Conductor R

1
Conductor RD Plan

• Arup K. Ghosh
• BNL

2
Introduction

• The first TQ magnets, TQC01 and TQS01 and SQ-02
  use
• 0.7mm Modified Jelly-Roll strands borrowed from
  FNALs inventory
• 27-strand cable with 1.0 Deg keystone angle
• Strand is of the 54/61 design with large
  effective filament diameter 70-80 mm
• Using Nominal heat treatment ?Jc gt 2000 A/mm2
  but the strand has a low stability current Is
• We now understand that Is in unstable strands is
  strongly influenced by dynamic effects
• Improve thermal environment ??Increase RRR of
  stabilizing copper
• Achieve this by preventing excessive reaction of
  Nb-barrier
• Optimize Reaction Time/Temp to increase the
  stability current to be well above magnet
  operating current

3
Heat-Treat Optimization
Jc(12T-15T)
HT-Temp 635C-695C Time
Strand Stability for large Deff
Higher Bc2 at higher T
RRR
Bc2
4
Ic and Is of virgin and of Strands Extracted
from LARP Proto-type Cables
5
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 (Rod-Restack Process)
• Uses a distributed barrier approach
• Jc (12T) 3000 A/mm2
• Effective Filament Diameter Deff Sub-element
  Diameter
• Deff scales inversely with increasing number of
  Sub-elements

6
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
7
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
• Very limited experience with the 91 or the 127
  stack design. These billets are presently
  considered by OST to be RD billets.
• For FY06 LARP would like to use strands with the
  84/91-stack design
• Why? Why not use the production 54/61 strand ?
• Stability will improve with decreasing
  sub-element diameter
• Question is how to move from RD to production
  at OST

8
Nb3Sn Strand Specification84/91 Design
9
Nb3Sn Strand Specification54/61 Design
10
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
• 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
• At present OST is fabricating strand for CDP that
  is similar to strand being considered for LARP
  purchase

11
CDP-RD Inventory
Compiled with D.R Dietderich
Yield of billet 8502 is 50 due to wire
breakage Billet 8521 is in process, yield not
known
12
Comments

• 30 kg can be fabricated into 5 ULs each 65m
  long. Each UL is for a TQ-coil
• With the exception of billet 8079, all the strand
  in CDP inventory is the high Sn-content capable
  of a Jc of 3000 A/mm2. The most recent billet
  8220 (54/61-design) has this Jc and a RRR 200.
  With this RRR the stability current is
  1000-1100 A.
• Most of the RRP strand at 0.7mm have yet to be
  cabled as a TQ-cable with 1.0 deg keystone. LBL
  has recently made a short (17m) trial piece of
  27-strand TQ cable using strand from 8220. This
  is being evaluated for Ic, Is and RRR.
• A short length 4m of cable has also been
  fabricated using strand from 8079 (90/91-design),
  this too is under evaluation. Strands from this
  billet show stability currents gt 1200A.
• For strands with either the 61, 91 or 127 stack,
  the key parameter that ensures a high stability
  current is the RRR of the copper stabilizer.
• Provided the copper remains clean, strand
  stability increases as the stack number is
  increased i.e. sub-element size is decreased

13
Recent OST Billets
14
Target Program
15
Total Conductor Estimate
Total
Total 936 kg Plan for 1100 kg
16
Procurement Plan
Low Risk
Low-Risk
Higher Risk
17
Procurement Strategy

• CDP has two billets on order which uses the same
  sub-element with the potential for Jc(12T) 3000
  A/mm2
• One uses 54/61 design
• The other 84/91 design
• Delivery 11/31/05
• CDP is also placing an order for 90 kg for high
  Jc wire using the 84/91 design Delivery 3/31/06
• LARP will place an initial order for 95 kg (this
  is the yield from one sub-element extrusion
  billet)
• 54/61 design Delivery 3/31/06

This allows for material to be in the pipeline
that we are certain to have in hand for the
magnets being fabricated in FY06. If the 84/91
billets for CDP are successful then LARP could
swap that with the 54/61 wire delivered under
its order
18
Summary

• Present Status
• Draft specification sent to OST
• Wire from Billet 8502 (84/91) arriving LBL
  10/10/30
• This wire needs to be characterized for Ic, Is
  and RRR
• Cable using billet 8220 (54/61) under
  investigation
• LARP order needs to be placed soon