Fabrication, analysis and preliminary test of the rectangular Bi2212 CICC in the CHMFL

Abstract The High Magnetic Field Laboratory of China (CHMFL) is developing high-temperature superconducting (HTS) magnets for the upgraded 55–60 T magnet. This is the first Bi2212 cable-in-conduit conductor (CICC) fabricated in the CHMFL with a rectangular-shape to serve the hybrid magnet. The fabrication of the Bi2212 CICC has technical challenges that must be overcome to optimize the critical performance in engineering applications. This paper details the fabrication technology, including cabling, jacketing, heat treatment (HT), and leakage detection, with critical current ( I c ) tests at low temperatures. The Bi2212 conductor has the characteristics of rectangular, long twist pitch, low void fraction, and large deformation of the wires and sub-cables. It has no central cooling channel and soft-silver tube, smaller in size and higher in engineering current density ( J e ), similar to the real conductor. The rectangular Bi2212 CICC, including 60 superconducting wires, exhibits 34.5 kA at 15 K and exceeds 40 kA at 4.2 K. The current sharing temperature ( T cs ) was up to 40 K at 10 kA, and no quench occurred. The resistance of the terminal joints reaches the nΩ-level. This paper presents a detailed fabrication technology of the Bi2212 CICC for the future engineering design of HTS magnets.