Superconducting and mechanical performance and the strain effect, the influence of mechanical strain upon the critical current, were investigated for commercially available MgB2 multifilamentary tape. The conductor was made by using the ex situ route and had 14 filaments in a Ni matrix; with Cu stabilizer. The JC was measured as a function of magnetic field, B, at 4.2, 15, 20 and 25K and the irreversibility fields (Birr) were determined using JC–B curves at each temperature. The JC, measured as a function of field angle at 4.2K and 4T, exhibited an anisotropic behavior. Measurements were also made of JC as a function of temperature at 0 to 5T. The stress–strain relationship was tested at 296 and 113K. The strain effect was examined in magnetic fields at 4.2, 15 and 20K using a U-shape rig made of stainless steel (SUS304). The JC–strain relationship was linear and reversible in the window of external strain between -0.5% (compression) and 0.5% (tension). With increasing strain, large and irreversible degradation occurred after the maximum of JC (JCm) at 0.57% tension. Although d(JC/JCm)/d(strain), the slope of the linear JC–strain relation in the reversible regime, depended upon both temperature and magnetic field, the relationships between d(JC/JCm)/d(strain) and B/Birr fell on a universal line; regardless of temperature.

Superconducting and Mechanical Performance and the Strain Effects of a Multifilamentary MgB2/Ni Tape. H.Kitaguchi, H.Kumakura: Superconductor Science and Technology, 2005, 18, S284-9