The elastic regime of vortices in superconducting YBCO and multilayer YBCO/PrBCO films

Seow, W. S.; Johnson, J. D.; Kumar, Deepak; Somekh, R.E.; Walker, Denise S.; Campbell, A.M.

doi:10.1016/0921-4534(94)02350-6

Cited by 12 publications

(9 citation statements)

References 45 publications

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“…The method is based on the force-displacement curve of the flux lines [8,9]. When a force is applied to the flux lines they move elastically for a short distance and then, as they become unpinned, the force becomes a constant frictional force.…”

Section: Theorymentioning

confidence: 99%

A new method of determining the critical state in superconductors

Campbell¹

2007

Supercond. Sci. Technol.

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A new numerical method for solving the critical state, based on the force–displacement curve of the flux lines, is described. The equation can be expressed in terms of the vector potential and can be solved by commercial finite element programs. It gives the critical state directly as a first approximation but a flux flow resistivity can easily be added. It avoids some of the numerical problems that occur if an E–J curve of the form is used with large values of n. It is particularly advantageous for problems involving trapped flux where a power law leads to decay at a rate dependent on the power assumed and the very low electric fields mean that the E–J curve is probably exponential. The flux flow resistivity can be included and since the relevant power law is 1/n rather than n the solutions are more stable. Multiphysics packages, such as FlexPDE, which allow simultaneous equations to be solved, can find the temperature distribution by adding the heat flow equation.

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Section: Theorymentioning

confidence: 99%

A new method of determining the critical state in superconductors

Campbell¹

2007

Supercond. Sci. Technol.

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“…In the case of B d B ac the compressional modulus c 11 should be applied, which for B B c1 is material independent; c 11 ≈ B 2 /µ 0 where B 2 ≈ B 2 d + B 2 a . The Labusch parameter characterizes the steepness of the potential wells for the flux lines (Seow et al 1995). It is defined as the mean value of the second derivative of the potential energy U l ascribed to the flux line of unit length in the field of pinning forces:…”

Section: Reversible Screeningmentioning

confidence: 99%

Characterization of high-temperature superconductors by AC susceptibility measurements

Gömöry

1997

Supercond. Sci. Technol.

290

197

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A magnetic field harmonically varying in time (to probe the sample) and a lock-in technique (to register the sample response sensed by a pickup coil) are widely used for characterizing superconductors. Measuring the temperature dependence of the complex AC susceptibility is the most common procedure of this type. This paper reviews these techniques, introducing in addition the complex AC susceptibility, the so-called 'wide-band AC susceptibility'. The latter quantity refers to the magnetic flux and often offers an easier meeting between theory and experiment. Starting from models for linear flux diffusion, reversible screening, volume and surface flux pinning and the intermediate regime in a type II superconductor, the expressions for the complex AC susceptibility in different cases are presented and compared with those derived for the wide-band AC susceptibility. Derivation of the basic physical properties of high-T c superconducting materials from the AC data (resistivity, critical temperatures and fields, London and Campbell penetration depths, critical current density, granularity and content of superconducting phase, irreversibility line, pinning potential) is then thoroughly discussed.

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“…An approach developed by A. M. Campbell in 2007 [7], based on the force-displacement curve of magnetic flux in HTS [8,9], has been adopted in the present model. This approach solves directly the critical state, in which J = J c wherever magnetic flux penetrates the sample.…”

Section: Methodsmentioning

confidence: 99%