Innovative application of a magnet system to fusion power

Strong-field tokamaks with high plasma current are attractive in raising the plasma performance of devices with small sizes. However, the coil-support structures become more demanding in order to withstand the stronger electromagnetic forces. In this paper, a new concept of a high field tokamak reactor is proposed. High magnetic field is generated using the force-balanced coil (FBC) system, that can reduce the huge electromagnetic force of coils by balancing the poloidal and toroidal magnetic field strengths. The poloidal-toroidal hybrid coil is wound in a multi-helical structure with varying pitch angle windings. A small size superconductor torus with the FBC system has thus been constructed to demonstrate proof of principle. A special operation scenario, owing to FBCs helical tokamak, is also demonstrated by realisation of the tokamak plasma. Future plans are reported.