高温超导临界电流密度J_c测量中的自场效应

THE SELF-FIELD EFFECTS IN THE MEASUREMENTS OF THE CRITICAL CURRENT DENSITY (J c ) OF THE HIGH TEMPERATURE SUPERCONDUCTORS (HTS)

讨论了高温超导临界态模型（Ｂｅａｎ模型）中的自场效应．通过计算和分析，得到了临界电流密度的测量值Ｊｃｅｘｐ（Ｂａ）．发现Ｊｃｅｘｐ（Ｂａ）与其真实值Ｊｃ（Ｂａ）之间在低外场时存在着较大的差异，从而解释了实验中发现的利用临界态模型测量高温超导体临界电流密度的值比直接测量值要小的现象．并提出了一种对实验测量值Ｊｃｅｘｐ（Ｂａ）进行修正的方法．

In this paper, the self field effects of the Bean's critical state model are discussed. The applied field dependence of critical current density J cexp (B a ) measured by Bean's critical model was calculated and discussed. We found that J cexp (B a )is much different from its actual value J c (B a ), especially when the applied field B a is lower than the deviated magnetic field Δ(B a ). So, the phenomena that the critical current density measured by the Bean's critical state model is smaller than that measured by the transport methods are explained. Furthermore, a method to correct the experimental value J cexp (B a )was proposed.