2'4'1 Materials Conductor Support Arup K' Ghosh

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2.4.1 Materials Conductor Support Arup K.
Ghosh
Introduction Strand Stability Strand Procurement
Plan Strand RD Cable RD Summary
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Main Task

• Strand Specifications and Procurement
• Strand Characterization and Selection
• Cable Fabrication and Testing

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Strand Stability
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Introduction

• Magnets for LARP are designed to use high Jc (gt
  2000 A/mm2 at 12T) Nb3Sn wires. Although
  considerable work by US industry has been done in
  developing such strands under both the SBIR
  (Small Business Innovative Research) and DOEs
  Conductor Development Program (CDP), we have as
  of today only one reliable US vendor that is able
  to deliver sufficient quantity of high Jc wires,
  namely Oxford Superconducting Technology (OST).
• All high Jc conductors that have been
  manufactured by the internal-Sn have large
  effective filament size, Deff. This Deff is
  typically the same as the geometric size of the
  filament bundle within the diffusion barrier. As
  a consequence all high Jc strands are
  intrinsically unstable at low field to
  flux-jumps. This property of the wire will
  persist till Deff is reduced below 30 mm for
  high Jc strands.

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Effective Filament Diameter
Copper
Nb-Barrier
Deff
Tin Core

• Increasing of sub-elements ? Decreases Deff

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Flux-Jump Instability

• Flux-motion within the superconductor generates
  heat
• Jc decreases with increasing temperature (dJc/dT
  lt 0)

• M Jc d

• Adiabatic Stability
• Wilson, Superconducting Magnets

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Stability Current Is
RRP - 0.7 mm d 70 µm Jc(12T) 2700 A/mm2
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But Reactions to get high Jc allow tin to react
through the Nb-barrier and poison copperCopper
RRR lt 7 for as little as 0.1 Sn
Dynamic Stability

• Wires with large filaments exhibit flux-jumps
• Measurements show that RRR (Residual Resistance
  Ratio) of the copper stabilizer influences Is
• Dynamic stabilization can increase Is

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Heat-Treat Optimization
Jc(12T-15T)
HT-Temp 635C-695C Time
Strand Stability for large Deff
Higher Bc2 at higher T
RRR
Bc2
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Example of HT Optimization

• Study of 0.7mm Modified Jelly-Roll (MJR) round
  and extracted strands from TQ cable
• By changing Reaction from 675C/72H to 635C/48H
• Jc(12T) decreased 8
• Increased RRR from 10 to gt 200
• Increased Stability Threshold Current, Is
• From 500 A to gt1200 A

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Strand in TQ-01 series cable
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Is for MJR wire as a function of RRR
Open symbols for extracted strand
635 C
650 C
665 C
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Conductor Procurement Plan
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Target Program
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Total Conductor Estimate
Total 1013 kg Plan for 1100 kg
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Commercial sources of high Jc Nb3Sn

• With the exception of ShapeMetal Innovation,
  Netherlands, (SMI), which uses Powder-in-tube
  technology (PIT) and has delivered strand to
  FNAL in the past, there is only one reliable
  source of high-Jc strand in the US.
• Oxford Superconducting Technology (OST)
• MJR Conductor has been phased out
• Present technique is RRP (Re-stack Rod Process)
• Uses a distributed barrier approach
• Jc (12T) 3000 A/mm2 , Jc(15T) 1600 A/mm2
• Effective Filament Diameter Deff Sub-element
  Diameter
• Deff scales inversely with increasing number of
  Sub-elements

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RRP strand

• Long-lead item 6-9 months after placing order
• SC vendor planning 12-13 months
• Under the direction of the Conductor Development
  Program, OST has developed strands with
  increasing number of sub-elements to reduce Deff

Billet 7054 54/61
Billet 7904 126/127
Billet 8079 90/91
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RRP Strand for LARP

• OST has the most experience in fabricating
  strands of 54/61-stack design. This is considered
  a production wire used in the NMR business
• Reproducible Jc
• long length (good sub-element bonding, better
  understanding of processing)
• RRRgt150 (better processing)
• OST has very limited experience with the 91 or
  the 127 stack design. These strands are presently
  considered by OST to be RD.
• Based on the present status of the 91 or 127
  design, for FY06, LARP will use strands with the
  54/61-stack design

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OST-RRP 61-Stack wire 2 year Development
Courtesy J. Parrell (OST)
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Ic, Jc, Is and RRR - RRP-8220 (54/61)Strand
Extracted strands from a 17m trial piece of TQ-
cable
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Jc and RRR as a function of reaction temp
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Stability Current of 54/61 strand
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Conductor Plan

• The first TQ magnets, TQC01 and TQS01 and SQ-02
  use
• 0.7mm MJR strands borrowed from FNAL inventory
• 27-strand cable with 1.0 Deg keystone angle
• Strand is of the 54/61 design with large
  effective filament diameter 70 mm
• For FY06, LARP will buy 300 kg of RRP 54/61
  strand
• Magnets SR-01, LR01, TQC02, TQC03, TQS03 will use
  cable made from this strand
• Strands with higher sub-element stack (84/91 and
  108/127) will be developed under CDP

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Conductor Development Program

• CDP has been the main driver in OSTs high-Jc
  strand RD.
• It continues to fund this development in FY06
• Main Goals ?reduce Deff, billet scale-up,
  (NbTi)3Sn Ternary
• CDP has been instrumental in getting LARP started
• LARP can take advantage of the strand that is in
  the CDP inventory to conduct strand
  characterization for use in TQ-type cable
• LARP can also borrow from the CDP inventory

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CDP Inventory
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Procurement Strategy

• CDP has two 54/61 billets on order which uses the
  same sub-element with the potential for Jc(12T)
  3000 A/mm2
• Delivery 11/31/05
• CDP has also placed an order for 90 kg for high
  Jc wire
• 60 kg of 54/61 and 30kg of 84/91 design
• Delivery 3/31/06
• CDP also plans to order (delivery 7/30/06)
• 35 kg of 84/91 and 35 kg of 108/127
• LARP will place an initial order for 95 kg (this
  is the yield from one sub-element extrusion
  billet), followed by two orders of 60 kg each

This allows for material to be in the pipeline
that we are certain to have in hand for the
magnets being fabricated in FY06.
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54/61 Strand Procurement
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54/61 Inventory/Month
TQC03 TQS03
TQC02
LR01
SR01
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Nb3Sn Strand Specification54/61 Design
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Strand Contingency

• Although the planning shows that strand inventory
  is maintained above 100 kg, additional strand can
  be made available should there be excessive
  losses during magnet fabrication
• Requesting FNAL to transfer the 85 kg
  replacement purchase for LARP use. This has
  been accepted by FNAL management.
• Requesting OST to divert sub-elements to
  fabricate an additional billet with the 54/61
  design. That is possible as they have material in
  the pipeline which is available for 60/61 wire
  production for other customers.

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Procurement Plan
Low-Risk
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Strand RD
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Strand RD

• Managed by E. Barzi (FNAL)
• Strand Testing
• Ic, Jc Measurements at 4.2K and 1.9 K
• RRR of Copper stabilizer
• Magnetization
• Effective Filament Size Deff
• Stability Measurements
• Stability Current Is

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Strand RD -Main Objectives

• In the near term
• Predict the performance of TQ magnets
• Evaluate the effect of cabling
• measuring strands extracted from the cables
• Heat treatment optimization
• Ic , RRR and Js
• Define strand specs for procurement
• Standardize test procedure (Round Robin Tests)
• Long-term
• Activities closely tied to strand development and
  cabling RD
• Strand stability
• Effect of cabling on Ic degradation
• Transverse stress effects in strands and cables

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Strand Test Facility Resources

• FOR STRAND Ic TESTS
• (MAX FIELD 4.2K/1.9K ,POWER SUPPLY MAX CURRENT)
• FNAL 15/17 T, 1800 A 14/16 T (large bore),
  1000 A
• LBNL 15 T, 2000 A
• BNL 11.5/12 T, 1500 A
• FNAL Balanced coil magnetometer for
  magnetization (15 T max)
• Probe for Ic tests under transverse pressure,
  15 tons max
• BNL Squid magnetometer for magnetization (5 T
  max)

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Comparison of test procedures
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Standardization of Test Procedures

• Round Robin Test
• Effect Of Bonding Agent Stycast
• Ti-Al-V vs. Stainless Steel Reaction Barrel
• Effect of reaction atmosphere vacuum vs. argon
  atmos.

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Round Robin BNL-FNAL
2 samples measured at FNAL and two at BNL. All
samples reacted at BNL.
At 12T
Ic at 12 T is within 3, at 8T it is lt 1
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Cable RD
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Cable RD

• Managed by D. Dietderich (LBNL)
• Primary task is Cable Manufacture for LARP
  magnets
• Optimize cabling parameters to minimize
  distortion of strand internal structure
• reduce critical current degradation at the edge

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TQ cable 28 strands vs. 27 strands
27-strand
28-strand
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Cable RD Main Objectives

• The overall mission of cable RD is to determine
  the cable parameter space (keystone angle, width,
  and thickness) for different strands.
• As a first task determined final parameters of
  the cable (using MJR strand) for the first series
  of TQ quad magnets
• Evaluation of Prototype TQ cable using RRP 54/61
  strands
• Other RD Effort
• Prototype TQ cable- RRP strand 84/91 and 108/127
  strand
• TQ Fully Keystoned Narrow cable (Q1)
• Very Wide Keystoned cable (Q2) 15mm
• Fully Keystoned w/core
• Partial Keystoned w/o core

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Cabling Procedure

• Present Nb3Sn cabling procedure at LBNL
• Fabricate cable
• Slightly over size
• Anneal at 200C/2-4 hrs
• 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

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Cabling Machines

• 60-strand cabling machine at LBNL
• Versatile machine for cable development.
• Sufficient to meet the conductor needs of the
  LARP magnets
• 42-strand cabling machine at FNAL
• Upgraded (summer of 05) from 28 to 42-strand
  (FNAL Core Program)
• Being commissioned for making LARP and other
  cables

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Cable Testing

• FNAL
• 28 kA SC transformer with fast (200kHz, 8-channel
  DAQ) for tests at self-field (1.8T)
• Small racetrack coils for test at field
• BNL
• Cable test facility, 7 T, 25 kA
• Possible upgrade using 12T, 40mm bore Common Coil
  Magnet under construction . This activity under
  BNLs Core Program
• LBNL
• Sub-scale racetrack coils for test at field

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SC Transformer Test
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Transformer Test SQ-02 Witness Cable
SQ-02 Iop
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Example of Cable Test at BNL
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Cabling for FY06
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Cabling for FY06
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Summary

• The Magnet Program relies on a stable,
  reproducible conductor with sufficient Jc that
  industry can deliver in a timely manner
• Hence the choice of 54/61 OST strand
• RRP 54/61 strand from OST will be used for the
  TQ and LR magnets in FY06.
• Data for recent strand shows that Strand
  Stability will not limit magnet performance.
• LARP and CDP will support development of strands
  with improved properties for use in later
  magnets.
• Monitor closely, development of conductor under
  US SBIR and also the NED program in Europe.
• Except for high field cable test, this task has
  the necessary infrastructure and man-power to
  support the main objectives.