Abstract: In a superconductive coil assembly, superconductive wires are extended in a sheath tube which also defines a passage for allowing a liquid helium to pass therethrough. Sheath tube is housed in reinforcing vessel which comprises a pair of vessel segments and welded to each other. Reinforcing vessel is enclosed by a turn insulation and a earth insulation.

Abstract: A pair of flanges are fixed to a pipe end of a port of a plasma vacuum vessel and another pipe end to be connected thereto. These flanges each have a ring-shaped knife edge. A copper gasket is interposed between the respective knife edges of the two flanges. A predetermined number of bolts are tightened to fix the flanges to each other. As a result, the knife edges bite into the copper gasket, and a linear sealing load from the knife edges acts on the gasket, thereby sealing and isolating the space inside the port from the outside. The number n of bolts are given by3(B+28)/65-0.ltoreq.n.ltoreq.3(B+28)/65+0.02B,and the flange thickness t is given by ##EQU1## where B is the diameter of a circle passing through the respective central axes of the n number of bolts. Thus, the bolt number and the flange thickness are reduced without lowering the sealing performance.