HTS Wire for Ultra-High Field Superconductor Magnets

Summary

This presentation explores the feasibility, status, and engineering challenges of using high-temperature superconducting (HTS) wire to develop ultra-high field all-superconducting DC magnet systems up to 50 T. It evaluates 2G REBCO and BSCCO wire performance under severe hoop stress and magnetic field requirements, reviews global magnet initiatives, and outlines commercial production readiness and development hurdles.

Slide 1: Title

A. P. Malozemoff Consultant to AMSC, Devens MA

AMSC | Windtec Solutions | Gridtec Solutions

Slide 2: A Breakthrough Opportunity in All-SC Ultra-High-Field Magnet Systems

• Highest all-LTS-superconductor magnet: Bruker 23.5 T (1 GHz) NMR magnet — Near asymptotic limit for low temperature superconductors (NbTi/Nb3Sn) • HTS materials like YBCO have enormous (~100 T) upper critical field in low-T limit — Opens up a potentially huge new range of fields for science and NMR, using all-superconductor magnets • HTS wires are now commercially available, enabling such magnet systems

All-SC magnet systems from 23.5 up to 50 T?

Slide 3: Towards a 50 T All-Superconductor DC Magnet System

• Exceed present highest DC field magnet: the 45 T hybrid at the National High Magnetic Field Lab (NHMFL) • Reduce operational cost (typical Bitter magnets cost $2000/ h r . t or u n, or, f or a y e a r o f co n t in u o u sr u nnin g$ 17.5 M!) — All-superconducting magnets would eliminate this dominating cost, expanding use dramatically • Avoid noise from forced water cooling of Bitter magnets • Enable revolutionary new science — Far more sensitive physics experiments probing quantum oscillations, decoherence, quantum computation, etc. — Far higher resolution in NMR for bioscience

An impossible dream or credible opportunity?

Slide 4: Could 50 T All-SC Magnets be Possible? (Stress and Current Density)

• Hoop stress σh = J x B x r • Assume σh = 500 MPa • Extrapolation to 50 T gives 4 cm bore, requires ~500 A/mm² under 50 T axial field

[Figure 3: A calculation example of the current densities and peak field in the case of σh = 500 MPa. Number of coils = 10, Coil outer radius = 130 mm, Coil length = 520 mm, B0 = 36.5 T, E = 4.5 MJ. Otsuka & Kiyoshi, High Field Magnet Design Under Constant Hoop Stress, IEEE TAS, 2008]

Slide 5: Could 50 T All-SC Magnets be Possible? (Field Anisotropy)

• HTS wires tape-shaped, with anisotropic field-dependence • Possible design will have: • 50 T axial field parallel to tape at inner bore • 15 T field perpendicular to tape at HTS coil ends

[Diagram showing 20 T LTS outsert surrounding HTS insert providing 20 T + 30 T = 50 T axial field (parallel to tape orientation) and 15 T perpendicular field at ends]

Slide 6: The HTS Conductor Choices

• Bi-2223 multifilament tapes (AMSC) Bi-2223 tapes exhaustively studied for power applications 30-77K: Now mature – lower Je than 2212 and YBCO • Bi-2212 round wire ~ 1mm dia. (Oxford SC) • REBCO coated conductor tapes (SuperPower) 4-12 mm wide by ~ 0.1 mm thick structure:

20 µm Cu
2 µm Ag
~ 1 µm HTS
~ 30 nm LMO
~ 30 nm Homo-epi MgO
~ 10 nm IBAD MgO
50 µm Hastelloy substrate
20 µm Cu

Larbalestier - SciMag NRC Panel: Washington DC, March 12, 2012

Slide 7: Example: AMSC Amperium™ 2G Wire

• Processed wide, then slit to desired width • Laminated with copper, stainless… for strength, electrical stabilization • Cross-section: Copper laminates surrounding Substrate – Ni-5W and HTS – 1 µm YBCO layer (Total thickness: 200 µm) • Comparison showing Cu vs HTS 1000 A equivalents

Well-established process producing 100’s km wire yearly

Slide 8: 2G HTS Wire Available in Long Length with High Uniformity

• Amperium™ Copper Laminated 12 (~300 A/cm-width):

3-layer, 10 mm wide HTS, 12 mm Cu
Average Ic = 296 A, σ = 3.7 A (1.2%) over 500+ m • Beta Wire – Double Insert (~550 A/cm-width effective):
4-layer, 10 mm wide HTS, 12 mm Cu
Average Ic = 541 A, σ = 3.2 A (0.6%) over 200+ m

High uniformity essential for stable operation

Slide 9: Can HTS Wire Meet Hoop Stress Requirement for a 50 T Magnet? YES!

e. g. SEI 1G (BSCCO) wire reinforced with 0.02-0.1 mm stainless steel Tensile strength @ 77 K (MPa) vs Ic retention (%):

SUS 0.10 mm maintains Ic retention up to ~500 MPa
SUS 0.05 mm maintains Ic retention up to ~380 MPa
SUS 0.02 mm maintains Ic retention up to ~270 MPa

K. Sato et al., JJAP 51, 2012 K. Sato, SEI: “500 MPa of tensile stress will be feasible”

Slide 10: Does Existing 2G HTS Wire Have Enough Jc(H) for a 50 T Magnet? YES! (just)

Current Density Across Entire Cross-Section (Je [A/mm²], 4.2 K vs Applied Field [T]):

Je for 15 T perpendicular field: 500 A/mm² (YBCO B ⊥ Tape Plane)
Je for 50 T parallel field: 1300 A/mm² (YBCO B || Tape Plane)
Comparison data includes NbTi, Nb3Sn (Bronze and RRP), Bi-2212 round wire, Bi-2223 tape

Note: BSCCO 2223 tape, round BSCCO 2212 wire possible future contenders. Larbalestier, NHMFL / SuperPower

Slide 11: Principal Commercial HTS Wire Producers Today

• AMSC – 2G wire: Ni-W substrate, MOD REBCO, laminated stabilizer • Bruker – 2G wire: Stainless steel substrate, PLD REBCO, laminated or electrodeposited stabilizer • Fujikura – 2G wire: Hastelloy substrate, PLD REBCO, electrodeposited stabilizer • Sumitomo Electric (SEI) – 1G wire: BSCCO/Ag composite, laminated stabilizer • SuperPower-Furukawa – 2G wire: Hastelloy substrate, MOCVD REBCO, electrodeposited stabilizer

A growing HTS wire industry, but no standardization yet

Slide 12: Remaining Hurdles for 50 T HTS Magnet Wire

• Wire for ultra-high-field magnet systems still requires development • Optimization still needs to be done to further enhance Je at 4.2 K and ultra-high-field beyond today’s marginal values • Even higher strength tapes could be developed, e. g. by laminating to a thin tape of CuNb with yield strength > 1 GPa • No wire producer yet combines all the wire characteristics needed for a 50 T magnet • Cabling may be needed for some designs; industrial Roebel cabling still rudimentary • Are HTS wire producers interested in such a relatively small market, in comparison to the huge wire-volume opportunities in power cables, wind generators and fault current limiters? • Would they be willing to pursue the necessary development work under government contract?

HTS wire already meets intermediate field requirements

Slide 13: How about Industrial Producers of Magnet Systems? (excluding MRI)

• Agilent (former Varian) – NMR systems • AMSC – all HTS magnet systems (e. g. 7 T research magnet) – now focused on coils for rotating machinery • Bruker – NMR systems with world’s highest field all-LTS system; also has BEST as HTS wire source; planning 28 T HTS NMR • Cryomagnetics – cryofree SC magnet systems • HTS-110 – so far mostly lower field HTS coils • Kobe Steel and JASTEC – cryofree SC magnet systems, NMR • Oxford Instruments – cryofree SC magnet systems, has worked with NHMFL on ultra-high-field HTS coil tests using Bi-2212 round wire • SEI – all HTS magnet systems (7 T research magnet) • Toshiba – cryofree LTS magnet systems, today focused on ITER, Maglev

Are any of these ready to address hi-field HTS systems?

Slide 14: NIMS/JASTEC(Kobe Steel) 24 T All-SC Magnet System Demo: Tsukuba

S. Matsumoto et al., SUST, 2012 • 515 m of Fujikura GdBCO 2G wire in layer wound coil w/5 cm i. d. • Configuration: GdBCO insert coil installed in 17.2 T low-temperature superconducting (Nb3Sn and Nb-Ti) magnet.

Highest all-superconductor field to date

Slide 15: Ultra High-Field Magnets Demonstrated at 4.2 K with Zr-Doped MOCVD Conductors

University of Houston & SuperPower • Je ~ 300 A/mm² • Stress levels 300 – 400 MPa • Coils tested:

SuperPower I: Bmax = 26.8 T, ΔB = 7.8 T
SuperPower II: Bmax = 27 T, ΔB = 7 T
NHMFL II: Bmax = 35.4 T, ΔB = 4.2 T

Slide 16: SEI 7T All-HTS Magnet System: 1G DI-BSCCO Wire, 20 K Operation

K. Sato et al., JJAP 51, 2012 • Refrigerator-cooled Bi-2223 magnet system (20 K operation, 50 mm bore) • Double pancake coils wound with Bi-2223 wires

SEI a leader in both HTS wire and its applications

Slide 17: NIMS, Kobe Steel, JASTEC 24.2 T NMR Magnet System – in progress

Kiyoshi et al., IEEE TAS 2010 • Uses SEI 1G “DI-BSCCO” wire • Coil configuration of the 1.03 GHz NMR magnet with Bi-2223 inner coil and Nb3Sn outer coils

First operating NMR system w/HTS insert – target 2012

Slide 18: NHMFL 32 T: The First HTS User Magnet

• High field 24/7 use:

Low operating cost
Breakthrough from current 18/20 T level • HTS Technology choices:
REBCO Coated conductor, single strand
Conservative design with margin • Focused project team:
Reliability is key
Supported by broader, aggressive R&D program • Close interaction with conductor vendor • The first ever all superconducting magnet with B > 24T • Key technological choices made; Now: full-featured test coils; 2013: User operations • Specifications: 32 T, 4.2 K, 32 mm bore; Standard “physics” homogeneity; Dilution refrigerator: <20 mK; HTS/LTS hybrid (LTS outsert from industry: Ø574mm, 745mm height; YBCO inner coil, Nb3Sn, NbTi)

Larbalestier - SciMag NRC Panel: Washington DC, March 12, 2012

Slide 19: Other HTS Magnet Projects and Plans

• Brookhaven National Lab HTS Magnet Program plans: • 24-30 T torus for ARPA-E SMES project (GRIDS SMES SYSTEM w/ SuperPower/University of Houston 2G HTS Wire, ABB Power Converter) • 40 T HTS solenoid test in 19 T resistive magnet background field: muon accelerator program (MAP) with Fermilab muon collider proposal • Grenoble High Magnetic Field Laboratory: • Interest in HTS for high fields, but no funded program yet • European funding for 5 kA HTS cables • LHC energy upgrade – CERN: • Goal ~20 T dipoles

Slide 20: Summary: HTS-Based All-SC Ultra-High Fields – a Revolutionary Opportunity

• HTS opens up the entire field range from 23.5 T to ~50 T for all-superconductor magnets • Multiple companies producing commercial HTS wire: Wire quality and quantity has matured to the point of enabling all-SC magnets >24 T, though more optimization required to achieve full range • Multiple companies have high field magnet systems expertise: Several already involved in initial ultra-high-field all-SC magnet systems • Government funding and co-operation with high field magnet labs like NHMFL or Tsukuba are likely needed

International race is on to capitalize on this opportunity