Superconducting critical current densities of pure and alloyed (Ti) Nb<inf>3</inf>Sn multifilamentary wires by the expanded-metal process

Abstract

The critical current densities J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (H) at 4.2 K and up to 19 T were measured for a number of pure and alloyed (with Ti) Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn multifilamentary wires which were fabricated by the expanded metal process. The critical current density (including the areas of Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn, the Cu-Sn alloy matrix and the Ta barrier) of the pure Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn wire at 10 T was essentially equal to the value for conventionally processed Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn wires. However, it rapidly decreased with increased magnetic fields. Although the addition of small amounts (∼0.8 and ∼ 1.6 wt% Ti) to the Nb filaments decreased the values of J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> at 10 T, they did not decrease with the increasing field as rapidly as is the case for the pure Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn. The additions of Ti slightly decreased the amount of tensile strain on the wire required to achieve a maximum in J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (8 T) when compared to that required for the pure Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn. However, this amount was higher than that for a similar Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn wire which was conventionally processed.