Drift of levitated YBCO superconductor induced by both a variable magnetic field and a vibration

Drift of Levitated/Suspended Body in High-$T_{c}$ Superconducting Levitation Systems Under Vibration—Part I: A Criterion Based on Magnetic Force-Gap Relation for Gap Varying With Time

“…The second examination of the numerical code is to predict the experimental phenomenon of downward drift of vibration center of LB in the levitation system [9]. In this experiment, a harmonic excitation of vertical displacement, , is applied.…”

“…Denote . From Newton's second law, the dynamic equation of vertical movement of the PM can be expressed as (8) and the initial conditions are taken into account by (9) Here, is the mass of the LB, stands for the air-damping coefficient, and is the gravitational acceleration; , , and are, respectively, the displacement, velocity, and acceleration of the PM relative to its static equilibrium position; represents the vertical component of magnetic force ; indicates an external excitation force. When an external excitation of displacement is applied to the superconductor, for example, we have .…”

“…Some experiments have found that, even for a very simple levitation system (a PM is levitated above an HTSC, or suspended below an HTSC), a vibration of PM/HTSC or an alternating magnetic field applied to an HTSC can make the levitated body (LB) drift (i.e., gap varying with time) [8]- [10] or even collapse [11], Manuscript which is directly related to the safe operation and design of the whole system. Nemoshkalenko et al [8] and Terentiev et al [9] first observed that the drift vertically down (i.e., gap decreasing with time) from the LB is induced by a vibration of HTSC/PM or an alternating magnetic field applied to an HTSC. Using various HTSC samples such as free-sintered, melt-quenched, and melt-powder-melt-growth ones, Hikihara et al [10] found that the drift does not depend on the preparation method of HTSC, material, and the cooling method, but mainly on the hysteresis relation between magnetic force and gap.…”

Magnetic Relaxation - Methods for Stabilization of Magnetization and Levitation Force

“…The direct measurements of the interaction force between magnet and superconductor (Moon et al, 1990;Riise et al, 1992;Smolyak et al, 2002) showed a considerable decrease of the force with time. However, in the experiments, where the drift of levitating HTS samples was observed, the levitation height did not change in the stationary magnetic field (Krasnyuk & Mitrofanov, 1990;Terentiev & Kuznetsov, 1992). We suggested that in the case of levitation the relaxation rate of magnetic force was much smaller than in the case of fixed position of superconductor and magnet (when the magnetic force acts on the superconductor, and the sample is fixed at the suspension point).…”

Vibration effect on magnetization and critical current density of superconductors

“…It would allow eliminating existing inconsistencies in measurements, corresponding data interpretations, and verifying models and explanations proposed on the basis of results obtained with instrumentally driven, phenomenological artefacts. The understanding of this influence can also allow one to study possible suppression of superconducting properties by vibrations at low frequency/amplitude, which naturally appears during application of superconductors [22,23,24,25].…”