Post on 05-Jan-2016
transcript
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).
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 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
StressQuenchA 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
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Nb-Ti
Nb3Sn
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Temperature (K)
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YBCO (^)
Bi-2223 (^)
Bi-2212 RW (^)
Nb-Ti
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 3
Plot maintained by Peter Lee at: http://magnet.fsu.edu/~lee/plot/plot.htm
Short sample Je of 2212 and YBCO soon exceed Nb3Sn
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 4
2 (or3?) viable HTS magnet conductors
YBCO with phenomenal Jc - ~20 x 106 A/cm2 at 25TBut YBCO is ~1% of cross-section50% is high strength superalloy
Round wire Bi-2212 – the preferred shape for cabling
2 m Ag
20m Cu
20m Cu
50m Hastelloy substrate
1 m HTS
~ 30 nm LMO
~ 30 nm Homo-epi MgO~ 10 nm IBAD MgO
< 0.1 mm
YBCO coated conductor4 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
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 5
Manufacturing processes are quite different
Powder in tube:2212 and 2223
IBAD-YBCO
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 6
Longitudinal defects in YBCO limit
transverse current transport
YBCO is a pilot plant product
Pilot manufacture at SuperPower and AMSCPre-pilot at Fujikura, Bruker, Sunam…..Pilot means many defects – manufacturing lengths of 500-1000 m lead to 70-120 m deliveries
Transport Ic over 5 m lengths
1 km spool
MO by Polyanskii, Ic(length) by SuperPower
4 mm
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 7
Debugging a recent test coil
Expected > 5T in 31T from 120m of tapeCoil quenched at about 20% expected IcThe Tapestar Hall array shows more local and bigger Ic drops
n value
Transport Ic
TapeStar
Xu conductor, Trociewitz and Dalban coil
YBCO
Hastelloy
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 8
Deconstructed YBCO coil shows
some present challenges
~30 - 70 m layer spacing due to “dog-boning” of conductorPacking density ~69 %No visible cracking of the epoxy
Glass fiber thread spacer Glass fiber thread spacer between filamentsbetween filaments
Interlayer Interlayer (wrapping paper)(wrapping paper)
Trociewitz, Dalban
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 9
Bi-2212 is normally reacted in place
NHMFL has made small coils generating 32T in 31TOxford has made coils giving 2.5T in 20TRound wire conductor (OST) allows easy winding and cabling for high currentMay be good for NMR
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~880ºC
2212 formed
2212 melted
Slow cooling
tmelt, timein the melt
Complex heat treatment
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)
Reasons for the complexity are being addressed
Shen, Jiang
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 10
OST wires with reduced porosity have high Jc (4.2K,5T) = 2900A/mm2 (Ic (4.2K,5T) = 862A)
Before reaction After reactionAfter reaction
After reactionAfter reactionAfter reactionAfter reaction
Shen, Jiang et al in VHFSMC collaboration with OST
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 11
Challenges remain with 2212 coils too
Layer 1… Layer 3… Layer 11… Layer 20
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Myers, Trociewitz
•Liquid BSCCO can leak through the Ag sheath•Coil performance is ~2/3 short sample performance•We are beginning to understand why
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 12
Conductor and Coil technologies are intimately
linkedCoils, R&D Test Beds
27T with SuperPower31T 2212 NHMFL
34 T YBCO NHMFL
HTS MagnetSystems
32 TZeemans
ConductorsYBCO 22122223
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 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!
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 14
A 2017 vision
YBCO and Bi-2212 will both be available in affordable, uniform, multi-km lengthsWe will be transitioning to round wire, multi-filament YBCO
32T will have satisfied many, many usersSmall coils will have achieved 40-50 THTS magnets will be widespread
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 15
David Larbalestier NHMFLDavid Larbalestier NHMFL Slide 16
Summary
StrengthsThe lab has a long tradition in HTS magnets – and now conductors
WeaknessesVery complex materials in pilot plant stageWeakening DOE support
OpportunitiesMake magnets impossible with NbFulfill COHMAGMake wise collaborations
ThreatsUnderestimate the challengesOverpromise and under-deliver