Bulk HTSC Research Articles

Levitation or suspension: Which one is better for the heavy-load HTS maglev transportation

Because of the limitation of permanent magnet (PM), the efficient of bulk high-[Formula: see text] superconductor (HTSC) in a high-[Formula: see text] superconducting (HTS) maglev system is not very high. It is better to magnetize the bulk HTSC with a high trapped field to increase the force density. The different application type of magnetized bulk HTSC in a maglev system, namely, levitation or suspension type, will bring quite different operation performance. This paper discusses the influence of application type on operation performance of magnetized bulk HTSC by experiments and simulations. From the discussion, it can be found which application type is better for the heavy-load HTS maglev system.

Crystalline phase transition information induced by high temperature susceptibility transformations in bulk PMP-YBCO superconductor growth in-situ

The dynamic susceptibility transformations of bulk HTSC PMP-YBCO growth have been investigated from 200°C up to 1060°C by the Faraday Balance in-situ. It revealed that the crystalline phase transitions of bulk PMP-YBCO growth in process. A new discovery of Y123 phase pre-formed then melted in heating stage has been found. It also discovered that Y123 crystal solidification started at 1004°C in cooling stage. Before Y123 solidification the liquid phase CuO change to Cu2O reciprocally as well as the copper ion valence changed between divalent Cu2+ and trivalent Cu1+ each other. It was essential to keep quantities of CuO phase instead of the Cu2O for Y123 crystal solidification.

Development of a field measurement system for the Bulk HTSC SAU

To realize a short-period strong-field undulator, we proposed a high temperature superconducting bulk staggered array undulator (Bulk HTSC SAU) and proceeded proof of principle experiments and numerical studies. We have succeeded to generate periodic transverse magnetic fields whose strength was controlled by an external solenoid field. At the same time, we revealed a problem; at both ends of undulator, field distribution is substantially distorted. We proposed several approaches of field correction. To verify the effectiveness of these field correction methods, it is necessary to measure the magnetic field distribution precisely, not only inside of the undulator but also both ends. For this purpose, we developed a rotary measurement system to measure the magnetic field distribution at the end of the undulator. Multiple Hall sensors are placed on a circuit board at equal intervals from the centre of the board. By rotating and moving the board, the probe can measure axial field in 3D space on the undulator ends. In this paper, we deliver specifics of the system.

Low-Temperature Operation of a Bulk HTSC Staggered Array Undulator

A use of bulk high-temperature superconductors (HTSs) for an undulator is attractive since a high magnetic field can be generated at low-temperatures. While potential for generation of the high magnetic field is high, in-situ magnetization of the bulk HTSs for periodic field generation is challenging issue. Recently, we proposed a new type of undulator using bulk high-Tc superconductors (HTS) and a solenoid magnet. The undulator, named Bulk HTSC staggered array undulator (Bulk HTSC SAU), consists of a stacked array of bulk HTSs and copper insulators and a solenoid magnet. A proof of principle experiment at 77 K using liquid nitrogen has been carried out. The estimated performance at about 30 K was estimated using results of property measurements for the HTS used for the Bulk HTSC SAU. The expected undulator peak field reaches to 1.08 T for undulator period length of 9.9 mm for the undulator gap of 4.0 mm. This performance is about 2 times higher than that of existing technologies.

Conceptual design of a novel insertion device using bulk superconducting magnet

An undulator or a wiggler with a strong magnetic field will play an important role in future synchrotron light sources, free electron lasers, and linear colliders. We proposed the bulk high critical temperature superconductor staggered array undulator (Bulk HTSC SAU) in order to generate a strong periodic field. The Bulk HTSC SAU consists of stacked bulk high-Tc superconductors (HTSs) and a solenoid magnet which is used to magnetize the bulk HTSs. A periodic magnetic field was produced and controlled using a prototype of the Bulk HTSC SAU using 11 pairs of REBaCuO bulk HTSs at 77K. The expected performance at low temperatures around 20K is calculated using a loop current model.

Influence of Maglev Force Relaxation on Hysteresis of Bulk HTSC Above the NdFeB Guideway at Different Lateral Displacements

After the maglev force (both levitation and guidance forces) relaxation property of a high-temperature superconductor (HTS) above a permanent-magnet guideway (PMG) was studied experimentally, the HTS bulk was horizontally moved in the lateral direction with different displacements above the permanent-magnet guideway. Both levitation and guidance force curves with lateral displacement were obtained by a SCML-2 measurement system synchronously. It was found that the levitation force hysteresis after relaxation was reduced compared to the case without relaxation, while the guidance force hysteresis curve almost did not change. This study provided a scientific analysis for the practical application of the bulk HTS.

High-efficiency and low-cost permanent magnet guideway consideration forhigh-Tc superconducting Maglev vehicle practical application

In order to improve the cost performance of the presenthigh-Tc superconducting (HTS) Maglev vehicle system for practical application, the multi-polepermanent magnet guideway (PMG) concept was introduced. A well-known double-poleHalbach PMG was chosen as a representative of multi-pole PMGs to compare withtraditional monopole PMGs from the point of view of levitation efficiency and cost.Experimental results show that YBCO bulks above the double-pole Halbach PMG canexhibit better load capability and guidance performance as well as dynamics stability atthe applied working height between the bulk HTSC and the PMG due to a more reasonablemagnetic field distribution at the working range of bulk HTSC. Furthermore, thedouble-pole PMG configuration can play a more important role in improving guidanceperformance due to the potential-well field configuration. By comparing with former‘century’ PMGs, the double-pole Halbach PMG shows another remarkable advantage inreducing the cost of levitation. As another necessary issue, magnetic field homogeneityand the corresponding magnetic drag force of a double-pole Halbach PMG hasbeen considered by experiment in spite of the above highlights. Synthetically,the multi-pole Halbach PMG design is concluded to be one important choice forfuture HTS Maglev vehicle applications because of its high efficiency and low cost.

Method to reduce levitation force decay of the bulk HTSC above the NdFeB guideway dueto lateral movement

A magnetic levitation vehicle using bulkhigh-Tc superconductors (HTSC) is considered as a promising transportation type thanks to itslateral inherent stability, but previous studies have found that the levitation force (LF)decays due to lateral movement. In this paper, a pre-load method is presented to reduce theLF decay, and the experimental results indicate that this method is very applicable insupressing this decay in spite of the applied field and material property of the bulkHTSC, and this effect can be ascribed to the reduction of the hysteresis loss inthe bulk HTSC, i.e. more trapped magnetic flux after the pre-load case. In theend, experimental results indicate that the Halbach PMG has an advantage toreduce the cost of the PMG, but its rate of LF decay is also larger due to lateralmovement

Processing and applications of bulk HTSC

The author has been emphasizing the importance of adopting refrigerators to keep the superconductivity instead of using cryogen such as liquid nitrogen, since the handling of cryogen requires complicated skills and does not fit to the widespread industries. An intense field of 5.2T has been obtained through the studies on the pulsed field magnetization process operated at 28K. Several kinds of practical applications, for instance, the magnetron sputtering cathodes, the nuclear magnetic resonance NMR equipments, and magnetic separation systems, and so on are under way with use of the melt-processed large grain bulk magnets and cryo-coolers.

Interplay between correlated and uncorrelated disorder in bulk HTSC materials with surface gold ion implantation

The interplay between correlated and uncorrelated disorder in bulk HTSC materials with gold ion surface implantation has been studied in two different temperature regions: the low-temperature range dominated by uncorrelated pinning and the high-temperature range dominated by vortex localization. The comparison with point-like uncorrelated disorder produced by low-energy proton helped to find the boundary between such regions. For what concerns the high-temperature region the possibility to obtain vortex localization as well as Jc enhancements by means of gold ion surface irradiations has been experimentally demonstrated.

Crystal growth of bulk high-Tc superconducting oxide materials

Abstract The growth of single crystals and highly oriented polycrystals of bulk high critical temperature ( T c ) superconducting (HTSC) materials is reviewed. Steady progress continues to improve the critical current density of polycrystals and the size and crystallinity of single crystals in HTSC materials using various solidification processes. In this article, advances in solidification processing, the understanding of the growth mechanism and promising new developments in bulk HTSC crystals are discussed. In particular, we describe the recent progress of crystal growth research on REBa 2 Cu 3 O 7− δ (RE, rare earth), the most widely studied HTSC material. © 1997 Elsevier Science S.A.

Evaluation of levitation and suspension forces of a bulk HTSC in microgravity experiments

Levitation and suspension forces between a permanent magnet and a bulk high T c superconductor are examined in microgravity experiments. Different experimental results are obtained for a melt processed and a sintered Y-Ba-Cu-O samples. Stable equilibrium of the melt processed sample is discussed from view points of pinning effect.

Numerical evaluation of levitation force of HTSC flywheel

Levitation force between permanent magnets and high-T/sub c/ superconductors (HTSC's) is evaluated numerically based on the critical state model. The bulk HTSC is approximated to a thin plate multilayer model from its anisotropic structure. The thin plate eddy current code with the finite element method is applied to the analysis of the HTSC flywheel, where ring magnets and the HTSC are arranged in triple concentric circles. The size and the combination of the magnets are examined to obtain the large levitation force. It is shown that the levitation force of the HTSC flywheel depends strongly on the magnetic field configuration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Power dissipation and thermal relaxation in high temperature superconductors

Abstract The hysteresis of the normalized dynamic resistance r(dJ/dt,J)t=R(dJ/dt,J)t/Rn as determined from the irreversible J-V characteristics taken out at constant reduced temperatures t=T/Tco by varying the rate of the transport current density dJ/dt has been used to study the nonequilibrium resistive state in bulk HTSC. From the observed correlations with the sample's morphology it was concluded that the internal overheating is firmly localized at the grain boundary interfaces thus resulting in further thermal release to the superconducting grains.