Pulsed field magnetization of a rectangular Y–Ba–Cu–O bulk, single grain superconductor assembly

Abstract

The practical magnetization of arrays of multiple single grain, bulk high temperature superconductors (HTSs) is essential for practical applications, such as trapped flux rotating machines, magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR). We report a systematic investigation of the pulsed field magnetization (PFM) of a bulk assembly consisting of two rectangular Y-Ba-Cu-O (YBCO) bulk single grains, in close proximity, at various temperatures. The measurements of the dynamic variation of the magnetic flux density, supported by numerical analysis, reveal that the induced screening currents during the rise of a pulsed field may greatly enhance the flux density in the region of the junction leading to uneven flux penetration and to an increased likelihood of flux jumps in this region. Such coupling between field and current promotes magnetic flux penetration and improves the peak trapped field from 3.01 T for a bulk single grain to 3.11 T for the bulk assembly at 30 K, improving the magnetization efficiency from 80% to 90%. The peak trapped field was further enhanced to 3.39 T and 3.31 T for the single bulk single grain and the bulk assembly, respectively, by employing a two-step multi-pulse PFM process.