Low frequency AC losses in multifilamentary superconductors up to 15 tesla

Abstract

Low frequency (1 Hz) ac losses were measured in a variety of A15 superconducting wires having different fiber geometries. Field modulations of ≤ 1 tesla were superimposed on a fixed background field up to 15 tesla. Losses were measured for Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn in continuous fiber, modified jelly-roll, In Situ, and powder metallurgy processed materials, and for Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Al powder metallurgy processed materials. The results are compared with dc magnetization measurements. The losses are purely hysteretic at these low frequencies, scale with J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (above ∼ 3 tesla), and are reduced substantially by twisting for all the materials. The lowest losses are observed for the Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Al wires.