Strongly Coupled Artificial Bulk HTS Grain Boundaries With High Critical Current Densities

Babu, N. Hari; Withnell, T.D.; Iida, K.; Cardwell, D. A.

doi:10.1109/tasc.2007.899063

Cited by 20 publications

(17 citation statements)

References 12 publications

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“…This kind of modelling framework allows the presence of the various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors to be considered, including inhomogeneous J c distributions (between top and bottom regions or between the seed and outer edge of the bulk [33,129], for example) and the presence of current limiting grain boundaries and cracks. It can also be used to assist optimization of processing techniques, such as samples with novel seed arrangements [130][131][132][133][134], as well as PFM techniques and coil design, for practical bulk superconductor applications.…”

Section: Inhomogeneities In (Re)bco Bulk Superconductorsmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

184

166

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This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialisation stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarised with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet-superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets (TFMs). Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.

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Section: Inhomogeneities In (Re)bco Bulk Superconductorsmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

184

166

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“…This modelling framework allows the presence of the various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors to be considered, including inhomogeneous J c distributions (between top and bottom regions or between the seed and outer edge of the bulk [32,33], for example) and the presence of current-limiting grain boundaries and cracks. It can be used to assist optimisation of processing techniques, such as samples with novel seed arrangements [34][35][36][37], as well as PFM techniques and pulse coil design, for practical bulk superconductor applications. Figure 13.…”

Section: Modelling Inhomogeneous Behaviourmentioning

confidence: 99%

Modelling and comparison of trapped fields in (RE)BCO bulk superconductors for activation using pulsed field magnetization

Ainslie

Fujishiro

Ujiie

et al. 2014

Supercond. Sci. Technol.

125

143

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The ability to generate a permanent, stable magnetic field unsupported by an electromotive force is fundamental to a variety of engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields of magnitude over ten times higher than the maximum field produced by conventional magnets, which is limited practically to rather less than 2 T. In this paper, two large c-axis oriented, single-grain YBCO and GdBCO bulk superconductors are magnetised by the pulsed field magnetisation (PFM) technique at temperatures of 40 and 65 K and the characteristics of the resulting trapped field profile are investigated with a view of magnetising such samples as trapped field magnets (TFMs) in-situ inside a trapped flux-type superconducting electric machine. A comparison is made between the temperatures at which the pulsed magnetic field is applied and the results have strong implications for the optimum operating temperature for TFMs in trapped fluxtype superconducting electric machines. The effects of inhomogeneities, which occur during the growth process of single-grain bulk superconductors, on the trapped field and maximum temperature rise in the sample are modelled numerically using a 3D finite-element model based on the H-formulation and implemented in Comsol Multiphysics 4.3a. The results agree qualitatively with the observed experimental results, in that inhomogeneities act to distort the trapped field profile and reduce the magnitude of the trapped field due to localised heating within the sample and preferential movement and pinning of flux lines around the growth section regions (GSRs) and growth sector boundaries (GSBs), respectively. The modelling framework will allow further investigation of various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors, including inhomogeneous J c distributions and the presence of current-limiting grain boundaries and cracks, and it can be used to assist optimisation of processing and PFM techniques for practical bulk superconductor applications.

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“…This is a common case where the GB plays a blocking or suppressing role to the flowing of the induced supercurrent when crossing the GB, as excess liquid and Y211 particles were pushed to this area during the crystal growth, creating a normal conducting barrier between two grains [8]. However, this problem can be alleviated or solved so as to obtain a clearer GB by several optimized processing methods reported in [8][9][10][11][12][13]. Next, we will present the influence of the GB coupling ratio on the total trapped flux.…”

Section: Resultsmentioning

confidence: 99%

“…As a result, this fabrication method owns several remarkable advantages such as larger-sized samples, time-saving as well as cost reduction. In view of these merits, numerous studies have concentrated on the optimization of processing, seed orientations and seed distance in order to obtain a clear grain boundary (GB) [8], thus improving the current transport capability across the GB between two adjacent grains [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%