207
Luc Oberli (CERN) WAMDO-06
Ic Degradation of 15 17 on samples with a
deformation level of 28 RRR value dropped to 80
indicating Sn diffusion in the Cu matrix
Def 28
No HT
Def 28 after 84 h at 675 0C
With HT
2.8 at. Sn
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Re-visit Strand Specification
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Summary

• There is sufficient RRP 54/61 strand for the
  magnets in the near term
• 91-filament is moving into production
• 127 filament can be in production within 12
  months.
• PIT strand with 288 filaments is flux-jump
  stable at 0.8 mm wire diameter with Jc 2100
  A/mm2 at 12 T
• Cabling Degradation from filament shearing
• Optimization of cabling parameters
• Optimization of strand design
• Increase filament spacing ? (FNAL has already
  ordered a 60/61 billet with larger Cu-spacing,
  evaluation in progress)