Microwave generation from a VIRCATOR with a slow wave structure

Summary form only given. The generation of high-power microwave (HPM) pulses from a VIRCATOR that has a slow-wave structure in the drift region downstream of the foil anode is discussed. The goals of this work are to demonstrate frequency-stabilized performance without the use of resonant cavities and to increase efficiency in the conversion of electron beam energy into HPM. The drift region is occupied by a slow-wave structure similar to that found in a backward-wave oscillator. An intense relativistic electron beam is introduced into the drift region, causing a virtual cathode to form. The slow-wave structure provides a feedback on the virtual cathode's frequency of oscillation via space charge cloud electromagnetic fields. Simulations indicate that the slow-wave structure can tune the frequency of operation quite well, but does little to improve the conversion efficiency. The authors have tested two structures in the laboratory and found reasonably good agreement with the simulation. The devices operate at about 1.8 GHz and appear to have a 5-10% bandwidth. The device appears to run predominantly in the TM/sub 01/ mode.