Measurement and Simulation of the Magnetic Levitation Characteristics of Passive No-Insulation Coils

The use of no-insulation coils in high-temperature superconductor levitation bearings has the potential to produce bulk-like characteristics without the associated size, quality and mechanical limitations of bulk material. Here we performed levitation force measurements on passive (open-circuit) dry wound and solder-impregnated REBCO no-insulation coils to investigate the effect of varying turn-to-turn resistivity. Finite element simulations employing a rotated anisotropic resistivity tensor successfully reproduced the observed behaviour, validating this approach. Low turn-to-turn resistivity facilitates the circulation of a net azimuthal current, which enhances levitation force but decays with time due to resistive dissipation. This work lays the groundwork for future research on active (powered) coils to fully realise the potential of no-insulation coils in superconducting bearings.