Trapped field magnets providing a large, stable magnetic field are critical to the operation of an abundance of superconducting engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields that are an order-of-magnitude larger than those generated by conventional magnetic materials, which are generally limited to less than 2 T. This provides an opportunity for bulk HTS materials to replace conventional ferromagnets, and, as a result, significantly improve applications such as rotating machines and MRI/NMR. A practical method of magnetising HTS materials is via pulsed-field magnetisation (PFM), which involves the rapid application (on the order of 10s-100s of ms) of a pulsed magnetic field to a bulk superconductor. This method, however, can generate a large amount of heat in the sample due to the rapid movement of magnetic flux, and therefore reduced its trapped field performance. In addition, the PFM process can result in the occurrence of flux jumps due to increased thermomagnetic instability. In this paper, we analyse the effects of flux jumps in a GdBCO bulk superconducting disc and demonstrate the viability of flux jump-assisted PFM. Increasingly, the observation of flux jumps during the rise time of the pulse during PFM has been shown to assist the sample magnetisation. However, the complex nature of flux jumps requires a careful understanding and optimisation of the magnetisation technique. Utilising finite-element models, we show that a numerical model based on the H-formulation, with a 2D-axisymmetric and spatially inhomogeneous J_c distribution representative of state-of-the-art materials, can lead to an accurate numerical description of flux jumps in bulk HTS materials. We further describe how the magnetisation parameters may be optimised to assist the magnetisation process utilising flux jumps under PFM of a HTS bulk superconductor, which could be an enabling technology for the use of these technologically important materials in realising practical applications.

Keywords: PFM, Bulks, HTS, FEM Modelling