At the end of the 1960s, the scientific community, starting with Russian scientists who were pioneers in this field, developed a machine capable of creating and confining a hot plasma (150 million°C) in a ring-shaped magnetic cage (or ‘torus’): the tokamak, for ‘Toroidalnaya Kamera Magnitnymi Katushkami’.
The plasma is confined by a superposition of magnetic fields:
- The toroidal magnetic field, which is 100,000 times stronger than the Earth’s magnetic field. It is created by toroidal magnetic coils.
- The poloidal magnetic field created by the central magnetic coil induces a current of several million amperes in the plasma.
- A set of horizontal magnets called poloidal coils ensure the plasma’s balance, position, shape and current control.
The resulting magnetic field inside the tokamak enclosure is a helix-shaped field.