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Coated conductors being used at the NHMFL are (not yet anyway) uniform
Data provided by Dmytro Abraimov (32 T testing), and further selected samples by Lidia Rossi, Xinbo
(Paul) Hu Jan Jaroszynski and Tak KametaniDavid Larbalestier
Data taken from D Abraimov(WAM-HTS Hamburg talk) and Lidia Rossi (MS thesis, University of Paris Marie Curie, June 2014 with stage at NHMFL Jan-Jun 2014)
Simple points
• Procurements have taken place over about 3 years
• SF 77K is not sufficient to specify conductor for any of our high field coils
• We have invested strongly in characterization capabilities
• Many variations are seen, more than those whose cause is understood!
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<Ic(4K;17T;18o)>
Inner Ic(4K;17T;18o)
Outer Ic(4K;17T;18o)
32T spec.
I c(4K
, 17
T, 1
8o),
A
Tape
M4passed with large margin
M3
The 32 T procurements show a very wide range of behavior even though supposed to be identical (each end short samples)
Abraimov WAM-HTS Hamburg
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M3 inner M3 outer M4 inner M4 outer
I c a
t 4.2
K e
xtra
po
late
d to
17
T, A
Ic SF; 77K, A
Self field 77 K does NOT provide good prediction of 4 K high field properties
Q: How do we (or the manufacturer) understand better such scatter?Partial A: in field at 77 K is better………
Abraimov WAM-HTS Hamburg
Lidia Rossi MS thesis
Select 5 from 100….
Lidia Rossi MS thesis
Conductor Ic at 0.5 T, 77 K
M4-151 M4-171-4 M4-142 Comment
B parallel ab 44 A 26 A - lowest 47 A - highest
B parallel c 55 A - highest 42 A 30 A - lowest
microscopy Dense c-axis BZO and ab-plane Re2O3
Fewer BZO c rods and many fewer ab- plane Re2O3
Few c-axis BZO nanorods with dominant ab plane ppts.
TEM by Fumitake Kametani
M4-151
M4-171
M4-142
Conclusion
• Both extrinsic and intrinsic defects control Ic in coated conductors and both types are present.
• In situ REBCO growth, especially with strong vortex pinning defects like BaZrO3 (BZO) is VERY susceptible to local growth perturbations that affect Jc(B, T, q) and Ic(x)
• The right tools – multiple ones – are needed to sort them out