Pulsed-field magnetization of drilled bulk high-temperature superconductors: flux front propagation in the volume and on the surface

TL;DR

This paper introduces a method to analyze magnetic flux propagation in drilled bulk high-temperature superconductors during pulsed-field magnetization, revealing differences in flux front speed and trapped flux distribution between the surface and median plane.

Contribution

It provides a novel experimental approach to measure flux front dynamics in three dimensions within drilled HTS samples during pulsed magnetization.

Findings

Flux front moves faster in the median plane than on the surface initially.

The flux penetrates faster along the surface as it advances.

Trapped flux density is higher in the median plane after the pulse.

Abstract

We present a method for characterizing the propagation of the magnetic flux in an artificially drilled bulk high-temperature superconductor (HTS) during a pulsed-field magnetization. As the magnetic pulse penetrates the cylindrical sample, the magnetic flux density is measured simultaneously in 16 holes by means of microcoils that are placed across the median plane, i.e. at an equal distance from the top and bottom surfaces, and close to the surface of the sample. We discuss the time evolution of the magnetic flux density in the holes during a pulse and measure the time taken by the external magnetic flux to reach each hole. Our data show that the flux front moves faster in the median plane than on the surface when penetrating the sample edge; it then proceeds faster along the surface than in the bulk as it penetrates the sample further. Once the pulse is over, the trapped flux density inside the central hole is found to be about twice as large in the median plane than on the surface. This ratio is confirmed by modelling.