FABRICATION OF SUPERCONDUCTOR FOR THE DPC-TJ COIL

A forced cooled superconducting coil (DPC-TJ) was wound with a double walled cable-in-conduit referred to as preformed-armour type C ICC. In this paper, we describe the fabrication of the conductor for the DPC-TJ coil with the first conduit, which plays a role in sealing the supercritical helium from the vacuum. Because the DPC-TJ coil has a high average current density of 40 A mm-2 (12 T, 4.2 K) in the winding area, an (NbTi)3Sn strand formed by the Nb tube method was selected, which has a very high critical current density in the non-Cu area. As a result of development work, a strand could be fabricated which met the following requirements: critical current density > 600 A mm-2 at 12 T and residual resistivity ratio (RRR) value > 50. A fabrication line for the cable-in-conduit conductors using the roll-forming method was also developed. Through fabrication of the conductor for the DPC-TJ coil, it was demonstrated that large and long conductors could be fabricated for future fusion reactors.