Niobium–tin

The material's ability to support high currents and magnetic fields was discovered in 1961 and started the era of large-scale applications of superconductivity.

[4][5] The central solenoid and toroidal field superconducting magnets for the planned experimental ITER fusion reactor use niobium–tin as a superconductor.

[7][8] At the Large Hadron Collider at CERN, extra-strong quadrupole magnets (for focussing beams) made with niobium–tin are being installed in key points of the accelerator between late 2018 and early 2020.

With both processes the strand is typically drawn to final size and coiled into a solenoid or cable before heat treatment.

Common strengthening materials include Inconel, stainless steel, molybdenum, and tantalum because of their high stiffness at cryogenic temperatures.

[13] Since the thermal expansion coefficients of the matrix, fiber, and niobium tin are all different, significant amounts of strain can be generated after the wire is annealed and cooled all the way down to operating temperatures.

[15] Strain in the niobium tin causes tetragonal distortions in the crystal lattice, which changes the electron-phonon interaction spectrum.

[16] At high enough strain, around 1%, the niobium tin conduit will develop fractures and the current carrying capability of the wire will be irreversibly damaged.

In most circumstances, except for high field conditions, the niobium tin conduit will fracture before the critical strain is reached.