Design and fabrication of a dumbbell-shaped poloidal magnetic coil

In the nuclear fusion devices of magnetic field containment type, for the generation and heating of plasma, the excitation of plasma current, the maintenance of equilibrium and stability of plasma and so on, various magnetic coils to meet respective objectives have been developed. In TPE-2, a toroidal screw pinch device, toroidal coils, poloidal coils and vertical magnetic field coils are provided to form the tokamak type magnetic field configuration. The poloidal coil is to excite plasma current, and corresponds to the primary winding of an air core current transformer, while plasma corresponds to the secondary winding of one turn. It was necessary to develop a new large poloidal coil to overcome the defects of conventional coils and to be suitable to the TPE-2. In this paper, the form and performance of this new poloidal coil are described, and the methods of its design and manufacture, and the comparison of its measured data with the design data are reported. The new coil is an air core helical coil of one turn, of which the length is 4 m, and the weight is about 6 t. The features of this coil are no effect of magnetic field disturbance, small leaking flux and high energy efficiency. (Kako, I.)