Superconducting critical-current densities of commercial multifilamentary Nb 3Sn(Ti) wires made by the bronze process

Abstract

Superconducting critical-current densities J c in fields up to 24 T and at 4.2 and 1.8 K were measured for a number of commercial Nb 3Sn wires which were alloyed with Ti. The best values of J c (for the area excluding the stabilizing copper) at 20 T and at 4.2 and 1.8 K were 78 and 156 A mm −2, respectively. These values are approximately 10 and 4 times greater than values for the best ‘pure’ Nb 3Sn wire for these measurement parameters. In order to achieve these high current densities at H>20 T, it was shown that nonuniformity of the filaments had to be minimized. It was also shown that the grain size of Nb 3Sn is not very important in determining J c at these high magnetic fields, and that achieving high values of critical magnetic field H c2 is more important than small grain size.