Properties of multifilamentary Nb<inf>3</inf>Sn conductors

Abstract

Measurements on Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn multifilamentary conductors show that normally a degradation of the transition temperature T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> and of the critical current I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> occurs as a result of the compressive strain exerted by the bronze on the Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn layers when cooling down. When tensile stresses are applied, therefore, an increase of the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> up to a maximum value is observed at first and then the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> begins to decrease. These compressive strains are favourable factors when the conductor is subjected to tensile and bending loads. A coil reacted after winding produces a flux density of 12 T in a 7.5 T background field. The measured I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> values were 10 % higher than in short samples. A coil wound with pre-reacted conductors produces a flux density of 13 T in an 8 T background field and, with an insert coil in the 55 mm bore of this magnet, 14.5 T has been measured.