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Guidance Performance of YBCO Bulks Under a Low-Pressure Environment

High temperature superconducting (HTS) maglev train running in the evacuated tube is a new kind of transportation with great potential, and its guidance performance is crucial to the ability of passing through curves. Therefore, it is necessary to study the guidance force of the bulks YBCO under a low-pressure environment. Based on the test platform of magnetic levitation characteristics under a low-pressure environment, the liquid nitrogen super-cooling state is realized by the method of evacuation and depressurization. The guidance force of YBCO superconductor in the lateral displacement above a Halbach permanent magnetic guideway (PMG) was measured under different pressure values (100 kPa, 60 kPa, 40 kPa, 20 kPa). Results show that decreasing pressure improved the guidance performance of YBCO bulks. Compared with the maximum guidance force and its hysteresis under 100 kPa, there are about 23.1% increase for guidance force and 40% decrease for hysteresis under 20 kPa. So, the lateral stability of the HTS maglev system has been enhanced during the evacuation process. The experimental results provide basic references for the research on the evacuated tube transportation (ETT) HTS maglev system.