DC FEATURES AND RF LOSSES OF NB-BASED SUPERCONDUCTING THIN-FILMS

We have realized superconducting thin films of Nb, NbN, and NbZr, in view of their application to the superconducting accelerating cavities. The samples have been sputtered on different planar substrates, i.e. glass, sapphire, and Copper. The electrical and superconducting features of the films have been measured in the temperature range of 300 K divided-by 4.2 K and in the presence of a magnetic field up to 5 T. The expected RF properties are discussed. Measurements of the RF dissipation of Nb75Zr25 films sputtered on Copper substrates have been performed in a cylindrical TE011 cavity.