Subwinding Pack Embedding Experiment of CRAFT TF Coil

The Comprehensive Research Facility for Fusion Technology (CRAFT), national big science facility in China, is focused on exploring and building key technologies and prototype systems for 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 gigantic “D” shaped, consists of a winding pack (WP) and coil case. The WP is composed of 3 sub-WPs, called low (LF), medium (MF), and high field (HF) WPs, which are embedded to form the WP. The embedding gap between neighboring sub-WPs ranges from 10 mm at the inboard leg to 30 mm at the outboard leg and 120 mm at the helium inlet regions. The LF, MF, and HF WPs are wound separately by NbTi, conventional Nb
₃
Sn, and high property Nb
₃
Sn cable in conduit conductor. The fabrication of MF and HF WPs follows the routine of “Wind and React” approach; therefore, the maximum strain on the conductor shall not exceed ±0.1% during the whole embedding process. In this article, the embedding system is introduced, the strain of the conductor is analyzed, the embedding process is verified by 1/4 scale MF and HF model WPs. The results of analysis and experiment imply that the conceived embedding process is fully engineering feasible.