Conductor Development Project (CDP)

1. Conductor Development Project (CDP) Evaluating Nexans powders for Bi-2212 Round Wire Fabrication Yibing Huang, Hanping Miao, Seung Hong, Michael Gerace and Jeff Parrell Oxford Superconducting Technology Acknowledgements U.S. DOE –High Energy Physics CDP, Lawrence Berkeley National Laboratory & ASC - Florida State University EuCARD2 Meeting CERN, Dec. 12, 2013

2. CDP Project Compare 3 powders recently produced by Nexans in Lot #82 with different particle size distributions Regular ultra-fine powder (d50 ~ 1 µm) Standard granulated powder with particle size of 200-500 µm Special granulated powder with narrower particle size in 100-200 µm

3. Bi-2212 Wire Characterization Summary

4. Wire Cross-Section Comparison PMM130723-1 (1mm, FF~29%) PMM130723-2 (200-500 mm, FF~22%) PMM130723-3 (100-200 mm, FF~23%) • Fill factor of the wires made of granulated powder is on purposely made lower than that of the regular ultra fine powder. • Wiresmade of the granulated powders have relatively higher homogeneity and less filament merges after drawn to final size.

5. Regular Ultra Fine Powder Wire Cross-Section Comparison Wire from this work, FF ~29% Wire from old work, FF ~26% • Both wires were made withultra-fine powder (d50 ~ 1 µm) and the same process conditions. • Fill factor and filament merging appear different. • 16 hard particles per 60 sample cross-sections in samples from this work and none from wires with standard powder made in 2005.

6. Granulated Powder Wire Cross-Section Comparison Wire from old work, 100-500 mm powder Wire from this work, 200-500 mm powder • No significant difference in fill factor between wires made of old and new powders. • Some hard particles were observed in the new wires, none in the wires made before 2007.

7. Wire Performance Comparison • The JE performance is the similar in all three billets, showing that slightly better on wire PMM130723-2 by the granulated powder with particle size of 200-500 m. • The JE performance is similar for all three billets, • Jcis clearly higher in wires with the granulate powder.

8. Hard Particles Observed in New Wires Ultra fine powder, ~1m) 0.8mm wire (granulated powder, 100-200 mm) • Hard particles are observed in all three new wires and the higher frequency of hard particles occurred in the wires with 1 mm and 100~200 mm powders. • Most of hard particle are 10~40 mm, not to causing wire breakage, but leading to filament merge. Some of them are slightly Bi-rich and Cu deficit. • Eliminating hard particle is important to keep wire uniformity and piece-length.

9. Summary • All three wires are fabricated into single piece without breakage. • The JE performance is similar for all three billets, but Jc is clearly better on wires made of granulated powder. • Hard particles were observed in all three wires. • Need to remove the hard particle.