Self-field Loss in AC Transport Current Loss of MgB_2 Superconducting Composites

The measurement and analysis of AC transport current loss (self-field loss) in MgB2 superconducting composites were studied. In experimental results, the normalized Ic dependency of AC loss in the MgB2 deviated from Norris' theoretical curve. Then a numerical analysis was performed by taking into consideration the model of a round superconducting wire that consisted of three concentric layers. The analysis clearly showed the experimentally obtained results, such as that the phenomenon originated in the inhomogeneity of the critical current density in the wire rod section.