NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin filmsPassive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation forces, e.g. microgravity - magnetic damping devices.
Document ID
19960000246
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Schoenhuber, P.
(Cornell Univ. Ithaca, NY, United States)
Moon, F. C.
(Cornell Univ. Ithaca, NY, United States)
Date Acquired
September 6, 2013
Publication Date
April 1, 1995
Publication Information
Publication: NASA. Johnson Space Center, Proceedings of the 4th International Conference and Exhibition: Workd Congress on Superconductivity, Volume 1
Subject Category
Solid-State Physics
Accession Number
96N10246
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
No Preview Available