Development of HTS Conductors for Fusion Magnets

In view of the development of cables for next-generation fusion reactors, research activities are carried out on all HTS materials available from industrial production. Preliminary design of a react and wind cable using Bi-2212 wires is carried out, inspired by the Nb₃Sn cable for European DEMO. The design and construction of a 60-kA prototype cable made of coated conductors have been carried out. The strands in the cable are composed of a stack of coated conductor tapes (4 mm wide) embedded in a copper profile of 6.3 mm in diameter. Tapes and copper profiles are soldered together in order to obtain a mechanically solid strand and to keep the inter tape resistance at a minimum, so that current can be easily redistributed among the tapes in a strand. The strands are fabricated in pieces 2 m long, but scaling up to industrial production should not present any major problem. A flat cable is manufactured by winding 20 strands around a central copper former; the cable will be inserted in a steel jacket for force flow cooling. The critical current of each strand was measured at liquid nitrogen in self-field just after the manufacturing process (twisted and straight) and after cabling: No reduction of the critical current was observed. Two pieces of cable, each 2 m long, are going to be prepared and assembled to form a sample that can be tested in the EDIPO facility.