Influence of thinned (RE)BCO conductors on the properties of stacked tapes

Superconducting magnetic bearings are based on self-stabilizing, non-contact levitation of a bulk superconductor over a magnet system. Using tape stacks, the performance of magnetic bearings can be improved. Here the engineering critical current density plays a decisive role, which is essentially determined by the thickness of the coated conductors and can be significantly improved by thinning the substrate of the tapes.
In order to determine the dependence of the levitation force on the tape thickness and thus the distance between the successive (RE)BCO layers, tapes from SuperPower and Theva were thinned from the substrate side by electropolishing. We developed an electropolishing process that generates a sufficiently high removal rate without having too great edge effect so that a uniform removal takes place in large parts of the sample. V-I measurements were performed to check whether the superconducting properties are influenced by the chemical and electrochemical processes. Additionally, levitation force measurements were performed to show the influence of the tape thickness on the performance of magnetic bearings.