Va. Balakirev et al., PARAMETRIC-EXCITATION OF ELECTROMAGNETIC-RADIATION BY AN ELECTRON-BEAM IN A STRATIFIED PLASMA WAVE-GUIDE, Plasma physics reports, 24(8), 1998, pp. 684-690
The excitation of electromagnetic radiation by an electron beam in pla
sma waveguides in which the plasma density varies periodically along t
he device is examined. In the scheme in question, a plasma wave synchr
onized with a beam is parametrically coupled with a fast electromagnet
ic wave due to periodic variations in the plasma density. This fast wa
ve propagates in a vacuum gap between the plasma boundary and the cond
ucting shell. It is shown that, in such a system, parametric conversio
n of the plasma wave into electromagnetic radiation increases the tota
l efficiency of the beam-power conversion. An important point is that
the mechanism for transformation of slow plasma waves makes it possibl
e to not only solve the problem of extracting microwave power from the
plasma but also substantially increase the total efficiency of the be
am-power conversion.