poloidal field

The term "poloidal" refers to a magnetic field that extends between the poles of a magnetic body, such as the Earth, and into surrounding space. In the context of fusion reactors, a poloidal magnetic field is a component of the helical magnetic field that spirals around a torus. This component is directed the short way around the machine and is crucial for maintaining the plasma in a stable equilibrium.12

Without a poloidal field, plasma particles would drift to the walls. The poloidal field is generated by an electric current flowing within the plasma itself. This current can be initiated using Faraday's law of induction or driven by methods like radio-frequency current drive or neutral-beam current drive, though these have low efficiency. A more efficient method is the "bootstrap current," which arises spontaneously from particle dynamics within the plasma.2