The early superconductors were chunks of metal. A breakthrough came in the 1960s with the development of a superconducting wire, an alloy of niobium and titanium. With this wire, engineers could wind electromagnet coils. These superconducting coils permit the construction of extremely powerful electromagnets. As with many engineering advances, there are tradeoffs:

Cost Saving: Since the magnet is operated with the wire at superconducting temperatures, the resistance of the coils is zero and no energy is lost to heating the coils. For superconducting magnets, a small power supply is sufficient to initiate the flow of current.

Cost Increase: Since the coils must be maintained at a low temperature, an expensive liquid helium refrigeration system is required.

200-ton superconducting magnet built at Argonne National Laboratory as part of a project to investigate power generation from fusion (see Plasma Power in Physics in Action Archives); photo by Dan Giroux, courtesy of Argonne National Laboratory