Measurements and modeling of HTS shielded dielectric resonators

We have performed accurate, reproducible and nondestructive measurements of the surface resistance of high quality YBa2Cu3O7-x (YBCO) thin films in th e temperature range 12 K to T-c using a compact rutile dielectric resonator method at 9.6 GI Iz. The absolute values of the Ts surface resistance have been measured to systematic errors of less than 10 mu Omega at this freque ncy using this technique, which employ two resonator configurations with ca refully chosen geometries. The resonators hale unloaded Q factors of around 10(5) at 77 K, increasing to above 5.10(5) below 15 K. We have used three dimensional electromagnetic software ("Superfish") to st udy the effects of the copper shield on these rutile (TiO2) measurements, a nd others using lanthanum aluminate (LaAlO3) as the dielectric material. In the latter case, there are significant uncertainties (as large as 100%) in the measurements of the surface resistance of the YBCO films owing to the smaller field energy filling factor for LaAlO3, since it has a lon er relat ive permittivity than rutile.