Investigation of HTS Tape Stacks for Levitation Applications

Abstract

Currently, high-temperature superconductor (HTS) bearings are most commonly designed with bulk REBa ₂ Cu ₃ O _7-x (REBCO), but these HTS bulks have several drawbacks, such as brittleness and the complexity of sample preparation. An alternative for levitation systems is to use stacks of REBCO coated conductors (HTS tapes). The main advantages of HTS tapes are the simplicity of manufacturing elements in the required shape and high strength stability. For the development of HTS bearings, it is important to characterize both the levitation force along the axis connecting the magnet and the superconductor, and the stability of the system in response to lateral displacement. In this paper, we present new results of measurements of the levitation force between a permanent magnet and a stack of HTS tapes containing from 10 to 100 tapes of 12 mm × 12 mm. Measurements were conducted in zero-field cooling mode. We observed hysteresis of the levitation force in the case of lateral displacement. In addition, we have investigated the decay in the levitation force due to lateral displacement with each cycle of movement. It is shown that the decay rate tends to be constant on increasing the number of tapes in the stack.