Magnetic shielding properties of a superconducting hollow cylinder containing slits: modelling and experiment

Fagnard, Jean-François; Elschner, S.; Hobl, A.; Böck, J.; Vanderheyden, Benoît; Vanderbemden, Philippe

doi:10.1088/0953-2048/25/10/104006

Cited by 20 publications

(9 citation statements)

References 38 publications

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“…In a superconducting material, the passive magnetic shielding effect arises from induced macroscopic shielding current loops flowing along the outer perimeter of the sample. This feature makes shielding properties highly sensitive to the presence of slits and non-superconducting joints [21][22][23]. Several high-T c materials are strong candidates for passive shielding: (i) Bi-based cuprates, which can be manufactured in the form of thick tubes [14,24] and large vessels [25], (ii) MgB 2, which can be produced in long tubes [26] and largesize cups [27,28], (iii) melt-textured (RE)Ba 2 Cu 3 O 7 (RE denotes a rare earth element Y, Gd, etc) [29], which allows efficient high-field shielding to be achieved above 20 K [30,31].…”

Section: Introductionmentioning

confidence: 99%

Magnetic shielding of various geometries of bulk semi-closed superconducting cylinders subjected to axial and transverse fields

Fagnard

Vanderheyden

Pardo

et al. 2019

Supercond. Sci. Technol.

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We consider the properties of bulk superconductors to be used as low-frequency passive magnetic shields. Although remarkable shielding properties have been recently achieved using high-temperature superconductors of various kinds, one current issue is to assemble medium-size superconducting parts to obtain large superconducting volumes. The aim of the present work is to understand how hollow, semi-closed superconductors can be combined to improve the shielding properties over sizeable volumes. In axisymmetric superconducting geometries subjected to an axial field, 2D modelling can be used to understand important features of the shielding properties. When finite-size superconductors are subjected to a transverse field, 3D modelling must be used. In this work, we use 3D finite-element modelling with an A-f formulation to investigate various geometries in which a tube is closed by a superconducting element shaped like a disk, a cup, or another cup-shaped superconductor that is coaxial with the first. The simulations help in revealing the most performant configurations to use as a function of the geometry of the applied field. Under an axial field, the type of closing is found to be irrelevant and the key ingredient to improve the shielding factor is to reduce the average field in the opening plane, e.g. by using a thicker superconductor near the open end. Under a transverse field, the difference between the shielding properties arise from the different routes taken by flux lines to penetrate the shield. In particular, the presence of flux lines channelled through the gap between a tube and a cup-shaped sample surrounding the tube are detrimental to the shielding properties. The configurations where the tube surrounds the cup-shaped sample are found to yield much higher shielding factors, whose field dependence is further improved when the tube extends slightly beyond the end of the cup. The values of the shielding factors that can be reached under a transverse field of low amplitude are discussed by comparing them to those predicted for an ideal perfectly diamagnetic superconductor of similar dimensions.

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Section: Introductionmentioning

confidence: 99%

Magnetic shielding of various geometries of bulk semi-closed superconducting cylinders subjected to axial and transverse fields

Fagnard

Vanderheyden

Pardo

et al. 2019

Supercond. Sci. Technol.

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“…Several low- [12][13][14]39 and high-temperature [40][41][42][43][44] superconducting materials have successfully been employed for shielding purposes. For the superconducting shield in this paper, niobium was selected based on the following properties.…”

Section: Detailed Designmentioning

confidence: 99%

“…15) illustrate that further model refinements are needed to describe the detailed flux behavior at the detector plane during cool-down, e.g., by explicitly taking the non-linear current density-electric field relation of the superconductor into account. 20,44,50 Nevertheless, comparing the AC residual field ratios R measured inside the hybrid shield under FC conditions (shown in Fig. 16) with those obtained after a ZFC procedure (Fig.…”

Section: Field Cooledmentioning

confidence: 99%

Design and validation of a large-format transition edge sensor array magnetic shielding system for space application

Bergen

Weers

Bruineman³

et al. 2016

Review of Scientific Instruments

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The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ∼100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 10, well exceeding the requirement of the envisaged missions. Following field-cooling in an axial field of 85 μT, the residual internal DC field normal to the detector plane is less than 1 μT. The trapped field patterns are compared to the predictions of the dynamic FEM model, which describes them well in the region where the internal field exceeds 6 μT.

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“…A hollow bulk superconductor is able to provide a transverse holding field inside, while adjusting its internal currents to shield any outside field [5,6]. The latter feature is an important improvement with respect to a conventional coil-based magnetic solution.…”

Section: Introductionmentioning

confidence: 99%

A bulk superconducting MgB2 cylinder for holding transversely polarized targets

Statera

Balossino

Barion

et al. 2018

Nuclear Instruments and Methods in Physics Research Section A:

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Magnetic shielding properties of a superconducting hollow cylinder containing slits: modelling and experiment

Cited by 20 publications

References 38 publications

Magnetic shielding of various geometries of bulk semi-closed superconducting cylinders subjected to axial and transverse fields

Magnetic shielding of various geometries of bulk semi-closed superconducting cylinders subjected to axial and transverse fields

Design and validation of a large-format transition edge sensor array magnetic shielding system for space application

A bulk superconducting MgB2 cylinder for holding transversely polarized targets

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