This is the Tokamak nuclear fusion reactor

The term "Tokamak" comes from a Russian acronym meaning "Toroid chamber with magnetic coils".

It is an experimental machine designed to harness fusion energy. The energy is absorbed inside the Tokamak in the form of heat, attached to the walls of the vessel. The fusion plant uses this heat to produce steam and then electricity through turbines and generators.

In a tokamak device, very strong magnetic fields are used to confine and control the plasma.

The heart of the tokamak is a toroidal (i.e. doughnut) shaped vacuum chamber. Inside this chamber, and under the influence of enormous pressures and temperatures, the gaseous hydrogen fuel is converted into plasma to allow the hydrogen atoms to fuse. The charged particles in the plasma can be controlled by the huge magnetic coils located around the vessel.

In this video, we explain it with pictures: