Microstructure and Superconducting Properties of Cu Addition MgB2 Multifilamentary Wires Using Boron Isotope Powder as the Boron Source Material

Abstract The natural boron has two kinds of isotopes which are existed 20 wt% boron-10 ( 10 B) and 80 wt% boron-11 ( 11 B). 11 B isotope is stable against the neutron irradiation without nuclear transformation. For an advanced fusion application, in-situ PIT process using 11 B isotope powder as the boron source material was desirable to enhance low induced radio-activity of MgB2 superconducting wire. We tried to fabricate the in-situ Cu addition MgB2/Ta/Cu multifilamenatry wire using boron isotope powder as the boron source material. In this study, superconductivity and microstructure of MgB2 wire using boron isotope powder were investigated. Tc value of MgB2 wire using 11 B powder was shown to about 37 K by the low temperature diffusion reaction, and its value was higher than commercial natural powder. However, Jc value of MgB2 wire using 11 B isotope powder was remarkably lower than that of commercial natural powder. This is caused by the forming of much impurity phase and decrease of MgB2 volume fraction due to the remaining of much non-reactive 11 B isotope powder.