CEC-ICMC 2017 - Abstracts, Timetable and Presentations

The development of high pinning site densities in multifilamentary PIT wires using the internal oxidation route

10 Jul 2017, 17:30

15m

Hall of Ideas - EH

Contributed Oral Presentation M1OrF - Focused Session: Pushing Nb3Sn Conductors Beyond the State of the Art

Speaker

Peter Lee (Florida State University)

Description

Prior to his passing in late 2016, Leszek Motowidlo
developed a method of applying the Nb-1Zr/SnO₂ internal oxidation method
to APC Nb₃Sn through a powder-in-tube (PIT) approach that used low-cost
Cu₅Sn₄ powder as the Sn source. Two designs of
multifilamentary PIT wire were successfully produced and fine-grain A15 layers
with average grain diameters as small as 30 nm were obtained. High
resolution field emission SEM also indicated the presence of point pinning
sites, particularly at grain boundaries. Magnetization and transport critical
current tests showed a shift in the peak of the pinning force curve toward
higher magnetic field. Deconvolution of the pinning force curves indicated a
strong point pinning component, perhaps produced by the ZrO₂
precipitates. It was found that the degree of microstructural refinement was very
sensitive to the volume percent of SnO₂ in the core. This
presentation will also look at some limitations of this technique, which
included a strong gradient in grain size, uneven distributions of point-pinning
sites and relatively low levels of conversion of Nb₆Sn₅
to Nb₃Sn. Such compromises will need to be addressed to make this
approach competitive with more fully developed conventional internal Sn and PIT
Nb₃Sn wires.

Support

The work is funded by the High Energy Physics division of
the US Department of Energy under a Phase I SBIR award DE-SC0009605. A portion
of this work was performed at the National High Magnetic Field Laboratory,
which is supported by National Science Foundation Cooperative Agreement No.
DMR-1157490 and the State of Florida.