An experimental investigation of axial cylindrical surface waves supported by capacitive surfaces

This paper records experimental work designed to investigate the use of a guide with a capacitive surface impedance for the support of an axial cylindrical surface wave. Previously only inductive surfaces had been employed for the purpose. A solid dielectric rod, made of Perspex, was used as the guide, and its diameter was carefully adjusted to make the surface impedance come within the particular range of interest. The experiments show that there is no doubt at all about the physical reality of an axial cylindrical surface wave supported by a capacitive surface and having a phase velocity exceeding that of light. Moreover, it has been established that, within the limits of experimental error, such waves vanish completely when the threshold condition necessary for their support in the capacitive region is approached, exactly as predicted by theory.