Reflection and transmission measurements on high-Tc superconducting films in the MM-wave region

The characterization of high-Tc superconducting films is in progress at the Frascati FEL Facility, F-CUBE. The experiment is aimed at obtaining the complex conductivity of YBCO films deposited on a LaAlO3 substrate by measuring the reflection and transmission coefficients. Similar experiments have been performed by other groups at far infrared wavelengths. The continues tunability and the high peak power, up to 10 kW, of F-CUBE make this experiment possible also at millimeter wavelengths even in very lossy samples with transmission of less than 1%. Such an experiment is important for the study of high-Tc superconductors, because it provides additional spectral information and a better comprehension of the internal structure of these materials. The experimental technique utilized will be discussed together with the issues related to the detection process and to the stability of the FEL source. Results in the spectral range between 2 and 3.5 mm will be presented and compared with the characteristics at shorter wavelengths