Research and engineering design work of superconducting magnet system of CFETR (China Fusion Engineering Test Reactor) is in progress and supported by China government. The major radius and minor radius of CFETR is designed as 7.2 m and 2.2 m, respectively.
For one hands, such big size will bring big challenges to the magnet system because it will be difficult to get high enough volt seconds and magnetic field in plasma center. For another hands, high voltage seconds generated by central solenoid coils and high magnetic field provided by toroidal field coils are required to get high performance plasma with current of 10-14 MA. Therefore, to generate high enough magnetic field of 6.5 T field at R= 7.2m, the peak field at TF coils will reach to 14.3 T. The big challenge will be the enough stability margin and enough temperature margin of the high-Jc NB3Sn CIC (cable-in conduit) conductor.
Besides, China government support new funding ($600 Million) to design and manufacture a TF prototype coil since from 2019. Although the engineering design work goes smoothly in now stage, it is still big challenge to get high enough stability margin of the TF coil under the condition of peak field of 14.3 T. Besides, the peak stress of the TF coil will be about 700MPa. The new design of high Jc Nb3Sn conductor and structure of TF prototype coil will be detailed introduced.
In addition, the eight CS coils with HTS insert coil which can reach to peak filed of 17 T are investigated which can provide a high voltage second of 480V•s in the plasma region. The poloidal field coils are far away from plasma, so the big overturning moment generated by PF coils is a big challenge for snowflake plasma equilibrium configuration. It hopes that the presentation can not only be good reference for other DEMO projects, but also a good bridge for the broad international cooperation for fusion research work.