High power plasma filled backward wave oscillators

Relativistic backward wave oscillators (BWOs) have proven to be relatively efficient, high-power microwave sources in the centimeter wavelength range. Recent Soviet results have indicated that the use of a background plasma in such a device can serve to increase the space charge limiting current and allow operation of the BWO at higher injected beam current levels, with accompanying higher microwave power outputs. Studies currently being initiated at the University of Maryland include studies of BWO performance with fill plasmas produced by both electron beam ionization of a low pressure neutral gas background and by an independently controllable plasma source used to inject plasma directly into the BWO structure. Results of the first configuration will be reported and compared with theoretical expectations.