Protection device for a thermonuclear device

Purpose: To prevent the damage in a vacuum vessel or the likes upon plasma abnormality by decreasing the mechanical stresses such as turning or shearing forces exerting on the vacuum vessel. Constitution: The apparatus comprises a current detector for detecting a saddle type current containing components flowing in the circumferential direction of the wall of the container in adjacent with the high resistance members, coils disposed in adjacent with the container walls on both sides of the high resistance members respectively and formed such that the current in the direction adverse to that of the saddle type current is supplied, and a coil exciting power source is provided for supplying the same current as the saddle type current detected by the current detector in the opposite directions. The apparatus having such a structure can off-set the saddle-current components flowing in the direction that cause turning force or shearing force in an equivalent manner. (Aizawa, K.)