The effect of non-superconducting defects on microwave breakdown of HTSC films

Microwave breakdown of an HTSC film caused by the film overheating in the vicinity of non-superconducting defects is studied theoretically. It is shown that microwave breakdown may be preceded by the nucleation of the normal phase domain localized at the defect. The influence of the defect geometry and conductivity on the microwave breakdown development and on the breakdown magnetic field is investigated. Analytical expressions for are found in the cases of circular and linear defects. The breakdown field at a linear defect is shown to be several times lower than the one at a circular defect. The results obtained may be of importance in the study of power handling capability of HTSC films.