Excellent field-trapping properties of large ring-shaped REBCO melt-textured bulks fabricated by the Single-Direction Melt Growth (SDMG) method

Abstract Ring–shaped homogeneous YBCO and DyBCO bulks were successfully fabricated using the Single–Direction Melt Growth (SDMG) method. The bulks were directly grown from ring–shaped compacted powder using ring–shaped molds with an outer diameter of 50 mm and inner diameters of 15, 20, and 25 mm. The ring–shaped bulks exhibited high trapped fields inside the rings up to 1.2 T at 77 K. Analyses of trapped field distributions revealed uniform current density distributions along the orbital direction. Stacked ring bulks demonstrated even higher trapped fields, reaching 2.0 T at 77 K. It was confirmed for the stacked bulks that time–independent uniform trapped fields can be achieved by magnetizing at lower fields than fully magnetizing conditions. Observed paramagnetic magnetization of the SDMG–processed YBCO bulk was negligibly small below the detection limit, which is considered to be more suitable for bulk NMR/MRI applications than DyBCO. Additionally, we proposed a method to quantitatively evaluate trapped fields of superconducting bulks with various diameters and thicknesses, where the estimated average current densities from the maximum trapped fields for all the obtained ring–shaped bulks were above 10 4 A cm –2 at 77 K. These results indicate that SDMG is an effective method for fabricating high–quality, large–scale ring–shaped bulks with superior field–trapping properties.