[6p-S42-1~18] 11.3 Critical Current, Superconducting Power Applications

[6p-S42-12] In-field Scanning Hall Probe Microscopy of Hot-pressed Ag-sheathed (Ba,K)Fe₂As₂ Tape

〇Takanobu Kiss¹, Koki Tamae¹, Shyam Mohan¹, Shuhei Bochi¹, Kohei Higashikawa¹, Masayoshi Inoue¹, He Huang², Chao Yao², Yanwei Ma² (1.Kyushu Univ., 2.IEE CAS)

Keywords:superconductor, iron pnictide, tape wire

Iron-based superconductors have a great potential for high field applications because of its superior in-field current transport characteristics with high irreversibility fields and low anisotropy. Recently, promising value of critical current density, J_c, was obtained by use of hot-pressing process, and even 100-m-class long length tapes has already been demonstrated. Nevertheless, current limiting mechanism is not yet fully understood. In this study, we investigated J_c distribution in a hot pressed Ag-sheathed (Ba,K)Fe₂As₂ tape by use of in-field scanning Hall-probe microscopy (SHPM). We have succeeded in obtaining remanent field signal even in such high back ground field as 4 T. Even though the tape contains a single flat core, we observed two parallel filamentary structures. Namely, the central region of the filament decoupled each other most probably because of the pressing process. Local critical current distribution is also obtained from the magnetic imaging by solving inverted Biot-Savart law. The present method is powerful to derive local J_c, because it is impossible to derive J_c only from magnetic moment of the whole sample. Obtained critical current, Ic, shows good agreement with transport measurements. We also noticed that the field dependence of I_c is very small. This suggests strong flux pinning of the tape. In the presentation, more detailed analysis including flux creep will also be presented.