How to determine critical current density in YBCO tapes from voltage–current measurements at low magnetic fields
How to determine critical current density in YBCO tapes from voltage–current measurements at low magnetic fields
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DOI：
10.1088/0953-2048/20/12/002
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发表时间：
2007-12
影响因子：
3.6
通讯作者：
L. Rostila;J. Lehtonen;R. Mikkonen;J. Šouc;E. Seiler;T. Melíšek;M. Vojenčiak
中科院分区：
文献类型：
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作者：
L. Rostila;J. Lehtonen;R. Mikkonen;J. Šouc;E. Seiler;T. Melíšek;M. Vojenčiak
本文介绍了一种确定本征临界电流密度 Jc(B) 与磁场相关性的优化方法。首先，在各种外部磁场中测量临界电流。然后搜索最适合测量的 Jc(B) 依赖性。在这些计算中，考虑了样品的自场，因此可以利用在低于 0.1 T 的低外部磁场中进行的测量。这里，YBCO 材料的 Jc(B) 依赖性由 Kim 模型描述，该模型经过修改也包含各向异性。因此，需要搜索四个参数：零场临界电流密度 Jc0、参考场 B0、Kim 模型指数 α 和各向异性比例因子 γ。搜索这些参数在计算上具有挑战性，但计算时间仍然令人满意。作为示例，我们发现了来自不同制造商的两个 YBCO 样品的 Jc(B) 依赖性。对于这两个样本，除 B0 之外的所有参数都彼此接近。例如，两个样品的 Jc0 值约为 0.9 × 1010 A m−2。
In this paper, an optimization method to determine the magnetic field dependence of the intrinsic critical current density, Jc(B), is introduced. First of all the critical current is measured in various external magnetic fields. Then the Jc(B)-dependence that fits optimally to the measurements is searched for. In these computations the self-field of the sample is taken into account and thereby measurements performed in low external magnetic fields, below 0.1 T, can be exploited. Here the Jc(B)-dependence of YBCO material is described by the Kim model, which is modified to include the anisotropy also. Thus, there are four parameters to search for: zero field critical current density Jc0, reference field B0, Kim model exponent α and anisotropy scaling factor γ. The search for these parameters was computationally challenging but computation times were still satisfactory. As examples, the Jc(B)-dependences of two YBCO samples from different manufacturers were found. For both samples, all parameters except B0 were near each other. For example, Jc0 values for both samples were about 0.9 × 1010 A m−2.