Dispositif supraconducteur

1126404 Making super-conductors; extruding IMPERIAL METAL INDUSTRIES (KYNOCH) Ltd 2 May 1967 [20 May 1966] 22581/66 Headings H1A and A4D A tubular super-conductor arrangement comprises one or more elongate elements which are super-conductive below a predetermined temperature at least partially embedded in a matrix of material non-super-conducting at that temperature. Typically the super-conductor elements are of niobium-titanium, niobium-zirconium or niobium tin and the matrix of copper, aluminium, silver, lead or solder. An exemplary arrangement is made as follows: A bar of niobium-titanium alloy formed by swaging, rod rolling or forging an ingot is sealed inside an evacuated copper tube and the assembly extruded at 300-450‹C and then drawn to form a rod. A number of such rods are then packed and sealed in the annular space between coaxial copper tubes and the assembly extruded at 150-450‹C. The resulting assembly is drawn using a floating plug technique, and finally without a plug to form a tube with a corrugated inner wall as shown in Fig. 5. The corrugations facilitate cooling in operation by pumping liquid or gaseous helium along the tube. In an alternative method superconductor material is packed in the annular space instead of the embedded rods to give the arrangement of Fig. 6 (not shown). Rectangular or hexagonal cross-sections tubes are also envisaged. Where Nb 3 Sn is to be used as super-conductor the procedure is to fill niobium tubes with tin and pack these in the copper tube in the first stage of the above described process. On completion of the assembly it is heated for 10 minutes to 3 hours at 100-950‹C to cause the niobium and tin to react to form the compound.