The magnetisation of ReBCO conductors is accentuated the strip geometry of very thin layer superconductors and a relative broad width, in contrast with typical round wire strands with fine filaments. In this talk, we show that efficient 2D formulations can be used to give insight into the details of the magnetisation process associated with the transverse distribution of the inducted currents.
While the intra-strand distribution of the inducted currents plays an insignificant role for LTS magnet design, we argue that the load-line approach can be insufficient for designing ReBCO coils. We show that the current distribution within ReBCO coupled with the anisotropic field dependence of critical current can result in the critical current is reached first in strands where the local magnetic field is not the highest. Furthermore, the current distributions in ReBCO strands in a coil can be different between insulated and uninsulated coils. An efficient turn-by-turn formulation is presented and used to model representative assemblies of ReBCO pancake coils. The (lack of) interplay between the current distribution and flux creep through non-linear E-J characteristics is highlighted and explained.
The induced current distributions within ReBCO strands also determine the ac losses of composite conductors such as Roebel cables. While the transposed strands are intrinsically 3D, we explain that the magnetic coupling within the strands can be modelled by the 2D formulations, and the underlying losses agree quantitatively with the experimental results of ReBCO Roebel cable samples.
