Thermonuclear device

Not uniform magnetic fields in a thermonuclear device give a significantly disadvantageous effect on the plasma confinement. Only the structural counter measure can not avoid the generation of the non-uniform magnetic fields since the size of the portion for passing electric current has a limit, and the efect is reduced as the size of the device is enlarged and the amount of current is increased. It is intended by the present invention to eliminate the undesired effect of non-uniform magnetic fields on the plasmas by surrounding the lead portion and the transfer portion of the coils as a not-uniform magnetic field generation source with superconductive sealing materials. The superconductive materials have a complete conductivity and complete antimagnetism when they are in the superconductive state. Therefore, the non-uniform magnetic fields can completely be shielded. Accordingly, it is possible to obtain a thermonuclear device with satisfactory plasma confining performance. (K.M.)