Fabrication of the Superconductor for the DPC-TJ Coil

A forced-cooled superconducting coil (DPC-TJ) was wound with a double walled cable-in-conduit named as “Preformed Armor Type CICC.” In this paper, we describe the fabrication of the conductor for the DPC-TJ coil with the first conduit which plays a role of sealing the supercritical helium from the vacuum. Because the DPC-TJ coil has high average current density of 40A/mm2 (12T, 4.2K) in winding area, the (NbTi)3Sn strand by Nb tube method was selected, which has a very high critical current density in non Cu area. As a result of development work, the strand could be fabricated which meet the following requirements; the critical current density of more than 600A/mm2 at 12T and the RRR (Residual Resistivity Ratio) value of higher than 50. The fabrication line of the cables-in-conduit conductors by roll forming method was also developed. Through the fabrication of the conductor for the DPC-TJ coil, it was demonstrated that large and long conductors for future fusion reactor could be fabricated.