Verification Testing of ITER Nb3Sn Strand at the NHMFL

• Published in: IEEE transactions on applied superconductivity Vol. 25; no. 3; pp. 1 - 4
• Main Authors: McGuire, David R., Jun Lu, Hill, Scott, Dellinger, Kegan, Sloan, Timothy, Chan, Kevin, Martovetsky, Nicolai N.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-06-2015; Institute of Electrical and Electronics Engineers (IEEE)
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Critical current; Heat treatment; Hysteresis loss; Integrated circuits; ITER; Microscopy; Nb3Sn; Niobium-tin; Organizations; RRR; Temperature measurement; Wires; Nb3Sn; ITER; Critical current; RRR; hysteresis loss
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2014.2382032

The large quantity of Nb 3 Sn superconducting wire needed by ITER presents a significant challenge to ensure that all wires adhere to ITER specifications. The National High Magnetic Field Laboratory, USA performed verification tests for Nb 3 Sn strands used in ITER TF magnets. Converting a research laboratory into a large quantity testing facility presented many challenges in developing standard operating procedures for all the verification tests. Verification tests required by ITER include: unreacted-chrome-plated strand diameter, twist pitch and twist direction, chrome-plating thickness, unreacted-chrome-plated strand Cu-to-non-Cu volume ratio, residual resistivity ratio of Cr-plated strand (RRR), critical current at 4.22 K and 12 T (I c ), resistive transition index at 4.22 K and 12 T (n-value), and hysteresis loss per strand unit volume at 4.22 K over a ±3 T cycle. Additionally, due to the brittle nature of Nb 3 Sn superconducting wire, some samples were damaged in a controlled manner to explore the negative extremes of damage due to sample handling. We successfully completed the verification tests of ITER TF Nb 3 Sn strands made by US vendors.