Levitation Properties Research Articles

The Magnetic Levitation Properties of YBCO Bulks Induced by a Recycling SmBCO Seed Crystal

The Magnetic Levitation Properties of YBCO Bulks Induced by a Recycling SmBCO Seed Crystal

Comparison of Levitation Properties between Bulk High-Temperature Superconductor Blocks and High-Temperature Superconductor Tape Stacks Prepared from Commercial Coated Conductors.

Bulk high-temperature superconductors (HTSs) such as REBa2Cu3O7-x (REBCO, RE = Y, Gd) are commonly used in rotationally symmetric superconducting magnetic bearings. However, such bulks have several disadvantages such as brittleness, limited availability and high costs due to the time-consuming and energy-intensive fabrication process. Alternatively, tape stacks of HTS-coated conductors might be used for these devices promising an improved bearing efficiency due to a simplification of manufacturing processes for the required shapes, higher mechanical strength, improved thermal performance, higher availability and therefore potentially reduced costs. Hence, tape stacks with a base area of (12 × 12) mm2 and a height of up to 12 mm were prepared and compared to commercial bulks of the same size. The trapped field measurements at 77 K showed slightly higher values for the tape stacks if compared to bulks with the same size. Afterwards, the maximum levitation forces in zero field (ZFC) and field cooling (FC) modes were measured while approaching a permanent magnet, which allows the stiffness in the vertical and lateral directions to be determined. Similar levitation forces were measured in the vertical direction for bulk samples and tape stacks in ZFC and FC modes, whereas the lateral forces were almost zero for stacks with the REBCO films parallel to the magnet. A 90° rotation of the tape stacks with respect to the magnet results in the opposite behavior, i.e., a high lateral but negligible vertical stiffness. This anisotropy originates from the arrangement of decoupled superconducting layers in the tape stacks. Therefore, a combination of stacks with vertical and lateral alignment is required for stable levitation in a bearing.

Analysis for Levitation of EHD and Electrostatic Propulsion Device in Direction of Gravity using Optical Flow Method

Electro hydro dynamic (EHD) and electrostatic propulsion devices have no moving parts and, in the air, operate on electrical energy. Thus, electric propulsion systems without moving parts such as propellers are expected to be developed in the future. EHD devices levitate in the direction opposite the direction of gravity when a high voltage is applied. In this study, detailed properties of the accurate propulsion direction, speed, and acceleration were clarified by imaging analysis. The analysis clarified that even if the orientation of the device was initially tilted from a horizontal line, the device was made to levitate vertically upward in the same direction as the direction of gravity, and a restoring force acts to return the orientation to a horizontal line during the levitation. These phenomena are very strange and different from those of drones with propellers. When the device levitates, the acceleration does not become constant immediately after the voltage is applied, but after passing through 0, it increases linearly in temporal duration of sub 0.1 s and saturates. The saturation of the acceleration changed with the input voltage. In this study, we used optical flow analysis, which is a well-known and proven imaging analysis, to analyze the trajectory of an object using image analysis. Detailed levitation properties have not been analyzed until now. First, as a result of analyzing the free flight characteristics of a single plate electrode, a single unit that has been very well researched in many papers, it was revealed that the direction of propulsion changes from the lateral direction to the direction of gravity midway through. Analysis on the levitation property of a EHD device, which has a special structure with a large area on the ground at a triangular center, and a propulsion device revealed that the EHD device can only levitate in almost the same direction as gravity. The maximum acceleration of the EHD device in these experiments was estimated to be 7 m/s2 .

Levitation force approximation of YBCO hybrid superconductors using critical-state theory and partitioning method

Introducing the second-generation coated conductor tapes (2G tapes) can enhance the performance of yttrium-barium-copper-oxide bulk superconductors (SCs) in terms of force, damping, and shape diversity. In this study, we investigate a hybrid SC that utilizes 2G tapes wrapped around the pivotal bulk component to achieve performance improvements. We also present a straightforward method, based on critical-state theory, to approximate the levitation force of this hybrid SC. This method characterizes the stack of tapes as an equivalent bulk with higher anisotropy and applies a fitting Kim model as an integrated expression of J (H) and J anisotropy. The partitioning method divides the SC into several isolated elements where the external field is approximately uniform within each sub-volume. Comparisons of calculated results with experiments indicate that this method can predict levitation properties with reasonable accuracy in just a few seconds. Furthermore, we propose two geometries of hybrid SC, namely, width-hybrid, and height-hybrid SC, for practical applications. Among them, the width-hybrid form exhibits higher efficiency in levitation. Our findings highlight the importance of applying the coated conductor stack when the magnetic field orientation is perpendicular to the a–b planes.

Vertical and lateral forces, torque and potential energy as a magnetic dipole with arbitrary angle moves laterally above a flat high-temperature superconductor

In the magnetic levitation system consisted of permanent magnets (PMs) and high-temperature superconductors (HTSs), the magnetization direction of the PM is often inconsistent with the c-axis of the HTS. Therefore, the interaction between the PM with an angle and the HTS should be studied to obtain the effects of the angle on the levitation properties due to the anisotropy property of the critical current density. In this paper, as the PM dipole oriented with the angle with respect to the c-axis of the HTS moves laterally above the semi-infinite HTS, the exact expressions for the lateral and vertical forces, the torque, and the total potential energy are obtained by using the advanced frozen-image model. The dependence of these physical quantities upon the angle and the initial cooling height have been systematically studied. Under the same conditions, the predicted force and torque calculations provided by the advanced frozen-image model qualitatively agree with the previous experimental and theoretical results. The study can provide some theoretical references for designing the HTS levitation system with the angle.

Analysis of structural, electrical, and levitation properties of (RE: Nd, Sm, Gd) BCO-358 superconducting ceramics prepared by a modified MPMG technique

Analysis of structural, electrical, and levitation properties of (RE: Nd, Sm, Gd) BCO-358 superconducting ceramics prepared by a modified MPMG technique

Influence of Pressure on the Critical Current and Levitation Properties of HTS Tapes

Influence of Pressure on the Critical Current and Levitation Properties of HTS Tapes

Effect of seed orientations on the crystallization characteristics and the magnetic levitation properties of single domain YBCO bulk superconductors

In this work, two groups of single domain YBCO grains with c-axis perpendicular (Pe-Y123) and parallel (Pa-Y123) to the top surface, were fabricated by the RE + 011 TSIG method under different supercooling temperature (ΔT). The effect of ΔT on the a-axis and c-axis growth rates on the surface (Ras and Rcs) and interior part (Rai and Rci) of YBCO grains were systemically investigated, and the magnetic levitation properties of single domain YBCO bulk superconductors were studied. The results indicated that the top surface morphology exhibits square shape for Pe-Y123 group bulks and rectangular shape for Pa-Y123 group bulks. All growth rates increase nearly linear with the rising ΔT. Ras and Rcs are greater than the Rai and Rci, respectively. Both Rcs and Rci are greater than Ras and Rai under the same ΔT. Pe-Y123 superconductor is of greater levitation force, while Pa-Y123 superconductor is of relatively higher guidance force. These results are very helpful for understanding the crystal growth difference between the surface and internal of the single domain YBCO bulks, and provide a new way to fabricate REBCO bulks with designed grain orientation for different applications.

The influence of temperature on levitation properties of CC-tape stacks

This article presents the study of the temperature effect on the levitation characteristics of stacks of CC-tapes from various manufacturers SuperOx, Theva and Sunam. Tapes differ in the values of the critical current density, architecture, and parameters of the metal substrate. Stacks of tapes were assembled from 12 by 12 mm square pieces of CC-tape. The number of elements in the stacks varied from 5 to 70. The dependences of the levitation force Fz (the vertical component of the force in the system permanent magnet—HTSC stack) on temperature were obtained both in zero field cooling (ZFC) and in field cooling (FC) modes. The measurements were carried out in the temperature range of 32–100 K. We have established that, down to the minimum operating temperatures, a decrease in temperature leads to a continuous increase in levitation force in ZFC mode. In FC mode, the Fz value tends to saturate after the initial increase in force. Cooling below the boiling point of liquid nitrogen up to 65 K gives a levitation force gain of 5%–10%. At the same time, cooling to 35 K gives an increase in levitation force by 7%–23%. It was found that an increase in the number of elements in the stack from 5 to 70 leads to an increase in the levitation force with a tendency to saturation for all temperatures studied. Excellent agreement between the experimental and calculated dependences of the levitation force on temperature and the number of elements in the stacks is demonstrated. Calculations show that for Sunam tapes, 90% of the levitation force is achieved with a stack thickness of 100 tapes at the boiling point of liquid nitrogen, and with 70 tapes at lower temperatures. The distributions of the magnetic field during the approach/removal of magnets, as well as the distribution of the trapped magnetic flux at different temperatures and numbers of elements in the stacks are modelled.

Modeling study on high-temperature superconducting bulk’s growth anisotropy effect on magnetization and levitation properties in applied magnetic fields

Fabricated by top-seeded melt-texture methods, high-temperature superconducting (HTS) bulk, such as YBaCuO bulk exhibits anisotropic properties of the critical current density J c spatial distribution in growth sector regions and growth sector boundaries (GSBs). It was found that the YBaCuO bulk arrangement optimization considering the J c spatial distribution above a permanent magnet guideway (PMG) enhances the levitation performance of the HTS magnetic levitation (maglev) system according to the past experiments. Therefore, from the point of view of practical applications, a theoretical model describing this HTS growth anisotropy is required to reproduce its effect on HTS maglev properties. In this study, we proposed an updated J c spatial function with an adjustment parameter to better describe HTS bulk’s growth anisotropy. Its Cartesian form is suitable for differently shaped bulk superconductors. We subsequently established a 3D simulation model of an HTS–PMG maglev system and completed the calculations of both the levitation force and decay of two different bulk arrangements above the PMG. The calculation results are consistent with the experimental results, which verifies the reliability of the 3D HTS–PMG maglev model and J c spatial function. Further, all results show that a more stable HTS levitation with a larger levitation force is generated in the case where the GSB is aligned with the longitudinal direction of the PMG’s largest magnetic field. This provides a reference for HTS maglev designs. Furthermore, the modeling can be a useful tool for optimizing the HTS–PMG maglev system for several scenarios.

Levitation properties of pre-magnetized HTS tape stacks

This study presents new results on investigation of the levitation force between a permanent magnet and pre-magnetized HTS tape stacks containing from 20 to 100 tapes of 12 mm × 12 mm. Stacks were magnetized in superconducting magnet capable of creating a field of up to 8 T and placed in a levitation force measurement system. Experimental data on levitation force value and the effect of lateral displacement on it for stacks of tapes with different values of the captured flux and thickness have been obtained. Levitation force decay during the lateral displacements above a permanent magnet was observed for different stacks.

A new type of drilling rig powered by the Meissner effect

The article considers the use of the quantum levitation property of a superconductor for the modernization of a new type of drilling rig system. The diagrams of the propulsion system of the rig, on the basis of which conclusions are made about the profitability and economic efficiency of the drilling rig, are provided. The use of the quantum levitation effect can be rationally used in drilling rigs, increasing the efficiency by 9%.

Magnetic levitation force performance of benzil added bulk MgTi0,06B2 superconductors

MgB2 superconductors can be proposed as a good candidate for Maglev systems due to their superior structural and superconducting properties. Besides, magnetic levitation and guidance force properties of these superconductors should be increased for commercial applications of Maglev systems. Therefore, the critical current density and magnetic levitation and guidance force properties of MgTi0.06B2 superconducting samples were investigated in this study, at measurement temperatures of 20 K and 25 K, depending on benzil (C14H10O2) addition in different adding amounts of 0, 1.5, 3, 4.5, 6 and 9 wt%. In addition to benzil, nanometer-sized silver particles were added to the samples in a constant ratio of 2 wt% to enhance the structural properties. The maximum critical current density values increased from 67 kA/cm2 for pure sample to 92 kA/cm2 with benzil adding amount of 3 wt% at T = 20 K, indicating an increment of 37%. In addition, the levitation force in ZFC (zero field cooling) regime and the guidance force in FC (field cooling) regime at 20 K increased at an amount of 46% and 57%, respectively, with 3% benzil addition. It can be said that the suitable amount of benzil addition as a carbon source produces additional pinning centres inside the MgTi0.06B2 and thus structural properties, critical current density and therefore, magnetic levitation properties of the samples are increased.

Levitation Force Improvement by Effective Magnetic Interaction in Two Magnetic Levitation Systems With HTS Coil and Bulks

In this article, we studied a magnetic levitation system which was composed of a high-temperature superconducting (HTS) coil, HTS bulks, and a ferromagnetic material (rail). We set two magnetic levitation systems in one ferromagnetic rail. We analyzed the levitation force depending on changing the distance between HTS coils of each direction of current flowing. As a result of comparing two poles that has current flowing through its coils in one direction and two poles that has current flowing through its coils in different directions, the model which had the coils in one direction was better. A reason for this result is discussed comparing with the magnetic flux density and the stress tensor in a ferromagnetic rail. In addition, the distance between coils was also important for the magnetic interaction. We show the tendency of levitation force obtained by changing the distance between coils in each direction of current flowing and explain the reason. In this article, it is found that a greater force can be obtained by using magnetic field interaction effectively. We optimized arrangement and magnetic pole combination and we succeeded to improve the levitation property.

Comparison of properties of a bulk HTS and a stack of HTS tapes after FC and ZFC

This paper presents the results of the analysis of properties of a high-temperature superconducting (HTS) material in two forms - HTS bulks and a stack made of a number of HTS tape layers. Stack of HTS tape is a new type of application of superconductors, which can be used instead of a convention bulk material. In this work, we study the levitation properties of HTS stack and compare it with the same characteristics of HTS bulks to find the effective way of modelling such type of HTS. Experimental measurements of the force interaction between a permanent magnet and HTS material, as well as a "trapped" magnetic field, are performed for both types of a superconductor. The HTS samples are analysed in the case of Field Cooling (FC) and Zero Field Cooling (ZFC). The aim of the research is to analyse experimental results to compose and justify mathematical models for calculation magnetic system with such types of superconductor.

The comparison of levitation and lateral force of bulk and cut-pasted bulk GdBCO samples at different temperatures

In this work, in the first time, we have investigated the levitation and lateral force properties of bulk and cut-pasted bulk GdBCO samples at different temperatures and different cooling heights (CH) to determine the effect of cut-pasted process on the magnetic levitation force behaviour. The measurements of superconducting characteristics indicated that the attractive and repulsive force values of cut-pasted GdBCO sample are slightly lesser than those of GdBCO bulk sample. The maximum repulsive and attractive force values obtained as 15.45 N and −4.56 N for GdBCO bulk and as 14.78 N and −3.92 N for cut-pasted GdBCO samples at 37 K. Although there are many fabrication methods as melt-textured growth (MTG), top seeded infiltration growth (TSIG) and TSMG to produce large HTS samples, the desired large sample size and the sample shape compatible with the superconducting magnetic bearing systems are not still sufficient for the technological applications. In this study, the performed cut-pasted process and obtained magnetic levitation force data can be using for the increment sample size and the desired sample shape in the needed different geometry and size for superconducting magnetic bearing systems.

Influence of the physical parameters on the limits of magnetic stiffness of high-Tc superconducting levitation systems

Magnetic stiffness is one of the important stability parameters of high temperature superconducting levitation systems. Till to now, great efforts have been made to understand levitation properties including flux penetration, magnetization curves, levitation force, ac susceptibilities, etc. In this paper we present a quadratic approximation method for the limit of magnetic stiffness in a high temperature superconducting levitation system based on Kim’s critical state model and Ampère law. The system is composed with a cylindrical permanent magnet (PM) and a coaxial high temperature superconductor (HTS). It is found that the limit of magnetic stiffness depends upon both the penetration history of shielding currents distribution in HTS and applied magnetic field gradients. Furthermore, the influence of the physical parameters, such as critical current density in HTS and applied magnetic field, on the limits of magnetic stiffness is investigated in detail. The obtained results display that magnetic stiffness decreases with the increasing of critical current density, since shielding currents have not penetrated into the large portion of the HTS. With the increase of applied magnetic field, the magnetic stiffness obtain a larger magnification factor. It is related to the increase of the shielding current penetration volume and the internal magnetic field in HTS.

Optical Resonators based on Casimir Forces -INVITED

The work here presented demonstrates theoretically that it is possible to create optical resonators based on levitation properties of thin films subjected to repulsive Casimir-Lifshitz forces. Our optical cavity design is made up of commonly found materials, such as silicon oxide, polystyrene or gold, with glycerol as a mediating medium, which supports high Q-factor optical modes at visible frequencies. The balance between flotation and repulsive Casimir-Lifshitz forces in the system allows the fine-tuning of the optical cavity thickness and hence its modes. Finally, we show that well-defined spectral features in the reflectivity allows by indirect means, an accurate prediction of the estimated equilibrium distance at which some part of the optical cavity arrangement levitates.

Experimental Characterization of the Temperature Influence on the Stiffness and Damping of a Field-Cooled Superconducting Magnetic Suspension

Superconducting magnetic levitation has been used in contactless mechanical components for different applications like bearings or positioning devices. This technology is currently being investigated for its potential use as a vibration isolation and thermal disconnect passive mechanism to support the focal plane array of the ESA ATHENA scientific telescope. Although it is well known that superconducting levitation properties depends on temperature, theoretical models have difficulties with complex bearing geometries or capturing inhomogeneity in material properties. In addition, experimental studies focused on the characterization of the mechanical properties of superconducting magnetic bearings are scant and mostly carried out with zero-field-cooled thrust bearing configurations. In order to increase the maturity of the technology for its potential use in space applications, further experimental research of the superconducting levitation properties at different temperatures is required. In this paper, we present the results of an experimental study of the levitation mechanical properties of a journal superconducting suspension in a high vacuum and temperatures from 90 to 12 K. Axial stiffness quadratically increases at lower temperature and linearly in the radial direction. However, the hysteresis loss factor decreases when decreasing the temperature for both axial and radial directions of displacement. These results demonstrate that the temperature influence on superconducting levitation systems is significant, and thus, mechanical engineers must consider it for design of superconducting levitation systems subjected to temperature variations.

Casimir-Lifshitz Force Based Optical Resonators.

We theoretically investigate the building of optical resonators based on the levitation properties of thin films subjected to strong repulsive Casimir-Lifshitz forces when immersed in an adequate medium and confronted with a planar substrate. We propose a design in which cavities supporting high Q-factor optical modes at visible frequencies can be achieved by means of combining commonly found materials, such as silicon oxide, polystyrene or gold, with glycerol as a mediating medium. We use the balance between flotation and repulsive Casimir-Lifshitz forces in the system to accurately tune the optical cavity thickness and hence its modes. The effects of other forces, such as electrostatic, that may come into play are also considered. Our results constitute a proof of concept that may open the route to the design of photonic architectures in environments in which dispersion forces play a substantial role and could be of particular relevance for devising novel microfluidic optical resonators.