Void fraction research and destructive examination of CFETR toroidal field coil protype joints

The CFETR toroidal field coil (TFC) is designed to generate a peak magnetic field of 14.5 T at 4.2 K, with an operating current of 95.6 kA. The creation of superconducting joints is one of the most delicate parts of TF winding package (WP) fabrication, as the superconducting joints play an important role in the electrical and cooling circuit connection. ASIPP has produced a prototype sample containing three types of joints using a CFETR TF cable in conduit conductor (CICC) in 2022 and has obtained good resistance test values. This paper describes the study of joint void fraction (VF) and pixel-based image recognition analysis, and evaluation of contacts between conductive components. And the solution of the expansion of the twin box terminal in the manufacturing process and the groove design examination of spliced joints.