MAGNETIC-FLUX DYNAMICS AND IMPEDANCE IN A SUPERCONDUCTING YBA2CU3OX CERAMIC TUBE

The external surface impedance of a ceramic tube made of high temperature metal oxide YBa2CU3Ox superconductor has been measured in a magnetic field at a frequency of 500 MHz. The screening behaviour of the tube, i.e. the external magnetic field dependence of the magnetic field in the inner space of the tube, has been investigated. The results show the material to behave as a hard type-II superconductor. The impedance contains a contribution governed by the magnetic flux passing through the surface. The contribution depends on the distance from the surface to the boundary of the critical state region in the material.