scholarly journals Dynamic resistance measurements in a GdBCO-coated conductor

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
R Toyomoto ◽  
N Amemiya ◽  
Christopher Bumby ◽  
Rodney Badcock ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dynamic Resistance ◽  
Normal Vector ◽  
Coated Conductor ◽  
Personal Use ◽  
Perpendicular Component ◽  
Experimental Values ◽  
Dc Current ◽  
Heat Loads ◽  
The Magnetic Field

Dynamic resistance is a phenomenon which occurs when a superconducting wire carries dc transport current whilst experiencing an alternating magnetic field. This situation occurs in a range of HTS machinery applications, where dynamic resistance can lead to large parasitic heat loads and potential quench events. Here, we present dynamic resistance measurements of a 5-mm-wide Fujikura coated conductor wire at 77 K. We report experimental values obtain through varying the field angle (the angle between magnetic field and normal vector of the conductor wide-face), the dc current levels, and the magnetic field amplitude, and frequency. We show that the dynamic resistance in perpendicular magnetic field can be predicted by using a simple analytical equation. We also show that across the range of field angles measured here the dynamic resistance is dominated by the perpendicular component of the applied magnetic field. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals Dynamic resistance measurements in a GdBCO-coated conductor

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
R Toyomoto ◽  
N Amemiya ◽  
Christopher Bumby ◽  
Rodney Badcock ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dynamic Resistance ◽  
Normal Vector ◽  
Coated Conductor ◽  
Personal Use ◽  
Perpendicular Component ◽  
Experimental Values ◽  
Dc Current ◽  
Heat Loads ◽  
The Magnetic Field

Dynamic resistance is a phenomenon which occurs when a superconducting wire carries dc transport current whilst experiencing an alternating magnetic field. This situation occurs in a range of HTS machinery applications, where dynamic resistance can lead to large parasitic heat loads and potential quench events. Here, we present dynamic resistance measurements of a 5-mm-wide Fujikura coated conductor wire at 77 K. We report experimental values obtain through varying the field angle (the angle between magnetic field and normal vector of the conductor wide-face), the dc current levels, and the magnetic field amplitude, and frequency. We show that the dynamic resistance in perpendicular magnetic field can be predicted by using a simple analytical equation. We also show that across the range of field angles measured here the dynamic resistance is dominated by the perpendicular component of the applied magnetic field. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals Dynamic Resistance Measurement in a Four-Tape YBCO Stack with Various Applied Field Orientation

2021 ◽  
Author(s):  
Y Liu ◽  
Zhenan Jiang ◽  
Q Li ◽  
Christopher Bumby ◽  
Rodney Badcock ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Buffer Layers ◽  
Analytical Models ◽  
Dynamic Resistance ◽  
Normal Vector ◽  
Field Frequency ◽  
Field Orientation ◽  
Personal Use ◽  
Dc Current ◽  
The Magnetic Field

The dynamic resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on dynamic resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of dynamic resistance on field angle as well as wire Ic (B, θ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of dynamic resistance on these parameters. Finally, we compared the measured dynamic resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the dynamic resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. Ic (B, θ) influences dynamic resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals Dynamic Resistance Measurement in a Four-Tape YBCO Stack with Various Applied Field Orientation

2021 ◽  
Author(s):  
Y Liu ◽  
Zhenan Jiang ◽  
Q Li ◽  
Christopher Bumby ◽  
Rodney Badcock ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Buffer Layers ◽  
Analytical Models ◽  
Dynamic Resistance ◽  
Normal Vector ◽  
Field Frequency ◽  
Field Orientation ◽  
Personal Use ◽  
Dc Current ◽  
The Magnetic Field

The dynamic resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on dynamic resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of dynamic resistance on field angle as well as wire Ic (B, θ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of dynamic resistance on these parameters. Finally, we compared the measured dynamic resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the dynamic resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. Ic (B, θ) influences dynamic resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals Dynamic Resistance Measurement of a Four-Tape YBCO Stack in a Perpendicular Magnetic Field

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
W Zhou ◽  
Christopher Bumby ◽  
M Staines ◽  
Q Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Role ◽  
Coated Conductors ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Perpendicular Magnetic Field ◽  
Personal Use ◽  
Dc Current ◽  
The Magnetic Field ◽  
Circulating Currents

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals Dynamic Resistance Measurement of a Four-Tape YBCO Stack in a Perpendicular Magnetic Field

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
W Zhou ◽  
Christopher Bumby ◽  
M Staines ◽  
Q Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Role ◽  
Coated Conductors ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Perpendicular Magnetic Field ◽  
Personal Use ◽  
Dc Current ◽  
The Magnetic Field ◽  
Circulating Currents

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

scholarly journals The dynamic resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
W Zhou ◽  
Q Li ◽  
M Yao ◽  
J Fang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Applied Field ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Coated Conductor ◽  
Field Orientation ◽  
Ac Magnetic Field ◽  
Ybco Coated Conductor ◽  
Wide Range ◽  
Dc Current

Dynamic resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of dynamic resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ∼12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured dynamic resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the dynamic resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured dynamic resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the dynamic resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles. 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/aaa49e.

scholarly journals The dynamic resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation

2021 ◽  
Author(s):  
Zhenan Jiang ◽  
W Zhou ◽  
Q Li ◽  
M Yao ◽  
J Fang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Applied Field ◽  
Threshold Field ◽  
Dynamic Resistance ◽  
Coated Conductor ◽  
Field Orientation ◽  
Ac Magnetic Field ◽  
Ybco Coated Conductor ◽  
Wide Range ◽  
Dc Current

Dynamic resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of dynamic resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ∼12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured dynamic resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the dynamic resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured dynamic resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the dynamic resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles. 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/aaa49e.

scholarly journals Topology of Coronal Magnetic Fields: Extending the Magnetic Skeleton Using Null-like Points

Solar Physics ◽  
2020 ◽  
Vol 295 (12) ◽  
Author(s):  
Daniel T. Lee ◽  
Daniel S. Brown
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Free Field ◽  
Point Sources ◽  
Topological Features ◽  
Perpendicular Component ◽  
Definition Of ◽  
Magnetic Null ◽  
The Magnetic Field ◽  
Continuous Source

AbstractMany phenomena in the Sun’s atmosphere are magnetic in nature and study of the atmospheric magnetic field plays an important part in understanding these phenomena. Tools to study solar magnetic fields include magnetic topology and features such as magnetic null points, separatrix surfaces, and separators. The theory of these has most robustly been developed under magnetic charge topology, where the sources of the magnetic field are taken to be discrete, but observed magnetic fields are continuously distributed, and reconstructions and numerical simulations typically use continuously distributed magnetic boundary conditions. This article investigates the pitfalls in using continuous-source descriptions, particularly when null points on the $z=0$ z = 0 plane are obscured by the continuous flux distribution through, e.g., the overlap of non-point sources. The idea of null-like points on the boundary is introduced where the parallel requirement on the field $B_{\parallel }=0$ B ∥ = 0 is retained but the requirement on the perpendicular component is relaxed, i.e. $B_{\perp }\ne 0$ B ⊥ ≠ 0 . These allow the definition of separatrix-like surfaces which are shown (through use of a squashing factor) to be a class of quasi-separatrix layer, and separator-like lines which retain the x-line structure of separators. Examples are given that demonstrate that the use of null-like points can reinstate topological features that are eliminated in the transition from discrete to continuous sources, and that their inclusion in more involved cases can enhance understanding of the magnetic structure and even change the resulting conclusions. While the examples in this article use the potential approximation, the definition of null-like points is more general and may be employed in other cases such as force-free field extrapolations and MHD simulations.

VALLEY SPLITTING AND g-FACTOR IN AlAs QUANTUM WELLS

2009 ◽  
Vol 23 (12n13) ◽  
pp. 2948-2954
Author(s):  
C. A. DUARTE ◽  
G. M. GUSEV ◽  
T. E. LAMAS ◽  
A. K. BAKAROV ◽  
J.-C. PORTAL
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Quantum Confinement ◽  
Zeeman Splitting ◽  
Exchange Contribution ◽  
G Factor ◽  
Valley Splitting ◽  
Perpendicular Component ◽  
Magneto Resistance ◽  
The Magnetic Field

Here we present the results of magneto resistance measurements in tilted magnetic field and compare them with calculations. The comparison between calculated and measured spectra for the case of perpendicular fields enable us to estimate the dependence of the valley splitting as a function of the magnetic field and the total Landé g -factor (which is assumed to be independent of the magnetic field). Since both the exchange contribution to the Zeeman splitting as well as the valley splitting are properties associated with the 2D quantum confinement, they depend only on the perpendicular component of the magnetic field, while the bare Zeeman splitting depends on the total magnetic field. This information aided by the comparison between experimental and calculated gray scale maps permits to obtain separately the values of the exchange and the bare contribution to the g -factor.

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