Speaker
Description
In this work we pursue the development of high-Jc multifilamentary (Nb,Ti)3Sn wire containing ZrO2 APCs. Previously, 61-filament powder-in-tube (PIT) APC Nb3Sn binary conductors were demonstrated. These conductors showed very high pinning strength and high layer Jcs at 12 and 15 T (a layer Jc double the best RRP wires). However, the wires had low A15 layer conversion fractions, because the designs were not optimized. Additionally, they were binary, and thus not optimized for the highest fields. Here, new 61 subelement binary designs were made to achieve higher Sn/Nb ratios, leading to conductors with larger A15 conversion factors; these results are discussed. Next, we performed some initial work in order to develop a ternary wire. In this experiment, an externally oxidized tube-type wire was manufactured, starting from a precursor of Cu-Sn-Ti rod in a Nb-1%Zr tube. Samples were heat-treated in a vacuum sealed quartz tube with CuO present. Heat treatment schedules included 20°C/h up to 650°C for 300h, and 20°C/h up to 700°C for 100h. Grain refinement (about 35nm) was observed due to the internal oxidation process, and Ti was observed within A15 layer, demonstrating a simple ternary APC route. Subsequently, a modified restack was manufactured with internal oxide and Ti sources. Heat treatment times and schedules were optimized for oxygen diffusion and phase formation. Refined grain sizes and Ti inclusion are also detailed for this ternary option. The SEM, magnetic, and transport results are presented for these conductors.
