WB10-3
Fabrication of superconducting coil and (Ba,Na)Fe2As2 long round wire with large superconducting core
*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 (IBSs), especially 122-type (AE,A)Fe2As2 (AE: Ba,Sr. A: K, Na), have been studied as promising candidates for future high-magnetic-field applications. Critical current density Jc of uniaxially pressed tape of (Ba,K)Fe2As2 has exceeded the practical level of 100 kA/cm2 and reached 150 kA/cm2 at 4.2 K under 100 kOe [1]. Jc of round wire, whose isotropic shape is more advantageous than that of flat tape, has been improved steadily. It is reported that Jc in (Ba,Na)Fe2As2 and (Ba,K)Fe2As2 HIP round wires reach 54 and 47 kA/cm2 at 4.2 K under 100 kOe, respectively [2,3]. Using these promising materials, long wires or tapes and superconducting coils have been fabricated [2,4]. 100-m class (Sr,K)Fe2As2 tape and superconducting coil were fabricated [4]. Recently, we reported the generation of magnetic field of 2.6 kOe at 4.2 K using 10-m class (Ba,Na)Fe2As2 round wire [4].
We have reported that critical current Ic can be increased by making the core area larger by controlling the size of Cu/Ag-sheath of the wire [5]. For further enhancement of Ic in round wires and generating higher magnetic field, we prepare a long HIP round wire with 2.5 times larger core area compared with that of wire used for the construction of the demo coil [2]. Figure (a) shows an optical micrograph of (Ba,Na)Fe2As2 round wire with larger superconducting core using thinner Ag-sheath compared with that in previous wire [2] shown in Fig. (b). Figure (c) shows that magnetic Jc of a short piece of the wire reaches 48 kA/cm2 at 4.2 K under 40 kOe, which is ~70% of the highest Jc [2]. Although relatively high magnetic Jc is demonstrated, transport Ic of the wire is significantly lower than that for the previous long HIP wire due to reduction of mechanical strength and sensitivity to strains caused by benting. In the presentation, we will report detailed characterizations of the new long HIP wire with large core area. Furthermore, utilizing these information, we will fabricate another long HIP wire of (Ba,Na)Fe2As2, and report the performance of the coil using this wire.
[1] H. Huang et al., Supercond. Sci. Technol. 31, 015017 (2018).
[2] S. Pyon et al., Supercond. Sci. Technol. 34, 105008 (2021).
[3] W. Guo et al., Supercond. Sci. Technol. 34, 094001 (2021).
[4] X. Zhang et al., IEEE Trans. Appl. Supercond. 27, 7300705 (2017).
[5] T. Tamegai et al., Supercond. Sci. Technol. 33, 104001 (2020).
Figure. Optical photographs of cross sections of (Ba,Na)Fe--2As2 HIP wire in (a) this study and (b) previous study [2]. Yellow bars in (a) and (b) indicateswork ])seld.tape, have 0.5 mm. (b) Magnetic field dependence of magnetic Jc of (Ba,Na)Fe--2As2 HIP wires shown in (a).
Keywords: Iron-based superconductor, Superconducting coil, Critical current, HIP round wire
