Niobium-tin

Unity cell of the A15 phases of Nb₃Sn

Niobium-tin (Nb₃Sn) or triniobium-tin is a metallic chemical compound of niobium (Nb) and tin (Sn), used industrially as a type II superconductor. This intermetallic compound is a A15 phases superconductor. It is more expensive than niobium-titanium (NbTi), but can withstand magnetic field intensity values up to 30 teslas (T), whereas NbTi can withstand only up to roughly 15 T.

Nb₃Sn was discovered to be a superconductor in 1954.

Its critical temperature is 18.3 kelvins (K). It is usually used at 4.2 K, the boiling point of liquid helium.

In April 2008 a record non-copper current density was claimed of 2643 A/mm² at 12 T and 4.2 K ^[1]

Practical use

Mechanically, Nb₃Sn is extremely brittle and thus can not be easily drawn into a wire, which is necessary for winding superconducting magnets. To overcome this, wire manufacturers typically draw down composite wires containing ductile precursors. The "internal tin" process include separate alloys of Nb, Cu and Sn. The "bronze" process contains Nb in a copper-tin bronze matrix. With both processes the strand is typically drawn to final size and coiled into a solenoid or cable before heat treatment. It is only during the heat treatment that the Sn reacts with the Nb to form the brittle, superconducting niobium-tin compound.^[2]

The powder-in-tube process is also used ^[3][1].

The high field section of modern NMR magnets are composed of niobium-tin wire.

Some niobium-tin wires can be wound after heat treatment.

History

Nb₃Sn was discovered to be a superconductor in 1954, one year after the discovery of the first type of A₃B superconductors V₃Si.^[4] In 1961 it was discovered that niobium-tin still exhibits superconductivity at large currents and strong magnetic fields, thus becoming the first known material to support the high currents and fields necessary for making useful high-power magnets and electric power machinery.^[5][6]

Notable uses

The central solenoid and toroidal field superconducting magnets for the ITER fusion reactor use niobium-tin as a superconductor ^[7]. The central solenoid coil will produce a field of 13.5 teslas. The toroidal field coils will operate at a maximum field of 11.8 T.

The International Thermonuclear Experimental Reactor is estimated to use 600 metric tonnes of Nb₃Sn strands and 250 metric tonnes of NbTi strands.^[8][9].

The LHC upgrade will use superconducting magnets made of niobium-tin.

See also

• Niobium-titanium

References

1. ^ ^{a b} "Record current with powder-in-tube superconductor". laboratorytalk.com. http://www.laboratorytalk.com/news/bru/bru219.html. Retrieved 2008-09-06. 
2. ^ http://supercon.lbl.gov/SuperconDocuments/SSC-MAG-81-1986.pdf
3. ^ J.L.H., Lindenhovius; Hornsveld, E.M.; den Ouden, A.; Wessel, W.A.J.; ten Kate, H.H.J. (2000). "Powder-in-tube (PIT) Nb₃Sn conductors for high-field magnets". Applied Superconductivity 10 (1): 975–978. doi:10.1109/77.828394. http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/77/17989/00828394.pdf?arnumber=828394. Retrieved 2008-09-06. 
4. ^ Matthias, B. T.; Geballe, T. H.; Geller, S.; Corenzwit, E. (1954). "Superconductivity of Nb₃Sn". Physical Review 95 (6): 1435–1435. doi:10.1103/PhysRev.95.1435. 
5. ^ Geballe, Theodore H. (October 1993). "Superconductivity: From Physics to Technology". Physics Today 46 (10): pp. 52–56. doi:10.1063/1.881384. 
6. ^ Godeke, A. (2006). "A review of the properties of Nb3Sn and their variation with A15 composition, morphology and strain state". Supercond. Sci. Technol. 19 (8): R68–R80. doi:10.1088/0953-2048/19/8/R02. 
7. ^ "Results of the first tests on the ITER toroidal magnet conductor". Commissariat à l'Énergie Atomique. 2001-09-10. http://www-fusion-magnetique.cea.fr/gb/actualites/01-0910-insert_tf.htm. Retrieved 2008-09-06. 
8. ^ G. Grunblatt; P. Mocaer, Ch. Verwaerde and C. Kohler (2005). "A success story: LHC cable production at ALSTOM-MSA". Fusion Engineering and Design (Proceedings of the 23rd Symposium of Fusion Technology) 75–79: 1–5. 
9. ^ "Alstom and Oxford Instruments Team Up to Offer Niobium-Tin Superconducting Strand". Alstrom. 2007-06-27. http://www.azom.com/news.asp?newsID=9064. Retrieved 2008-09-06. 

External links

• European Advanced Superconductors