Time-varying magnetic field induced electric field across a current-transporting type-II superconducting loop: beyond dynamic resistance effect

2021 ◽  
Author(s):  
Jianzhao Geng ◽  
Justin McRobbie Brooks ◽  
Chris W Bumby ◽  
Rodney Alan Badcock
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Element Model ◽  
Transport Current ◽  
Dynamic Resistance ◽  
Time Varying ◽  
Type Ii ◽  
Analytical Formulae ◽  
Superconducting Loop ◽  
A Current

Abstract The emergence of a potential drop across a current-transporting type-II superconducting loop under a perpendicular oscillating magnetic field is revealed. We have derived analytical formulae to describe the effect under DC transport current in 1D, based on Bean’s critical state model. The analytical formulae are verified by a finite element model. To exploit this effect, we have developed a transformer-like ‘resistive switch’, and experimentally observed a switching effect. This work demonstrates a physically important general insight of the interaction between DC transport currents and time-varying magnetic fields in type-II superconducting loops, which extends beyond the well-known ‘dynamic resistance’ effect. It also provides a useful view on the interaction between a “transport-current” and a “screening-current” in the superconductor. The resulting demonstrated switch has the potential to be used in a variety of applications including superconducting rectifiers, fault current limiters, and superconducting magnetic energy storages.

Magnetic Field Evaluation of a Thin Type-II Superconducting Circular Washer Carrying a Radial Transport Current

2014 ◽  
Vol 24 (2) ◽  
pp. 117-120 ◽  
Author(s):  
Ali A. Babaei-Brojeny ◽  
Mohammad Karimi ◽  
Navid Barani-Lonbani ◽  
Mohsen Maddahali
Keyword(s):  
Magnetic Field ◽  
Field Evaluation ◽  
Transport Current ◽  
Type Ii ◽  
Radial Transport

Self-similar resistive decay of a current sheet in a compressible plasma

1979 ◽  
Vol 22 (2) ◽  
pp. 289-302 ◽  
Author(s):  
Keith B. Kirkland ◽  
Bengt U. ö. Sonnerup
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Interplanetary Space ◽  
Magnetic Energy ◽  
Flow Direction ◽  
Inertia Effects ◽  
Compressible Plasma ◽  
Earth Magnetic Field ◽  
Self Similar ◽  
A Current

Self-similar solutions of the magnetogasynamic equations are derived which describe the resistive decay of a plane current sheet in a compressible plasma. Such current sheets are thought to provide the magnetic energy storage in solar flares. They also occur at the boundaries between regions containing different magnetic-field directions in interplanetary space, and at the interface between the solar wing and the earth' magnetic field. It is shown that the resistive decay of a current sheet in a compressible plasma must involve plasma motion. The convective effects associated with this motion are incorporated in the analysis; the inertia effects are not. The electrical and thermal conductivities are taken to be constant, but the analysis may easily be generalized to include realistic temperature and magnetic field dependences of these quantities. Radiative and viscous terms are not included. The ordinary differential equations resulting from the similarity hypothesis are solved numerically, yielding curves of the plasma density, temperature, and velocity, as well as of the magnetic and induced electric fields, as functions of the similarity variable. The non-dimensional groups of importance are: y, the ratio of specific heats at constant pressure and constant volume; Kx, the ratio of thermal to resistive diffusivity; β∞, the ratio of plasma pressure to magnetic pressure at large distances from the current sheet. The first of these ratios is kept constant and equal to 5/3, corresponding to a monoatomic gas. The behaviour of the solution when the other two ratios are varied is investigated. The plasma velocity at large distances from the current sheet does not vanish in these solutions. It is always directed toward the sheet. However, when the diffusivity ratio K∞ is small, plasma flow away from the centre of the sheet also occurs in two narrow regions, one on each side of the centre. As a result of the reversals in the flow direction, the density then displays a relative minimum at the centre of the sheet with two outward travelling maxima adjacent to it. The plasma temperature at the centre of the sheet becomes very large for small K∞ and β∞ The expansion of the sheet becomes explosive and inertia effects can no longer be neglected. The physical meaning of these results is discussed and directions for further research are outlined.

scholarly journals Dynamic resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
R Toyomoto ◽  
N Amemiya ◽  
X Zhang ◽  
Christopher Bumby
Keyword(s):  
Magnetic Field ◽  
Critical Currents ◽  
Transport Current ◽  
Field Amplitude ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Coated Conductor ◽  
Flux Flow ◽  
Wide Range ◽  
Perpendicular Field

Superconducting high-Tc coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'dynamic resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of dynamic resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the dynamic resistance in perpendicular field. This approach implies a linear relationship between dynamic resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC resistance includes an additional nonlinear term which is due to flux-flow resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the dynamic resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aa54e5.

On the distribution of the magnetic field of the transport current in type-II superconductor

1979 ◽  
Vol 51 (2) ◽  
pp. K117-K119 ◽  
Author(s):  
N. Alekseevsky ◽  
E. Krasnopiorov ◽  
E. Trojnar ◽  
A. J. Zaleski
Keyword(s):  
Magnetic Field ◽  
Transport Current ◽  
Type Ii ◽  
Type Ii Superconductor ◽  
The Magnetic Field

scholarly journals Cosmic Magnetic Fields and Superconducting Strings

1990 ◽  
Vol 140 ◽  
pp. 507-512 ◽  
Author(s):  
Christopher Thompson
Keyword(s):  
Magnetic Field ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cosmic Ray ◽  
String Model ◽  
Maximum Energy ◽  
Superconducting Loop ◽  
Field Lines ◽  
The Magnetic Field ◽  
A Current

A cosmic magnetic field may play a significant role in the formation of galaxies and large scale structure. In particular, a fossil field of present strength ~ 10−9 Gauss is an essential ingredient in the superconducting string model of galaxy formation (Ostriker, Thompson and Witten 1986 (OTW); Thompson 1988a). We discuss the mechanism by which a current is induced on a superconducting string, including recent work on the reconnection of magnetic field lines near the string (Kulsrud and Thompson 1989). A substantial amount of baryonic plasma is trapped on the magnetic field lines which close around the string. The current on a loop almost certainly does not undergo exponential dynamo amplification; an oscillating superconducting loop emits a relativistic MHD wind (Thompson 1988a). Decaying superconducting loops fill most of the intergalactic medium with a relativistic, magnetized fluid. In this model, the gas between galaxies is highly clumped and strongly magnetized, the field strength approaching 1 μG. The maximum energy of cosmic ray protons accelerated at string-driven shocks is ~ 1020 eV (Madau and Thompson 1989).

scholarly journals Dynamic resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
R Toyomoto ◽  
N Amemiya ◽  
X Zhang ◽  
Christopher Bumby
Keyword(s):  
Magnetic Field ◽  
Critical Currents ◽  
Transport Current ◽  
Field Amplitude ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Coated Conductor ◽  
Flux Flow ◽  
Wide Range ◽  
Perpendicular Field

Superconducting high-Tc coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'dynamic resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of dynamic resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the dynamic resistance in perpendicular field. This approach implies a linear relationship between dynamic resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC resistance includes an additional nonlinear term which is due to flux-flow resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the dynamic resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aa54e5.

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