Calculation of the Forces Applied to a Superconductor in Levitation in an Inhomogeneous Magnetic Field

Bernstein, P.; Xing, Yiteng; Noudem, Jacques

doi:10.21926/rpm.2203018

Cited by 4 publications

(4 citation statements)

References 31 publications

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“…However, measurements of the restoring force carried out on the samples investigated in this work have revealed that levitation with magnet PM70 was unstable for Z ⩽ Z L . This is due to the dependence of the restoring force on the net density of the vortices trapped in the sample [5,31], the entry of antivortices resulting in a decrease of this quantity and instability. Since stability depends also on the mean value of the magnet field in the superconductor, works are in progress to determine if an interesting trade-off between levitation force and stability can be achieved with large superconductors and magnets with suitable dimensions.…”

Section: Discussionmentioning

confidence: 99%

“…A detailed description of the mean field model can be found in [5,6,11,12]. The model considers that during the field cooling process, the magnetic flux generated by the magnet located at Z cp is channelled along vortex lines at the transition to the superconducting state at T c .…”

Section: Summary Of the Mean Field Modelmentioning

confidence: 99%

“…This observation suggests that at low temperatures some changes occur in the physics of the investigated superconductors below some threshold Z = Z L (Z L ≈ 15 mm for cycle T28). As a consequence, we assume that the corresponding cycles consist of the four steps mentioned in table 5.…”

Section: Modifications To the Mean Field Modelmentioning

confidence: 99%

“…to determine the samples critical current and surface current densities J c and J sc , respectively, as well as the thickness t of the layers carrying the superconducting current (see section 3) [5]. However, the model was verified with bulks generating a moderate levitating force only (see figure 1).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The possible effect of surface barriers on the magnetic levitation of cylindrical superconductors

Bernstein,

Xing,

Noudem

et al. 2023

Supercond. Sci. Technol.

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Superconducting magnetic levitation force measurements on large field cooled cylindrical MgB2 bulks with different diameters and thicknesses are reported. For these experiments, a special set-up permitting one to measure forces up to 500 N was used. In contradiction to previous measurements, the obtained force hysteresis cycles could not be reproduced with the analytical mean field model proposed by Bernstein et al (2017 Supercond. Sci. Technol. 30 065007). The failure of the model has been attributed to surface barriers effects which were not taken into account in the model. This last one was accordingly modified in order that the measured force cycles could be reproduced. Contrary to most other models describing surface barriers effects, the modified model suggests that above a threshold field anti-vortices and not vortices enter the superconductor. This behaviour is related to the storage by the superconductor of the mechanical work done by the operator. In addition, it has turned out that the threshold field is a decreasing function of the critical surface current density of the samples. As a consequence, the surface barriers effects occur only if this quantity and the critical current density are large enough. Otherwise, the internal magnetic field of the superconductor could be computed and was seen to be a decreasing function of the thickness of the superconductors.

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Section: Discussionmentioning

confidence: 99%