the most powerful magnet in the world will soon arrive in France

American engineers are preparing to ship the first part of the largest and most powerful pulsed electromagnet ever to France. Once assembled, the structure will power the core of the world’s largest fusion reactor, ITER.

Currently, 35 countries are working together on a project called ITER (“the way”, in Latin). The idea: to build a gigantic nuclear fusion reactor. This one will see the light of day in Saint-Paul-lès-Durance, in the Bouches-du-Rhône.

The Vinci company has been busy in recent years building the structure of the reactor. This site is now complete, the assembly of the reactor itself was able to begin last July and is still ongoing. In a few weeks, one of the centerpieces of this incredible structure will arrive on site.

The pulsating heart of the reactor

Indeed, engineers from the American company General Atomics are preparing to ship the first of the six parts of the central solenoid, the electromagnet most powerful ever built.

This module will soon reach the Port of Houston from San Diego via a massive 24-axle tractor. From there, it will be shipped by ship to Marseille in early July, with an expected arrival at the end of August. It is then sent to the ITER facility. The same goes for the five remaining modules. These will be realized in the coming years.

When assembled, this central magnet will be 18 meters high and 4.3 meters wide, weigh about 1000 tons on the scale and can produce a magnetic field of 13 Tesla.

Each of these individual modules is essentially a huge coil containing more than five kilometers of superconducting cable in niobium. Each structure is then treated in a large oven for several weeks to further increase conductivity, after which the cables are insulated and the coil is wound into its final shape.

We know from Faraday’s law of induction that electricity passing through a wire generates a magnetic field that is perpendicular to that wire. When this wire is wound, does the electric current produce a circular magnetic field. In this central solenoid, each coil will be responsible for amplifying the strength of the magnetic field, sufficient to control of unstable reagents of nuclear fusion.

iter magnet
A diagram of the ITER reactor with the central solenoid in the center and the plasma in the chamber. Credit: ITER

Plasma control

To master nuclear fusion – at work in the hearts of stars – engineers are developing reactors called tokamaks, in which they heat deuterium and tritium to more than 100 million degrees Celsius until they form a cloud of plasma. At this temperature, the atoms undergo a fusion that releases large amounts of energy, which can be used to generate electricity.

In contrast, for nuclear fusion to be a viable option, this reaction must be kept at a constant rate. This is where the central solenoid comes into play, it is indeed the powerful magnetic field that will sustain the plasma in the tokamak.

As for the whole project, construction of ITER is still expected to be completed by 2025, despite the impact of the pandemic. The project will then be at full capacity by 2035, producing approximately 500 megawatts of thermal energy, enough to power 200,000 households. As a reminder, this is just an experimental project that should lay the groundwork for future fusion reactors, each capable of powering several million households.