High temperature superconducting current leads for cryogenic apparatus

The use of high-temperature superconductors (HTSC) for cryostat current leads is analyzed for operation between liquid helium and liquid nitrogen temperatures in the conduction-cooled and vapor-cooled cases. Existing fabrication methods are sufficient to produce such leads for most known applications. Thermophysical data suggest that performance of HTSC leads operated in the normal state is nearly as good as that of pure metal leads. If leads of HTSC are optimized for the normal state and then operated in the superconducting state, helium boil-off can be reduced by about a factor of two. For leads longer than the normal-state optimum, the helium boil-off can be reduced further, but the system must be guarded against thermal runaway