Architecture and Transport Properties of Multifilamentary MgB2 Strands for MRI and Low AC Loss Applications.

Standard in-situ type MgB2 strands manufactured by Hyper Tech Inc have 19 - 36 subelements, a monel outer sheath, and a Cu interfilamentary matrix. Typical transport Jc s of the strands are 2×105 A/cm2 with n-values of 20 - 30 at 4.2 K and 5 T. This work introduces two new MgB2 conductor designs. First, a new class of MgB2 strand is designed for magnetic resonance imaging applications. This type has a higher Cu content designed to enhance protection of a magnet wound with it, and a larger diameter to increase the critical current. Second, a new class of low AC loss MgB2 strand with high filament count and a high resistance matrix is discussed. Transport properties at 4.2 K and fields up to 10 T are reported. Optical techniques are used to study the macro- and micro-structures of these MgB2 strands.