International Development of Superconducting Magnets for Fusion Power

In the 10-year-long Large Coil Task, the U.S., EURATOM, Japan and Switzerland separately designed and jointly tested six superconducting toroidal field coils, having 2.5 × 3.5-m bores. Three coils were bath-cooled; three used forced flow. Five used NbTi conductors; one Nb₃Sn. All were fully instrumented. All coils surpassed 8-T design criteria, reaching peak fields of 9.0 T. Tests demonstrated tolerances for internal heating and safety under abnormal conditions (e.g., loss of flow). Data were gained in experiments to extreme conditions. This paper summarizes results, both technical and with regard to successful international collaboration.