Critical Persistent Currents in Hard Superconductors

Kim, Y. B.; Hempstead, C. F.; Strnad, A. R.

doi:10.1103/physrevlett.9.306

Cited by 1,154 publications

(443 citation statements)

References 8 publications

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“…In the limit n → ∞, (2) is equivalent to the Bean model, and for 1 << n < ∞, it corresponds to flux creep regimes. The third constitutive law, (3), first introduced by Kim [24], results from the polycrystalline nature of the material. …”

Section: Constitutive Lawsmentioning

confidence: 99%

“…In [7], the parameters J c0 and B 1 entering the constitutive laws (3) were determined by fitting the curve of first magnetization of figure 2 to an analytical expression obtained from Maxwell's equations and Kim's model [24], while the exponent n in (2) was obtained from an analysis of the frequency dependence of the field attenuation at the centre (r = 0, z = 0) of the sample. These procedures lead to the values [7] Although the results of this paper will not be compared to experimental data, we use the same values, determined at 77 K, in order to take realistic parameters.…”

Section: Model Parametersmentioning

confidence: 99%

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Field penetration into hard type-II superconducting tubes: effects of a cap, a non-superconducting joint, and non-uniform superconducting properties

Denis

Dirickx

Vanderbemden

et al. 2007

Supercond. Sci. Technol.

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Using the numerical method of Brandt (1998 Phys. Rev. B 58 6506), we study the penetration of a uniform magnetic field that is gradually applied parallel to the axis of finite type-II superconducting tubular samples with strong pinning. This study is carried out in view of designing low-frequency magnetic shields by exploiting the diamagnetic properties of type-II superconductors. First, we compare the field penetration into open and closed tubes. For long tubes (length larger than three times the outer diameter), we show that a cap weakly affects the maximum magnetic induction that can be shielded, but greatly increases the region over which the field is nearly uniform. When the length of the tube is shorter, both the maximum shieldable magnetic induction and the uniformity of the field attenuation are enhanced by closing the tube. We also show that making a hole in the cap, which is often necessary for applications, does not greatly affect the shielding properties provided the diameter of the hole is small compared to that of the tube (hole diameter smaller than a quarter of the outer tube diameter). In view of designing large size magnetic shields, superconducting tubes of finite size need to be joined together. We therefore examine in a second part how the presence of a non-superconducting joint between the tubes affects the shielding efficiency. It is shown that the effect of a joint depends upon its position along the tube axis and strongly increases with its size. Third, we study how non-uniform superconducting properties affect the shielding capabilities.

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Section: Constitutive Lawsmentioning

confidence: 99%

Section: Model Parametersmentioning

confidence: 99%

Field penetration into hard type-II superconducting tubes: effects of a cap, a non-superconducting joint, and non-uniform superconducting properties

Denis

Dirickx

Vanderbemden

et al. 2007

Supercond. Sci. Technol.

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“…2 shows the J c -B curves become flattened at low field due to very large self-field suppression effects on J c . 18 The inset shows the extrapolation of the critical current for the FHTϩOP sample to zero field I c ͑0 T, 77 K͒ based on the model proposed by Kim et al 19 where 1/I c (B)ϭB/I c (0)B 0 ϩ1/I c (0). B 0 is the characteristic field and I c (0) is the critical current at 0 T. The extrapolated I c ͑0 T, 77 K͒ for the FHTϩOP sample is 235 A, corresponding to J c (0 T,77 K)ϭ90 kA/cm 2 .…”

mentioning

confidence: 99%

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Yuan

Jiang

Cai

et al. 2004

Applied Physics Letters

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Overpressure ͑OP͒ processing otherwise fully treated, commercial Ag-sheathed multifilament (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x ͑2223͒ composite conductors increased the critical current density J c ͑0.1 T, 77 K͒ by 37% to 30.8 kA/cm 2 and the self-field J c ͑SF, 77 K͒ to 69.6 kA/cm 2 . These improvements were obtained on full-size high current conductors such that critical current I c ͑0.1 T, 77 K͒ reached 80.6 A and I c ͑SF, 77 K͒ 181.7 A, even though there was a very strong self-field suppression of I c . Estimated values for the non-self-field-limited I c and J c ͑0 T, 77 K͒ reached 235 A and 90 kA/cm 2 . Scanning electron microscopy and superconducting quantum inference device measurement revealed that OP processing effectively suppressed cracks, porosity, and the volume fraction of the Bi 2 Sr 2 Ca 1 Cu 2 O y ͑2212͒ phase, which are all major current-limiting mechanisms in present 2223 conductors.

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“…This is in contrast with exponents obtained in [9,10] where values of 0.35 were obtained. Let us recall that a value of 1 is predicted in the 3D Kim model [15], a value of 1/2 for interfacial pinning [16] and a value of 0 for the Bean model. The most general expression with an arbitrary value of the exponent has been considered by Ming et al [17] …”

Section: Direct Methodsmentioning

confidence: 99%

Magnetic flux penetration and creep in BSSCO-2223 composite ceramics

Vanderbemden

Destombes

Cloots

et al. 1998

Supercond. Sci. Technol.

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Abstract. We have experimentally investigated the magnetic flux penetration through a Bi-2223 polycrystalline superconductor synthesized by a classical solid-state reaction method. Electrical resistance, AC susceptibility, the Campbell method and magnetic flux waveform recordings have been analysed and compared in order to separate clearly intergrain and intragrain contributions. The AC susceptibility frequency dependence has been also examined at T = 77 K in a broad field range (0.01 G< B AC < 100 G). The activation energy as a function of AC applied magnetic field is found to present a pronounced minimum for an induction (8 G) corresponding to full magnetic flux penetration through the intergranular matrix.

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Critical Persistent Currents in Hard Superconductors

Cited by 1,154 publications

References 8 publications

Field penetration into hard type-II superconducting tubes: effects of a cap, a non-superconducting joint, and non-uniform superconducting properties

Field penetration into hard type-II superconducting tubes: effects of a cap, a non-superconducting joint, and non-uniform superconducting properties

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Magnetic flux penetration and creep in BSSCO-2223 composite ceramics

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