Stories from Physics for 11-14 14-16
The iron cores in solenoid magnets typically saturate at field strengths of a few tesla, limiting the strength of field they can produce. An improved design is the Bitter electromagnet which is constructed from a series of circular metal plates, drilled with a pattern of holes, and separated by insulating spaces. This design causes currents to circulate in a helical pattern. Water can be pumped through the holes to cool the metal as the high currents, of the order of 10,000 A, cause large heating effects.
While superconducting magnets can produce fields of up to 22 T, a Bitter electromagnet has been constructed that produces a field of 37.5 T and a hybrid superconducting-Bitter magnet can reach fields of 45 T.