The United States has completed its delivery of the final component for the ITER Central Solenoid, the powerful magnet at the core of the world's largest fusion experiment. The last of six modules, manufactured by General Atomics in San Diego, arrived at the ITER site in southern France in May 2024. This delivery marks the culmination of a multi-year, US-led effort to build the 1,000-ton magnet system. The Central Solenoid is a critical component of the ITER tokamak, designed to induce a powerful current within the plasma, initiating its formation and providing essential heating and stability. Its completion and delivery represent a significant hardware milestone for the international collaboration, moving the project closer to assembly and eventual first plasma operations. Source: Oak Ridge National Laboratory
Dubbed the 'beating heart' of the machine, the Central Solenoid is a stacked series of six superconducting magnet modules that form a cylindrical structure 18 meters tall and 4.25 meters in diameter. When fully assembled and energized, it will be the most powerful pulsed superconducting magnet ever constructed. The system is designed to ramp up to a peak magnetic field of 13 tesla and drive 15 million amperes of current in the ITER plasma. Its stored magnetic energy will reach 5.5 gigajoules. The magnet's immense strength is necessary to contain and shape the 150-million-degree Celsius D-T plasma within the tokamak vacuum vessel, a fundamental requirement for achieving sustained fusion reactions. Source: Oak Ridge National Laboratory
When fully assembled and energized, it will be the most powerful pulsed superconducting magnet ever constructed.
The fabrication of the Central Solenoid modules was a complex undertaking managed by US ITER, a project office at Oak Ridge National Laboratory. Each module contains approximately 5.6 kilometers of niobium-tin (Nb3Sn) superconducting cable, which must be precisely wound and then heat-treated in a multi-week process to create its superconducting properties. Following fabrication at General Atomics, the modules underwent rigorous testing at cryogenic temperatures to verify their performance before being shipped to France. This extensive manufacturing and qualification process underscores the engineering challenges inherent in building magnets of this scale and power, a key area of focus for both public and private fusion development efforts. Source: Oak Ridge National Laboratory
With all six modules now on site, ITER engineers will begin the intricate process of assembling the Central Solenoid stack. The modules will be carefully lowered into the central pit of the tokamak complex and integrated with the surrounding machine structures, including the toroidal field coils and vacuum vessel sectors. This assembly phase is a critical path item in the overall project timeline. The successful operation of the Central Solenoid is a prerequisite for achieving the project's primary scientific goal: producing 500 MW of fusion power from a 50 MW input, for a plasma energy gain (Q_plasma) of 10. The performance of this magnet will be a key indicator of the viability of the tokamak approach at reactor scale. Source: Oak Ridge National Laboratory