Long removable cryogenic transfer lines

Easily removable cryogenic transfer lines of lengths up to 63 feet have been successfully constructed and operated at the National Superconducting Cyclotron Laboratory. For the initial testing phase of the K-800 superconducting magnet, temporary lines which span a rather long distance between coil cryostat and a helium refrigerator were built. Eventually, a low heat load cryogenic distribution system will be constructed. The differential contraction between the cold inner pipe and ambient temperature outside vacuum jacket presents design problems for stainless steel bayonet transfer lines. The traditional solution to the contraction problems, contraction loops or bellows, usually results in a fixed line. Using the alloy Invar 36, which has a contraction coefficient about 1/8 of stainless steel, simple bayonet type transfer lines have been built. A lifting fixture is used for line installation