Smith-Purcell Radiation Based on Cylindrical Surface Waves

Smith-Purcell (SP) radiations based on cylindrical surface wave are examined. Cylindrical surface waves are formed on metal cylinders having a periodically corrugated wall. Corrugation parameters are those used in K-band backward wave oscillators (BWOs). The corrugated metal cylinders are excited by an axially injected coaxial annular beam in a weakly relativistic region less than 100 kV. Cylindrical surface wave excitations due to BWO are observed at about 23 GHz. In addition, SP radiations are observed in the higher frequency regions up to about 90-100 GHz, which is about 4 times higher than the frequency of cylindrical surface wave.