High-speed fluorescent thermal imaging of quench propagation in high temperature superconductor tapes

TL;DR

This paper demonstrates high-speed fluorescent thermal imaging to visualize and measure temperature changes during quench events in high temperature superconductor tapes, enabling detailed analysis of quench propagation.

Contribution

It introduces a novel application of fluorescent microthermographic imaging with high temporal resolution for studying quench dynamics in HTS tapes.

Findings

Successfully visualized quench propagation in HTS tapes.

Calculated temperature distribution during quench events.

Demonstrated the method's effectiveness in a liquid nitrogen environment.

Abstract

Fluorescent Microthermographic Imaging, a method using rare-earth fluorescent coatings with temperature-dependent light emission, was used for quench investigation in high temperature superconductors (HTS). A fluorophore was embedded in a polymer matrix and used as a coating on top of an HTS tape, while being excited with UV light and recorded with a high-speed camera. Simultaneously, the tape was pulsed with high amplitude, short duration DC current, and brought to quench with the help of a localized defect. The joule heating during a quench influences the fluorescent light intensity emitted from the coating, and by recording the local variations in this intensity over time, the heating of the tape can be visualized and the developed temperatures can be calculated. In this paper, the fluorophore Europium tris[3-(trifluoromethylhydroxymethylene)- (+)-camphorate] (EuTFC) provided sufficient temperature sensitivity and a usable temperature range from 77 K to 260 K. With the help of high-speed recordings, the normal zone development was imaged in a 20 \mu m copper stabilized HTS tape held in a liquid nitrogen bath, and using a calibration curve, the temperatures reached during the quench have been calculated.