Current and voltage distribution in composite superconductors with resistive barriers - symmetric case

An equivalent symmetric scheme with distributed parameters is proposed, aiming to simulate the current and voltage distribution in composite high-T_c superconductors with thin resistive barriers around the filaments. There are three longitudinal parallel branches in the scheme representing the superconducting core, the metallic inner matrix around this core and the outer metallic matrix. Transversal current flow is controlled by two interlayer elements: one represents the barrier inserted between the outer and inner matrices, while the second simulates the interface resistance between inner matrix and the superconducting core. The superconducting core may be fully resistanceless, but it can be found eventually in the resistive state.

Two cases are discussed: first, the transport current is supplied into the composite conductor through the outer matrix and, second, the transport current flowing fully in the superconducting core is forced to leave it due to some distortion of superconductivity.

The governing relation in the scheme is the product of the matrix-superconductor interface conductance and the inner matrix resistance per unit length. Solution of the scheme leads to results that depend on the following dimensionless relations: the ratio of the barrier to the matrix-superconductor interface conductances per unit length, the ratio of the outer to the inner matrix resistances per unit length and the ratio of the eventually resistive core resistance to the inner matrix resistance per unit length.

The analytical results offer the possibility to calculate the longitudinal voltage distribution on the outer matrix surface and by this means to follow the current distribution in the conductor cross section. They also allow one to calculate the typical current transfer lengths between the elements.