Conductor Requirements for Magnet Designers DOE Conductor Development

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Conductor Requirements for Magnet Designers DOE- Conductor Development Program Daniel R. Dietderich Superconducting Magnet

Conductor Requirements for Magnet Designers DOE- Conductor Development Program Daniel R. Dietderich Superconducting Magnet Program ICFA Mini Workshop on High Field Magnets for Future pp Colliders Shanghai Jiao Tong University, Xuhui Campus June 14 -17, 2015 Office of Science

A focused set of Grand Challenge questions addressing the P 5/HEPAP subpanel report concerns

A focused set of Grand Challenge questions addressing the P 5/HEPAP subpanel report concerns have been identified • Achieve a field of 16 T in a bore of at least 50 mm by focusing on simple, manufacturable designs Dr. X. Wang will address technology development in next talk • Understand training of Nb 3 Sn magnets and develop ways to reduce or eliminate it • Produce an HTS (Bi-2212/YBCO) insert with a self-field of > 4 T and measure the field quality • Reduce cost and improve performance of Nb 3 Sn • Increase the current density by 30% with a scalable sub-element structure • Aim for a cost per kg the same as Nb. Ti • Develop HTS conductor • Reduce silver (i. e. increase Bi-2212 content) or replace silver • Increase Jc/Je • Focus on magnets as technology drivers to generate larger market for cost reduction (Stewardship activity) as a collateral benefit to the program. ATAP SMP is uniquely qualified to address these challenges. June 15, 2015 2 D. R. Dietderich, LBNL

Conductor for Hi-Lumi LHC ITER strand: Non-Cu Jc 800 A/mm 2 (12 T, 4.

Conductor for Hi-Lumi LHC ITER strand: Non-Cu Jc 800 A/mm 2 (12 T, 4. 2 K) Critical current density versus field 2450 A/mm 2 Hi-Lumi strand: Non-Cu Jc 2500 A/mm 2 (12 T, 4. 2 K) RRP 132/169 1340 A/mm 2 PIT 192 ITER A. Ballarino June 15, 2015 3 D. R. Dietderich, LBNL

LARP Nb 3 Sn Specification The 150 mm aperture QXF magnet program in LARP

LARP Nb 3 Sn Specification The 150 mm aperture QXF magnet program in LARP is initially using the RRP 108/127 Ti-Ternary strand. Strand specification Strand Diameter, mm Jc(12 T) at 4. 2 K, A/mm 2 Ic , A Jc(15 T) at 4. 2 K, A/mm 2 Ic , A ds, µm (nominal) Cu-fraction, % Cu/non-Cu RRR Piece length June 15, 2015 0. 85 > 2650 > 684 > 1400 > 361 < 60 > 53 > 1. 13 > 150 > 750 m 4 D. R. Dietderich, LBNL

FCC Nb 3 Sn Requirements CDP is now focusing on conductor needs beyond High

FCC Nb 3 Sn Requirements CDP is now focusing on conductor needs beyond High Luminosity LHC June 15, 2015 5 D. R. Dietderich, LBNL

Conductor Priorities for 20 T • Reduce cost – Need to reduce cost of

Conductor Priorities for 20 T • Reduce cost – Need to reduce cost of Nb 3 Sn and Bi-2212 – Can billets be scale-up • ~ 200 kg billets Nb 3 Sn, perhaps 50 kg for Bi-2212 • Need to establish process early • Increase piece length • Reduce subelement size (filament ) – Single re-stack or Double re-stack • Increase Critical Current Density (Jc) – Need to understand the origin of Jc variation between identical wire – Need to understand Nb 3 Sn formation – Need to understand loss of Jc as the wire diameter decreases – Shift pinning curve June 15, 2015 6 D. R. Dietderich, LBNL

Rounder Nb Filament • Better piece length • Perhaps better performance (Higher Jc )

Rounder Nb Filament • Better piece length • Perhaps better performance (Higher Jc ) June 15, 2015 7 D. R. Dietderich, LBNL

ATI - Nb Grain Structure Heat A Heat C OST working with ATI To

ATI - Nb Grain Structure Heat A Heat C OST working with ATI To improve Nb rods Rod Micrographs Nb Type 1 Edge of billet Center of billet Courtesy of Phil Olarey Microstructure can be vary across a billet ATI developing processing to improve uniformity June 15, 2015 8 D. R. Dietderich, LBNL

RRP® with more sub-elements Smaller Filament Size RRP® 54/61 RRP® 192/217 721 to 919

RRP® with more sub-elements Smaller Filament Size RRP® 54/61 RRP® 192/217 721 to 919 ~ 20 mm June 15, 2015 9 D. R. Dietderich, LBNL

CDP -- RRP® 192/217 Properties No SF correction CDP billet 14832 650 C/50 hrs

CDP -- RRP® 192/217 Properties No SF correction CDP billet 14832 650 C/50 hrs 30 m • RRR, Jc, and n-value decrease with decreasing wire diameter • Can reduce Sn to increase RRR • Reduced Sn may permit the 30% thicker barrier to be used in a 252/271 stack or greater – 37 µm sub-elements at 0. 85 mm June 15, 2015 10 D. R. Dietderich, LBNL

Sub-element Diameter, m • L. Cooley & A. Ghosh Formalization • LARP and OST

Sub-element Diameter, m • L. Cooley & A. Ghosh Formalization • LARP and OST Standard R=Cu/Non-Cu=1. 15 , 46. 5% SC, 53. 5 % Cu June 15, 2015 11 D. R. Dietderich, LBNL

Subelement Number • What sub-element size is needed for HE-LHC and future machines? •

Subelement Number • What sub-element size is needed for HE-LHC and future machines? • For a wire diameter of 0. 85 mm • Stack = Subelement size 271 = 42 mm 271 = 37 mm. . 721 to 919 ~ 20 mm Can this be produced? • If billet starting diameter is ~100 mm (4”) • Subelement diameter during billet fabrication is 3 -4 mm • At this size they are difficult to handle June 15, 2015 12 54/61 RRP® Perhaps cold extrusion for 6 -8” diameter billet D. R. Dietderich, LBNL

Formation of Nb 3 Sn – Re-design of RRP® Sub-element • Re-visit the design

Formation of Nb 3 Sn – Re-design of RRP® Sub-element • Re-visit the design of the RRP® subelement – Cu channels between filaments – Nb filament diameter – Barrier thickness and uniformity • Subelement will start to approach a tubular process • Jc decreases significantly for Ds below ~50 m – Need better understanding of tin / bronze diffusion and the interaction with Nb-Sn-Cu ternary as Ds↓ RRP reacted 210°C/48 hr + 400°C/48 hr, Courtesy of FSU (Peter Lee, Charlie Sanabria) • Collaborations with Sanabria (FSU), Pong (LBL) June 15, 2015 75 m 20 m 13 D. R. Dietderich, LBNL

Methods to Reduce Cost and Magnetization • Single barrier approach • ITER style conductor

Methods to Reduce Cost and Magnetization • Single barrier approach • ITER style conductor – Single barrier approach – Has lower magnetization and cost than RRP® – However, Jc is low • This would require an increase of the layer Jc – Increasing flux pinning – Recent work by OSU and Hyper Tech • No clear path to final conductor! June 15, 2015 14 D. R. Dietderich, LBNL

Double Re-stack • A “double restack” – restacking the restack – can access the

Double Re-stack • A “double restack” – restacking the restack – can access the smaller Ds at the desired wire size range – Need subelements tolerant to a high degree of deformation – Difficult to keep the Non-Cu fraction and Ic up, • Double restacking adds in extra copper 7 stack X 61 stack = 324 Ds ~ 20 m @ 0. 8 mm Perhaps one could cold extrusion a 6”-8” diameter billet June 15, 2015 15 D. R. Dietderich, LBNL

Conductor Performance Improvement • Need to increase current density at higher fields • Nb

Conductor Performance Improvement • Need to increase current density at higher fields • Nb 3 Sn - Shift pinning curve in wires to higher fields – Develop conductor with smaller grain Nb 3 Sn • Bi-2212 – Need to reduce porosity – Improve filament continuity Nb 3 Sn Target JE ~ 600 A/mm 2 Bi-2212 A. Godeke June 15, 2015 16 D. R. Dietderich, LBNL

J of wire for Pinning Curve Shift Godeke, et al. , unpublished Nb 3

J of wire for Pinning Curve Shift Godeke, et al. , unpublished Nb 3 Sn Target JE ~ 600 A/mm 2 Hc 2? June 15, 2015 17 New work Xingchen Xu of OSU and Hyper Tech on wires may be shifting the curve D. R. Dietderich, LBNL

Shift Pinning Curve of Nb 3 Sn Films of Nb 3 Sn with “Engineered

Shift Pinning Curve of Nb 3 Sn Films of Nb 3 Sn with “Engineered Microstructures” Grain size ~ 75 nm Dietderich and Godeke, Cryogenics 48, 331 (2008) June 15, 2015 18 Grain size ~ 20 nm Inclusions ~ 5 nm D. R. Dietderich, LBNL

Bi-2212 With Over Pressure Godeke, et al. , unpublished Target JE ~ 600 A/mm

Bi-2212 With Over Pressure Godeke, et al. , unpublished Target JE ~ 600 A/mm 2 Bi-2212 Magnet target has been achieved with overpressure processing June 15, 2015 19 D. R. Dietderich, LBNL

Material Properties • Conductor Development Program of HEP • Nb 3 Sn: – Understand

Material Properties • Conductor Development Program of HEP • Nb 3 Sn: – Understand strain behavior RRP Nb 3 Sn • Bi-2212 – Develop a high quality powder supplier – Increase critical current by exploring other powder compositions. – Improve strain tolerance of wire – Cable stress A. Godeke Ic drops at 60 MPa June 15, 2015 20 D. R. Dietderich, LBNL

Bi-2212 Goals • Reduce Cost – Bi-2212 needs a market other than HEP –

Bi-2212 Goals • Reduce Cost – Bi-2212 needs a market other than HEP – Scale up billet size • Can the amount of superconductor in wire cross section be increased? – Improve stress and strain tolerance – Area is now ~25%, need ~50% • Would this lead to processing issues since Bi-2212 powder has not strength? – This would double critical current of a wire for the approximately the same cost – Past wires with 50% Ag showed NO increase in Ic June 15, 2015 21 D. R. Dietderich, LBNL

Bi-2212 Effort in CDP • For a 1. 2 mm diameter wire with a

Bi-2212 Effort in CDP • For a 1. 2 mm diameter wire with a stack of 85 x 18 – No loss of critical current for twists lengths down to 12 mm • Increase strength of wire – Increase Ag alloy fraction in wire from ~24% to ~42 % • Could lead to more Bi-2212 in cross section • With over-pressure the wire Jc(4. 2 K, 12 T) is about the same as that of a std. wire June 15, 2015 Ag alloy (blue) 22 D. R. Dietderich, LBNL

Bi-2212 Future Directions • Concern about supply of high quality Bi-2212 powder – Supporting

Bi-2212 Future Directions • Concern about supply of high quality Bi-2212 powder – Supporting a Task to fabricate wires from the different powder suppliers • “ 521” composition has been the standard for many years – Can the critical current be increased by obtaining a better understanding of why it seems to be the best? – Or composition developed before? • 522, 523, & 524 developed by OST and Nexans • Try new compositions – Over pressure processing may require different composition • Improve filament continuity • The effective filament size of a wire is large: How can it be reduced? June 15, 2015 23 D. R. Dietderich, LBNL

End June 15, 2015 24 D. R. Dietderich, LBNL

End June 15, 2015 24 D. R. Dietderich, LBNL