Abstract: An adiabatic expansion apparatus 22 with a built-in turbine impeller 12 adiabatically expands gas at a cryogenic temperature when the impeller rotates. A control device 24 is connected coaxially with the turbine impeller to control the impeller. A variable nozzle mechanism 30 is provided for varying the throat area for the gas at a cryogenic temperature to be introduced into the turbine impeller. The adiabatic expansion apparatus is installed in a vacuum vessel 14, and a control device is disposed outside the vacuum vessel. The variable nozzle mechanism comprises a nozzle component 32 built into the adiabatic expansion apparatus, and a driving component 34 installed outside the vacuum vessel. The nozzle component and the driving component are connected to the turbine impeller with a coaxial, thin cylindrical component 36, and drive the nozzle component when the cylindrical component rotates about the axis Z of the turbine impeller.

Abstract: There is provided a forced-cooled superconductor including a conduit and a plurality of superconducting strands disposed within the conduit in spaced relationship. A coolant passes through the spaces between the strands for cooling the conduit and strands. The conduit and strands are further cooled by means of an additional separate cooling channel which cooperates with the coolant for cooling the conduit and strands.