Performance of Nd-Fe-B and ferrite magnets in superconducting linear bearings with bulk YBCO

The performance of two different magnets has been tested in linear bearings with YBCO bulk superconductors, prepared by seeded melt texturing technique. Two different rails have been assembled with opposite magnetic polarization and intercalation of ferromagnetic flux concentrators. One rail has been mounted with Nd-Fe-B magnets and the other one, with Ferrite magnets. The levitation force of the Nd-Fe-B permanent magnets rail is more than one order of magnitude larger than that one of Ferrite. The stiffness of the linear bearing and the vibration damping were measured in the field cooling procedure for several cooling heights from the rail. The different cooling heights result in different gaps between the YBCO blocks and the magnets, for the same load. The stiffness increases with the decrease of gap, for the same load, in both cases, but is higher in the Nd-Fe-B rail. The vibration damping is rather low in both systems (similar to 0.01). We conclude that the Nd-Fe-B magnets are the most suitable for applications on linear levitating bearings.