Observation of RF superconductivity in Y1Ba2Cu3O9−δ AT 3 GHz

Abstract Two samples of Y 1 Ba 2 Cu 3 O 9−δ , one fabricated at Los Alamos National Laboratory and the other at the University of Wuppertal, were tested in the rf field of a niobium cavity at 3 GHz and in a temperature range from 4.2 to 300 K. The data show a sharp reduction of the Joule losses in the samples beginning at an onset temperature of 98 and 92 K, respectively. The residual losses of the sample were measured at 4.2 K where the host cavity was superconducting. The ratio of these losses to the ones observed slightly above T c was less than 1.1 × 10 −2 . This indicates that only a small fraction of the conduction electrons of the Y 1 Ba 2 Cu 3 O 9-δ sample remain unpaired. The dependence of the rf losses on the rf magnetic field allows the determination of a maximum surface current density which is found to be about 5 × 10 4 A/cm 2 .