Development of an indirectly cooled superconductor for the LHD fusion reactor FFHR

A 100-kA indirectly cooled superconductor has been designed and optimized for the heliotron fusion power reactor FFHR. A doubly transposed Rutherford cable composed of 216 Nb3Sn superconducting wires is embedded in an aluminum-alloy jacket with a high filling factor. Additional high purity aluminum strips around the cable reduce the hotspot temperature to 150 K. The final design has a rectangular cross section that is 100mm wide and 25mm high, which will achieve an operating current of 100 kA at a current density of 40A/mm2. A prototype of the conductor was developed to demonstrate the fabrication process. The prototype has the same configuration as the design, except that the aluminum strips are eliminated. © 2014 The Japan Society of Plasma Science and Nuclear Fusion Research.