Bulk high temperature superconductors (HTS) have significant potential for industrial applications such as magnetic bearings, flywheel energy storage systems and trapped-field magnets. One of the prospective applications of bulk high temperature superconductors is a superconducting magnet for magnetically levitated (maglev) trains. It is very difficult to make a big superconducting bulk for various large-scale applications.
The fabrication of bulk HTS for high trapping magnetic fields has been extensively studied and the top seeded melt growth (TSMG) process is a superconductor fabrication method developed for the improvement of flux pinning property of bulk HTS. This method, widely used in the field of superconductor manufacturing, has been applied to the superconductor magnetic levitation equipment like magnetic bearings due to its ability to raise the flux pinning property of superconductors several times more than the preceding methods.
Ri Hak Mun, a researcher at the Faculty of Physical Engineering, has confirmed the position-dependent current density distribution inside the bulk high temperature superconductor after field cooling of bulk HTS fabricated by TSMG by numerical calculations, and considered the effect of shape and aspect ratio of the bulk HTS on the z-axis trapped magnetic field.
The results have shown the following conclusions.
First, the critical current density distribution depending on the position in the cylindrical bulk HTS after field cooling of the bulk Y-Ba-Cu-O superconductor prepared by TSMG is a polynomial monotone function. Second, among the cylindrical and squared bulk HTS of the same volume, the cylindrical one has bigger z-axis trapped magnetic field. Third, in the case of uniform critical current density in the range of 4-30mm in radius and 1-50mm in height, the aspect ratio affecting the trapped magnetic field property is 0.775-0.957, and in the case of ununiformity, it is 0.625-0.829.
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