Hall probe mapping of melt processed superconductors with artificial holes

Haindl, S.; Hengstberger, F.; Weber, H. W.; Meslin, S.; Noudem, Jacques; Chaud, X.

doi:10.1088/0953-2048/19/1/018

Cited by 20 publications

(19 citation statements)

References 15 publications

(17 reference statements)

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“…The distribution of magnetic flux density above the surface of the SC/FM hybrid structure was investigated by Hall probe mapping [37,38]. The vertical component of magnetic flux density above the magnetized sample is mapped with a miniature Hall probe (AREPOC AXIS-3H) controlled by a XYZ micropositioning stage.…”

Section: Methodsmentioning

confidence: 99%

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

Philippe

Ainslie

Wera

et al. 2015

Supercond. Sci. Technol.

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Bulk, high temperature superconductors have significant potential for use as powerful permanent magnets in a variety of practical applications due to their ability to trap record magnetic fields. In this paper, soft ferromagnetic sections are combined with a bulk, large grain Y-Ba-Cu-O (YBCO) high temperature superconductor to form superconductor/ferromagnet (SC/FM) hybrid structures. We study how the ferromagnetic sections influence the shape of the profile of the trapped magnetic induction at the surface of each structure and report the surface magnetic flux density measured by Hall probe mapping. These configurations have been modelled using a 2D axisymmetric finite element method based on the H-formulation and the results show excellent qualitative and quantitative agreement with the experimental measurements. The model has also been used to study the magnetic flux distribution and predict the behaviour for other constitutive laws and geometries. The results show that the ferromagnetic material acts as a magnetic shield, but the flux density and its gradient are enhanced on the face opposite to the ferromagnet. The thickness and saturation magnetization of the ferromagnetic material are important and a characteristic ferromagnet thickness d* is derived: below d*, saturation of the ferromagnet occurs, and above d*, a weak thicknessdependence is observed. The influence of the ferromagnet is observed even if its saturation magnetization is lower than the trapped flux density of the superconductor. Conversely, thin ferromagnetic discs can be driven to full saturation even though the outer magnetic field is much smaller than their saturation magnetization. [5,6]) is well beyond the saturation magnetization of conventional ferromagnets. This makes them extremely promising as a competing technology for traditional permanent magnets in various applications [7][8][9][10]. The combination of ferromagnetic and superconducting materials can enhance the performance of the superconductor [11,12] and even lead to new applications [13]. Large grain, bulk superconductors are often used in applications that incorporate ferromagnetic materials, such as in motors and generators [14,15]. Ferromagnets can also increase the force in levitation systems [16,17] and close the magnetic circuit, which improves the available flux produced by bulk superconductors [18]. Similarly, ferromagnetic materials are used as sheaths around multifilament wires and tapes [19,20] or as magnetic flux diverters to modify the flux distribution around tapes and superconducting coil magnets [21][22][23][24][25][26][27][28]; thereby improving their electrical properties (i.e. increasing the critical current and reducing AC losses).

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Section: Methodsmentioning

confidence: 99%

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

Philippe

Ainslie

Wera

et al. 2015

Supercond. Sci. Technol.

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“…5 Associated measurement and characterization methods by both destructive and non-destructive techniques have developed naturally as the ability to melt process these materials has evolved. Of these, the most popular methods have tended to focus on local measurements of the flux density by scanning a miniature Hall probe above the top surface of the sample, either after full magnetization of the sample by a field cooling technique [6][7][8] or by using a small permanent magnet moved simultaneously with the Hall probe (the so-called "magnetoscan" technique). 9 Such measurement techniques have provided valuable information about current distribution and characteristics in the vicinity of the surface of the sample, although they are significantly less sensitive to the inner, bulk critical current density.…”

Section: Introductionmentioning

confidence: 99%

A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

Egan

Philippe

Wera

et al. 2015

Review of Scientific Instruments

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Articles you may be interested inCompression of a magnetic flux in the intergrain medium of a YBa2Cu3O7 granular superconductor from magnetic and magnetoresistive measurements J. Appl. Phys. 110, 093918 (2011) We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm 3 ) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within userdetermined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m 2 (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K). C 2015 AIP Publishing LLC. [http://dx

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“…Recently, bulk HTS cylinders with artificial columnar holes have been synthesized to enhance the chemical, thermal, and mechanical properties of HTS [7,28,29,30].…”

Section: Introductionmentioning

confidence: 99%

Measurement of the magnetic field inside the holes of a drilled bulk high-T_csuperconductor

Lousberg

Fagnard

Noudem

et al. 2009

Supercond. Sci. Technol.

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Abstract.We use macroscopic holes drilled in a bulk YBCO superconductor to probe its magnetic properties in the volume of the sample. The sample is subjected to an AC magnetic flux with a density ranging from 30 mT to 130 mT and the flux in the superconductor is probed by miniature coils inserted in the holes. In a given hole, three different penetration regimes can be observed: (i) the shielded regime, where no magnetic flux threads the hole; (ii) the gradual penetration regime, where the waveform of the magnetic field has a clipped sine shape whose fundamental component scales with the applied field; and (iii) the flux concentration regime, where the waveform of the magnetic field is nearly a sine wave, with an amplitude exceeding that of the applied field by up to a factor of two. The distribution of the penetration regimes in the holes is compared with that of the magnetic flux density at the top and bottom surfaces of the sample, and is interpreted with the help of optical polarized light micrographs of these surfaces. We show that the measurement of the magnetic field inside the holes Measurement of the magnetic field inside the holes of a drilled bulk HTS 2 can be used as a local characterization of the bulk magnetic properties of the sample.

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Hall probe mapping of melt processed superconductors with artificial holes

Cited by 20 publications

References 15 publications

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

Measurement of the magnetic field inside the holes of a drilled bulk high-T_csuperconductor

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Hall probe mapping of melt processed superconductors with artificial holes

Cited by 20 publications

References 15 publications

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

Measurement of the magnetic field inside the holes of a drilled bulk high-Tcsuperconductor

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Measurement of the magnetic field inside the holes of a drilled bulk high-T_csuperconductor