Fabrication of multi-filament(Ba,<i>A</i>)Fe<sub>2</sub>As<sub>2</sub> (<i>A</i>: Na, K) HIP round wires and a small superconducting coil
Sunseng Pyon, Takamasa Ito, Ryosuke Sakagami, T. Tamegai, Satoshi Awaji, H. Kitô, Shigeyuki Ishida, Hiroshi Eisaki, Yoshiyuki Yoshida, Hideki Kajitani
Abstract
Abstract We report the fabrication and systematic characterizations of multi-filament (Ba, A )Fe 2 As 2 ( A : Na, K) round wires processed under high pressure. The evaluated transport and magnetic critical current density show clear core-number dependence. This trend originates from degradation of the superconducting core during the wire-drawing process, degradation of the concentric texturing of the core, and the enhanced sausaging effect of the core (revealed by x-ray tomography) as the number of cores increases. Details of the characterizations and suggestions for the improvement of the fabrication process are discussed. We constructed a superconducting magnet using seven-filament (Ba,K)Fe 2 As 2 hot-isostatic pressed round wires. The generated magnetic field and critical current ( I c ) of the coils at 4.2 K are 1.0 kOe and 18 A, respectively. Measurements of the I c of short segments picked up from the coil show that there is enough room for improvements.