Preliminary design of a US ITER model poloidal coil

A preliminary design of a central solenoid model coil for ITER (International Thermonuclear Experimental Reactor) has been made. The preliminary conductor and coil design described should achieve the model coil performance requirements with minimum cost and maximum reliability. The design is based on a Nb₃Sn cable-in-conduit conductor incorporating a conduit made from the new superalloy Incoloy 908. This alloy has excellent mechanical properties and a COE (cost of electricity) well matched to the COE of the superconducting wire. Major advantages in coil performance result, due to reduction of the thermal strain-induced degradation of the critical properties of the Nb₃ Sn superconductor. The principal performance advantages include higher critical current density and higher critical temperature, particularly at high fields, which results in increased operating margins of critical current and stability. A prediction of enhanced operating performance is made relative to conductor designs by other ITER parties which rely on conduits made from austenitic stainless steels with relatively high coefficients of thermal expansion