References of "Vanderbemden, Philippe"
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See detailCharacterization of superconductor magnetic properties in crossed magnetic fields
Vanderbemden, Philippe ULg

in Larbalestier, David; Cardwell, David (Eds.) Handbook of Superconducting Materials (2nd edition) (in press)

This chapter deals with the characterization of the magnetic properties of superconductors which are subjected to magnetic fields that have been applied along two orthogonal directions, which is commonly ... [more ▼]

This chapter deals with the characterization of the magnetic properties of superconductors which are subjected to magnetic fields that have been applied along two orthogonal directions, which is commonly referred to as a “crossed” magnetic field configuration. The purpose of this chapter is to describe the techniques that are useful to perform crossed field experiments, with an emphasis placed on practical aspects that are useful for designing the system and for understanding the measured data. This chapter is organized as follows. In Section 2, the key terms involved in the literature dealing with crossed field effects are defined. Section 3 deals with experimental methods and some key parameters will be outlined. In Section 4, practical conclusions will be drawn and next challenges in this area will be discussed. [less ▲]

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See detailBehaviour of bulk superconducting trapped field magnets subjected to magnetic fields with a transverse component
Vanderbemden, Philippe ULg; Caps, Hervé ULg; Vanderheyden, Benoît ULg et al

Conference (2016, November 10)

Bulk superconductors can be used as trapped field magnets with unprecedented performances. Such trapped field magnets find a variety of engineering applications, in particular for brushless rotating ... [more ▼]

Bulk superconductors can be used as trapped field magnets with unprecedented performances. Such trapped field magnets find a variety of engineering applications, in particular for brushless rotating machines and levitation devices. Compared to conventional permanent magnets, however, the magnetic field generated by a superconducting trapped field magnet is much more sensitive to the presence of an external field that is not perfectly aligned with the superconductor magnetic moment, i.e. when the external field has a transverse component. A situation where the superconductor experiences a magnetic field with a transverse component is likely to happen several times during running operation of the device. As an example, in a “trapped flux” synchronous machine, any variation of the load of the shaft may lead to a slight misalignment of the magnetic moment of the superconductor (placed in the rotor) with respect to the rotating field (generated by the stator). In such a situation, the superconductor is subjected to a rotating field, and the situation is likely to be different from a situation where the superconductor is subjected to a pure transverse field. In the present work, we aim at examining different scenarios (i.e. transverse or rotating) where the trapped field magnet is subjected to a transverse component. These configurations are examined both experimentally and numerically. The numerical model is used to determine the distribution of currents in the cross-section of the superconductor. We examine the conditions where the rotating field leads to a partial remagnetization of the sample and is therefore less detrimental that the application of a pure transverse field. We also show that the magnetic moment of the sample may behave differently that the field at the surface of the superconductor. Finally, we investigate the behavior of structures where the superconductor is attached to a thin ferromagnetic disk, and show the beneficial effect of such hybrid structures compared to the superconductor alone. Acknowledgements : The research was funded through the University of Liège (ULg) and an ARC grant for Concerted Research Actions, financed by the French Community of Belgium (Wallonia-Brussels Federation), under reference ARC 11/16-03. We greatly acknowledge M. Morita, S. Nariki and H. Teshima from Nippon Steel & Sumitomo Metal Corporation, Futtsu, Chiba. [less ▲]

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See detailMagnetic shielding above 1 T at 20 K with bulk, large grain YBCO tubes made by Buffer-aided Top Seeded Melt Growth.
Wera, Laurent ULg; Fagnard, Jean-François ULg; Kumar, Nambury Devendra et al

Poster (2016, September 07)

A superconducting tube can be used as an efficient magnetic shield. The best shielding performance levels are usually achieved when the tube is closed at one or both extremities. The purpose of the ... [more ▼]

A superconducting tube can be used as an efficient magnetic shield. The best shielding performance levels are usually achieved when the tube is closed at one or both extremities. The purpose of the present work is to study experimentally the shielding performance of YBCO tubes obtained by Buffer-aided Top Seeded Melt Growth fabrication process (BA-TSMG). This fabrication process enables the tube to be closed at one extremity by a cap containing the seed and there is no air gap between the cap and the tube. The shielding effectiveness is characterized by two parameters: (i) the shielding factor, defined as the ratio between the applied magnetic induction and the local magnetic induction measured inside the shield, and (ii) the threshold induction, i.e. the applied magnetic induction above which a given value of the shielding factor cannot be achieved. The magnetic shielding performances of tubes with different geometry are characterized at 77 K in liquid nitrogen. Further magnetic shielding measurements are carried out on one tube at various temperatures ranging from 20 K to 77 K using a Physical Property Measurement System (PPMS). The tubes are subjected to a quasi-static (“DC”) uniform magnetic field. A Hall probe measures the axial component of the local magnetic induction along the axis of the tube as a function of the applied magnetic induction. In order to investigate how the cap prevents the magnetic flux from penetrating inside the tube, we also characterize open tubes where the cap is removed and compare their properties to those of closed tubes. Magnetic shielding measurements show that the threshold induction increases by a factor of 9 as temperature decreases from 77 K to 20 K. Measurements also show that the presence of the cap improves the shielding performance at the closed extremity of the order of 1000 as it reduces the penetration through the open end. Near the closed extremity, a threshold induction of 1.5 T was reached at 20 K. To our knowledge this threshold induction is the best value reported so far at 20 K, and is comparable in magnitude to the record threshold inductions reported for bulk MgB2 and Bi-2212 materials at lower temperatures. These results give evidence that efficient magnetic shields can be obtained with this fabrication technique. [less ▲]

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See detailNon-destructive measurements of the volume magnetic behavior of large bulk GdBCO single domains and ferromagnet/superconductor structures
Vanderbemden, Philippe ULg; Egan, Raphael; Morita, Mitsuru et al

Conference (2016, September 05)

The present work deals with magnetic measurements on bulk large grain GdBa2Cu3O7 (GdBCO) single domains using a recently constructed bespoke magnetometer [Rev. Sci. Instrum. 86 025107 (2015)]. The device ... [more ▼]

The present work deals with magnetic measurements on bulk large grain GdBa2Cu3O7 (GdBCO) single domains using a recently constructed bespoke magnetometer [Rev. Sci. Instrum. 86 025107 (2015)]. The device enables the measurement of magnetic moments as large as 1 Am^2 (1000 emu) on large bulk samples up to 20 mm diameter at 77 K. This extends significantly the accessible measurement range of “off-the shelf” magnetometers (e.g. SQUID, VSM). Unlike Hall probe mapping, the measured signal is representative of the superconducting currents flowing across the entire height of the sample. Since the device is based on a flux extraction technique and does not include any Hall probe, another advantage is that no gap between a Hall probe and the sample needs to be taken into account to interpret the results. In the present work we first show how the dimensions of the sensing coils and integration bounds are chosen in such a way the magnetometer is sensitive to dipolar magnetic moment of the sample, while being insensitive to moments of higher order. Next we study the relaxation of the trapped magnetic moment under various magnetization processes. The sensitivity of the device allows small variations of m (e.g. ~ 2% for 1 hour) to be recorded. We show experimentally that the relaxation of the magnetic moment of the whole sample is reduced strongly if the superconductor is not fully magnetized, either in field cooled (FC) or zero-field cooled (ZFC) conditions. The practical consequence is that an abnormally slow magnetic relaxation (large E-J power law exponent n) under a conventional magnetization procedure indicates that the bulk superconductor could be magnetized further. In a second set of experiments, we study the increase of magnetic moment of a bulk superconductor when it is attached to a soft ferromagnetic disk. We also examine the irreversible demagnetization of these structures when subjected to crossed magnetic fields and compare to the magnetic moment of a classical (Nd-Fe-B) permanent magnets in the same conditions. Acknowledgements: This work is part of an "Action de Recherches Concertees" grant (ARC 11/16 -03) from the "Communaute Francaise de Belgique". [less ▲]

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See detailSuperconductors used as trapped field magnets : investigation of hybrid structures combining superconducting and ferromagnetic materials
Vanderbemden, Philippe ULg; Fagnard, Jean-François ULg; Caps, Hervé ULg et al

Conference (2016, August 30)

In addition to their unique ability to carry electric currents without loss, superconductors are able to trap significant magnetic flux densities at low temperature. In so-called type-II irreversible ... [more ▼]

In addition to their unique ability to carry electric currents without loss, superconductors are able to trap significant magnetic flux densities at low temperature. In so-called type-II irreversible superconductors, these properties are due to the pinning of individual flux lines (vortices) by defects at the nanoscale level. In this talk the influence of pinning on the magnetic properties of bulk superconductors will be explained and illustrated, with the emphasis placed on how pinning can be exploited to produce “trapped field magnets” for practical applications. We will then show how the properties of these trapped field magnets are enhanced when superconductors (SC) are combined to soft ferromagnetic (FM) alloys [1,2]. In particular we investigate the properties of macroscopic FM/SC/FM structures where the superconductor is sandwiched between two ferromagnetic sections, one of each circular face. In particular we show how the properties of the whole structure is influenced by the saturation magnetization and the geometry of the ferromagnetic material. References: 1. M P Philippe, J-F Fagnard, S Kirsch, Z Xu, A R Dennis, Y H Shi, D A Cardwell, B Vanderheyden, and P Vanderbemden, Magnetic characterisation of large grain, bulk Y–Ba–Cu–O superconductor–soft ferromagnetic alloy hybrid structures. Physica C: 502 (2014) 20-30. 2. M P Philippe, M D Ainslie, L Wera, J-F Fagnard, A R Dennis, Y H Shi, D A Cardwell, B Vanderheyden, and P Vanderbemden, Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor. Superconductor Science and Technology: 28 (2015) 095008. [less ▲]

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See detailImprinting superconducting vortex footsteps in a magnetic layer
Brisbois, Jérémy ULg; Motta, Maycon; Avila Osses, Jonathan ULg et al

in Scientific Reports (2016), 6

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit ... [more ▼]

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories. [less ▲]

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See detailMagnetic shielding with bulk high-temperature superconducting hollow cylinders: improvement of the shielded volume and investigation of sequential orthogonal applied fields
Vanderbemden, Philippe ULg; Hogan, Kevin ULg; Wera, Laurent ULg et al

Conference (2016, April 26)

Due to their ability to trap magnetic fields that exceed the saturation magnetization of conventional ferromagnets, bulk high-temperature superconductors have great potential to act as efficient passive ... [more ▼]

Due to their ability to trap magnetic fields that exceed the saturation magnetization of conventional ferromagnets, bulk high-temperature superconductors have great potential to act as efficient passive magnetic shields. Shielding efficiency is usually demonstrated in bulk hollow cylinders. One of the main drawbacks of this geometry is that the shielding is only effective in the central region of the tube and decreases towards the tube extremities because of the field penetration through the open ends. In order to improve the performances at tube extremities and hence increase the shielded volume, the tube should be closed using e.g. a superconducting cap. Gaps or holes, however, are needed for allowing connections between the inner part of the tube and the external world. In this communication we examine the shielding efficiency and volume when a superconducting tube is closed either at one extremity or at both extremities. The effect of the gap size between the cap and the tube is also studied. Next we examine more complex magnetic shielding configurations where an external magnetic field is applied first one direction and a second field is subsequently applied along another (perpendicular) direction. We discuss the influence of pre-existing shielding supercurrents on the magnetic shielding properties. [less ▲]

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See detailMagnetic flux penetration in Nb superconducting films with lithographically defined micro-indentations
Brisbois, Jérémy ULg; Adami, Obaïd-Allah ULg; Avila Osses, Jonathan ULg et al

in Physical Review B (2016), 93(5), 054521

We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines ... [more ▼]

We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines (d-lines), caused by the abrupt bending of current streamlines around the indentations, depart from the expected parabolic trend close to the defect and depend on the shape and size of the indentation as well as on the temperature. These findings are backed up and compared with theoretical results obtained by numerical simulations and analytical calculations highlighting the key role played by demagnetization effects and the creep exponent n. In addition, we show that the presence of nearby indentations and submicrometer random roughness of the sample border can severely modify the flux front topology and dynamics. Strikingly, in contrast to what has been repeatedly predicted in the literature, we do not observe that indentations act as nucleation spots for flux avalanches, but they instead help to release the flux pressure and avoid thermomagnetic instabilities. [less ▲]

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See detailBulk high-temperature superconducting hollow cylinders used for magnetic shielding: effect of an initial trapped field on the shielding performances.
Wera, Laurent ULg; Fagnard, Jean-François ULg; Hogan, Kevin ULg et al

Poster (2016)

Bulk High-Temperature Superconductors (HTS) can be used as efficient passive magnetic shields with performances exceeding those of conventional ferromagnetic materials. The most common geometry for a ... [more ▼]

Bulk High-Temperature Superconductors (HTS) can be used as efficient passive magnetic shields with performances exceeding those of conventional ferromagnetic materials. The most common geometry for a superconducting shield is a bulk hollow cylinder. In this work, we investigate the magnetic shielding properties when the tube is not in the virgin state. Such a situation happens in practice when the tube has been initially subjected to a first magnetic field. The induced superconducting currents that are flowing in the tube generate a trapped magnetic moment which may deteriorate the shielding of a second field. Here we study experimentally how an initial trapped moment affects the shielding of a magnetic field, when they are both perpendicular to each other. In particular, we focus on the effect of an axial trapped moment on the transverse shielding performances and on the effect of a transverse trapped field on the axial or the transverse shielding performances. Finally, we show how the pristine state of the tube can be restored when applying an external field of adequate amplitude. The consequence for practical applications is that it is possible to recover shielding properties similar to those obtained in the virgin state without heating up the shield above its critical temperature TC. [less ▲]

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See detailMagnetic moment and local magnetic induction of superconducting/ferromagnetic structures subjected to crossed fields: experiments on GdBCO and modelling
Fagnard, Jean-François ULg; Morita, Mitsuru; Nariki, Shinya et al

in Superconductor Science and Technology (2016), 29(12), 125004

Recent studies have shown that ferromagnetic materials can be used together with bulk high temperature superconductors in order to improve their magnetic trapped field. Remarkably, it has also been ... [more ▼]

Recent studies have shown that ferromagnetic materials can be used together with bulk high temperature superconductors in order to improve their magnetic trapped field. Remarkably, it has also been pointed out that ferromagnets can help in reducing the crossed field effect, namely the magnetization decay that is observed under the application of AC transverse magnetic fields. In this work, we pursue a detailed study of the influence of the geometry of the ferromagnetic part on both trapped fields and crossed field effects. The magnetic properties of the hybrid superconducting/soft ferromagnetic structures are characterized by measuring the magnetic moment with a bespoke magnetometer and the local magnetic field density with Hall probes. The results are interpreted by means of 2D and 3D numerical models yielding the distribution of the superconducting currents as a function of the ferromagnet geometry. We examine in details the distortion of the shielding superconducting currents distribution in hybrid structures subjected to crossed magnetic fields. These results confirm the existence of an optimum thickness of the ferromagnet, which depends on the saturation magnetization of the ferromagnetic material and the current density of the superconductor. A hybrid structure providing an efficient protection against the crossed magnetic field while maintaining the magnetic induction along the axis of the structure is suggested. The limitations of the 2D modelling in this configuration are discussed. [less ▲]

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See detailInfluence of crossed fields in structures combining large grain, bulk (RE)BCO superconductors and soft ferromagnetic discs
Philippe, Matthieu ULg; Fagnard, Jean-François ULg; Wera, Laurent ULg et al

in Journal of Physics: Conference Series (2016), 695

Bulk (RE)BCO superconductors are able to trap record magnetic fields and can be used as powerful permanent magnets in various engineering applications such as rotating machines and magnetic bearings. When ... [more ▼]

Bulk (RE)BCO superconductors are able to trap record magnetic fields and can be used as powerful permanent magnets in various engineering applications such as rotating machines and magnetic bearings. When such superconducting (SC) “trapped field magnets” are combined to a ferromagnetic (FM) disc, the total magnetic moment is increased with respect to that of the superconductor alone. In the present work, we study experimentally the magnetic behaviour of such hybrid FM/SC structures when they are subjected to cycles of applied field that are orthogonal to their permanent magnetization, i.e. a “crossed-field” configuration. Experimental results show that the usual “crossed-field demagnetization” caused by the cycles of transverse field is strongly reduced in the presence of the ferromagnet. [less ▲]

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See detailCritical analysis of the paramagnetic to ferromagnetic phase transition in Pr0.55K0.05Sr0.4MnO3
Thaljaoui, R.; Pękała, M.; Fagnard, Jean-François ULg et al

in Physica B: Condensed Matter (2016), 482

The critical properties of monovalent doped manganite Pr0.55K0.05Sr0.4MnO3 around the paramagnetic to ferromagnetic phase transition were investigated through various methods: the modified Arrott plots ... [more ▼]

The critical properties of monovalent doped manganite Pr0.55K0.05Sr0.4MnO3 around the paramagnetic to ferromagnetic phase transition were investigated through various methods: the modified Arrott plots (MAP), the Kouvel-Fisher method and the critical isotherm analysis. Data obtained near Tc were examined in the framework of the mean field theory, the 3D–Heisenberg model, the 3D–Ising model, and tricritical mean field. The deduced critical exponents values obtained using MAP method were found to be β = 0.44(4) with TC ~ 303 K and γ = 1.04(1) with TC ~ 302 K. Kouvel-Fisher method supplies the critical values to be β = 0.41(2) with TC ~ 302 K and γ = 1.09(1) with TC ~ 302 K. The obtained critical parameters show a tendency towards the mean-field behavior, suggesting the existence of long-range ferromagnetic order in the compound studied. The exponent δ deduced separately from isotherm analysis at T= 303 K was found to obey to the Widom scaling relation δ = 1+ γ/ β. The reliability of obtained exponents was confirmed by using the universal scaling hypothesis. The itinerant character of ferromagnetism in the present system was also tested by using Rhodes-Wohlfarth’s criterion. [less ▲]

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See detailThermal properties of Ti-doped Cu–Zn soft ferrites used as thermally actuated material for magnetizing superconductors
Stachowiak, Piotr; Mucha, Jan; Szewczyk, Daria et al

in Journal of Physics : D Applied Physics (2016), 49

A great majority of widely used ferrite ceramics exhibit a relatively high temperature of order–disorder phase transition in their magnetic subsystem. For applications related to the magnetization process ... [more ▼]

A great majority of widely used ferrite ceramics exhibit a relatively high temperature of order–disorder phase transition in their magnetic subsystem. For applications related to the magnetization process of superconductors, however, a low value of Tc is required. Here we report and analyze in detail the thermal properties of bulk Ti-doped Cu–Zn ferrite ceramics Cu0.3Zn0.7Ti0.04Fe1.96O4 and Mg0.15Cu0.15Zn0.7Ti0.04Fe1.96O4. They are characterized by a Curie temperature in the range 120–170 K and a maximum DC magnetic susceptibility exceeding 20 for the Cu0.3Zn0.7Ti0.04Fe1.96O4 material. The temperature dependence of both the specific heat Cp and of the thermal conductivity κ, determined between 2 and 300 K, are found not to exhibit any peculiar feature at the magnetic transition temperature. The low-temperature dependence of both κ and the mean free path of phonons suggests a mesoscopic fractal structure of the grains. From the measured data, the characteristics of thermally actuated waves are estimated. The low magnetic phase transition temperature and suitable thermal parameters make the investigated ferrite ceramics applicable as magnetic wave producers in devices designed for magnetization of high-temperature superconductors. [less ▲]

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See detailMagnetic Shielding with Bulk High Temperature Superconductors: Improvement of the Shielded Volume in Hollow Cylinders
Wera, Laurent ULg; Fagnard, Jean-François ULg; Hogan, Kevin ULg et al

in Muralidhar, Miryala (Ed.) Superconductivity: Applications Today and Tomorrow (2016)

The superconducting HTS hollow cylinder has been one of the first geometries to demonstrate its utility as an efficient passive magnetic shield, and particularly for DC magnetic shielding. The shielding ... [more ▼]

The superconducting HTS hollow cylinder has been one of the first geometries to demonstrate its utility as an efficient passive magnetic shield, and particularly for DC magnetic shielding. The shielding performances can be characterized by two parameters: (i) the shielding factor SF, defined as the ratio between the applied magnetic induction Bapp and the magnetic induction inside the shield Bin and (ii) the threshold induction Blim for which the shielding factor becomes lower than a given level. The main drawback of the hollow cylinder geometry is that the shielding is only effective in the central region of the tube and decreases towards the tube extremities because of the field penetration through the open ends. In order to improve the performances at tube extremities and hence increase the shielded volume, the tube should be closed. This can be achieved by using a superconducting vessel or by closing one or both extremities with a cap. This chapter describes the experimental and the numerical analysis of the DC shielding performances of a Bi-2223 tube closed by a superconducting Bi-2223 cap, for an axial configuration. The first part is dedicated to the experimental study of two tubes of different lengths when they are closed at one extremity or closed at both extremities. We also study the effect of the gap size between the cap and the tube. In the second part, we use numerical simulations to highlight the possible improvements and to optimize the design. In particular we study the influence of the critical current density and of the thickness of the cap. [less ▲]

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See detailProcessing and applications of (RE)BCO and MgB2 bulk superconductors: an introduction to the special issue
Vanderbemden, Philippe ULg; Cardwell, D A; Freyhardt, H C et al

in Superconductor Science and Technology (2016), 29

Preface of the Superconductor Science and Technology special issue "Focus on processing and applications of (RE)BCO and MgB2 bulk superconductors". This special issue focuses on contributions from the 9th ... [more ▼]

Preface of the Superconductor Science and Technology special issue "Focus on processing and applications of (RE)BCO and MgB2 bulk superconductors". This special issue focuses on contributions from the 9th International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials (PASREG 2015). The workshop was held at the University of Liège, Belgium on 02–04 September, 2015, as a satellite conference of the European Conference on Applied Superconductivity (EUCAS 2015). The Chairman was Philippe Vanderbemden; Benoît Vanderheyden, David Cardwell, and Herbert C Freyhardt served as Co-Chairmen. PASREG 2015 was the latest in a series of international workshops previously held in Cambridge, UK (1997), Morioka, Japan (1999), Seattle, USA (2001), Jena, Germany (2003), Tokyo, Japan (2005), Cambridge, UK (2007), Washington D.C., USA (2010), and Tainan, Taiwan (2012). [less ▲]

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See detailElectric charging of bodies and electrostatic discharges: Basic notions
Vanderbemden, Philippe ULg

Conference (2015, December 15)

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See detailDesign of the superconducting end caps of a tubular magnetic shield.
Wera, Laurent ULg; Fagnard, Jean-François ULg; Hogan, Kevin ULg et al

Poster (2015, September 09)

Shielding a sensitive device against DC or AC stray magnetic fields can be realized very efficiently with high-Tc superconductors. A simple magnetic shield can be obtained with a tube enclosing the device ... [more ▼]

Shielding a sensitive device against DC or AC stray magnetic fields can be realized very efficiently with high-Tc superconductors. A simple magnetic shield can be obtained with a tube enclosing the device, which is protected against external fields until the magnetic flux diffuses either across the tube wall or through the end openings. A better shielding vessel is obtained by using superconducting end caps. In the simplest design, the end caps, consisting of superconducting disks placed at the extremities of the tube, are making a 90 degree angle with the tube wall. Because of demagnetization effects, this arrangement results in a 'weak spot' for the penetrating magnetic flux. In this work, we investigate numerically different shapes for the end caps so as to avoid sharp angles and obtain a smoother magnetic flux penetration. The external magnetic induction is applied parallel to the shield axis. The magnetic flux distribution and the shielding currents are calculated with a finite element approach. The shielded volume is defined as the region where the local magnetic flux density is attenuated below a given fraction of the external field. It is studied as a function of the shape of the cap, its superconducting properties, the aspect ratio of the assembly, and the presence of a cabling hole. Curved and elongated caps, which could in principle be obtained by melt cast processing or different coating techniques, are shown to substantially increase the shielded volume. [less ▲]

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See detailMagnetic shielding properties of a bulk Bi-2223 superconducting hollow cylinder subjected to the magnetic stray field of a nearby magnetic source
Hogan, Kevin ULg; Wera, Laurent ULg; Fagnard, Jean-François ULg et al

Poster (2015, September 09)

Superconducting materials act as efficient magnetic shields thanks to their intrinsic magnetic properties. At low frequencies, their efficiency even surpasses that of conventional ferromagnetic materials ... [more ▼]

Superconducting materials act as efficient magnetic shields thanks to their intrinsic magnetic properties. At low frequencies, their efficiency even surpasses that of conventional ferromagnetic materials. Therefore, they can be very useful for many applications which require low or very low magnetic field in intense quasi-static magnetic environments. The vast majority of studies on superconducting screens has been conducted in homogeneous magnetic field configurations. Few works have been done concerning inhomogeneous magnetic field configurations while those are representative of practical situations. Moreover, those configurations are non-trivial given the magnetic hysteretic behaviour of type-II superconductors. In the present work, we aim at investigating and understanding the shielding properties of a superconducting hollow cylinder made of Bi-2223 subjected to the magnetic stray field of a coil placed in the vicinity. All experiments are carried out at 77K. [less ▲]

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