Study of Cu fraction influence on Nb sub(3)Sn strand for ITER performance

• Published in: IEEE transactions on applied superconductivity 2000-01, Vol.10 (1), p.1004-1007
• Main Authors: Vorobieva, A, Shikov, A, Pantsyrnyi, V, Dergunova, E, Silaev, A, Belyakov, N, Kozlenkova, N, Polikarpova, M, Mareev, K, Malafeeva, O, Plashkin, E, Kuznetsov, S
• Format: Article
• Language: English
• Subjects: Approximation; Chromium; Copper; Diffusion coefficient; Mathematical analysis; Strands; Superconductivity; Tasks
• ISSN: 1051-8223
• DOI: 10.1109/77.828401

In frame of Se.C.R.E.T.S. international task Nb sub(3)Sn strands with 50 and 60% of Cu fraction have been produced and comparative research of their performance (Q, I sub(c), J sub(c), RRR, etc.) have been carried out. Strand design and processing were identical. However, the decrease of Cu fraction value has influenced on RRR value as well as Cr-plated and bare strands. By method of subsequent approximation the estimation of diffusion coefficients of Cr into Cu by R275/R20 values of both strands have been carried out. These calculations have shown that Nb sub(3)Sn strand after reaction at the standard regime (575 degree C 150 h+650 degree C 200 h at 10 super(-5) Torr) characterized the value of diffusion coefficient approximately 10 super(-12) cm super(2)/s, that has led to Cr penetration into oxygen free Cu in not more than 40 mu m of depth. The calculations of RRR integral value versus reaction time and Cu thickness have also been done. The relation of diffusion coefficient and microstructure of Cu-stabilization has been discussed.