Novel truncated cone cavity for surface resistance measurements of high T/sub c/ superconducting thin films

A truncated cone cavity that avoids degeneration between the TE/sub 01n/ and TM/sub 11n/ modes occurring in the most frequently used circular cylindrical cavities for materials measurements is described. Analytical expressions for the field components are given. An error analysis is carried out which yields a sensitivity of 2.3 m Omega for surface resistance measurements at 18 GHz, using samples with a diameter of 9 mm. One cavity was built, and measurement results are given for the surface resistance of various YBa/sub 2/Cu/sub 3/O/sub x/ thin films on MgO substrates. The samples were manufactured by means of laser ablation and magnetron sputtering. >