Observations of the effect of pre-reaction on the properties of Nb<inf>3</inf>Sn Bronze composites

Abstract

The effect of varying the annealing temperature on the degree of pre-reaction of two Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn composites has been investigated. Annealing at 550, rather than 450 C produces noticeably more irregular growth and more uneven Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn layers when final reaction occurs. It is believed that this is due to the effect that pre-existing Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn nuclei have on subsequent Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn growth. In one case the use of four anneals at 550 C, rather than 450 C was found to reduce the J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> by 50%. Results are also presented on some samples of the HFTF conductor. It is concluded that over-annealing of the bronze can be a major cause of reduced J <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> in bronze Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn conductors.