Poloidal coils encircling ASDEX tokamak. (Credit: © IPP, www.ipp.mpg.de)

Circular electromagnets used to stabilize the plasma in a tokamak or stellarator. The poloidal coils are positioned horizontally and surround the entire vacuum vessel including e.g. toroidal coils. Their function is to push the expanding plasma back into the centre of the vacuum vessel. They are most often used for shaping and positioning of the plasma. The largest poloidal coil in the world, 24 metres in diameter, is in the ITER tokamak.