WB8-2

Development of Superconducting Coils using (Ba,A)Fe2As2 (A: Na, K) Round Wires with Large Critical Current

Dec.3 13:15-13:30 (Tokyo Time)

*Sunseng Pyon1, Tsuyoshi Tamegai1, Hideki Kajitani2, Norikiyo Koizumi2, Satoshi Awaji3, Hijiri Kito4, Shigeyuki Ishida4, Yoshiyuki Yoshida4

Dept. of Appl. Phys., The Univ. of Tokyo , Japan1

Naka Fusion Institute, National Institutes for Quantum and Radiological Science and Technology , Japan2

High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University , Japan3

National Institute of Advanced Industrial Science and Technology, Japan4

Iron based superconductors ( are one of the prom ising candidates for future high magnetic field application s because of their high critical temperature, Tc, high upper critical field, Hc2, and high critical current density, Jc. For application of IBSs to superconducting coils, dozens or hundreds of meters of wires or tapes with high critical current Ic, should be fabricated. Recently, fabrications of 100 m-class IBS tape and coils with the tape are reported [1]. On the other hand, there has been no report on IBS round wires longer than 1 m nor a coil with the wire. Although there have been several reports on critical current density Jc of the wire [2], not much attention has been paid to Ic. Here, we report the fabrication of 10 m-class (Ba,A)Fe2As2 (A:Na, K) wires and coils using long round wires. Round wires are fabricated by powder in tube (PIT) method and hot isostatic press (HIP) technique. To increase Ic keeping the diameter of the wire constant, the cross section area of the superconducting core is enlarged by changing the dimensions of metal sheaths. As shown figures (a) and (b), we fabricated the wire with twice larger superconducting core compared with that in the previous study [2]. At 4.2 K under a high field of 100 kOe, Jc of HIP wire is 42 kAcm2, which is comparable to the highest Jc of IBS round wires 44 kAcm2 [2]. As shown in figure (c), Ic of the HIP wire at 4.2 K under 100 kOe reaches 54 A, which is about twice the value of the previous report [2]. We will also report on the fabrication of a small demonstration magnet and generated magnetic field in this magnet

[1] X. Zhang et al., IEEE Trans. Appl. Supercond. 27, 7300705 (2017).
[2] T. Tamegai et al., Supercond. Sci. Technol. 33, 104001 (2020).

Figure. Optical photographs of cross sections of (Ba,Na)Fe2As2 HIP wires (a) in the previous study [2] and (b) in this study. (c) Magnetic field dependence of transport Ic of (Ba,Na)Fe2As2 HIP wires shown in (a) and (b).

Keywords: Iron based superconductor, Superconducting coil, Critical current, PIT HIP wire

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