Title :
High-field performance and structure of (Nb,Ta)3Sn superconductors produced by Ta-Sn core
Author :
Tachikawa, K. ; Kato, T. ; Matsumoto, H. ; Kato, R. ; Takeuchi, T.
Author_Institution :
Fac. of Eng., Tokai Univ., Kanagawa, Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
New (Nb,Ta)3Sn high-field conductors have been fabricated using a Ta-Sn powder core and a Nb-Ta alloy sheath. An appropriate Ta/Sn composition ratio in the core is 6/5 to 6/4, and an optimum Ta concentration in the sheath is 3 to 4 at%. In tape specimens, relative thickness ratio of (Nb,Ta)3Sn layer increases with decreasing total thickness of the tape. The non-Cu Jc at 23 T and 4.2 K of 0.6 mm-thick tape is 1.15×104 A/cm2, while that of 0.3 mm-thick tape is 1.35×104 A/cm2 . 2 wt%Cu addition to the core decreases the optimum reaction temperature from 900°C to 800°C. More homogeneous and finer grain structure of (Nb,Ta)3Sn is obtained in specimens with a small amount of Cu addition. 2 wt%Cu addition to the core enhances non-Cu Jc of the tape in fields lower than 22 T. Mono-core wire specimens are also easily fabricated, and show excellent non-Cu J c values in the field range of 21 to 23 T at 4.2 K
Keywords :
alloying additions; composite superconductors; critical current density (superconductivity); crystal microstructure; niobium alloys; powder metallurgy; superconducting tapes; tantalum alloys; tin alloys; type II superconductors; (Nb,Ta)3Sn superconductors; (NbTa)3Sn; 21 to 23 T; 4.2 K; 900 to 800 degC; Cu addition; Nb-Ta; Nb-Ta alloy sheath; Ta-Sn; Ta-Sn powder core; Ta/Sn composition ratio; critical current density; grain structure; high-field conductors; high-field performance; mono-core wire specimens; optimum Ta concentration; optimum reaction temperature; relative thickness ratio; structure; tape specimens; Conductors; Current measurement; Magnetic field measurement; Niobium; Powders; Scanning electron microscopy; Superconductivity; Temperature; Tin; Wire;
Journal_Title :
Applied Superconductivity, IEEE Transactions on