Superconducting Electromagnets

AbstractThe design and construction of superconducting magnets has been made possible by the development of technical superconductors. There are three principal materials: the alloy niobiumtitanium (NbTi), the intermetallic compound niobiumtin (Nb3Sn), and the collective high‐temperature superconductors (HTSs) based on copper oxide layers in a perovskite structure.Technical superconductors are a class having special properties that allow superconductor operation in high magnetic fields and with useful current densities. Superconductors are of two types; both can support the flow of electrical current without resistance only below a combination of maximum temperature, field, and current density, with critical parametersTc,Bc, andJc[1]. For type I superconductors, typical values ofTcandBcare 9 K and 0.1 T, respectively. Flux is excluded from the bulk of a type I superconductor, and current flows only in a surface layer, about 10−4 mm thick.By contrast, type II superconductors allow flux to penetrate into the bulk of the lattice in the form of an array of flux quanta.