Thermonuclear device

In a plasma position stabilizing shell used for a tokamak type thermonuclear device, a conventional shell has to be designed as a split type in view of the requirement for plasma breakdown and plasma current rising. Accordingly, the time constant of the shell is limited and the plasma position stability is also restricted. In view of the above, a shell made of oxide superconductors and a device for controlling the shell temperature are disposed along a vacuum container surrounding the plasmas. By controlling the shell temperature to higher than the critical temperature upon plasma breakdown or plasma current rising, a sufficiently high resistance can be obtained. Further, by lowering the temperature to less than the critical temperature when the plasma current is stabilized, it can stabilize plasma as a shell of infinite time constant. Thus, it is possible to provide an effective shell giving no undesired effects on plasma breakdown and plasma current rising. (N.H.)