Influence of Temperature and/or Field Dependences of the $E-J$ Power Law on Trapped Magnetic Field in Bulk YBaCuO

Abstract. In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness / diameter) ~ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (< 0.2 K across the radius of the superconductor). The time-dependence of the average temperature T(t) is found to agree well with a theoretical prediction based on the one-dimensional (1-D) Bean model, assuming a uniform temperature in the sample. A 2-D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T (r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2-D model is used to study the effect of a non-uniform distribution of critical current density J c (r, z) on the losses within the bulk superconductor.

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“…A field dependence n(B), however, can be introduced to the model, as considered, for example, in ref. [40][41][42].…”

Section: Distribution Of Ac Losses At a Constant Temperaturementioning

confidence: 99%

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Laurent¹,

Fagnard²,

Babu³

et al. 2010

Supercond. Sci. Technol.

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“…They are fixed as follows. First, the critical current density is chosen such that model (3) exponent n is taken as n ≈ 25, a typical value for YBCO bulk samples [22].…”

Section: Discussionmentioning

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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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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“…In the field dependence in Eq. 6 of superconductor index n-value [14], instead the superconductor dependent constant parameters are n 0 = n(B a = 0), n 1 = n(B a ˃˃ B 0 ), B 0 and β.…”

Section: Superconductor Index N-value Dissipation Lossmentioning

confidence: 99%

A compactly integrated cooling system of a combination dual 1.5-MW HTS motors for electric propulsion

Le¹,

Kim²,

Hyeon³

et al. 2016

Progress in Superconductivity and Cryogenics

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The high temperature superconducting (HTS) contra-rotating propulsion (CRP) systems comprise two coaxial propellers sited on behind the other and rotate in opposite directions. They have the hydrodynamic advantage of recovering the slipstream rotational energy which would otherwise be lost to a conventional single-screw system. However, the cooling systems used for HTS CRP system need a high cooling power enough to maintain a low temperature of 2G HTS material operating at liquid neon (LNe) temperature (24.5 -27 K). In this paper, a single thermo-syphon cooling approach using a Gifford-McMahon (G-M) cryo-cooler is presented. First, an optimal thermal design of a 1.5 MW HTS motor was conducted varying to different types of commercial 2G HTS tapes. Then, a mono-cryogenic cooling system for an integration of two 1.5 MW HTS motors will be designed and analyzed. Finally, the 3D finite element analysis (FEA) simulation of thermal characteristics was also performed.

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Influence of Temperature and/or Field Dependences of the $E-J$ Power Law on Trapped Magnetic Field in Bulk YBaCuO

Cited by 83 publications

References 7 publications

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

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

A compactly integrated cooling system of a combination dual 1.5-MW HTS motors for electric propulsion

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