Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Masti, M.; Lehtonen, J.; Perala, R.; Mikkonen, R.; Soderlund, L.; Seppälä, P

doi:10.1088/0957-0233/16/5/007

Cited by 4 publications

(6 citation statements)

References 25 publications

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“…Comparing the t (x)J c0 (x) profile with the t (x) estimate (light grey area in figure 5(b)) obtained from the cross-section shown in figure 1, it is apparent that the values of J c0 (x) in the central filament column are systematically lower than those in the two side columns. This observation correlates well with the stressstrain pattern of the applied rolling deformations, which allows the formation of better texture in the outer columns [14].…”

Section: Resultssupporting

confidence: 80%

Comparison and analysis of Hall probe scanning, magneto-optical imaging and magnetic knife measurements of Bi-2223/Ag tape

Kòváč

Masti

Lehtonen

et al. 2005

Supercond. Sci. Technol.

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Magneto-optical (MO) imaging, Hall probe measurements and the magnetic knife method were used for sample quality studies of multi-core Bi-2223/Ag tape with a columnar 60-filament structure made by the TIRT (tape in rectangular tube) process. While the magneto-optical imaging was made at 25 K and without transport current, Hall probe and magnetic knife measurements were performed for the sample carrying a direct current at 77 K.The MO image recorded at 25 K and external field 30 mT has shown non-uniform flux distribution in the three filament columns. 2D field profiles were analysed by the finite element method assuming ideal filament homogeneity. B z (x) was computed analytically with an assumption that current density flows straight through the cross-section of the filament columns. The best agreement of computed profiles with measured ones is achieved for equal currents flowing in all filament zones. According to the magnetic knife measurements, current density is lowest in the centre column, but in this method the magnetic self-field is hardly influencing the current distribution. A better understanding of such experimental differences is obtained with 3D modelling. Three different cases of meandering transport current were studied computationally in order to explain the measured results. Finally, we discuss the advantages and drawbacks of the methods used and present how they can together produce the most complex information.

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Section: Resultssupporting

confidence: 80%

Comparison and analysis of Hall probe scanning, magneto-optical imaging and magnetic knife measurements of Bi-2223/Ag tape

Kòváč

Masti

Lehtonen

et al. 2005

Supercond. Sci. Technol.

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“…The properties of the tape, such as the J c -B-and n-B-dependencies, were well-known as they had been thoroughly investigated earlier 28 . We measured the current penetration into the sample carrying a DC current in zero external field by means of a Hall-probe mapping 29,30 . Furthermore, we measured the AC losses of the sample carrying a DC current in an AC magnetic field perpendicular to the sample width using several different values of DC current and AC field.…”

Section: The Methods Of Measurementmentioning

confidence: 99%

Ripple field losses in direct current biased superconductors: Simulations and comparison with measurements

Lahtinen

Pardo

Šouc

et al. 2014

Journal of Applied Physics

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Articles you may be interested inMicrostructure dependence of the c-axis critical current density in second-generation YBCO tapes Singular current density in the planar superconductor/normal metal/superconductor junctionIn several superconducting applications, as, for example, in some supercondcuting generators, motors, and power transmission cables, the superconductor experiences a changing magnetic field in a DC background. Simulating the losses caused by this AC ripple field is an important task from the application design point of view. In this work, we compare two formulations, the H-formulation and the minimum magnetic energy variation-formulation, based on the eddy current model (ECM) and the critical state model (CSM), respectively, for simulating ripple field losses in a DC biased coated conductor tape. Furthermore, we compare our simulation results with measurements. We investigate the frequency-dependence of the hysteresis loss predictions of the power law based ECM and verify by measurements, that in DC use, ECM clearly over-estimates the homogenization of the current density profile in the coated conductor tape: the relaxation of the local current density is not nearly as prominent in the measurement as it is in the simulation. Hence, we suggest that the power law resistivity, used as the local relation between the electric field intensity E and current density J in ECM, is not an intrinsic property of high-temperature superconductors. The difference between the models manifests itself as discrepancies in ripple field loss simulations in very low AC fields with significant DC fields or currents involved. The results also show, however, that for many practical situations, CSM and ECM are both eligible models for ripple field loss simulations. V C 2014 AIP Publishing LLC. [http://dx.

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“…This Hall sensor voltage, v H , and current transducer signal are digitized with two synchronized voltage meters. After measurement at desired spatial points, the current transducer signal is scaled back to the alternating transport current i T [8]. At all spatial points, m, sample data has N samples.…”

Section: Methodsmentioning

confidence: 99%

“…In this paper, an alternating current Hall magnetometer has been used to measure the Hall voltage signal and alternating transport current synchronously over several current cycles in a set of spatial points over a Bi-2223/Ag tape sample [8]. These measured magnetic flux density maps are compared to the calculated ones with discrete Fourier transformation (DFT) analysis.…”

Section: Introductionmentioning

confidence: 99%

Discrete Fourier transformation analysis of AC Hall sensor magnetometer measurements of high temperature superconductor tapes

Masti¹,

Lehtonen²,

Mikkonen³

2005

Supercond. Sci. Technol.

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During the last five years, the AC performance of high temperature superconductor (HTS) tapes has been under intense development due to the needs of practical applications. Previously, a system capable of measuring time dependent, spatial distribution of the magnetic flux density at a selected distance above the HTS tape has been presented. The tape can carry any cyclic current signal in the frequency range of 0-400 Hz. In this paper, a calculation model to extract information about the current densities, which create the measured magnetic flux density, is developed and used to interpret these measurements. Discrete Fourier transformation is found to provide a numerically stable method that is well suited to the interpretation of results and also for the signal noise exclusion. The third harmonic of the measured Hall voltage is seen to play an integral role in the comparison of the penetration models.

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Hall sensor magnetometer for ac characterization of high temperature superconducting tapes

Cited by 4 publications

References 25 publications

Comparison and analysis of Hall probe scanning, magneto-optical imaging and magnetic knife measurements of Bi-2223/Ag tape

Comparison and analysis of Hall probe scanning, magneto-optical imaging and magnetic knife measurements of Bi-2223/Ag tape

Ripple field losses in direct current biased superconductors: Simulations and comparison with measurements

Discrete Fourier transformation analysis of AC Hall sensor magnetometer measurements of high temperature superconductor tapes

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