Is it possible to mimic the energy-producing process in the Sun and stars and obtain a safe, clean, and possibly unlimited energy source? In order to take an ambitious step towards the development of nuclear fusion technology, a few years ago the ITER ( International Thermonuclear Experimental Reactor ) project was launched, a collaboration between 35 countries in the world that is building in France more tokamak reactor biggest in the world.
ITER aspires to be the first nuclear fusion device that produces more energy than is needed to start the reactions – this is one of the many pitfalls for the development of fusion technology – in addition to serving as a prototype for the future commercial reactors.
Despite the challenges inherent in the year of COVID-19, the construction of ITER is progressing at a good pace and for months, unique components that will be part of this colossal piece of engineering have begun to arrive in France, from the different participating countries. Among them, the central solenoid, which will be sent by the American company General Atomics and will be, not only the most powerful magnet in ITER, but in the whole world.
Why is a giant magnet needed?
The ITER reactor will be based on magnetic confinement, which consists of creating vacuum conditions to contain the plasma by generating a donut-shaped magnetic field – toroidal-. The tokamak is the most popular structure design for this magnetic field.
When fully assembled, the center solenoid will measure 18 meters high, 4.25 wide and weigh 1,000 tons. Its magnetic force could be capable of lifting, according to its creators, a two meter aircraft carrier, and at its core a magnetic field strength of thirteen tesla will be reached, approximately 280,000 times stronger than the Earth’s magnetic field. In addition, the support structures for the center solenoid must withstand forces equal to twice the thrust of a space shuttle lift-off. In this way, the central solenoid will induce a huge current in the plasma and help control the nuclear fusion reaction.
Earlier this year, General Atomics completed final testing of the first center solenoid module and last week it was loaded onto a special heavy duty truck for shipment to Houston, where it will be placed on an ocean vessel for shipment south of France.
The center solenoid in context
Creating magnetic fields in a tokamak requires three different arrays of magnets. The outer coils around the ring of the tokamak produce the toroidal magnetic field, which confines the plasma within the vessel. The poloidal coils, a set of stacked rings that orbit the tokamak parallel to its circumference, control the position and shape of the plasma.
In the center of the tokamak, the center solenoid uses a pulse of energy to generate a powerful toroidal current in the plasma flowing around the torus. The movement of ions with this current creates in turn a second poleidal magnetic field that improves the confinement of the plasma, in addition to generating heat for fusion. At fifteen million amps, the ITER plasma current will be far more powerful than anything possible in today’s tokamaks. The superconducting material used in ITER magnets has been produced in nine factories in six countries. The 43 kilometers of niobium tin superconductor for the central solenoid have been manufactured in Japan. Together, the ITER magnets create an invisible cage for the plasma that precisely conforms to the metal walls of the tokamak.
” The ITER project is the most complex scientific collaboration in history, ” says Dr. Bernard Bigot, Director General of the ITER Organization. “Leading companies like General Atomics are manufacturing world-class components on three continents over a period of nearly ten years. Each component represents a world-class engineering team. Without this global participation, ITER would not have been possible, but as a combined effort, each team leverages its investment with what it learns from the others. “
