Conductor and Cable R

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Conductor and Cable RD for LARP
US LHC Accelerator Research Program

bnl fnal lbnl slac
D.R. Dietderich, LBNL LARP Collaboration
Workshop June 17-18, 2004
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Outline of Presentation

• Strand Needs
• Target strand specifications
• RD effort
• Jc, RRR, M, Deff, strand stability
• Cabling Needs
• RD effort to develop reference or baseline
  cables
• Narrow cables for 4 layer cosine 2q quad
• Wide cables for 2 layer cosine 2q quad, (useful
  for cosine q dipole)
• Cable measurements
• Ic of cables
• Effect of stress on Ic
• Strand procurement
• Strand specifications

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Strand Requirements

• Conductor Development Program
• 3,000A/mm2
• 40 micron subelements
• 10,000m piece lengths

Parameter Near Term (1-2 yrs) Long Term
(gt2yrs) Diameter (mm) 0.7-0.8 0.6-1.0 Cu
fraction 0.5 0.4-0.5 Deff (microns) 90-120 4
0-55 Jc (A/mm2) 3,000-2,500 3,000 RRR 20-100
20-100
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OST RRP Wire HT and Test at LBNL

• OST B6555
• HT 650oC, 200hr
• RRR15
• Stable to 58 ?V/m

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Strand Stability
MJR ORe 0021
Field Ramps
Field Ramp
650C/ 112.5h RRR 20
650C/100h RRR 20
Diameter 0.7mm Sub-element 90 microns
Diameter 0.48mm Sub-element 60 microns
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LBNL Stability of Strands
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FNAL Stability of Cables
PIT (1mm)
MJR (0.7mm)
MJR (1mm)
E. Barzi, FNAL ASC-2004
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One approach to reduce Deff split the subelement
30 ?m
Ta split

• Ta rods divide the Nb3Sn
• see 4MR09 on Thursday by Ghosh et al.
• Effectively reduces Deff

P.Parrell ASC-2004

• Excessive Ta work hardening causes wire breaks
  in full-size billets

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Another way to reduce Deff restack more bundles
61 stack
127 stack

• Direct way to reduce Deff
• Challenge to achieve good bonding during cold
  drawing due to increased Cu/Cu surface area
• Experimenting with modified subelement designs
  to counteract finer structure
• Not yet sure of impact on RRR

P.Parrell ASC-2004
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Cable RD Modify Strand Mechanical Behavior

• Present Nb3Sn cabling procedure at LBNL
• (Coils for RD-3b, RD-3c, HD-1)
• Fabricate cable
• Slightly over size
• Anneal at 210oC/6h
• Softens Cu and cable contracts by 0.25 in
  length
• May harden Sn core
• Re-roll to decrease thickness by 25-50 mm.
• Compacts cable making it mechanically stable
• Plan to follow same procedure for LARP
• May try increasing annealing temperature and time

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Tasks and Objectives Cable RD

• Narrow Cables (8mm) FY 2004
• Establish cable parameter space
• Important to 4-layer design
• Extend LBNLs rectangular cable used for sub-size
  coils
• 20 Strands and 0.7mm diameter
• Wide Cables (16mm) FY 2005
• Highly keystoned cables
• Important for 2-layer designs
• Core near thick edge of cable
• Reduces strand deformation improves mechanical
  stability
• Explore the use of Cu-SS core

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Cable Compaction
Problem with Area Compaction
Decouple thickness width
w
t
2 Cables Same compaction
14.4 mm x 1.400 mm 20.16 mm2
0.8 mm strand diameter 40 Strands Area 20.11
mm2 87.57 Compaction
14.0 mm x 1.440 mm 20.16 mm2
0.4mm half a strand diameter
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Cable Parameter Space
No strand deformation at (0,0)
Decreasing Thickness
Increasing Width
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Cables for D-20, RD-3, and HD-1
D-20
RD-3
RD-3 HD-1
Rect. D-20
LBL Cable 523 MJR-TWCA
Key. D-20
Abandoned Keystoned D-20 Cables
NbTi LHC-HGQ
LBL Cable 805R Oxford-ORe
LBL Cable 522 IGC-Int. Tin
Keystoned cables had 20 loss in Ic Plus more
sensitive to stress
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Quantify Cable Deformation

• Area of edge facet

• Large facets deformation too high
• Potential for real time monitoring

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Cable RD Rectangular Cable

• LBNL experience (RD-3, HD-1 and sub-scale
  magnets)
• No damaged strands during cabling (i.e. no
  reduction in Ic)
• Mechanically stable for coil winding
• Little RD required
• Except for new strand types

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Cables for LARP
RD-3 HD-1
Cos Q FNAL
Sub-scale
4-layer LBNL
2 4 layer FNAL
FNAL Cable 891
Potential Area for LARP Cables
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Cable RD Narrow (8mm)

• Fully Keystoned cable
• Sub-scale as reference
• 20 strands, 0.7mm
• Determine cabling limits
• Damage at thin edge
• Should be mechanically stable
• Prototype cable made and ready to be tested

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LARP Narrow Cable

• Cable 898R
• Strand Diameter 0.70 mm
• Width 7.866 mm
• Thickness 1.2788 mm
• Keystone Angle 0.897o

Major Edge
Minor Edge
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Cable RD Wide (16mm)

• Are fully keystoned cables possible?
• Greater risk of damage at thin edge
• Greater risk of being mechanically unstable
• RD Needed
• Partial keystone
• Cored cables
• Place wedge inside cable

Mechanical stability
Damage
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Cable 891 FNAL Design

• Edge facets size is much larger that LBNL
  experience suggests is appropriate
• Even the thicker major edge is highly deformed

891-D Minor Edge
891-D Major edge
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Cables for LARP
RD-3 HD-1
Cos Q FNAL
Sub-scale
4-layer LBNL
2 4 layer FNAL
FNAL Cable 891
Potential Area for LARP Cables
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Cable 891 FNAL Design

• Metallography shows that sub-elements have been
  damaged
• Sheared in some locations.

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Preliminary Critical Current of Extracted Strands
E. Barzi, FNAL
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Critical Current Measurements of Cables

• Sub-scale race track coils
• Develop winding and assembly method for keystoned
  cables
• BNL
• 7T dipole, 25,000A
• 4 layer quad cable
• CERN (FRESCA)
• 10T, 32,000-40,000A
• 2 layer quad cable
• FNAL
• 28,000A superconducting transformer, 1 cable/day,
  self-field
• NHMFL
• 12T split pair solenoid, 20,000A
• 4 layer quad cable

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Sensitivity of Cables to Transverse Stress
MJR recover Ic when unloaded
D-20
11 T
LBL Cable 523 MJR-TWCA
LBL Cable 522 IGC-Int. Tin
HD-1
NHMFL Test 150mm uniform field 122mm load length
Stress Issue?
Less Cu more Nb3Sn in subelement Nb3Sn filaments
sinter together
RRP-Oxford
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Conductor Characterization FY 2005

• Need 50-60kg (500m) of conductor for 2-layer and
  4-layer quad
• 25 kg per billet
• Jc samples from FE, MID, BE 6 samples minimum
• 3 billets requires 18 samples
• Cable tests
• Depends on number of cables
• Extracted strands 3-6 samples per cable
• One cable test minimum
• Current requirement determines which test
  facility is optimum
• Plus low field stability issues

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Cable Priorities and Plans FY2005

• Cable RD
• Deformation limits of existing strand
• Oxford Strand -- Restack Rod Process (RRP)
• RRP 126 sub-element
• RRP 60 sub-elements with 40 Cu
• HER
• Outokumpu If material is supplied
• Internal tin
• SMI and Supercon, Inc.
• Powder in tube (PIT)
• Keystone cables
• Keystone angle (strain limit) Usually a issue at
  thin edge
• Mechanical Instability (winding issue) Issue at
  thick edge
• Both of these issues less of a problem with NbTi

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The End
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D-20 Azimuthal Stress and Magnetic Field in
Coils at 13T Peak
The narrow edge of a keystoned cable is located
at high field and high stress point
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Conductor Inventory
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Inter-Laboratory Critical Current Comparison
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Proposed Responsibilities

• D. R. Dietderich (LBNL) -- Cabling
• E. Barzi (FNAL) -- Strand Characterization
• A. Ghosh (BNL) -- Cable testing (4-layer)
• G. Ambrosio (FNAL) -- Cable testing (2-layer)