2018 年 13 巻 p. 3405027
A Cable-in-conduit (CIC) conductor, in which superconducting wires are multi-stage twisted and inserted into a tube-like conduit, has been developed mainly for fusion magnets. CIC conductors with Nb3Sn wires are primary candidates for the magnets of the next fusion reactors. Since an A15 phase superconductor such as Nb3Sn is brittle, heat treatment for production of the A15 phase must be carried out after manufacturing the conductor. Either the wind and react (WR) or the wind, react, and transfer (WRT) method has been applied for the CIC conductors with Nb3Sn wires in order to prevent degradation of the critical current by excess strain after the heat treatment. The allowable strain after the heat treatment is considered to be 0.2 %. Since the WRT technique has been matured through manufacture of the ITER magnets, adaption of the WRT method to helical coils of an LHD type reactor is studied.
