This is a fusion reactor that was never built, a small power plant that takes the principles of a tokamak (use super-heated plasma to generate more power than you put into heating and containing the plasma) and adds different magnetic fields running in different directins to keep the hot stuff inside the donut-shaped body of the thing. A donut shape is technically a “torus,” and “toroidal” means in a circle that follows the shape of the donut. “Poloidal” means in a ring around the body of the donut; slicing the donut in half gives you two poloidal cross-sections.
So this thing used rings of magnetic fields to keep the plasma spinning safely as it moves around the torus.
Today, there’s a lot more heat in the US around the HSX, or Helically Symmetric eXperiment. As that wiki page describes the general gist of these designs: ” Computer-modeled odd-looking electromagnets will directly produce the needed magnetic field configuration. These devices combine the good confinement properties of tokamaks and the steady-state nature of conventional stellarators.”