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

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 Flux front propagation in a drilled HTS during a pulsed-field magnetization 2 is found to be about twice as large in the median plane than on the surface. This ratio is confirmed by modelling.Flux front propagation in a drilled HTS during a pulsed-field magnetization Recently, bulk HTS cylinders with artificial columnar holes have been synthesized; the presence of holes has been shown to enhance the chemical, thermal, and mechanical properties of the bulk HTS material [4,15,16,17]. Drilled structures also offer a means for characterizing locally the magnetic properties inside the volume of the magnet.The procedure is described in a previous work for the case of an AC magnetic field excitation [18] and is based on the acquisition of the pick-up voltage across microcoils inserted inside the holes, in order to probe the magnetic flux in the bulk of the sample.In this paper, we use microcoils to locally measure the magnetic flux density inside

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