Magnetic shielding performances of YBCO superconductors : applications to multiple bulks and thin films
Résumé
HTS bulks present a high critical current density which can either be used as strong magnets or perfect magnetic shields. Previous works showed that BSCCO bulks can screen magnetic fields up to 0.1 T. For large scale applications like electrical machines, stronger magnetic field is usually needed. In so doing, (RE)BCO materials are more suitable since they can shield much higher magnetic fields (typically around 0.5T at 77 K). Another key issue concerns the size of the bulks. Nowadays, it is possible to manufacture 150-mm diameter class cylindrical YBCO bulk. In order to get larger magnetic shielding areas, multiple bulk superconductors should be arrayed and stacked in layers. Thin films can also be deposited to get very large screening areas. The paper presents experimental results on screening performances of layered YBCO pellets as well as thin films. The experiments are carried out at 77 K under external magnetic fields of 150 mT. Different topologies are considered as follows: - Single layer configuration with 9 square pellets, - Double layer configuration with respectively 9 and 4 square pellets, - One layer of YBCO thin film. It is shown that the double layer configuration improves the shielding performances. Other results and discussions will be given in the full presentation.