High-performance Ba1−x K x Fe2As2 superconducting joints for persistent current operation

Abstract

High-performance superconducting joints are the key to achieving persistent-mode magnets. Herein, the superconducting joints between Ba1−x K x Fe2As2 (BaK-122) superconducting tapes were prepared by a simple cold-pressing method, and the joint resistance of the iron-based superconducting joint was estimated by field-decay method for the first time. Via the scanning electron microscope (SEM), electron backscattered diffraction (EBSD), electron probe microanalysis (EPMA) and x-ray computed tomography (XCT) measurements, it is found that the joint sample CP80 shows fine performance. At 4.2 K and 10 T, a transport critical current I c of 105 A for the joint sample CP80 was measured, and the critical current ratio (CCR = Ijoint c/Itape c) of the joint was 94.6%. On the other hand, the joints exhibit a pretty low joint resistance of 2.7 × 10−13 Ω in self-field at 4.2 K. Among iron-based superconductors, we are the first to estimate the accurate resistance of iron-based superconducting joint by the field-decay method. All these show the great prospective to apply BaK-122 in a series of practical applications that require superconducting joints as key components.