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INTERCOMPARISON OF CRITICAL CURRENT MEASUREMENTS IN Nb3Sn SUPERCONDUCTORS

Objective



The current carrying capability of superconductors is limited by the strength of the applied magnetic field. An intercomparison of critical current determinations in a Nb3Sn superconductor was undertaken between laboratories within the Community. Subsequently a second intercomparison involving laboratories in Europe, Japan and the USA was arranged as part of the Versailles Project on Advanced Materials and Standards (VAMAS). As the wires have to be heat treated to form the superconducting Nb3Sn phase, the intercomparisons were structured in order to identify differences arising from both the heat treatment and the critical current measurements.

RESULTS

European intercomparison

Completed in 1986, this intercomparison showed an agreement on critical current measurements to within 6% irrespective of whether the specimens were heat treated individually by the participants or centrally in a single batch. The major source of differences was identified as induced strain effects, the magnitude of which depended upon the details of the mandrel upon which the specimen was wound and the method of fixing it in place.
VAMAS intercomparison
22 laboratories from Europe, USA and Japan made measurements on 3 wires of different construction and hence current carrying capacity. The results reflected the same trends as found in the European intercomparison. The between laboratory standard deviation increased from 6% to 12% as the current carrying capacity of the wire decreased from approximately 550 to 400 A. The induced strain in the different experimental set-ups was again approximately equivalent to the observed scatter in the critical current data. A second round using a single wire on identical mandrels and more precisely defined test procedures reduced the scatter in the data from 8.3 to 2.2% at a field strength of 12 Tesla.

Coordinator

VACUUMSCHMELZE GMBH
Address
Gruener Weg 37
63450 Hanau
Germany

Participants (12)

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (CNRS)
France
Address
3, Rue Michel Ange
Commissariat à l'Energie Atomique (CEA)
France
Address
Centre D'études De Saclay
91191 Gif-sur-yvette
Ente per le Nuove Tecnologie, l'Energia e l'Ambiente (ENEA)
Italy
Forschungszentrum Karlsruhe Technik und Umwelt GmbH
Germany
Address

76021 Karlsruhe
Imgc
Italy
Infn
Italy
Rutherford Appleton Laboratory (RAL)
United Kingdom
Address
Chilton
OX11 0QX Didcot
SCK/CEN
Belgium
Siemens AG
Germany
Twente University of Technology
Netherlands
Universiteit Nijmegen
Netherlands
University of Oxford
United Kingdom
Address
Parks Road
OX1 3PU Oxford