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Are HTS conductors up to the Magnet Builders’ vision yet?

Are HTS conductors up to the Magnet Builders’ vision yet?. David Larbalestier On behalf of the

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Are HTS conductors up to the Magnet Builders’ vision yet?

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  1. Are HTS conductors up to the Magnet Builders’ vision yet? David Larbalestier On behalf of the YBCO Conductor Group (Dmytro Abraimov, Tolya Polyanskii, Aixia Xu, Pei Li, Yan Xin, Valeria Braccini, Chiara Tarantini, Jan Jaroszynski), the 2212 Group (Tengming Shen, Eric Hellstrom, Ulf Trociewitz, David Myers, Andrea Malagoli, Jianyi Jiang, Fumitake Kametani) and the HTS Coil R&D group (Huub Weijers, Ulf Trociewitz, Jun Lu, Jan Jaroszynski, Patrick Noyes, Matthieu Dalban, David Hilton, Valeria Braccini and Aixia Xu) and 32 T (Denis Markiewicz).

  2. What does HTS offer us? • A decisive break from Nb-Ti and Nb3Sn • Jc is always limited by proximity to Hc2 • Bruker has just achieved the 1 GHz (23.5T at ~1.5K) in a Nb-Ti/Nb3Sn NMR magnet • A magnificent but asymptotic advance! • HTS removes the Hc2 or Hirr restriction but imposes new ones • Stress • Quench • A young and still primitive conductor technology because the materials are so much more complex than Nb-Ti or Nb3Sn Nb3Sn is limited to ~18 T in saddle magnets and ~ 24 T in solenoid magnets

  3. Short sample Je of 2212 and YBCO soon exceed Nb3Sn Plot maintained by Peter Lee at: http://magnet.fsu.edu/~lee/plot/plot.htm

  4. 2 mm Ag 1 mm HTS ~ 30 nm LMO ~ 30 nm Homo-epi MgO 20mm Cu ~ 10 nm IBAD MgO < 0.1 mm 50mm Hastelloy substrate 20mm Cu 2 (or3?) viable HTS magnet conductors • YBCO with phenomenal Jc - ~20 x 106 A/cm2 at 25T • But YBCO is ~1% of cross-section • 50% is high strength superalloy • Round wire Bi-2212 – the preferred shape for cabling YBCO coated conductor 4 x 0.1 mm Bi-2212 round wire ~ 1mm dia. Bi-2223 tapes represents a third possibility exhaustively studied for power applications 30-77K Now mature – lower Je than 2212 and YBCO

  5. Manufacturing processes are quite different IBAD-YBCO Powder in tube: 2212 and 2223

  6. Longitudinal defects in YBCO limit transverse current transport Transport Ic over 5 m lengths 1 km spool YBCO is a pilot plant product • Pilot manufacture at SuperPower and AMSC • Pre-pilot at Fujikura, Bruker, Sunam….. • Pilot means many defects – manufacturing lengths of 500-1000 m lead to 70-120 m deliveries 4 mm MO by Polyanskii, Ic(length) by SuperPower

  7. Debugging a recent test coil TapeStar • Expected > 5T in 31T from 120m of tape • Coil quenched at about 20% expected Ic • The Tapestar Hall array shows more local and bigger Ic drops Transport Ic n value YBCO Hastelloy Xu conductor, Trociewitz and Dalban coil

  8. Deconstructed YBCO coil shows some present challenges ~30 - 70 mm layer spacing due to “dog-boning” of conductor Packing density ~69 % No visible cracking of the epoxy Interlayer (wrapping paper) Glass fiber thread spacer between filaments Trociewitz, Dalban

  9. 2212 melted 2212 formed tmelt, time in the melt Bi-2212 is normally reacted in place Complex heat treatment ~880ºC • NHMFL has made small coils generating 32T in 31T • Oxford has made coils giving 2.5T in 20T • Round wire conductor (OST) allows easy winding and cabling for high current • May be good for NMR Slow cooling Temperature Shen, Jiang Time Reasons for the complexity are being addressed We lead a DOE-HEP effort to understand the limits of Bi-2212 for making strand, Rutherford cables and test coils VERY HIGH FIELD SUPERCONDUCTING MAGNET COLLABORATION (VHFSMC)

  10. OST wires with reduced porosity have high Jc (4.2K,5T) = 2900A/mm2(Ic (4.2K,5T) = 862A) After reaction Before reaction After reaction After reaction Shen, Jiang et al in VHFSMC collaboration with OST

  11. Challenges remain with 2212 coils too Layer 1… Layer 3… Layer 11… Layer 20 • Liquid BSCCO can leak through the Ag sheath • Coil performance is ~2/3 short sample performance • We are beginning to understand why Myers, Trociewitz

  12. Conductor and Coil technologies are intimately linked Coils, R&D Test Beds 27T with SuperPower 31T 2212 NHMFL 34 T YBCO NHMFL HTS Magnet Systems 32 T Zeemans Conductors YBCO 2212 2223

  13. Major macro issue: the DOE budget request to Congress January 2010 YBCO is commercial and DOE is going to end support and search for RT superconductors!

  14. A 2017 vision • YBCO and Bi-2212 will both be available in affordable, uniform, multi-km lengths • We will be transitioning to round wire, multi-filament YBCO • 32T will have satisfied many, many users • Small coils will have achieved 40-50 T • HTS magnets will be widespread

  15. Summary • Strengths • The lab has a long tradition in HTS magnets – and now conductors • Weaknesses • Very complex materials in pilot plant stage • Weakening DOE support • Opportunities • Make magnets impossible with Nb • Fulfill COHMAG • Make wise collaborations • Threats • Underestimate the challenges • Overpromise and under-deliver

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