Advertisement

Closely Spaced Fine Filament Multifilamentary NbTi Strands

  • E. Gregory
  • H. Liu
  • J. M. Seuntjens
Part of the An International Cryogenic Materials Conference Publication book series (ACRE, volume 40)

Abstract

A series of papers1–8 showing the advantages of close spacing and matrix alloying for the development of high Jc, fine filament, NbTi materials which have low electrical coupling have appeared in the last seven years. In order to achieve the highest Jc’s, it has been shown that close spacing has many advantages1–3. This, however, leads to proximity coupling which has to be overcome by the addition of alloying elements to the matrix between the filaments4–11. Of the three alloying materials normally used for this purpose, Ni, Si and Mn, the most effective is Mn, which operates by a spin flip scattering mechanism whereas Ni and Si produce decoupling by less effective resistive scattering. Ni and Si, however, harden the matrix more than does the small amount of Mn, [0.5wt.%], which has been used in most of the past work on the reduction of proximity coupling. This hardening allows the filaments to be separated to a greater extent than is possible in the case of a pure copper matrix without a significant increase in filament sausaging and a resultant Jc decrease. Silicon also has one additional advantage over the other alloying elements in that it reduces the formation of compounds on the surface of the filaments8–11, thus it may obviate the necessity for a Nb barrier layer8 and thus allow an even greater increase in Jc.

Keywords

Filament Size Close Spacing Copper Matrix Fine Filament Precipitation Heat Treatment 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    E. Gregory, T. S. Kreilick, A. K. Ghosh and W. B. Sampson, Importance of spacing in the development of high current densities in multifilamentary superconductors, Cryogenics, 27, 4, pp. 178–182, 1987.CrossRefGoogle Scholar
  2. 2.
    T.S. Kreilick and E. Gregory, Further improvements in current density by reduction of filament spacing in multifilamentary NbTi superconductors, Cryogenics, 27, 7, 401, 1987.CrossRefGoogle Scholar
  3. 3.
    E. Gregory, H. Liu, G.M. Ozeryansky, M.D. Sumption, K.R. Marken and E.W. Collings, Experiments to improve materials for SSC magnets, IISSC 4 pp. 923–930, New Orleans, LA, Plenum Press, NYC, NY 1992.Google Scholar
  4. 4.
    T.S. Kreilick, E. Gregory, J. Wong, R. M. Scanlan, A. K. Ghosh, W. B. Sampson and E.W. Collings, Reduction of coupling in fine filament Cu NbTi composites by the addition of manganese to the matrix, in: Adv. in Cryo. Eng., A. F. Clark and R. P. Reed, eds., Plenum, New York, 34, 895, (1988).Google Scholar
  5. 5.
    A.K. Ghosh, W. B. Sampson, E. Gregory, T. S. Kreilick and J. Wong, The effect of magnetic impurities and barriers on the magnetization and critical current of fine filament NbTi composites, IEEE Trans. 24, 2, 1145, (1988).Google Scholar
  6. 6.
    E. Gregory, T.S. Kreilick, J. Wong, E. W. Collings, K. R. Marken, Jr., R. M. Scanlan and C. E. Taylor, A conductor, with uncoupled 2.5 µm. diameter filaments, designed for the outer cable of SSC dipole magnets, IEEE Trans, vol. 25, 2, pp. 1926–1929, (1989).Google Scholar
  7. 7.
    T. S. Kreilick, E. Gregory, and J. Wong, The designing and fabrication of multifilamentary NbTi composites utilizing various matrix materials, Journal of Less Common Metals, 139, 45, (1988)CrossRefGoogle Scholar
  8. 8.
    H. Liu, K. J. Faase, E. Gregory and B.A. Zeitlin, The addition of silicon to the copper between NbTi filaments to reduce interdiffusion, Presented at IISSC 5 San Fransico May (1993).Google Scholar
  9. 9.
    K. Tachikawa, J. Ninomiya, T. Ajioka, M. Terda and K. Sakinada, Recent Studies on Composite Superconductors, 7th U.S.–Japan Workshop on High Field Superconductors, Fukuoka, Japan, Oct. 22–24, (1991).Google Scholar
  10. 10.
    K. Tachikawa, S Koyama, S. Akita, S. Torii, H. Kasahara, Y. Tanaka, K. Matsumoto, Material and electro-magnetic Aspects of newly developed Nb-Ti wires for ac use with Cu-Si alloy matrix, Trans IEEE, Appl Superconductivity, 3, 1, pp. 1374–1377, 1993CrossRefGoogle Scholar
  11. 11.
    S. Akita, S. Torii, H. Kasahara, K. Matsumoto, Y. Tanaka, T. Ajioka and K. Tachikawa, Ultrafine multifilamentary Nb-Ti wires with Cu-Si alloy matrix, Cryogenics, 33, 2, pp. 199–204, (1993).CrossRefGoogle Scholar
  12. 12.
    T.S. Kreilick, E. Gregory, P. Valaris and J.Wong, The mechanical and electrical effects of adding manganese to the copper matrix of multifilamentary niobium-titanium superconducting composites, pp. 857–863, Proc. ICEC 12, Butterworths, Guildford, Surrey, U.K. (1988).Google Scholar
  13. 13.
    H. Kanithi, P. Valaris and B. A. Zeitlin, A novel approalch to make fine filament superconductors. “Supercollider 4,” John Nonte, ed., Plenum Press, New York, pp. 41–47, (1992).Google Scholar

Copyright information

© Springer Science+Business Media New York 1994

Authors and Affiliations

  • E. Gregory
    • 1
  • H. Liu
    • 1
  • J. M. Seuntjens
    • 2
  1. 1.IGC Advanced Superconductors, Inc.WaterburyUSA
  2. 2.Superconducting Super Collider LaboratoryDallasUSA

Personalised recommendations