Techno-Economic Optimization of the NbTi DTT Feeders

The superconducting (SC) coils of the Divertor Tokamak Test (DTT) facility will be connected to the current leads by a set of SC feeders, currently designed as cable-in-conduit conductors wound using commercial NbTi strands to be cooled by Supercritical Helium at 4.5 K. The feeders are immersed in the magnetic field generated by the SC coil and plasma outside of magnet system, so that the maximum field on the most loaded feeder can reach 4 T at the full rated current (including the self-field effect). Here the performance of the feeder conductors is assessed during a plasma pulse, based on the DTT standard text single-null operating scenario, for the most loaded feeder of the Central Solenoid and of the Toroidal and Poloidal Field coils, computing the minimum temperature margin to current sharing throughout the plasma scenario. Several alternative cabling configurations are analyzed, designed to withstand the nominal current at the peak field with a different number of SC and stabilizer strands. The minimum temperature margin is evaluated as a function of the material, manufacturing and operational costs of the different alternative feeder layouts. Based on such techno-economical characterization, the optimal (cheapest) design of the feeder cables is identified.