# Niobium–titanium

Niobium-titanium (Nb-Ti) is an alloy of niobium and titanium, used industrially as a type II superconductor wire for superconducting magnets, normally as Nb-Ti fibres in an aluminium or copper matrix.

Its critical temperature is about 10 kelvins.[1]

In 1962, at Atomics International, T. G. Berlincourt and R. R. Hake,[2][3] discovered the superior high-critical-magnetic-field, high-critical-supercurrent-density properties of Nb-Ti that, together with affordability and easy workability, distinguish Nb-Ti alloys from thousands of other superconductors and justify their status as the most widely utilized (workhorse) superconductors.

With a maximal critical magnetic field of about 15 teslas, Nb-Ti alloys are suitable for fabricating supermagnets generating magnetic fields up to about 10 teslas. For higher magnetic fields, higher-performance, but more expensive and less easily fabricated superconductors, such as niobium-tin, are commonly employed.

The part of global economic activity for which superconductivity is indispensable amounted to about five billion euros in 2014.[4] MRI systems, most of which employ niobium-titanium, accounted for about 80% of that total.

## Notable uses

### Superconducting magnets

A bubble chamber at Argonne National Laboratory has a 4.8-meter-diameter Nb-Ti magnet producing a magnetic field of 1.8 tesla.[5]

About 1000 NbTi SC magnets were used in the 4-mile-long main ring of the Tevatron accelerator at Fermilab;[6] the magnets were wound with 50 tons of copper cables containing 17 tons of NbTi filaments.[7] They operate at 4.5 K generating fields up to 4.5 tesla.

1999: The Relativistic Heavy Ion Collider uses 1,740 NbTi SC 3.45 tesla magnets to bend beams in its 3.8 km double storage ring.[8]

In the Large Hadron Collider particle accelerator the magnets (containing 1200 tonnes of NbTi cable[9] of which 470 tonnes are Nb-Ti[10] and the rest copper) are cooled to 1.9 K to allow safe operation at fields of up to 8.3 T.

Nb-Ti wires coming out of an LHC dipole magnet.

Niobium-titanium superconducting magnet coils (liquid helium cooled) were built to be used in the Alpha Magnetic Spectrometer mission to be flown on the international space station, they were later replaced by non-superconducting magnets.

The experimental fusion reactor ITER uses Niobium-titanium for its poloidal field coils. In 2008 a test coil achieved stable operation at 52 kA and 6.4 Tesla.[11]

The Wendelstein 7-X stellarator uses NbTi for its magnets.

## References

1. ^ Charifoulline, Z. (May 2006). "Residual Resistivity Ratio (RRR) measurements of LHC superconducting NbTi cable strands". IEEE Transactions on Applied Superconductivity. 16 (2): 1188–1191. Bibcode:2006ITAS...16.1188C. doi:10.1109/TASC.2006.873322.
2. ^ T. G. Berlincourt and R. R. Hake (1962). "Pulsed-Magnetic-Field Studies of Superconducting Transition Metal Alloys at High and Low Current Densities". Bull. Am. Phys. Soc. 2 (7): 408.
3. ^ T. G. Berlincourt (1987). "Emergence of NbTi as a Supermagnet Material". Cryogenics. 27 (6): 283. doi:10.1016/0011-2275(87)90057-9.
4. ^ "Archived copy". Archived from the original on 2014-08-11. Retrieved 2015-05-17.CS1 maint: archived copy as title (link)
5. ^ "Superconducting Magnets". HyperPhysics. Retrieved 4 Jan 2019.
6. ^ R. Scanlan (May 1986). "Survey of High Field Superconducting Material for Accelerator Magnets" (PDF). Archived from the original (PDF) on 2011-08-30. Retrieved 2011-08-30.
7. ^ Robert R. Wilson (1978). "The Tevatron" (PDF). Fermilab. Retrieved 4 Jan 2019.
8. ^ "Archived copy". Archived from the original on 2011-06-07. Retrieved 2009-12-07.CS1 maint: archived copy as title (link)
9. ^ Lucio Rossi (22 Feb 2010). "Superconductivity: its role, its success and its setbacks in the Large Hadron Collider of CERN". Superconductor Science and Technology. 23 (3): 034001. doi:10.1088/0953-2048/23/3/034001.
10. ^ Status of the LHC superconducting cable mass production 2002
11. ^ "Milestones in the History of the ITER Project". iter.org. 2011. Retrieved 31 March 2011. The test coil achieves stable operation at 52 kA and 6.4 Tesla.