Overview of the Design Status of the Superconducting Magnet System of the CFETR

The concept design of the China Fusion Engineering Test Reactor (CFETR) was started in 2012 in two stages. For CFETR-Phase I, the major radius is 5.7 m, the minor radius is 1.6 m, and the magnetic field at the plasma region, BT, is 4-5 T. There were 16 toroidal field coils and six central solenoid coils designed by a Nb3Sn cable-in-conduit conductor (CICC) with the maximum operation current of 64 and 50 kA, respectively. Three types of plasma equilibrium configuration (ITER-like single null, super-X, and snowflake) were designed. The maximum flux provided by the central solenoid is set at 180 V·s. However, to get much higher operation parameters such as steady-state operation, particle and heat exhaust, disruption mitigation and avoidance, ELM control, and material damage by high heat flux and neutron, the superconducting magnet system of CFETR-phase II has been updated based on the larger machine with R = 6.7 m-7.0 m, a = 2.0 m, and BT= 6.5-7 T. Such a new design makes over 1-GW fusion power and better plasma performance possible. Hybrid TF coils are designed by a high-performance Nb3Sn conductor, since the maximum magnetic field can reach to 14-15 T. Besides, in order to save the space for the blanket system and get higher flux, a high-temperature superconducting Bi-2212 magnet with better current-carrying performance under high field is supposed to be employed for the CS coils of CFETR-phase II. The Bi-2212 CICC sample has been tested at 4.2 K with a critical current of 26.6 kA under its self-field.