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

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 Jc coupled with whole-strand Je (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 Je 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 Je 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.