The final module of the Central Solenoid has been installed within the cryostat at the ITER experimental fusion facility in southern France, marking the completion of the most powerful magnet ever constructed. This 1,000-ton superconducting magnet, standing 18 meters tall, is the central component of the ITER tokamak's magnetic confinement system. Its primary function is to induce a powerful current within the D-T plasma, providing the initial heating and confinement necessary to begin the fusion reaction. The assembly's completion represents a significant hardware milestone for the international project, which aims to demonstrate the scientific and technological feasibility of fusion energy. Source: Oak Ridge (ORNL)

Manufactured by General Atomics in California and shipped to France in six modules, the Central Solenoid is a feat of materials science and engineering. It is wound with 43 kilometers of niobium-tin (Nb3Sn) superconducting cable, which will be cooled to 4 Kelvin to achieve its operational state. At peak performance, the magnet will generate a magnetic field of 13 Tesla and store 5.5 gigajoules of energy. This immense magnetic force is essential for driving the plasma current required to heat the fuel to temperatures exceeding 150 million degrees Celsius. The successful fabrication and now complete assembly of this 'heart' of the reactor is a critical step on the path to first plasma. Source: Oak Ridge (ORNL)

Manufactured by General Atomics in California and shipped to France in six modules, the Central Solenoid is a feat of materials science and engineering.

The Central Solenoid operates as the primary winding of a massive transformer, with the plasma itself acting as the secondary winding. By rapidly changing the current in its coils, it induces a large electromotive force that drives millions of amperes of current through the plasma. This ohmic heating is the first stage of reaching fusion conditions, with subsequent heating provided by neutral beam injection and radio-frequency waves. The successful operation of this component is non-negotiable for achieving ITER's primary scientific goal: producing 500 MW of fusion power from 50 MW of input heating power, for a plasma energy gain factor (Q) of 10. Source: Oak Ridge (ORNL)

This milestone for the public-sector ITER project occurs amidst a dynamic period in the private fusion industry, where companies are pursuing smaller, often faster-paced, device development cycles. While many private designs also rely on powerful superconducting magnets, the scale and integrated complexity of the ITER Central Solenoid are unparalleled. Its construction has provided invaluable manufacturing experience and supply chain development for high-field niobium-tin magnets, data that informs both public and private efforts. The project's progress, though subject to schedule revisions, continues to serve as a key benchmark for large-scale fusion engineering and international scientific collaboration. Source: Oak Ridge (ORNL)

With the Central Solenoid now fully assembled inside the tokamak pit, the next phases of the ITER project will focus on the installation of the remaining toroidal and poloidal field coils, vacuum vessel sectors, and diagnostic systems. The integration of these complex, multi-ton components requires precision engineering and coordination among the project's international partners. The successful commissioning and eventual operation of the complete magnet system will be the ultimate test of the design and manufacturing processes. Observers will be watching for subsequent announcements regarding the vacuum vessel closure and the integrated testing schedule as key indicators of progress toward first plasma. Source: Oak Ridge (ORNL)