Article (Scientific journals)
Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow cylinders in axial magnetic fields
Fagnard, Jean-François; Elschner, Steffen; Bock, Joachim et al.
2010In Superconductor Science and Technology, 23, p. 095012
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Keywords :
magnetic properties; magnetic shielding; superconductors
Abstract :
[en] We show that tubes of melt cast Bi-2212 used as current leads for LTS magnets can also act as efficient magnetic shields. The magnetic screening properties under an axial DC magnetic field are characterized at several temperatures below the liquid nitrogen temperature (77 K). Two main shielding properties are studied and compared with those of Bi-2223, a material that has been considered in the past for bulk magnetic shields. The first property is related to the maximum magnetic flux density that can be screened, Blim; it is defined as the applied magnetic flux density below which the field attenuation measured at the centre of the shield exceeds 1000. For a cylinder of Bi-2212 with a wall thickness of 5 mm and a large ratio of length over radius, Blim is evaluated to 1 T at T = 10 K. This value largely exceeds the Blim value measured at the same temperature on similar tubes of Bi-2223. The second shielding property that is characterized is the dependence of Blim with respect to variations of the sweep rate of the applied field, dBapp/dt. This dependence is interpreted in terms of the power law E = Ec(J/Jc)^n and allows us to determine the exponent n of this E(J) characteristics for Bi-2212. The characterization of the magnetic field relaxation involves very small values of the electric field. This gives us the opportunity to experimentally determine the E(J) law in an unexplored region of small electric fields. Combining these results with transport and AC shielding measurements, we construct a piecewise E(J) law that spans over 8 orders of magnitude of the electric field.
Research center :
SUPRATECS - Services Universitaires pour la Recherche et les Applications Technologiques de Matériaux Électro-Céramiques, Composites, Supraconducteurs - ULiège
Disciplines :
Electrical & electronics engineering
Physics
Author, co-author :
Fagnard, Jean-François  ;  Ecole Royale Militaire (Belgique) - ERM > CISS
Elschner, Steffen;  University of Applied Science Mannheim, Germany
Bock, Joachim;  Nexans SuperConductors GmbH, Hürth, Germany
Dirickx, Michel;  Ecole Royale Militaire (Belgique) - ERM > CISS
Vanderheyden, Benoît  ;  Université de Liège - ULiège > Dép. d'électric., électron. et informat. (Inst.Montefiore) > Electronique et microsystèmes
Vanderbemden, Philippe  ;  Université de Liège - ULiège > Dép. d'électric., électron. et informat. (Inst.Montefiore) > Capteurs et systèmes de mesures électriques
Language :
English
Title :
Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow cylinders in axial magnetic fields
Publication date :
2010
Journal title :
Superconductor Science and Technology
ISSN :
0953-2048
eISSN :
1361-6668
Publisher :
Institute of Physics, Bristol, United Kingdom
Volume :
23
Pages :
095012
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
RMA - Royal Military Academy [BE]
FWB - Fédération Wallonie-Bruxelles [BE]
Available on ORBi :
since 18 August 2010

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