HYBRID VAPOR COOLED POWER LEAD FOR CRYOSTAT

A power lead for a cryostat has high temperature superconducting (HTSC) conductors extending inward toward a pool of liquid cryogen in the cryostat in series with normal conductors extending from the HTSC conductors to outside the cryostat. Tubular shrouds vented to atmosphere direct a flow of cryogen vapor along the HTSC conductors to maintain them superconducting, and along the normal conductors to remove Joule heat and heat leakage along the normal conductors. In one embodiment, a pool of liquid nitrogen maintained within a tubular inner shroud is the principal coolant for the normal conductors. Helium vapor is circulated over the HTSC conductors and is then directed by an outer tubular shroud around the inner tubular shroud to provide additional cooling for the normal conductors. Flexible connectors at one end of each of the HTSC conductors accommodate for individual thermal contractions of these conductors.