Temperature Dependence of AC Transport Current Loss of QMG Bulk Superconductor

Abstract

The AC transport current loss of a QMG bulk superconductor for a current-limiting device with a rectangular cross section was measured at various frequencies in the temperature range of 40–77 K. Since the AC transport current loss did not appreciably depend on frequency in the range of 35–70 Hz, the pinning loss was dominant. The experimental result was well explained by the numerical calculation by finite element method in which the Irie–Yamafuji model was assumed for the magnetic field dependence of critical current density. The AC transport current loss decreased markedly with decreasing temperature. Therefore, it is beneficial to decrease temperature, since the increase in cooling penalty is not significant. It was also found that cylindrical superconductors have a lower AC transport current loss than rectangular superconductors.

Plastic Forming of High‐TcYBa2Cu3O7−x Bulk Superconductors

“…Numerous approaches have been attempted to synthesize YBCO products which have a high critical temperature ( T c ) and a J c . These approaches have used melt‐texturing concepts, such as melt‐powder‐melt‐growth (MPMG) and quench and melt growth (QMG) . With melt texturing, bulk superconductors can be made that have critical current densities in the range from 10 4 to 10 5 A/cm 2 at 77 K. To make the desired form of a large bulk superconductor by the above methods, first block samples which are larger than the desired form must be made, and then they are cut, milled, and polished.…”