World’s largest nuclear reactor gets 3,000-ton magnet core for 10x energy output

Today, the International Thermonuclear Experimental Reactor (ITER) announced the completion of all components for its pulsed superconducting electromagnet system. 

This intricate network of magnets, the largest and most powerful ever assembled, will serve as the “electromagnetic heart” of ITER’s fusion reactor, a donut-shaped device known as a Tokamak.

“The final component was the sixth module of the Central Solenoid, built and tested in the United States,” said the ITER.

“When it is assembled at the ITER site in Southern France, the Central Solenoid will be the system’s most powerful magnet, strong enough to lift an aircraft carrier.”

Critical role in fusion process

This crucial component was built and rigorously tested in the United States before its shipment to the ITER site in Southern France.

When fully assembled, this pulsed magnet system will weigh a staggering 3,000 tons and “will work in tandem with six ring-shaped Poloidal Field (PF) magnets, built and delivered by Russia, Europe, and China.”

These superconducting magnets will perform a critical role in the fusion process, i.e., initiating and confining a superheated plasma within the Tokamak.

ITER Director-General Pietro Barabaschi hailed this achievement: “What makes ITER unique is not only its technical complexity but the framework of international cooperation that has sustained it through changing political landscapes.”

“This achievement proves that when humanity faces existential challenges like climate change and energy security, we can overcome national differences to advance solutions.”

The “heart” will function in systematic manner

The process begins with injecting a few grams of hydrogen fuel – deuterium and tritium gas – into ITER’s massive Tokamak chamber. The powerful pulsed magnet system then kicks in and sends an electrical current that ionizes the hydrogen gas, transforming it into a plasma.

This is where the “invisible cage” comes into play. The magnets generate intense magnetic fields that confine and shape this ionized plasma, preventing it from touching the reactor’s walls. 

External heating systems then raise the plasma’s temperature to 150 million degrees Celsius, ten times hotter than the sun’s core. 

“At this temperature, the atomic nuclei of plasma particles combine and fuse, releasing massive heat energy,” explained the ITER in a press release.

ITER has been designed to demonstrate fusion power’s scientific and technological feasibility. At full operational capacity, the experiment is projected to produce 500 megawatts of fusion power from a mere 50 megawatts of input heating power – a tenfold energy gain. 

“At this efficiency level, the fusion reaction largely self-heats, becoming a ‘burning plasma,” added the press release.

A global effort toward fusion energy

ITER is an international collaboration involving more than 30 countries. Under this project, seven ITER members contributed significantly through the in-kind provision of crucial components. 

For instance, the United States built the Central Solenoid, while Russia delivered a large Poloidal Field magnet and superconductors. Europe manufactured several Poloidal Field magnets and Toroidal Field coils, creating a significant portion of the vacuum vessel. 

China contributed a Poloidal Field magnet, superconducting materials, and the Correction Coils and Magnet Feeders. Japan produced key components for the Central Solenoid and several Toroidal Field magnets. Korea manufactured vacuum vessel sectors and thermal shields. 

Meanwhile, India fabricated the massive Cryostat, the “thermos” that houses the ITER Tokamak.

Ahead of schedule

This latest milestone follows significant progress in ITER’s construction. In 2024, the project achieved 100 percent of its construction targets. Just this month, in April 2025, the first vacuum vessel sector module was successfully inserted into the Tokamak Pit, ahead of schedule, which marked the beginning of the reactor’s assembly phase.

Completing the Central Solenoid and the entire pulsed superconducting electromagnet system represents a major leap forward for ITER and the future of clean energy.

“The ITER Project is the embodiment of hope. With ITER, we show that a sustainable energy future and a peaceful path forward are possible,” concluded Barabaschi.