A toroidal magnetic field is shaped like a doughnut. This design is crucial for applications in fusion energy because it allows the magnetic field lines to loop continuously around the plasma. The unique geometry of a torus provides stability and confinement for the high-temperature plasma, which is essential to achieve the conditions needed for fusion reactions.
The symmetry of the toroidal shape helps in minimizing the risk of instabilities that can occur if the plasma were to touch the walls of the containment vessel. By having a closed-loop magnetic field, the plasma is kept away from the material boundaries, thus enhancing confinement and improving the efficiency of the fusion process.