EXCITATION OF ELECTROMAGNETIC-WAVES IN A PLASMA-FILLED BACKWARD-WAVE OSCILLATOR IN THE KU REGION

The effect of plasma on backward wave oscillator (BWO) emission in a 1 2-18 GHz frequency range is given. It is shown that the Ku band emissi on corresponds to the cylindrically symmetric transverse magnetic TM01 and not the higher mode. Due to the slowing down of waves with the in crease in plasma density there occurs a BWO mode switching, i.e., BWO switches from a bounded mode to an unbounded one. Here the analysis fo r the switched BWO in the unbounded mode is given. The expressions for the temporal and spatial growth rates in the presence of plasma are o btained. The efficiency calculations are also given. Comparison of the results with that of a previous experiment [IEEE Trans. Plasma Sci. 1 8, 497 (1990)] has been carried out. (C) 1998 American Institute of Ph ysics. [S1070-664X(98)01106-9]