HARMONIC GENERATION IN NONLINEAR BEAM-PLASMA SYSTEMS.
MICHIGAN UNIV ANN ARBOR ELECTRON PHYSICS LAB
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Nonlinear operation and the saturation characteristics of beam-plasma devices were investigated both theoretically and experimentally. The gain, power output, efficiency and the magnitude of the higher harmonic components that pertain to such devices are of particular interest. The geometry analyzed consists of a cylindrical plasma column, treated in a linear fashion, which serves as a slow-wave circuit along which electromagnetic energy can propagate. A cylindrical electron stream, treated in a nonlinear fashion, is assumed to be concentric with the plasma column. RF amplification takes place when a fraction of the kinetic energy of the stream electrons is converted into RF wave energy. One- as well as two-dimensional stream models are used to calculate the RF currents and circuit voltages of the fundamental signal and its harmonics by use of a digital computer. An experimental test vehicle was used to correlate the theoretically calculated results with those obtained from an actual beam-plasma interaction. A xenon plasma column 10.5 cm long yields electronic gain as high as 35 dB in the vicinity of 2 GHz. Harmonic components through the fifth are observed with the second harmonic being only 5 dB below the fundamental under certain conditions. Two methods of coupling RF energy to the device are employed. The quasi-optical technique making use of elliptic cavity couplers reduces the coupling losses significantly compared to previously used coupling schemes. Author
- Electrical and Electronic Equipment
- Plasma Physics and Magnetohydrodynamics