Superconducting Electromagnets

Abstract

The 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 (Nb 3 Sn), 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 parameters T c , B c , and J c [1]. For type I superconductors, typical values of T c and B c are 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.