Plasma and Fusion Research

Volume 3, 042 (2008)

Regular Articles

Mitigation of Critical Current Degradation in Mechanically Loaded Nb₃Sn Superconducting Multi-Strand Cables by Ice Molding

Kazutaka SEO, Arata NISHIMURA, Yoshimitsu HISHINUMA, Kazuya NAKAMURA¹⁾, Tomoaki TAKAO¹⁾, Gen NISHIJIMA²⁾ and Kazuo WATANABE²⁾

National Institute for Fusion Science, Oroshi-cho 322-6, Toki-city, Gifu 509-5292, Japan
1): Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
2): IMR, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Miyagi 980-8577, Japan

(Received 28 August 2007 / Accepted 18 April 2008 / Published 17 July 2008)

Abstract

We have developed a novel critical current and stability measurement experimental setup, which utilizes a closed electric circuit with a multi-strand superconducting cable. The feature of this setup is mechanical loading applied to the multi-strand cable in the transverse direction. It was reported that Lorentz forces caused degradation in the critical current of the ITER-TFMC conductor. Furthermore, these phenomena were mainly observed in the ITER full-size conductors with large Lorentz forces under high magnetic fields. The advantage of our setup is critical current measurement under mechanical stresses comparable to those in the full-size conductor under high magnetic fields. By employing an inductive critical current measurement technique, we conducted an experiment with a transport current of about 10 kA without any power supply or current leads. In our experiments, we observed significant degradation in critical currents due to a compressive stress of about 30 MPa. We applied an innovative technique to mitigate the critical current degradation in mechanically loaded Nb₃Sn superconducting multi-strand cables. We molded one such cable with ice and tested it. No degradation occurred in the icemolded cable. In addition, stability was also ensured due to the large thermal conductivity of ice. Thus, we have successfully mitigated the degradation in the critical current of the Nb₃Sn conductor by ice molding.

Keywords

Nb₃Sn, critical current degradation, transverse load, cable-in-conduit conductor, ice molding

DOI: 10.1585/pfr.3.042

Full Text

PDF format (1.6Mbytes) PDF Download

References

[1] ITER Design Description Document (DDD), 11, Magnet (N 11 DDD 177 04-05-12 W 0.2) (2004).
[2] A. Nishimura et al., J. Plasma Fusion Res. 83, 30 (2007).
[3] N. Mitchell, Cryogenics 43, 255 (2003).
[4] A. Ulbricht, J.L. Duchateau, W.H. Fietz, D. Ciazynski, H. Fillunger, S. Fink et al., Fusion Eng. Des. 73, 189 (2005).
[5] K. Seo, Y. Hishinuma, A. Nishimura, G. Nishijima, K. Watanabe, K. Nakamura, T. Takao and K. Katagiri, Fusion Eng. Des. 81, 2497 (2006).
[6] K. Seo, A. Nishimura, Y. Hishinuma, K. Nakamura, T. Takao, G. Nishijima, K. Watanabe and K. Katagiri, IEEE Trans. Applied. Supercond. 17, 1390 (2007).
[7] P. Fabbricatore, R. Musenich, R. Parodi, D. Truffelli and G. Zappavigna, IEEE Trans. Magn. 27, 1818 (1991).
[8] G.B.J. Mulder, H.H.J. Ten Kate, A. Nijhuis and L.J.M. Van de Klundert, IEEE Trans. Magn. 27, 2190 (1991).
[9] S. Iida, New edition - Table of physical constant (Asakura Publishing Co., Ltd., 1978) p.123 [in Japanese].
[10] J. Klinger and G. Rochas, J. Phys. Chem. B 87, 4155 (1983).
[11] T. Shigi et al., Cryogenic Engineering Handbook (Uchida Rokakuho Publishing Co., Ltd., 1982) p.582 [in Japanese].
[12] V.F. Petrenko and R.W. Whitworth, The Physics of Ice (Oxford University Press, 1999) ISBN 0-19-851895-1.
[13] K. Seo, S. Nishijima, K. Katagiri and T. Okada, IEEE Trans. Mag. 27, 1877 (1991).

This paper may be cited as follows:

Kazutaka SEO, Arata NISHIMURA, Yoshimitsu HISHINUMA, Kazuya NAKAMURA, Tomoaki TAKAO, Gen NISHIJIMA and Kazuo WATANABE, Plasma Fusion Res. 3, 042 (2008).