Percolative Current Flow through Anisotropic High-Field Superconductors under Strain

Abstract

For decades, flux pinning scaling laws based upon unimodal, infinitesimally narrow, averaged distributions of critical superconducting parameters have been used to explain what limits the critical currents of practical superconducting materials in high fields. These scaling laws have enabled superconducting technologies ranging from MRI scanners, to high field research magnets, to magnets for particle accelerators and fusion energy. However in this work, we progress beyond these approximations and provide:

(i) The first comprehensive analysis of critical current density data showing that in high magnetic fields, technological
low and high temperature superconducting materials can be treated as a percolative network of Josephson junctions. We
then extract the size and normal state properties of the grain boundaries, the underlying distribution within the grains, and the dimensionality of the current flow within the material

(ii) The first reported measurements of the in-plane, biaxial strain dependence of for (RE)BCO tapes. This provides a description and understanding of the effects of the two most important strain components on and

(iii) The first comprehensive framework for percolative current flow in LTS and HTS superconductors under strain. It explicitly includes the factors suppressing and describes percolative flow within an anisotropic material containing a distribution of critical superconducting parameters. Our results show that large improvements to are available from further optimisation of the grains and grain boundaries in (RE)BCO and which will help enable the successful delivery of commercial fusion tokamaks.