Experimental studies of overmoded high power microwave generators

Summary form only given. Experiments with overmoded (Dspl lambda/ /spl sim/3) high-power microwave generators have been performed. Two classes of devices were investigated: (1) single-stage backward wave oscillators (BWOs) with varying electrodynamic structure lengths; and (2) multiwave Cerenkov generators (MWCGs), consisting of two stages of seven sinusoidal periods each, connected by a variable length drift section. Both types of devices were driven by large-diameter, magnetized, annular, intense relativistic electron beams (250-900 keV, 2.5-9 kA). High-power microwave radiation in the 5.5 to 6 GHz frequency range was generated with both types of structures. A maximum radiated power of 320 MW was obtained with an overmoded BWO structure, and a maximum power of 102 MW was obtained with an MWCG. Start oscillation currents in the range of 204 kA were observed for both classes of devices.