Tuesday, May 7, 2013

1305.1269 (D. C. Larbalestier et al.)

A transformative superconducting magnet technology for fields well above
30 T using isotropic round wire multifilament Bi2Sr2CaCu2O8-x conductor

D. C. Larbalestier, J. Jiang, U. P. Trociewitz, F. Kametani, C. Scheuerlein, M. Dalban-Canassy, M. Matras, P. Chen, N. C. Craig, P. J. Lee, E. E. Hellstrom
We report here that magnetic fields of almost 34 T, far above the upper 24 T limit of Nb3Sn, can be generated using a multifilament round wire conductor made of the high temperature cuprate superconductor Bi2Sr2CaCu2O8-x (Bi-2212). A remarkable attribute of this Bi-2212 conductor is that it does not exhibit macroscopic texture and contains many high angle grain boundaries but nevertheless attains very high superconducting critical current densities Jc of 2500 A/mm2 at 20 T and 4.2 K. This Bi-2212 conductor does not possess the extreme texture that high Jc coated conductors of REBa2Cu3O7-x (REBCO) require, avoiding also its high aspect ratio, large superconducting anisotropy and the inherent sensitivity to defects of a single filament conductor. Bi-2212 wires can be wound or cabled into almost any type of superconducting magnet and will be especially valuable for very high field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. This demonstration that grain boundary limits to high Jc can be practically overcome suggests the huge value of a renewed focus on grain boundary properties in non-ideal geometries, especially with the goal of translating the lessons of this Bi-2212 conductor into fabrication of multifilament round wire REBCO or Fe-based superconductors.
View original: http://arxiv.org/abs/1305.1269

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