The superconducting winding comprises a rotor which may rotate about a rotation axis with a superconducting winding in a thermally conducting winding support. The winding support comprises a central coolant cavity, with a lateral cavity leading out of the winding support connected thereto. A cold head of a refrigeration unit is connected to a condenser unit for condensing refrigerant and is arranged outside the rotor. A fixed heat tube, supplying the refrigerant, is coupled to the condenser unit, extending axially into the rotating lateral cavity and is sealed relative to the cavity. The refrigerant is a mixture of several components having different condensation temperatures.