Self-fields in thin superconducting tapes: implications to the thickness effect in coated conductors

TL;DR

This paper theoretically explains the thickness-dependent decrease in critical current density in coated superconducting tapes by analyzing the self-field effects, offering insights to improve performance in thick superconducting films.

Contribution

It provides a theoretical analysis of the self-field effects causing the thickness effect in coated conductors with realistic Jc dependence.

Findings

Self-field effects significantly influence Jc in thick superconducting tapes.

Theoretical model explains the universal thickness effect observed in experiments.

Insights can guide the development of thicker, higher-performance superconducting films.

Abstract

Most applications of superconductors, such as power transmission lines, motors, generators, and transformers, require long cables through which large currents circulate. Impressive progress has recently been achieved in the current-carrying capability in conductors based on high-temperature superconductors. Coated conductors are likely the best examples, consisting of very good quality thin layers of YBCO superconductor grown on top of a metallic tape with some intermediate layers. However, there is an important problem for achieving large currents: a large decrease in transport critical-current density Jc when increasing film thickness has been observed in coated conductors made by all available techniques. Here, we theoretically explain the nature and the ubiquitous presence of this so-called thickness effect by analyzing the self-field created by the transport currents in the superconductor, assuming a realistic field-dependent Jc. This knowledge can help finding new ways to improve transport current in thick superconducting films.