Trial manufacture of a 2.5 km class long-length of Nb-matrix jelly-roll Nb/Al precursor wire for RHQT process

Since the RHQT-Nb₃Al conductor shows excellent superconducting characteristics in high magnetic fields, its application to a 1 GHz NMR insert coil is in particular expected. For such an application, the development of a long-length of RHQT-Nb₃Al wire is indispensable. However, the unit length of wire achieved was no more than 400 m so far, due to a restricted size of the multi-billet, while about a 2.5 km-length of wire is necessary for the NMR insert coil application. Thus, an attempt was made to produce a 2.5 km-length of precursor wire by using a large-sized billet, and we have succeeded in producing such a long-length of precursor wire (2.6 km) without any breaking of wire during hydrostatic extrusion and subsequent drawing processes.