Superconducting magnets

An electromagnet made by using coils of superconducting coils orcables is called a superconducting magnet. Type I superconductors arenot used since their Hc values are low. Type II superconductors, forexample, alloys like Nb3Sn and Nb3Ti are used for the construction ofsuperconducting magnets.The material itself cannot be used directly in the form of wire. Twoparallel current carrying wires exert force on each other. The forcewill be attractive if the two currents are parallel and repulsive ifthey are in opposite direction. Attractive force will lead to enormouscompressional forces squeezing the solenoid axially. Repulsive forcesmay try to blow open the solenoid.For the construction of superconducting magnets, the superconductingwires are made in the form of tiny filaments which are embedded in acopper matrix by certain kind of material processing. Copper matrixalso prevents mechanical fracture that may happen in thesuperconducting material.Magnetic fields of the order of 15 Tesla can be achieved here and itrequires only a little liquid helium to keep in operation.Superconducting magnets are used in many applications. Most importantapplications are in MRI scan and maglev vehicles.