X-ray tomography assessment of the heat treatment effect on Nb3Sn wires with different architectures

Abstract

Two unreacted commercially available Nb 3 Sn precursor wires with different architecture were subject to a two-temperature heat treatment in vacuum at 650 °C for 72 h and at 700 °C for 168 h. Evolution of wires towards formation of the superconducting phase was assessed by the non-invasive X-ray computed microtomography (micro XRT) with a spatial resolution of ∼2 μm on the samples before and after the heat treatments. Statistical image analysis quantified the defects and quantitatively revealed the deviation of the geometrical perfection of the wire components comparative to designed parameters depending on the wire architecture and heat treatment conditions. Our results position XRT as a tool to evaluate the quality of Nb 3 Sn, also promoting it as a method capable for providing new insights that could be used in the optimization processes of Nb 3 Sn wires design, technology, and during operation. • Wires of Nb 3 Sn were heat treated (HT) and assessed by x-ray tomography (XRT). • Before and after HT, defects and deviation from design parameters were quantified. • Architecture has a strong influence on the HT processes and quality of the wires. • XRT emerges as a non-invasive tool with novel, unique characterization possibilities. • XRT contributes wires optimization, fabrication, application, and during operation.