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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Nb3Sn

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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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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