Thursday, 1A-10, 6:00-6:10

Cuprates for High Field Magnets

David Larbalestier

Zhijun Chen, Jan Jaroszynski, Jianyi Jiang, Fumitake Kametani, Pei Li, Denis Markiewicz, Patrick Noyes, Ulf Trociewitz, Huub Weijers, Aixia Xu

National High Magnetic Field Laboratory, 2031 East Paul Dirac Drive, Tallahassee FL 32310 USA

Although no all-superconducting, HTS-containing magnet has yet challenged the capabilities of classical Nb-base magnets at 4K, the time when this will occur seems near at hand. From this point of view the very strong Hastelloy substrates employed for a number of coated conductor designs are very attractive. Recent SuperPower tapes made by the MOCVD route are particularly attractive since their overall J_c(4K, H) exceeds that of Nb3Sn by a substantial amount, even if the fraction of superconductor in the cross-section is 1%, rather than 30-50%. We have been making extensive characterizations of such conductors. LTLSM shows that IBAD-MgO tapes with FWHM of 2-3° exhibit little local contrast by low temperature laser scanning microscopy, implying a high uniformity of current flow that is consistent with their low YBCO grain boundary misorientation distribution of 2-3°. The tape magnetization also shows few signs of flux jumps at 4K, even with field perpendicular to the broad face of 4 mm wide tapes. As expected from many evaluations of the angular dependence of J_c at higher temperatures and low fields, there is extensive evidence for correlated pinning defect detail in specific ranges of temperature and field. The recent test of a coil made from such tape which generated a total field of 2.8 T in a 31 T background field following an earlier coil generating 7.8T in a 19 T background shows that all superconducting magnets above 30 T are now conceivable.

*We are grateful to SuperPower for partial support of some of these tests.

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