II型超导圆柱形导线临界电流下的磁通切割和磁通输运理论
Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire
摘要：
我介绍了一个临界状态理论，结合磁通切割和磁通运输计算磁场和电流密度分布内的第二类超导圆筒在其临界电流在纵向施加磁场。该理论是罗梅罗-萨拉查和佩雷斯-罗德里格斯提出的椭圆临界状态模型的扩展。旋涡动力学详细地取决于磁通切割（ρ_ \parallel）和磁通流动（ρ_ \perp）的两个非线性有效折射率及其比值r = ρ_ \parallel /ρ_ \perp。当r < 1时，磁通切割在降低内部磁通密度的幅度方面的低相对效率导致顺磁性纵向磁矩。作为一个模型，了解实验观察到的磁通切割和脱钉的临界电流之间的相互关系，我计算的螺旋涡弧拉伸两个钉扎中心之间的力时，涡受到电流密度的任意角度θ。在临界电流密度J_c（θ）处，磁通切割和磁通输运同时发生，使涡流电弧不稳定。
英文摘要：
I introduce a critical-state theory incorporating both flux cutting and flux transport to calculate the magnetic-field and current-density distributions inside a type-II superconducting cylinder at its critical current in a longitudinal applied magnetic field. The theory is an extension of the elliptic critical-state model introduced by Romero-Salazar and Perez-Rodriguez. The vortex dynamics depend in detail upon two nonlinear effective resistivities for flux cutting (ρ_\parallel) and flux flow (ρ_\perp), and their ratio r = ρ_\parallel/ρ_\perp. When r < 1, the low relative efficiency of flux cutting in reducing the magnitude of the internal magnetic-flux density leads to a paramagnetic longitudinal magnetic moment. As a model for understanding the experimentally observed interrelationship between the critical currents for flux cutting and depinning, I calculate the forces on a helical vortex arc stretched between two pinning centers when the vortex is subjected to a current density of arbitrary angle ϕ. Simultaneous initiation of flux cutting and flux transport occurs at the critical current density J_c(ϕ) that makes the vortex arc unstable.
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