Long flexible transfer lines for gaseous and liquid helium

Screened flexible four-fold coaxial transfer lines for gaseous and liquid helium with lengths of 5 to 50 m have been successfully built and tested. The lines for gaseous helium have to supply and return a mass flow of 5 to 10 g s−1 at temperatures ranging between 350 and 20 K for cooldown or warmup of superconducting magnets. The lines for liquid helium have to supply up to 100 ℓ h−1 for final cooldown or up to 25 ℓ h−1 for normal operation of superconducting magnets. The hydrodynamic and thermal performance characteristics of the lines have been measured. The results are encouraging and it can be envisaged to use this kind of lines for superconducting magnets in high energy accelerators.