Normal zone in $YBa_2Cu_3O_{6+x}$-coated conductors

TL;DR

This paper analyzes electric field distribution in YBCO-coated conductors during normal zone propagation, highlighting the potential for electric discharges to detect quenches, with implications for superconductor stability.

Contribution

It provides a detailed theoretical analysis of electric fields in YBCO conductors during normal zones, including substrate effects and potential quench detection methods.

Findings

Electric field in the substrate can be large due to screening effects.

Electric fields at the YBCO-stabilizer interface can reach several kV/cm.

Potential for microscopic discharges to serve as quench indicators.

Abstract

We consider the distribution of an electric field in YBCO-coated conductors for a situation in which the DC transport current is forced into the copper stabilizer due to a weak link -- a section of the superconducting film with a critical current less than the transport current. The electric field in the metal substrate is also discussed. The results are compared with recent experiments on normal zone propagation in coated conductors for which the substrate and stabilizer are insulated from each other. The potential difference between the substrate and stabilizer, and the electric field in the substrate outside the normal zone can be accounted for by a large screening length in the substrate, comparable to the length of the sample. During a quench, the electric field inside the interface between YBCO and stabilizer, as well as in the buffer layer, can be several orders of magnitude greater than the longitudinal macroscopic electric field inside the normal zone. We speculate on the possibility of using possible microscopic electric discharges caused by this large ($\sim $kV/cm) electric field as a means to detect a quench.