Experimental studies on the critical current of REBCO coated conductors as a function of the magnetic field and temperature for a scaling law suitable for designing high field accelerator magnets.

Abstract

REBCO coated conductors, or tapes, are innovative materials which are attracting major attention in the worldwide community of applied superconductivity. Their ability to work from the liquid helium temperature up to the liquid nitrogen temperature, combined with their high performance in magnetic fields, make them a potential game-changer not only in superconductivity, but also in the broader domain of electromagnetic machines. Nonetheless, the design and modelling of coils and other devices wound with REBCO tapes require an accurate knowledge of their electrical properties.

So-called scaling laws are needed to define tape properties and a thorough experimental campaign is needed to validate them. Scaling laws validated by the experimental effort are of the utmost importance for the design of coils and magnets. In this work, a formulation of an anisotropic scaling law that describes the field dependence of the critical current of REBCO tapes up to the irreversibility field and at temperatures of up to the critical temperature, is proposed. The law extends on previous formulations available in the literature.

The validation of this law is conducted by means of an experimental campaign of testing REBCO tapes from various manufacturers. Measurements of critical current were done via transport and magnetization methods at two facilities available at CERN. For the transport method, a sample holder with a 'U' shape was developed, to create a short straight region and expose tapes to a perpendicular field inside the bore of a solenoid station. Tests were conducted in liquid helium, at~4.2~K, and in magnetic fields of up to 15 T. Magnetization measurements have also been performed on small tape samples to extend the measurement range up to the critical temperature, using a vibrating sample magnetometer (VSM), in perpendicular fields of up to 10 T.

Matching of the two methods allows inferring the critical current as a function of field and temperature. The resulting scaling parameters of tapes are derived for various manufacturers. Different as well as common patterns in the temperature dependence of the scaling parameters have been identified and a correlation with the known pinning landscapes has been discussed. The variations of the scaling law parameters and their temperature dependence could be helpful in further performance optimization, through correlation with the material science and production techniques of the different manufacturers. To conclude, the scaling law is validated for coated conductors exposed to perpendicular magnetic fields.

More information

Identifiers

ORCID for Giovanni Succi: orcid.org/0000-0002-1729-1401

ORCID for Yifeng Yang: orcid.org/0000-0002-3874-6735

Catalogue record

Export record