A review of conductor development for large fusion magnets

This paper is a survey of the development progress towards high-field, high-current superconducting conductors suitable for the next experimental fusion machines. The reference is the International Thermonuclear Experimental Reactor, ITER a world-wide project presently in the Engineering Design Activity Phase. The main conclusions are that the available Nb₃Sn strand is not far from the ITER specifications, the feasibility of the cabling procedure has been demonstrated, suitable jacket materials have been identified, and the pull-through draw-down jacketing technique has been successfully applied to significant lengths of subsize conductor. R&D-activity is required to upgrade the background knowledge to the level necessary for the fabrication of the long-length, full-size ITER conductors. Qualification of welding procedures for Incoloy 908 is required. Further investigation has to be made on the effect of chromium plating on the RRR of the strands and on the transverse resistivity of the cable vs void fraction and/or transverse loads