SUPERCONDUCTIVE CIRCUIT

1,191,446. Superconductor devices. COMMISSARIAT A L'ENERGIE ATOMIQUE. 28 Feb., 1969 [15 March, 1968 (2)], No. 10769/69. Heading H1K. A superconductor circuit, comprising a winding of a tube of superconductor material having an electrically insulating outer sheathing, is completed by electrically joining together the outer surfaces of the ends of the tube where there is no sheathing and leaving inlets and outlets for cooling fluid flowing through the tube independent of one another. As shown, Fig. 1, the circuit comprises a superconductor tube carrying the cooling fluid forming a coil 10 connected to a superconductive switch 16. The outer surfaces of the tubes 19, 21 extending from the switch 16 and the coil 10 respectively are electrically connected together by means of clamp members 20 which surround the tubes at areas free from the outer insulating sheath. The ends 23, 24 of the tubes extend from the clamping members 20 and are connected to a self-contained cryogenic coolant system which pumps liquid helium through the tube. An electrical lead 22 is connected to the clamping members 20 to provide a connection to an external circuit. The tubes 13, 15 at the other ends of the coil 10 and switch 16 are buttjointed and secured by a clamp 14 to which a second lead 17 is connected. The clamping members 20, 14 are covered with a layer of insulating material (not shown). Switch 16 comprises an enlarged diameter tube section surrounded by a coil 18 by means of which a magnetic field can be applied to drive the tube section normal. The insulating sheath provides electrical and thermal isolation and the whole circuit may be mounted in an evacuated container. The superconductor material may be a Nb-Ti or Nb-Zr alloy or may be Nb 3 Sn and the tube may be provided with a liner of high thermal conductivity metal such as copper. The liner may comprise a tube, Fig. 2 (not shown), or a solid core having a plurality of bores for the coolant, Fig. 4 (not shown). A further layer of high thermal conductivity metal may be inserted between the superconductor tube and the insulating sheath, Fig. 3 (not shown), and the superconductor tube itself may comprise alternate layers of superconductor material and high conductivity metal. The superconductor may be applied to the liner by codrawing, evaporation in vacuo, cathode sputtering, plasma spraying, or by electrolytic or chemical deposition. The clamping members may be of copper and may be further supported by a stainless steel fit