PURPOSE: To reduce the loss of refrigerant as well as to improve the efficiency of the titled coil by a method wherein the adjoining vessels are connected using an interconnecting tube for the purpose of filling up the vessels with refrigerant, and the superconductive lead-out wire coming from the superconductive coils adjoiningly positioned in the interconnecting tube is arranged in connected manner.

CONSTITUTION: An interconnecting tube 6 passing through the vessel wall of the adjoining vessels 2 is provided at the arbitrary position located on the lower side above the lowest limit of the surface of the refrigerant filled in the vessels 2, the lead-out wire 3 of a superconductive coil 1 is brought in said interconnecting tube 6 and the connected part 5 of the lead-out wire 3 coming from the adjoining superconductive coil 1 is provided in the midway of the lead-out wire 3. This lead-out wire 3 consists of a superconductive material, and it is cooled by the refrigerant contained in the vessels 2, thereby enabling to maintain the superconductive condition at all times. Accordingly, Joule heat is generated only by the connection resistance of the connected part 5, and when the Joule heat is maintained at 1×10-9Ω and current used is 20kA, a low value of 0.4W is obtained, thereby enabling to cut down 0.5W1% from the conventional system. Besides, as the lead-out hole requires a power lead and a vacuum seal can be unnecessitated, it contributes for increase in economical effciency.