Analysis and Verification of CRAFT TF Coil Turn Insulation Wrapping System

The Comprehensive Research Facility for Fusion Technology (CRAFT), national big science facility in China, is focused on exploring key technologies and building prototype systems for the Chinese Fusion Engineering Test Reactor (CFETR). The toroidal field (TF) coil is one of the most important parts of CRAFT, targeting at manufacturing a prototype TF coil for CFETR. The TF coil is a gigantic “D” shape, which consists of a winding pack (WP) enclosed in the coil case. The winding pack is composed by embedding three sub-WPs, called low, medium, and high field WPs. The conductor of the high and medium WPs is fabricated from Nb
₃
Sn, follow the “winding and reaction” approach. As one of the most critical steps, turn insulation has to be wrapped after the heat treatment of the conductor. Since the superconducting property of Nb
₃
Sn is deeply sensitive to the strain, the strain must be strictly controlled during the wrapping process. In this article, the concept design of the wrapping system is introduced. Analysis of strain and construction of the wrapping mathematic model are performed and verified by the wrapping trial. Based on the abovementioned results, the detail design of the wrapping system has been completed and the machine is currently being manufactured.