The conductor used in nearly all modern superconducting MR scanners is niobium-titanium (NbTi) that becomes superconductive below 9.4°K. Each wire is composed of multiple NbTi microfilaments embedded in a copper core. The copper core has two functions: 1) to support and protect the delicate microfilaments; and 2) to serve as a low resistance path for large currents in the event superconductivity is lost. Scanners and spectrometers with field strengths greater than 10T frequently use a niobium-tin (Nb3Sn) alloy. Magnesium diboride (MgB2) is also emerging as a new superconducting material for scanners and other magnetic instruments because of its much higher transition temperature (39°K).
