Evaluation of Pulsed-Field Magnetization of a Bulk Superconductor With Small Holes

Yokoyama, K.; Oka, Tetsuo; Kondo, N.; Hosaka, Sumio

doi:10.1109/tasc.2013.2237934

Cited by 5 publications

(6 citation statements)

References 12 publications

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“…The drilling of holes in the sintered powder before the crystal growth [187][188][189] has been proposed as a method to improve the processing of single grain bulk HTS materials, which offers a larger surface area for oxygen diffusion, enabling a higher oxygen content and a reduction in the number of macrocracks formed during oxygen annealing [190]. The mechanical resistance of the TFM can be increased by impregnating the holes with a resin [2,189] and research has also been carried out investigating the role of other filler materials, such as solder [191], copper [192] and soft ferromagnetic powder [190], for which the experimental results suggest that all of these techniques can contribute to an increased trapped field and/or flux.…”

Section: Improved Thermal Conductivity Composite Structuresmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

181

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: Improved Thermal Conductivity Composite Structuresmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

181

166

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“…We have proposed to supply the magnetic flux in the bulk by boring small holes in part of the sample [15], [16]. Since superconductivity was decreased artificially in the holed portion, the magnetic flux went through the bulk without generating heat, and consequently, the trapped field was increased for lower applied fields.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the Trapped Field Performance of a Holed Superconducting Bulk Magnet

Yokoyama

Igarashi

Togasaki

et al. 2015

IEEE Trans. Appl. Supercond.

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Our goal is to generate a strong magnetic field using a REBCO bulk superconductor activated by pulsed field magnetization (PFM) for industrial application using the bulk magnet. As the diameter of the material increases and its critical current density rises, magnetic field trapping by PFM is difficult due to the strong magnetic shield. We have proposed a holed superconducting bulk magnet to improve the trapped field performance in large-size and high-J c bulk material. Magnetic flux can be supplied efficiently by reducing superconductivity in the portion with holes artificially. To confirm the validity of the proposed method, an experiment, in which a single pulsed field was applied with changing amplitude of the magnetic field and temperature, was carried out using a GdBCO bulk superconductor with four small holes. Although the magnetic flux penetrated at a lower applied field, there was a problem in that the maximum trapped field and the total magnetic flux decreased. In this paper, the size and number of holes were optimized to manage both the increase in the trapped field and easy flux penetration. A hole 1mm in diameter was drilled to half of depth of the thickness at the rim of a sample after investigating the magnetization characteristic of a GdBCO bulk 60 mm in diameter and 20 mm thick. A trapped field performance was evaluated in the sample, and afterwards, the hole was bored completely to the full depth. Then, the same experiment was carried out. The trapped field for a single hole was improved compared to the four holes, and it was confirmed that the 1-mm-diameter hole did not degrade the magnetization performance.Index Terms-Pulsed field magnetization, small hole, superconducting bulk magnet, trapped field performance. 1051-8223

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“…After this, an original material, a 1-mm-diameter hole sample, and a 2-mm-diameter hole sample are called ''case 0,'' ''case 1,'' and ''case 2,'' respectively. A sample with four 2-mm-diameter holes used in our previous study [13] is called ''case 3.'' in hole diameter at 20 K, while a decrease in the trapped flux was hardly seen probably because the absolute value was small at 40 K. Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Then, several methods of improving the PFM process [6][7][8] and adding mechanical processing to a bulk [9][10][11][12] were proposed to enhance a trapped field. We proposed intentionally weakening the magnetic shield in part of the sample by drilling small holes and supplying the magnetic flux in the bulk without generating heat; consequently, the trapped field was improved [13]. To investigate the validity of our proposed method, four 2-mm-diameter holes were drilled in a growth sector region (GSR) of a GdBCO bulk 60 mm in diameter and 20 mm thick, and a single pulsed field was applied with varying amplitudes and temperatures.…”

Section: Introductionmentioning

confidence: 99%