Abstract: A superconducting power transmission line is comprised of sections of rigid cryogenic envelope and sections of flexible cryogenic envelope. The rigid sections are comprised of rigid inner and outer tubes having a refrigeration shield located in a vacuum chamber therebetween. The flexible sections are comprised of flexible inner and outer tubes surrounded by reinforcing braid. The rigid and flexible inner and outer tubes are joined together and a refrigeration tube which is in contact with the rigid section's shield is coiled about the inner flexible tube.

Abstract: An elongated cryogenic envelope including an outer tube and an inner tube coaxially spaced within said inner tube so that the space therebetween forms a vacuum chamber for holding a vacuum. The inner and outer tubes are provided with means for expanding or contracting during thermal changes. A shield is located in the vacuum chamber intermediate the inner and outer tubes; and, a refrigeration tube for directing refrigeration to the shield is coiled about at least a portion of the inner tube within the vacuum chamber to permit the refrigeration tube to expand or contract along its length during thermal changes within said vacuum chamber.