Insulated transmission line for cryogenic media

Insulated transmission line for the transfer of cryogenic media, comprising:

• a tubular heat shield, including at least three concentric, radially separated, corrugated metallic tubular members, that provides a first annular space between two of said tubular members wherein a multiple layer, fibrous insulating material is disposed under vacuum conditions;
• a second annular space between two of said tubular members, including the innermost of said tubular members, having disposed therein a liquid or gaseous cooling madia;
• and a vacuum sealed, inner tubular space formed by said innermost tubular member;
• the improvement comprising:
• first and second longitudinally seam welded, corrugated metal pipes extending through said vacuum sealed, inner tubular space;
• and
• first insulating spacer means positioned about said first metal pipe and at least partially between said first and second metal pipes for maintaining a spacial separation and minimum heat conductance between said metal pipes throughout their respective axial lengths, and second insulating spacer means positioned about at least said second metal pipe and between said metal pipe and said innermost tubular member for maintaining spacial separation and minimum heat conductance between said metal pipe and said innermost tubular member throughout their respective axial lengths.