STABILIZED SUPERCONDUCTOR

1383889 Super-conductors BBC BROWN BOVERI & CO Ltd 20 July 1973 [20 July 1972] 34669/73 Headings H1A A5 A3M and A4D An electrically poorly conductive layer is formed around each filament 2 of a multi-filament super-conducting cable by heating so that the material of an electrically highly conductive matrix carrying the filaments interdiffuses with either the super-conductor itself or with another electrically conductive material surrounding the filaments 2 to form the relatively poorly conductive layer. In a simple embodiment NbTi rods are inserted in a Cu sheath and drawn to form a wire, many of which are stranded together and rolled to form a cable of NbTi filaments in a Cu matrix. The cable is then heated to a temperature which causes a highly resistive layer of CuTi to form round each filament. In the embodiment shown in Fig. 2, NbTi filaments 2 are surrounded by Cu4, Zn 5 and a Cu matrix, and on heating a relatively resistive Cu-Zn layer forms round each filament. In a third embodiment the filaments are surrounded with Al which, on heating, combines with oxygen released from the highly conductive matrix to form insulating aluminium oxide.