Concept design of hybrid superconducting magnet for CFETR Tokamak reactor

CFETR which stands for “China Fusion Engineering Test Reactor” is a new tokamak device. The mission and goal of CFETR are as follows: (1) ITER-like; complementary with ITER; (2) Fusion power 50-200 MW; (3) Duty cycle time (or burning time)~(30-50%); (4) Tritium must be self-sufficiency by blanket. The main parameters of low temperature superconducting magnet system are as follows: (1) The central magnetic field in plasma area is designed as 5.0 T. (2) The major and minor radius of plasma is 5.7 m and 1.6m. The main parameters of CFETR´s were optimized several times within past year according to the further physical target and engineering. Due to the restrictions of the critical magnetic field strength, low temperature superconducting conductor may difficulty applied in low aspect ratio tokamak device in a limited space. In order to achieve a much higher central magnetic field in plasma area and much higher maximum capacity of the volt seconds provided by center solenoid winding, it is possible to apply hybrid superconducting magnet to the TF coil and CS coil in a low aspect ratio design condition. In this paper, the hybrid magnet winding by using of Nb₃Sn and Bi₂₂₁₂ are designed and detailed analyzed which can be selected as a reference for CFETR´s magnet system design. The high temperature magnet part is Bi2212 conductor, its dimension is 30 mm×35 mm/turn and current density is 117.46 A/mm². The low temperature magnet part is Nb₃Sn conductor which can good work under 11T, its current density is about 80A/mm². In addition, the hybrid superconducting magnet system will be expected to save space for sufficient tritium blanket due to reduced conductor size.