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Conductor R&D Plan

Conductor R&D Plan. Arup K. Ghosh BNL. Introduction. The first TQ magnets, TQC01 and TQS01 and SQ-02 use 0.7mm M odified J elly- R oll strands “borrowed” from FNAL’s inventory 27-strand cable with 1.0 Deg keystone angle

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Conductor R&D Plan

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  1. Conductor R&D 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 FNAL’s 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 > 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 8079 90/91 Billet 7904 126/127

  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 R&D 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 R&D 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 OST’s high-Jc strand R&D. • 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-R&D 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 UL’s 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 > 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

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