High performance, advanced-internal-magnesium-infiltration (AIMI) MgB₂ wires processed using a vapor-solid reaction...

MgB₂ superconducting wires made using a Mg infiltration method have reached a higher performance than either in-situ or ex-situ mixed powder based routes. Indeed, very high layer J _c coupled with whole-strand J _e (critical current per total strand cross section) exceeding 10⁴ A cm^-2 at 4.2 K, 10 T have been found for monocore MgB₂ wires. However, previous multicore infiltration route wires have not reached their potential for J _e due to partially reacted and non-uniform MgB₂ layers. This study shows that 18-core MgB₂ AIMI wires processed using a low temperature route can attain higher and more uniform J _e values due to a more uniform MgB₂ reaction layer. The formation of fully reacted, uniform MgB₂ layers is attributed to the switch from a liquid-solid to a vapor-solid reaction route.