Superconducting lead cavities at 35 GHz

An investigation of machined superconducting lead cavities operating in the circular cylindrical TE011mode at 34.8 GHz is reported. Measured values of the surface resistance and the shift of the resonance frequency are presented and compared with calculated values. Construction criteria for high-Q cavities are proposed, based on a discussion of the different loss mechanisms in a cavity. According to these criteria 10 cavities were processed and investigated by Q measurements. The surfaces were examined by microscope. A new untraditional method for examining machined surfaces was applied. Recognizing that a surface with surface defects has both inferior electrical properties and decreased mechanical strength compared with a perfect surface, different surfaces were treated in ultrasonic baths in order to examine the mechanical strength. The degree of destruction of the surfaces was compared with the Q values of cavities with surfaces constructed in the same way.