RESONANT ENHANCEMENT OF RADIATION FROM A BACKWARD-WAVE OSCILLATOR UTILIZING LARGE-DIAMETER CORRUGATED METAL STRUCTURE

An experiment on a backward wave oscillator (BWO) utilizing a large di ameter corrugated metal wall slow wave structure (SWS) has been presen ted. Measurements are made above and below the starting beam energy fo r conventional BWO operation. For the latter case, an excited noise-le vel backward wave at 20 GHz (TM(01) mode) is coupled at the ends of th e SWS to a forward anomalous Doppler shifted electron cyclotron (EC) b eam mode which amplifies the original oscillation by an amount of 50 d B. Resultant microwave output powers of 200 kW with 4.5% electronic ef ficiency are observed near the condition of resonant magnetic field fo r an electron beam with energy 35 keV. Unlike the well-known fast wave devices, our slow wave EC device is simple to operate utilizing an el ectron beam with dominant parallel velocity in a uniform magnetic fiel d.