Most efforts towards fusion power rely on magnetic confinement with tokamaks and ITER is the latest such device in construction. It is planned to be followed with demonstration power plants before the final achievement of commercial fusion power.
The Breeder Blanket is the most critical and complicated component of a fusion reactor because of the dual functions of heat extraction and tritium breeding.
The divertor is the device which implements the exhaust of the plasma at the end on a confinement cycle. The limiter scraps the edge off the plasma in disruptions. These components have the highest radiation damage in the tokamak.
Superconducting magnets are the core enabling technology for magnetic confinement fusion reactors. The reliability of the magnets is essential for the operation of a fusion power plant.