High-power capabilities of beam-plasma amplification

Using the beam-plasma interaction for microwave amplification to high powers results in a significant reduction in beam power density over that required in conventional amplifiers. This, and other advantages of the interaction are discussed and some of the possible limitations pointed out. A brief introduction presenting a physical description of the basis of the beam-plasma interaction is given along with the results of a large-signal analysis using a disk model for the electron beam. These results indicate that ratios of fundamental RF current to dc beam current of greater than 1.5 can be obtained with a velocity spread of less than ± 20%. This predicts efficiencies of greater than 60% if an optimum output coupler is used. In order to achieve these efficiencies without sacrificing the advantages of the interaction, tight coupling directly to the RF fields in the plasma must be achieved. Possible coupling methods are discussed along with experimental data showing the degree to which coupling has been achieved.