Current transfer length revisited

Abstract

We constructed a model to estimate analytically the current transfer from a matrix to asuperconducting region through a highly resistive barrier layer. Also, a numerical modelwas formulated in order to study the current transfer when the superconducting region hasnonlinear resistivity. Because so far the definition for current transfer length (CTL) hasnot been well established we propose a definition which introduces a method todetermine the CTL corresponding to a chosen criterion. Two possible criteria aresuggested. One relates to electric field and the other to current in the superconductingregion. As a consequence this paper gives an analytical formula which can beused for example in a short-specimen measurement to determine the disposablemeasurement area. As examples, the different CTL criteria were computed with differentresistivities in the superconductor. Also, analytical and numerical models werecompared. The analysis was carried out for the possible general structure of futureMgB2 conductors: superconductor, barrier layer and matrix metal. According to theresults, the presented analytical model is a useful tool in determining thecurrent transfer length when the barrier layer contact resistance is at least25 µΩ mm2. Otherwise the presented numerical model must be used.