Experimental Evaluation of the NbTi Inter-Winding Joint for CFETR Central Solenoid Model Coil

The Central Solenoid Model Coil (CSMC) project of China Fusion Engineering Test Reactor (CFETR) was begun in 2014 to develop and verify the manufacture technology of large-scale superconducting magnets. The CFETR-CSMC coil is mainly composed of inner Nb3Sn windings and outer NbTi windings. There are 12 joints in total, including six interwinding joints and six transition joints. A simple test facility is required for joint experimental evaluation. In this paper, the test facility, sample assembly, and installation and calibration of Hall sensor are described in detail. The first test results of NbTi inter-winding joint are also given. The resistance of the measured NbTi inter-winding joint is about 0.55 nΩ and changes slightly in the current range from 10 to 20 kA.