Influence of semi-spherical shallow pits on levitation force of HTS bulks in applied magnetic field

Abstract High-temperature superconducting (HTS) maglev has the advantages of self-stabilizing, energy-saving, and environmental protection, and illustrates good development prospects in fields such as rail transportation, superconducting bearings, and superconducting motors. The paper finds a new method of increasing the effective interaction area between the bulk and the magnetic field through mechanically processing semi-spherical shallow pits. This method enhances the current density on the projection surface, strengthening the interaction between the magnetic field and the surface current. As a result, the levitation force of HTS bulks is ultimately improved. In this paper, experiments using three different bulks confirmed that pits can effectively enhance the levitation force. Furthermore, by studying the effects of semi-spherical shallow pits at different positions and depths on the levitation force, we have identified the optimal processing scheme to increase the levitation force. This scheme increased the levitation force by 14.8% to the most. On the other hand, addressing the difficulties in simulating bulk with microscale pits, an improved E–J relationship model is established. This calculation uses virtual bodies to simulate the current gain effect of the pits, enabling fast and accurate calculations. This work not only explores the effects of pits on the levitation force and current of bulk materials but also provides an effective method for further improving the carrying capacity of practical superconducting magnetic levitation and system design.