Self-field effects upon the critical current density of flat superconducting strips
Self-field effects upon the critical current density of flat superconducting strips
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DOI：
10.1088/0953-2048/18/6/016
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发表时间：
2005-06-01
影响因子：
3.6
通讯作者：
Clem, JR
中科院分区：
文献类型：
--
作者：
Brojeny, AAB;Clem, JR
本文建立了一个自洽的一般理论，当体钉扎由依赖于场的脱钉临界电流密度J（p）（B）表征时，自洽地解释了自场效应对混合态下平板II型超导带材的平均输运临界电流密度J（c）的影响，其中B是局部磁通密度。我们首先考虑散装和边缘钉扎贡献的可能性，但得出结论，散装钉扎占主导地位的几何边缘势垒效应在国家的最先进的YBCO薄膜和原型第二代涂层导体。我们使用Kim模型J（pK）（B）= J（pK）（0）/（1 +竖线B竖线/B-0）来应用我们的理论作为示例。我们计算J（c）（B-a）作为垂直施加的磁感应强度B-a的函数，并显示J（c）（B-a）如何与J（pK）（B）相关。我们发现，当B-a >= B*（a）时，J（c）（B-a）非常接近等于J（pK）（B-a），其中B-a（*）是使带材边缘净通量密度为零的B-a值。然而，当B-a < B-a（*）时，Jc（Ba）相对于J（pK）（B-a）在低场中被抑制，当B-a（*）/B-0为1阶或更大时发生最大抑制。
We develop a general theory to account self-consistently for self-field effects upon the average transport critical current density J(c) of a flat type-II superconducting strip in the mixed state when the bulk pinning is characterized by a field-dependent depinning critical current density J(p)(B), where B is the local magnetic flux density. We first consider the possibility of both bulk and edge-pinning contributions but conclude that bulk pinning dominates over geometrical edge-barrier effects in state-of-the-art YBCO films and prototype second-generation coated conductors. We apply our theory using the Kim model, J(pK) (B) = J(pK)(0)/(1 + vertical bar B vertical bar /B-0), as an example. We calculate J(c)(B-a) as a function of a perpendicular applied magnetic induction B-a and show how J(c)(B-a) is related to J(pK)(B). We find that J(c)(B-a) is very nearly equal to J(pK)(B-a) when B-a >= B*(a), where B-a(*) is the value of B-a that makes the net flux density zero at the strip's edge. However, Jc(Ba) is suppressed relative to J(pK)(B-a) at low fields when B-a < B-a(*), with the largest suppression occurring when B-a(*)/B-0 is of order unity or larger.