Measurements of magnetic fields of levitated bulk superconductors

Yamachi, N.; Nishikawa, T.; Tomita, Masaru; Sawa, Kôichiro; Murakami, Masato

doi:10.1016/s0921-4534(02)01818-x

Cited by 5 publications

(6 citation statements)

References 5 publications

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“…The maximum trapped flux density is simulated in the median plane of the samples with models (1), (2) and (3) and on the surface with model (3). It is found that the maximum trapped flux density is in each case the largest with the Bean model, the flux creep and geometrical effects bringing additional drops of trapped flux.…”

Section: Discussionmentioning

confidence: 99%

“…Single crystals of YBa 2 Cu 3 O 7−δ containing a series of holes that are artificially drilled along a given crystallographic direction have been recently introduced in order to improve the performances of YBCO trapped field magnets [1,2,3,4,5]. For instance, it was demonstrated that the maximum trapped flux density in YBCO magnets may be enhanced in the presence of holes that favor the oxygen annealing and thus yield larger critical current densities [6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

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Modification of the trapped field in bulk high-temperature superconductors as a result of the drilling of a pattern of artificial columnar holes

Lousberg¹,

Fagnard²,

Ausloos³

et al. 2010

J. Phys.: Conf. Ser.

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Abstract. The trapped magnetic field is examined in bulk high-temperature superconductors that are artificially drilled along their c-axis. The influence of the hole pattern on the magnetization is studied and compared by means of numerical models and Hall probe mapping techniques. To this aim, we consider two bulk YBCO samples with a rectangular cross-section that are drilled each by six holes arranged either on a rectangular lattice (sample I) or on a centered rectangular lattice (sample II). For the numerical analysis, three different models are considered for calculating the trapped flux: (i), a two-dimensional (2D) Bean model neglecting demagnetizing effects and flux creep, (ii), a 2D finite-element model neglecting demagnetizing effects but incorporating magnetic relaxation in the form of an E − J power law, and, (iii), a 3D finite element analysis that takes into account both the finite height of the sample and flux creep effects. For the experimental analysis, the trapped magnetic flux density is measured above the sample surface by Hall probe mapping performed before and after the drilling process. The maximum trapped flux density in the drilled samples is found to be smaller than that in the plain samples. The smallest magnetization drop is found for sample II, with the centered rectangular lattice. This result is confirmed by the numerical models. In each sample, the relative drops that are calculated independently with the three different models are in good agreement. As observed experimentally, the magnetization drop calculated in the sample II is the smallest one and its relative value is comparable to the measured one. By contrast, the measured magnetization drop in sample (1) is much larger than that predicted by the simulations, most likely because of a change of the microstructure during the drilling process.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modification of the trapped field in bulk high-temperature superconductors as a result of the drilling of a pattern of artificial columnar holes

Lousberg¹,

Fagnard²,

Ausloos³

et al. 2010

J. Phys.: Conf. Ser.

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“…The parameters for each Hall probe mapping are (i) a spatial step of 0.5 mm and (ii) a distance between the sample top surface and the probe equal to 1 mm. The Arepoc™ HHP-MFO Hall probe has an active area of 0.01 mm 2 . In order to generate the heat flux in the sample, a 100 mA current is injected into a 1 kΩ SMD resistor (6.4 x 3.1 x 0.55 mm 3 ) stuck to the lateral surface sample with Apiezion™ M grease; the corresponding dissipated power is equal to 10 W. The sample holder (figure 2) allows the superconductor to be clamped with four small brass screws in order to maximize the exchange surface with the liquid nitrogen bath.…”

Section: Measurement Set-upmentioning

confidence: 99%

“…Bulk high temperature superconductors (HTSs) can be used in engineering applications as permanent magnets [1,2]. At present, the most promising materials are bulk (RE)BCO single domains (where RE denotes a rare earth element such as Y, Dy, Nd...), for which trapped induction values exceeding 15 T have been successfully demonstrated by various laboratories [3], Such trapped fields suggest that single-domain HTSs may replace permanent magnets in the rotor of an AC rotating machine in order to achieve a high torque [1,4].…”

Section: Introductionmentioning

confidence: 99%

Study by Hall probe mapping of the trapped flux modification produced by local heating in YBCO HTS bulks for different surface/volume ratios

Laurent

Mathieu

Mattivi

et al. 2005

Supercond. Sci. Technol.

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The aim of this report is to compare the trapped field distribution under a local heating created at the sample edge for different sample morphologies. Hall probe mappings of the magnetic induction trapped in YBCO bulk samples maintained out of thermal equilibrium were performed on YBCO bulk single domains, YBCO single domains with regularly spaced hole arrays, and YBCO superconducting foams. The capability of heat draining was quantified by two criteria: the average induction B decay and the size of the thermally affected zone caused by a local heating of the sample. Among the three investigated sample shapes, the drilled single domain displays a trapped induction which is weakly affected by the local heating while displaying a high trapped field. Finally, a simple numerical modelling of the heat flux spreading into a drilled sample is used to suggest some design rules about the hole configuration and their size.

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“…High-temperature superconductors are a new kind of superconductors which are promising materials for the permanent magnet applications [1][2][3][4][5]. Single domain bulk melt-processed RE-Ba-Cu-O has a large potential for use in permanent-magnet like engineering applications, such as magnetic bearings [6,7], and high power density rotating machines [8][9][10][11][12] because it can trap a high value of magnetic fields [13,14].…”

Section: Introductionmentioning

confidence: 99%

Influence of the inductor shape, and the magnetization processes on a trapped magnetic flux in a superconducting bulk

Gony

Linares

Lin

et al. 2014

Physica C: Superconductivity and its Applications

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6 pagesInternational audienceIn this paper, we study the form of the inductor for producing a magnetic field in a superconductor bulk by using a method of PFM (Pulsed Field Magnetization). We tested two inductors: vortex coil and systeme of three coils, where we found the best results with the systeme of three coils. After that, we presente two processes for trapping a magnetic field in the bulk: direct magnetization and successive magnetization where we found similar results

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Measurements of magnetic fields of levitated bulk superconductors

Cited by 5 publications

References 5 publications

Modification of the trapped field in bulk high-temperature superconductors as a result of the drilling of a pattern of artificial columnar holes

Modification of the trapped field in bulk high-temperature superconductors as a result of the drilling of a pattern of artificial columnar holes

Study by Hall probe mapping of the trapped flux modification produced by local heating in YBCO HTS bulks for different surface/volume ratios

Influence of the inductor shape, and the magnetization processes on a trapped magnetic flux in a superconducting bulk

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