Characterization of Mechanical Properties of Conductor for the Superconducting Link Project at CERN

In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB₂ wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young´s modulus of MgB₂ filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB₂, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young´s modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young´s modulus of MgB₂ was estimated to be lower than that reported for highly dense MgB₂ bulks. The reason for such difference is discussed from the viewpoint of void fraction.