In this letter we demonstrate achievement of record non-Cu critical current
density (Jc,non-Cu) in ternary, multifilamentary Nb3Sn conductors by the
introduction of artificial pinning centers (APC). In the past two years, we
have made great progress in the development of APC Nb3Sn wires. Recent
resistivity vs magnetic field measurements confirmed the high upper critical
field (Bc2) of ternary APC wires, which at 4.2 K was ~28 T, about 1-2 T higher
than present state-of-the-art conductors. In addition to high Bc2, it was found
that APC wires have noticeably higher Sn content in the Nb3Sn layers as
compared to standard wires. The Jc,non-Cu values of the most-recent APC wires
have met the Jc,non-Cu-B specification required by the Future Circular Collider
(FCC), with the best heat treatment leading to a Jc,nonCu 29% higher than the
FCC specification at 21 T. Microscopy analysis shows that the APC wires still
have overly high residual Nb fractions due to too low of a Sn/Nb ratio,
indicating that there is still great potential for further Jc,non-Cu
improvement. The development of APC wires is ongoing; this letter details some
of the steps forward in the optimization and lays out a roadmap to push the APC
wires towards practical, magnet-grade conductors.Comment: 4 figure
