Fyzikální ústav Akademie věd ČR

Nucleation of the superconducting phase in a thin surface sheath in a decreasing magnetic field parallel to the sample surface was predicted by Saint-James and de Gennes fifty years ago. This prediction was confirmed in a short time after the paper’s publication. Nevertheless, the model for the ac losses in bulk samples in magnetic fields above H_c2 are still absent. Experiments with thin-walled superconducting cylinders can provide an essential simplification of this problem. Thin-walled hollow cylinders with macroscopic diameter have some advantages in research.