State of the art powder-in-tube niobium–tin superconductors

Powder-in-tube (PIT) processed niobium–tin wires are commercially manufactured for nearly three decades and have demonstrated a combination of very high current density (presently up to 2500 A mm−2 non-Cu at 12 T and 4.2 K) with fine (35 μm), well separated filaments. We review the developments that have led to the present state of the art PIT niobium–tin wires, discuss the wire manufacturing and A15 formation processes, and describe typical superconducting performance in relation to magnetic field and strain. We further highlight successful applications of PIT wires and conclude with an outlook on possibilities for further improvements in the performance of PIT niobium–tin wires.