Protection device for poroidal coils in vacuum vessel

Purpose: To suppress the temperature increase and thereby protect a poroidal coil protection tube against the damages by disposing a plurality of elongate liners around the outer circumference of the protection tube. Constitution: The portion of poroidal coils situated within a vacuum vessel is covered by way of heat insulating material with a protection tube consisting of a thick wall portion and a bellows portion. A plurality of elongate liners are disposed with a predetermined pitch around the outer circumference of the protection tube in perpendicular to the moving direction of the bellows portion and fixed to the thick wall portion of the protection tube by means of bolts. Thus, radiation heat entered through the gaps between the liners is applied only to a part of the bellows portion whereby the temperature increase is suppressed. Furthermore, since the liners are supported at the thick wall portion of the protection tube, heat entered from the plasmas is not transmitted to the vacuum vessel. Accordingly, the thermal stresses in the bellows portion can be decreased to prevent the damages. (Kawakami, Y.)