Variable-temperature critical-current measurements on a Nb3Sn wire

We made variable-temperature critical-current (I-c) measurements on a commercial multifilamentary Nb3Sn wire for temperatures (T) from 4 to 17 K and magnetic fields (H) from 0 to 12 T using transport current. The sample had a diameter of 0.811 mm and a Cu/non-Cu ratio of about 1.5. The measurements cover the range of critical currents from less than 0.01 A to over 700 A. To verify the measurements at variable temperature, we compared critical currents up to 400 A on a specimen that was immersed in liquid helium to those on the same specimen in flowing helium gas. This comparison indicated our ability to control and measure specimen temperature was within 40 mK. The critical-current data presented include electric field/current (E - I) characteristics, and E - T characteristics at constant I and H, I-c(H) at constant T, and I-c(T) at constant H. Such data may be used to determine the temperature margin of magnet applications.