Superconducting Current Pump

A superconducting current pump arranged to cause a DC electrical current to flow through a superconducting circuit accommodated within a cryogenic enclosure of a cryostat comprises a rotor external tothe cryogenic enclosure and a stator within the cryogenic enclosure, the rotor and stator separated by a gap through which passes a thermally insulating wall of the cryogenic enclosure, the rotor andthe stator comprising at least in part a ferromagnetic material to concentrate magnetic flux in a magnetic circuit across the gap between the rotor and the stator and through the wall, so that movement of the rotor external to the cryogenic enclosure relative to the stator within the cryogenic enclosure induces a DC transport current to flow around the superconducting circuit within the cryogenicenclosure. There is no coupling between a drive motor external to the cryogenic enclosure and an internal rotor which may introduce a path for heat leakage into the cryostat, in turn increasing the heat load and thus increasin