Ternary Nb3Sn superconductors with artificial pinning centers and high upper critical fields
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Date
2019
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Publisher
IOP Publishing Ltd
Abstract
In this letter we demonstrate the development of ternary Nb3Sn multifilamentary conductors with
artificial pinning centers (APC) which achieve high critical fields. These recently-developed
conductors were tested in a 31 T magnet, and the results showed that their upper critical field
(Bc2) values at 4.2 K are 27–28 T, and irreversible field (Birr) values are above 26 T, values
similar to or higher than those of best rod-restack-process (RRP) conductors. The non-Cu Jc has
been brought to nearly 1200 A mm−2 at 16 T and 4.2 K, comparable to RRP, in spite of the fact
that the fine-grain Nb3Sn fractions in filaments are still low (20%–30%) and the grain sizes are
still not fully refined (70–80 nm) due to conductor designs and heat treatments that are not yet
optimized. The Nb3Sn layer Jc at 4.2 K, 16 T is 4710 A mm−2 for the APC wire with 1%Zr,
about 2.5 times higher than RRP conductors, in spite of the fact that its grain size is not yet fully
refined due to insufficient oxygen and unoptimized heat treatment. An analysis is presented
about the non-Cu Jc that can be achieved by further optimizing the APC conductors and their
heat treatments.
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Citation
Published version: Xu et al 2019 Supercond. Sci. Technol. 32 02LT01. https://doi.org/10.1088/1361-6668/aaf7ca