The Definition of the Paramethers of Superconducting Film for Production of Protection Equipment Against Electromagnetic Environmental Effects

The paper presents the results of evaluating the propagation of a plane electromagnetic wave (EMW) over the surface of a film made of a high-temperature superconductor (HTS) in both superconducting S and normal N states, as well as an analysis of the parameters of a thin HTS film necessary for implementing a device for protection against electromagnetic radiation. Evaluation of the propagation of EMW over the surface of a thin HTS film was performed on the basis of a two-fluid model. As a result of the research, relations were obtained for determining the value of the surface impedance and the depth of penetration of EMW into a superconducting film in S and N states. It is shown that the expression for determining the penetration depth of EMW into a superconducting film in the normal N state is applicable provided that the frequency of the signal field does not exceed the critical value, which is determined by the binding energy of charge carriers at a temperature not exceeding the transition temperature to the superconducting state. Based on the relations for determining the surface impedance of a thin HTS film, relations are obtained for the active surface resistance, which is the real part of the surface impedance, and the surface reactance, which is its imaginary part, in the superconducting and normal states. Using these ratios, the quality parameter of the HTS thin film is introduced. The dependence of the quality factor of the HTS film on its thickness is found. It is shown that the highest value of the quality factor is realized when the film thickness is less than or of the order of the penetration depth. It is noted that this dependence is valid only if the film thickness does not depend on its quality. Keywords — superconducting film, electromagnetic wave, two-fluid model, surface impedance, penetration depth.