A study on levitation force and its time relaxation behavior for a bulk superconductor-magnet system

We have studied the levitation force of a Gd–Ba–Cu–O bulk superconductor 60 mm in diameter and 20 mm in thickness with a newly developed superconducting magnet system that can provide high field gradient. The magnet system was composed of two superconducting coils that are co-axially placed, and currents are passed in the opposite direction. To study the effect of radial and vertical magnetic field components on the levitation force and its time relaxation, the superconductor was placed at several locations. It was confirmed that the levitation force is strongly dependent on the radial component of magnetic fields. It was also found that the time relaxation was reduced without sacrificing the levitation force by increasing the radial component of the external field.