Takanobu Kiss1 Shuhei Bouchi1 Kohei Higashikawa1 Masayoshi Inoue1 Hiroaki Kumakura2 Dongliang Wang3 Yanwei Ma3

1, Kyushu University, Fukuoka, , Japan
2, NIMS, Tsukuba, , Japan
3, IEE CAS, Beijing, , China

Combining X-ray tomography and in-field scanning Hall probe microscopy (SHPM), we have succeeded in visualizing local distortion of filaments in IMD processed-MgB2 wires and their influence on critical current distribution in the MgB2 wires. High resolution X-ray tomography is a powerful tool to investigate filamentary architecture and local distortion such as sausaging effect and exudation of Mg. From the magnetic image of the magnetized MgB2 wire measured by the SHPM, we could evaluate spatial distribution of local critical current density, Jc, according to Biot-Savart law. The in-field SHPM allows us to evaluate critical currents quantitatively of the MgB2 wire with magnetic sheath materials by the measurement where the external magnetic field is higher than the saturation field of the magnetic sheath [1]. The advantage of such magnetic measurements is also to evaluate high current region in which transport method is difficult to apply. Combination with the X-ray tomography and the SHPM leads abundant information on current limiting mechanism of the MgB2 wires by synergistic effect.

[1] K. Higashikawa et al., IEEE Trans. Appl. Supercond. 26 (2016) 6200804.

Acknowledgements: This study was supported by Japan Science and Technology Agency (JST) as ALCA and also by by Japan Society for the Promotion of Science (JSPS) and Chinese Academy of Sciences (CAS) under the Japan – China Research Cooperative Program.